2017 Renewable Energy Handbook Wind

December 2016 windpowerengineering.com

The technical resource for wind profitability

2017 Renewable Energy

HANDBOOK

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NEVER HAVE I BEEN as excited to welcome you to the pages of our handbook and to our celebration of renewable energy as this year. It’s a great time to be in wind and solar, whether you’re an industry vet or a newcomer in 2017.

I say this with confidence, in spite of concern you’ve likely heard that renewable development won’t prosper—and may even come to a halt—under the new U.S. presidency. For every commentary I’ve seen igniting panic over possible solar and wind policy repeals, I’ve read another instilling faith in the strength of both markets and their bipartisan support.

Having heard out both opinions, I tend to side with the latter. True, the new administration could slash renewable energy tax credits, revoke programs and ignore recommendations, guidance and goals of the previous office. This would certainly hurt the pace of renewable development but definitely not destroy it. Perhaps eight years ago the absence of a federal focus on renewables could have devastated wind and solar energy growth. But if it happens today, these markets will survive—they’re now so established, they could take the hit.

While we still have education to do, renewables are no longer such a blue-versus-red issue. I remember former SEIA President Rhone Resch touting, “We’re not an issue, we’re an industry.” Based on the number of senators from both parties who support renewables, this idea is catching on. Studies, such as those from the Pew Research Center, confirm that most Republicans and Democrats favor expanding renewables. Yes, renewable development helps combat climate change, but politicians and citizen alike see that it also creates energy independence, additional electricity our increasing population demands and long-term jobs.

I could go on with facts and figures demonstrating the success of these markets, but my colleagues Michelle Froese, senior editor of Windpower Engineering & Development, and Kelly Pickerel, managing editor of Solar Power World, have already done so in their editorials. You can find them in the beginning pages of the following wind and solar sections, followed by articles that address many important components and other aspects of each market. We work diligently all year to provide answers to questions you may have on each topic, in hopes of enabling you to do better work, grow your business and create stronger industries.

I’d also like to direct you to a variety of previous print resources that are now available to you online. Databases for wind turbines, projects, solar panels, inverters, mounting systems and now batteries can be found on windpowerengineering.com and solarpowerworldonline.com.

We hope this makes your component selection easier. Our bimonthly print issues and weekly newsletters are also rich resources you can subscribe to for free.

We look forward to watching solar and wind energy grow in 2017 and dutifully remaining a MANAGING EDITOR resource to help you succeed, starting today.

Solar Power World kzipp@wtwhmedia.com Thank you for your continued readership.

ive never been so excited to welcome you to

renewables

KATHIE ZIPP

SPW WPE&D

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2017 RENEWABLE ENERGY HANDBOOK

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WINDPOWER ENGINEERING & DEVELOPMENT is also an independent forum for the expression of opinions relevant to industry issues. Letters to the editor and by-lined articles express the views of the author and not necessarily of the publisher or publication. Every effort is made to provide accurate information. However, the publisher assumes no responsibility for accuracy of submitted advertising and editorial information. Non-commissioned articles and news releases cannot be acknowledged. Unsolicited materials cannot be returned nor will this organization assume responsibility for their care.

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Welcome to the handbook....................................................................................................02

WINDPOWER

SOLARPOWER

Editor’s welcome to the wind section................ 09

Solar Basics........................................................ 62

Wind Basics....................................................... 10

Editor’s welcome to the solar section................ 66

Top wind stats.................................................... 12

U.S. Solar Irradiance map ................................. 67

U.S. Wind Speeds map .................................... 14

Top solar stats.................................................... 68

Components of a wind turbine.......................... 16

WIND ARTICLES

SOLAR ARTICLES

Silicon Modules .................................................. 70

Bearings............................................................... 18

Thin-Film Modules .............................................. 74

Bolting................................................................. 21

Power Optimizers ............................................... 76

Hydraulics ........................................................... 24

Microinverters ..................................................... 78

Cables.................................................................. 26

String Inverters ................................................... 82

Couplings............................................................ 28

Central Inverters ................................................. 90

Encoders.............................................................. 32

Flat Roof Racking & Mounting ............................ 92

Blade Composites .............................................. 34

Sloped Roof Racking & Mounting ...................... 95

Site Assessment .................................................. 36

Rail-less Mounts .................................................. 98

Construction, Installation, Development ............ 38

Grount Mounts ................................................. 102

Fall Protection ..................................................... 41

Carports ............................................................ 106

Operations & Maintinence ................................. 44

Trackers ............................................................. 108

Condition Monitoring ......................................... 47

Cables ............................................................... 112

Filters .................................................................. 51

Pyranometers .................................................... 116

Lubricants ........................................................... 53

Logistics .............................................................. 56

Software ............................................................ 121

Seals ................................................................... 58

Distribution ....................................................... 124

Ad Index ........................................................... 133

Batteries & Storage .......................................... 118 Site Assessment ................................................ 122

Operations & Maintinence ............................... 126

Construction, Installation, Development .......... 130

Safety ................................................................ 133

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2017 RENEWABLE ENERGY HANDBOOK

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WINDPOWER 09 10 12 16

Editor’s welcome to the wind section

Wind Basics

WIND ARTICLES Bearings............................................................... 18

Bolting................................................................. 21 Hydraulics ........................................................... 24 Cables.................................................................. 26

Top wind stats and resource map Components of a Wind Turbine

Couplings............................................................ 28 Encoders.............................................................. 32

Blade Composites .............................................. 34

Site Assessment .................................................. 36

Construction, Installation & Development ......... 38

Fall Protection ..................................................... 41

Operations & Maintinence ................................. 44

Condition Monitoring ......................................... 47

Filters .................................................................. 51 Lubricants ........................................................... 53 Logistics .............................................................. 56 Seals ................................................................... 58

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WINDPOWER

Farming the wind

WP

Dr. Sarah Mills, a researcher at the University of Michigan’s Gerald R. Ford School of Public Policy, recently took a deeper look at the impact of the wind industry on the rural community in a paper entitled, “Farming the wind: The impacts of wind energy on farming.” Responses to a survey of 14 farmland townships throughout Michigan came from over 1,200 landowners. Key findings include: • Farmers with turbines on their land have invested twice as much in their operations over the last five years as those without them.

• Turbine-hosting farmers have purchased more farmland in the last five years than non-hosts.

• Farmers with turbines are more likely to believe their property will be farmed in the future, and they’re more likely to have a succession plan in place for when they retire.

• 92% of respondents think wind turbines provide income for landowners.

• 84% think wind farms create jobs.

Just as important, Mills also found that landowners with wind turbines spent significantly more improving their homes and farms.

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a great time to invest in

WIND POWER THE SAYING GOES that good things come in threes, and the wind

industry has certainly delivered on a trio of positives this past year.

For one, the industry started 2016 with a five-year extension of the Production Tax Credit (PTC), which provides wind developers with a credit (of $0.023/kWh at full value) for generated power.

After years of policy uncertainty, this good news meant the industry would begin 2016 with welcomed stability. As Tom Kiernan, CEO of the American Wind Energy Association (AWEA) pointed out at the time of the announcement: “Our industry will now get a break from the repeated boom-bust cycles that we’ve had to weather for two decades of uncertain tax policies.”

The performance-based PTC has helped drive down wind power’s costs by two-thirds in the past six years. For 2016, it has meant a nearrecord amount of wind farms are under construction or in advanced stages of development. As of the third quarter, more than 18,200 megawatts (MW) of wind capacity were under construction or in final development stages across 23 states. ”There’s never been a better time to buy American wind energy,” stated Kiernan in a related press release. And he was right. The multi-year PTC extension came with a phase down that encouraged developers and utilities to invest in wind early to receive the full value of the tax credits. As of the end of 2016, the 2.3 cents per kilowatthour credit is set to decrease to 80% of that value for projects that start construction in 2017, 60% in 2018, and 40% in 2019.

This brings us to our second good news item: U.S. windpower projects are growing in number and size. The industry is thinking big. Case in point: The 2,000-MW Wind XI Iowa project proposed by MidAmerican Energy.

“Wind XI puts Iowa on track to be the first state in the nation to generate more than 40% of its energy needs from wind power — far ahead of any other state,” said Iowa’s Governor Terry Branstad.

The project is slated for completion in 2019.

Although not quite as large, there were other big projects announced in 2016, including a proposed 600-MW Rush Creek project in Colorado

by Xcel Energy and a 500-MW Whispering Willow project expansion in Iowa by Alliant Energy. Even big

contracts are on the rise, such as the one New York’s Empire State Connector signed with wind developer Invenergy for 600 MW of wind power.

What’s more, corporations and mainstream companies are jumping on board and signing up for wind power (think Google, but also Walmart, IKEA, and Procter & Gamble). In fact, Procter & Gamble announced plans to meet its electricity demands with a long-term goal of using 100% wind energy, which means products such as Tide and Dawn will in future be manufactured by wind-generated power. According to AWEA, corporations and non-utility customers accounted for more than half of the wind capacity sold through power purchase agreements in 2015 — a trend that has continued in 2016.

The wind industry is also expanding its reach, which is our third positive to note. Onshore projects are growing in size and number, and at long last so are plans for offshore wind in the U.S. Much credit goes to Deepwater Wind for developing and commissioning America’s first offshore wind farm, the five-turbine, 30-MW Block Island project south of Rhode Island. The project has inspired interest and plans for an offshore market.

The Department of Energy has released a national strategy to facilitate the development of offshore wind energy in the country, which it maintains could help enable 86 GW of offshore wind in the U.S. by 2050. New York has created an offshore wind alliance with the goal of developing 5,000 MW of offshore wind power by 2030. And Massachusetts has put forth a bill that requires large utilities to buy up to 1,600 MW of offshore wind energy. This is the first legislation of its kind dedicated to offshore wind, and at a scale necessary to establish a viable market in the U.S. But the wind industry has more than three good things to report on. For instance, it is growing quickly and showing no signs of slowing down. Perhaps the best news is that now over 75,000 MW of installed wind-power capacity is on the grid, which means that wind is on track for meeting the Department of Energy’s Wind Vision. This report maintains that wind power could grow from supplying around 5% of U.S. electricity today to 10% by 2020, and 20% by 2030. With policy certainty now in place, it seems the wind industry is just getting started. WPE&D

MICHELLE FROESE SENIOR EDITOR

Windpower Engineering & Development mfroese@wtwhmedia.com

windpowerengineering.com

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WINDPOWER

WIND BASICS

WIND BASICS

By Emily Wild, Research assistant

What does the current wind market look like? important factor in estimating the potential power generation from a wind 2015 was a record-breaking year in the wind turbine in that area. The higher the wind speed, the easier and cheaper it is industry. For the first time, the wind market to capture the wind energy. To take advantage of areas with sufficient wind installed over 60 GW in a single year, according resources, utility-scale wind turbines are often built in large groups. to the Global Wind Energy Council (GWEC).

Wind turbines convert the kinetic energy of the wind into mechanical The European offshore sector set a yearly record power, which can be used for particular mechanical tasks or converted as well, with over 3 GW installed. Even despite into electricity through a generator. The three main parts of a typical China’s decelerating economy and lack of horizontal-axis wind turbine are the tower, blades or rotor, and nacelle. demand for wind power, that country installed The wind turns the rotor, which drive the gearbox located in the nacelle.

30.8 GW. Markets in Canada, Brazil, Mexico, The gearbox increases the speed of the blade rotation to spin a generator, and other countries also continue to develop. By which produces electricity in the form of alternating current. The turbine’s the end of the year, 26 countries had more than controller monitors the turbine operation and when wind speed exceeds 1,000 MW installed. According to the GWEC, about 55 mph, it halts the turbine’s operation to avoid damage. the global wind capacity is expected to nearly double in the next five years.

The U.S. also experienced an impressive year. According National Wind Technology Center in Boulder, Colorado. to the American Wind Energy Photo courtesy of Energy.gov.

Association (AWEA), by the end of 2015 the total number of operating utility-scale wind turbines was almost 48,800 with about 88,000 people employed across the industry’s various fields. U.S. wind industry continues to approach record levels today with well over 18,200 MW of wind capacity under construction. As Tom Kiernan, CEO of AWEA pointed out in a recent press statement: “There’s never been a better time to buy American wind energy.”

How does wind power work?

Wind energy, a form of solar energy, is produced by the sun’s uneven heating of the atmosphere and the earth’s surface. Wind-flow patterns vary depending on surrounding bodies of water, vegetation, and differences in terrain.

How fast and how often the wind blows in a certain area is known as its wind resource, an 10

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WINDPOWER

2017 RENEWABLE ENERGY HANDBOOK

What are some of the main advantages of wind power, and what are some of its challenges?

One of the biggest advantages of wind power is that it is produces power without pollution, unlike plants powered by fossil fuels. Wind power is also cost-effective, especially as installation prices continue downward as a result of more efficient technologies and industry experience. According to the U.S. Department of Energy, the average cost Expect to see more offshore of wind power is between wind farms in U.S. waters. four and six cents per kW hour, depending on the site’s wind resource and the project’s financing.

Because it is a form of solar energy, wind power is a highly sustainable energy source. Over the past 10 years, the total wind-power capacity in the U.S. has increased at an average of 30% per year, proving it to be a reliable domestic energy source.

Despite its overwhelming benefits, wind power can also present a few challenges. Even though it is a cost-effective energy resource, constructing a wind turbine requires a higher initial investment than a fossil fueled power plant. Another challenge is that while remote locations are often ideal for wind projects, they are far from large cities where electricity is needed. Transmission lines are then needed to transfer energy from wind farms to cities. In the past, wind turbines presented a hazard to local wildlife, especially birds. But through technological developments and improvements in site assessments, many of these issues have been resolved.

Why are offshore wind projects important to the growth of the wind industry?

The importance of offshore wind projects lies in its enormous potential. According to the GWEC, offshore wind has the potential to meet Europe’s energy demand seven times over, and the U.S. demand four times over. Areas of the U.S. where offshore wind could be especially beneficial are in coastal cities where there is a high demand for energy, but limited land-based renewable energy resources.

Offshore wind represents about 3% of global installed capacity. In 2015, 3,398 MW of offshore capacity was installed, bringing the global total to over 12,107 MW. About 11,028

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MW of this total is installed off the northern European coast, representing more than 91% of the world’s offshore wind power. Projects are in developmental stages throughout China, Japan, South Korea, Taiwan, and the U.S. A major benefit to building offshore is that the wind resource there is generally better than onshore. Offshore winds are typically stronger and fluctuate less than on land, resulting in greater energy production and from fewer turbines. Although costs for offshore wind development are relatively high, they are expected to decrease in the near future as the technology improves and the industry gains experience.

How does Congress’ extension of the Production Tax Credit affect the wind industry?

The wind industry stands to benefit greatly from the extension of the wind energy Production Tax Credit (PTC).

It has been extended for 2015 and 2016, and will continue at 80% of present value in 2017, 60% in 2018 and 40% in 2019, according to AWEA. Wind projects will be able to qualify as long as they start construction before the end date.

Industry leaders are hopeful for what the extension will bring, especially based on the results of the initial performance-based PTC. Since its integration in 2008, wind power in the U.S. has quadrupled, with costs decreasing by 66% within six years. The recent extension will help to continue these trends, allowing installers to build more projects at lower costs and create more jobs in the industry.

sources

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top wind stats

There’s a lot to consider when selecting a state in which to do wind business. Here’s an easy way to look at which states are excelling in the industry and in what ways.

Top five states in total wind capacity in 2015 Texas (17,713 MW) Iowa (6,212 MW) California (6,108 MW) Oklahoma (5,184 MW) Illinois (3,842 MW)

Top five states in total new wind capacity in 2015 Texas (3,615 MW) Oklahoma (1,402 MW) Kansas (799 MW) Iowa (524 MW) Colorado (399 MW)

Top five states according to percentage of wind generation Iowa (31.1%) South Dakota (25.5%) Kansas (23.9%) Oklahoma (18.4%) North Dakota (17.7%)

Percentage of new wind-generation capacity by region New Mexico (Over 10 MW) Texas (Over 10 MW) California (1.1 MW to 10 MW) Nebraska (1.1 MW to 10 MW)

CA

Utilities with wind-power capacity in 2014 (owned or under contract) Xcel Energy (Minnesota) (5,736 MW) Berkshire Hathaway Energy (Iowa) (4,992 MW) Southern California Edison (California) (3,531 MW) American Electric Power (Ohio) (2,185 MW) Pacific Gas & Electric (California) (2,060 MW)

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Sources: Information compiled from AWEA’s U.S. Wind Industry Annual Market Report 2015; the Department of Energy’s 2015 Wind Technologies Market Report; the 2015 Distributed Wind Market Report; and National Renewable Energy Laboratory (NREL).

windpowerengineering.com

12/16/16 8:42 AM

Provided by:

Wind jobs

Top five U.S. small wind-turbine manufacturers

The wind industry employed approximately 88,000 full-time workers in the U.S. at the end of 2015 — an increase of more than 15,000 from the end of 2014.

Northern Power Systems of Vermont Renewtech of Minnesota Ogin of Massachusetts Primus Wind Power of Colorado Bergey WindPower of Oklahoma

Texas (Over 24,000) Oklahoma (Over 7,000) Colorado (Over 6,000) Iowa (Over 6,000) Kansas (Over 5,000)

ND MN

VT

SD

NE IA CO KS

IL

OH

NM

OK

MA

TX windpowerengineering.com

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united states

Provided by:

WIND SPEEDS By placing project performance in the context of long-term average wind behavior, Vaisala’s maps

highlight the occurrence of specific quarterly wind anomalies which can significantly impact the financial health of an operational portfolio.

Quarterly U.S. Performance Maps, such as those produced by Vaisala, show departures from normal

wind speeds across the country and help wind operators reconcile recent project performance against actual wind conditions. Vaisala conducted the study by comparing 2016 data from its continually updated meteorological dataset with 30-year averaged conditions from the same dataset.

2016 U.S. WIND PERFORMANCE QUARTERS 1-3

Q1

Q2

Q3

LEGEND

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1 2

Wind sensors (mechanical & ultrasonic) Radiators and exhaust fans

3 Nacelle walls (fiberglass) 4 Induction generator

5

Encoders .............................................. p.32

Sliprings

Bed plate

6 Vibration isolator

7 Generator blower 8 Obstruction light

9 Air filters .............................................. p.51

10 Inverter, standby power & electrical connectors 11

Disc brake

12 Coupling and torque limiter ............... p. 28 13 Yaw bearings

Motors Gears

14 Bearing................................................. p.18

Lubricators ........................................... p.53

15 Multistage gearbox 16 Fire Suppression

17 Electrical control 18 Main shaft

19 Fans for oil cooling 20 Pitch controls

21 Pitch bearings

Seals

22 Main shaft bearing

23 Bolts ..................................................... p.21

24 Tower

(cables lifts, ladders and lighting)

25 Blades

Composites .......................................... p.34

Coating

26 Hub hatch

27 Safety rails

28 Nose cone (fiberglass)

29 Hub hydraulics...................................... p.24

30 Hub (casting) 16

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COMPONENTS OF A

WIND TURBINE ILLUSTRATION COURTESY OF:

Suzlon 9X 2.1 MW

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WINDPOWER

BEARINGS

BEARINGS What different kinds of bearings are used in wind turbines?

A WIDE RANGE of bearings are used to perform the different functions at several locations throughout a wind turbine.

Slewing Ring Bearings, for example, are typically found in the blade pitch and nacelle yaw mechanisms of a turbine.

As long as proper maintenance procedures are observed, the bearings usually experience few problems besides normal wear and tear over time.

Spherical Roller Bearings are often used in the main shaft of the turbine. It is also common to find a Tapered Roller Bearing (TRB) used in combination with a Cylindrical Roller Bearing (CRB) at this location, said Stephen Curtis, director of Renewable Energy Business. A number of different bearing designs can be found in the gearbox of a wind turbine, but most often, they are combinations of CRBs, TRBs, and ball bearings.

Bearing manufacturers are constantly developing new solutions to improve the lives of the components. An example of this, said Curtis, is a new seal that improves retention of lubrication.

Incorporating new designs into gearbox bearings has been a recent trend in bearing developments. Along with the CRBs and TRBs commonly used in gearboxes, integrated planet bearings have been added to reduce the total number of components in the assembly. Bearing races are machined into the surrounding components of the gearbox, said Richard Brooks, manager - Wind Energy Aftermarket at Timken Co. The semi-integrated design is most commonly used because of its ability to create greater gearbox density, reduce total gearbox mass, and eliminate fretting in the integrated component. Brooks said that this design also has potential to improve load sharing among the planet gears.

“These advances are driving improved gearbox reliability in the wind industry and are being introduced as upgraded retrofits for some older gearbox models,” said Brooks.

It is difficult, however, to make general recommendations regarding bearing installation and maintenance. “The reason is that bearing applications in a turbine are developed specifically for each customer and their components,” said Curtis. “Bearing manufacturers make recommendations about how to install and maintain the chosen bearing for each application.

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Emily Wild, WPE&D research assistant

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WINDPOWER

BEARINGS

Should a replacement gearbox bearing be case carburized or through hardened?

WHEN IT COMES time to replace bearings in a wind-turbine gearbox, purchasers will find two post manufacturing processes to choose from: Case carburized or through hardened. Dimensionally, the bearings with the same ISO designation will be identical in every respect. But under the surface they are different in significant ways.

Recent studies conducted by Rob Budny, RBB Engineering LLC and Rich Brooks, Timken Co., found evidence that points to one heat treatment as superior to the other. In one study, the bearings came from a turbine population of about 500 units and from two manufacturers.

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Intermediate bearing failure morphology

Axial Cracks on Bearing IR

(less than 1% failure in its gearboxes) while the other was responsible for 16% of its population failures, with a mean time to failure of 27,200 hours, about three years.

The intermediate speed bearings were ISO designated as NJ2334, a standard catalog bearing. Those from vendor A (<1% failure) were case carburized while vendor B bearings were through hardened. OK, but why the life difference?

Consider what the failure looked like. The crack, like the one in the image, Intermediate bearing failure morphology, has been pervasive. This axial crack failure mode is the leading cause of wind-turbine gearbox failure. It is almost always visible (on the left) on tear down.

The image on the right shows a cross-section through the bearing ring. This shows what's called an irregular white etch area, a tell tale structure associated with the crack failure.

The two also examined the residual stress present in each.

Both bearings had a compressive residual stress at their ring surfaces. That's an artifact of grinding, but look just below the surface and analysis shows that the case-carburized bearing had a relatively large compressive residual stress. That stress acts to keep cracks closed and provides a reliability benefit.

The through-hardened bearing had little if any compressive residual stress other than at the surface. That was one of the significant differences. Another attribute examine was the level of retained austenite. The bearings don't have a single microstructure, they are different, primarily in terms of martensite and austenite.

The case carburized bearing had high levels of retained austenite, greater than 30% at the surface and dropping to about 25% at one millimeter into the surface.

The through-hardened bearing however had essentially no retained austenite. This is a significant difference in the microstructure of the two bearings.

To summarize, the data showed that the case-carburized bearings were many times more reliable than throughhardened versions. Furthermore, they also had a beneficial residual compressive stress in the subsurface that the throughhardened bearings did not.

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irWEA in Sub-surface of Bearing

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2017 RENEWABLE ENERGY HANDBOOK

BOLTING What method and tools are used to fasten the bolts on turbines?

THE DECISION whether to use torque or tension to apply a bolt load is determined by the manufacturer of the turbine. Some manufacturers require the use of tensioning for the entire wind turbine, while others specify torque as the controlled bolting method for tower sections, blades and other turbine areas. Typically, foundation base bolts are tensioned, which is also the preferred method for offshore applications.

With many torque-related tools in the marketplace, a debate is growing around the proper way to the ensure bolt tightness of wind-turbine components. Increasingly, some say that tensioning and tension-related products should also be considered. The issue stems from variations in the torque and tension specifications supplied by OEMs. Wind turbines’ bolted joints are typically designed by mechanical engineers, guided by a German-based standard known as VDI 2230, which determines joint stress thresholds.

To properly calibrate torque and tension, and ensure accuracy, installers must apply equations such as those for a tightening factor. The tightening factor is the ratio of maximum tension to minimum tension (Tmax/Tmin) and it reflects the accuracy of the tightening method.

VDI 2230 accounts for the tension scatter or variation from the target value caused by the tightening technique via the tightening factor. Simply put, the higher the tightening factor, the more scatter you get, according to Barnaby Myhrum, applications engineer at Bellows Falls, Vt.-based Applied Bolting Technology. “The more scatter, the larger the bolts must be to increase safety.”

The VDI 2230 standard recommends a tightening factor of 1.6 for torque wrenches. In addition to tightening factors, bolting sequences beyond 11 bolts require solving for several variables.

One company, AMG Bolting Solutions, has created a Bolting Pattern & Sequence Guide to elimination the need to calculate many variables on 12 to 96-bolt applications. Other products, such as direct tension indicators (DTIs), feature lower tightening factors, which can play a crucial role in the dimensioning bolted-joint connections

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WINDPOWER

BOLTING

Three areas that require bolting include the: Nacelle – Use the appropriate torque and tensioning tools for the safe assembly of bearing and blade bolted applications.

Tower – Follow the manufacturer’s guidelines when tightening bolts on tower sections. A range of torque and tension tools are available for the assembly and maintenance of tower structures.

Foundation – For offshore applications, foundation bolting can be the trickiest to maintain. Typically, a range of safe and reliable foundation bolt tensioners will secure any type of bolt to any type of offshore structure. Hydraulic torque tools generally handle onshore foundation bolts.

Regarding tools: Electric torque wrenches operate on batteries and ac, up to 220V. The output torque is adjusted by the voltage. A torque wrench is often confused with an impact wrench. However, they are completely different tools.

Bolt tensioners stretch a bolt’s stud or shaft. The method gives a consistent tension load. A hydraulic bolt tensioner makes it easier to stretch the stud and is preferred over the usage of a hydraulic torque wrench for certain applications.

A hydraulic torque wrench is the main tool for applying torque to industrial fasteners. The wrench is simple to use because it is applied right to the nut.

Lithium ion batteries have significantly changed the world of industrial bolting. Today, a portable and lightweight Lithium Gun can put out as much as 3,000 ft-lbs and tighten up to 100 bolts with a single battery. These compact systems are ideal for bolting jobs in wind turbines, where the tool must be carried up tower to the nacelle.

22

Additionally, some battery-powered bolting systems, such as HYTORC’s Lithium Series, offer onboard documentation capabilities to let users record the torque applied to each nut and export it as needed. This provides new options for quality control in maintenance and manufacturing that were previously unavailable.

However, today’s technology makes going beyond 3,000 ft-lbs with a battery-powered tool impractical because the cumbersome tool weight.

For applications that require higher torque, pneumatic and hydraulic bolting systems are still the tools of choice. Pneumatic systems can go up to 8,000 ft-lbs (more is possible, but usually impractical because of weight) and hydraulic systems can go beyond 150,000 ft-lbs when needed. An additional benefit of hydraulic systems is that they can be interconnected and locked onto the job to provide a completely hands-free, simultorc system. For large bolted joints, using multiple tools is the best way to assure even and accurate bolt load across the flange which prevents unintentional loosening over time.

With so many different bolting systems and accessories available, the simplest way to determine the best tool for the job is to have a representative from a trusted manufacturer visit your site and perform a survey of the applications in question. Once complete, it is possible to recommend a system or combination of systems that provides the highest level of efficiency and quickest return on investment.

By Paul Dvorak, WPE&D editorial director

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HYDRAULICS

HYDRAULICS What functions in a turbine are powered by hydraulics?

THE POWER THAT PITCHES wind-turbine blades can come from either a hydraulic or electric devices on turbines rated at and below 2.5 MW. But for turbines over 3 MW, the job of pitching blades more often falls to hydraulics. The disk brake that brings the rotor and drive train to a halt is also hydraulically operated.

In a nutshell, the process of turning wind into electricity involves a rotor, gearbox, and generator, and related equipment. While small turbines often have fixed rotor blades – they do not pitch – larger turbines require blades that pitch and so are mounted on large bearings, 2 to 3-m diameter and more.

Driving each blade to a best pitch position decided by the controller requires a hydraulic pump, motor, reservoir, and associated hardware. For example, the pump and motor are usually mounted in the nacelle while hydraulic pistons are mounted in the hub. A hydraulic rotary joint allows passing hydraulic fluid from the stationary side (nacelle) to the rotating side (the hub). Pitch control then varies the pitch of the blades to maintain the generator at a nearly-constant rotational speed.

Aside from adjusting for changes in wind speed, the pitch of the blades may vary even during a 360-degree rotation of a single blade. Such adjustments are necessary because wind speed at the 12 o’clock position may significantly differ from its speed at the 6 o’clock position, according to Afzal Ali, Director of Marketing at Deublin. Typically, the pitch of each blade varies continuously and independently.

In an emergency, hydraulic pitch control can operate without an external power supply thanks to an accumulator, essentially hydraulic battery. It stores a small amount of hydraulic fluid under pressure. For emergency stops, hydraulic actuation provides the shortest stopping time, and a wider range of operating temperatures than alternative systems.

Hydraulic equipment usually includes an accumulator as a way to store energy in case of an

24

it

emergency shutdown. The hydraulic system usually fills the accumulator during off-demand periods, when pump flow is not allocated to system actuators. The pressurized fluid stored in the accumulator can then pitch the turbine blades to a safe position where they can stay until power is restored or the halting condition is corrected.

The rotor brake -- hydraulically activated -- engages during emergency stops (and that for many reasons) as well as during service work when the turbine is manually shut down. Another hydraulic system, one that activates yaw brakes, is comprised of several hydraulically-activated brake calipers which act on a break disk at the top of the tower. During normal turbine operation, brake calipers are under maximum pressure to keep the nacelle facing the wind direction.

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WINDPOWER

CABLES

CABLES

What should guide the selection of cables in a wind turbine?

WHEN SELECTING a replacement cable for a wind turbine, wind technicians should take several things into consideration.

Uwe Schenk, Global Segment Manager at Helukabel, explained several things to look for during the wind turbine inspection process. Technicians should first inspect the dimension of the conductor to ensure that it is able to carry the rated current levels. Hardened conductor material is a sign that the current carrying capacity has overloaded the cable and a cable with a greater current rating should be used.

Cracks in the cable jacket are another issue. When cracks are found, it is crucial that the cable is replaced with one that has greater resistance properties. It is also important to locate the source of the damage so that steps can be taken to reduce its effects on the new cable. Common causes of damage include exposure to ozone, lubricants, electrical fields and mechanical stress.

It is also common to find damage to the outer jacket and torsion fatigue in cables that function in the turbine’s cable loop area. These problems should be dealt with immediately because abrasions wear away the jacket and insulation, exposing the conductors and resulting in potential electrical hazards.

“Technicians should replace the loop cables with those that have a strong resistance to both abrasion and torsion,” Schenk said. “This torsion resistance is critical because cables that are not suited for this type of application will either have their jacket, copper strands or both broken due to the strain of frequent twisting and untwisting.”

Manufacturers are incorporating new technology into newer designs that increase cable lifespans by reducing the amount of damage they sustain. Insulation compounds are being developed for power cables to allow higher conductor temperatures and provide better abrasion characteristics, which improve the turbine’s overall efficiency.

Also, additional conductor materials are being used in certain wind turbine applications. For example, while copper was previously the only conductor engineers selected, aluminum is now considered a prime copper alternative for cables located in the tower and base areas. Aluminum cables are 60% lighter, have only slightly larger diameters and cost about half as much as copper cables while maintaining the same performance rating, Schenk said.

New technologies are also being developed for signal cables. These are now being constructed with a D-shield design to allow for better torsion performance.

They are also seeing enhanced mechanical properties as a result of better insulation materials. Depending on the application within the wind turbine, copper signal cables are being replaced by other materials capable of transmitting data signals just as in power cables.

Engineers now have access to fiberoptic data cables in turbine applications such as the pitch control systems. This control turns or pitches the blades as the wind speed changes to keep the rotor speed within operating limits. In addition, fiber optic cable allows real-time data communications and monitoring of wind turbine operations, said Schenk.

By Emily Wild WPE&D research assistant

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Cabling your entire wind turbine â&#x20AC;&#x201D; rotor tip to tower base.

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COUPLINGS & TORQUE LIMITERS

WINDPOWER

COUPLINGS & TORQUE LIMITERS What causes damaging loads in wind turbine drivetrains and how does torsional damping help?

This article provided by Paul Baker, AeroTorque Corp.

THE COST OF PRODUCING wind Transient loads from rotor and energy has steadily declined for the generator inertia are difficult to model past several years. While the increase accurately and almost impossible to in the size of wind turbines has been duplicate on a test stand. But they can one key contributor, improvements be measured in the field, and have been in reliability have also played a major for more than five years on many sizes, role. Hard lessons have been learned types, and brands of turbines. One thing about bearings, gears, generators, and is clear, this is not a turbine specific turbine control systems. Improvements problem, it’s an inertia problem. have been made to bearings, gears, Five years of field-measured data and lubricating oils. Condition from seven different OEMs show that monitoring techniques such as vibration transient loads are daily events to some The WindTC, a torsional control device analysis, wear debris analysis, and lube turbines and monthly to others. What’s for wind turbines drivetrains, comes from sample analysis are improved and in more, many torque reversals have AeroTorque. much wider use than even five years been measured at 1 to 3 times nominal ago. Testing capabilities have also operating torque. Oscillations are often improved with larger and more sophisticated dynamometers at 1.5 times torque (peak to peak) at a frequency of greater and modeling continues to advance as more dynamic models than 1/sec. are developed. The reliability discussion has also evolved from Smooth frictional torque control, one solution, greatly “How can we make turbines more robust?” to “What loads are reduces loads caused by transient events. By absorbing the causing these failures?”. As more people inside the industry energy early in the event, it lets the turbine operate under the come to the realization that it is not normal operating loads loads for which it was designed and tested. The graph, Turbine that are problematic, rather the occasional transient events stopping protocol, demonstrates results of field measurements that are causing the most damaging loads. during a stopping event on side-by-side turbines, one with Before discussing how a torsional damper reduces severe and one without torsional damping, a solution that can be transient loads, it’s important to understand where damaging retrofitted to most modern turbines, easily and with a fast loads come from. Transient events can be caused by nature payback. or related to control systems. Nature induced transients Don’t confuse Torque Limiting with Torque Control. come from wind gusts, ridgeline effect, wake effect, wind Traditional style torque limiters have been employed for years shear, and sudden changes in wind direction. Events related in gearbox to generator couplings. While these can protect to control systems include starting and stopping protocols, the spacer from extreme loads, it has to be set so high that and pitch lube and brake tests. Necessary stopping protocols it cannot protect against torsional reversals. To accomplish intended to protect the turbine often create the worse torsional control, it must react at a lower setting during a transient loads of all. Under normal operation, the drive train torque reversal. masses wind up almost like the rubber band on a toy airplane The WindTC torque controller acts to extend other (huge exaggeration), but they are ‘in sync’. When the system reliability improvements and enables production improvements experiences a sudden change (transient) in dynamics, the while improving reliability. Because the device dissipates the reaction can be a violent torque reversal, a significant torque energy early during the transient event, it protects the drive oscillation, and usually both. These drive train loads react train and the entire turbine from the related reactionary loads through the bedplate and the entire turbine structure down to which may manifest as bedplate cracks, yaw pinion/gear the foundation. problems, tower flange faster tension, and more.

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WINDPOWER

COUPLINGS & TORQUE LIMITERS

What is the job of a coupling in a wind-turbine drivetrain?

MECHANICAL COUPLINGS connect shafts so one can transmit rotational power to the other while accommodating some misalignment that is almost always present. For wind-turbine drivetrain applications, some designs are better suited than others.

Flexible couplings in wind turbines are used on the high-speed (the output) shaft of the gearbox to drive the generator. The task is made more difficult because the coupling is working in a nacelle where everything − gearbox and generator mostly − moves around, a bit thanks to the high vibration environment. While the gearbox and generator are bolted to a frame, it is not the large concrete inertia base frequently used in ground-level production settings.

Regarding misalignment, the couplings must accommodate it in considerable radial, angular, and axial form without wear and maintenance. In addition, couplings should provide electrical insulation, an ability to handle loads well beyond the normal application needs, and weigh as little as possible for easy installation.

One such coupling, from Zero-Max, provides an example of the features useful to a wind turbine. For instance, it is available as an upgrade replacement for existing wind turbines and for OEM applications. The company says the design has been tested under conditions simulating a 20-year load spectrum of continuous operation.

In addition, the turbine couplings are said to handle torque spikes and high misalignment issues.

The coupling comes with composite disk packs (the elements that let it flex) at both ends of a center spacer that is made of composite or steel. Composite disk packs provide a distinct advantage over other coupling designs by allowing for a surplus of parallel and axial misalignment while remaining torsionally rigid through all harmonic ranges of a wind turbine’s oscillating load.

The coupling further protects the generator and gearbox bearings by transferring lower reaction loads.

And, the lack of conductive properties of the composite material make it useful for electrically insulating the turbine’s gearbox from the generator, thereby eliminating stray currents that can leak across a coupling and damage gearbox bearings and gear teeth.

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The composite materials also withstand all types of environmental elements, including temperature extremes from -40 to 70°C, along with moisture and chemicals common to wind-turbine nacelles. Designed for onshore and offshore turbine drivetrains with capacities up to 5 MW, the couplings are said to provide extreme endurance in a lightweight package.

Lastly, the units are easy to install either on the production floor or in the cramped, up-tower environment and they operate well in new OEM turbines or existing drivetrains. Standard models and sizes include single and double flex models with clamp style hubs with or without keyways. The torque capacities range from 40 Nm to 1,436 Nm and beyond with speed ratings that start about 4,000 rpm.

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High Speed Shaft Solutions

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Protects wind turbines against peak loads, reverse torques and grid shorts.

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WINDPOWER

ENCODERS

ENCODERS

What criteria should be considered when selecting and maintaining encoders for wind turbines?

The encoder has been mounted on a slip ring for installation in a wind turbine. Key attributes to consider when choosing encoders include electrical characteristics (such as operating voltage and output configuration), shock and vibration resistance, operating temperature, lightning protection, and maximum shaft load. (Photo credit: UEA)

WIND TURBINES require accurate and reliable blade pitch-control to optimize power generation and safeguard the asset from extreme conditions that could cause damage. Turbine generators also rely on precise feedback to properly control and synchronize energy output with line frequency. Disruption of these processes can lead to poor turbine performance, downtime, or costly repairs.

Encoders are small devices that play a big role in productive wind-turbine operations. These sensors provide reliable feedback for wind speed, control, over-speed protection, and position.

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“Encoders or rotation sensors, can be used in a number of places on wind turbines,” explains Christian Fell, Chief Operations Officer of FRABA-POSITAL North America, an industrial sensor engineering company. “Incremental encoders are ideal for monitoring the rotation speed of the rotor. They transmit a stream of electrical pulses at a frequency that is proportional to the speed of rotation of the encoder’s shaft. Absolute encoders, which measure the absolute rotation angle, are typically used to provide feedback on blade pitch and the azimuth or yaw angle of a nacelle.”

Application encoders can be located deep within a turbine’s nacelle and hundreds of feet off the ground so reliability is key, according to Fell. “Devices with communications interfaces that are compatible with

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WINDPOWER

a turbine’s control system will simplify encoder installation and monitoring.”

Extreme temperatures, electrostatic discharge, vibration, and exposure to hydraulic fluids can also impact and shorten the life and performance of turbine components, including encoders.

“Reliability is crucial,” says Fell. “Chronic vibration means the general mechanical durability of encoders is a must. But weather and environmental concerns are also an issue. Wind turbines present harsh conditions for instrumentation, including extreme temperatures, moisture, dust, and other contaminants.” He points out that encoders should carry a minimal ingress protection rating of IP67. A higher IP class is recommended for offshore turbines with a salt-spray resistant IP69K housing.

Safety is also an important consideration. For yaw positioning, choose encoders with integrated end switches, says Fell. “In a typical design, the nacelle should not turn more than 3.5 revs total range so as not to damage the power or control cables running between the nacelle and tower. Because these end switches are derived from the encoder position, a safety rating of at least SIL2 is necessary.”

While maintenance is a concern for most turbine components, Jesse Shearer, Sr., an Application and Design Engineer at UEA, claims that industrial encoders should be made to last. “Most should last the life of the slip ring but if a device fails, they’re typically quite easy to replace.

Once accessed, a couple of screws and an electrical connector is all that’s needed,” he says. Granted, this is assuming a wind technician is set and ready to safely climb uptower.

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To prevent encoder failure, Shearer suggests adhering to the manufacturer’s recommendations and not over-taxing the device. “The most common failure mode with an encoder once it’s made it to the field is a bearing or shaft failure,” he says.

“So avoid overloading the shaft on the encoder, which will cause the optical disk to break.”

Optical encoders, which use an optical disk and a reader, tend to experience the most breakdowns. But the wind industry is slowly beginning to incorporate another option. “The industry is moving more toward magnetic encoders, which are finally trending down in price and are much more robust than optical encoders,” says Shearer.

Magnetic encoders are available in incremental and absolute versions. These sensors can detect a change in magnetic field and convert this information to a sine wave. They are ideal for use in wind turbines because of how well they withstand high temperatures and environments with extreme shock and vibration.

“The latest generation of compact and highly accurate magnetic encoders are appealing to the wind industry,” agrees Fell, and says they are easy to integrate into new or existing turbine designs. “Some advanced control systems even optimize energy production by making small adjustments to the pitch of blades as they pass in front of the support tower.” This is possible because of the quick response time of magnetic encoders.

“These magnetic devices eliminate the need for mechanical contact between sensing elements. This reduces wear and prolongs longevity — the goal for any turbine owner or manufacturer.”

By Michelle Froese Senior editor, WPE&D

WINDPOWER ENGINEERING & DEVELOPMENT — 2017 RENEWABLE ENERGY HANDBOOK

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WINDPOWER

BLADE COMPOSITES

BLADE COMPOSITES How are blade materials and manufacturing keeping up with larger turbines?

THE WIND INDUSTRY has set installation records over the last couple years. That trend may continue with global wind capacity predicted to double in the next five years, according to the Global Wind Energy Council. This growth trend is thanks, in part, to a developing offshore wind market and larger wind turbines with longer blades.

“The wind industry has been increasing blade length approximately 6.5 feet per year over the last 10 years,” said Mark Kirk, CCT, Wind Energy Sales Manager at Composites One. “This increase in length has allowed the industry to increase production by using larger turbines and, therefore, lower the cost of energy.”

However, the longer the blade, the more reliability and stability come into question. Kirk attributes materials and manufacturing for letting turbine blades keep up with ever-

Advanced materials and manufacturing processes means blades can efficiently and cost-effectively keep up with the installation of taller towers and larger wind turbines. (Photo credit: CompositesOne)

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growing towers. “Because of composite materials, blades can spin faster and capture winds at lower velocity. Composites offer wind manufacturers strength and flexibility in processing with the added benefit of a lightweight material,” he says.

Composites are made of two or more materials with different physical or chemical properties that when combined, do not fully blend but together become stronger and more durable. Materials for the wind-turbine blade market include resins of glass fiber reinforced polyester, glass fiber reinforced epoxy, and carbon fiber reinforced epoxy.

“Combining glass fibers with a resin matrix results in composites that are strong, lightweight, corrosion-resistant, and dimensionally stable. They also provide good design flexibility and high-dielectric strength, and typically require lower manufacturing costs,” says Kirk, who points out that high-strength composite materials, such as carbon fiber and epoxies, are now also being used for highperformance blades.

“Today’s turbine blades and components must meet strict mechanical properties, such as high rigidity and resistance to torsion and fatigue. In addition to these mechanical properties, the finished product must offer excellent corrosion resistance and a high-temperature tolerance. Composite materials can offer greater stiffness in many instances, and reduced weight on finished parts,” he adds.

But that’s not all. Because of their flexibility, composites materials make repairs easier for wind technicians and provide for a longer blade

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life. The materials can also be used for other turbine components. “The move to composite nacelle covers, composite spinners, and in some cases more advanced closed molding of these composite components, has also reduced the over all weight of the units over traditional steel and aluminum so turbine costs are coming down.”

Materials make up more than 90% of the manufacturing costs of a blade, so if turbines are to successfully grow in size, reduced costs are key. “The challenge for today’s wind industry is clear,” says Alexis Crama, LM Wind Power’s Vice President of Offshore Development. “The industry must increase annual energy production, and reduce costs through innovation in material use and manufacturing technologies, all the while considering reliability and the efficient servicing of turbines during operation.”

He says that as turbine blades get longer and more offshore projects develop, the demand for higher reliability and lower costs will only increase from wind-farm developers. “Building larger blades presents new design challenges, which in many ways involve re-thinking the materials, structure, and other characteristics. Rotor blades are arguably one of the most influential pieces in terms of the cost of energy.”

Along with building the world’s longest blade to date (at 88.4 meters — the blade is currently undergoing testing for product validation in Denmark), LM Wind Power recently unveiled research into a modular blade-molding concept to increase flexibility in production when making larger and longer blades. The new process extends the rotor diameter by attaching variable tip lengths, without the added expense of building a new blade mold.

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This process enables separate manufacturing of the blade and tip, followed by a traditional joining technique that permanently assembles a blade, explains Crama. “Through a combination of reduced production costs, increased rotor size, and optimized wind-farm output, these modular products are expected to cut the cost of energy for offshore blade applications by about 6 to 8%.”

He adds: “Ultimately, the winners of tomorrow’s wind industry will be those who can adapt, innovate, and expand at the lowest cost.”

By Michelle Froese Senior editor WPE&D

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SITE ASSESSMENT

SITE ASSESSMENT What are the major wind-farm siting issues facing developers today?

SUCCESS OF A WIND PROJECT starts by selecting an optimum site and, for that, there are four key aspects of wind-farm siting, said Chris Parcell, Director of Feasibility and Development at SgurrEnergy. The first is to inspect the land and determine whether it is possible to obtain construction permits. Next, a developer must analyze the wind resource at the site. This involves measuring wind speed to ensure it can generate enough energy to create revenue, and deciding on which turbines will work longest and require the least possible maintenance.

A developer then has to examine the grid connection, which is necessary to export power and earn revenue. The costs and capacities of a grid connection vary depending on location.

Finally, environmental restraints must be weighed. Constraints may include ecological concerns, noise, shadow flicker, and visual impact.

When siting a location for a wind farm, several protocols are worth observing for success. Most important is conducting a professional wind-measurement campaign.

“Wind measurements are needed to determine the economic viability of the project, as well as to determine the suitability of the turbine design for a site,” said Jay Haley, Principal in Charge of Wind Energy at consulting firm EAPC. To obtain the most reliable data possible, developers should use quality instruments to collect data at the wind-turbine hub height for at least one full year prior to installation.

As wind turbines get taller and blades longer, it is critical to measure wind speeds at hub height and within the vertical profile of the swept area of the blade. Failure to obtain accurate wind measurements could jeopardize the chances of getting turbines certified for a site. (Photo: Joy Powers; EAPC)

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Parcell added that developers must also carry out an environmental impact assessment, which is typically required by the permitting authority and financial institutions. These surveys consist of studying the ecology and ornithology of the site, peat probing (a soil analysis), noise modeling, and visual studies. The goal is to avoid or minimize potential impacts on the environment.

The available transmission capacity is also important to inspect, said Haley. Depending on the upgrades or additions necessary to accommodate the wind farm, the transmission connection could be a major cost item, which feeds into the financial feasibility of the site.

Parcell explained several other sensitive features worthy of consideration in siting protocols, such as the internal track layout and access points to the site based on its topography and site survey results. Together, all of this information can help accurately determine the optimal turbine layout for the site.

Developers are often met with challenges when performing site assessments. “Wind development is a complex and expensive process,” Haley said. “Bad decisions made early on can have expensive or even disastrous consequences later on.”

With this in mind, developers must understand that each site will present unique problems depending on the requirements of authorities and financial institutions. To help combat issues that arise, it is important to plan ahead and devise specific plans of action.

Another important task for developers is to strategically identify and solve challenges early on in the development process. Common issues include reducing the effect of wind turbines on aviation radar, managing forestry to maintain the safety of animals, and compensating residents on or near a proposed wind farm, said Parcell. Developers must also understand the requirements of banks and lenders whom they are working with to avoid costly delays.

During the development of a wind farm, it is also necessary to involve the community in the process.

“Communities are important stakeholders in wind-farm developments because they could be directly affected in many ways, such as by construction, traffic, visual impact, or noise,” added Parcell.

What’s more, with local support of a project, it is easier for developers to secure land leases and permits. It is common to see a planning committee determine wind-farm planning applications. These committees are typically made of elected members of the community who will represent the views of their constituents, which emphasizes the importance of gaining local support.

Wind development comes with its own unique and often subtle development challenges that can easily make or break a project. A full understanding of those subtle industry differences can save time, cost, and potential pitfalls when developing a new wind farm. (Photo: Joy Powers; EAPC)

By Emily Wild, WPE&D research assistant windpowerengineering.com

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CONSTRUCTION, INSTALLATION & DEVELOPMENT

CONSTRUCTION, INSTALLATION & DEVELOPMENT What is changing the way wind farms are constructed?

SEVERAL TRENDS underway are changing how wind farms are constructed. In a nutshell, the trends have been working to trim time and cost from the work that goes into a wind farm and that has led to new equipment and construction methods. The principles of lean manufacturing are being applied to trim waste time and labor as it is found in construction activities.

On the financial side, the big stimulus to get things done as quickly as possible has been the Production Tax Credit. It provides about 2.3 ¢/kWh for the power produced. That figure will drop 20% in 2017, 40% in 2018, 60% in 2019, and will disappear in 2020. Before that, however, the wind construction industry will remain working at full speed using modern construction equipment and methods.

The notable new feature on the crane is the variable position counterweight that shortens work time. Controls automatically position the counterweight based on the crane’s load and required radius. The weight moves on a track either away from the crane cab or toward it to keep the center of gravity over the crane tracks. The capability has several plusses. For one, the crane need not set up for every lift on a jobsite. It can be erected and set up once and then the crane adjusts itself for different lifts. The moving counterweight means less overall counterweight is needed for work. On conventional high-lift cranes, counter weights (some in 10-ton

A tower and rotor are ready for assembly at the Tucannon River Wind Farm during construction in the summer of 2014.

One piece of equipment in particular is the MLC650 crane from Manitowoc. The VPC MAX option increases the cranes capacity from 716 to 770 tons, and the luffing jib adds to the standard 331-ft. lift height for a total of 357 ft. The company says it has a 50% greater load capacity than competing models. That’s useful on wind farms because it allows lifting larger and more complete nacelles, or a hub and rotor that have been assembled on the ground – not in the air.

Building on the ground is easier than lifting and fastening each blade to a hub 300-ft. up.

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increments) are added to a fixed bed or removed as lift needs change, a time consuming task. Also, a wider track than the 60-in. standard is available which means lower ground bearing pressure, hence, less jobsite prep.

Another factor that has improved wind farm construction is the application of lean construction principles. These come from lean manufacturing principles that have the goal of identifying and eliminating waste from every step in a project.

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CONSTRUCTION, INSTALLATION & DEVELOPMENT

A few lean construction principles include: • • • •

Making sure value-added activities flow smoothly Buildings should be prefabricated and modular Nothing is made or delivered until needed Recognizing that perfection is sought by a commitment to continually improve the entire process. One construction crew leader, for example, says that after each project, subcontractors and other bosses gather to discuss what slowed things down and how to eliminate them in the next job.

An example of applied lean construction comes from the 267-MW Tucannon River Wind in Washington State. It received a Gold rating from ISI Envision by meeting its sustainability principles. For instance, the wind farm was sited to avoid all wetlands and surface water, floodplains, steep slopes, and other potentially fragile or hazardous terrain.

Before construction began, a design team evaluated ways to reduce the project’s net embodied energy. For example, turbine foundations were designed to reduce the amount of required concrete and a significant portion of construction materials used in the project was sourced locally. This cut transportation costs and boosted the local economy. In addition, materials excavated during construction were retained and reused onsite where possible.

The effort is paying off. Not long ago, it was safe to use $2 million/MW as a cost estimate for a wind farm. Today, thanks to lean principles, one farm was constructed in Iowa at $1.69 million/MW.

By Paul Dvorak WPE&D editorial director

Photos courtesy of TGM Wind Services

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2017 RENEWABLE ENERGY HANDBOOK

FALL PROTECTION What should wind technicians know about fall protection equipment?

Workers at heights of six feet or greater must have safeguards in place to protect them from the risk of falling. A properly trained worker will also ensure all fallprotetion equipment is inspected and fitted prior to use.

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ACCORDING TO the Occupational Safety and Health Act (OSHA), falls are the leading cause of fatalities at construction sites in the United States, accounting for about one-third of all incidences in the industry.

Workers at heights of six feet or greater must have safeguards in place to protect them from the risk of falling.

The most effective way to ensure safety at heights is through proper equipment use and up-todate training.

“Good training is about meeting the specific needs of workers based on the type of work they’ll perform,” says John Eckel, Sr. Technical Training Specialist at Miller Fall Protection. He adds that a properly trained worker understands the basics of the job, such as how to properly employ fall-protection equipment, climb a wind tower, and work inside of a nacelle.

To safely and effectively work at heights, wind technicians must identify existing and potential hazards on the job, and have the authority to take corrective actions when necessary. Technicians should be trained by a Competent Person Trainer, as established under ANSI Z359.2, and meet the authorized rescuer level under ANSI Z359.2.

ANSI refers to the American National Standards Institute, which provides performance standards

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FALL PROTECTION

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for fall protection in the U.S. The organization also requires workers to return every two years for refresher training.

Wind technicians should also keep apprised of what’s new and available in fall-protection equipment, including how to inspect all safety gear, use the hardware, and don a harness correctly. “Often the biggest mistake made is the size of the harness, which doesn’t match the student’s torso. But workers must also understand how to use the different anchors and connecting devices, and know where they’re located on a turbine at each different jobsite,” says Eckel.

Craig Firl, Technical Manager at 3M Fall Protection, says full compliance to applicable safety standards is critical in the wind industry (OSHA and ANSI both apply in the U.S.), and that fall-protection equipment must also fit its intended application. “It is important to understand how and where the equipment is going to be used,” he shares.

“For example, on a full-body harness determine what type of comfort level is desired and where you need connection points – at the waist, front, or dorsal? Do you need a seat sling or tool pouch? And do you have concerns about arc flash or potential damage from high heat?” These are important questions to ask when selecting the correct product for the application.

Over the past few years, fall-protection equipment has developed significantly, particularly in terms of comfort and available features. Many full-body harnesses are now equipped with more padding and extra support, so wind technicians can comfortably wear them for longer periods of time. The material of such gear has also become lighter, but without compromising strength or durability.

“Fall-protection equipment has also made technological advancements, with many types of connecting systems capable of handling increased fall distances and higher capacities,” says Firl, who also points out that ANSI has produced new standards on

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By Emily Wild WPE&D research assistant

Climbing with

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harnesses and self-retracting lifelines, meaning the equipment is safer.

When caring for fall-protection gear, Firl recommends storing products in a cool, dry area, and out of direct sunlight to keep them in proper working condition. Most manufacturers will provide direction on storing and inspection steps in the instruction manuals. “Regardless, equipment should be inspected before each use and formally examined by a qualified inspector at least once a year,” advises Firl.

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OPERATIONS & MAINTENANCE

OPERATIONS & MAINTENANCE How has wind-farm operations and maintenance changed over the last few years?

A good O&M plan will help prevent equipment decline or failure, and increase long-term wind-farm efficiency and production. According to a recent market report, the wind-turbine O&M industry is expected to increase from $9.3bn in 2014 to $20.6bn in 2023.

AN OPERATIONS and maintenance (O&M) strategy is important for a wind-farm owner because of the long-lasting impact it can have on the profitability and efficiency of a wind site’s operations. According to Aaron Barr of MAKE Consulting, a research firm focused on renewable energy, larger owners often pursue self-perform (maintenance) strategies to fully control their assets, trim costs, and optimize O&M practices. Smaller owners, however, may not be able to justify the capital expense required to self-perform and instead rely on services offered by OEMs. Although at a cost premium, these 44

services provide minimal risk strategy to troubleshoot turbine performance issues, offer access to spare parts, and ensure high technical availability. On the other hand, many service providers can offer maintenance services at a discount, but may not be able to provide all elements of the O&M scope.

Many turbine owners struggle with major component reliability. Large components, such as gearboxes, generators, blades, and bearings, are expensive to repair and may result in significant downtime and lost production. Over time, the nature of these failures has shifted.

“For years, gearboxes were the focus of asset owners because they were experiencing high failure rates and substantial replacement costs,” said Barr.

“However, reliability engineering efforts have improved the failure rates of gearboxes, and advanced diagnostics and condition monitoring efforts have been combined with innovative up-tower repair processes to dramatically reduce the cost of gearbox service.”

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By Emily Wild, WPE&D research assistant The focus has recently shifted to other major components, such as bearings, generators, and blades, which have developed reliability concerns as OEMs build larger turbines.

The supply of qualified technicians has also presented major challenges to owners, explained Barr. The U.S. fleet of turbines has grown substantially while the number of technicians has struggled to maintain pace. According to the U.S. Bureau of Labor statistics, wind-turbine technicians will be one of the fastest growing occupations over the next 10 years. Although the shortage of technicians is an issue for large asset owners, it also creates a workforce opportunity for the U.S. job market.

The biggest opportunities for cost savings over the life of a turbine lie in attention to detail, adherence to rigorous routine maintenance practices, and leverage of power of data, said Barr. The costly failures that occur in turbines are typically a result of improper maintenance, inadequate lubrication, or missing a data signal that would have provided advanced warning of a pending failure. Leveraging data can lead to advanced prognostics of component failure, improved tracking of turbine conditions, optimized energy production, and improved scheduling of routine maintenance, said Barr.

The wind-turbine services market is currently one of the most innovative areas of the industry and is developing new services and technologies to help owners maintain their turbines. Many new technical innovations focus on the aftermarket, including performance improvements, reliability upgrades, diagnostic tools, prediction algorithms, and low-cost repair processes.

There are also innovations such as aerodynamic blade enhancements, control card reliability improvements, up-tower gearbox repair processes, and mobile cranes that help reduce risk, lower costs, and improve operating efficiencies.

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OPERATIONS & MAINTENANCE

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Wind-farm owners representing about 12% of global wind-turbine assets have founded a peer-to-peer online platform, called o2o Wind. The o2o Wind forum takes down the barriers to information exchange that typically get in the way of optimizing wind energy assets. It is the first initiative of its kind aimed at fostering wind-farm O&M best practices through a collaborative approach.

Members share the common objective of optimizing turbine yields, and many problemsolving discussions relate to issues with components, such as rotor blades, gearboxes, or substations. Although the topics addressed on the forum are mostly technical, they may contribute to important investment decisions.

The platform also hosts many discussions on offshore O&M. “When it comes to trouble-shooting many of the O&M issues encountered, wind-farm owners are not competitors,” said Mårten Nilsson, head of the o2o Wind platform. “On the contrary, they are in the same boat, and that’s why adopting a collaborative approach to problem-solving makes a lot of sense.”

A strict member-selection criteria is intended to maintain integrity along with a high level of expertise throughout the network. “Our members recognize that the most valuable information for turbine owners is the hands-on experience held by their peers,” said Nilsson

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2017 RENEWABLE ENERGY HANDBOOK

CONDITION MONITORING What are the new ideas in condition monitoring for wind turbines?

ROUTINE WIND-TURBINE MAINTENANCE once required a wind technician to suit up and climb uptower just to inspect what components might need upkeep or repair. Today, wind farm CMS firms can offer owners a whole new way to approach operations and maintenance, thanks to condition monitoring and advanced prognostic systems.

Condition monitoring is an O&M tool that helps wind-farm owners and operators monitor the health of turbine components and related electrical systems.

Its purpose is to predict maintenance issues so site operators can conduct repairs and replacements only when needed to avoid unnecessary and costly up-tower jobs.

Although the intent is to cut time and cost from O&M tasks, condition monitoring system (CMS) have become rather detailed in accumulating and analyzing data and, therefore, costly.

“Over the last few years a lot has changed in the field of CMS and data acquisition,” says Dr. John Coultate, Head of Engineering Development at Romax Technology. “For example, the idea of putting ‘intelligence’ in the data-acquisition box or in turbine sensors has proved unnecessary — this just drives up cost and the limitations on data storage and transmission.”

Dr. Coultate points out that advancements in embedded computing also means that high-performance systems can be deployed at much lower prices. “Most systems today rely on an older and high-cost approach to architecture. But we’re learning that by using less expensive sensors and electronics in each condition monitoring unit — and only one in each turbine — the cost of CMS comes way down,” he says. “This is particularly important for operational wind-farm owners looking to retrofit their monitoring systems because they often don’t have the budget for new units.”

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Romax Technology’s ecoCMS is a new condition monitoring system for turbines aimed at making high-performance monitoring more affordable for wind-farm owners. EcoCMS combines Cloud-based software technology with cost-effective hardware to create reliable asset monitoring and predictive maintenance.

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CONDITION MONITORING

Of course, cheaper is not always more efficient so Coultate and his team at Romax had to think outside the box.

“The traditional approach needed a change. So we put all the complex mathematical algorithms in Cloud computing — rather than on expensive sensors and electronics — and reduced the condition-monitoring unit to a simpler, more robust piece of equipment.”

This lets a wind farm transmit data collected from every sensor on its turbines, wirelessly or by Ethernet, back to a single server for data processing. Essentially, this provides three benefits: cost-savings on sensor equipment, a better more extensive data-collection reach, and a more scientific approach to data analyses.

Sentient Science’s Stephen Steen has also noted the digital change in monitoring capabilities. He is the Head of Industrial Internet Solutions for the company. “Many windturbine operators have begun the move from condition-based monitoring systems, which include vibration sensors, to a material science-based prognostics approach,” he says. So where condition monitoring once gave turbine operators a heads’ up regarding potential equipment failures to minimize turbine downtime and related costs, advanced prognostic systems can predict failures before they occur and let turbine operators plan ahead.

“An initial fleet risk assessment can now provide the failure rate data of each individual turbine in a fleet over the next 20-plus years.” Steen says this means asset managers are able to build multi-year budgets and maintenance forecasts to lower their O&M costs. “The move to digitalization can also offer a rolling five-year forecast into the predictive health of each asset at the major system and component level.”

The forward-looking approach allows “virtual testing” of each asset using a material science-based method that can provide savings beyond lower O&M costs. “It facilitates supply-chain management because wind-farm operators can better anticipate when and where to expect component replacements. This digital approach also lets an operator simulate the impact of different supplier components and how they will affect asset life,” he says.

This is no small feat. CMS with advanced prognostics is providing turbine owners with a better understanding of their asset health at a micro-structural level, which means a more accurate prediction of failure rates and more cost-efficient and effective O&M planning. As Steen explains, this deeper level of asset life understanding improves a wind-farm owner’s ability to negotiate warranty and insurance contracts and strategize multi-year business plans and initiatives.

“Digitalization provides the forward visibility needed to reduce the cost of energy by $10/ MWh as it enables smart decision making and multi-year forecasts,” he says. “Building virtual models of each asset on a wind farm and monitoring how they perform under the operating conditions is where the future of wind energy is moving.”

By Michelle Froese, Senior editor WPE&D

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FILTERS

2017 RENEWABLE ENERGY HANDBOOK

What features should you consider when choosing filters for a wind turbine?

IN THE WIND INDUSTRY, simple logistics places importance on a well-planned operations and maintenance strategy. The geographic location, weather conditions, and height of most wind turbines make even the most basic gearbox or hydraulic repairs a daunting and costly task. For that reason, filtration is critical in wind turbines.

Gears and bearings ride on a film of oil only a few microns thick. This might seem insignificant, but quality gear oil and fine filtration are imperative to avoid unnecessary wear and equipment downtime. Filter elements are typically rated based on their ability to remove contaminants of specific targeted sizes from a fluid under set operating conditions. Enough contaminant particles, measuring only 1-μm in size and invisible to the human eye, can knock out a 20-ton gearbox.

“Full-flow and bypass filtration have benefits that can increase uptime, save costs, and extend maintenance intervals”, says Michelle Arceneaux, Sr. Product Manager for Des-Case, a manufacturer of contamination control products for industrial lubricants. “Always make sure the filter you choose accommodates the needs of the system and filters the targeted particles of concern.”

For example, water-removal filters and fine micron-rated filters are best used for hydraulic and gearbox fluids. On heavier gear oils, flow rate, pore size, and dirt-holding capacity are the key features to look for. “The most important selection criteria for kidney loop (offline) systems are filter pore size and flow rate. Also, make sure the flow rate is right for the sump size,” advises Arceneaux.

She says that a kidney-loop filtration system should not take more than 10% of the total sump volume per minute.

“Closer to 5% would be safer. And it’s important to filter the entire volume at least 7 to 10 times in a 24-hour period for supplemental filtration and once per hour for primary filtration.

And be sure to look for automatic emergency reliefs or bypass with these systems,” she adds.

Fortunately, today there are more options than ever for intelligently and efficiently improving a turbine’s reliability.

However, Arceneaux points out that clean oil is only half the battle when it comes to maintaining good turbine health.

“Did you know that on average, it costs 10 times as much to remove contamination from a system than it does to exclude the contamination in the first place?” she asks. “And in the wind industry, this figure is probably even higher.” To improve reliability and keep particles from entering a system in the first place, Arceneaux recommends a high-quality desiccant breather.

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A desiccant breather replaces the standard dust cap or OEM breather cap on equipment, and provides better filtration and protection against even the smallest particulates that can destroy the effectiveness of turbine components. As air is drawn into equipment through the breather, the layered desiccant filter elements remove particulate. “As an added benefit, desiccant breathers are also very effective at removing existing headspace moisture,” she says.

When selecting desiccant breathers, look for things such as a high flow rate (especially for hydraulics), check valves, and a large volume of filter media and silica gel to extend the breather life.

“Things like over-sized check valves in some desiccant breathers already combine the benefits of high flow rate with longer breather life,” says Arceneaux. “More media typically means a longer life.”

In the wind industry, maintenance tasks are a challenge and, for this reason, it is important to choose components that last.

“Compare dirt and water-holding capacities of different filter elements, as well as their efficiencies. On average, appropriately sized breathers and filter elements should last nine months or longer when in operation,” Arceneaux says. “And a better filter choice means more reliability, greater longevity, and less worry for turbine operators.”

By Michelle Froese, WPE&D senior editor

The Des-Case EX-series breather combines offers a high flow rate and extended life from check valves. As wet, contaminated air is drawn through the unit, multiple 3-micron polyester filter elements remove solid particulate, and color-indicating silica gel extracts moisture. When air is expelled from the container, the top foam pad prevents oil mist from contacting silica gel or entering the atmosphere.

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FILTRATION & FILTER SYSTEMS

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Contamination and degraded fluid quality cause inefficient operation, component wear, and eventually failures in all hydraulic and lubrication systems. We have the tools that are needed to prevent such occurrences and at HYDAC we recommend a three step approach to controlling contamination in any system:

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The money invested in contamination control can easily be justified when the resulting machine availability increases significantly. HYDAC Fluid Service can return 90% of the fluid related downtime costs.

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WINDPOWER

2017 RENEWABLE ENERGY HANDBOOK

LUBRICANTS How are lubricants treated for wind turbines?

QUALITY COMPONENTS are integral to a high-performing wind farm, and ongoing care and maintenance of its parts are just as important. Turbines are exposed to some of the harshest conditions in the industrial world, such as extreme temperatures, vibration, and debris. In these conditions, proper equipment lubrication is essential. It can help protect system components, minimize unscheduled downtime, reduce costs, extend oil-drain intervals, and enhance safety through reduced human-machine interaction.

To this end, the wind industry is continually seeking advances in oil and lubrication aimed at increased turbine efficiency. For example, it is now generally accepted that synthetic gear oils (versus conventional mineralbased oils) offer more protection from common gearbox failure modes including micropitting, which results in reduced gear-tooth accuracy and bearing wear. But how turbine oils are maintained and treated over time is also an important consideration for long-term performance and equipment protection.

“If you’ve been following wind-turbine equipment maintenance trends, you may have heard some chatter about top treating turbine gearbox oils with additives as a strategy to mitigate lubricant degradation and extend oil life,” says Gary Hennigan, a National Account Executive at ExxonMobil.

A high-quality, balanced lubricant can help protect wind-turbine components and reduce maintenance costs by extending oil-drain intervals and minimizing equipment downtime. (Photo: ExxonMobil)

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T:9”

Keeping wind turbines and their components up and running is your job. Mobil™ has the lubrication solutions to help, with product technology that protects against extreme conditions and maintenance services that help ensure equipment reliability. Learn more at mobilindustrial.com

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T:10.875”

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To top treat oil, turbine operators use condition monitoring to identify when an oil’s additives start to deplete and then “re-additize” that oil with the addition of after-market additive packages. “While it’s important to identify opportunities to optimize oil life and equipment reliability, relying on additive top treating as part of your primary lubrication strategy is not a recommended long-term maintenance strategy,” he says.

The reason? Top treating may introduce new contaminants to oil, which can alter the balance of the lubricant’s formulation and, subsequently, impact turbine performance. “Surfaceactive additives, such as anti-wear additives and rust inhibitors, compete for space on the metal surfaces in a gearbox,” explains Hennigan. “It is a delicate balance to formulate an oil so that both of these additives are present in correct amounts to adequately protect a machine’s elements from wear and rust.

Top treating can lead to different ratios or different types of these additives, which can disturb the intended balance of the formulation.”

An often-overlooked component of top treating oils with additives is that it can lead to safety challenges, points out Hennigan. “Every time you top treat, you’re interacting with equipment. And, more frequent equipment interaction increases the potential for safety issues.”

After all, for every maintenance check or oil change, a wind technician must climb up-tower and risk exposure to heights and a high-powered machine.

For Hennigan, these risks far outweigh the benefits of a quick-fix maintenance plan. “Instead, the key to long-term lubricant performance is to start with a well-formulated oil that can perform at a high level over many years without need for additive top treating.” This means choosing an oil formulation with the right mix of advanced base oils and additives. Of course, many factors can impact this choice and oil life in service, such as a turbine’s typical operating conditions, severe environmental conditions, and overall maintenance practices.

“But to provide turbine operators with a sense of baseline performance, some of our synthetic wind-turbine oils are

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warrantied for up to seven years, demonstrating the capability for the fluid to protect the machine even after 60,000 hours in service,” he says.

The bottom line: oils with a balanced formulation will last longer, in some cases years longer, so top treating will be a waste of time. “With the right formula, you will not need to top treat the oil to deliver the expected level of performance,” says Hennigan. “Most importantly, it will result in less frequent equipment interaction, improved operational safety, as well as minimized risk of accidentally introducing insoluble contaminants into your lubricants when conducting a top-treat service.”

The diagram compares the performance of different wind-turbine gearbox oils. The red line represents the performance benefits that a high-quality synthetic oil with a balanced formulation can deliver, especially in the key areas of oxidative stability and filterability.

(Photo credit: ExxonMobil)

By Michelle Froese, Senior editor WPE&D

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LOGISTICS

LOGISTICS

What are the considerations when planning for transportation & logistics?

PLANNING A WIND FARM is no easy task. After the site is secured and permitting complete, the wind farm must be designed and turbines selected and then transported for construction. While some developers may source local parts where available, typically many turbine components (think gearboxes, bearings, generators, blades, and others) are ordered from multiple locations. For shipments of that size and complexity, planning and logistics becomes a vital part of project management.

“There are many facets to the wind industry especially at the supply-chain level,” says Jarl Pedersen, Chief Commercial Officer at the Port of Corpus Christi, the fifth largest port in total tonnage in the United States. It provides access to the Gulf of Mexico and the entire U.S. inland waterway system.

“We see a lot of global sourcing and receive towers from Asia, blades from Europe, and so on. A port can help facilitate the communication between developers and suppliers, including the transportation and logistics companies.”

Pedersen says that much like planning a wind farm, it is just as important for developers to do their homework when it comes to delivering their assets to site. “One of the logistical challenges with moving today’s wind-related cargo is that components are getting larger and blades longer. Of course, all projects are different but you really have to plan appropriately because time and diligence are key in the wind industry,” he says.

Case in point: the production tax credit. One of the ways developers can qualify for the recently renewed PTC is to meet the 5% safe harbor requirement and purchase wind turbines before the end of 2016. “We have numerous letdown and storage areas because if you can get your components into the U.S. before the end of the year, you’re in the clear even if you have not yet broke ground at your wind site,” says Pedersen. “In other cases, a developer might have a contract with a supplier for a set number of turbines and need to store them for future projects. But all of this takes operational flexibility and planning ahead.”

Turbine blades used for utility-scale wind farms are now typically well over 100-ft long, which means transporting them to site is no easy feat. A well-planned transportation and logistics plan is a must to ensure components arrive at their final destination intact and unscathed.

(Photo: Port of Corpus Christi)

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He says you also have to consider different state regulations and suggests using a logistics company to help with the process. “At Corpus Christi, we are a selfgoverning body and a sub-division of the state of Texas so, in many ways, we have an advantage of creating many of own rules, but this is not the case with all ports.”

For example, if you are thinking ahead for the slow but surely growing offshore wind market, height restrictions may come into play. “Onshore tower sections are transported horizontally, but the offshore concept is to erect turbines vertically and, considering the size of those towers, you have to consider height restrictions during transport,” says Pedersen. Only the inner harbor at Corpus Christ has height restrictions of 128 feet. “But we’re getting a bridge that will move this to 205 feet.”

He encourages wind developers or manufacturers to visit the port — or truck, train, or vessel company — to ensure the method of transport (or storage) chosen meets the component measurements and project schedule. “The movement of large-scale turbine components is not done easily. A lot of people, from site planners, logistics companies to stevedores and others, come together to make it happen.”

Ian Baylis of Seacat Services, an offshore energy support vessel operator in the UK, agrees and says that to meet the growing offshore wind industry, it is important to work together. “In the early days, crew transfer, personnel, ports, and logistics were all distinct and separate areas. However as the offshore wind industry has evolved in the UK, developers are taking a more holistic look at how these services are procured.”

The U.S.’s Rhode Island Fast Ferry has already demonstrated this in action. The company consulted Seacat Services before construction of the country’s first purpose-built Wind Farm Support Vessel, which serviced America’s first offshore wind farm off Block Island, RI. “There are certainly opportunities to collaborate throughout the supply chain, so it important to develop positive working relationships with complimentary operators,” says Baylis. He says that this will enable the wind industry to streamline its procurement processes.

Plus, you never know when you might need that connection later to help navigate O&M crew to a wind site for turbine maintenance or repairs.

“By developers, operators, and crew sharing their experiences, tasks, and operations while working on a site, it is possible to promote the best global logistics and offshore wind practices, and create future cost savings for the wind industry,” says Baylis.

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SEALS

SEALS

What criteria should be considered when selecting seals for wind turbines?

A WELL-SEALED wind turbine is a longer working wind turbine. Without proper seals, weather and windcarried debris can invade a nacelle and cause problems.

Temperature extremes, for instance, expand and contract air in gearboxes and other lubricated equipment. Dropping temperatures let enclosures pull in dirt and moisture. And for turbines offshore and on, rain and sea spray can cause corrosion problems.

“Seals play a critical role in the operation of wind turbines, whether it is insulating components against the elements, or preventing oils and lubricants from leaking out of a system,” says Jim Harty, A Bal Seal springGlobal Market energized seal used in pitch-drive gear helps Manager Energy protect the bearing by for Bal Seal keeping debris out and Engineering. “But clean lubricants in. with a number of products on the market, selecting the right seals can be a challenge.”

Because seals can have major effects on the duration between the repair of turbine components, such as gearboxes and generators, Harty says it is important to consider materials that offer a proven ability to last and withstand harsh conditions. Seals also need to facilitate a certain level of mobility — just consider the millions of times blades rotate — while resisting continuous wear.

“Low-friction sealing materials, such as a polymer-filled polytetrafluoroethylene, or PTFE, can minimize wear and provide excellent sealing performance and a low-dynamic coefficient of friction,” says Harty. “An energized seal, one containing a component that exerts a measured force, will ensure that the lip retains an ability to contact the housing, while securely and consistently sealing around the edges.”

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For proper protection, it is also important to choose a sealing material that exhibits chemical compatibility with the greases and lubricants commonly used in the turbine. Harty points out that PTFE is chemically inert and offers high resistance to solvents, chemicals, and other materials over time. “By contrast, materials, such as elastomers found in some seals, struggle with long-term exposure to UV rays.”

Machined seals can also withstand much harsher conditions than welded ones, increasing service life of the seal and minimizing turbine downtime for maintenance or repairs.

“Machined largediameter seals have no weld and no hard spots or areas of potential weakness.

This results in an ability to provide consistent contact pressures along the entire diameter of the sealing lip,” says Harty.

In areas where ambient heat is excessive, such as in a turbine’s gearbox, it is essential to use seals that provide protection and thermal stability if these components are to last. Ideally, seals should withstand high and low temperatures (up to 140°F and as low as to -65°F) without compromising the sealing contact stress.

“Minimizing the need for repairs or replacements of a seal means fewer maintenance visits,” says Harty. “Plus, the design of a seal and the choice of material used will affect its shelf life.”

The length of time that seals can be stored often depends on the material. For example, materials such as PTFE can be stored for years without impacting their sealing performance.

“Longevity is an essential turbine design consideration, and this holds true for all of wind turbine components — even seals,” he says.

By Michelle Froese Senior editor WPE&D

WINDPOWER ENGINEERING & DEVELOPMENT — 2017 RENEWABLE ENERGY HANDBOOK

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WINDPOWER

SEALS

TIPS FOR CONNECTING TURBINE COMPONENTS Much like the requirements for proper sealing, connecting wind-turbine parts deserves special consideration for the best and safest results.

Connecting presents specific conditions inside the small confines of a turbine nacelle. Tight spaces can make it difficult to achieve adequate torque and high vibrations can loosen cables. In a worstcase scenario, this can lead to increased turbine temperatures, rising heat, and potentially hazardous conditions.

•

•

• A canted coil spring in a slip-ring application is located inside a turbine’s generator, near the back of the nacelle. A Bal Spring ensures electrical contact over varying thermal expansion conditions by compensating for misalignment caused by thermal expansion.

When choosing connectors, consider these characteristics:

•

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Latching and locking forces. Connectors should provide wind-turbine engineers with a means of dictating forces with which connections are made and broken. Fasteners, such as canted coil springs, offer controllable mating and un-mating forces. Such controlled forces make it easy to connect and disconnect control, and provide an alternative to traditional technologies, such as threaded connections that require tools.

Conductivity. In wind systems, it’s necessary to “dial in” the current-carrying capacity based on application need by specifying physical properties of contact (e.g., type of plating and wire diameter). Although copper braids are typically used to carry current, other options, such as canted coil springs placed on each end of a rod, can improve current transmission.

Because the spring maintains consistent contact forces on the conducting element, it can ultimately improve turbine performance.

Heat safe. Connectors should allow maximum current management with minimal heat buildup in the turbine. Capacitors, transformers, generators, electrical controls, and transmission equipment are all subject to fire. To minimize risk in wind turbines, operating temperatures must remain at a minimum. Typical requirements include a heat run during which the heat rise can be no more than 63°C. Operating temperatures should not exceed 110°C at 2900 A CC [amps of constant current]. The short circuit current (SCC) must be able to withstand 1.6 kVA for two seconds. Canted coil springs help minimize heat-to-current carrying capacity in high-temperature conditions.

Compression resistance. It is important to ensure connectors in wind turbines are resistant to compression set, which refers to the permanent deformation of a material after release of stress or force. They should comprise of material with physical properties that provide consistent, multi-point contact for maximum efficiency of current flow. A resistance to compression set provides for consistent service over thousands of cycles.

By Jim Harty, Global Market Manager Energy Bal Seal Engineering

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SOLAR BASICS

SOLAR BASICS What does the current U.S. solar market look like?

The U.S. solar industry now has more than 22,700 MW of cumulative solar electric capacity in operation, enough to power more than 4.6 million American homes, according to SEIA. The first half of 2015 brought more than 135,000 installations with a new project being installed about every two minutes. Since the implementation of the federal investment tax credit (ITC) in 2006, the cost to install solar has dropped by more than 73%. Since 2010, residential costs have dropped by 45%, and over the past three years the average price of a commercial PV installation has dropped by nearly 30%.

Nearly two-thirds of the market over the past few years has been represented by utility-scale solar, a trend that is likely to continue since many more projects are currently under construction. In the beginning of 2016, the United States reached 1 million solar installations and is expected to reach 2 million within the next two years. By the end of 2016, the U.S. solar industry is expected to install 14.5 GW of capacity, nearly double the capacity installed in 2015.

What are some new solar applications being developed?

Floating solar is one of the most promising new applications being developed in the solar industry.

The biggest draw for floating solar is its potential to create solar-friendly real estate from standing bodies of water. Some ideal sites for floating solar installations are wastewater ponds at water treatment facilities and chemical plants, irrigation ponds at farms or vineyards, quarry lakes or large storage reservoirs behind dams.

Not only is floating solar an optimal solution for conserving land space, but it is cost-effective compared with other energy sources since lease payments for underused bodies of water are lower than land lease payments. It also provides unique environmental benefits. Dry regions like California can benefit from the shade the panels provide because it significantly reduces the amount of water evaporation taking place. Additionally, the shade hinders photosynthesis, resulting in less algae growth on the waterâ&#x20AC;&#x2122;s surface and improving water quality. Since the panels are naturally cooled, they exhibit improved power production.

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By Emily Wild, SPW research assistant

There are currently projects in various stages of development throughout California, Arizona, Texas, New Jersey, Mexico, Brazil, France, Japan and Australia.

What are some of the main financial advantages of going solar?

With federal credits, rebates and state tax credits, the average customer only pays 50% of the total cost for a solar installation, according to EnergySage. However, net costs can vary greatly depending on what incentives are available in a specific geographic area. Solar homes will typically have free electricity for 25 to 35 years with actual savings increasing each year because upsurges in utility rates will be avoided.

Customers who live in states with markets for solar renewable energy certificates (SRECs) may be able to generate additional income by selling the SRECs that the solar panel system generates back to the state.

Another area where going solar can provide financial benefits is in the overall value of the home. As long as the solar panel system is bought rather than leased, the home has the potential to sell at a premium that oftentimes pays back more than the initial cost of the system. According to a Lawrence Berkeley National Laboratory 2015 report, solar PV systems can add an average of $3.78/watt to a home sale price, which is equivalent to adding $22,680 to the cost of a home for a standard 6-kW system.

REC floating PV installation in Indonesia.

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SOLARPOWER A solar panel payback period is an estimation for how long it will take customers to break even with the total cost of their solar energy investment. This calculation takes into account components including the gross cost of the solar panel system, the value of up-front financial incentives, average monthly electric use, estimated electricity generation and additional financial incentives. It is difficult to find an average payback period since many factors are considered, but the range is usually somewhere between three and 15 years. There are many online calculators available to help customers determine their specific payback period.

How does a state’s solar policy affect their solar development? How does Congress’ renewal of the renewable investment tax credit affect the solar industry?

Some states, like Florida, Oklahoma, Texas, Virginia and others, maintain policies that discourage the development of distributed solar. Poor state policy can be a result of not having a renewable portfolio standard (RPS); having an RPS with a low, outdated solar target; having an inadequate statewide net metering policy; lacking strong interconnection laws; and/or having few established community solar programs. Other factors that provide barriers to distributed solar are the prohibition of third-party sales and burdensome taxes on solar and solar leasing. Florida is a state that is taking action against these codes by demonstrating efforts to remove these taxes and lower the cost of solar.

The U.S. Congress recently agreed on a bill that extends the solar investment tax credit (ITC) by five additional years. The ITC will be extended from December 31, 2016, and decreased from 30% to 10% until 2024. Projects that begin construction by 2019 will receive the current 30% ITC, while projects that begin construction in 2020 and 2021 will receive 26% and 22% respectively, according to IHS. All projects must be completed by 2024 to receive these elevated ITC rates.

2017 RENEWABLE ENERGY HANDBOOK

As a result of the extension, the solar industry is expected to add 220,000 new jobs by 2020. It is also forecasted that clean solar energy will cut emissions by 100 million metric tons and more than $133 billion in new, private sector investments will be generated. Before the extension, the solar industry faced pressure to complete projects by the end of 2016. With the extension now in place, the number of completed projects is expected to peak in 2020 and 2023, while the extension of tax credits for residential PV enables steady growth of this segment through 2022.

Why is storage important to the growth of solar?

In the past, the majority of storage usage was in the off-grid market; however, storage is now being used to back up gridconnected projects. If PV systems are expected to replace existing energy sources, it is crucial that storage be used. GTM Research expects significant growth in the U.S. storage market over the next five years across residential, non-residential and utility markets, resulting in a 2,081 MW annual market by 2021.

This is nine times the size of the 2015 market. The behind-themeter sector is expected to account for an ever-larger share of total storage MW deployed each year through 2021, up from 15% in 2015 to 49% by 2021.

Energy storage can be deployed in most PV markets today, including residential, commercial and utility segments. It can reduce grid power usage at certain peak electricity demand times, which can help drive down customers’ electricity bills, and it can also be used to smooth system output to overcome grid integration challenges in both new solar installations and those that are retrofitted with storage.

The biggest difficulty with solar+storage remains the high cost. However, energy storage is said to be where PV was six or seven years ago, and the factors that led PV to mass affordability will have a similar effect on storage. Battery costs have already begun to decline as a result of dozens of start-up companies, new technologies and safer, more efficient types of inverters and storage options.

Credit: GTM Research solarpowerworldonline.com

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SOLAR BASICS

SolTerra captures solar on the Seattle skyline.

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www.seia.org/research-resources/solar-industry-data www.solarpowerworldonline.com/?s=floating+panels www.energysage.com/solar www.solarpowerworldonline.com/2016/02/u-s-pvinstalls-expected-to-grow-67-this-year-with-help-fromitc-extension/ www.solarpowerworldonline.com/2015/12/solar-itcofficially-extended-through-2021/ www.solarpowerworldonline.com/2016/05/tensunny-states-poor-solar-policies/ www.solarpowerworldonline.com/2015/12/whystorage-is-a-huge-market-opportunity-for-solar/

sources

What is net-metering and how is it affecting solar?

During the day, most residential and commercial customers generate more electricity from solar power than they consume. Net metering allows these customers to sell their excess electricity back to the grid, which reduces their future electric bills. Even though it would generally cost electric utilities less to produce their own electricity, they are still required to buy this excess power. Depending on differences in states’ net-metering regulations, its benefits vary for solar customers in different areas of the country. Since net-metering increases the demand for solar energy systems and allows the industry to thrive, it creates thousands of jobs for installers, electricians and manufacturers. Net metering was originally developed to encourage the introduction of small-scale power sources like rooftop solar panels.

However, there is some conflict surrounding net metering. Some utilities see net-metering policies as lost revenue opportunities. When residential and commercial solar customers sell back their generated electricity to the grid, they avoid paying the utility’s power since they did not use it, but they also avoid paying for all of the fixed costs of the grid. These grid costs then take the form of higher utility bills for customers who do not have distributed energy. Edison Electric Institute is among a large population who argues that net-metering policies should be updated to reflect the decline in solar power production costs.

www.solarpowerworldonline.com/2016/03/enphasefounder-speaks-solar-storage/ www.seia.org/policy/distributed-solar/net-metering www.solarpowerworldonline.com/2016/03/ net-metering-inaction-stalls-500-solar-projectsmassachusetts/ www.eei.org/issuesandpolicy/generation/ NetMetering/Documents/Straight%20Talk%20 About%20Net%20Metering.pdf

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Solar Basics

Editor’s welcome to the solar section Top solar stats and resource map

SOLAR ARTICLES

Silicon Modules .................................................. 70

Thin Film Modules .............................................. 74

Power Optimizers ............................................... 76

Microinverters ..................................................... 78

String Inverters ................................................... 82

Central Inverters ................................................. 90

Flat Roof Racking & Mounting ............................ 92

Sloped Roof Racking & Mounting ...................... 95

Rail-less Mounts .................................................. 98

Grount Mounts ................................................. 102

Carports ............................................................ 106 Trackers ............................................................. 108 Cables ............................................................... 112 Pyranometers .................................................... 116

Batteries & Storage .......................................... 118

Software ............................................................ 121

Site Assessment ................................................ 122

Distribution ....................................................... 124

Operations & Maintinence ............................... 126

Construction, Installation & Development ....... 130

Safety ................................................................ 133

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, IT S THRIVING solar is here and

WE MAY PERSONIFY a broken record when we say, “Now is a great time to get involved with solar.” But the statement holds true every year. Even as we were hesitant to make that pitch last year—with the uncertainty surrounding the investment tax credit (ITC) renewal and the expected 8-GW drop in projects if tax credits were reduced—solar pulled through. Just before the 2015 holiday season, the U.S. Congress agreed on a bill that extends the ITC by five additional years. The industry was immediately forecasted to grow 116% in 2016 because of the extension. It remains a great time to be involved in solar.

The ITC extension “breathes new life into the U.S. solar industry,” said analysts at IHS Markit. Manufacturers, developers and even those wary about getting involved with the U.S. market have pushed forward. Installation growth is off the charts.

It took us 40 years to hit 1 million U.S. solar installations (which was celebrated in May this year).

But the exploding growth of solar is evident in forecasts that expect us to reach another million installations just within the next two years. As SEIA interim president Tom Kimbis said, “The solar industry is growing at warp speed, driven by the fact that solar is one of the lowest cost options for electricity, and it’s being embraced by people who both care about the environment and want access to affordable and reliable electricity.”

Solar accounted

for 26% of all new electric generating capacity brought online in the United States in the first half of 2016. This summer was the first for California to use more electricity from renewables than from natural gas. The U.S. Energy Information Administration expects 2016 to be the first year in which utility-scale solar additions to the power grid exceed additions from any other single energy source.

Need more proof the U.S. solar industry is ripe for additional activity? Costs keep dropping and technology advancements make solar more attractive to the masses.

Solar prices are 18% lower than they were a year ago and 63% lower than five years ago. NREL found that overall installation costs have fallen by 6% (residential), 4% (commercial) and 20% (utility) since 2015. A residential system costs, on average, $2.93/watt to install today. Back in the late ’70s when President Jimmy Carter was installing solar on the White House roof, the solar panel alone cost $76/watt. These crazy cost savings made solar a more attractive option when President Barack Obama re-installed a 6.3-kW system on the White House in 2014.

The growth we see now is expected to continue, most definitely through the next five years. GTM Research notes that by 2021, more than 30 states will add more than 100 MW of annual capacity, with 20 of those states becoming home to more than 1 GW of total operating solar PV. When we hit that next ITC step down, the U.S. solar industry will be better prepared for what’s to come, and solar will continue its dominance.

This is the proof that upholds our annual solar-friendly sentiments; it’s a great time to get involved in the market, whether through manufacturing, installing or choosing to put solar on your own roof. Join us in this booming industry! SPW

KELLY PICKEREL SENIOR EDITOR Solar Power World kpickerel@wtwhmedia.com

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united states

SOLAR IRRADIANCE

Provided by:

Note solar irradiance across the country to plan for your next project. The 2016 U.S. solar performance maps show departure from average solar irradiance in GHI (or Global Horizontal Irradiance, the key variable for PV projects) by quarter. Vaisala conducted the study by comparing 2016 data with long-term averaged values from its continually updated global solar dataset.

GHI ANOMALY MAPS QUARTERS 1-3

Q1

Q2 LEGEND Departure from normal [GHI] −10%

0%

10%

Q3

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top solar stats

There’s a lot to consider when selecting a state in which to do solar business. Here’s an easy way to look at which states are excelling in the industry and in what ways.

Top states for 2015 installed capacity California (3,266 MW) North Carolina (1,140 MW) Nevada (409 MW) Massachusetts (340 MW) Arizona (258 MW)

Top utilities by 2015 installed solar megawatt Southern California Edison (California) (1,258 MW) PG&E (California) (787 MW) Duke Energy (North Carolina) (461 MW) SDG&E (California) (441 MW) Los Angeles Dept. of Water and Power (California) (247 MW)

Top cities for total PV capacity through 2015 Los Angeles, California (215 MW) San Diego, California (189 MW) Phoenix, Arizona (147 MW) Honolulu, Hawaii (146 MW) San Jose, California (141 MW)

Highest 2015 cumulative solar capacity per capita Nevada (429 watts/person) Hawaii (394 watts/person) California (338 watts/person) Arizona (337 watts/person) North Carolina (206 watts/person)

NV

CA

ID

AZ

Most solar watts per customer by utilities in 2015 Village of Minster (Ohio) (2,104 watts/customer) Dominion North Carolina Power (1,946 watts/customer) City of Palo Alto Utilities (California) (1,846 watts/customer) Carey Municipal Power & Light (Ohio) (1,351 watts/customer) Guam Power Authority (661 watts/customer)

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Provided by:

Solar jobs in 2015 California (75,598) Massachusetts (15,095) Nevada (8,764) New York (8,250) New Jersey (7,071)

Top states by percentage of veteran solar jobs in 2015

Top metros for solar jobs in 2015 Los Angeles, California (21,263) San Francisco, California (15,631) Boston, Massachusetts (10,096) San Diego, California (8,402) Las Vegas (7,644)

Kentucky (19.6%) Louisiana (16.9%) South Carolina (15.7%) Georgia (15.1%) Idaho (13.3%)

NY OH

KY SC

LA

MA NJ

NC

GA

FL

Number of solar companies California (2,754) New York (652) New Jersey (547) Florida (456) Arizona (452)

Info from: The Solar Foundation, SEIA, GTM Research, SEPA, Environment America Research & Policy Center

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SILICON MODULES

SILICON MODULES What is PERC? Why should you care?

THERE HAS BEEN a lot of buzz about PERC solar cell technology, especially over the past year, with manufacturers large and small touting it. Here are the basics on this still-new technology and why PERC matters to the different players in the solar PV market.

WHAT â&#x20AC;&#x2122;S PERC? Depending on which source is consulted, PERC stands for Passivated Emitter Rear Cell, Passivated Emitter Rear Contact or even Passivated Emitter and Rear Cell.

First developed in Australia in the 1980s by scientist Martin Green and his team at University of New South Wales, PERC technology adds an extra layer to the rearside of a silicon solar cell. Manufacturers spent many years focusing on the front side of a solar cell, and less attention was paid to taking advantage of production opportunities from the backside. Incorporating PERC into a solar cell boosts generation.

In order to create a PERC cell, an additional two steps are employed to the standard back surface field (BSF) during the manufacturing process. First, a rear surface passivation film is applied. Second, lasers or chemicals are used to open the rear passivation stack and create tiny pockets in the film to absorb more light. Manufacturers can approach this in different ways (i.e. varying the recipe for the film and opening technique), but in every instance a dielectric passivation layer is added to the back of the cell.

In employing just two additional steps, the return is threefold: 1.) Electron recombination is significantly reduced; 2.) More light is absorbed; and 3.) Higher internal reflectivity is experienced.

Not all sunlight is absorbed through non-PERC solar cells (some light passes straight through). But with a passivation layer on the rear side of a PERC cell, unabsorbed light is reflected by the additional layer back to the solar cell for a second absorption attempt. This process leads to a more efficient solar cell. This is great news for those across the spectrum of the industry.

PERC explained (Credit: SolarTech Universal)

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2017 RENEWABLE ENERGY HANDBOOK

WHY D O SOLAR CELL AN D PAN EL MAN UFAC T U R ER S C A R E? The investment to move to a PERC technology line requires minimal modifications to existing cell manufacturing lines.

Manufacturers can easily make the jump to produce a superior product without having to outlay large capital expenditures for a complete overhaul of existing equipment. There has been a boom in adding PERC capacity to the global market and it is set to continue at a rapid pace for the next several years.

Additionally, panel manufacturers are now able to produce a more energy dense module without much of an increase in build cost.

WHY D O D EVELOPERS, DESI GN ERS AN D I N STA L L ER S C A R E? Panels incorporating PERC technology give more freedom to developers and designers, especially when dealing with unorthodox spaces or locations that were once thought to be less than desirable for solar. PERC panels have a higher energy density per square foot and perform well under low-light conditions and high temperatures. When considering total

energy production rather than peak wattage, it is clear PERC panels are superior. Designers can utilize fewer panels to accomplish total output goals where footprint is limited, or they can dramatically maximize energy output if space is not a premium. It empowers designers to be more flexible and responsive to project objectives.

This freedom also allows the option to drive down balance of system (BOS) costs. More is being achieved with less, which can trickle down to significantly reduced soft costs. This can be the difference between a client having sticker shock and not moving forward with project to one seeing a cost-effective and manageable system. Additionally, more

THE NEW SUPER POWER Introducing the new HIT® BLACK Series solar panel from Panasonic. The N320K throws a shadow on the competition with its 19.1% module efficiency that produces 23% more power than conventional 60-cell modules. And when the mercury rises, we don’t miss a beat with a surprisingly low temperature coefficient of -0.29%/°C that churns out power even at high temperatures. Featuring a sleek, all-black design, the new N320K looks as good as it performs and blends in nicely with any roof color.

Let’s get you on the team. Become a Panasonic Authorized Solar Installer and gain priority access to financing, qualified leads, training and co-op marketing funds, and much more... Learn more at Business.Panasonic.com/SolarPanels.

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SILICON MODULES

By Gena Gustin, sales with SolarTech Universal attractive temperature coefficients make PERC a top performer in hotter climates, and less thermal loss is experienced. This allows end users to achieve superior performance from their systems throughout the year.

W H Y DO F I NA NC I E R S C A R E ?

The Future is Now

ENERGY FOR A BETTER WORLD

German Engineered High-Performance Solar Modules

Being that PERC technology is neither new or radically different from standard cells, there is reduced risk on the financier’s side of the table to back an advanced technology. By utilizing a proven technology and modifying the standard cell, there is no change in the inherent risk of the module and its performance. Financiers should warm to the idea of panels manufactured with PERC technology.

It sets a course for establishing dependable, long-term power output in a cost-effective manner for residential, commercial and utility projects. Total power generation over the lifetime of the solar system is increased without dramatically boosting the cost per watt.

A SolarTech Universal panel that incorporates PERC technology.

(Credit: SolarTech Universal)

- AXIpower 60/72 cells Rooftop or Ground Mount 260 – 320W, Polycrystalline - AXIblackpremium Superior Aesthetics Meets Performance 270 – 280W, Monocrystalline - AXIplus SE Smart Module Solution 270W, Optimizer Technology AXITEC, LLC, 75 Twinbridge Drive, Suite E, Pennsauken, NJ 08110, Phone 856-813-9386, info@axitecsolar.com 72

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THIN-FILM MODULES

THIN-FILM MODULES What are the advantages of flexible thin-film solar modules?

THE FLEXIBLE AND LIGHTWEIGHT solar modules of today have efficiencies that rival that of traditional rigid silicon panels, while their flexible format and non-penetrating peeland-stick installation make them ideal for a wide variety of applications unsuitable for heavy silicon panels.

Flexible thin-film solar has been around for a number of years. The first generation flexible thin-film PV modules were developed around amorphous silicon (a-Si), a noncrystalline form of silicon. The early generation a-Si thin-film modules, while lightweight and flexible, provided a low power output—only about 5 to 6% power efficiency— meaning only 5 to 6% of the sun’s energy was converted into electricity. The result was very low power density, requiring a large area to produce a power output equal to that of crystalline silicon modules. Even with the low power output, a-Si modules were popular because the peel-andstick adhesive application did not require racking assembly, ballast or roof penetrations. To solar installers, this meant an easier installation with a faster learning curve. Labor costs were also lower because project staging, loading and installation could be completed faster with fewer workers than with conventional rack-mounted glass modules.

The next generation flexible thin-film PV modules to enter the marketplace were built using copper-indiumgallium-selenide (CIGS) thin-film PV technology. These new flexible CIGS modules offered the same benefits as a-Si— lightweight, flexible, peel-and-stick application—at a much higher power efficiency (MiaSolé’s FLEX line of flexible CIGS thin-film modules reaches efficiencies exceeding 16%).

Flexible solar modules are ideal for membrane roofs, including TPO and EPDM low-slope roof systems. Because these thin-film modules can weigh as little as 7-oz per sq. ft, they can be installed over low-load-capacity roofs that prove challenging for conventional crystalline panels and rack systems because the roofs can’t support the added weight. Today’s flexible modules use a factory-applied butylbased self-adhesive with a 30-year proven performance history. Installed with this simple peel-and-stick adhesive,

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flexible modules become an integrated part of the roof system and have the same wind uplift and seismic performance characteristics of the roof system itself.

From an installer perspective, without racks to assemble, ballast to carry and place, or leakcausing roof penetrations, peel-and-stick thinfilm modules are the simplest, fastest and lowest labor cost rooftop solar solution.

Some flexible modules are also designed for architectural standing seam metal roofs, where the module can be adhered directly to the metal roof surface in between the raised seams. The result is an aesthetically pleasing solar roof that doesn’t have obtrusive racks mounted to the outside of the metal seams that detract from a clean, streamlined look.

The benefits of thin-film modules extend well beyond roofing. Lightweight and flexible modules with no-penetrationinstallation enable solar power generation in a wide variety of non-roofing applications. A good example is landfills. Flexible modules with a large format make PV landfill installations over geo-membranes both practical and cost-effective compared to traditional Subtitle D closures and ballasted crystalline rack systems. Large-scale geo-membrane panels can be factoryassembled with flexible solar modules laminated directly onto the geo-membrane surface. Then the combined solar membrane package can be rolled up and transported to the landfill site. This greatly speeds up installation time while reducing labor costs, especially on state and county projects that require Davis-Bacon wages to be paid on site. Often the cost savings of using the geo-membrane compared to a full Subtitle D closure alone can offset a significant percentage of the solar cost.

Transportation is another market in which flexible and lightweight thin-film modules provide significant advantages. Federal and state regulations limit how long buses and largehaul tractor-trailer rigs can idle in place.

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The MiaSolé FLEX-02N line of modules is rated between 115 and 130 watts. (Credit: MiaSolé)

2017 RENEWABLE ENERGY HANDBOOK

Applying flexible thin-film solar modules to a bus or trailer roof, coupled with onboard power generation integrated with additional battery storage and an off-grid inverter, means tractor-trailer rigs can power the driver cabin during mandated sleep/rest overs without idling the engine.

Solar power can also be used to offset refrigeration power for cold storage trailers.

Flexible thin-film modules can also be applied to bus rooftops, so that when the vehicles are idling, solar power can heat and cool the bus while powering accessories such as Wi-Fi, power plug-ins and refrigeration units, all without burning fuel. In the personal RV sector, rooftop solar can reduce engine and generator runtime. For both commercial and recreational use, flexible and lightweight thin-film solar modules make a serious reduction in vehicle fuel cost while reducing air pollution and achieving a fast payback.

Flexible thin-film solar modules can also be used in many other applications, such as floating solar reservoir covers and large canal waterway solar covers. These covers help reduce water losses due to evaporation, and once solar modules are

installed they can also provide renewable energy to process and move water.

Floating covers built with flexible polymer membranes and lightweight support structures provide a low-cost option compared to using heavy glass solar modules with large structural supports and flotation components. Tension fabric using cables or lightweight space-framing structures can span across water and irrigation canals. On large steel water towers, flexible solar modules can bond directly to the steel tank providing solar power to pump water for storage while a battery backup can provide emergency power in the event utility power is lost.

The technical achievements of CIGS result in high efficiencies when added to non-penetrating, peel-and-stick installations, and their flexible format make them ideal for a wide variety of applications unsuitable for heavy silicon panels. Flexible thin-film solar modules increase the number of surfaces that can be used to provide solar energy generation, providing more opportunities for renewable, clean energy, helping move the bar forward to a carbonneutral future.

The MiaSolé FLEX-02W module is 39.3 in. by 102.3 in. and is rated at 360 watts. (Credit: MiaSolé)

By Michael Gumm, application technologist, MiaSolé

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POWER OPTIMIZERS

POWER OPTIMIZERS What are the advantages of a DC-coupled solar storage system?

BATTERIES CAN ONLY STORE ENERGY in its direct current (DC) form so the very essences of energy storage is DC. The reason that DC lends itself to being storable is because it has a unidirectional flow. A graphical representation of this would be a straight horizontal line. However, energy that is expressed in alternating currents (AC) has an electric charge flow that changes direction.

This is depicted as a sine wave in a graph. Trying to store energy in its AC form would be like trying to capture a wave–it’s impossible.

Knowing that the battery is limited to DC energy and that solar modules produce in DC, it becomes obvious that the rest of the storage hardware should also be in DC. This is because each time that there is a conversion from AC to DC or vice versa, there is some amount of energy loss. But when PV power is stored directly in the battery in its DC form, there are no additional conversions from AC to DC and then back again to AC for use in the home or export to the grid. This means that a DC-coupled solution allows for higher system efficiency because there will only be one total conversion.

Beside minimizing the initial energy losses, there are other benefits to a DC-coupled storage system. First of all, a DC-coupled system can be implemented with only one inverter, which initially means simpler installation. Also, having one inverter managing the system makes it easier to coordinate advanced functionalities that are required in some locations, rather than trying to synchronize and coordinate these functions between two different inverters in an AC-coupled solution.

A DC-coupled solution also allows using PV power above the inverter rating, while an AC coupled system will not. For instance, in some locations there is a limitiation on the size of the inverter.

So, if the inverter size is limited to 8 kW, with an AC-coupled system this would include both the PV inverter and the inverter for the battery. This means that an 8-kW, AC-coupled system would only be able to accomodate a 4-kW inverter for PV and a 4-kW inverter for storage–thus limiting the PV system to only 4 kW. But with a DC-coupled system, the 8-kW limitation would be allocated to only one inverter, thus allowing a larger PV system and greater battery charge/discharge capability.

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Additionally, a DC-coupled system is able to route more energy to the battery because the energy flow is not limited by the inverter capacity. This is because the energy is routed directly to the battery without needing to go through any conversion. However, in an AC system, the inverter acts as a bottleneck for energy flow. As an example, in a PV system that has a 10-kW production but a 7.6-kW inverter, the energy to the grid and the AC-coupled battery would be limited to 7.6 kW. This means that potential energy would simply be lost. However, with a DC-coupled system the 7.6 kW would be routed through the inverter to the grid and the additional 2.4 kW would be sent directly the battery, without needing to pass through the inverter. Because the inverter does not limit power in an DC-coupled system, system owners are able to increase energy production, which leads to improved ROI. DC-coupled solutions are also beneficial for backup storage systems. When an inverter is in backup mode because the grid is temporarily down, the inverter may try to power the backed-up loads with energy from both the battery and PV. When this is done in DC-coupled solution, the energy only needs to be drawn from a single inverter.

But with an AC coupled system, the two or more inverters will require complicated syncronization. While at first look, it might seem that an AC-coupled system would split the burden up between the two inverters and potentially lighten the load of each, but it actually makes the energy management to be more complicated and can cause the energy production and storage to be decreased.

By Lior Handelsman, VP of marketing & product strategy and founder of SolarEdge solarpowerworldonline.com

12/16/16 2:29 PM

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SOLARPOWER

MICROINVERTERS

MICROINVERTERS

What are the advantages of microinverters going into 2017?

MICROINVERTERS are driving sales in the MLPE segment to year-over-year highs. These powerful little boxes are the hot technology for both residential and commercial solar.

Their popularity starts with solar harvest, safety and ease of installation when compared to string and even optimizer systems.

The first advantage lies in module-level harvest and tracking, a distinct advantage over conventional string systems. Particularly in any environment where shading poses a challenge–such as in a moderately-treed suburban neighborhood, or an urban setting with tall surrounding buildings– microinverters’ ability to independently serve and monitor the performance of each individual panel ensures maximum harvest throughout the day.

Meanwhile, a single shadow or even debris would reduce output across an entire string.

This distributed harvest also means there’s no single potential point of failure in the array. Even if one component goes down, the rest of the array will still function at top power. Compare that to a string system in which, again, a single technical issue can sideline whole groups of modules.

Another often overlooked point of distinction for microinverters is low-light performance. With a lower startup voltage than string systems, microinverter arrays will begin producing energy earlier in the day, and stretch that production deeper into twilight—built-in optimization that matches technology with the diurnal cycle, wherever you might live.

IHS SAYS MICROINVERTERS AND OPTIMIZERS TO SHIFT TO INTEGRATED AC AND SMART MODULES The business model of microinverter and power optimizer suppliers is set to shift from standalone units to integrated systems, such as Smart and AC modules, according to new analysis released last November by IHS Markit.

The annual IHS Technology PV Microinverter and Power Optimizer Report examines market size, pricing and vendor market share. It forecasts revenue for Smart and AC modules will jump from under $100 million in 2015 to almost $500 million by 2020.

“Suppliers are shifting their business model from selling stand-alone products to selling an off-the-shelf integrated model,” said Cormac Gilligan, research manager at IHS Technology. “This will help them capture new emerging markets, improve sales channel efficiencies and lower customer costs.

Microinverters and power optimizers will increasingly be installed in the factory in the form of AC and Smart Modules, the IHS Technology report said.

The growth of the smart home technology market may provide an opportunity for Module Level Power Electronic (MLPE) suppliers to enter new markets and extend their partnership networks, according to the IHS Technology report.

“Policies and standards will be a significant driver of MLPE adoption and associated module integrated solutions over the next five years, particularly in the United States,” said Camron Barati, solar analyst at IHS Technology. “The 2017 update to the United States National Electric Code will standardize safety requirement applications in state markets. This will ultimately incentivize the use of microinverters and power optimizers for rooftop applications. Technology giants such as Apple, Google, Amazon, Huawei, AT&T and Comcast also provide solutions for the smart home market and, therefore, opportunities for MLPE suppliers to engage with wider audiences.”

This information was pulled from a press release distributed by IHS in November 2016.

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’

rs e l l a st

e c i o ch

n

i The

#2 microinverter supplier globally – we work harder for you APsystems microinverters serve multiple modules—cutting installation time by 50% or more over competing brands Built-in safety with rapid shutdown and DC arc-fault protection features New in 2016: YC500i with EnergyMaxTM, developed to harness the power of today’s high-output PV modules ECU Gateway with integrated Wi-Fi for easy set up and lower installation costs

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MICROINVERTERS

Microinverters are also extremely safe by design—a paramount concern under evolving NEC standards meant to protect homeowners, emergency responders and others who may venture onto the roof. For example, when an AC circuit goes down for any reason, each unit in a microinverter array performs its own rapid shutdown function in just 100 milliseconds. That’s 100 times faster than the current codespecified standard of ten seconds for shutdown. System voltage at shutdown is about 30 Vdc, meeting stringent NEC requirements, and well below the 80-V threshold generally considered safe for contact.

There’s no high-voltage DC running across the roof with a microinverter array. Also, any low-voltage lines present will be located beneath solar modules, eliminating the chance of contact during rooftop activity. This safety by design makes microinverters essentially “future proof,” not only meeting today’s stringent codes, but anticipating and easily programmed to meet tomorrow’s.

Microinverters are also making strides in the growing arena of storage. For example, APsystems has teamed up with Sensata and their Magnum Energy brand to offer an integrated microinverter-and-battery charger/controller package, extending MLPE’s market reach to this dynamic new segment.

MLPEs have come a long way since the first generation products many years ago. The new generation of microinverters are producing more power than ever before.

Meeting the latest regulatory standards, they have shown their reliability in challenging environments, extreme temperature ranges and in every conceivable application on each continent.

Microinverters continue to be one of the fastest-growing segments in the solar industry and will continue to be for years to come.

By: Jason Higginson Senior director of marketing for APsystems

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STRING INVERTERS

STRING INVERTERS Why are string inverters increasingly used in larger projects?

1-MW installation on California Goodyear Rubber Manufacturing Facility by REP Solar with Yaskawa – Solectria Solar inverters.

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SOLARPOWER “STRING INVERTERS are rapidly gaining market share for PV installations lower than 1 MW,” said Cormac Gilligan, research manager – PV inverters at IHS Technology. According to IHS Technology’s PV Inverter Market Tracker Q4 2015, threephase, low-power (less than 99 kW) inverters accounted for about 15% of total shipments to utility-scale projects in 2015.

IHS estimates that shipments of this power class will reach 30GW by 2019.

“There are many reasons why string inverters are replacing central inverters for increasingly larger projects,” said Emily Hwang, Yaskawa – Solectria Solar’s senior applications engineer. “String inverters are getting larger due to market demand driving technological advances. In today’s market, the initial price of installing string inverters is typically more economical than centrals for projects up to a certain size. When the inverter size grows, so does the maximum size of the projects where string inverters work financially.”

Hwang explained that installers are finding financial benefits of string inverters in their ease of installation and replacement, and in the fact that they need less transformers than central inverters and no concrete pad. “For instance, 3 MW of string inverters can be handled by one dual winding transformer,” she said. “Alternatively, accomplishing 3 MW with central inverters would require at least one more

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12/16/16 2:58 PM

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SOLARPOWER

STRING INVERTERS

have utility-powered management features such as low voltage ride through, frequency ride through, curtailment and dynamic power factor control. The cost per watt of string inverters is now comparable to that of central inverters. All of this is making string inverters an increasingly popular choice over central inverters in large projects.”

Gregg said that when choosing a type of inverter, overall the client is trying to achieve the highest return on investment. “It isn’t about technology, it’s about money,” he said. “People want to have the systems with the highest uptime, lowest installed cost and lowest O&M. The most efficient inverters create the highest energy yields, which results in the lowest costs and the easiest O&M.”

expensive three-winding transformer, or multiple transformers.

Also, you don’t need to pour a pad for a string inverter, which creates more space for solar modules and allows installers to squeeze more power and revenue from a site.”

Finally, while central inverters are more customizable and made to order, most manufacturers and distributors have the string inverters in stock, which significantly reduces lead times.

While a few incumbent manufacturers have been leaders in this market, IHS reports more Japanese, Chinese and Western suppliers are expanding their portfolio and entering the U.S. China-based Sungrow is an example. The company showcased two new 1500-Vdc inverters at Solar Power International 2016.

The company’s SG125HV inverter offers 125 kW of capacity in a suitcase-sized cabinet weighing 130 pounds.

“Although central inverters have seen improvements in performance, reliability and efficiency, they have maintained the same standard function,” said Allan Gregg, director of applications engineering at Sungrow, in a Solar Power World webinar. “String inverters, however, have undergone many significant changes. They’ve grown from being single string to having the capacity for up to 16 strings. Some string inverters

By Kathie Zipp, SPW editor

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SOLAR SOLAR 05. Solar REH 17 - String Inverters V4.indd 84

Voc (V) Voc (V)

2.52 3.78 2.52 5.04 3.78 5.04 5.04 5.67 5.04 5.67 5.67 5.67 5.67 6.3 5.67 6.3 6.3 6.3 6.3 6.3 6.3 6.3 6.3 7.56 6.3 7.56 7.56 7.56 7.56 7.56 7.56 7.56 7.56 0.63 7.56 0.63 0.63 1.89 0.63 1.89 1.89 4.7 1.89 4.7 4.7 4.7

Isc (mA) Isc (mA) 50 50 50 50 50 200 50 40 200 50 40 135 50 15 135 25 15 50 25 200 50 1000 200 20 1000 29 20 36 29 40 36 200 40 50 200 50 50 15 50 15 15 4.4 15 4.4 4.4 4.4

Pmax (mW) Pmax (mW) 89.2 133.8 89.2 178 133.8 712 178 162 712 200 162 540 200 67 540 111 67 223 111 890 223 4450 890 108 4450 156.6 108 182 156.6 218 182 1068 218 22.3 1068 22.3 22.3 20.1 22.3 20.1 20.1 12.9 20.1 12.9 12.9 12.9

Vmax (V) Vmax (V) 2 3 24 34 4 4.5 4 4.5 4.5 4.5 4.5 5 4.5 5 55 55 55 56 5 5.8 6 5.9 5.8 6 5.9 6 6 0.5 6 0.5 0.5 1.5 0.5 1.5 1.5 3.4 1.5 3.4 3.4 3.4

Imax (mA) Imax (mA) 44.6 44.6 44.6 44.6 44.6 178 44.6 36 178 44.6 36 120 44.6 13.4 120 22.3 13.4 44.6 22.3 178 44.6 890 178 18 890 27 18 31 27 36 31 178 36 44.6 178 44.6 44.6 13.4 44.6 13.4 13.4 3.8 13.4 3.8 3.8 3.8

Jac (mA/ Jac cm2) (mA/

Fill Factor Fill (%) Factor

Cell Effcy Cell (%) Effcy

42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4 42.4

>70 > 70 >70 >70 >>70 70 >70 >70 >70 >70 >70 >70 >70 >70 >70 >70 >70 >70 >70 >70 >70 >70 >70 >70 >70 >70 >70 >70 >70 >70 >70 > 70 >70 > 70 >>70 70 >>70 70 >70 >60 >70 >60 >60 >60

22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22

42.4 cm2) 42.4

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>70 (%) >70

22 (%) 22

Dimension (mm) Dimension (mm)

43 x 14 x 2 42 x 21x 2 43 x 14 86x 14 xx 22 42 89 xx 21x 55 x22 86xx 21.5 14 x 2x 1.3 44.5 89 62xx55 21xx22 44.5 1.3 58xx21.5 58 x x2.0 62 54xx21 18xx22 5822x x5835x x2.0 2 54 42xx18 35xx22 22 89xx35 67xx22 42 xx35 x2 x2 214.5 131.6 89 22xx67 35xx22 214.5 131.6x 1.6 x2 42.0 xx35.0 22 x 35 38.5 x 32.9x x2 2.0 42.042x x35.0 35 xx21.6 38.590x x32.9 79 xx22.0 42 2 22 xx 35 7 xx1.8 90 2 22 xx 79 7 xx1.8 22 22xx77xx1.8 1.8 22 22xx77xx1.8 1.8 22 22xx77xx1.8 1.8 22 22xx77xx1.8 1.8 22 x 7 x 1.8 22 x 7 x 1.8

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Unit cell Unit size(mm) cell 20 x 6 size(mm) 20 x 6 20 20xx66 x 6x 2 2020 x 12 20Xx 4.8 6 20 20 20 x 12 X 6x 2 20 XX 64.8 18 X3 20 X 6 X 66 1810 X 6xX63 6 XX66 20 x 6x 2 2010 x 12 20 Xx620 120 2010 x 12 x2 x 4.8 120 20 15 Xx 4.8 10 18xX4.8 4.8 15 20Xx4.8 4.8 18xX12 4.8x 2 20 2020x x4.8 6 20 20 x 12 x 6x 2 20 6 xx 66 20 6 xx 66 6 56xx2.4 6 56xx2.4 5 x 2.4 5 x 2.4

Cellsin series Cellsin (cells) series 4 (cells) 6 48 68 89 89 99 9 10 9 10 10 10 10 10 10 10 10 12 10 12 12 12 12 12 12 12 12 1 12 1 13 13 38 38 8 8

Weight (grams) Weight (grams) 2.5 3.5 2.5 5 3.5 18 5 4.5 18 5.5 4.5 12 5.5 2 12 2.5 2 4.5 2.5 20 4.5 110 20 2.5 110 4.5 2.5 4.5 4.5 4.5 4.5 22 4.5 0.5 22 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5

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SOLARPOWER

STRING INVERTERS

WEBINA ALERT

R

LEARN MORE ABOUT STRING INVERTERS

The Solar Power World website (solarpowerworldonline.com) has loads of archived webinars you can watch to learn more about string inverters. Check out these and more online.

The Virtual Central Inverter: Using 1500-Vdc string inverters for utility-scale solar projects At what point do the total installed costs make it wiser to go with central instead of string inverters? New higher output 1,500-Vdc string inverters can be combined and be controlled as a single power conditioning system through a single SCADA interface, creating one point of command and control for the entire group of string inverters. The end result is a solar PV system that can reap the benefits of both string and central inverters. This webinar explains the “Virtual Central Inverter” design concept in deeper detail, an idea which illustrates how string inverters may soon be the ideal choice for utility-scale PV projects of the future.

Battery storage inverter compatibility to PV solar string inverters The addition of a battery storage system can add significant user benefits at both the residential and C&I levels. However, within the inverter manufacturing community its fairly well known that not all PV inverters are capable of AC coupling. Many older generation PV string inverters rely on a grid impedance technique to meet the protective anti-islanding solar array electric utility requirement, which means they either will not or cannot work with the hybrid bi-directional inverter used in the typical battery storage system to provide power during grid outage to charge the batteries. This not always a well understood aspect of making battery storage systems with PV solar arrays. Find out about this issue, what to be aware of and potential solutions in this webinar.

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When string inverters are the right choice: Best practices for utility solar PV plants System designers have continually evaluated the benefits of using string versus central inverters due to the constant evolution of string inverters.

This webinar explains the trade-offs of various system architectures and highlight practices system designers can employ to maximize string inverter performance. Learn about: •

• • • • • •

SOLAR POWER WORLD — 2017 RENEWABLE ENERGY HANDBOOK

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Evolution of string inverters: how new technology and capacity increases have changed system design Pros/cons of string and central inverters: when do string inverters make sense?

Typical system architectures and associated trade-offs Design practices that can maximize string inverter performance Inverter controls and system controls that can meet utility requirements Options for connecting to MV step-up transformers Operation and maintenance

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SOLARPOWER

STRING INVERTERS

LEARN MORE ABOUT STRING INVERTERS (CONTINUED)

Four strategies solar installers can use to reduce soft costs Soft costs represent the most flexible aspect of solar project finance, yet they continue to consume outsize sums of cash—up to 64% of the total project cost, according to the DOE. Fortunately, industry innovators are finding ways to reduce soft costs. View this webinar to learn four such strategies, including: •

• • •

How solar companies can reduce financing costs through standardization and automation technology, particularly in the C&I sector.

How in-depth training reduces installation soft costs.

How creating and maintaining solar opportunities within local communities can reduce soft costs.

How solar software tools, techniques and workflows can accelerate proposal-to-project speed while shrinking costs.

ask a vet

Podcasts interview solar industry professionals who have been around the block.

Hear their insight from years of solar experience.

Visit iTunes or SoundCloud to subscribe, or listen directly from archives at windpowerengineering.com and solarpowerworldonline.com

contractors corner Podcasts feature solar contractors from around the country. See how others are doing business and get ideas to implement into your own.

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solar speaks

Solar Power World’s flagship podcast series, gives you the opportunity to hear from the industry’s biggest newsmakers in their own words.

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REH -17 - String Inverters V4.indd halfSolar horizontal WP&SPW Podcast.indd 10188

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12/19/16 8:04 12/20/16 6:38 AM PM

CENTRAL INVERTERS

CENTRAL INVERTERS

By Kathie Zipp, SPW editor

MORE THREE-PHASE LOW POWER, string, inverters are being used in larger projects. But IHS research shows that central inverters aren’t going anywhere soon, and will still account for more than half of shipments in 2016.

Jani Kangas, ABB’s product line manager for North America, said central inverters are often the best solution to meet the sophisticated needs of utility projects, including the need for customization and control.

“Large power plants are sophisticated in design and function,” Kangas said. “They require specially trained power electronics professionals to install, maintain and service the equipment. Depending on the size of the project and the technical specifications, central inverters tend to offer more customization, control and can be a cost effective solution for larger utility projects.”

Inverters also need to have the technical ability to adapt to changing utility requirements. “Central inverters have more flexibility to offer this grid support, which enables the system to be simpler and easier to control from the utility’s perspective,” Kangas said.

The robustness and modularity of central inverter systems, such as ABB’s PVS980, allow a more sophisticated design to help increase reliability and lower maintenance cost, according 90

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SOLARPOWER Why won’t central solar inverters go away in large commercial/ small utility projects?

to Kangas. “System features like closed-loop cooling elements without moving parts automatically increase the reliability of the total unit,” Kangas said. “Therefore, the better control over the inverter functions and less total amount of components in the power plant, the easier to maintain the reliability.”

Using a central inverter for utility projects also enables site owners to maximize the economies of scale. “If site owners select the right central inverter for their site he can have better control over the units in the field; then you can have a lower number of inverters to use, better plant control and an easier time to diagnose the inverters,” Kangas said.

For example, Kangas explained that ABB’s PVS980 central inverter is compatible with control systems that enable maximum energy harvest by proactively monitoring the system status through a sophisticated SCADA system that can be completely digitally monitored and controlled.

“All in all, there are many reasons to use a large string solar inverters for commercial installations,” Kangas said.

“However, when it comes to the larger utility-scale power plants designs, central solar inverters tend to offer more customization, controllability and are more cost effective systems for larger utility projects.”

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12/16/16 2:55 PM

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12/19/16 4:30 PM

SOLARPOWER

R&M FLAT ROOF

FLAT ROOF RACKING & MOUNTING What happens when an east-west solar array isn’t perfectly east-west?

EAST-WEST ARRAYS are an increasingly popular configuration in the commercial solar market. With low module prices, it makes sense to trade a slight decrease in module productivity for greater overall system power production. By placing modules back-to-back, designers can avoid clearances for module shading, and can fit many more modules per unit area. Typical east-west arrays will have energy yield 5 to 10% worse than equivalent south-facing arrays, but 20 to 25% better power density.

Typical east-west analysis assumes that the commercial rooftop is facing north-south. Unfortunately, in the real world, many rooftops are not so orderly in their design. In the cases where there is no true “south” (and therefore, no true “east” or “west” either), how do these new racking products pencil out?

By Paul Grana, co-founder, Folsom Labs

having an array that is a combination of, for example, southwest- and northeast-facing modules is seen as a fundamentally un-sound PV system. But is it?

T H E P EN A LT Y F OR B EIN G OF F - A Z IMU T H It is no secret that modules do best when they are facing toward the equator. If we look at an example system in Charlotte, NC (a ballasted commercial array at a 10° tilt), the array 30° off of due-south produces 1% less energy than the south-facing array, while the array 60° off produces 4% less energy.

However, we get truly interesting results if we vary the azimuth of the east-west array. The east-west array has no penalty at all for being

IMPA C T OF B U IL DIN G A Z I M UT H O N A R R AY F I E L D

First, it is worth clarifying why the building’s orientation has any bearing on the module orientation. Solar arrays are typically designed to go with the direction of the building. There are a number of reasons for this: •

•

•

Cost-effectiveness. Positioning the array with the direction of the building makes it easier to install, secure to the roof as necessary, and maintain. In short, having the array not oriented with the rooftop incurs many additional costs.

Packing density. Most commercial arrays are spaceconstrained rather than demand-constrained. Designers can pack more modules into the roof when they are going “with the grain” of the roof versus against it.

Aesthetics. Solar arrays look better when they are aligned with the building. Symmetry is always beautiful, and aesthetics are often quite important to building owners.

In short, the building’s direction often dictates the orientation of the array –system engineers cannot simply require that their modules perfectly align based on the equator.

While this may be reasonable to consider for traditional south-facing racking, the concept of being off azimuth for an east-west array seems unacceptable for many engineers. To these designers, having modules pointed to the north is a cardinal sin that good engineers simply don’t do. By extension,

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k Wh /kWp

WHY D OES T HE BUI LDI N G O RI EN TAT I ON MAT T ER F OR T H E SOL AR ARRAY’S ORI EN TAT I O N ?

A zimut h Energy Yield as a function of Array Orientation, South-facing versus East-West.

off of due south – and in fact, produces slightly more energy (0.3% improvement for an array that is 60° off of due south). In absolute terms, note that the east-west array actually “catches up” with the south-facing array when the building is 60° off of due south. In that case, the array is benefiting from all of the packing density benefits of dual-tilt arrays, with none of the yield problems.

W H Y EA S T - W ES T IS N ’T A S B A D A S IT SE E M S How can it be that the energy yield of east-west arrays is so unchanged based on the azimuth angle? Much of it comes down to the offsetting impacts of the two sets of modules. As an east-west

solarpowerworldonline.com

12/16/16 3:02 PM

SOLARPOWER array rotates, one half of the modules gets pointed away from the equator, while the other half is rotated toward the equator.

The net impact is that there is essentially no penalty for being off-center for east-west racking systems. Interestingly, since there is a drop in yield for a single-tilt array (1-4%, as seen above), the comparative economics for east-west arrays actually looks better for nonsouth-facing rooftops.

“D U AL -TILT” VERS US “EAST -WES T ” East-west racking systems are becoming popular due to their ability to greatly improve system size in exchange for a modest downgrade in energy yield. Even for buildings that are not facing south, east-west racking (while not actually east-west) can provide all of the density benefits, with even smaller yield downgrades. In light of this, we should perhaps start calling the products “Dual-Tilt” rather than “East-West.”

2017 RENEWABLE ENERGY HANDBOOK

What is solar ballast?

BALLAST is a common alternative used on solar installations unable to penetrate either the roof or the ground. On lowsloped, flatter rooftops, many building owners don’t want to poke holes through the roof. Temperamental ground-mounts have some of the same concerns; solar arrays installed on top of landfill caps cannot penetrate that liner.

That’s where solar ballast comes in.

Concrete blocks are placed throughout a project to secure an array to the ground or the roof and prevent wind lift or other movement, all without having to make any (or as many) penetrations.

Cael Schwartzman, lead solar design engineer at Orion Solar Racking, explained there are many factors that go in to determining how much ballast

By Kelly Pickerel, SPW editor

a solar array needs. Most are pretty obvious: size and orientation of array; physical project location (wind, seismic factors); roof shape, height and strength; and type of racking used. Project jurisdiction must also be considered, as Schwartzman pointed out, because various jurisdictions have different code requirements.

Common rectangular-sized ballast blocks can be purchased at a home improvement store or anywhere that carries masonry blocks. The sources for unique block shapes and sizes specific to a certain racking system are provided by the racking manufacturer.

“The racking design will dictate the maximum size of ballast blocks that can be used,” Schwartzman said. “A system

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should be able to hold multiple blocks in each ballast pan such that weight can be added to or subtracted from a specific spot on the array. Ballast weight isn’t always uniform throughout an array.”

The core element of ballast—concrete blocks— hasn’t changed much since the beginning of solar installations. But project and racking design has led to the biggest evolution in ballast—less is best. By using wind tunnel analysis, the amount of ballast weight needed on today’s solar projects is less than before.

Changing how panels are interconnected allows for increased load sharing and an overall drop in needed ballast. Racking companies incorporating wind deflectors makes an array more aerodynamic and less ballast is needed to hold everything down.

An emerging issue with solar ballast is the breakdown of the concrete. Sam Veague, vice president of commercial sales at Ecolibrium Solar, said common concrete landscaping pavers can deteriorate through exposure to UV light, moisture and freezing/thawing.

“Depending on the design of the racking system, cracked or broken ballast blocks may fall out of the racking and end up with some or all of the ballast laying on the roof,” Veague said. “Thus [the ballast] is no longer doing its job of adding weight to the system to hold it in place. Broken chunks of concrete on the roof can damage the roof membrane.”

Veague recommends ensuring solar installers use concrete that has the appropriate rating for the local environmental conditions. Concrete is available in a range of ratings and quality levels, so a little homework can lead to years of solar success. Using high quality racking components also helps with ballast installations.

“Use a racking product with a ballast pan that fully supports the ballast block,” Veague said. “This means in the case of cracked or broken concrete, it is still held captive by the racking system.”

While there have been ideas for alternative ballast materials (jugs of water have been considered), concrete ballast isn’t going anywhere any time soon. Essentially simpler to install than penetrating systems—mostly from fewer pieces of hardware and less skill needed—ballast systems do require some technical know-how. With the right dedication to installation precision, ballasted solar systems can be a successful alternative to penetrating systems.

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SOLARPOWER

2017 RENEWABLE ENERGY HANDBOOK

SLOPED ROOF RACKING & MOUNTING What is shared rail mounting?

IN A TRADITIONAL shared-rail mounting system, such as the one pictured, the rails themselves are used to hold modules in place, eliminating the need for mid and end clamps. Recently, shared-rail systems have adopted clamp systems, too.

Composed of fewer components than other types of mounting, one primary benefit of shared rail systems is the reduction of parts installers are required to carry to a roof, making installation easier.

Because the rails are shared, a two-up installation requires three rails as compared to four for a standard mid and end clamp system. Shared-rail systems also require significantly fewer roof penetrations, with all penetrations being on a rafter, eliminating the risk of a “floating” penetration, which could occur in some rail-less installations.

In our experience, training for shared-rail systems takes less time than what’s required to master other system types. The most challenging aspect is ensuring rails are square, which can be accomplished with spacer bars.

Photo courtesy of Sarah Kelsen, Renovus Solar

Shared rail systems without clamps cover the entire side of a module, and the module frame becomes “bonded” to the rails, which can make for a more supportive as well as aesthetically pleasing installation. Shared full-rail systems reduce risk of damage to the module due to micro fractures.

It’s common knowledge that roof penetrations may be the Achilles heel of mounting systems. Installers constantly express concern over the number of roof penetrations required for system installation.

Roof penetrations are time consuming and costly, and, if improperly sealed, can create major post-installation problems and liabilities.

In a 12-module, two-up by five-across project, a rail-less system may require six penetrations per row, plus an additional six to secure the top row for a total of 18. Clamped systems could require up to five per rail for a total of 20. Current shared-rail systems require as few as nine roof penetrations for the same system.

So why haven’t shared rail systems taken a larger share of the market? It could be because they install so differently that installation companies have been reluctant to switch as they would have to retrain their crews. Perceived cost may also be a factor, as often installers are comparing the cost of the racking rails alone without taking into account the reductions in the number of flashings required to install the same number of panels.

By Michael Salvati, Vice President, Solar SpeedRack

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What should solar installers know about solar adhesives and sealants?

ALTHOUGH adhesives and sealants are small pieces of the solar module installation process, they play a big part in the quality, reliability and lifespans of systems. To make the most of installations, it’s critical for installers to understand how these materials can help complete successful projects that withstand extreme temperatures and conditions for decades.

WATE RPROO FI N G T H E ROO F The primary purpose of sealants is to waterproof the roof, which is crucial for ensuring a clean install and a long-lasting bond. To produce a solid hold, create a dam with a bondline thick enough (at least 2 to 3 mm) to hold off water. Be careful not to make the bond too thick, otherwise it’s susceptible to cohesion failures.

The sealant’s temperature is also a factor in the installation process. It’s important to apply it to the flashing as close to room temperature as possible, since low temperature can attract condensation while high temperature can flash off some of the cure chemistry.

By David McDougall, senior business development manager, photovoltaic group, H.B. Fuller While these principals—creating a dam and accounting for temperature— are not always practical due to the unpredictable nature of installations, they should be adhered to as often as possible to achieve reliable holds.

U N DER S TA N DING SUB ST R AT E S It may seem obvious, but understanding the different materials to be bonded, or substrates, along with the roof and solar mounting systems, goes a long way in terms of identifying which adhesive is right for your project. Some of the most common solutions include:

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•

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MS polymers: Used in roof materials like asphalt and are better suited for projects with low surface area.

Silicones: Ideal for projects with metal-to-metal systems.

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EX T R EME T EMP ER AT U R ES A N D C ON DIT ION S No matter where solar modules are placed throughout the country, they will be exposed to harsh conditions—both weather- and system-related. That’s why understanding various weather and project conditions plays a key role in successful installations. There are numerous settings to account for, but a few conditions to keep top of mind are: • Ambient conditions: These can impact the cure. Heat plays a role, but humidity is the primary condition that affects the speed of the cure (see the graph to the right).

• Cleanliness: Greater cleanliness results in better adhesion. After all, roofs can be messy, so do what you can to have a clean, dry surface.

• Carrying load: Although bolts and hardware will be the primary load carrying component, adhesives and sealants play a role here. They can also contribute to dampening loads of wind to the hardware.

A D HE SI V E S A ND SE A L A NT S: H O L D I NG I T A L L T O GE T HE R A greater grasp on applying adhesives, identifying the best substrates for projects, and accounting for extreme weather and conditions are all crucial pieces of a successful installation.

Installers who make a point of thoroughly understanding how adhesives impact installations will better positions themselves to install solar systems that are reliable, efficient and longlasting.

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2017 RENEWABLE ENERGY HANDBOOK

RAIL-LESS MOUNTS How can installers know if rail-free racking is right for them?

WITH RAIL-FREE RACKING trending in the market, installers now have many options to choose from in both railed and rail-free solar mounting configurations. But how can an installer know if a rail-free design is right for them? There are a few key differences when determining which system is best for your company and projects.

Knowing the benefits of each system can make the process easier and more cost-effective.

Installing rails on an obstacle-filled roof can be tricky, especially when installers need to cut rails on-site. Rail-free provides the advantage of high design flexibility, accommodating otherwise cumbersome and complicated layouts and offering

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RAIL-LESS MOUNTS

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more freedom in the placement of each stanchion. However, if an installer faces a design that is fairly straightforward and simple, such as a two-by-four consistent block of modules, then a railed installation may serve as a more suitable solution, especially if an installer is already familiar with a particular railed system.

Conveniently, properly designed rail-free systems provide ample amount of both NorthSouth and vertical adjustability similar to that found in many railed systems, so the installation of these newer systems may not seem too far off the beaten path from more traditional installations.

With a trained crew of installers, the installation times for rail-free should be faster (or at the very least similar) than railed systems.

Similarly, both systems require the same number of roof attachment points, governed by how much load the roof can take, so neither system sees a notable difference in the number of roof connections.

So where can installers see the significant difference? In the soft costs. Installers will notice large differences in shipping and handling. No rails means less material in inventory, more storage capacity, smaller trucks and less money spent on shipping.

Features such as integrated bonding and pre-assembly further decrease the overall part count for rail-free solutions. At the installation site, less material is carried onto the roof and on-site cutting is eliminated, allowing for more installs per day.

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However, there is one caveat. Although these changes are noteworthy, they do show a higher return on investment for large installers who benefit from economies of scale than those who perform just a few installations per week. Companies with multiple installation crews see the value more quickly than smaller installation companies.

Should smaller installers then disregard this new trend in solar? No, the advantages of going rail-free are still considerable and costeffective, just more time and patience will be needed until these differences become more apparent for certain installers.

2017 RENEWABLE ENERGY HANDBOOK

Going rail-free is certainly an innovative and revolutionary racking option that is breaking ground within the solar industry.

Capitalizing on this trend can reap certain benefits, yet those benefits may be more immediate and transparent for some installers compared to others. Knowing the right system and when best to use it can make all the difference for any solar installer.

By Brandy Diana Kay, Marketing Associate, Mounting Systems

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GROUND MOUNTS

GROUND MOUNTS What should contractors look for in a quality ground-mount provider?

By TerraSmart WHEN IT COMES to selecting the right partner and product for your next solar ground mount project, there are six key characteristics to always look for. These items will quickly narrow down the choices and lead you to the partner with the best selection of services and products for your next job.

Adjustability: Selecting a partner with highly adjustable racking will save money and time upfront by reducing, and in many instances cutting out, pre-construction civil work associated with earth moving or site grading. Look for a cross-slope tolerance of at least 30% grade and racks that allow for ease of installation with pre-drilled, adjustable slots and brackets throughout all steps of the rack assembly. Also, look for partners that offer more simplified hardware stacks. This allows for easier materials handling that takes less time to stage on the work site, and will result in a higher velocity completion schedule.

delivery, and should additional materials be needed, they can be moved to your site more rapidly. Typical time from manufacturing to worksite is four to six weeks, especially when choosing a rack sized for and made of readily available, roll-formed steel.

Installation Speed: How long will it take to get from ground to glass? Velocity can be increased by using adjustable racks made of roll-formed steel, eliminating pre-construction civil work and with simplified hardware stacks for easier materials handling. But what about unforeseen conditions? This is really where the rubber Photo courtesy of TerraSmart

Overall project cost: Everyone wants to find ways to lower cost. An easy way to do that is to look for a partner that uses recycled materials, such as roll-formed steel. Steel is both efficient and readily available, and the recycled quality does not impact the integrity or lifecycle quality of the product. Rather, this is a way to pull out cost upfront at the bid phase and will help you come in under a competitor on overall project pricing. That said, this must also factor into overall project cost, such as efficiency, reduction of pre-civil work and more. For example, if one partner is able to get your project online a month sooner due to efficiencies, that one month of additional energy that the customer gets out of the system will have a significant impact on profitability.

Delivery: How quick can materials make it to the site?

If you are building in the U.S., ideally look for a partner whose products are manufactured there. The last thing you want is for materials to be stuck on a slow boat from the other side of the globe. By choosing a partner with U.S. manufacturing, youâ&#x20AC;&#x2122;ll have more control over the speed of

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GROUND MOUNTS

meets the road with the partner you select. By choosing a partner that is vertical, meaning that they offer a truly turnkey solar ground mount build experience, you’ll be ready for whatever a project site throws at you. Look for a partner with everything from surveying to a construction arm for rock drilling and civil work, installation teams with product expertise and ideally one that manufactures their own parts so they have total control of the project timeline and can ensure continued velocity and hit your desired deadline.

Bankability: Financiers who are considering investing in your solar project want to know more than if you have the ability to fulfill your end of the bargain. They also want to know if your vendors can deliver on theirs. When it comes to solar ground mounts, look for a current and regularly up-to-date UL 2703 safety and performance listing, which will let you know the product is certified and safe. Look for a racking product that has a 20-year warranty to ensure the racks will maintain their integrity for the lifecycle of the solar project. Supply-chain

management is becoming an increasingly vital component of closing solar projects—so make sure you’re doing business with people who are as bankable as you are by looking for the right certifications, safety standards and warranties.

Experience: There is one easy way to judge experience and expertise: Has the partner you are looking at successfully installed at least 1 GW of product to date? But there are more questions you can use to evaluate a potential partner: Have they done a significant amount of work at the commercial and utility-scale level? Is their company steadily growing and expanding projects into new territories? Do they have an extensive history working successfully with unforeseen conditions in many different types of tough soils? Do they own their equipment and are their crews on staff rather than subcontracted? If the answers to these questions are “yes” and they have made it through the other five questions on this list with tangible results and references, you’ve got a solid project partner to add to your bid.

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CARPORTS

CARPORTS How can solar contractors improve the appearance of solar carports?

By Emily Wild, SPW research assistant

Photo courtesy of Osceola Energy

FOR POTENTIAL CUSTOMERS interested in installing a solar carport, visual appearance is a major concern.

Customers are usually looking for a structure that blends with the style of their pre-existing buildings and landscape.

“Unlike traditional solar arrays, a carport is part architecture, part engineering and always show-stopping,” said Christopher Fortson, marketing director at Osceola Energy. While rooftop solar is barely visible for people at ground-level, solar carports can be seen from a mile away.

Fortunately, there are many ways that solar contractors can improve the appearance of carports from all angles.

From a distance, it is easy to enhance the aesthetic through a simple coat of paint or by adding details such as lighting features, integrated artwork or trim additions. Neat wire management can improve the view from underneath the carport. At ground-level, inverter casings, conduits and electronics can be custom painted so they are less noticeable, Fortson said.

But just how much do these visual improvements cost?

Daryl Zeis of Baja Construction said a coat of paint is an addition of about $0.55 per square foot. Other details might make a more significant impact on the total cost, but the numbers can certainly be legitimized.

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“It’s important to remember that a solar carport can add value to a property in addition to reducing energy costs,” Fortson said. “Just like any outdoor renovation, the return value is only as good as its curb appeal.”

Fortson mentioned several examples of attractive solar carports constructed by Osceola Energy. One is a 250-kW solar carport system at the Santa Ana Golf Club in Bernalillo, New Mexico. It features aesthetics inspired by the Southwest that complement its picturesque background. A custom paint job, LED lighting and Spanish-style corbels create a visually appealing and functional piece of solar architecture.

Osceola Energy also built a residential project for a customer who wanted a solar carport to match the rustic appeal of the customer’s home. Developers color-matched the steel of the carport to the existing fencing and incorporated a traditional Southwestern snake design into the structure at the customer’s request.

Fortson and Zeis agree that the simplest aesthetic upgrade a solar contractor can make to a solar carport is color.

“Never underestimate the power of a simple coat of paint,” Fortson said. “A custom palette can transform a bland, cold steel structure into a work of art.”

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TRACKERS

TRACKERS How do self-powered trackers work?

ONE OF THE SOLAR INDUSTRY’S most impactful innovations is the invention of self-powered trackers (SPTs). These are a true advancement over conventional linked (ganged) trackers.

Engineered and designed for deployment in large and utility-scale scale PV arrays, SPTs incorporate small PV modules (of approximately 30W or more), accompanied by battery backup, and positioned in the middle of each tracker row.

These components power the self-powered controller (SPC), which in turn drives the motor to rotate the trackers. Each tracker row operates autonomously and relies on an onboard clock and inclinometer that adjusts each row throughout the day to track the sun precisely—leveraging the SPC’s processing power to calculate a daily algorithm.

Although the rows are physically unlinked and independent, they remain connected as a node within a sitewide wireless communications network for smart performance communications, precision monitoring and supervisory control.

Performance data is intelligently communicated over a ZigBee wireless mesh network that facilitates supervisory

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control and maintenance. SPT systems are accessed remotely, providing system owners, customers and stakeholders with a granular view to optimize tracker performance. In NEXTracker’s case, we use software to optimize operations and maintenance (we call it Digital O&M) and use machine learning for advanced diagnostics and real-time control of our solar tracking systems.

AC power is not required to move the tracker; the standalone SPC provides UPS for the tracker in the case of grid power failure. To ensure reliable wind-stowing, UPS systems are added to provide tracker power in the case of grid power failure.

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Less hardware and disruption in construction: SPT eliminates the traditional requirement for external power and UPS systems to power and control each row, saving costs associated with AC power supply, material and wiring, trenching and UPS backup costs. Intelligent control

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TRACKERS

electronics work to position each tracker optimally.

Because the SPC functions independently of grid power the entire commissioning process for all the trackers can be completed in parallel with the tracker build. This allows networking and IT teams to commission tracker and SCADA in unison without being dependent on the mechanical build of the system and trenching requirements.

More energy and reduced costs: SPTs (deployed by NEXTracker) facilitate rotational range that delivers up to 2% more energy yield than traditional linked row trackers.

Mechanically balanced row design aligns PV panels with the tracker’s axis of rotation; this greatly reduces row torque, using less energy from the motor to track throughout the day. SPT helps accelerate construction timelines, ensure repeatable outcomes and reduce costs.

Greater performance, increased safety and smoother O&M: With smart communications built in, SPT systems’ distributed, self-powered design and wireless monitoring capabilities provide customers with a granular view to

optimize tracker performance. In the case of NEXTracker’s NX Horizon SPT, data is pulled into the cloud and stored by Flex’s connected intelligence platform which manages data security and bank level encryption.

Single points of failure are eliminated and any tracker unit downtime will only impact ~25 kW of PV panels. In the event of a power outage, SPTs can operate independently of the grid. All trackers can go to stow at the same time, whereas others may need to do it in a gradual ‘staged’ approach, due to AC power requirements.

SPTs also eliminate costly backup power (UPS) infrastructure needed for trackers in many jurisdictions; it increases safety through much faster stowing. SPT (which doesn’t require wired input power to motors) eliminates separate grounding hardware, making it the fastest stowing of any tracker in rapidly changing weather. Exterior rows can be stowed at different position than interior rows rapidly and efficiently in various weather scenarios.

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CABLES

CABLES

What are some things a solar contractor should know about cables?

Photo credit: Snake Tray

W H EN T O P U R C H A S E Cables should be purchased as early as possible in a project.

Helukabel representatives noted that some solar panels are sent to the job site without interconnection between panels. A contractor should be ordering the cable or wire they need for the system before this point. The panels that do have interconnection already (commonly known as MC connectors) will only need to provide any extension cables and cabling to return to the inverters. The inverters and other control panels are usually pre-wired and the contractor provides the connections to the meter and interconnections of the panel and control hardware. It is when the panels arrive at the site that the interconnect PV wire is installed.

H OW EN VIR ON MEN TA L IS S U ES A F F E C T C A B L E S Significant environmental issues for cables, especially in solar projects, are the sunlight, temperature and chemical resistance needed for each installation. Helukabel explained that PV cables are exposed to extreme UV radiation.

Thermoplastic insulation and jackets (PVC) do not hold up as well to high temperatures and UV radiation compared to a thermoset material. Eventually over time these cables will dry out (plasticizers get hard) and the cables will fade and crack.

U L S TA N DA R DS F OR C A B L ES Cabling must comply to UL 4703 standards. There have been revisions to this specification to accommodate 1000 and 2000-V systems, and also to allow using aluminum, which has better price stability that copper, according to Helukabel.

EX P ER IEN C E MAT T ER S Helukabel said having experienced people planning the installation will assist with ordering the proper amount of materials at the earliest possible timeframe, which saves time, trouble and added costs during the project’s construction.

T R EN C H IN G IS EA S Y B U T MES S Y

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Trenching to bury cables is as easy as digging a hole and filling it in. But it can be messy—literally from dirt ,but also with issues such as hitting rock and divots filling with water to create mud. There are cable management solutions on the market. One from Snake Tray allows free air transit of cables.

Snake Tray said that this is more cost efficient and eliminates the need to de-rate cable capacity. solarpowerworldonline.com

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CABLES

What cables and connectors do you need for energy storage installations?

EVERY ENERGY storage system is different. To be fully prepared, it’s crucial to consider all wiring needs, from essential cables and connectors to the time needed to connect them. Long before you unwrap your batteries, ask yourself these questions: Six weeks before installation: Do I have the cables and connectors I need?

Each battery manufacturer has specific requirements for connecting and wiring batteries. The battery operations manual will contain essential information you must review before installation. We recommend that you closely read the operations manual at least six weeks before the day of

Cable Management for Solar Installations

installation. Some connectors or cables might have a long lead time, or they may not be available in your region. Give yourself adequate time to source the needed accessories and order ahead to avoid installation delays.

This six-week mark is also the right time to make sure you have the tools you need. Depending on the components in your energy storage system, you may need access to tools that aren’t in your everyday kit. For example, you may need a crimping tool for cables.

Identifying these necessary tools in advance will give you ample time to find or order them.

Two weeks before installation: Have I planned for adequate wiring time and labor?

Some batteries may ship un¬bussed or not connected and will require action before installation. Aquion Energy’s Aspen 48M batteries, for example, are shipped un¬bussed, and the top cover must be removed to connect the fuses before installation. A second review of the battery operations manual at least two weeks before installation will help you plan for all time and labor related to cables and connectors.

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SOMETHING NEW IS COMING OVER THE HORIZON

FOR YOUR PV SOLAR WIRING NEEDS, SOUTHWIRE IS INNOVATION THAT RISES TO THE OCCASION. With a strong commitment to innovation and sustainability, Southwire developed an answer to customer needs for enhanced UV protection on photovoltaic (PV) wire slated for solar installations above ground. Southwire’s newly-introduced Super Sunlight Resistant – SSR ™ photovoltaic (PV) cable provides a solution for ever-present solar rays, which age jackets on exposed above ground solar cables.

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SOLARPOWER

PYRANOMETERS

PYRANOMETERS What types of projects need pyranometers?

By Emily Wild, SPW research assistant

PYRANOMETERS are used during various phases of a solar installation. During the pre-construction stage of a project, they are needed to evaluate the location of the site by measuring the irradiance of the sun at a certain point. The irradiance is a measure of how much light hits a particular surface, usually expressed in watts per square meter, which is important in determining how much power a project could potentially harvest from the sun at a certain site. During post-construction of an installation, pyranometers are placed next to the PV panels to determine whether they are working properly, said Rodney Esposito, sales office director at Kipp & Zonen. These assessments are oftentimes used in conjunction with temperature measurements to obtain an accurate analysis of the module’s output, added Thomas Enzendorfer, president of Soligent.

There are two types of pyranometers: thermopile pyranometers and semiconductor pyranometers. A thermopile pyranometer measures the total amount of radiation on a surface using a thermopile detector, a device that converts thermal energy into electrical energy. A thermopile pyranometer has a horiztonal surface coated with a light-absorbing black paint that consumes radiation from the sun. A temperature difference is created between the black surface and the body of the instrument, resulting in a small voltage that is measured in watts per square meter.

A semiconductor pyranometer measures radiation using a photodiode, a device that converts light into a current.

An electrical signal is created from the solar radiation being absorbed. Semiconductor pyranometers are typically less reliable than thermopile pyranometers because they cannot capture the sun’s entire spectrum, resulting in measurement errors.

Pyranometers are mainly used in large-scale projects rather than smaller installations to determine the efficiency of the panels, explained Esposito. However, Enzendorfer said that all projects, despite their size, should use pyranometers to verify expected performance and ensure the installation will operate at its full potential.

Solar installers and project developers more prevalently use pyranometers, but anyone commissioning a system or troubleshooting to resolve issues with system production should use these measurement tools to obtain the most accurate analyses possible.

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A P YR ANOMET ER N EEDS MAI N T EN AN CE T OO The perfect time to send in a pyranometer for calibration is when the days get shorter and the sun is less powerful—late fall and early winter. Kipp & Zonen recommends pyranometers get recalibrated every two years to ensure the product is at its top performance level.

“The recalibration, complying to ISO 9847, provides proof of correct irradiance measurements that is often required by solar park owners and asset managers,” the company stated on its website.

During recalibration, pyranometers are tested to measure their sensitivity under controlled conditions equal to real-life service. With a calibration label and sensitivity certificate in hand, solar project owners can be sure the instrument is performing at peak reliability and accuracy.

While the pyranometer is off-site getting tested, asset managers can avoid measurement outages by swapping it out with a spare unit. Or, if multiple pyranometers are used on a site, sending them in for maintenance one-by-one can limit measurements loss. Kipp & Zonen offers an interchange service for certain pyranometer models to easily trade a loaner unit with the instrument to be sent in for servicing.

Proper maintenance on a pyranometer provides assurance to everyone involved with the solar project that next year’s yield measurements will be as accurate as possible.

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SOLARPOWER

BATTERIES & STORAGE

BATTERIES should be regarded as a fuel. They are expendable and have a fixed amount of energy they can discharge over their limited lifespans.

“Understanding battery chemistry, the leading causes of failure and properly maintaining them will allow the user to maximize the battery’s capabilities,” said Ron Rowe, senior sales engineer at Harris Battery Company. Two of the most common types of batteries used in solar installations are lead-acid and lithium-ion. Lead-acid batteries are typically declared dead when they can no longer provide 80% of their rated capacity, explained Jim McDowall, business development manager with Saft’s energy storage business unit.

Lithium-ion technologies often age linearly down to 60%.

The decomposition of a battery’s internal components depends on its type. Rowe explained that lead-acid battery deaths manifest themselves in two ways. The first is through gradual degradation of battery capacity through sulfation, a process that results in the buildup of tiny, sulfur-based dendrites in the lower, acidic part of the battery.

These dendrites block the transmit of electrons between regions of the active material, causing a reduction of battery capacity. The second manifestation is through catastrophic failure as active material is shed from the plates and causes a breach in the battery case.

The most common cause of death in lithium-ion batteries is wear-out due to cycling, or simple old age, explained McDowall. They can also experience failures to electronic components that worsen as those components reach the end of their lives. When lithium-ion batteries

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Why do batteries die?

Courtesy of Harris Battery

BATTERIES & STORAGE

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SOLARPOWER

BATTERIES & STORAGE

die, the structure remains intact, but there are gradual changes in the active materials that reduce capacity and increase resistance.

Temperature also largely affects battery life at a component level.

“Heat is the enemy of batteries,” said Rowe. “While a battery in warmer temperatures can produce more energy in the short term, the degradation of the internal components is accelerated.”

It is important to note that even short periods at high temperatures can have an impact on battery life, added McDowall. The damage sustained after a certain time and temperature shift above the standard operating temperature cannot be offset by an equivalent shift below that temperature.

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Although batteries sometimes die despite proper maintenance, there are steps that can be taken to maximize the life of a battery. Specifically for leadacid batteries, Rowe recommended keeping the battery fully charged when it is not in use. It is also important to provide proper watering for flooded batteries to maintain the manufacturer’s specific gravity rating and to keep the plates submerged in electrolytes. Finally, system sizing is crucial. Most manufacturers recommend sizing the energy storage system so that a typical discharge removes no more than 50% of the battery’s capacity. Always consult the manufacturer to gain a complete understanding of the battery’s expected life-cycle performance.

Beyond carrying out recommended preventative and corrective maintenance at the system level, usage conditions must be considered, McDowall added.

“In many cases with energy storage systems the owner is less concerned with long battery life than with return on investment, and in many cases this means paying less for a smaller battery, using it hard and then replacing the cell periodically as they wear out.”

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By Emily Wild SPW research assistant

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2017 RENEWABLE ENERGY HANDBOOK

SOFTWARE How can today’s solar software help residential installers?

SOLAR SOFTWARE helps solar installers accelerate and streamline their sales and design processes. In fact, with modern solar software, an installer can easily pre-design projects and develop a sales proposal before they even meet a homeowner.

They can know ahead of time where the modules will go on a roof and how much money a customer can expect to save, said Samuel Adeyemo, COO of Aurora Solar. Software can also help the homeowner visualize what their house will look like with modules on it, even before an installation crew arrives.

Paul Grana, founder of Folsom Labs, said usability is one of the most important aspects of a software program. Most software programs are not difficult to use and allow installers to quickly and accurately design installations.

Ease of use can ultimately increase productivity and customer satisfaction.

The majority of today’s solar software offer several common capabilities, Adeyemo explained.

The first is performance simulation, which calculates how much energy a solar installation will produce over a year. Financial analysis capabilities calculate a homeowner’s financial return from their installation. System design resources help installers

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choose the most efficient combination of modules and inverters for a particular roof. Proposal generation tools consolidate the performance simulation, financial analysis and system design into one place, so a solar sales person can easily present the opportunity to a homeowner.

Along with these common capabilities, some software offer premium features as well, Adeyemo added. Automatic system design accounts for shading conditions of a particular roof and automatically selects the optimal combination and placement of modules and inverters to generate the highest return for a homeowner. Shading analysis generates reports that can give

installers accurate irradiance and shading values even if they are not on-site. 3D system design creates 3D images of the installation that not only look better, but generate more accurate results.

Pricing for solar software varies between companies. One program, for example, costs $159 per user for a basic version and $259 per user for a premium version. Another costs $95 per month or $950 per year with team discounts starting at 10% for three or more users.

By Emily Wild, SPW research assistant

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SITE ASSESSMENT

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SITE ASSESSMENT How can we use the weather to assess a solar site?

WEATHER is one of the most important aspects to consider when performing a site assessment for a potential solar installation. Contractors must evaluate the intensity, characteristics and variability of irradiance at a location to fully understand its generation potential. From here they are able to make critical decisions regarding project design or whether to invest in the site. It is also important to measure temperature and wind speed since high winds and extreme temperatures affect the efficiency of PV panels, explained Gwendalyn Bender, energy assessment project manager at Vaisala.

Precipitation is helpful to measure as well since it can be used to estimate soiling or snow losses.

In the early stages of a site assessment, many contractors turn to free or low-cost data available from government agencies and private companies to get a sense of a siteâ&#x20AC;&#x2122;s resource potential.

Although this information is usually approximate and not specific to an installation it is often more sensible than investing in detailed information so early in a project.

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projects is by collecting information from satellite derived datasets, which use algorithms to determine surface irradiance through satellite images, elevation and snow measurements. To obtain site-specific observations, weather stations like pyranometers or pyrheliometers can be deployed at specific locations to measure the type of irradiance the solar project will use to create energy, said Bender. Weather stations also have sensors that measure wind speed and direction, precipitation, temperature and humidity.

Oftentimes, these short-term weather station observations are then combined with the uncertain long-term data to achieve an overall analysis of the siteâ&#x20AC;&#x2122;s average weather conditions.

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Bender recommended that weather station observations be taken at a site for a full year to capture the entire seasonal cycle. Although this may not always be possible, developers should at least ensure that observations are available for the peak production months.

There are some instances where weather might make certain design choices unfeasible, like if wind speeds or snow loads are so high they could break a tracking system. However, the solar industry has found ways to make most projects viable regardless of the siteâ&#x20AC;&#x2122;s weather conditions.

By Emily Wild, SPW research assistant

12/16/16 4:27 PM

DISTRIBUTION

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DISTRIBUTION How can distributors help contractors improve cash flow?

By Kathie Zipp, SPW Managing Editor

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COMPONENTS MAKE UP at least a third, sometimes half, of the total cost of a solar project. Often, solar contractors are asked to pay for the panels, inverters and other equipment before a job is inspected and functional.

But because homeowners aren’t usually expected to pay for a system until it’s proving to offset their energy costs, this heavy upfront component cost can stall or even sink contractors trying to increase business.

“Solar contractors growing their businesses often find themselves stretched for working capital, even as they reinvest their profits into their growth—hiring, marketing, trucks, etc.,” said Jonathan Doochin, CEO of national solar distributor Soligent. “By nature, a contractor’s growing business requires more working capital to cover operating costs to achieve larger revenues. Inevitably, there becomes a constant struggle of cash-flow management between balancing contract terms with customers, establishing credit lines for equipment and meeting finance payment milestones—not to mention timing when they pay their sales teams.”

Increasing demand for solar theoretically sounds good for business, but this growth can also complicate cash flow. Nestor Tarango, ‎director of sales at New Mexico solar distributor Affordable Solar, illustrated this difficulty. A contractor selling and installing 10 systems per month will need about $70,000 in cash reserves to cover equipment procured prior to customers paying in full. A line of credit can help lower the total reserved cash needed. However, if sales jump a month—say from a successful marketing campaign—doubling their installations, their reserves and credit capacity must also double to purchase equipment for the extra jobs. This doesn’t even include overhead costs such as labor and administration expenses.

“In this new, fast-paced industry, this sort of growth is not uncommon,” Tarango explained. “It is exciting for a contractor to see an incredible jump in sales, but it can be nearly impossible to manage from a cash flow perspective.

This challenge is compounded for new contractors who don’t have the business history to justify a trade line of credit or vendor relationships.”

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The cash flow conundrum has moved distributors like Affordable Solar and Soligent to develop financing and credit solutions for their customers.

In addition to an equipment credit, Soligent’s Solar Engine program enables smaller contractors to offer financing options which may be more difficult to obtain from banks. “Financing has historically given the upper hand to the larger solar installers who can interface directly with banks,” Doochin explained.

“Through our Solar Engine program, we are giving access to affordable and simple finance products—residential and commercial loans and PPAs— to

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local- and state-level installers, allowing them to compete on a level playing field. A good financing product unlocks new customers who wouldn’t otherwise be able to afford the system and provides working capital for installers to grow their businesses. Between the equipment credit and the working capital and consulting support through Solar Engine, we’re enabling our customers to grow as quickly as they can sell.”

Affordable Solar also offers loans, leases and PPAs to help contractors offer solutions to more customers. The distributor’s “direct-pay” program helps

contractors with cash flow. Financers pay Affordable Solar directly for equipment.

“This gives our company security in the deal and allows our customers an extended line of credit,” Tarango said.

“Direct-pay programs have allowed several of our customers to grow from installing 15 to more than 120 systems per month, without having to raise outside capital. Direct-pay offerings give more solar contractors the competitive advantage of access to affordable financing options, and credit limits that fuel growth.”

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SOLARPOWER

OPERATIONS & MAINTINENCE

OPERATIONS & MAINTINENCE What does it take for solar installers to provide O&M services?

GLOBAL SOLAR INSTALLATIONS are expected to reach 321 GW by the end of 2016, exceeding 756 GW by 2025. As the world’s inventory of solar PV assets grows, it is not surprising to see those industries related to post-installation—operations, maintenance and asset management— exploding as well.

This explosion of solar PV systems of all sizes around the world is driving the need for cost-effective O&M practices and company specialization to ensure best practices and superior plant performance.

While the solar O&M market got its start when EPC companies needed to service the installations they built, the landscape is changing. Lately, the market is moving in favor of independent service providers 126

(ISPs). This can be attributed to the maturation of the market and the need for specialized service offerings.

The level of complexity for O&M and asset management grows as the size of the install increases, with utility-scale installations requiring a sophisticated suite of services to manage and onboard large amounts of power onto the grid.

But for those installers looking to add O&M to their service offerings, here are the basics on how to get started.

C OS T FA C T OR S OF IN - H OU S E S OL A R O&M If installers are interested in providing solar O&M services or expanding on their existing capabilities, there are several areas of functionality that should be reviewed. Can the installers perform plant monitoring, analytics, root cause detection and other reporting functions? Are there dedicated skilled technicians, O&M managers, software/IT experts, financial and accounting personnel available?

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Alectris O&M technicians on-site (Credit: Alectris)

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SOLARPOWER

OPERATIONS & MAINTINENCE

There are three basic functions an O&M department is asked to perform: • Fast problem identification and resolution • Minimization of down-time due to faults • Detailed reporting and transparency In order to determine the company’s ability to comply and even outperform the contractual obligations related to a specific solar project, it is important to define what qualities and competencies are needed to excel in these three functions.

The design or architecture of the O&M provider, whether in-house or outsourced, can be evaluated on three areas of functionality–core systems, supporting systems and management.

The Alectris O&M control room in Greece (Credit: Alectris)

COR E S YS T EMS This set of properties is absolutely necessary to perform solar PV operations and maintenance services at a minimum. Such core capabilities include: DAS (Data Acquisition System): Companies often develop their own proprietary systems or rely on third-party platforms. Contractors who use multiple systems often have a difficult time consistently monitoring their portfolios due to differences in performance of various systems. DASs should be evaluated on specific competences, including small things like lag time between data generation and insertion into the database. It is important to identify how comprehensive a DAS is in terms of devices monitored and also parameters measured on those devices.

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Data Analysis Capabilities: Massive amounts of data is generated from each solar PV plant in a company’s portfolio, and appropriate IT tools must be used to accurately analyze this data. Whether analytical capabilities are integrated in the DAS or are provided by an external tool, the requirements remain the same.

Analytical tools can be rated according to their customization and the range of pre-configured analytical reports. One important aspect that needs to be taken into consideration is the reporting on the solar O&M activities performed and their outcome. All the above should ideally be related to as-built data in a hierarchical manner, so that analysis is more meaningful to engineers.

Field Personnel: The types of field personnel needed to maintain the physical aspects and installation environment of a solar site range from plant security and maintenance to panel cleaning, testing in the field, equipment technicians, electricians, etc. There are specialized services now even within each of these areas. Hiring and managing these resources dictates another level of expertise needed within the solar O&M service area.

Control Room: The solar O&M control room is the heart of the operations—the command center. The operators in the control room analyze faults and provide the instructions to the field personnel for their interventions. The technological infrastructure of the control room, which is tightly connected with the DAS, analytical tools and CRM, is also of key importance.

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Engineering Capabilities: Engineering capabilities are very often undervalued mainly due to the fact that the role of the solar O&M service provider is often restrained to basic preventative maintenance activities and responding to incidents. The importance of engineering in analyzing deficiencies and proposing technical enhancement is of major importance.

SU P P OR TIN G S YS T EMS Supporting mechanisms required to keep a solar O&M operation running at maximum efficiency include: Quality Assurance & Accountability: Like any other service provider, O&M providers have to perform its services at the highest level. Especially in distributed environments, when different teams are getting involved in problem resolution, it is important to measure quality of the services, track activities of people involved and focus on deficiencies through training programs. It is critical to measure such services in an objective way to provide needed insights for management.

Process Control: Especially when the portfolio consists of geographically distributed solar PV plants, having a tight control on the processes through documented internal processes, written procedures for in-house or outsourced personnel is necessary to ensure all activities are executed according to exact plant, O&M plan and budget specifications.

2017 RENEWABLE ENERGY HANDBOOK

MA N A G EMEN T Skilled professionals are required to manage a solar O&M discipline within a company. Typically having an engineering and/or deep solar PV background, they oversee the plant maintenance activities starting at the onset to manage the handoff of newly constructed solar plants from construction to O&M. They are responsible for in-house technicians or outsourced subcontractors in every area of maintenance. They oversee warranty part inventory.

Their responsibilities include the control room and IT functionality and asset management reporting, along with department reporting.

The complexity of solar operations, maintenance and asset management, including the need for robust software support, demands a sophisticated approach to plant operational health.

This may or may not be feasible within the average installerâ&#x20AC;&#x2122;s capabilities. An objective review of what is truly required will shed light on the feasibility of delivering a full suite of O&M services in-house.

By Laks Sampath, country manager of U.S. & Latin America for global solar O&M firm Alectris

Knowledge-base of Problem Resolution: Solar PV plants are similarly constructed regardless of their location. There are few technological differences, and the vast majority of arising issues tend to be very similar. Building a centralized knowledge-base of issues dealt with (and resolved) in the past can be a significant help for engineers, operators and field personnel to increase efficiency and speed of problem resolution.

Tracking Activities and Measurements by Field Personnel: Although a DAS captures vital data from all devices in a solar plant, this alone does not provide a holistic view of the PV system, since throughout the duration of an O&M contract a variety of activities are performed. Apart from simple tasks and preventative maintenance, the service provider may perform a wide range of field measurements to analyze and troubleshoot faults. Such measurements are valuable data contributing to the understanding of a plant behavior. Every service ti cket and steps taken to resolve issues are critical to ensuring corrective and preventive maintenance activities are recorded and preserved.

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CONSTRUCTION, INSTALLATION & DEVELOPMENT

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CONSTRUCTION, INSTALLATION & DEVELOPMENT How should installers stay current on permitting codes and procedures?

Photo courtesy of Wayne National Forest Flickr

IT’S IMPERATIVE to the growth of the solar industry that installers stay current with the pace of solar technology evolution. Updated professional training is critical, including the latest best practices for permitting processes and electrical codes. Also at the heart of successful permitting is communication—between both industry professionals and local code officials.

Across the country, jurisdictions are either overloaded with solar permitting applications or they lack the steady stream of solar projects and the know-how to handle inspections. Some areas with long queues are streamlining the permitting process for efficiency to allow more firsttime approvals without compromising the quality of installations. In other

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regions, excessive paperwork, multiple callback inspections and related delays may be common, either due to the inspection and permitting process or contractors who aren’t sufficiently familiar with what code officials expect. In all cases, the disconnect can affect solar installers’ bottom line and that of their customers.

That’s where communication comes into play. As a professional contractor or installer, knowing what an inspector is looking for and keeping up with current codes and procedures will help move the permitting process along as efficiently as possible. Likewise, contractors with quality solar training and experience may position themselves to educate a less experienced inspector on the most current tools and best practices for solar installation and permitting.

An interactive online PV training course created for code officials and increasingly used by contractors and installers can help. It’s referred to as PVOT (PV online training).

While the course was originally designed for code officials by a prestigious working group of subject matter experts, under the guidance of the International Association of Electrical Inspectors (IAEI) and the Interstate Renewable Energy Council (IREC), it is increasingly utilized by electrical and general contractors, PV installers and others who can benefit from the knowledge presented in a self-paced, online format. It can be thought of as another tool in an installer’s professional toolbox.

The free course offers CEUs from the IAEI, the International Code Council (ICC) and NABCEP (North American Board of Certified Energy Professionals).

“One of the things most valuable for a contractor is building confidence with an inspector, so they feel you know and follow the applicable codes and standards,” said Don Hughes, a code official with Santa Clara County, California, for more than 20 years who was involved with the development of the PVOT since its initial creation in 2012.

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12/16/16 4:37 PM

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CONSTRUCTION, INSTALLATION & DEVELOPMENT

PVOT features seven lessons that cover key points and common installation mistakes. A “capstone” lesson then offers a game-based 3D model for roof-mounted residential PV installation.

An information icon throughout the training references the 2008, 2011 and 2014 National Electric Code as well as the 2012 international fire, residential and building codes.

“PVOT is an excellent source for PV installers as well as code officials and inspectors since they can both be participants in speeding up the permitting process, while never compromising safety or the effectiveness of an installation,” said Joe Sarubbi, who directed the development of the original PVOT and its most recent update for IREC and the IAEI. A former solar instructor and electrician who set up a nationally recognized renewable energy training program at Hudson Valley Community College in Upstate New York, Sarubbi was IREC’s project director for the SITN (Solar Instructor Training Network), which provided training to more than 1,000 solar instructors in colleges and other training facilities across the United States.

The newly updated PVOT includes a chapter on streamlining the permitting process for code officials and industry experts, as well as a new chapter on the I-codes (IBC, IRC, IFC) to help code officials who handle all code-related issues.

“In developing the PVOT, we were aware that small municipalities don’t always have electrical inspectors and building inspectors. It’s usually one person doing it all,” Sarubbi said. “Either way, in small and large communities, by taking the online training, the PV installer gets a better feel for what inspectors are going to need—up-front and during the inspection process—to ensure the timeline from inception to completion is reduced.”

The training is part of the U.S. Department of Energy SunShot Initiative’s STEP project (Solar Training for Energy Professionals), for which IREC serves as national administrator.

Since launched just four years ago, nearly 5,000 code officials and industry professionals have begun the online PV training. While some complete the entire course, including quizzes that test the knowledge learned, others spend time only on select lessons. CEUs are awarded only for course completion.

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As for the permitting process, some states, such as Vermont and California, are taking on solar permitting as a state issue rather than leaving it to local authorities having jurisdiction. There is some movement on the national level to encourage more consistent permitting processes, at the very least in the form of standard recommended guidelines.

The Solar America Board for Codes and Standards (Solar ABCs) has created a model streamlined permit process for small-scale PV systems, which it recommends local jurisdictions use. According to Solar ABCs (a separate program funded by the U.S. Department of Energy), the suggested process takes advantage of the many common characteristics inherent in most small-scale PV systems installed today, both to streamline the application process and the awarding of permits.

The streamlined permitting process is intended to simplify the structural and electrical review of a PV system project of less than 15 kW, according to Solar ABCs, and to minimize the need for detailed engineering studies and unnecessary delays.

As permitting authorities across the country become more burdened with high volumes of solar permit applications, keeping the process moving efficiently is as important for them as it is for the solar industry. IREC is helping to identify reforms that offer benefits to both.

“With so many jurisdictions involved, consistency and standardization are among the keys to driving down the installed cost of solar and other renewable energy,” said IREC regulatory director Sara Baldwin Auck. “One of the things we’re doing is spreading the word about innovative processes some communities have adopted. Best practice examples show forward-thinking jurisdictions are providing transparent and efficient permitting and inspection procedures, streamlining the process to lower costs for solar developers and ultimately consumers.”

By Ruth Fein Revell, communications manager for the Interstate Renewable Energy Council (IREC)

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SOLARPOWER

SAFETY

2017 RENEWABLE ENERGY HANDBOOK

What are the National Electrical Code fire safety requirements for PV arrays?

THE SAFETY CONVERSATION involving rooftop solar has largely been influenced by the NFPA and others responsible for developing nationally recognized codes and standards. First responders are worried about dangerous current running through a solar array when responding to a building fire. The 2014 edition of the National Electrical Code (NEC) requires rapid shutdown for roof-mounted solar PV (essentially a way for firefighters or others to quickly control and shut down an entire PV system’s circuits at a single point), while NEC 2017 takes the code one step further, requiring shutdown to occur at the module level.

The 2017 edition will take some time to go into effect and become adopted by states, but the 2014 code is largely accepted nation-wide and guides the current fire safety rules within solar.

Marvin Hamon, principal with Hamon Engineering, said many solar installers don’t see the need for rapid shutdown, but firefighters and insurance companies largely support a way to turn off the electrical charge of a PV array.

“The 2014 NEC rapid shutdown requirements were always intended as a starting point, and the 2017 revision was to expand on them,” Hamon said. “Modulelevel isolation is about as far as the NEC can take rapid shutdown since anything else requires changes in the products themselves.”

N EC 2 01 4 A N D R A P ID S H U T DOW N Rapid shutdown was first introduced on a wide-scale with NEC 2014. Firefighters want to know how to shut down a solar system to prevent shock when responding to an emergency. DC disconnects help to stop the flow of electricity, but they don’t limit dangerous voltages.

Firefighters often have a false sense of security when using just DC disconnects because there still may be electricity flowing through a part of the system.

NEC 2014’s rapid shutdown requirements (NEC 690.12) provide some instruction for installers. They say first responders should be able to turn off a PV system’s voltages using a clearly labeled switch or disconnect.

How and where these devices are installed is up to an installer’s interpretation of the NEC.

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“The 2014 NEC was non-specific about several points in rapid shutdown, such as how the rapid shutdown would be initiated, how the array was to be isolated, etc.,” Hamon said.

“It indicated what had to happen, when and at what point, but the rest was left up to the AHJ and installer to decide how to implement.”

When setting up a solar array, installers have to incorporate PV circuit conductors within 5 ft of entering a building or within 10 ft of the array. During rapid shutdown, solar arrays have 10 seconds to limit voltages to no more than 30 V (considered touchsafe in wet locations). Most of these requirements are easily met by inverters and optimizers currently on the market. If not, rapidshutdown controllers and/or combiner boxes are often where first responders can find shutdown devices.

NEC 20 17 AN D MO DULE-LEVEL S H UT D OW N While PV shutdown requirements in NEC 2014 were essentially vague, proposed revisions to NEC 2017 are much more detailed—expanding from less than 150 words to more than 1,100. Module-level shutdown becomes law of the land with a new section enforcing an 80-V limit within the solar array boundary, essentially mandating the use of module-level power electronics (MLPEs). Many firefighters are advocates of the new revisions. Even those who don’t completely understand its technicalities think “module-level shutdown” sounds a lot safer than “rapid shutdown.”

Module-level shutdown can be accomplished using microinverters, DC optimizers, smart modules, AC modules and other MLPEs, which have all been on the market for some time.

MLPE manufacturers obviously support the new code because their products inherently meet it. Though string inverters are not built for module-level shutdown, manufacturers are coming out with innovative solutions to meet the code such as incorporating optimizers. Other in-array shutdown devices may also be coming to market.

“Module-level shutdown requires module-level electronics and remote control,” Hamon said. “While the overall safety will be improved, it would be hard to overlook that the additional components might reduce the reliability of the system.”

However, many MLPE manufacturers argue that their products actually provide more system uptime than string inverters, though they come at an initially higher cost.

The effects of NEC 2017 have yet to be seen, and with a louder outcry from the anti-module-level-shutdown crowd, it will be interesting to see how AHJs handle future solar installations.

By Kelly Pickerel Associate editor, SPW

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WINDPOWER

2017 RENEWABLE ENERGY HANDBOOK

AD INDEX 3M Personal Safety Division, Fall Protection Business....................... 43 Abaris Training ................................................................................... 42 ABB Power-One ................................................................................. 83 AeroTorque ........................................................................................ 29 AMSOIL Inc. .................................................................................... IFC APsystems ......................................................................................... 79 Arraytech ......................................................................................... 110 Aurora Bearing Co. ............................................................................ 20 Axitec Solar USA ................................................................................ 72 Aztec Bolting ..........................................................................Cover, 23 Bachmann Electronic ......................................................................... 50 Baja Construction ............................................................................ 107 Bal Seal .............................................................................................. 59 Bronto Skylift ..................................................................................... 40 Campbell Skylift .............................................................................. 123 Castrol Ltd. ...................................................................................... IBC Chint Power Systems ........................................................................... 1 Cincinatti Gearing Systems ............................................................... 45 Cornell Dubilier Electronics, Inc. ....................................................... 81 Deublin Co. ....................................................................................... 25 Dexmet Corp. .................................................................................... 35 DPW Solar ....................................................................................... 105 Dunkermotoren, part of AMETEK ................................................... 109 EcoFasten Solar ............................................................................... 101 Ecolibrium Solar .............................................................................. 100 Everest Solar Systems, LLC ................................................................ 94 ExxonMobile ...................................................................................... 54 Firetrace ............................................................................................. 39 Fortune Energy ................................................................................ 125 Fronius USA LLC ................................................................................ 85 GameChange Solar LLC ...................................................................... 3 Gradient Lens Corp. .......................................................................... 46

SALES

GroWatt ............................................................................................. 89 Helukabel, USA.......................................................................... 27, 113 HYDAC International ......................................................................... 52 IMO Precision .................................................................................. 135 IXYS ................................................................................................... 84 Kipp & Zonen USA Inc. .................................................................... 117 MageRack Corp. ................................................................................ 93 Mattracks, Inc. ................................................................................... 57 Megger ............................................................................................ 127 Methode Inc. ................................................................................... 119 Moog Inc. - Components Group ............................................Wind Tab Mounting Systems, Inc. ................................................................... 104 Norbar Torque Tools, Inc. .................................................................... 7 Panasonic Eco Solutions .................................................................... 71 RBI Solar/Renusol ........................................................... Solar Tab, 103 Renewable NRG Systems .................................................................. 49 Roof Tech ........................................................................................... 97 Rotor Clip Co., Inc. ............................................................................ 19 S-5! .................................................................................................... 96 Schneider Electric IT ............................................................................ 5 Seaward Group ................................................................................ 131 Snake Tray ....................................................................................... 114 Solar Connections International ........................................................ 98 SolarEdge Technologies Inc. ............................................................. 77 SolarRoofHook .................................................................................... 4 Solectria ...................................................................................... 91, BC SOMO ............................................................................................... 80 Southwire ......................................................................................... 115 Specialty Coating Systems, Inc. ......................................................... 15 SUNGROW POWER SUPPLY Co. ...................................................... 87 Trelleborg Sealing Solutions .............................................................. 61 Zero-Max, Inc. .................................................................................... 31

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