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December 2017

The technical resource for wind profitability

2018 Renewable Energy


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Welcome to the Guidebook..................................................................................................06

ENERGYSTORAGE Energy storage articles...................................... 08

WINDPOWER Editor’s welcome............................................... 18 U.S. wind speeds map ...................................... 19 Top wind stats.................................................... 20 Components of a wind turbine.......................... 22 Wind power articles Technology & Components...................................................24 Safety.....................................................................................37 Project Development.............................................................38 Operation & Maintenance.....................................................44 Offshore.................................................................................52

SOLARPOWER Editor’s welcome............................................... 56 U.S. solar irradiance map .................................. 57 Top solar stats.................................................... 58 Solar power articles Technology & Components...................................................60 Project Development.............................................................94 Business Issues......................................................................98 Education & Policy..............................................................100

Ad Index........................................................................................................................................... 104 - -

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welcome to the 2018 renewable energy


IF YOU’RE FAMILIAR WITH THIS PUBLICATION, you’ll notice we’ve changed our name from “handbook” to “guidebook.” In an effort to produce the best content possible, we took a moment to step back and consider what information in this “extra” edition would be the most beneficial to our readers. While in the past we’ve let an outline of narrow categories dictate our content, by combining topics into broader sections, we now have the flexibility to cover the most relevant information that sometimes overarches wind, solar and energy storage topics. We’ve traditionally focused on basic educational content, but this structure allows us to feature topics most relevant to today’s industries. We didn’t feel that this publication was an intro-level handbook but instead an industry guidebook for the year—hence, the new name. At the beginning of the wind and solar sections, our editors give you a general overview of the state of each industry. Michelle Froese discusses how as tax credits are ramping down, wind development is ramping up with 29,634 MW of wind projects under construction and in advanced development. AWEA reports that wind is on track to deliver 10% of America’s electricity by 2020. New construction will require lots of labor, and wind technician jobs are projected to be one of the fastestgrowing jobs in the United States. The solar industry is also seeing a huge demand for solar installers. In her editorial, Kelsey Misbrener talks about her impressions of solar during her first year covering the industry. She saw how the industry “bobbed and weaved with the punches,” including the uncertain results of a trade case and tax bill. But she also saw solar break records in 2017, and the industry continues to push forward. We also have an exciting new industry to cover in our guidebook: storage. The Energy Storage Association reports that energy storage systems currently make up approximately 2% of U.S. generation capacity—more than the solar industry. Furthermore, U.S. energy storage deployments were up 46% annually in Q3 of 2017. Storage is growing rapidly with development of more renewable energy. It seemed the right time to include a section dedicated to storage in our guidebook and launch a new publication: Energy Storage Networks (ESN) at Michelle Froese and I will develop storage content and attend storage conferences in 2018. If you’re in the storage market, please connect with us and help us learn. It’s very exciting to delve into a new industry! Don’t forget we have solar inverter, panel and racking, and wind project and turbine databases online. We’ve also launched a new battery tool on ESN. We hope you find this new guidebook useful. We look forward to working with you in 2018! SPW WPE&D ESN


MANAGING EDITOR Solar Power World @SolarStorageKZ



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COMPONENTS OF AN ENERGY STORAGE SYSTEM INSTALLING A SOLAR ARRAY WITH BATTERY BACKUP requires some different components than traditional systems. Here is a quick rundown of the components involved in grid-tied PV solar storage system with batteries. Hybrid inverter A hybrid inverter (also referred to as a bidirectional or battery-based inverter) is typically a string inverter that can operate bidirectionally. This means it can take DC from the array or the battery, supply AC to the grid or critical load panel, and charge from the PV panels or the grid. A hybrid inverter can isolate the system from the grid when the grid is down so the system can still provide power to critical loads without feeding it into the grid. In contrast, when systems with traditional string inverters disconnect when the grid is down, no solar power is able to be generated or used. The job of a string inverter mainly consists of checking if the grid is online and if PV is being generated, and then converting powering and sending it to the grid. However, hybrid inverters need to be pretty smart, taking an intelligent approach to power management. This is especially important because of changing time-of-use rates that affect the cost of electricity at different times. The inverter needs to determine where the power is coming from and what critical load is needed to manage power from the batteries, array and grid to get the best electricity savings and financial return possible for the system owner. Battery management system A battery management system (BMS) helps control parameters such as battery temperature, depth of discharge and state of charge so the batteries aren’t over or under charged, which can affect their life. A BMS is usually a software function internal to a charge controller or more sophisticated charging device. A BMS is critical when using lithium-ion batteries because there is more risk for thermal issues with this chemistry. When using other batteries, such as lead acid, a BMS can be included

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By Kathie Zipp, managing editor; Solar Power World

but is not critical because there is less risk of thermal issues, and the inverter or charge controller can usually handle charging regimes. Batteries Choosing the right battery for a system is essential for optimizing project life and performance, and minimizing maintenance costs and downtime or failure. There are different types of batteries, and manufacturers within each type make their products differently. Exploring the different types of batteries and asking your manufacturer or distributor the right questions can help you decide which chemistry and manufacturer is right for you. You’ll also want to make sure you size the battery properly to the array and provide proper O&M for the best performance and battery life.

An example of power flow in a hybrid inverter system. The inverter can direct power to a load or the grid if needed, or store it in batteries if not. It can also use power from the grid if needed. (Photo credit: GreatWall)



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By Kathie Zipp, managing editor; Solar Power World

A lead-acid battery.

(Photo credit: Rolls Battery)

INTEREST IN ENERGY STORAGE IS GROWING RAPIDLY. It’s not all about living off the grid anymore. Storage helps solve variability issues with renewables. Adding solar batteries to a grid-connected residential project also allows the array to keep providing power to critical loads when the grid is down, instead of having to disconnect and refrain from generating power. Storage can also help commercial consumers reduce peak demand charges, significantly lowering their energy bills. Storage is even used at the utility level to help provide ancillary services to the grid. The need for storage grows as states pass self-consumption legislation. Here’s a look at these aspects of some of the more popular battery technologies. Lead acid Deep-cycle, lead-acid batteries have been reliably used globally for decades. Cost: Typical deep-cycle, lead-acid batteries cost significantly less than lithium-ion. Cycling: Valve-regulated lead-acid (VRLA) batteries include absorbed glass mat (AGM) and gel models. Many AGM batteries available in the market are primarily built for dualpurpose or standby applications like emergency backup, but not deep cycling. However, new deep-cycle AGM designs have increased performance and total energy output making them a good choice for renewable energy applications at a lower price point than gel batteries. In fact, VRLA batteries with added nanocarbon are more resistant to sulfation, which can lead batteries to die over time. The carbon slows sulfation and allows the battery to charge faster and cycle more than traditional lead acid. This makes it a good choice for applications in which the battery is in a partial state of charge, such as energy arbitrage or off-grid.



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Replacement/maintenance: Many factors including initial design and ongoing maintenance influence battery life so it’s difficult to put a time frame on when the batteries will need replacement. Flooded lead-acid batteries have to be refilled regularly because the electrolyte that fully submerges the battery plates evaporates during charging. The battery enclosure needs ventilation to keep hydrogen gas from accumulating to dangerous levels. AGM and gel technologies, however, are recombinant, meaning they internally convert hydrogen and oxygen into water and do not require maintenance. As there is no free acid inside these batteries, they can be installed in any position other than upside down. Because solar applications can be in hard-to-reach or remote areas, the ability to install the batteries and let them operate over long periods without maintenance is a benefit. Disposal: Proper disposal of lead-acid batteries is important because they are toxic. Thankfully, the automotive industry organized to recycle lead early on. Plastic containers and covers of old batteries can also be neutralized, reground and used in new battery cases. In some cases, the electrolyte is cleaned, reprocessed and sold as batterygrade electrolyte. In other instances, the sulfate content is removed as ammonium sulfate and used in fertilizers. The separators are often used as a fuel source for the recycling process. Old batteries may be returned to the battery retailer, automotive service station, a battery manufacturer or other authorized collection centers for recycling. Lithium-ion According to a U.S. Solar Energy Monitor report, lithiumion batteries are the most common storage technology, regardless of application. There are three types: pouches such as in smartphones and tablets, cylindrical such as in power tools, and prismatic (which come in various shapes) such as in electronic vehicles. Prismatic types often have corrugated sides, which create air gaps between adjacent cells and can aid in cooling. The prismatic can have applications in renewable energy storage, specifically lithium iron phosphate (LFP) batteries.

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Disposal: Lithium-ion batteries can use organic or inorganic cells. Organic-based batteries are free from any toxins. Inorganic-based cells are much more difficult to dispose of. Inorganic lithium-ion is toxic so it must be disposed of properly. Manufacturers encourage recycling, but there is often a price. Spent lithium-ion cells have little commercial value. Lithium-ion manufacturing involves lengthy preparation and purification of the raw material. In recycling, the metal must go through a similar process again, so it’s often cheaper to mine virgin material than retrieve it from recycling. A lithium-ion battery.

(Photo credit: Simpliphi Power)

Cost: Deutsche Bank analysts estimated lithium-ion batteries at about $500/kWh at the end of 2014, but one manufacturer said it’s closer to $750 to $950/kWh. Overall, they are more expensive than lead acid batteries. Part of this cost comes from needing a battery management system to monitor the voltage and temperature of each cell to prevent excessive charging and discharging. A BMS isn’t critical for other technologies like lead acid because the inverter or charger controller can handle the battery charging regime. However, some manufacturers note that, if sized correctly, lithium-ion cells can reduce the cost of peripheral devices like charge controllers, offsetting its higher initial price and lowering cost-of-ownership. Cycling: Lithium-ion batteries can typically deliver more cycles in their lifetime than lead-acid. This makes them a good choice for applications when batteries are cycled to provide ancillary services to the grid such as energy smoothing or frequency and voltage support. The most important benefit lithium-ion provides for solar is its high charge and discharge efficiencies, which help harvest more energy. Lithium-ion batteries also lose less capacity when idle, which is useful in solar installations where energy is only used occasionally.

Flow batteries Flow battery use in long duration storage is growing. Most conventional flow batteries use two electrolyte liquids: one with a negatively charged cathode, and one with a positively charged anode. The cathode and anode are separated into two tanks by a membrane, because if they come into contact with each other the battery will short and require replacement. This is often what happens with lithium-ion batteries; the membrane degrades over time. But the exchange of negatively and positively charged fluids in flow batteries produces electrical current without degradation, providing a longer cycle life and quick response times. Cost: When looking the levelized cost of storage, flow batteries often come out on top in long-duration storage applications over lithium ion. This is due to their ability to last decades with little maintenance and the fact that the electrolyte materials can be reused or sold.

Replacement/maintenance: Lithium-ion batteries can be lighter and more self contained than lead-acid batteries, so may be easier to install and change out. They can be wall-mounted and located indoors or outdoors. They are solid, so don’t require refills or maintenance.



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Replacement/maintenance: The flow battery’s membrane degrades little over time, allowing flow batteries to last much longer than other technologies. Flow batteries also require little maintenance. With other technologies, adding more batteries is the only way to increase hours of storage. A benefit of flow batteries is that you can increase storage capacity by simply adding more electrolyte. Cycling: Flow battery developers say the technology has no cycling limitations, and batteries can be charged and discharged completely without impact on their lifespan. Disposal: Though it depends on the chemistry, flow batteries tend to be less reactive and easy to dispose, with no fire risk. Many times the electrolyte is able to recycled, which helps lower the levelized cost of storage for flow batteries. Nickel cadmium Nickel cadmium or NiCd batteries have been around since the early 1900s. Though they may not have the energy density (the power) of other technologies, they provide long life and reliability without complex management systems. Cost: Nickel cadmium is relatively inexpensive compared with other technologies. Replacement/maintenance: NiCd batteries are vented to allow gases to dissipate. They traditionally require some watering, but new designs allow the gases to recombine to form water which makes the battery nearly maintenance free. This, along with the ability to tolerate extreme temperatures, makes these batteries ideal for off-grid applications in harsh environments. They have been used for storage in megawatt-sized projects. . Cycling: NiCd batteries are rugged batteries with a high cycle life. Some companies promise a service life of up to 20 years.

A flow battery. (Photo credit: ESS Inc.)

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Disposal: Cadmium is a hazardous material. In fact Europe limits the applications NiCd batteries can be used in. Toxic materials must be removed before the battery is disposed of. NiCd batteries can be recycled, however. The cadmium can be extracted and reused in new batteries. The nickel can be recovered and used to make stainless steel.



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HOW TO MAXIMIZE DEEP-CYCLE BATTERY PERFORMANCE IN RENEWABLE STORAGE SYSTEMS REGULAR BATTERY MAINTENANCE FOR ENERGYSTORAGE SYSTEMS used with renewable-energy (RE) applications is critical for maximum system performance. Batteries in RE systems should be engineered for deep-cycle use, meaning the battery’s design is optimized for the deep discharge and recharge cycles characteristic of RE systems, especially in support of the variable power production from wind and solar equipment. Deep-cycle batteries fall into two groups: flooded lead acid (FLA) and sealed valveregulated lead acid (VRLA), such as Absorbed Glass Matt (AGM) and gel. To achieve maximum life, each battery type requires particular care.

The temperature of a battery’s electrolyte is taken by hydrometer to obtain an accurate and specific gravity value. If the hydrometer used is unable to automatically compensate for temperature, the specific gravity reading should be corrected manually to a standard temperature of 80°F. To correct specific gravity readings for temperature, add 0.004 for every 10°F above 80°F and subtract 0.004 for every 10°F below 80°F.

FLA batteries When deep-cycle flooded batteries charge, they produce and vent hydrogen gas. This “off gassing” of hydrogen reduces the battery’s electrolyte level, which requires periodic “watering” of the battery (with distilled water) to ensure maximum life. It is important to add distilled water only when the batteries are fully charged in float mode, which is when the charge current and voltage are reduced to maintain a full battery. Although variations exist between manufacturers, electrolyte levels should never be allowed to drop so low as to expose the battery plates to air. While monthly watering is typically recommended, the ideal frequency depends on how the batteries are used and the operating temperatures of the battery bank. Bearing this in mind,

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By Vicki Hall, director of global technical services; Trojan Battery

careful monitoring of new installations is key (say, once a week to start) to determine the correct frequency of watering required. As flooded batteries age, their gassing rate will increase requiring more frequent watering. However, regardless of the amount of watering a battery bank receives, it is important to do so on a regular schedule. Equalization is also an important part of maintaining the longevity of FLA batteries used in RE systems. The process for equalizing FLA batteries involves periodically overcharging the batteries at a higher voltage for a set period of time to reduce the effects of electrolyte



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PUTTING SAFETY FIRST Effective battery maintenance for peak system performance and longevity means committing to a regular maintenance schedule. With FLA or VRLA deep-cycle batteries, it is important to adhere to similar safety and maintenance tips. • Always wear protective clothing, gloves, and goggles when working with batteries. The electrolyte in a flooded battery is a solution of acid and water, so take extra precaution to avoid contact with skin and clothing. • Check that all cable connections to the terminals are properly tightened—connections that are too tight or loose may result in post breakage, meltdown, or fire. • To safeguard against short-circuits, use only insulated tools when maintaining batteries. • Avoid placing tools or objects on top of the batteries. • Charge batteries in a well-ventilated area. • Clean battery tops and terminals with a solution of baking soda and water, and dry thoroughly. • Apply a thin coat of petroleum jelly or terminal protector spray to terminals. • Never add acid to a battery.



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ENERGYSTORAGE stratification (the accumulation of sulfuric acid at the bottom of a battery cell), sulfation (the formation of deposits in the active battery material), and other battery cell inconsistencies that develop over time. Stratification and sulfation typically occurs when a battery is deprived of a full charge. If left unchecked, these conditions eventually diminish the overall efficiency and performance of the batteries. VRLA batteries Although equalization is an important maintenance procedure for FLA batteries, the same is not true for VRLAs. VRLA batteries should never be equalized because they are incapable of properly venting excess hydrogen produced in the process. VRLA batteries are typically referred to as maintenancefree because of the minimal amount of maintenance needed to function reliably. Because VRLA batteries are sealed, adding distilled water is unnecessary. However, it is important to check VRLAs regularly for terminal corrosion. In addition, such batteries should be cleaned to remove dirt or dust that accumulates on top of their surface. State of charge Evaluating the state of charge (SOC) of a FLA or VRLA battery bank is a necessary maintenance procedure. To conduct an SOC check, simply take an open-circuit voltage reading of the battery bank using a voltmeter. For FLA batteries, it is possible to use a hydrometer to take specific gravity (SG) readings of individual cells. Both voltage and SG readings should be taken under a “no load” battery condition to ensure accuracy. It is wise to refer to the battery manufacturer’s user’s guide to determine proper equalization and SOC methods, and measurements required for each specific battery configuration. With proper care and maintenance, deep-cycle batteries are more likely to achieve the manufacturer’s optimum design life, extending the battery investment and keeping the total cost of ownership to a minimum.

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THE UNITED STATES HAS YET TO PLANT MORE STEEL IN THE COASTAL WATERS since erecting the five-turbine Block Island wind farm. That

project, a few miles south of Rhode Island, is an industry first for the nation. While the impatient ones among us would like to see more construction, we recognize that development plans and approvals are moving ahead at a considerable pace. For instance, North and South Carolina are conducting aerial digital surveys of offshore wildlife in preparation of future wind-farm development. Massachusetts signed a bill to procure 1,600 MW of offshore wind-generated power. New York State set an ambitious goal of generating 2.4 GW from its offshore resources by 2030. In fact, a recent report suggests that the Northeast has potential for 4,000 to 8,000 MW of offshore wind projects by 2030, and that would translate into about 36,000 jobs. Currently, the wind industry employs over 102,000 people across all 50 states, and that number may be on the rise. Data from the Bureau of Labor Statistics shows that over the coming decade jobs as wind technicians (and solar installers) are projected to grow faster than any other job category in the United States. The number of workers in these professions is expected to double between 2016 and 2026. This makes sense because although the production tax credits are ramping down each year (the PTC is in a five-year phasedown that began December 2015), the wind industry has been gearing up in capacity. As of the end of the third quarter of 2017, U.S. wind projects under construction and in advanced development have reached 29,634 MW. That is at the highest level since this statistic was first measured at the beginning of 2016, according to the American Wind Energy Association (AWEA). “The high level of wind under construction and in advanced development shows we are on track to deliver 10% of America’s electricity by 2020, along with $85 billion in economic activity and 50,000 new jobs,” says Tom Kiernan, CEO of AWEA. And with the advancement of the offshore market, there is potential to surpass that goal. Bigger and smarter turbine development is also pushing the wind industry forward. MHI Vestas, for example, recently announced its most powerful turbine to date: the V164-9.5 MW. The 9.5-MW’s gearbox and main bearings are currently undergoing testing and verification at Clemson University in South Carolina. Wind turbines that can predict the weather and communicate their “health” conditions to each other and an offsite command center are also proving valuable. This is thanks to advanced condition-monitoring systems, digital sensors, and the industrial Internet of things. GE Renewable Energy’s Digital Wind Farm, for example, lets wind owners collect and analyze turbine and site-level data to optimize maintenance strategies and increase annual energy production. Goldwind has also unveiled a “smart turbine,” and Bachmann electronic introduced controls that would raise the IQ of an average wind turbine. Such advancements are driving down the cost of production. Wind energy is one of the most affordable forms of electricity today, ranging from about $32 to $62/MWh. Utilities, consumers, and private industry are taking notice. The end of 2017 saw Fortune 500 companies and others buying wind power for the first time. According to AWEA’s third-quarter report, the first-timers include major manufacturers such as Cummins and Kimberly-Clark. Target, General Motors, and Google also became repeat customers by signing additional PPAs. “The wind industry is propelling American energy production, manufacturing, and job creation into the 21st Century,” said Kiernan. This is good news for Americans and a clean-energy nation. WPE&D ESN

the rise of wind power in



Windpower Engineering & Development @michelleforwind



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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 2017 data from its continually updated meteorological dataset with 30-year averaged conditions from the same dataset.


Q1 Q2



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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 states for cumulative wind capacity through Q1 2017 Texas (21,044 MW) Iowa (6,952 MW) Oklahoma (6,645 MW) California (5,656 MW) Kansas (4,931 MW)

Top states in total new wind capacity in 2016 Texas (2,611 MW) Oklahoma (1,462 MW) Iowa (707 MW) Kansas (687 MW) North Dakota (603 MW)



Top states according to percentage of wind generation Iowa (36.6%) South Dakota (30.3%) Kansas (29.6%) Oklahoma (25.1%) North Dakota (21.5%) S S

Top states receiving Rural Energy for America Program (REAP) energy efficiency grant funding for wind projects (since 2003) Iowa ($23.3 million) Minnesota ($21.2 million) Illinois ($4.1 million) Ohio ($2.9 million) Oregon ($2.8 million)

Offshore wind demonstration projects that have obtained site control from federal or state authorities BIWF (Rhode Island) Aqua Ventus I (Maine) Dominion/DONG Energy (Virginia) Fred Olsen/LEEDCo Icebreaker (Ohio) Fishermen’s Energy Atlantic City Windfarm (New Jersey)



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Top states for offshore wind project pipelines

Top states for number of wind turbines

Massachusetts New Jersey North Carolina Virginia Hawaii

Texas (12,077) California (7,465) Iowa (3,976) Oklahoma (3,394) Kansas (2,795)

Wind jobs in 2016 Texas (23,000) Iowa (9,000) Oklahoma (9,000) Colorado (7,000) Kansas (6,000)




















TX Sources: Information from AWEA, Department of Energy, NREL

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1 2

Wind sensors (mechanical and ultrasonic) Radiators and exhaust fans

3 Nacelle walls (fiberglass) 4 Induction generator



Slip rings

Bed plate

6 Vibration isolator

7 Generator blower 8 Obstruction light 9 Air filters

10 Inverter, standby power, and electrical connectors 11

Disc brake

12 Coupling and torque limiter 13 Yaw bearing

Motors Gears

14 Bearing


15 Multi-stage gearbox 16 Fire suppression

17 Electrical control 18 Main shaft

19 Fans for oil cooling 20 Pitch controls

21 Pitch bearings


22 Main-shaft bearing 23 Bolts

24 Tower

(with cables lifts, ladders, and lighting)

25 Blades



26 Hub hatch

27 Safety rails

28 Nose cone (fiberglass) 29 Hub hydraulics 30 Hub (casting) 22


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Suzlon 9X 2.1 MW

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A blast from the past. Here is an example of a two-parallel stage gearbox design, typical of a mid-1990s wind turbine.

AS UTILITY-SCALE WIND TURBINES HAVE DEVELOPED from the kilowatt-class to the multi-megawatt machines installed today, the components inside a nacelle have also evolved to keep up with new power demands. Drivetrains, in particular, have had to change significantly to meet stronger, more variable wind loads and higher power levels—and without significant increases in costs. So, engineers took on the challenge, and manufacturers delivered. What was once an off-the-shelf, industrial gearbox is now uniquely designed to meet the harsh conditions typical of a multimegawatt turbine. A modern geared turbine typically has a threestage gearbox with a low-speed planetary stage and two parallel stages. By using planetary gears, designers created high-powered


By Dr. John Coultate, head of engineering development, and Mike Hornemann, reliability engineer; Romax InSight

gearboxes that are durable enough to withstand harsh loading, yet compact enough to maintain a reasonable nacelle size. This gearbox design has also proven economical for turbines with power ratings between 500 kW and 2.5 MW. However, longevity is the one challenge still unmet in the wind-turbine gearbox industry. Turbine gearboxes are typically given a design life of 20 years, but few make it past the 10-year mark. Why the discrepancy? Part of the answer is in the way that gear and bearing lives are defined. The life of a gearbox component is stochastic, not deterministic. This means that it is impossible to predict with accuracy when a component will fail, even though it is possible to estimate the probability given certain parameters. Keep in mind that wind-turbine drivetrains undergo severe and variable transient loading during start-ups, shutdowns, emergency stops, and grid connections. A turbine’s loading depends on its location in the wind farm and the terrain. Load cases that result in torque reversals may be particularly damaging to bearings because rollers may skid during the sudden relocation of the loaded zone. Micropitting, a form of surface fatigue, is one example of damage in bearings that can affect its longevity. The life of a bearing is generally defined as the “L10” life, which is the duration after which 10% of the bearings will fail. If L10 for one bearing is 20 years, then there is a 10% chance that the bearing will fail in fewer than 20 years. This is important because it forces manufacturers and wind operators to think about “lifetime” in terms of probabilities. It is also important to consider that a wind turbine has more than one bearing. A typical drivetrain has 20 to 25 bearings, including the main bearings, gearbox, and generator bearings. So, what happens if we combine the L10 life for every bearing in a drivetrain to calculate a “system-level life?” A simple calculation for a drivetrain with 25 bearings, all with an L10 design life of 20 years, indicates that the probability of one or more bearings failing within 20 years is 93%.


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A typical wind-turbine contains 20 to 25 bearings, all of which must be considered in a system-level reliability calculation of life expectancy.

Based on this calculation, nearly all gearboxes in a wind farm are likely to fail within 20 years. This may seem shocking, but it is a reality in the field. Many wind operators will attest that most gearboxes have been changed or gone through an uptower repair of some kind, such as a new high-speed stage shaft or bearings, long before its 20-year life is up. Now let’s ask how many gearboxes will fail within seven years? The same calculation indicates that the probability of one or more bearings failing within seven years is 37%. This means more than one-third of gearboxes will suffer some sort of bearing failure. These results come from a simplified calculation and are only intended to show overall trends, but they show some startling findings. Unfortunately, the calculation can under-estimate gearbox failure rates because it fails to account for nonfatigue failure modes. But the good news is that, in practice, some bearings offer a design life in excess of 20 years because their size is dictated by other factors, such as stiffness or safety factors during extreme load cases.

This is why the term “design life” is misleading, and one reason why many gearboxes in the field are failing in fewer than 20 years. One way to mitigate these failures is to employ more reliable engineering methods throughout the entire lifetime of a turbine. For example, using design standards and simulations, along with reliable operational data and historical failure rates, it is possible to provide accurate predictions of drivetrain failures.


A modern-day design. This three-stage (planetary/parallel/parallel) design is common to more recent gearboxes.



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High Speed Shaft Solutions

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WHY POWER CABLES NEED MORE ATTENTION THAN THEY GET By Paul Dvorak, editor; Windpower Engineering & Development

YOU’LL BE FORGIVEN IF you think that cables are a “set and forget” type of component. Not so. In truth, cables in wind turbines must tolerate abrasion from vibration, oil on insulation, and remain flexible to a bone-chilling -40°F—and more. Then as the wind industry becomes more digital, it calls for more data from more sensors, which require more connectors. But as things have gotten more complicated, the industry has responded with new products and updated standards, which will guide industry growth. In fact, a recent report from Research and Markets forecasts the growth of the global wind-power cables market at a compounded rate of about 7% from 2017 to 2021. Here are a few recent cable and connector developments, and outlooks that will drive that growth. Tolerating cold Electrical cables are exposed to harsh temperature extremes where low and high-temperature fluctuations affect a cable’s performance. Cables are now tested in accordance with UL, CSA, and NEC standards for applications that require bending in cold temperatures down to -40°F (-40°C). Cold bend tests determine how the entire cable (conductors, insulation, and jackets) might react to cold-temperature bending. For the test, cable samples are cold soaked to a specified temperature for a number of hours. After the cold soak period, the samples are wound around a steel mandrel determined by the cables’ outer diameter. After winding, a cable is removed and examined for surface damage, such as cracks, splits, and tears. The cable passes the UL cold-bend test when there is no visual surface damage


and further electrical test reveal no other issues. One cable manufacturer says a recent design has successfully surpassed two tough mechanical tests to ensure its safety and performance capabilities in wind turbines found throughout North and South America. HELUKABEL says its TRAYCONTROL X has passed the UL -40°C Cold Bend Test and a torsion test of 10,000 torsion cycles. Testing by twisting Electrical cables exposed to continuous movements and vibration force them into near constant flexing, which produces mechanical stresses in them. This can degrade their performance and lead to failure. One place this

Passing 10,000 cycles in a torsion test is significant because it exceeds the torsion lifecycle requirements from all of the global wind-turbine manufacturers. The recent TRAYCONTROL X cable from HELUKABEL is a NFPA 79-compliant flexible control power cable with cross-linked (thermoset) polyethylene insulation. It works in dry, humid, and damp environments, in pipes, underground, and for open, unprotected installation within the turbine. The cable is rated for use in 1,000-V wind-turbine cable tray applications.


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WINDPOWER occurs is in the tower. As a wind turbine’s nacelle rotates, cables in the loop twist and tighten onto one another. This places torsional stress on the cable’s components at every level—conductors, jacketing, and insulation. To test new designs, one cable manufacturer operates an R&D lab that duplicates a section of a wind tower big enough to test a full-sized cable in a drip loop. The tower-lab also allows exposing cable to various climates. A cycle in the twist test is defined as a 1,080° (360° x 3) rotation in either direction (clockwise and counter). The rotation rates allow for up to one cycle per minute. After reaching a required cycle count, cables are inspected for visual defects, such as abrasion and cracking, and internal components are examined for signs of failure, such as conductor strand breakage. Wear in the loop The drip loop is that bundle of cables responsible for carrying power, data, signals, and communication for everything generated inside a nacelle. The loop is needed to provide slack for the turbine to yaw a few revolutions as it works to face the wind. While the cables in this loop meet windindustry standards (for torsion, oil resistance, and temperature), current industry practice of tightly bundling them has serious impacts. The biggest problem with closely arranging cables in this manner is there can be as many as 16 of them tightly bound together, twisting and rubbing against each other. This arrangement creates excessive heat and wears down the jacket insulation, ultimately exposing a cable conductor that


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can carry from 600 to 1,000 V. This wear can appear only a few months after the start of operations but is often missed or overlooked during end-of-warranty inspections. One solution to cable abrasion in drip loops comes from the collaboration of three companies headed by Lapp USA, a global cable manufacturer. The SOHL (from company initials) provides a range of modular clamps and sections to keep cables from rubbing against one another. One device, informally called the snowflake star clamp, serves as a multi-function, engineered cable gland and management system for drip loop applications. The device keeps cables sufficiently separated to prevent them from wearing each other’s insulation.

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The compact modular design of the SOHL allows for proper heat dissipation to keep cables cool for maximum efficiency and to avoid excess wear in the insulation. The number of units needed per drip loop is turbine-specific.

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HOW TO CHOOSE THE RIGHT BRUSH FOR YOUR WIND TURBINE By Neel Sheth, wind-power application engineer; Mersen

BRUSHES PLAY AN IMPORTANT ROLE IN WIND-POWER GENERATORS. A brush is an electrical conductor subject to friction. It works as a mechanical and electrical component that has the function of transferring a current (ac or dc) between the rotating part of a machine and its fixed external power supply or power converter. A brush is typically expected to operate efficiently within a wide or narrow range of speeds and electrical loads. How it performs, however, depends on the brush material (also called brush grade) and the system assembly. Choosing a brush for an application consists of best matching its mechanical and electrical properties to the operating conditions of the machine. Although a relatively small component, the performance of brushes in wind-turbine generators is key to efficient operation.

Slip-ring profiles obtained using an advanced digital profiler tool. The diagram above shows an almost perfect ring, while the one below shows a damaged ring in need of immediate attention. Advanced digital tools are available on the market to analyze slip rings and provide outputs as shown.

What makes a good brush? A good brush must have a set of electrical and mechanical properties, some of which are more important than others. Two essential properties include reliable wear and compatibility with the slip ring. 1. Moderate wear: A brush is a wear item—a consumable. That means it has a minimum life, which is important to note for its intended application to best optimize replacement schedules and maintenance intervals for the rotating machine. Excessive brush wear typically causes carbon dust generation in the slip-ring cabinet, which increases the risk of reduced internal insulation. This may lead to additional maintenance costs and the risk of an arc flash (also known as a flashover), as a result of the phase-to-phase conductive dust covered surfaces in the slip-ring cabinet. Moderate or adequate brush wear is key to proper generator and wind-turbine O&M.


2. Slip-ring compatibility: A brush must maintain a good surface finish of the slip ring on which it’s operating. The surface finish must remain stable so there is no diminishing of brush performance over time. This includes surface roughness and runout (which is the shape profile or “roundness”) of the slip ring. Unfortunately, repair or replacement costs of a damaged slip ring are high and can cause unexpected shutdowns and equipment downtime.


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Finding a match A quality brush application must also consider the slip ring’s material. This is because a good brush features a long life without damaging or wearing into the slip-ring surface. Together, the two components must work together while minimizing wear of the brush and slip ring. The optimum brush is found when its mechanical properties match the specific application without compromising a slip ring, and while fulfilling its electrical requirements. A damaged slip ring may be a sign that the brush used is unsuited for the application. Damage detection An improper brush can damage its slip ring. The most frequent damages and their root causes are: 1. Slip-ring wear: Optimizing metal content and material hardness of the brush material is critical. Improper spring tension or an excessively hard brush grade can cause high friction at high speeds, and cause slip-ring wear by mechanical abrasion. Therefore, spring tension and metal content of a brush slip-ring system is an important consideration during the design stage. 2. Abnormal temperature rises: If the temperature of a brush or slip ring exceeds the manufacturer’s recommendations, damage is likely to occur. This could happen because of a mechanical issue (such as high friction) or an electrical issue (such as electrical loads exceeding the current carrying capability of the brush).

3. Arcing, burns, or micro-pitting: These are indications of fatigue failure on the surface of a material, typically seen in rolling bearings and gears, although they also show up in slip rings. Such wear typically means a brush is unable to handle the electrical loads, or that the brush material or the surface of contact between the brush and the slip-ring are incompatible. This electrical phenomenon can cause local or repetitive deformations. It can also do worse damage and destroy the slip-ring surface, making it abrasive to the brush and resistive at the same time. 4. Slip-ring deformation: This happens when a slip ring is “out of round,” which can occur on both phase and ground rings. On grounding applications, shaft currents leaking into the grounding system can lead to rapid slip-ring deformation when the application uses an improper brush grade. High-frequency ground discharges act as electric discharge machining on the ring, causing low or flat spots on the ring over time. This phenomenon is often referred as ghost marking. Slip-ring design Choosing the right brush for the application is only part of the answer for the best brush and slip-ring performance. The proper slip-ring design is just as critical.

As the system temperature in a wind-turbine generator increases abnormally, the risk of excessive wear increases for the brushes and slip rings. This may lead to arcing from the brushes to the ring or across rings—from phase-to-phase or phase-to-ground. Incorrect system design can also contribute or accelerate the failure rate on these components. This flow chart shows the relationship between various factors, which affect slipring temperature and the general condition of a machine.



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A number of slip-ring designs are currently available for windenergy applications. Design criteria should account the electrical loads (rotor current loads) of the turbine generator. The generator rotor electrical loads, in comparison with the targeted slip-ring S-factor (surface factor), define the slip-ring sizes required for an application. The S-factor is a simple key design factor used by experts to accurately size slip rings for a machine. It is calculated as a ratio between the slip-ring surface width over the nominal current, and is directly correlated to heat dissipation factor of the system. This S-factor co-efficient can be used to quickly evaluate the degree of difficulty of a motor or generator, and guide installers to the right brush grade for the application. A brush-slip ring manufacturer should use this outline as the basic design guide when designing or customizing systems for today’s highly demanding applications. The choice in ring material or design of slip-ring ventilation directly affects the acceptable S-factor requirements. A well-ventilated bronze slip ring would typically offer better performance than an equivalent sized stainless steel ring with poor ventilation, even when featuring the same S-factor. Bronze generator slip rings are becoming more common in the wind industry, and were introduced as replacement components for the original stainless steel versions. Bronze slip rings for generators significantly improve the overall performance of these systems. In fact, brush wear rates and operating temperatures drop by as much as 30 to 40% when a slip ring is correctly designed based on these factors. The ideal brush Motors or generators (synchronous and asynchronous), and all rotating systems using slip rings, employ technologies that are different from those used on dc motors. The technological requirements also differ. Many factors come in consideration when choosing the right brush grade, such as:


• The slip-ring design: Alloy, size, and helical groove • The brush-holder design: Number of brushes and coverage ratio of the ring • The system design: Current loads, rpm, spring pressure, and ventilation A detailed understanding of a heat source or hot spot in a brush slip-ring system is necessary before identifying a heat dissipation method. Of course, this method depends on system size. Therefore, it is important to consider the brush grade and design along with the slip-ring design. The choice of metal content (typically copper) is also an important consideration. Brushes that wear evenly across all phases indicate good performance over a given set of operating conditions. The brushcontact-surface aspect is also a good performance indicator. Pitting marks or heavy streaking on the other hand, are signs of overload or grade mismatch. There is a wide range of brush grades for slip rings, and the metal content can vary from 0 to more than 90%. The number of brushes and brush sizes needed in a system is determined by the current load to transfer. The current capability of the brush grade chosen is typically quantified in terms of “current density” (amps/cm²). The higher the metal content of a brush grade, the higher the current density (or current capability), but the lower the peripheral speed of the slip ring. The metal content in the selected brush should be inversely proportional to machine speed. Based on the intended application, manufacturers normally recommend a speed range for a brush grade. In summary, the application’s component wear and operating temperature indicates whether the brush grade is appropriate.


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3 2

1 4


ABOUT EVERY 10 MINUTES IN THE UNITED STATES somebody gets hurt from something falling. That “something” is typically an object or tool from a construction site, which may be at a wind farm. Effective fall protection requires a combination of products working together, often described as the ABC’s of fall protection. The anchorage connector, body support, and connecting device — form a complete fall-protection system for maximum worker protection. However, it is also important to remember D, E, and F, the other significant components of a comprehensive safety program: descent and rescue, education, and fall protection for tools. Craig Firl, Technical Manager at 3M, has put together a list of the basics that all wind technicians and employers should know to keep workers safe while working at height. •


Download an easy-to-follow checklist for the inspection of fall protection equipment at

1. D-rings, O-Rings, and Oval Rings must withstand a minimal tensile load of 5,000 lbs without breaking 2. Buckles and Oval-rings used as adjusters (as well as other adjusters) must withstand a tensile load of 3,372 lbs. 3. Straps must be 1-5/8 inches or wider and be made of synthetic materials with finished edges 4. Stitching on straps must be contrasting in color to the load-bearing straps to help facilitate inspection

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Contributed by 3M

Anchors: The secure point of attachment for the fall-arrest system. The appropriate type of anchorage connector varies by industry, job performed, type of installation required, and the available structure. It is essential to ensure the anchor chosen is correct for the task at hand. Body harness: The best way to achieve body support while working at height. Ideally, a harness will distribute fall forces over the upper thighs, pelvis, chest, and shoulders to lessen the impact on an individual body part. It is important to inspect your harness before each and every use. Check for wear, excessive corrosion, burns, or other damage. Connectors: A device that links a user’s full-body harness to an anchorage point. When used as part of a fall-restraint system, the length of the connector must be carefully selected so a worker is safely restrained or prevented from reaching a fall hazard. Descent & rescue: Decent and rescue devices are used to retrieve a worker who has fallen. Such devices include tripods, davit arms, winches, and comprehensive rescue systems. Choosing the right descent and rescue equipment depends on the jobsite, the task being performed, and the available workforce. Education & training: The effectiveness of fall protection gear, no matter how durable or reliable, is compromised when workers fail to use it correctly. That’s why contractors should enlist a training program or specialist to show workers not only what tools to use, but also how to use them. Fall protection for tools: For all objects at height, it’s not about catching the object — it’s about preventing things from falling in the first place. When using fall-protection equipment for tools, it is important that lanyards, attachment points, and wristbands allow a worker unrestricted movement and to use the tool with little or no interference.

The safety standards discussed reference the American National Standards Institute (ANSI) and the American Society of Safety Engineers (ASSE) requirements that are a part of the ANSI/ASSE Z359 fall protection code. These standards are copyright protected documents but can be purchased at



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FIRST-TIME WIND DEVELOPERS: WHAT TO KNOW BEFORE YOU BUILD By Jay Haley, PE, principal in charge of wind energy; EAPC

Know the opposition. Establishing strong local connections and community support for a wind project is often the best way to anticipate and avoid opposition that may threaten land leases, project permits, and wind-farm financing. Permitting bodies also tend to look more favorably upon projects that have strong local support and participation, so being proactive can successfully impact a new wind project.

SO YOU’VE FOUND AN IDEAL LOCATION TO BUILD A WIND FARM and are considering life as a wind developer. How difficult could it be, right? Before jumping into the industry with both feet, first consider the many phases and nuisances involved with moving a wind project forward. Wind development comes with 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, costs, and potential pitfalls when developing a wind farm. Development phases Wind-farm development is a complex process. As a project progresses through the various stages of development, there are many opportunities for mistakes that can seriously affect the final


outcome and success of a wind farm. In fact, some of the biggest mistakes in wind development begin in the early stages and are difficult to overcome as the project progresses. The typical phases of wind-farm development are: • Prospecting and land securing • Wind-resource assessment • Interconnection and transmission studies • Wind-farm design and permitting • Power purchase agreements • Financing • Procurement • Construction and operations.


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Poor site selection is all too common with new developers. Sites are ill chosen for the wrong reasons, such as location preferences, or without sufficient due diligence. Typical problems that arise from poor site selection include: • • • • • •

Landowner issues Less than adequate wind resource Lack of access to transmission (or no capacity on existing lines) Lack of an off-taker for the power Constructability issues Fatal permitting issues.

Data collection Depending on the size of the project and the complexity of the terrain, a number of site measurements are necessary to validate wind flow. A financeable wind-measurement campaign includes proper selection of measurement locations and heights, a reliable measurement instrument, and an equipment maintenance plan. Also needed: a high degree of data recovery and thorough documentation. Most investors and banks require a minimum of one year of onsite wind data before either will consider financing a project. Most turbine manufacturers have the same requirement. An independent engineer is typically asked to verify the wind regime and energy projections prior to financial closing, so the wind measurement campaign must be thoroughly Build smart. documented and the met When building a towers precisely installed new wind farm, at a potential development some of the site. Installation details most challenging issues occur in such as tower location, the early planning mounting heights, boom and construction directions, instrument stages. New models, serial numbers, developers should spend time on calibration coefficients, research and due and site photographs diligence before are all necessary for the committing to their independent engineer to first wind project. (Photo credit: perform his or her task Joy Powers) accurately. Permitting standards Permitting is an expensive part of a wind-power project, and requirements vary from state to state and from county to county. One missed step can


quickly jeopardize or halt a project from moving forward. For example, regulations are often changing with regards to bats, eagles, migratory flyways, and endangered species or regions, so keep up with the latest rules and bylaws. The size of wind turbines—which has gotten larger and taller of late—is also an important development consideration. Setbacks from occupied structures have increased due to noise and shadow flickering concerns, which may eliminate some of the developable area. Turbine choices 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. The type of measurement instrument selected is also important, and quality counts. Lower quality instruments can result in poor data and higher uncertainty in the wind regime. This, in turn, can lead to significantly higher financing costs, many times more than the amount saved on cheaper instrumentation. The type of wind turbine selected is also crucial to achieving a successful and financially viable project. All turbines are not created equal. Some turbines match up with the wind resource better and, therefore, produce more electricity than the others. Some turbine types will have higher upfront costs, while others may have higher operations and maintenance costs. All such factors need consideration prior to selecting the best turbine model for a project. Buyers wanted If you intend to sell power to a local utility once the wind farm is up and running, it is a good idea to open up a dialog early on. It is also important to research the local infrastructure, proposed upgrades to transmission systems and substations, long range plans for large transmission projects, and the overall system operations for that region. As more and more wind farms are built in an area, the possibility of being curtailed due to transmission congestion becomes more likely and will affect the financial viability of the project. The late stage of project development is a less than ideal time to learn there are no interested buyers for the output from the wind farm—and this does happen from time to time. The reason? There are several including political changes that affect the market, interconnection or transmission issues preventing access to the market, or unrealistic expectations regarding the anticipated power pricing. It cannot be overstated: Proper due diligence in the early stages of a wind project can help avoid costly mistakes and disappointment down the road.


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HOW SIMULATION SOFTWARE IS IMPROVING THE WIND INDUSTRY By Michelle Froese, senior editor; Windpower Engineering & Development Pacific Northwest National Laboratory’s ThermalTracker software analyzes thermal video taken night or day, which could warn windfarm operators of birds or bats in the vicinity. PNNL engineers Shari Matzner and Garrett Staines discuss their development of the software while doing field research near Sequim Bay in Washington. (Photo credit: Eric Francavilla, PNNL)

ADVANCES IN WIND-TURBINE DESIGN AND OPERATION over the past few years have improved several bottom lines making wind energy more efficient and affordable than ever. Although much of this can be attributed to what’s visible—the innovative components and hardware that go into these machines—much credit should go to what’s behind the scenes—the engineering software that guided the design. Software simulations and analytics are helping manufacturers and operators maximize wind developments, and now researchers are benefiting, too. For example, until recently much focus was on how to improve the performance of individual wind turbines through comparative analytics and programs that assessed turbines under different loading and weather conditions. But researchers from the National Renewable Energy Laboratory (NREL) decided to look at the bigger picture and the performance of a wind farm as a whole. In a recent paper, the research was labeled: “The butterfly effect at wind-farm scales.” This effect refers to the concept that small causes can have large effects or that small occurrences (say in one wind turbine) can impact a larger scale (an entire wind farm). Upon accumulating and analyzing the data, the NREL team found that “optimizing yaw control and the relative positioning of individual turbines improved the power performance of downstream wind turbines by mitigating the interference that wind turbines in an array have on each other.” This is important insight for developers deciding on the optimal placement of turbines in a farm. The researchers were able to make this conclusion, thanks to the design and

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development of “Simulator fOr Wind Farm Applications” (or SOWFA), a coupled open-source software platform and framework. SOWFA lets users investigate the effects of weather patterns, turbulence, and complex terrain on the performance of turbines and wind farms. According to NREL, such software also lets engineers and scientists understand the causes of wind-farm underperformance, increase a project’s power output and decrease the effects of structural loads to minimize wear on turbine components. Additionally, SOWFA lets turbine manufacturers study designs before they are manufactured and allows developers to assess the performance of turbines on a proposed site before construction. Here are a few other examples of how focused engineering software is pushing the wind industry forward: Bladed modeling As the primary simulation tool in the design of about half of the utility-scale wind turbines manufactured worldwide, DNV GL’s Bladed wind-turbine modeling software has recently undergone a transformation to improve its outputs and user experience. The design of a turbine is fundamental to its function and productivity. Failure to correctly model loads, structural integrity, or even the environment—and perform accurate testing—can jeopardize the long-term safety and reliability of a turbine. Accurate modeling of a wind turbine is essential.



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“Wind-turbine modeling in the design phase is incredibly important,” said Patrick Rainey, Bladed product manager for DNV GL. “If a design isn’t accurately tested and a failure mode not detected, then the final operational design could encounter serious problems and cost a manufacturer in terms of reputation, lost revenue, and the time to find a solution.” Thanks to Bladed’s new 3D animation graphical environment, designers can now view simulated turbine behavior from any angle by “panning” around a threedimensional model. The new Multipart Blade non-linear structural model reduces uncertainty in blade vibration predictions, and the Result Animation, gives users insight into turbine performance via a simulated scenario. Project siting The Rocky Mountain Institute (RMI) and its Business Renewables Center (BRC) have launched a new software platform that helps buyers and developers of renewable projects better understand which locations are more likely to be economically attractive across deregulated electricity markets in the United States. The platform was built using publicly available data from market operators, a levelized cost of energy calculation, and a proprietary algorithm to model hypothetical project revenue. BRC’s market analysis platform produces an estimated “value” calculation for about 4,300 nodes, or grid-connection points—across all seven U.S. independent system operators covering 39 states. “In 65% of the U.S., it’s possible to source wind and solar directly but, much like real estate, these renewable energy deals hinge on location, location, location,” said Hervé Touati, managing director at RMI. “At the Business Renewables Center, we are working to educate business leaders with insights on economic value that help buyers and developers build better projects in ideal locations.” This software tool, currently available to members of the BRC, aims to help buyers and developers of renewable projects build a more complete picture of wholesale electricity market economics, based on real price histories for individual grid-connection locations.

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Thermal tracking Researchers at the Department of Energy’s Pacific Northwest National Laboratory (PNNL) are developing software to track birds and bats near offshore wind projects. The platform, called ThermalTracker, automatically notes and categorizes birds and bats found in thermal-imaging video. “Birds and bats fly over offshore waters, but they’re difficult to track in such remote locations,” said PNNL engineer Shari Matzner, who leads the project.



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Analysis tools, such as those offered in DNV GL’s Bladed windturbine modeling software, can assist engineers in the design of more reliable turbines, with lower modeling costs and in shorter periods.

The software can help determine if there are many birds or bats near a proposed offshore project, and if they could be affected by development. If that’s the case, developers can consider adjusting the location of a the project or even modifying an existing project’s operations. “ThermalTracker can help developers and regulators make informed decisions about siting and operating offshore wind projects,” said Matzner. “We need scientific tools like this to better understand how offshore wind turbines can coexist with birds and bats.”

two can pass notes virtually (via text), and telestrate or draw on the video screen.” A telestrator is a device that lets its operator draw a freehand sketch over a moving or still video image. Neagoy said the software can also integrate within existing workflow processes and build a saved knowledge base that leverages expertise as part of the Internet of things. “So when a similar problem occurs in the future, the answer is available and only a click away.”

Connecting experts Imagine that during a routine wind-turbine inspection, a wind tech hears an odd noise coming from the gearbox. He is unsure of the cause and could use a second opinion to diagnose the problem. If the technician is equipped with live video-collaboration software that connects his footage and audio to a remote expert, he or she may save time, costs, and an additional trip or two uptower. By using a collaboration platform, such as Librestream’s Onsight, the tech simply launches the Onsight app on his smartphone, connects using cellular or wireless networks, and video calls his expert at headquarters. Unlike video chat or conference calling, Onsight was built to meet rigorous security requirements and operate in low bandwidth environments. “Through use of an easy-to-access app, the wind technician and equipment expert can work together on finding and fixing that gearbox problem,” explained Charlie Neagoy, VP Business Development with Librestream Technologies. “The

Onsight Connect video collaboration software runs on smartphones, tablets, desktops, and even smart glasses. It connects field workers with experts for a shared experience to more rapidly diagnose, inspect, and resolve problems in low bandwidth and rugged environments.

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WINDPOWER Uptower wind-turbine repairs average $5,000 to $6,000 for a generator bearing change out, and $80,000 to $90,000 for an unpredicted failure that requires a crane. The wide price differences show that condition-monitoring systems can have a tremendous return per incident. However, not all products are equivalent or effective for monitoring each turbine component. It is important to do your research.

By Michelle Froese, senior editor; Windpower Engineering & Development SOON AFTER A WIND FARM’S COMMISSIONING, it is critical to adopt a cost-effective operations and maintenance (O&M) strategy to maximize the project’s long-term profitability and return on investment. Condition monitoring is a typical O&M tool that helps wind-farm owners and operators track the health of turbine components and related electrical systems. Its purpose is to assess the current condition of turbine assets, predict potential maintenance issues in components, or both. The advantage of predictive maintenance is that it lets wind operators proactively plan repairs or replacements, and only when needed so as to avoid unnecessary and costly uptower jobs. One recent study showed that most wind farms still use a reactive maintenance system for turbines, and that wind operators could save millions of dollars by using new preventive-maintenance technologies that identify problems before they result in unplanned downtime. One way wind operators benefit from predictive maintenance is by first setting alerts to signal when a diagnostic signal crosses a specified set point. Then, for example, if an operator were alerted to a temperature increase in a turbine’s generator, ideally a wind tech would quickly fix the issue before it becomes a serious problem. However, a recent study cited in Wind Energy O&M Report 2017, from New Energy Update compared the performance of predictive and conditionbased O&M strategies, and found that a predictive approach was not always the most effective. The report used a scoring strategy to measure the performance of different sensor configurations under various key component failure scenarios. The research examined 3-MW turbines on a 630-MW wind farm, and 2-MW turbines on a 420-MW capacity wind farm. Results showed that a condition-based monitoring strategy using all sensors (except oil sensors) was the optimal O&M strategy for the 630MW wind farm, but the preventative approach was more effective for the smaller, 420-MW project. Overall, a preventive strategy was more costly, and particularly under a gearbox-failure scenario. So how does a wind operator effectively choose a condition-monitoring system (CMS) for a wind project? According to David Clark, President, CMS Wind, it is an important question. The answer should be wind-farm specific. “Part of the problem is the erroneous assumption that all condition-monitoring systems for wind turbines



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are the same,” he says. “That’s like saying all cars are the same.” Although condition monitoring is now typically considered a must in the industry, the sheer number of different systems available has led to problems. “Not all systems are equal,” says Clark. “And buying an ineffective condition-monitoring system is costly, it can be damaging and has contributed to a slower acceptance of CMS in the industry. It is truly a buyer-beware scenario.” Clark says that contrary to the advertising, not all systems are ideal for an application and typically more than one tool is necessary. For example, oil-related sensors and filtering systems are typically focused on gearbox monitoring (which make up about 50% of the drivetrain failures), while vibration-based systems tend to work on the drivetrain as a whole. Conditions and events, such as icing or lightning, also require the correct sensors and properly configured CMS.

also important to consider a system’s software capability to store alarm and measurement criteria, and perform analysis for proper preventative maintenance,” he adds. When assessing potential risks to a CMS program, Clark says there are a few points to consider. • Incomplete data. This includes a lack of full data and access to report configuration, or inadequate review of the available information. • Poor analysts. Incorrect calls and lack of experience in wind has, in some ways, created an illusion that CMS is ineffective. • Ineffective monitoring. A poor system choice for a specific wind farm, or poor communication between analysts and wind operators. • Ease of use. Data must be available in real time and in simple, easy-to-understand terms or formats for proper reporting, analysis, and understanding. • Predictive maintenance. Proper component monitoring can lead to significant cost savings. Case in point: a single onshore event involving a crane is $300,000 on average for a 1.5-MW wind turbine. Avoiding the crane cost by predicting the failure using predictive CMS drops the per-event cost to $12,000 to $15,000. Ideally, a CMS will also include predictive analysis. “However, just because a wind turbine is optioned with preventive monitoring does not mean that it is the best solution or even a viable one. Do your research,” Clark advises. “Education is invaluable and key to a productive, well-run wind farm.”

An evaluation of seven different condition-monitoring systems (CMS) installed by OEMs and aftermarket vendors show the odds are high that a system will have improper sensors or the sensors be mounted incorrectly. The end results will be missing detections and false alarms.

“Take sensors, for example. There are only so many signals and measurements one can pull from a sensor. Unfortunately, there are many variables beyond just the sensor and hardware installed in a nacelle,” says Clark. “And if the core CMS system has incorrect hardware, issues go undetected.” To compound this, when measurements are not correctly established, expect missed detections and false alarms. “It is


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By Jeanay Langer, O&M sales & marketing proposal coordinator, and Valerie Mason, communications manager; EDF Renewable Energy

It is wise to include your wind service provider in the O&M budgeting process for each project. O&M teams work at wind sites daily, and will have a good idea of what repairs to expect for a project over time.

BUDGETING. It is far from a glamorous task, but a necessary one for businesses to succeed and thrive. The same holds true for wind project operations and maintenance. Wise and precise budgeting for O&M is key to optimal wind project performance and profitability. There are many things to think about when budgeting for project O&M tasks. Here are six of the most important:


1. Plan ahead for inspections, repairs, and upgrades. Many customers recognize that winter is tough on turbine blades and will plan and budget accordingly for a site inspection. However, it is not uncommon to find unanticipated blade damage during onsite inspections that impact turbine efficiency and production. What’s more, this additional cost for repairs is typically not factored into a project owner’s original O&M budget.


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Suggestion: If your wind site requires an inspection in the next six to 12 months, plan for it now. Also, set aside extra funds during the start of a project for those unexpected repairs that could interfere with wind project uptime. 2. Install upgrades at the same time as blade or turbine repairs. By doing so, wind project owners can save time and costs by avoiding multiple service trips uptower. The most costly part of repairs is the associated labor and wind project downtime. In addition, every trip uptower puts a wind technician at risk, so plan ahead to minimize risks as much as possible. Suggestion: Take advantage of turbine downtime by planning upgrades at the same time as repairs. For example, consider installing performance-improving solutions, such as leadingedge blade protection or vortex generators (VGs). VGs are small devices that adhere to a turbine blade to modify the surface airflow and optimize aerodynamic performance. 3. Expect failures. Turbine components must endure plenty of wear and tear, and harsh environments. Few last past their expected lifetime without damage that may lead to failure. For example, turbine gearboxes are lucky to reach the fiveyear mark without problems. Failure is par for the course and to be expected when it comes to owning a wind project — but you can plan for failures. Plan ahead and ensure wind project O&M budgets include contingency funds to cover the cost of major components, such as gearbox replacements or generator repairs.

5. Upgrade data. Supervisory control and data acquisition (SCADA) is a network data system that provides control and communications. If your wind project’s SCADA servers are more than seven years old, it is time to think about upgrading the system. Suggestion: Instead of budgeting to fix an outdated SCADA system, consider spending funds to virtualize the servers. With a virtual server, it is unnecessary to plan for the time and equipment necessary to obtain system repairs. The updates can be done virtually and in minutes. 6. Get quotes early. Late spring through early fall is a busy time for O&M service providers. If your wind site is due for an oil change or an end-of-warranty inspection within the next year, plan for the cost and maintenance now. Suggestion: Get quotes and secure a service provider six to eight months before work needs to be completed. Scheduling work ahead typically leads to lower costs and ensures your O&M provider is available for the work required on your wind project. Siting and building a wind project is only part of the project process. Once operational, operations and maintenance is critical to a productive site. To help with advice and budgeting throughout a project’s lifetime, include your O&M provider in the planning and budgeting process. O&M teams are on wind sites daily, and can offer guidance on the repairs and inspections to expect over time.

Suggestion: Your O&M provider can help you analyze which components to prioritize repair or replacement budgets for based on your wind project. With the right plan in place, you can avoid wind-turbine downtime because of unexpected failures and unavailable repair funds. 4. Stay compliant. NERC, or the North American Electric Reliability Corporation, is a not-for-profit international regulatory authority that assures the reliability and security of power systems in North America. NERC regulations are evolving with new standards rolling out multiple times a year. Fines for noncompliance are costly, and a site that fails to meet standards will be assessed on a daily basis until the issue(s) is resolved. Suggestion: Plan for NERC compliance based on the size of your wind site, and keep up to date on the standards. Their requirements are extensive and change every few months. So, it is important to ensure there are enough funds put aside to hire NERC experts for project inspections to ensure your site is compliant and stays that way.

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TIPS FOR CHOOSING THE RIGHT DRONE-INSPECTION SERVICE SENDING WIND TECHS UPTOWER to inspect blades is a time-consuming and potentially dangerous task. Recent advancements in drone technology or UAVs (unmanned aerial vehicles) are slowly turning such labor-intensive maintenance efforts into a safer, more precise, and streamlined process. And wind companies are taking notice. For example, global energy companies such as Enel, E.On, and AES are starting to invest in drones for tower and blade inspections. U.S.-based drone inspection company, SkySpecs, is working with Sandia National Labs to validate turbine blade damage data using its automated drone inspection technology. And currently, SkySpecs is collaborating with Siemens to deploy automated drone technology for onshore and offshore wind turbine inspections. Ben Marchionna, System Integration & Test Engineering Lead at SkySpecs, says that drones offer many advantages for wind turbine inspections, with safety the most significant. “Using a drone for blade inspections is safer than a wind tech hanging off a rope at high altitude, in high winds, and for long periods,” he says. This type of manual inspection can take up to a full day for a single tower and months for a full fleet. Marchionna notes that the Federal Aviation Administration (FAA) has a certification process, but it sets a low bar of entry for commercial operations. Although the FAA requires an aviation and systems knowledge test, the practical flying test for drone pilots is basic and falls short of meeting the demanding skills required for wind-turbine inspections. Currently, there are no additional regulatory qualifications required for wind sites. Marchionna advises wind companies to use caution when sourcing and contracting a drone-inspection company. “The FAA's recent Part 107 commercial drone certification program has resulted in a flood of ‘hobbyist’ drone pilots looking to earn extra cash,” he explains. “They will often solicit wind companies with the promise of safe, industrial UAVs, but show up inexperienced and often with a cheap, unreliable drone.” Hobbyists typically lack wind experience and extensive drone flying skills, he says, so they pose a greater risk to wind-turbine site operations. This may result in asset damage, lost revenue, or serious accidents. “Unfortunately, the current FAA drone pilot certification is not difficult to pass compared to the skill level required to perform consistently safe and reliable drone inspections


SkySpecs’ automated drone inspection is launched with the simple push of a button, and can often be done in as little as 15 minutes. Data is then automatically analyzed, annotated, and ready for review within 48 hours.

of turbines. So, look for drone companies with track records of successful experiences in the wind industry." “This is important because wind turbines present a difficult inspection environment,” he says. “Turbines are located in windy locations, and as a pilot navigates around the turbine blades, the wind speed and direction can change rapidly and unexpectedly because of how the turbine structure interacts with the wind. This makes manual flights exceedingly challenging and potentially dangerous.” For instance, the blades and tower can present large visual obstructions. “It can be tough to get an accurate sense of how far a drone is away from the blades, and continually looking uptower can cause operator fatigue.” Marchionna says even expert pilots can become physically or mentally fatigued, or simply lose situational awareness. “Losing sight of the drone for even a moment during flight can result in impacts with the turbine. Such an event could cause debris or hazardous material issues on the ground if, for example, a drone’s batteries are damaged on impact.” Drone pilots must also adhere to numerous safety regulations associated with flight operations near a


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By Michelle Froese, senior editor; Windpower Engineering & Development

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WINDPOWER structure. For personnel on the ground, this typically involves standing a planned distance away from path of the drone, during takeoff, landing, and flight. “It is a pilot’s responsibility to ensure ground personnel are cognizant of a drone's location in the sky at all times, and are aware of the safety procedures in the event of an inflight emergency. When all is said and done, the safety of those at a wind site and of the turbine assets during an inspection comes down to the skill of the drone pilot.” To mitigate many of these concerns, SkySpecs has developed an autonomous inspection drone, which the company says can maintain precise location, control, and image capture while navigating around a tower. “In this case, the pilot is on site strictly as a safety backup,” says Marchionna. “The automated drone’s on-board sensors are far more accurate than a pilot standing below the tower, and it can constantly analyze its position with respect to the tower while factoring in changes in wind condition. Plus, the automated computer cannot fatigue or forget where it is, so human error is no longer a safety factor.” Automated drone inspections let customers identify problem areas faster, and optimize repair schedules and costs earlier and more accurately. “It’s not only faster but the measurable and repeatable data improves a wind operator’s ability to predict problems in the field, and deploy repair crews before an issue escalates,” he says. “This, in turn, leads to higher efficiency in the energy generation and lower overall operations and maintenance costs over the life of the turbine.”


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A picture taken from a drone captures clear evidence of erosion on a turbine blade.


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THE FUTURE OF OFFSHORE WIND IN THE U.S. NOW THAT THE UNITED STATES HAS TESTED THE WATERS with its first offshore wind farm—the five-turbine Block Island Wind off the coast of Rhode Island—predictions vary about the future growth of the industry. Bloomberg New Energy Finance has forecast that the U.S. will have a total installed offshore wind capacity of between 3 and 4 GW by 2030. A new report from renewable-energy consultants, BVG Associates, also predicts that the U.S. offshore market will develop rapidly from 2020 to 2030. It provides a more optimistic forecast where annual installed capacity surpasses 1 GW in 2026, and continues to increase annually with a cumulative 8.4 GW installed at the end of 2030.

By Michelle Froese, senior editor; Windpower Engineering & Development

turbines are operating near Block Island, several Mid-Atlantic and Northeastern states are passing legislation and making purchase commitments resulting in a regional project pipeline totaling more than 5.4 GW,” she says. “And that number is only going to increase.” The Network is actively engaged in a number of initiatives to expand the offshore market. For example, it was involved in passing the Maryland legislation in May 2017, which has set the course for two offshore projects totaling 368 MW. “When this legislation was first debated in 2013, the price point was estimated to be $230 MWh. Since then, that number has been nearly cut in half. The Maryland Public Service Commission’s approval of the U.S. Wind and Deepwater Wind projects set a $134 MWh price point, and that gives the industry a baseline price.” Burdock credits this decision with moving the U.S. industry forward and is why she expects it to grow considerably over the next couple of years. “Until now, the cost of offshore wind in the country has always been speculative. Really, the most significant development in the U.S. offshore wind industry is that a price point has finally been set. So from here on out, we can expect project developments to move forward.”

investors have become more comfortable with and interested in the offshore wind industry’s movement into the global mainstream market. With close ties to the sector, Elizabeth Burdock, Executive Director for the Business Network for Offshore Wind (Network), also expects the industry to grow fairly quickly. The not-for-profit organization, which she helped develop, has a direct hand in supporting the offshore wind industry in the U.S. “Now that offshore

The U.S. offshore wind industry is in full swing. The States of Massachusetts, New York, and Rhode Island recently released three reports that set out the context for offshore wind development in the Northeast and reveal its potential economic development benefits. The reports are available for download at



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KEY POLICY ACTIONS THAT ARE BUILDING THE U.S. OFFSHORE WIND INDUSTRY • Key industry players, such as the NREL, AWEA, the Network, and others, have formed the Offshore Wind Technical Advisory Panel (OWTAP), an initiative to develop national offshore wind standards in the U.S. • The Maryland Public Service Commission approved financing applications for two offshore wind projects totaling 368 MW. • In New York, the Long Island Power Authority approved a 90-MW offshore wind project. • New York State Energy Research & Development Authority is developing an Offshore Wind Master Plan, which identifies local potential offshore wind sites. • Massachusetts released an RFP for 400 to 800 MW of offshore development, which represents the largest competitive solicitation for offshore wind in the U.S. • In Virginia, Ørsted (formerly DONG Energy) is partnering with Dominion Energy to construct two 6-MW wind turbines off the coast of Virginia by 2020.

• The California Intergovernmental Renewable Energy Task Force was created as part of the BOEM federal process. It agreed that the development of an online data portal for the collection of spatial data and information sets (pertinent to offshore wind energy in California) would be useful in identifying areas appropriate for offshore wind energy development off the west coast. • Two Gulf Coast companies have announced that they will build the first U.S. Jones Act-Compliant Jack-Up Vessel, an important advancement in U.S. offshore technology.

She says that while the industry has been slow moving in the U.S., the country has and will benefit from lessons in the European market. “As offshore wind has advanced over the last two-plus decades in Europe and gradually become less reliant on subsidies, investors have become more comfortable with and interested in the offshore wind industry’s movement into the global mainstream market. This comfort and interest is also lowering the cost of equity capital, which will directly contribute to the lower kilowatt-hour price for the

the United States is benefitting from their cost-cutting project development measures, investments and advances in turbine technology, and examples of how an offshore supply chain works most efficiently. These are great advantages.” Burdock predicts that during the next three to 12 months, the U.S. offshore wind industry will see new commitments from state Governors—such as Governor Carney in Delaware, who signed an Executive Order to establish a group for studying the potential environmental and economic benefits of offshore wind. She also expects the Department of Interior’s Bureau of Ocean Energy Management (BOEM) to hold additional federal lease auctions. In March 2017, the BOEM formally executed the lease of 79,350 acres offshore New York to offshore company, Statoil. Statoil is evaluating the lease site including the seabed conditions, wind resources, and grid connection options. Currently, BOEM has committed to a minimum of one such lease per year.

The intent to accelerate commercial-scale development in the U.S. will also attract more European developers and businesses to enter the market here. ratepayer,” she says. Case in point: in the last four years, the industry has experienced a $96 MWh reduction in the U.S., and that’s without one commercial-scale project in the water. “What’s more is that by having the European offshore wind experience to learn from—with its 96,000 jobs to view as a precursor—



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“The federal process for approving permitting will likely be shortened within the next year, and supported by a new offshore wind standard-setting process,” says Burdock. “The intent to accelerate commercial-scale development in the U.S. will also attract more European developers and businesses to enter the market here.” Although offshore wind is still higher in costs than solar and land-based wind, a number of organizations, such as the National Renewable Energy Laboratory (NREL) and Annual Technology Baseline, predict project growth and substantial offshore wind cost reductions over the next 10 years. “Going forward, there is no question that cost reductions will be key to the industry’s growth, and we intend to fully support the sector in its ongoing growth and development,” she says. Indeed, in its recent Offshore Wind Technologies Market Report, NREL principal engineer and lead author of the report, Walt Musial, stated: “Around the world, several events have transpired in parallel to demonstrate that offshore wind is a viable U.S. market. These events include the Block Island Wind Farm, which became operational in 2016, the drop in offshore prices on the European market, which is driving U.S. interest in offshore development, and policies that have resulted in promotion and stimulation of offshore wind development by local and state governments. The

offshore wind market today is the result of a long process of technology and market cultivation.” Burdock agrees. “When you consider that electric cars will increase their market share and more aging coal and nuclear plants will go offline, the accelerated growth of the U.S. offshore wind industry will be essential to meeting the country’s electricity and clean-energy needs. This demand will also help drive offshore wind to deliver on its promise of reliable, clean energy and thousands of good, local jobs.”


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bobbing and weaving with the

solar punches

I JOINED THE SPW TEAM IN JANUARY 2017, when a new administration took over the White House and created some new challenges for the solar industry. Now, we’re reckoning with possible tariffs that could mean significant job losses in 2018, according to SEIA. I saw the effects of the 201 petition firsthand at a solar farm in Tennessee over the summer. The contractor had almost missed the utility’s PPA deadline because of a delay in panel shipment, but managed to stay on track with some creative solutions. I’ve found creativity to be the nature of this industry—installers find ways to persevere through the ups and downs of the “solar coaster” and continue to grow their businesses and the industry. And grown it has. In 2017, solar has again broken records. The U.S. solar market had the largest second quarter ever, installing 2.4 GW of solar. GTM Research and SEIA announced in the U.S. Solar Market Insight 2016 Year-in-Review report that over the next five years, the cumulative U.S. solar market is expected to nearly triple in size. And over the next decade, the number of solar panel installers is expected to increase by 103%, according to the Bureau of Labor Statistics. Individual states had a stellar 2017, too: Nevada passed legislation to raise the state’s RPS and put it back on the solar map. Texas had its best quarter in history in the spring, adding 24% of all the state’s cumulative capacity in three months. Florida reduced tax barriers for consumers to go solar. As solar grows, people keep looking for ways to make sure it’s equitable for all and also as environmentally friendly as possible. I’ve learned about strides being made in community solar through electric cooperatives and creative financing. By the end of 2017, the total solar capacity of rural electric co-ops will be five times the amount just two years ago, according to the National Rural Electric Cooperative Association. In the past two years, co-ops have expanded their solar footprint from 34 to 44 states. I’ve learned about new pollinator-friendly native plant initiatives to make solar better for agricultural areas that rely on bees and other pollinators to grow crops. Native vegetation is one way to make up for the inevitable environmental disturbance that occurs when installing solar farms, and Minnesota led the way on creating a standard for pollinator-friendly arrays that other states like Vermont are now emulating. Although these feel like uncertain times for the solar industry, SEIA and passionate installers like you are pushing hard to make sure solar keeps growing. No matter what happens in the political realm, the numbers don’t lie: Solar means jobs, and solar is the future. SPW




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united states


Provided by:

Note solar irradiance across the country to plan for your next project. The 2017 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 2017 data with long-term averaged values from its continually updated global solar dataset.





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top solar stats

There’s a lot to consider when setting up shop in a new state. Here’s an easy way to look at which states are excelling in the industry and in what ways.

Top states for cumulative solar capacity through Q1 2017 California (19,665 MW) North Carolina (3,540 MW) Arizona (3,254 MW) Nevada (2,350 MW) New Jersey (2,164 MW)


Top states for 2016 installed solar capacity California (3,819 MW) Georgia (775 MW) North Carolina (768 MW) Utah (760 MW) Texas (423 MW)

Top cities for total PV capacity through 2016 San Diego, California (303 MW) Los Angeles, California (267 MW) Honolulu, Hawaii (175 MW) San Jose, California (174 MW) Phoenix, Arizona (165 MW)

Top utilities by 2016 installed solar megawatt Southern California Edison (California) (1,647 MW) PG&E (California) (773 MW) Rocky Mountain Power (Utah) (759 MW) Los Angeles Dept. of Water and Power (California) (732 MW) Georgia Power Company (Georgia) (553 MW)





Most solar watts per customer by utilities in 2016 City of Palo Alto Utilities (California) (2,754 watts/customer) Dominion North Carolina Power (North Carolina) (1,718 watts/customer) Farmers Electric Cooperative – Kalona (Iowa) (1,564 watts/customer) Ouachita Electric Cooperative (Arkansas) (1,282 watts/customer) Rocky Mountain Power (Utah) (847 watts/customer)



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Top states by percentage of solar jobs held by veterans in 2016

Top metros for solar jobs in 2016 San Francisco, California (26,056) Los Angeles, California (23,622) Boston, Massachusetts (12,487) San Diego, California (11,306) New York, New York (10,815)

Texas (15.7%) Oklahoma (15.1%) Utah (15.1%) Pennsylvania (12.6%) Wisconsin (12.4%)

Top states by percentage of solar jobs held by women in 2016 Vermont (47.8%) Tennessee (47.8%) New Mexico (45.4%) Ohio (42.9%) Montana (41.8%)














Solar jobs in 2016 California (100,050) Massachusetts (14,582) Texas (9,548) Nevada (8,371) Florida (8,260

Sources: SEIA, SEPA, GTM Research, The Solar Foundation, Environment America Research and Policy Center

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By Kelsey Misbrener, associate editor; Solar Power World

Inverters Inverter warranties vary with the different types of inverters. Central inverters typically come with five-year limited warranties. String inverters promise a longer lifespan, with warranties of about 10 years. And microinverters come with by far the longest warranties, as much as 25 years. Mounting Solar mounting warranties also vary widely, from five to 25 years, likely because of the range of materials used to make them and other differentiating factors (such as whether it’s tracking or roof- or ground-mounted). Because of all the variables, pinning down the lifetime in general is difficult.

ACCORDING TO SEIA, solar PV systems have life expectancies of upwards of 30 years. However, even if the panels are guaranteed by the manufacturer to last that long, what about the rest of the components that make your array work? We looked at the different warranties offered by typical solar array components to help you gauge the expected lifetime of your solar installation. Warranties don’t necessarily equal life expectancy, but they are a good place to start estimating. Panels Solar panels typically come with 25-year performance warranties and 10- to 12-year limited warranties. Performance warranties guarantee that the power output will decline at a rate set by the manufacturer– usually about 0.7% each year. By the end of year 25, the output should be no less than about 80% of the labeled power output. Batteries Batteries used in solar arrays come with a wide range of warranties. Deep-cycle lead acid and AGM batteries are on the low end of the spectrum, with some manufacturers offering a one-year limited warranty. Lithium-ion and redox-flow battery manufacturers offer longer warranties, as much as 20 years.



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O&M Appropriate maintenance can help extend the life of your solar array. There are four types of maintenance that can be offered, according to the National Renewable Energy Laboratory: Administration maintenance: Establishing budgets and securing funds for preventative maintenance, corresponding with customers, record-keeping, reporting on system performance and O&M program efficacy. Preventative maintenance: Scheduling maintenance checks to conform to manufacturer recommendations as required by equipment warranties. Frequency of preventative maintenance is determined by equipment type, environmental conditions and warranty terms. Corrective maintenance: Required to repair damage or replace failed components. Less urgent corrective maintenance tasks can be combined with scheduled, preventative maintenance tasks. Condition-based maintenance: Using real-time information from data loggers to schedule preventative measures like cleaning. Anticipating failures or catching them early. Although component warranties may be less than 30 years, if you do your homework before the installation and perform maintenance throughout its lifespan, you can ensure a long life for your solar array.

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By Direct Energy Solar

AS YOU BEGIN YOUR SEARCH FOR PHOTOVOLTAIC INSTALLERS, you’ll likely come across two similar-sounding concepts: 1. 2.

Solar product warranties Solar workmanship warranties

But what do these two terms mean exactly? And how do they differ? Solar product warranties defined Solar product warranties are very similar to what you receive whenever you buy consumer goods like iPads, televisions or computers. In essence, the manufacturer guarantees that its product will not break for a set period of time. But with most electronic products, the best you can hope for is about one year of coverage—maybe three years if you buy extended protection. However, PV products work a little differently. Because solar doesn’t have any moving parts, it is one of the most durable energy generation technologies in the world. Moreover, each component is rigorously tested before shipping to market. As a result: •

Most panel optimizers carry warranties ranging from 12 to 25 years (depending on the manufacturer). If anything happens, the original factory will replace the defective part free of charge. Solar PV panels come with standard warranties of 25 years. Again, if anything happens, you receive a replacement part for free. However most panels last much longer—sometimes for as many as 40 years.

Wi wi

(Graphics courtesy of Direct Energy Solar)

It’s important to note that all solar panels degrade with time— usually about 0.5% every year. This is why manufacturers only guarantee 80% performance or higher after 25 years. Now let’s turn to the other type of warranty—the one that covers installation workmanship.



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Solar workmanship warranties defined Whereas product warranties protect you against component-related issues, workmanship warranties protect you from labor-related defects—e.g. those arising from the actual installation process. This type of guarantee states that: • • •

The design, assembly and installation are all done correctly The system will perform as expected—without malfunction Any defects that may arise will be fixed free of charge

Solar workmanship warranties vary depending on the installer. Some offer none, while others provide five years of continuous coverage.

For truly worry-free solar protection, be sure to… As a general rule, you should avoid any contractors who don’t provide both types of warranties—product and workmanship. The longer the coverage, the better. However, there is one final type of coverage that a select number of installers provide—a solar production guarantee. With this type of protection, the installer promises that your system will deliver a predetermined amount of solar energy every billing cycle. If your installation ever falls below this threshold, the contractor will correct the problem—and even compensate you for any financial losses.

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By Kelly Pickerel, managing editor; Solar Power World

(Photo credit: Dennis Schroeder, NREL)

So panels degrade automatically; that’s worked into their performance warranties. There are also outside forces that can contribute to a panel’s degradation and possible failure. We talked with Sarah Kurtz, research fellow at NREL and co-author of that oft-cited 2012 study, on how technology and manufacturing changes, along with installation practices, affect degradation rates. ALTHOUGH CRYSTALLINE SOLAR PANELS are often sold with 25- to 30-year lifespan guarantees, those 30-year-old modules won’t be performing as well as they did on Day 1. Performance declines as solar cells degrade due to unavoidable circumstances like UV exposure and weather cycles. Manufacturers realize this, so solar panels come with a power output or performance warranty that usually guarantees 80% production at 25 years. Panel companies are only comfortable offering this guarantee because of a 2012 NREL study (“Photovoltaic Degradation Rates— An Analytical Review”) that found solar panels degrade about 0.5% to 3% each year, barring any equipment issues.



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A complex issue According to NREL, modules can fail because of unavoidable elements like thermal cycling, damp heat, humidity freeze and UV exposure. Thermal cycling can cause solder bond failures and cracks in solar cells. Damp heat has been associated with delamination of encapsulants and corrosion of cells. Humidity freezing can cause junction box adhesion to fail. UV exposure contributes to discoloration and backsheet degradation. These things just happen, and it’s difficult to determine how bad the degradation will be.

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“Solar panel degradation and failure is not a clear-cut situation,” Kurtz said. “There are lots of different reasons why they degrade and why they fail.” Kurtz said module manufacturers are looking into every piece of the solar panel puzzle, all the way down to the encapsulants and adhesion materials, to try to slow degradation rates. “Companies are figuring out how to change the formulation of the encapsulants so they don’t yellow,” she said. “In my opinion, they’ve made great progress in solving this problem.” New inverters, higher voltages and PID If it wasn’t bad enough that solar panels turn on themselves after years in the field, outside products can also contribute to degradation levels. The increased usage of transformerless inverters on U.S. solar projects has raised the threat level of potential induced degradation (PID) of solar panels. PID happens when different components in the same system are at different voltage potentials (such as the frame and the solar cell), which can allow electrical current to leak and modules to lose their peak performance. Often, simply negatively grounding a system removes the concern for PID, but transformerless inverters are ungrounded.

(Photo credit: SolarTech Universal)



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SOLARPOWER When that electrical current leaks, sodium ions in the glass move toward the solar cell or the frame, depending on how the system is grounded. There’s also an issue with the whole industry moving to higher voltages, because higher voltages make that current pull stronger, and sodium ions move more easily over top solar cells, reducing their output. Frameless modules can help reduce the PID possibility (since there’s no metal frame to disrupt voltages). And many module manufacturers take extra steps to ensure modules are PID-free now. It’s important for installers to know what products they’re combining into a full system to know if something besides the panel may contribute to degradation. Cheaper panels and less material Back in 2015, NREL surveyed New York installers and found that many were having the same issues with new solar modules. As module companies were trying to lower their prices, they made their frames thinner to reduce the aluminum. “[Installers were] finding that those frames will bend,” Kurtz said. “As snow melts and then refreezes on the edge of the module, that puts quite some strain on the frame. Those newer frames would bend.” Bent frames can strain the whole panel, and it can be especially bad as panels get thinner and less mechanically robust. “When people squeeze the cost down, they can find low-cost materials or they’ll try to reduce the total amount of material,” Kurtz said of today’s modules. “As you optimize the cost of the module, you’ll tend to see more mechanical failure mechanisms.” More, thinner busbars Solar panels sometimes fail because of busbar solder bond failures. With the trend of more busbars on solar cells, you would think there is a higher chance of solder bond failures. That’s not entirely true. “Cells can easily break,” Kurtz said. “If you have a big ribbon with a big solder bond, it puts more local stress on the cell and causes them to be more likely to break. By reducing the size of those solder bonds, you can reduce the amount of stress at the point where that ribbon gets connected to the cells.” With more busbars and more solder bonds, there is a higher probability of solder bond failure. But the importance of one solder bond failure goes down when there are more busbars to pick up the slack. Also, more busbars across a solar cell can decrease the chance of full cell breakage.

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Hand-to-hand transport can affect a module, especially if installers are carrying modules on top of their hardhats. That flexing and bouncing up and down can take a real toll and lead to microcracks in the cells. Same with dropping a module and the biggest no-no—standing or walking on top of solar modules. “It doesn’t necessarily stop working right away, but it will degrade with some time,” Kurtz said.

Flexible panels and installation As module companies decrease their costs, they may turn to ultrathin solar cells that use less silicon. Thinner solar panels are more flexible and not as rigid as older module models, which makes installation a delicate process.

What can we do? Not all new technologies are bad, nor are all modules destined for failure. Kurtz mentioned that recent NREL research has found fewer PV module issues being reported. And although the types of problems may be changing, module warranties are increasing and system lifespans are getting longer. Smart buying and installation of solar panels and other project components can mitigate potential degradation chances. Using trusted products and installing them with care will ensure a solar system will perform at its best—with no more than 3% power loss each year.

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A MARKET UPDATE ON DUAL-AXIS TRACKERS By Kelly Pickerel, managing editor; Solar Power World

THE DOMINANCE OF SINGLE-AXIS TRACKERS in the large utility-scale solar market sometimes steals the limelight from its dual-axis cousins. But dual-axis trackers—those that follow the sun more directly than single-axis models’ east-west path—have their place in residential and commercial markets. We caught up with Vermont’s AllEarth Renewables to learn more about dualaxis solar trackers and what makes them a great choice. Stats and customers AllEarth manufactures four dual-axis models, each holding a table of 20 to 24 solar panels at a height of about 11 ft above the ground when flat. With an authorized dealer in almost every state, AllEarth solar trackers are available across the country. Single-axis trackers follow the sun across a horizontal plane, but dual-axis trackers move in a more direct, circular path.



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“Different manufacturers use different methods of tracking to follow the sun,” said Paul Gustafson, technical customer support for AllEarth. “The AllEarth Renewables dual-axis trackers use GPS signals to determine the tracker’s latitude and longitude, as well as the date and time. With this information, the tracker will know the position of the sun for any given time and orient itself to face the sun using a hydraulic drive system. The tracker will be facing the sun even during cloudy periods, so when the clouds part the tracker will already be positioned to maximize power production without any delays to reposition itself.” Since the panels are always directly facing the sun, AllEarth estimates that its dual-axis trackers produce 45% more energy than a fixed-roof system and up to 30% more than a fixed-ground-mount system.

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Residential customers turn to dual-axis trackers often because they have the land-space available and want to maximize their output. “[A residential customer] has some property and is looking for a power source away from the house and not on the roof,” said Tim Post, AllEarth sales account manager. “Their roof is likely inadvisable for solar because of dormers, slate, shading, east-west alignment, aesthetic considerations or structural issues.” Commercial customers often have the same reasoning for wanting a dual-axis tracker but with a green twist. “[Commercial customers are] often looking for the visibility for green energy cache and the PR factor,” Post said. “The commercial customer understands the greater value in being able to produce about 45% more power in the same footprint, especially when constrained by space or regulatory factors.”

The commercial customer understands the greater value in being able to produce about 45% more power in the same footprint. 70


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Benefits and future outlook As with a lot of solar developments, dual-axis trackers evolved from Europe. “Areas like Spain have embraced the dual-axis tracker as one of the best ways to harness the sun’s power for some time,” said AllEarth president and CEO David Blittersdorf. “In America, the market evolved from a niche market for maximizing solar energy production. Location plays into this, as states have different laws regarding solar energy production and net metering.” Dual-axis trackers obviously win the game when it comes to smaller arrays. Single-axis trackers only work if there’s enough land for a long span of panels. But dual-axis arrays can work just as well on larger projects as single-axis models—material costs are similar but dual-axis trackers produce more power since the sun is being followed more accurately. And with only one pole to work into the ground and a stow-level height at 11 ft, the land associated with dual-axis projects can continue to be used for agriculture, and vegetation management is much easier. Movement across two axes doesn’t automatically mean twice the amount of maintenance. “As with any solar system, fixed or tracking, AllEarth Renewables | | 740.249.1877 ® SOLAR POWER — 2018 GUIDEBOOK *rated72 by DNV-GL ©2017 Ecolibrium Solar,WORLD Inc. EcoFoot2+ andRENEWABLE Ecolibrium Solar®ENERGY are registered trademarks of Ecolibrium Solar, Inc.

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trackers should have an annual inspection to ensure the system is working properly,” Gustafson said. “The inspection should confirm that the inverter and panels are producing and that the system is tracking properly. The only scheduled maintenance recommended for the AllEarth trackers is a hydraulic fluid change every eight to 10 years.” To stay on top of this niche market, the AllEarth team is constantly working on ways to improve cost, reliability and monitoring with its dual-axis trackers. AllEarth’s new Gen 4 model (out in 2018) will be self-powered, drawing energy directly from its panels so it will work even if the grid is down. The new tracker will also be Wi-Fi, cellular and SD card-enabled, expanding its communication options. “We plan to keep finding ways for people to get more from the sun with our dual-axis trackers,” Blittersdorf said. “We plan to continue with the release of Gen 4 and get it ready for installations and sales for the 2018 year. Father down the line we plan to keep releasing innovative products that allow people to harness the full potential of renewables.”

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A traditional ground-mount system. (Photo credit: RBI Solar)

WHAT ARE THE DIFFERENT TYPES OF GROUND-MOUNT SOLAR RACKING SYSTEMS? ONE OF THE LARGEST AREAS OF INNOVATION WITHIN SOLAR involves the mounting system. Probably the most competitive solar product market, mounting systems are an important element of solar arrays—they secure solar panels to the roof or the ground. Here we go over the basic categories of ground-mounted solar systems to help new installers get a grasp on installation processes. Traditional ground-mount systems Ground-mounted solar systems essentially all work the same— systems anchor to the ground and hold a large number of stacked panels, often two but sometimes three or four panels high. Two rails usually support each panel, whether oriented in landscape or portrait. The anchoring to the ground is the tough part of these installations, as there are many different types of foundations.



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By Kelly Pickerel, managing editor; Solar Power World

If the soil is clear of debris, steel beams are driven into the ground and the racking system is attached to the beams. If ground conditions are not suited for smoothly driven beams, anchor systems may be used—helical piles, ground screws. These can take more time to install as they have to power through boulders and other large debris. Ground-mounted systems don’t always have to penetrate into the earth. Capped landfills and other brownfields are ideal for solar arrays, as they are underused land areas, but their temperamental ground conditions cannot be disturbed. Arrays can be ballasted on the ground just as they are on flat roofs. Concrete blocks hold a system in place, and if ground conditions can hold the weight of a concrete truck, cast-inplace blocks may be an easier option for installers.

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Tracking systems To improve energy output, developers and installers turn to tracking systems. These motorized ground-mounts track the sun throughout the day, ensuring the panels are facing the sun at all times. Panels are attached to similar racking tables as traditional groundmounts, usually bolted or clamped into place, but there are different types of tracking systems. The two main classifications of tracking systems are single-axis and dual-axis. Single-axis tracking systems span panels on long rows, following the sun from east to west. Dual-axis tracking systems separate out tables of panels and follow the sun on a more circular path for the best energy output. Tracking systems have two motor distinctions. Centralized trackers move many rows of panels with a single motor. Distributed trackers use one motor per row or table of panels. Centralized systems use fewer motors while distributed systems use many.



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Carports and canopies Solar carports and canopies can be looked at as really, really tall ground-mounts. They are very common in commercial settings, especially at schools and business campuses. Reinforced concrete foundations hold large steel beams that support solar panels overhead. Carports can be designed to cover one row of parking spots, span over two rows or be as large as a project needs. Many carports can be equipped with electric vehicle charging stations for an extra bonus to cars sheltering underneath.

A solar carport. (Photo credit: Quest Renewables)

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Floating solar systems Floatovoltaics—a solar array that floats on water—has really taken off in Asia and parts of Europe, and it’s beginning to find its way to the United States. Many reservoirs and water treatment facilities can benefit from leasing their water surfaces to solar developers. Although not really anchored to the ground, floating solar arrays still borrow characteristics of ground-mounted solar. Floating systems are made of a type of plastic that link together into a mat. Each individual float is molded into a tilted design, so panels are positioned at a similar degree as systems on a flat roof. Floating systems can often be assembled on land and then pushed out onto the water as more panels are added. The system is either secured to shore mounts or floating anchors.

A floating solar array. (Photo credit: Ciel & Terre)


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A rail-less system. (Photo credit: Magerack)

WHAT ARE THE DIFFERENT TYPES OF SOLAR MOUNTING SYSTEMS FOR ROOFS? ONE OF THE LARGEST AREAS OF INNOVATION within solar involves the mounting system. Probably the most competitive solar product market, mounting systems are an important element of solar arrays—they secure solar panels to the roof or the ground. Here, we go over the basic categories of roof-mounted solar systems to help new installers get a grasp on installation. Sloped roof mounting systems When it comes to residential solar installations, solar panels are often found on sloped rooftops. There are many mounting system options for these angled roofs, with the most common being railed, rail-less and shared rail. All of these systems require some type of penetration or anchoring into the roof, whether that’s attaching to rafters or directly to the decking.



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By Kelly Pickerel, managing editor; Solar Power World

The standard residential system uses rails attached to the roof to support rows of solar panels. Each panel, usually positioned vertically/portrait-style, attaches to two rails with clamps. The rails secure to the roof by a type of bolt or screw, with flashing installed around/over the hole for a watertight seal. Rail-less systems are self-explanatory—instead of attaching to rails, solar panels attach directly to hardware connected to the bolts/screws going into the roof. The module’s frame is essentially considered the rail. Rail-less systems still need the same number of attachments into the roof as a railed system, but removing the rails reduces manufacturing and shipping costs, and having fewer components speeds up install time. Panels are not limited

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A non-penetrating system. (Photo credit: SolarPod)

A standard rail system. (Photo credit: Unirac)

to the direction of rigid rails and can be positioned in any orientation with a rail-free system. Shared-rail systems take two rows of solar panels normally attached to four rails and removes one rail, clamping the two rows of panels on a shared middle rail. Fewer roof penetrations are needed in shared-rail systems, since one entire length of rail (or more) is removed. Panels can be positioned in any orientation, and once accurate positioning of the rails is determined, installation is quick. Once thought to be impossible on sloped roofs, ballasted and nonpenetrating mounting systems are gaining traction. These systems are essentially draped over the peak of a roof, distributing the system’s

weight on both sides of the roof. Strain-based loading keeps the array almost suctioned to the roof. Ballast (usually small concrete pavers) might still be needed to hold the system down, and that extra weight is positioned overtop loadbearing walls. With no penetrations, installation can be incredibly quick. Flat roof mounting systems Commercial and industrial solar applications are often found on large flat rooftops, like on big-box stores or manufacturing plants. These roofs may still have a slight tilt but not nearly as much as sloped residential roofs. Solar mounting systems for flat roofs are commonly ballasted with few penetrations.








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Since they’re positioned on a large, level surface, flat roof mounting systems can install relatively easily and benefit from pre-assembly. Most ballasted mounting systems for flat roofs use a “foot” as the base assembly—a basket- or tray-like piece of hardware with a tilted design that sits on top of the roof, holding ballast blocks in the bottom and panels along its top and bottom edges. Panels are tilted at the best angle to capture the most sunlight, usually between 5 and 15°. The amount of ballast needed is dependent on a roof’s load limit. When a roof can’t support a lot of extra weight, some penetrations may be needed. Panels attach to the mounting systems either through clamps or clips. On large flat roofs, panels are best


positioned facing south, but when that’s not possible, solar power can still be generated in east-west configurations. Many flat roof mounting system manufacturers also have east-west or dual-tilt systems. East-west systems are installed just like south-facing ballasted roof mounts, except the systems are turned 90° and panels butt-up to one another, giving the system a dual-tilt. More modules fit on a roof since there is less spacing between rows. Flat roof mounting systems come in a variety of makeups. While aluminum and stainless-steel systems do still have a home on flat roofs, many plastic- and polymer-based systems are popular. Their light weight and moldable designs make installation quick and easy.


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A dual-tilt system. (Photo credit: SunPower)

A ballasted system. (Photo credit: Ecolibrium Solar)

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INVERTERS IN 2017 AND BEYOND SOLAR INVERTER MANUFACTURERS are always innovating to meet changing market demands. Here’s a look at some of the ways in which inverters advanced throughout 2017 and some trends experts see for the inverter market in 2018 and beyond. NEC 2017 As of October 1, 2017, NEC 2017 is in effect in 12 states, with 14 in the process of adopting the new code, according to While NEC 2014 rapid shutdown requirements only limited voltage for the wiring outside of a certain perimeter around the array, NEC 2017 adds detail by limiting the voltage at the module level. Inverter manufacturers have taken the lead on providing solutions to meet the code. While microinverters inherently meet rapid-shutdown requirements, string inverter manufacturers have released a variety of solutions to achieve compliance, such as offering DC optimizers or partnering


with MLPE or panel manufacturers with integrated technology that already meets the code. Though the code actually delays enforcing rapid-shutdown requirements until January 1, 2019, to allow time for the industry to develop a product safety standard for rapid-shutdown PV arrays, inverters are well on their way to code compliance. SunSpec communication protocol The SunSpec Alliance has also been working hard on the communications side of rapid-shutdown requirements. In September, it released its “communication signal for rapid shutdown interoperability specification.” It may


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seem like a mouthful, but it addresses a key, and somewhat controversial, part of the 2017 NEC code that requires all rooftop PV modules installed after December 2018 to stop electricity generation within 30 seconds. Supporters say the move will increase safety for first responders. SunSpec’s rapid-shutdown specification is a communication protocol that defines how the modules, inverters and other control systems interact to get the job done. Many manufacturers—including ABB, Fronius, Maxim Integrated, Omron, Outback, SMA and Texas Instruments—announced plans at the Solar Power International show in Las Vegas this year to incorporate the protocol. String inverter manufacturers are starting to offer SunSpec-certified solutions to also achieve module-level rapid shutdown. Fronius announced that its new Symo Advanced string inverter actually integrates communications compliant with the SunSpec protocol directly inside the inverter, so no extra box is needed. Inverter advancements in this area are expected to keep coming.

Rule 21 Though traditional interconnection requirements have mandated that inverters must shut down during grid issues to prevent back-feeding current onto the grid, new requirements are allowing inverters to use their advanced capabilities to help with grid voltage issues. The Electric Power Research Institute (EPRI) reported that advanced smart inverters can be the least costly solution for such issues. States are revising interconnection requirements so inverters can stay active and “ride through” minor utility faults to support the grid and allow issues to clear. California is leading this effort with recent changes to a set of utility interconnection requirements known as Rule 21. Effective Sept. 9, 2017, the revised rule widens the range of conditions during which inverters may operate and allows inverters to provide seven grid support functions. Inverter manufacturers are working toward UL 1741-SA certification to be compliant. Though California is leading the way for smart inverter requirements, grid support will increasingly be needed in places with high solar penetration. Hawaii may soon follow California’s lead, as well as other states such as Nevada, Arizona, Vermont and Massachusetts.

Source: GTM Research The Global Solar PV Inverter and MLPE Landscape: H2 2017



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Other trends: • As manufacturers are able to pack more kilowatts into smaller enclosures, string inverters will continue to be viable options over central inverters in utility projects. GTM sees more 1,500-V string inverters coming to the North American market in 2018. • While string inverters see opportunity for growth in the commercial and utility markets, DC optimizers and microinverters will increasingly take string’s place in residential installations, according to GTM Research.

Source: GTM Research The Global PV Inverter Landscape: H2 2016

• The United States is the top market for microinverters and power optimizers, according to IHS research. IHS Markit reported that suppliers are shifting their business models toward integrating with other products for smart and AC modules, rather than selling standalone models. The market for smart and AC modules will grow from less than 200 MW in 2015 to over 4 GW in 2020 as integrated products become favored in the global market, IHS predicts.



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AC MODULES MAKE A COMEBACK By Kelly Pickerel, managing editor; Solar Power World TWO YEARS AGO, GTM RESEARCH RELEASED A REPORT that predicted the integrated smart and AC module market would reach 1 GW by 2020. Looking around at the market then, it seemed kind of impossible. The 2014 integrated market barely hit 73 MW, and it is supposed to increase 14 times to 1,000 MW in seven years? Power optimizers (to make modules smart) and microinverters (to make modules AC) have been around and in use, but integrated modules with either option are harder to find. Walking around the exhibit hall at Solar Power International 2017, it appears AC modules are making a comeback, and there might be some truth to that whole 1 GW by 2020 thing. Since Solar Power World gave the lowdown on smart modules in a previous article, we’ll now take a deeper look at the world of AC modules What is an AC module? In a traditional solar system, solar panels produce DC power, which gets fed to a nearby inverter and then converted into AC power for typical use. AC modules make that power conversion right at panel-level, so long cable runs to string or central inverters aren’t needed. Microinverters come pre-attached and pre-wired with the solar panels, so they’re called “AC modules.” AC modules come with many installation benefits. Time spent installing is cut significantly when the inverter and module are positioned at the same time. Installers don’t have to attach electronics to rails and then attach panels. DC wire management is a thing of the past.

LG’s NeON 2 ACe module with Enphase microinverter

What’s the deal with AC modules today? To find AC modules, your best bet is to look at microinverter manufacturers and their partnerships. Five years ago, the two main microinverter companies trying AC modules were SolarBridge and Enphase. SolarBridge was acquired by module manufacturer SunPower in 2014, and SunPower now markets a full AC module within its SunPower Equinox residential system available through its dealer network. In addition to the AC module, the Equinox system has mounting, monitoring and one warranty. These AC modules have found success as part of a full system only sold by SunPower dealers, but on a limited (yet still large) scale. Enphase has been in the AC module game for a while, but integrated modules with the company’s inverters hadn’t been seen for a few years. Installers were still purchasing Enphase microinverters and manually connecting them to solar panels, but an outright AC module was not being pushed. Enphase now has two new AC module partnerships on the market—with LG and JinkoSolar—that promise a much better experience than the company’s efforts five or six years ago. “Around 2011, we did enter into a couple partnerships for an early version of module. These were mechanical in nature; the ones now are electrical in nature,” said JD Dillon, vice president of product

The IQ series [of microinverters for AC modules] represents an eventual link to energy independence. Since there’s a module-level switch to AC voltage, AC modules are safer to handle. These integrated modules are also NEC 2014 and 2017 rapid shutdown compliant from the get-go. Logistics are easier, because the two products ship as one. Fewer components take up less space in warehouses. And if the module manufacturer offers a single warranty for the full system, performance is guaranteed.



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Global Smart and AC PV Module Base-Case Forecast, 2014-2020E Source: GTM Research’s Smart and AC PV Modules, 2015-2020

management and pricing at Enphase Energy. “The module was a microinverter clipped to the frame of a panel, and you still had to plug everything in, hook everything together. It sold almost as a kit. That’s why I call it mechanical—it was clipped and plugged as opposed to fully integrated.” Enphase’s new IQ series of microinverters have been specifically developed for AC modules and now ship fully integrated with LG or JinkoSolar panels. Rather than its “mechanical” connection attempts with early AC module efforts, these new systems are “electrical” and offer easier plug-and-play options from Enphase. The microinverter is pre-mounted and fully tested with the LG and JinkoSolar panels. The microinverter is backsheet attached and ships collapsed within the panel’s frame. When the module is ready to be installed, the microinverter is pulled down gently and snapped into place with 15 mm of airflow



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between the backsheet and the microinverter. This improved airflow helps with performance and reliability. Modeling plans from SunPower, Enphase is interested in being part of an entire system that begins with an AC module. “The IQ series [of microinverters for AC modules] represents an eventual link to energy independence,” Dillon said. “We’re going to be upward compatible from here on out. Our ultimate goal is to be almost a solar appliance on the roof for an energy-independent world. An inverter, a panel, the software, the energy management system and the battery—that’s a cohesive, self-sustaining system.” LG and JinkoSolar are just the first partnerships Enphase has set up for AC modules. If the company increases access to AC module offerings, the U.S. industry just may hit 1 GW of integrated installations by 2020.

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WHAT’S THE DEAL WITH SOLAR NET METERING? SOLAR NET-METERING POLICIES ENCOURAGE homeowners and businesses to install solar by paying them for the solar power they feed back to the grid. The policies provide a financial incentive to install solar in addition to saving on electricity costs. According to SEIA, “Net metering allows utility customers to generate their own electricity cleanly and efficiently. During the day, most solar customers produce more electricity than they consume; net metering allows them to export that power to the grid and reduce their future electric bills.” Forty-seven states plus Washington, D.C., took some sort of action on solar in 2016, according to Cleantech’s “50 States of Solar” Q4 2016 report. Of those, 28 states considered or changed net metering policies. Why is net metering contentious? Solar installers and utility owners are at odds. Utility owners and some politicians say net metering shifts costs to electric


By Kelsey Misbrener, associate editor: Solar Power World

customers who don’t have solar panels, and that falling solar prices lessen the need for the incentive. Many utilities view net metering as unfair because some states, like Indiana, require utilities to pay solar panel owners more than it would cost the utilities to produce the power.

Independent studies, in state after state including Maine, have repeatedly found that solar net metering saves money for all electric ratepayers.

(Photo credit: Creative Commons / NASA)



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But installers say net metering helps ease load-burdens during high-demand times. Solar installers are in favor of it because it is an added incentive for homeowners and commercial property owners to invest in solar. “Independent studies, in state after state including Maine, have repeatedly found that solar net metering saves money for all electric ratepayers,” writes Steve Hinchmin of ReVision Energy, Maine’s largest solar installation company, in the Portland Press Herald. “Plus, residential solar development is proven to help grow local economies, create new jobs, raise incomes and reduce pollution.” Who decides? It’s up to the legislative bodies of each state to determine the policy. According to the National Conference of State Legislatures, 41 states have net-metering policies in place as of October 2016. Two states—Texas and Idaho—have voluntary utility policies, while three others have distributed generation compensation rules other than net metering. Another three states— Tennessee, Alabama and South Dakota—have no policies in place. In a Washington Post article about the net metering battle that ended up lowering the net metering incentive rate in his state of Indiana, Sen. Brandt Hershman said, “I have nothing against solar. I’m simply trying to reset the marketplace.” He believed solar panel owners were reimbursed at too generous a rate.

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What will the future look like? Regulators in some states are considering measuring “value of solar” rates in place of net metering, an alternative “designed to capture the value solar installations provide to the electric system,” according to NCSL. But a solarcentric solution means the battle will wage on with other sources of renewable energy like wind power. Community solar is another initiative that utilities are pushing in lieu of net metering. Under community solar agreements, customers buy or lease panels from large solar projects supported by utilities in exchange for power or financial benefit. Utilities are fighting for control of energy, but small businesses rely on net metering incentives to make solar economical for customers. Without those benefits, some smaller solar installation businesses might have to turn off the lights.

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STRATEGIES TO MAKE THE MOST OF SOLAR LEADS WITH TECH TOOLS AND CUSTOMER PREFERENCES evolving so quickly, are your marketing and sales efforts still on target? Or are they starting to feel more like ready, fire, aim? Ugly stats on poor sales lead response tactics are a good indication that solar sales professionals might need to reexamine their sales processes, then dust themselves off and get back in the saddle. Sales software provider Velocify has distilled the best of its data-driven research into a handy guide that will help you do just that.

By Velocify

Simple things like responding quickly, being appropriately persistent, and leaving quality voicemails can leave a positive first impression and set you apart from your competition. This infographic uncovers the good, the bad and the ugly statistics related to online sales lead response. Read on to find how your sales lead response tactics can be a bit more Clint Eastwood—aka “Blondie”—from the 1966 movie classic.





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8 NATIVE AMERICAN TRIBES GOING SOLAR THE 567 FEDERALLY RECOGNIZED American Indian Tribes and Alaska Natives in the United States have many different languages and customs, but one thing they all share is a deep reverence for the natural world. It makes sense, then, that many tribes are choosing to go solar to help reduce their carbon footprints, save money on electric bills and create revenue on reservations. According to the Bureau of Indian Affairs, of the 326 American Indian reservations, “more than 150 have the resource capacity needed to sustain a 1- to 25-MW renewable and/or natural gas power generation facility.” The Department of Energy and Mineral Development has a grant program for tribes to access government funds for solar development, and its staff can help tribes through the process of going solar. GRID Alternatives also helps tribes identify funding sources for solar. In addition to financing projects, the organization launched a tribal program in 2014, where it works with tribes to install solar and provide training to students at tribal colleges throughout the country. Here are eight tribes that have added solar to their portfolios.


By Kelsey Misbrener, associate editor; Solar Power World

Navajo Window Rock, Arizona The Navajo Tribe has operated the coal-fired Navajo Generating Station since the 1970s, but the plant will soon close in 2019 due to competition from falling natural gas costs. To help balance the socioeconomic impacts of the closure, Navajo President Russell Begaye is pivoting to renewables. The Navajo Tribal Utility Authority now has a 27.5MW solar farm on 300 acres in a Navajo community south of Monument Valley, Arizona, according to the Associated Press. AP reports the solar farm “delivers energy across the reservation and into Arizona, California, New Mexico and Utah.” First Solar operates the project in Tempe, Arizona, but according to AP, there are plans to bring the controls in-house.

(Photo credit: The Southern Ute Indian Tribe)



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Solar array on the Sokaogon Chippewa reservation. (Photo credit: Current Electric)


Sokaogon Chippewa Crandon, Wisconsin SunVest Solar contracted Current Electric to build over 600 kW of solar on about 50 homes and 19 commercial sites for the Sokaogon Chippewa Community in Wisconsin. SunVest funded the project through a $1.1 million grant from the U.S. Energy Department and the Department of Housing and Urban Development. Part of the mission included hiring members of the tribe to help work on the installation.

Chemehuevi Havasu Lake, California EnSync Energy added a DER system to the Chemehuevi Tribe’s community center that includes a 90-kW solar array and energy storage totaling 125 kWh. The University of California Riverside’s Southern California Research Initiative for Solar Energy (SCRISE) obtained state funding to build the system for the tribe that demonstrates DERs and grid load management, while addressing energy resiliency and reliability issues at the community center.

Hoopa Valley Hoopa, California The Hoopa Valley Tribe added a solar carport along with storage to virtually eliminate the annual electricity bill for the tribe’s community center. The center includes indoor basketball courts and an outdoor swimming pool. JLM Energy provided the solar+storage solution and also financed the project.

Southern Ute Ignacio, Colorado The Southern Ute Tribe received a $1.5 million grant from the Department of Energy and funded $1.5 million itself to build a 1.3-MW ground-mount solar array on 10 acres of the tribe’s land. The tribe contracted Namaste Solar to design and build the project that will help to offset the energy usage of 10 tribal buildings.


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SOLARPOWER Washoe Gardnerville, Nevada The Washoe Tribe contracted nonprofit Black Rock Solar to build seven groundmount solar arrays at community centers on the tribe’s land. The tribe financed the project that will offset energy costs for about 50 homes with help from a $470,000 grant from the Department of Energy and NVEnergy rebates.


Moapa Band of Paiutes Moapa, Nevada The Moapa Southern Paiute Solar Project was the first utility-scale solar project on tribal land. First Solar constructed and operates the 250-MW plant that’s capable of generating enough energy to power about 111,000 homes. The tribe has a 25-year PPA with the Los Angeles Department of Water and Power to bring clean energy to Los Angeles residents. The tribe will benefit from lease revenues over the lifetime of the project and about 115 construction jobs for tribal members and other Native Americans.

Leech Lake Band of Ojibwe Cass Lake, Minnesota The Rural Renewable Energy Alliance (RREAL) received a grant from the McKnight Foundation and the Legislative-Citizen Commission on Minnesota Resources to build a 200-kW community solar array for the Leech Lake Band of Ojibwe Tribe. The solar will help offset energy costs for about 100 families. The Initiative Foundation also helped RREAL fund three tribal college students’ solar installation training and certification. The students then put their training into action and helped with the installation.

The Washoe Tribe’s cultural monitor Otis Bryan watches over construction of a 35-kW solar array at the Stewart Family Wellness Center in May. (Photo credit: The Washoe Tribe)

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AD INDEX Ace Clamp.......................................................................................... 67 AeroTorque......................................................................................... 25 Altech Corporation............................................................................... 7 Amsoil............................................................................................... IBC Aurora Bearing Company................................................................... 30 Aztec Bolting.....................................(WPE) cover/corner, special cover Baja Construction Co., Inc.................................................................. 79 Bal Seal Engineering, Inc.................................................................... 29 Bronto Skylift...................................................................................... 42 Burndy-Wiley...................................................................................... 63 Castrol (BP Lubricants USA).............................(WPE) IFC, 1 ; (SPW) 2, 3 Chint Power System................................................(WPE) 2 ; (SPW) IFC Cornell Dubilier Electronics, Inc......................................................... 85 Deublin............................................................................................... 30 Dexmet Corporation.......................................................................... 51 EcoFasten Solar.................................................................................. 73 Ecolibrium Solar................................................................................. 72 Everest Solar Systems, LLC................................................................. 76 Fronius................................................................................................ 89 GameChange Solar.................................................... (WPE) 3 ; (SPW) 1 Gradient Lens Corporation................................................................. 96 HELUKABEL USA.......................................................................... 31, 65 HYDAC Technology Corporation............................................Wind Tab KACO new energy Inc...................................... 87 ; (SPW) cover/corner Kipp & Zonen..................................................................................... 82

LONGi Solar ...................................................................................... 91 Magnum Energy, A Product Brand of Sensata Technologies............. 11 Megger............................................................................................... 61 Mounting Systems.............................................................................. 77 NRG Systems...................................................................................... 45 PCL Construction Enterprises, Inc...................................................... 97 Phoenix Contact................................................................................. 35 Pika Energy......................................................................................... 17 Preformed Line Products.................................................................... 70 RAD Torque........................................................................................ 33 RBI Solar............................................................................ Solar Tab, 75 Rotor Clip........................................................................................... 39 S-5!..................................................................................................... 78 Schletter............................................................................................. 71 Seaward Group................................................................................... 95 SnakeTray........................................................................................... 67 Solar Connections International......................................................... 81 SolarEdge Technologies..................................................................... 83 SolarRoofHook................................................................................... 69 Specialty Coating Systems................................................................. 47 SUNGROW POWER SUPPLY Co., Ltd................................................ 93 Trojan Battery Company..................................................................... 14 Yaskawa Solectria Renewables.......................................................... BC Zero-Max, Inc...................................................................................... 27

* The Renewable Energy Guidebook is a resource of both Solar Power World and Windpower Engineering & Development. .Some ads may appear in different positions depending on title, and in these instances are specified above.



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