Renewable Energy Handbook 2021 Solar Power World

December 2020 www.solarpowerworldonline.com

Technology T echnology • Development • Installation

2021

RENEWABLE

EHNANEDBROOGK Y

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by RBI Solar

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RENEWABLE ENERGY

HANDBOOK

Welcome to the 2021

Renewable Energy Handbook At times this past year felt like an eternity, but we bet a few expert renewable energy stories slipped past you in 2020.

This handbook reviews what has been trending in both the solar and wind industries in our sister publications Solar Power World and Windpower Engineering & Development.

In addition to installation tips, service guides and O&M best practices, the 2021 Renewable Energy Handbook offers our editors' picks for the top solar products released in the last year as well as the top wind projects recently brought online.

Don't worry if you were a little preoccupied in 2020; here is a solar and wind year in review and a few predictions for 2021.

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2021 RENEWABLE ENERGY HANDBOOK

SOLARPOWERWORLDONLINE.COM // WINDPOWERENGINEERING.COM

RENEWABLE ENERGY HANDBOOK

SOLAR POWER WORLD PUBLISHER Courtney Nagle cseel@wtwhmedia.com 440.523.1685 @wtwh_CSeel EDITORIAL Editor in Chief Kelly Pickerel kpickerel@wtwhmedia.com @SolarKellyP Senior Editor Kelsey Misbrener kmisbrener@wtwhmedia.com @SolarKelseyM Associate Editor Billy Ludt bludt@wtwhmedia.com @SolarBillyL

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SOLAR POWER WORLD // 2021 RENEWABLE ENERGY HANDBOOK

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WHAT’S INSIDE THE 2021 RENEWABLE ENERGY HANDBOOK

An Introduction to the Renewable Energy Handbook ...........................................................................2

Solar Power

Windpower

Solar Market Overview ...................................... 8

Wind Market Overview ................................... 46

Top Solar Products .......................................... 10

Major Wind Projects ........................................ 48

2020 Solar Power Leadership Winners ........... 15

2020 Windpower Leadership Winners ............ 50

Lessons in Climate Solutions ............................ 16

Safety and Construction .................................. 51

Landfill Installation Practices ............................ 20

Generators ....................................................... 54

Energy Storage ................................................ 26

Lightning Damage ........................................... 58

Solar Modules ................................................. 31

Bolting ............................................................. 62

Tracking Systems and Software ....................... 34

Wind Turbine Shafts O&M .............................. 65

Inverters and O&M .......................................... 38

Offshore Fastening .......................................... 70

Solar Connectors ............................................. 41

Pitch Control Valves ........................................ 73

Floating Solar Systems .................................... 43

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2021 RENEWABLE ENERGY HANDBOOK

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MARKET OVERVIEW

SMALLER SOLAR SECTORS TOOK A HIT IN 2020, BUT PATH AHEAD IS PROMISING THE SOLAR INDUSTRY isn't new to roadblocks on its path. Whether it's tariffs, manufacturer bankruptcies or misinformation about its reliability, this industry is tougher because of what it has endured. So when COVID-19 halted business across the country, the industry found a way to pivot to stay alive.

Installers moved processes such as sales and design online, organizations like NABCEP and manufacturers like Enphase made trainings virtual, CEOs made tough decisions to lay off employees or cut salaries and nonprofits lobbied for solar workers to be considered "essential" so their businesses could remain open despite statewide closures.

Still, the solar market didn't come out unscathed.

COVID caused an estimated 38% drop in forecasted U.S. solar jobs year over year, according to SEIA. The height of the pandemic hurt some solar sectors far more than others; the residential sector felt the most losses since it relies most on face-to-face sales. According to the “U.S. Solar Market Insight Q3 2020” report by SEIA and Wood Mackenzie, residential installations were down 23% quarter over quarter due to restrictions and shelter-in-place orders.

Utility-scale solar, however, remained resilient in the face of COVID disruptions, representing 71% of all new solar capacity brought online in Q2. Corporations also continued adding renewables at a record pace, investing in nearly 8 GW of wind and solar installations in 2020,

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SOLAR POWER WORLD // 2021 RENEWABLE ENERGY HANDBOOK

a 45% annual increase in installations stemming from corporate procurement, according to IHS Markit.

There's no denying the United States is on the verge of a big energy transition. Uneconomical and carbon-emitting fossil fuel plants are closing from coast to coast, leading to the question: What's next?

The answer is usually one of two resources — natural gas or renewables.

The SUN DAY Campaign found that renewable energy sources generated more electricity than either coal or nuclear in nearly 30 states and Washington, D.C., during the first two-thirds of 2020.

Although natural gas is still cheaper than renewables in some states, renewable portfolio standards and climate change mitigation factors help make solar an attractive option. According to the National Oceanic and Atmospheric Administration, the United States experienced a record-tying 16 total $1 billion weather disasters in the first nine months of 2020.

Public opinion on renewables has changed too. According to a Politico/Morning Consult poll, half of voters say the United States should incentivize the use of renewable energy over fossil fuels to combat climate change.

Solar and green jobs were central in the 2020 presidential election, with some candidates promising to tackle the twin goals of building back the pandemic-pummeled economy and fighting climate change by investing in solar and green jobs.

With growing public support and the right policies in place, the solar industry is well-positioned to flourish in the next year. SPW SOLARPOWERWORLDONLINE.COM

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TOP PRODUCTS

SOLAR POWER WORLD EDITORS PICK THE

TOP PRODUCTS OF 2020 CORONAVIRUS may have halted solar installations for a short time this year, but R&D and product development continued uninterrupted. With at-home and on-site power now more important than ever, many new products of 2020 aimed to make solar installations quicker and the user experience simpler for easier solar power consumption.

There weren't any in-person tradeshows for SPW editors to attend and see new products, but we kept

an eye on everything happening in every corner of the market this year. These are our top choices for the most innovative products announced and becoming available soon. We expect these products to transform the solar installation market — all for the better.

Be sure to check out an even more extensive database of the top solar products of the last year on our website.

Making whole-home backup a reality with smart circuits AS SEEN IN LUMIN When it comes to solar and energy storage, descriptive words can sometimes be confusing. A common misconception about battery backup is that the battery will actually back-up the entirety of a home's loads.

Most of the time, a battery has to be hooked up to its own protected loads panel that will support only a few circuits. But a handful of "smart circuit" products are coming to market to make whole-home backup actually mean what it says.

For example, the software/hardware combo Lumin is a physical box that taps into the main electrical panel to make all circuits "smart." Now instead of only being able to support five circuits through a protected loads panel, Lumin's software allows for load toggling, giving homeowners the ease of choosing which loads to support during a grid outage.

Smart circuit setups can also monitor charging levels while providing load control. If a battery is low on power, fully charging an electric vehicle probably isn't of the highest priority. Instead, apps like Lumin's can monitor energy consumption and automatically shed large loads during an outage to protect the battery from draining. Smart panels and smart circuits give consumers the flexibility to back-up everything or just a few important loads — and on varying schedules. The whole house might not be humming at full power during an outage, but at least homeowners don't have to settle for a few circuits every time a grid interruption occurs.

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SOLAR POWER WORLD // 2021 RENEWABLE ENERGY HANDBOOK

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TOP PRODUCTS Squeezing extra production out of single-axis trackers AS SEEN IN NEXTRACKER’S NX NAVIGATOR Tracking solar systems undeniably produce more energy than their fixed-tilt counterparts. The GPS technology directing their path every day is standard across the industry because it’s been long determined where the sun will be at any given time. But there's still room for monitoring and management software to help project owners optimize other tracker considerations like radiant light, compatibility with bifacial modules and compensation for increasingly frequent weather events.

Nextracker’s proprietary monitoring software, NX Navigator, gives site managers control over their arrays, providing data down to the production efficiency of individual trackers. The software, which works in conjunction with Nextracker’s TrueCapture control system, adds safety measures for extreme weather events and heavy snowfall. Site managers can adjust panels to stow at a safer angle for falling hail, as well as plan snow shed actions. Users can even schedule maintenance through NX Navigator.

Incremental improvements for utility-scale tracker projects can increase profits and minimize downtime. Predicting potential faults and keeping the array in motion is any site manager’s goal, and the tools are available to do so on smartphones and laptops.

Design software that helps utility-scale solar developers save on soft costs AS SEEN IN PVCOMPLETE'S PVSKETCH MEGA Residential installers have had access to tools to assist with designing and selling solar arrays for a while now. Software like Helioscope and Aurora help them automatically view many iterations of module layouts, kilowatt sizes and product types to determine the best fit for each home.

Even commercial projects up to 20-MW can be modeled using existing advanced software. But anything larger than that, and the only option for most developers has been AutoCAD. Typically, a developer would give a team of engineers specific parameters and get a layout back in a few days, according to Daniel Sherwood, president of PVComplete.

Then, if developers wanted to see the project with different parameters, it would take another handful of days of work. And so on.

PVComplete is launching an antidote to that labor-intensive design process in the form of PVSketch Mega.

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PVSketch Mega lets users input multiple parameters for the computer to assess, including fixed-mount or tracking systems, different types of modules, alternative row spacing measurements and more. The software then exports a chart that displays each different layout along with how many kilowatt hours it could produce. The company is also working on building in more LCOE factors, such as fixed costs, maintenance costs and more.

"That layout that took three or four days for an engineering team to do, you can now do in three or four minutes, but you can do a thousand of them in three or four minutes," Sherwood said.

SOLAR POWER WORLD // 2021 RENEWABLE ENERGY HANDBOOK

PVComplete is best known for PVSketch, an AutoCAD software for utility-scale solar. Its new browser-based PVSketch Mega tool communicates with the company's AutoCAD software, so designers can export parameters from the web browser into AutoCAD and finish designing the project offline.

"The amount of money you could save by being smart about these decisions early on in a really big site, it could be millions of dollars. It's no joke," Sherwood said.

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TOP PRODUCTS

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It should be any mounting manufacturer’s goal to ensure ease of use of its products for solar installers when they’re up on the roof.

Reducing trips up the ladder, the number of components and tools installers must carry, the amount of steps to install and the time it takes to install each piece of the system should all be on a manufacturer’s mind — and sometimes a single product design can manage to accomplish all of that.

QuickBOLT, formerly known as SolarRoofHook, was the company that popularized the viability of top-mounts for solar arrays back in 2012. Its namesake product skips the traditional method of prying up composition shingles to slide aluminum flashing underneath for waterproofing. Instead, QuickBOLT goes straight through the shingle and uses a rubber puck dubbed “Microflashing” to keep water out. No pried shingles, meaning fewer chances of roof leaks.

QuickBOLT’s latest iteration, QB2, is three pieces: Microflashing, an L-foot and a lag bolt, and the company claims it can be installed in 30 seconds. The lag secures the L-foot set atop the Microflashing, driven straight into a rafter through the shingle.

While it’s reserved for rafters, QuickBOLT is soon releasing a topmount that can fasten to decking.

Installers and manufacturers see pitched rooftop solar mounting trending toward top-mount solutions, with several companies releasing their own versions in 2020 alone. And given the temperamental nature of asphalt shingle rooftops, any opportunity to reduce potential damage to them is a positive.

SOLAR POWER WORLD // 2021 RENEWABLE ENERGY HANDBOOK

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SOLAR POWER

TOP PRODUCTS Big-wafer solar panels that smash output records AS SEEN IN TRINA SOLAR'S VERTEX LINE OF MODULES Current solar panel technologies are reaching their limit at improving efficiency.

The only way to make solar panels more powerful is to go bigger. But rather than have a massive solar panel that needs to be installed by crane, one way to create a more powerful module in the same-sized footprint is to switch to bigger silicon wafers. Silicon wafers are the building blocks of crystalline silicon solar cells, which string together to become solar panels. The bigger the wafer, the more power it can generate because of its larger surface area.

Many companies have adopted this simple concept and released large-format panels to the utility-scale market in the last year, but one of the first was Trina Solar with its Vertex bifacial modules using the largest wafer size (G12/210-mm). The dual-glass, 12-busbar panel only uses 50 tri-cut cells to reach over 500 W and 21% efficiency. That's a 100-W and 0.5% efficiency increase over Trina's Duomax bifacial module that uses 72 smaller wafers. And Vertex modules are relatively the same size — give or take a few inches in either direction — as what the utility-scale market is used to.

The key selling point for these larger-wafer panels is to generate more energy in less space. By using fewer panels, one can reduce balance-of-system costs. This is an easy sell on multi-megawatt ground-mounts, but some more tweaks are needed to bring big wafers to the non-utility sector. Don't worry though, Trina is already working on that with its Vertex S line, a more compact version of the original Vertex modules.

Inverters that safely maximize precious solar output AS SEEN IN YASKAWA SOLECTRIA’S XGI 1500 Solar installers have to strike a delicate balance to ensure they're getting as much power as possible out of systems without overloading inverters. That typically means oversizing arrays and using inverters that can tolerate more power than they're rated for, with the warranty to back it up.

More inverter manufacturers are now advertising their ability to oversize and accept more power than traditionally thought. Yaskawa Solectria, for example, assures customers that its reliability testing has proven its XGI 1500 string inverter can withstand oversizing without breaking, and its warranty will provide peace of mind should any issues arise.

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The company has found oversizing capability to be especially important to utility-scale installers who need to get as close as they can to their allowed export amount so projects are profitable.

"Being able to hit that limit without having to do other things in the system has immense value to our customers," said Eric Every, product manager at Yaskawa Solectria.

Every said since modules are so affordable, adding a few extra strings to max out production barely makes a dent in a project's budget.

Maximizing solar energy output in a smaller footprint is made easier with bifacial modules. Module manufacturers

SOLAR POWER WORLD // 2021 RENEWABLE ENERGY HANDBOOK

aren't able to give an exact wattage of the backside gain these modules can be expected to produce since it varies based on the amount of diffused light at each specific site. An inverter that can handle a lot of extra DC energy without faulting, like the XGI 1500, is attractive for such projects.

"Being able to have the higher loading ratios allows our customers to actually take advantage of that backside gain," Every said. SPW

SOLARPOWERWORLDONLINE.COM

Congratulations!

2020 LEADERSHIP IN

SOLAR ENERGY Celebrating the companies and individuals leading the solar PV industry.

Solar Power World announces the winners of our Leadership in Solar program. Nominees were released in our January issue, and our user community voted on which companies they felt best exemplify solar leadership. Congratulations to the winners!

BATTERIES

ROLLS BATTERY

MEASUREMENT MEGGER

SOLARPOWERWORLDONLINE.COM

COMPONENTS

ALTECH CORPORATION

MODULES Q CELLS

INSTALLATION SNAKE TRAY

MOUNTING RBI SOLAR

INVERTERS

SUNGROW POWER SYSTEMS

SOFTWARE

AURORA SOLAR

SOLAR POWER WORLD // 2021 RENEWABLE ENERGY HANDBOOK

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SOLAR POWER

BUSINESS

WHAT COVID-19 CAN TEACH US ABOUT EQUITY IN CLIMATE SOLUTIONS

BY MICHAEL KADISH, RENEE SHARP AND NICOLE STEELE • FOUNDING PARTNERS • INSIGHT POWER PARTNERS

AS 2020 careens to its eventual close, among the numerous profound challenges we’ve keenly felt this year are two global crises, the COVID-19 pandemic and the severe present day impact of climate change. These challenges have more in common than you would think at first glance.

Addressing the changing climate, much like overcoming this pandemic, requires multi-pronged solutions at local, national and international levels. They both also demonstrate that a fractured and uncoordinated response is inadequate to address this type of problem.

Most critically, our policies to address both issues must be designed with

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attention to the glaring inequities in our society in order to be effective and fair.

In each crisis we stand at a crossroads.

Our current path to recovery has not only failed to avoid the worst outcomes, but without carefully crafted policies in place, the current recovery could actually serve to worsen the growing inequality in our society.

Continuing to operate under a business-as-usual approach means the impacts of both crises will continue to vary significantly based on income and race in the United States. Look no further than COVID-19 mortality rates among African Americans at more than twice that of whites, or the hospitalization rate of

SOLAR POWER WORLD // 2021 RENEWABLE ENERGY HANDBOOK

the Latinx community at nearly five-times higher than whites.

Frontline communities, from the South Bronx to South LA, already live with existing inequality on a range of issues from healthcare access to locally emitted pollution. They are more vulnerable to the challenges posed by a pandemic or a climate event. It’s part of why we see those elevated COVID-19 mortality and hospitalization rates among many minority communities and why we expect to see even higher childhood asthma rates in low-income communities of color faced with smoke from far away forest fires. The crisis exacerbates the challenges already being endured.

SOLARPOWERWORLDONLINE.COM

SOLAR POWER

BUSINESS

Disparities also happen because in climate terms, the preferred adaptation strategy is not a possibility.

For example, many people have service industry jobs or have been deemed “essential workers” and have no feasible options to work from home.

How many families living near the poverty line can afford to run an air conditioning unit and a HEPA filter every minute of every day of the now annual three-month forest fire season? It is also expected that as the climate worsens, those who can easily adapt by relocating to more climate-friendly locales will do so. This expected climate migration will leave behind climate-stressed frontline communities, now with even fewer local resources to address increasingly greater challenges including rising sea levels, more extreme weather patterns and unbreathable air from ever more massive wildfires. There is already a growing resource disparity available to avoid the worst consequences of inaction in response to both the pandemic and climate change. Most certainly, there is a fundamental injustice in watching some people ignore science, knowing that they have the resources to try to avoid the worst consequences of their own inaction.

But this story is not yet written.

Frontline communities do not have to be left abandoned to the inevitable fires, floods and extreme heat. In fact, there’s a better way, one that builds up local economies and creates jobs while supporting healthy communities by investing in infrastructure that improves local air and water quality.

Our climate solutions can and must focus on helping vulnerable communities successfully

SOLARPOWERWORLDONLINE.COM

adapt to the new reality by prioritizing sustainable investments that create training opportunities and pathways into new highquality green jobs and lifelong careers.

Local community-scale solar and storage microgrids, community cooling centers and cleaner local electrified transportation should be the first among a host of options that can change things for the better today and for the future. In addition, we should build up the sustainability of communities including Detroit, Cleveland, Rochester and others that will likely be called upon to welcome Americans as they eventually relocate to avoid the worst impacts of climate change.

Smart climate adaptation strategies that focus on frontline communities can also help efficiently achieve broader mitigation goals meant to prevent the planet temperature from rising too high. For example “cash for clunkers” programs, that have been

targeted in some states for lowerincome areas, incentivize drivers of the most polluting vehicles to switch to cleaner cars. This provides multiple benefits: reducing local tailpipe pollution by removing thousands of the worst polluting vehicles, saving gas money for struggling families and stimulating the U.S. auto industry. Moreover, the greenhouse gas (GHG) emissions reductions from upgrading from a 1990s Chevy Blazer to a new Chevy Volt are greater than the modest GHG improvements wealthier people enjoyed when they leveraged tax credits for switching from their fuelefficient luxury cars to new Teslas.

Climate solutions can provide a multitude of benefits simultaneously, so when we replace locally polluting

SOLAR POWER WORLD // 2021 RENEWABLE ENERGY HANDBOOK

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SOLAR POWER

BUSINESS

GROUND MOUNT WIRE MANAGEMENT NFI-Hanger • Most cost-effective ground mount wire management option on the market

urban power plants with distributed clean energy and storage, we not only reduce GHG pollution but also improve everyday baseline local air quality and therefore the public health of the most vulnerable populations, all while providing an increasingly important community resilience resource.

There’s also great hope in innovation. Embracing new technologies from vaccines and medicines to energy storage and electric vehicles will be critical to our success in addressing each crisis. Good ideas come from many different places across our nation or world. We should commit to deploying these technologies early in frontline communities so that adoption isn’t a matter of resources, but of need. To succeed at defeating the pandemic and addressing climate change, frontline communities must be at the forefront of solutions, services, products and policies.

They cannot be an afterthought. Let’s learn from these lessons, work together, and effectively take on climate change in a way that reflects our best values. SPW

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SOLAR POWER WORLD // 2021 RENEWABLE ENERGY HANDBOOK

QuickBOLT: The Original Top Mount 8 years ago our competitors said top mount installation methods would never work, installers will never go for it, and you can’t get around lifting shingles. Well that wasn’t good enough. We took the leap anyways, because we believed not lifting shingles was the answer to installer’s problems. We believed solar mounting could be easier.

We heard how traditional flashing was falling short, and we acted. For 8 years since then, installers have been adopting QuickBOLT’s compression-sealing method and for 8 years we’ve continually proven this method to be tried and true for speed and effect. Our recommendation of installing over the shingle has steadily become the fastest growing solution amongst our customers AND our competitors - and we couldn’t be more excited!

Each year that goes by makes QuickBOLT the longest standing top mount solution on the market, and with zero reported leaks. But don’t just take it from us, hear it from YOUR competitors in our customer testimonials. They’ll prove to you why you should try out the QuickBOLT on your next project.

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INSTALLATION

AN INSTALLATION on the capped Cinnaminson Landfill in Vermont by CS Energy.

CONSIDERATIONS FOR SOLAR DEVELOPERS WHEN SITING PROJECTS ON LANDFILLS AND BROWNFIELDS

BY LUCIA WOO • ENVIRONMENTAL PLANNER • LABELLA ASSOCIATES

IN AUGUST OF 2018, the Environmental Protection Agency (EPA) identified over 80,000 brownfields and municipal solid waste landfills across the country that could be used for renewable energy facilities. This screening included maps depicting locations of EPA tracked sites and their potential for supporting renewable energy generation. According to the data, there are 4,498 sites in New York State alone that have been prescreened and deemed suitable for renewable energy development.

There are many benefits to reusing contaminated land for renewable energy, such as greater community support, protection of open space and valuable farmland and possibly shorter project approval timeframes. Many developers have

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adopted strategies to cost-effectively provide engineering controls, as well as activity and land use limitations that allow for safe redevelopment.

With many of the country’s brownfields, closed landfills and underutilized former industrial complexes ripe for redevelopment, there are some important factors developers should consider when reviewing ideal sites for solar development.

Ecological considerations Often, solar developers will overlook wetland and ecological concerns for their landfill or brownfield sites, when in reality, these should be among the first considerations at the beginning

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of the development process. Both landfills and brownfield sites can have cap issues like settling caused from lack of proper maintenance that can create jurisdictional wetlands over time.

In addition, some states regulate upland buffer areas adjacent to wetlands to protect the valuable upland habitat surrounding wetlands. These regulated buffer areas can and often do impede on the developable area within a landfill or brownfield. These sites can also provide unique and protected habitat for endangered or threatened species such as migratory birds, waterfowl, grassland birds, butterflies and dragonflies.

Wetland and ecological regulations differ from state to state and are forever changing at the federal level. As such, it is best practice to involve the right experts to properly address potential wetland and ecological concerns on a landfill or brownfield site to understand any possible project implications a site may have before proceeding.

Remediation history and ongoing monitoring responsibilities It is imperative to identify, evaluate and preemptively address the existing and future environmental issues and liabilities associated with these impaired properties that may contain hazardous waste.

Environmental due diligence is key to accomplishing these objectives by building a thorough understanding of the site’s contamination history, governing regulatory program requirements and ongoing environmental management and monitoring obligations.

Performing an All Appropriate Inquiry (AAI) Phase I Environmental Site Assessment (ESA) prior to land lease or purchase is an effective initial step. The AAI ESA process should be performed in accordance with a national standard established by the American Society for Testing and Materials (ASTM) to ensure consistency in terms of the depth and breadth of due diligence completed.

Information garnered from the ESA process should also be considered when negotiating lease or purchase terms to ensure that the developer is properly indemnified from potential environmental liabilities associated with the site. Lastly, defining all ongoing site management and monitoring requirements can put a developer in a position to establish the owner’s continued accountability and financial responsibility for compliance with these requirements in the lease or purchase agreement.

C2 ENERGY CAPITAL assisted with the development of a 2.7-MW solar array at a capped landfill just outside of Somerville, Tennessee.

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INSTALLATION

Landfill/brownfield cover type and post-closure status Landfills and other disturbed sites such as brownfields present unique challenges when placing structures on top of them.

Landfill capping systems are mainly engineered to isolate the buried waste from the environment, provide a stable barrier to rainfall and minimize the escape of landfill gasses. Brownfields and other formerly used industrial properties may have been filled with heterogeneous materials, which present stability issues for future construction and may have been capped as part of regulatory closure requirements.

It is important when considering solar development on top of these sites to review any available closure and post-closure care plans. Landfills and sometimes brownfield caps are constructed of several different layers of materials such as low permeability clays, geomembranes and topsoil.

Poorly designed caps can, over time, lead to surface water infiltration that can cause uneven settlement and produce a hummocky pattern on the surface. Soil settlement analysis should also be reviewed to document historical settlement, as well as predict potential for future settlement. If no information on how the cap was constructed is available, an intrusive investigation via borings or trenches can be done to document cap construction methods and thickness, which may include geotechnical testing of soil samples.

Civil site design Landfills and brownfields have several features that require deviations from standard civil engineering design for solar arrays. For instance, landfills are typically capped with liners and soils that cannot be disturbed with a pile-driven racking system. Instead, they require a ballasted

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SOLAR POWER

INSTALLATION

system, where the solar panels are held in place by concrete blocks — light enough to prevent unacceptable settlement, but heavy enough to prevent movement or uplift of the solar tables from wind and snow.

Accurate slope analysis is critical, especially for landfills in defining the buildable area since ballasted arrays are suited to more gentle slopes than their pile-driven counterparts. Landfills also typically have monitoring wells and gas vents across the site, for which the solar site design needs to provide adequate clearance for long-term maintenance of the landfill.

When these contaminated sites go through the closure process, stormwater management on a site-wide level should be developed to direct stormwater away from capped areas and to outfalls. This is a benefit since stormwater management has already been considered and might require little to no adjustments for the development of a solar array and associated infrastructure.

Identifying favorable interconnection opportunities within various utility territories Recognizing and evaluating capacity and suitability for interconnection to the utility distribution system is an essential factor in the assessment of siting solar arrays. In comparison to rural greenfield locations, brownfield sites are typically vacated facilities that were large net energy consumers and in the majority of cases comprise an existing electrical service of significant capacity and infrastructure to reduce potential interconnection costs.

Depending on location of the site, utility distribution system resilience is a potential prospect to interconnect a larger capacity distributed energy resource. In many cases, a landfill site will contain a dedicated electrical distribution service that can be assessed as a feeder for a dedicated interconnection.

There are many different factors at play when evaluating the feasibility of a landfill

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INSTALLATION

A SOLAR INSTALLATION on the 230-acre former Emerson Street Landfill in Rochester, New York, by LaBella Associates.

or brownfield for solar development. Specialized knowledge of landfills and brownfields — as well as their regulatory requirements and proven engineering solutions — are key to successful development projects.

It is important to note that not all landfills and brownfields are created equal and different challenges can arise for each project. The site constraints may vary widely depending on the size, topography, microclimate and remediation status. Some sites may contain hazardous waste that requires a health and safety plan and air monitoring for fieldwork that involves excavation. Others may have undergone extensive cleanup activities that preclude the sites from listings on the landfill or brownfield registry.

Redevelopment plans need to be addressed on a site-by-site basis to design an economical and functional solar system that carefully balances risks with opportunities. SPW

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SOLAR POWER

STORAGE

THE BENEFIT OF DC COUPLING STORAGE TO EXISTING UTILITYSCALE SOLAR PROJECTS

BY HANAN FISHMAN • PRESIDENT • ALENCON SYSTEMS

DUKE ENERGY’S McAlpine Solar + Storage project.

ONE LOGICAL TARGET for coupling batteries with solar is hiding in plain sight: The many gigawatts of already-installed PV resources. Duke Energy, one of the largest utilities in the nation, based in North Carolina, is seeking to tap into this opportunity by including energy storage into some of its existing PV arrays and continuing these integrations in the future.

“As more renewables come onto a circuit, the need to optimize that circuit, from the need to provide voltage and frequency stabilization is going to increase.

One of the easiest ways to do that is to utilize energy storage and allow that storage to interact with solar,” said Tom Fenimore, business development for Duke Energy.

“Providing grid stability is an explicit part of our charter as a regulated utility.”

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When looking to add storage to existing PV assets, system owners like Duke Energy have two options — AC or DC coupling. AC coupling of solar and energy storage is achieved when the solar panels and the batteries are connected on the AC side of the inverter — “behind the inverter.”

By contrast, in a DC-coupled topology, solar and storage are connected on the DC side of the inverter — “in front of the inverter.”

While there can be viable reasons to use the AC- or DC-coupled approach for different solar + storage applications, when it comes to installing storage into existing PV systems, Fenimore believes DC coupling presents some very compelling advantages over AC coupling.

One of the major advantages DC coupling offers as a technique for

SOLAR POWER WORLD // 2021 RENEWABLE ENERGY HANDBOOK

integrating storage into existing PV plants is the opportunity to take advantage of the trend of ever-increasing DC:AC ratios. The DC:AC ratio refers to the amount of installed PV panels relative to the AC nameplate of the inverter, which is dictated by the size of the AC interconnect to the power distribution grid.

In recent years, due the falling price of PV panels and improved inverter technology, there has been a trend to increase DC:AC ratios.

Years ago, PV plants were designed with modest DC:AC ratios, typically between 1.05 and 1.1. In more recent years, DC:AC ratios for largerscale solar plants have increased

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from anywhere between 1.5 to 1.8 DC:AC. There are some PV inverters even capable of handling DC overbuilds of two-times the PV to the plant’s rated AC capacity.

All that PV overbuild leads to the possibility of extensive amounts of potential clipped energy — PV production that is curtailed by the inverter when PV generation exceeds the inverter’s power rating.

The DC coupling technique of combining solar and storage allows that excess generation to be diverted into a battery during periods of overproduction.

This captured generation can then be discharged later in the day or in the evening to smooth out the production from a PV plant, turning an intermittent energy resource like solar into a truly dispatchable one. For regulated utilities like Duke Energy that contract with millions of end users to assure the lights turn on whenever they flip a switch in their home or business, being able to accurately control the dispatch of generation capacity is critical.

In addition to the opportunity to capture what might otherwise be clipped (thrown away) energy, DC coupling also offers a system owner some unique financial benefits. According to current government regulations, energy storage can only be claimed under the investment tax credit (ITC) when charged directly from PV. “The key to successfully installing energy storage is doing so with favorable tax or other financial benefits,” Fenimore said. “Once we figure out how to do that as an industry with regularity, we’ll really see the needle move. One of the challenges we’ve had with storage is capitalizing on investment tax credits. DC coupling allows that to happen more easily than AC coupling because we are only able to charge the battery from the solar. Doing so makes it a clear-cut case from a financial perspective where the kilowatt hours charging the battery are coming from.”

As more PV comes onto the electrical grid, there will be a greater need and incentive to pair batteries with existing PV resources to assure the reliable operation of the utility grid and maintain the viability of clean sources of generation. SPW

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SOLAR POWER

MODULES

HOW BACKSHEET QUALITY IMPACTS MODERN SOLAR PV MODULES

BY VIVEK CHATURVEDI • BUSINESS LEADER ENDURANCE BACKSHEETS • DSM ADVANCED SOLAR

IT IS NO SECRET that backsheets in PV modules are not always performing the way you expect. In all climates and in all types of modules, premature degradation can be, to a great extent, attributed to a faulty backsheet. This year’s DuPont analysis indicates that 16% of all modules inspected suffered backsheet failure. Dupont’s data supports previous research on the topic. According to a study by Solar Bankability, 1% of all modules exhibit backsheet failure, and out of all module failures, 9% are linked to the backsheet component.

Putting those percentages in real life application would mean that 1.1 GW of the forecasted 112-GW PV capacity installed in 2020 risks some degree of backsheet failure, which could potentially result in a repair bill of $500 million. It is clear that the widespread backsheet failure phenomenon is turning out to be extremely costly, not only because of the power loss, but mainly due to the accumulating bills for fixing or replacing the PV module.

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Backsheet: The unsung hero of module protection Before delving into analyzing the reasons behind modern backsheet underperformance, it is important we highlight their role in the solar module. The backsheet is the final layer on the back of a PV module, making it the first line of defense. Despite its role to protect the more fragile units of modules from ultraviolet radiation, moisture, wind, dust, sand and various mechanical impacts, traditional backsheets seem to be unable to provide long-term durability, resulting in underperforming PV modules and lower power outputs.

Adding to the complexity of the situation, while it’s often possible to spot a faulty backsheet in the field, it can be extremely difficult for solar park owners and module manufacturers to look into the “black box” of backsheet failure and pinpoint how and why a fault happened. Usually, the backsheet gradually deteriorates to the point of exposing the core layer to moisture and air — causing corrosion of the electrical components, known as the ultimate common denominator behind every failure that marks the countdown in the PV module’s life expectancy. Common symptoms to look for include cracking, delamination, chalking and mechanical abrasion.

The culprit behind this phenomenon is what is known as the “solar coaster.” The industry has been on a turbulent rollercoaster ride economically for more than a decade, where a significant growth in demand and manufacturing capacity has resulted in a tenfold decrease in solar panel prices, mainly due to the use of lesser quality materials and unreliable manufacturing techniques.

But why exactly are backsheets failing?

A weak core: preference for cheap materials such as the low stabilized

PET for core layers is one of the key reasons behind backsheet failure.

Despite being able to provide good electrical insulation, the PET polymer is extremely sensitive to moisture and sunlight – meaning its use in outdoor applications has huge limitations.

One of the solutions used in backsheet manufacturing is to add thin layers of fluoropolymers like PVF (Tedlar), PVDF or highly

SOLAR POWER WORLD // 2021 RENEWABLE ENERGY HANDBOOK

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stabilized PET to protect the intrinsically weak core. This is considered a costeffective alternative to stabilizing the full PET core layer, yet it makes its shelf-life dependent on the outer layers only, which real-life applications have shown to be a short-sighted tactic.

Cheaper, less materials: Under continuous cost pressure, manufacturers keep making the outer protective layer thinner and thinner, while the PET core remains still vulnerable to moisture. The market has been flooded with backsheets where the fluoropolymer outer film’s thickness is less than 20 microns, while in the past this layer was more than 40 microns thick. In some cases, the outer “protective” layer is as little as 10 microns, making the backsheet prone to bigger and faster damage.

Cost-driven manufacturing practices:

Loopholes in the certification process allow for manufacturers to cut corners in production practices like sourcing parts of the bill of materials from different suppliers and laminating them with various adhesives, as these don’t require a re-certification according to the latest regulations. Unsurprisingly, such practices can result in faulty backsheets and, more importantly, in the inability to understand the precise reasons behind every failure.

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The lack of transparency in materials and the inability of basic regulatory tests, like the IEC especially, to predict long-term performance in the field are pushing for more traceability in sourcing and better-quality materials.

All three factors are obviously linked to the prioritization of cost reduction over robust materials that would guarantee the — previously — typical solar module lifespan of 25 to 30 years. Cheaper PV modules are proving to be a costly choice in the long run, as the constant need for replacement options leads to unplanned downtime, replacement and maintenance costs.

The financial benefit of high-quality materials Considered in conjunction with other factors such as O&M reserves and appropriate scope, module manufacturing inspections as well as quality and design life of other components among others, it’s reasonable to assume that quality backsheets are likely to prolong the expected 30-year lifespan of PV modules.

Looking back at the initial question of whether the backsheet damages is a problem that can be avoided, the answer is clearly yes. Backsheets have only started massively failing when the prices of solar modules plummeted, and innovations in solar cells were prioritized above backsheet innovations, for which the cheaper quick fix was chosen. Now, with the proof that cheaper initial cost doesn’t necessarily

SOLAR POWER WORLD // 2021 RENEWABLE ENERGY HANDBOOK

outweigh the cost of sustaining and repairing, performance-focused manufacturers, such as DSM, have been rethinking how to support the industry with long-term reliable backsheets.

Co-extrusion and solar modules One of the most successful processes to replace traditional lamination and the related cost and quality issues is co-extrusion, a manufacturing process commonly used in materials science applications like multi-layer polymer film processing and thermoplastics used in automotive parts. Despite not being a new process in manufacturing, bringing co-extrusion in the solar industry is an innovative approach to replace the outdated traditional lamination process.

It is a single-step process that requires no adhesives, resulting in strongly coherent multi-material products.

Along with co-extrusion, the reinforcement of the core has huge potential too. Having established the relationship between quality materials and quality performance, the answer to the core conundrum lies in the material it is made from. Choosing to use a film made from modified polyolefin (PO) instead of the inferior PET will boost the core’s strength for instance. This solution is specifically designed for superior protection against moisture, excellent electrical insulation, crack resistance and protection against mechanical abrasion and UV – making the backsheet particularly well-suited for extreme environments like floating PV and tropical installations. When used in moderate weather conditions, it doesn’t need any extra protective layer.

For modules that need to operate in extreme weather conditions or that require an extended life, the layer that offers protection would have to be made by a material resistant to UV, abrasion and moisture. Looking more broadly to

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MODULES

the automotive, aviation and energy industries, it’s clear that the Polyamide 12 is the ideal material for this type of function.

Furthermore, having complete control and traceability of the backsheet supply chain is essential to give solar owners and operators peace of mind around their backsheet performance.

Moreover, a transparent supply chain gives visibility and credibility to sustainability credentials. The industry needs effective products that contain sustainable material and that can be economically recycled with a lower carbon footprint. DSM’s backsheet, for example, is fluorine-free with up to a 30% lower carbon footprint than traditional equivalents — and 100% recyclable with no production waste.

At DSM, quality is not an alternative route, it’s a constant aspiration. Fifty years of experience and technical knowledge in polymers have led to a deep understanding of the industry, allowing us to leverage our resources to create cutting edge technology, environmentally friendly and efficient solar products.

Products like the awarded DSM Endurance backsheet, which tackles the issue of failure using a co-extrusion process in manufacturing and the Polyamide 12 extra layer, are great examples of DSM’s leadership in solar innovation. SPW

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SOLAR POWER

TRACKING

CHOOSING THE RIGHT SOLAR TRACKING SYSTEM THROUGH SOFTWARE

BY DANIEL SHERWOOD • P.E., PRESIDENT AND CO-FOUNDER • PVCOMPLETE

AS THE NUMBER OF single-axis tracker manufacturers has continued to grow and diversify, so too has choosing the optimal tracker technology for a given utility-scale solar project become ever-more complex.

One manufacturer may claim short rows are superior because they make it possible to fill every nook and cranny of a project site and better accommodate changing terrain. Another manufacturer might tout the advantages of longer rows and more robust designs as an advantage when it comes to fewer drive motors and less longterm maintenance. Separating fact from fiction and hype from real advantages has been a significant challenge.

Until now.

Advances in solar design software provide a data-driven analytical comparison of tracker technology on a site-by-site basis that cuts through the marketing hype to enable bankable decisions that mitigate risk and improve longterm project performance.

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By leveraging modern cloud computing and data analytics, leading solar software platforms are able to generate project layouts for tracker projects of any size in minutes. This new speed and accuracy makes it possible to produce side-by-side layout comparisons of project designs featuring different tracker systems that reveal key decision metrics such as: • The amount of steel required by each system, • Which manufacturers are best suited to the complexities of a given site and able to maximize rackable area by filling in corners, going around bends, hugging farmers’ fields, following the contours of hills, conforming to the boundaries of cloverleaf highways or circumventing wetlands, waterways and other obstructions, • The number of motors required for each system, providing a better forecast of maintenance requirements and possible points of failure, • Precise computations of ground coverage ratio (GCR), kilowatt output capacity and production values, and • Anticipated foundation installation requirements.

Personal biases in favor of industry incumbents vs. newcomers, centralized vs. distributed architecture, long vs. short row lengths and more can be replaced by data-supported evidence of product suitability. With side-by-side design comparisons, the pressure to identify a universally

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SOLAR POWER

TRACKING

FIGURE 1: 13.6 MW using 90 module rows, drivelines shown in red.

FIGURE 2: The same 13.6 MW in a broken up conďŹ guration doubles the number of drivelines.

FIGURE 3: Using a tracker with only 30 modules per row allows 17 MW on the same site.

accepted tracker can be replaced by an opportunity to assess the best tracker for every unique project, improving project outcomes.

For example in Figure 1, we see a 13.6-MW tracker layout with 90 module rows in square, standard blocks. In this example, using a driveline to drive multiple rows with a single motor can greatly reduce the motor count and therefore the complexity of the EBOS. It also presents far fewer points of failure for plant operations and maintenance.

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TRACKING

FIGURE 4: 90-module rows, modeled on terrain. The middle piles are too tall and will fail structurally.

FIGURE 5: Using shorter 30-module rows will allow the tracker to be installed over the topography without issue.

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Figure 2 shows the same 13.6-MW system with a broken up layout. Using linked rows of 90 and 60 modules will still reduce the motor count, but not nearly as much as in the ďŹ rst example. Also, using shorter tracker rows of 30 modules per row will allow more than 17 MW to ďŹ t on the same site, as shown in Figure 3.

Another thing to consider when choosing the best tracker is topography. Longer tracker rows are typically not wellsuited to slopes and varied terrain. For example, Figure 4 shows a group of 90 module row trackers modeled on top of topography. The piers in the middle section would need to be more than 10-ft tall in order to keep the tracker row in the same plane. This is impractical and would cause the foundation to fail structurally due to the torsion force. Also, because the center of the trackers is misaligned, a single driveline cannot be used. By comparison, using 30 module rows, as shown in Figure 5, allows the piers to remain well within spec.

Examples like these reveal just a few of the side-by-side tracker comparisons that advanced software now enables.

With analytical evidence easily accessible, project engineers are able to identify the best solution for each unique project site, improving bankability and ensuring greater overall utilityscale project outcomes. SPW

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INVERTERS

SOPHISTICATED ASSET MANAGEMENT SOFTWARE CAN MAXIMIZE INVERTER OUTPUT ON LARGE PROJECTS

BY VASSILIS PAPAECONOMOU • MANAGING DIRECTOR • ALECTRIS

CPS AMERICA 1,500-V string inverters.

INVERTERS ARE a vital part of any solar project, ensuring that plants produce the optimal amount of power at all times and providing the key link between photovoltaic systems and the grid or energy offtaker. But despite their increasing sophistication and importance to solar plant electricity production, inverter data is often misunderstood by project owners and operators. This is due to a lack of investment in sophisticated software that can handle complex data — resulting in decreased energy production.

In contemporary solar PV plants, inverters are multi-functional, assisting with grid support related to voltage, frequency, communications and controls. On top of this, smart inverters can use maximum power point tracking (MPPT) to hold voltage and current at the optimal point on a solar module performance curve to maximize power extraction and revenue.

But these additional functionalities are of no benefit to a solar project owner if the inverter is not performing correctly, and in fact can have the opposite

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effect. In 2019 alone, 27% of total lost productivity was caused by offline inverters.

Little attention has been paid to this, and while advanced inverter technology has become more commonplace in solar projects, legacy operations and maintenance software is still being used. Sophisticated software solutions combining enterprise resource planning (ERP) and asset management platforms are available on the market and solar project owners and operators now have an opportunity to effectively manage smart inverters and minimize solar losses.

High-quality data is fundamental to optimizing inverters By performing multifaceted data analysis, combined ERP and asset management software platforms can draw high-quality information from inverters to identify both how they are operating and if they are enabling solar projects to operate at maximum capacity.

In this way, sophisticated systems can uncover the root cause and scope of solar asset failures — whether mechanical or electrical — and track where solar projects are losing revenue. By establishing when and how often inverters are malfunctioning, project owners can be proactive in taking action to avoid future failures and ensure safe system operation.

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Aggregating performance monitoring and financial data To fully understand the impact of solar project failures on the financial performance of an organization, solar PV monitoring data must be combined with wider financial data. More basic asset management software has historically fallen short in this area as it has focused primarily on asset performance without taking into consideration broader trends across the business. This has led to decisions being made on the basis of an incomplete picture, which could lead to further asset damage and revenue loss.

When used alongside ERP software, project owners can centralize data across monitoring, financial and operational aspects of their organizations and draw macro-trends between

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SOLAR POWER WORLD // 2021 RENEWABLE ENERGY HANDBOOK

inverter failures and low solar asset productivity. By identifying correlations between failure rate, asset downtime and expected revenue estimates, sophisticated software can accurately calculate the financial implications of different failures.

As a result, ERP software can enable project owners to more effectively prioritize which failures to repair and minimize revenue impact and asset damage.

By centralizing data, project owners can gain a greater understanding of the operational and financial impacts of inverter and other solar component failures on the broader organization and take swift action to tackle the issue and reduce the risk of it occurring again. SPW

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SOLAR POWER

COMPONENTS

PV CONNECTOR MATING AND INTERMATABILITY IN NEC 2020

BY DAVID BREARLEY • SENIOR PROJECT MANAGER OF TECHNICAL SERVICES • MAYFIELD RENEWABLES SOLAR

THE SOLAR INDUSTRY’S most dangerous misconception might be the deeply flawed notion of PV connector “compatibility.”

As part of the 2020 round of revisions, the code-making panel responsible for Article 690 in the National Electrical Code introduced language intended to reduce performance and safety risks associated with PV module connectors.

If your jurisdiction has already adopted NEC 2020, overlooking this seemingly small requirement could prove consequential and costly. Because of the intrinsic life safety and professional liability implications, industry stakeholders operating under previous NEC editions would be wise to plan ahead for the eventual adoption of these changes.

Missed Connections – Not surprisingly, module connectors are a common failure point in a solar electrical system. There are more connectors, after all, than modules or power converters or overcurrent protection devices. This is especially true with the advent of module-level rapid shutdown, which roughly doubles or triples connector quantities in roof-mounted systems.

Nevertheless, not all PV connector failures are created equally.

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As part of a technical assessment of solar project risk, TÜV Rheinland evaluated different PV module failure modes according to severity of effects, likelihood of occurrence and detectability. According to the results of this Failure Modes and Effects Analysis (FMEA), failures associated with dissimilar connectors represent the single greatest risk to PV system performance and safety. Walmart’s nowsettled lawsuit against Tesla, which hinged in part on roof fires and incompatible module connectors, illustrates high stakes associated with dissimilar connectors.

To understand why mating different types of connectors is such a problem, it is important to recognize that no universal PV connector standard exists. Each product manufacturer designs and builds PV connectors to its own specifications.

Housings from different vendors are made out of different materials; the electrical contacts are made out of dissimilar metals; there are no standard product dimensions or tolerances. These differences lead to failures, some of which lead to fires.

Mating Connectors – Industry experts have long been aware of the problems associated with mating incompatible PV

connectors. Incident investigators and first responders have documented these failures in the field. Testing laboratory personnel have studied connector failure modes and root causes. Trade publications and trainers have shined a light on this issue and shared best practices.

The problem persists, in part, because of misleading advertising.

It is not uncommon for module or module-level power electronics (MLPE) manufacturers to tout their PV module connectors as “MC-4 compatible” or similar. Unfortunately, connector “compatibility” is effectively meaningless. Granted, you can physically plug two “compatible” connectors together. However, a nationally recognized testing laboratory has not assessed and validated the quality, reliability and safety of this electrical connection.

As a short-term solution to a persistent problem, the codemaking panel introduced language pertaining to connector mating and intermatability as part of NEC 2020.

Specifically, Section 690.33(C) states

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SOLAR POWER

COMPONENTS

that: “Where mating connectors are not of the identical type and brand, they shall be listed and identified for intermatability, as described in the manufacturer’s instructions.” Explanatory text in the NEC 2020 Handbook notes: “The term intermatability is used in UL 6703, Connectors for Use in Photovoltaic Systems.”

Standardizing Connections – In the long-term, this NEC change may lead to a much-needed industry standard for PV connectors. If everyone builds and tests mating connectors to the same product safety standard, intermatability is all but guaranteed. Problem solved.

Unfortunately, changes to product safety standards are often slow in coming.

In the meantime, the simplest way to meet the new NEC 2020 requirements in 690.33 is to ensure that connectors on PV modules are the same type and brand as connectors on MLPE devices and DC string conductors. Prior to NEC 2020, plan checkers and field inspectors were unlikely to evaluate PV connectors for intermatability. Installers should not only expect additional scrutiny going forward but also should take immediate steps to mitigate risks associated with dissimilar PV connectors. SPW

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SOLAR POWER WORLD // 2021 RENEWABLE ENERGY HANDBOOK

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SOLAR POWER

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FLOATING SOLAR + HYDROPOWER HYBRID PROJECTS CAN BENEFIT BOTH TECHNOLOGIES

BY EMANUELE QUARANTA • SUBJECT MATTER EXPERT • PRESCOUTER

HYDROPOWER and solar power plants were developed separately in the past. Recently, hydro and solar plants have started to merge into photovoltaic-hydropower hybrid plants, where floating solar panels are installed on the water surface of hydropower reservoirs and/or on the dam surface. This represents a cost-effective strategy for allocating new PV plants without occupying natural lands, protecting dams from insulation and increasing hydropower generation by reducing evaporation losses.

Globally, hydropower represents the largest share of renewable electricity generation, with almost 1,200 GW of installed capacity, where 328 GW are run-of-theriver plants (e.g., hydropower plants without storage reservoirs, or with very small ones). Hydropower is a renewable energy source with benefits for flood control, water management, promotion of leisure activities and stabilization of the electric grid.

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However, a major loss in hydropower plants is the evaporation of water from reservoirs because the evaporated water cannot be exploited by the turbine to generate energy. Meanwhile, PV plants have grown exponentially since 2010, with a total installed capacity worldwide of about 400 GW that is expected to grow in the next decades.

Some of the biggest challenges, though, are that solar projects require large areas, and the warming of panels reduces their efficiency.

Photovoltaic-hydropower hybrid plants In photovoltaic-hydropower hybrid plants, PV panels are incorporated into the hydro plant mainly in two ways: installation of PV panels on the downstream face of the dam, an option only possible in certain plants where the face slope of the dam is below 40° (like in gravity and embankment dams), or floating PV panels on the water surface of the hydropower reservoir.

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In hybrid systems, several benefits are achieved with respect to the independent operation of the solar and hydro plants. In general, hydro plants are easy to access and already grid-connected, thus the installation of PV panels requires less work and infrastructure.

In the former case (PV on dams) the benefits are the following: • PV panels protect the dam surface from direct solar radiation that may negatively affect the stability of the dam itself, reducing thermal excursion of the dam surface and increasing dam durability • PV panels are installed on an existing structure (the dam surface), reducing land use • Energy generated by PV can be used for pumping in pumped-storage hydropower plants

•

PV panels are mounted on an inclined area, minimizing the distance required between two panels with respect to an analogous installation on a flat area, thus increasing solar energy generation

In the case of floating solar panels on hydropower reservoirs, the benefits are the following: • Land use is minimized • The cooling effect provided by water below the panels increases panel efficiency • The shading provided by PV panels on the water reduces algae growth and water evaporation, improving hydro energy generation and water quality • The water surface provides areas free of shading objects along with higher sunlight reflection, improving PV generation

Floating panels can increase the capacity factor of a hydropower plant by 50% to 100%, where the capacity factor of the hydro plant is the ratio of total generated energy to the maximum energy than can be generated if the hydro plant would always work at its maximum installed power capacity. Floating panels can gain 7% to 14% more energy than a land installation due to the reduction of temperature.

However, floating PV has an important limit: It cannot resist strong wind gusts, necessitating a very large number of mooring points in order for it to remain intact. The solution devised by the company Upsolar Floating is based

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on a much more robust concept where rafts are built with polyethylene pipes and steel beams supported by 20 to 24 panels. They have been shown to resist damage by winds up to 140 km per hour.

Real cases and costs Floating solar panels installed on a dam surface can be applied to several dams across the globe. For example, a recent study carried out by the European Commission’s Joint Research Center revealed that the application of such hybrid systems to 10 selected dams in South Africa can generate an annual electricity amount of 72 GWh from PV from an installed peak power of 42 MW. An example of a real project can be found in Japan’s Kutani Dam, with an installed PV capacity of 4.99 MW and a 20-year revenue of approximately $5.4 million.

Today, a floating solar project costs 10% more than a solar plant on the ground, but this higher cost is overcome by the increased efficiency.

The final kWh cost is 20% lower than a ground-based project. The cost for large projects is about $763 per kW,

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all included (mooring, cable, inverters, electric cabinet), while the final kWh price is in the range of $33 to $54 per MWh, depending on the local radiation conditions.

Potential estimation and conclusion By assuming coverage of 25% of the 265.7 thousand sq. km that represent all existing hydropower reservoir surfaces with floating PV, 4,400 GW could be generated (6,270 TWh) that can reach 5,700 GW (8,000 TWh) using all existing reservoirs, both for hydropower and for other purposes. Floating solar could prevent about 74 billion cubic meters of water evaporation, increasing water availability by 6.3% and hydropower generation by 142.5 TWh. This application to water reservoirs worldwide has already been considered, for a total installed capacity of floating PV of 376 MW in China, 22.7 MW in Japan, 9.3 MW in the United Kingdom,

6 MW in South Korea, 4 MW in Australia, 0.77 MW in Italy and 0.67 MW in the United States. Other examples, but at a minor scale with respect to the previously mentioned countries, can be found in Spain, Portugal, France and India.

Due to the advantages of this type of combined hybrid plant, the potential and market opportunities are expected to grow in the future, especially the floating solution, thus reducing the combined (hydro + solar) GHG emissions per kWh produced, particularly in tropical regions. SPW

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WINDPOWER

MARKET OVERVIEW

IT MIGHT NOT SEEM LIKE IT, BUT 2020 WAS SUPER POSITIVE FOR WIND WHILE THERE WERE a few blips, the tumultuous events of 2020 have not threatened the U.S. wind industry's longterm plans. Wind energy continues to be the most affordable source of new electricity in many regions across the country, which will only encourage more onshore development. And the offshore market is taking big steps toward its predicted boom, all in the face of a worldwide pandemic and turbulent political environment.

In March 2020, AWEA estimated nearly 25 GW of wind projects were at risk due to initial COVID-19-related construction pauses. But the industry continued to post record-setting numbers, despite fears. The U.S. installed nearly 2 GW of new wind power in the third quarter of 2020, its best third quarter ever. And 2020 installations outpaced 2019 by over 70%.

The government did step in to help wind developers through short-term headaches due to COVID. The IRS provided one additional year of safe harbor flexibility for projects that began construction in 2016 and 2017 trying to meet production tax credit (PTC) requirements. Now instead of having to wrap up projects in 2020, wind developers have through 2021 to receive the full PTC amount.

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Another positive result of COVID-19 is that more wind farm owners were turning to remote and virtual O&M assessment, according to analytics company ONYX InSight, which accelerates the industry's transition to more efficient practices and decreased maintenance costs. Also of note: Lawrence Berkeley Lab found that newer wind farms are showing less performance decline, further decreasing the need for routine O&M. One area that seems unaffected by COVID-related delays is offshore wind development. Wood Mackenzie still predicts at least 25 GW of installations through 2029, with even more expected if federal leasing is improved and renewable portfolio standards are increased. The East Coast is already forging ahead. New York wants 9 GW of offshore wind by 2035 and this past summer solicitated 2.5 GW of offshore projects. New Jersey requested its own 2.4 GW of offshore wind energy to kick off its 7.5-GW goal by 2035. Rhode Island requested proposals for 600 MW of new offshore wind, after already receiving approval for 400 MW in 2019.

Dominion Energy's 12-MW pilot project off the coast of Virginia Beach completed construction and testing, paving the way for its 2.6-GW project, the first major offshore

WINDPOWER ENGINEERING & DEVELOPMENT // 2021 RENEWABLE ENERGY HANDBOOK

wind project in U.S. federal waters. Virginia, Maryland and North Carolina also joined forces to advance offshore development in the industry through the Southeast and MidAtlantic Regional Transformative Partnership for Offshore Wind Energy Resources (SMART-POWER). Cooperatively, the states will streamline development and bolster offshore supply chains and workforces.

Looking inward, Ohio's 20-MW offshore project in Lake Erie finally has the go-ahead by the state's siting board, after over 10 years of planning.

And maybe the most optimistic news for the industry was the 25-GW by 2030 offshore target included in the OceanBased Climate Solutions Acts introduced to the House of Representatives in October.

National support of offshore wind would only reinforce plans already in the works.

Though the first few months of 2020 were worrisome for all industries and walks of life, the wind industry is unlikely to begin 2021 under further duress. Only positives are on the horizon. WPE

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MAJOR U.S. WIND PROJECTS COMPLETED IN 2020

The Midwest and central southern states remain the primary hub for wind development in the United States, with Texas, Oklahoma, Iowa and Illinois bringing gigawatts of new development online in 2020, despite pandemic-induced disruptions. The country is now looking beyond its onshore borders, catching up to international wind developers as it enters offshore wind construction.

The West Coast is still vying for offshore wind project approvals and a Lake Erie offshore project received approval after a decade, but the biggest offshore news in 2020 was a pilot project completed off the coast of Virginia. This past year saw many project completions in the United States — here are the most significant.

Pilot project for 2,600-MW Virginia offshore wind farm completed

The first steps of construction on the Coastal Virginia Offshore Wind project were completed with a 12-MW, two-turbine pilot installation. The project was the first offshore wind system approved by the Bureau of Ocean Energy Management, constructed in federal waters 27 miles off Virginia Beach. The final offshore wind project will be 2,600 MW, approximately 217-times larger than the pilot project, and is sited on 112,800 acres where developer Dominion Energy is currently surveying to determine the system’s potential impacts on local sea life. The State Corporate Commission approved the large-scale CVOW in November 2018, and it is expected to begin full construction in 2024.

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National Renewable Solutions completes 324-MW interstate wind portfolio in the Southwest

National Renewable Solutions completed the fourth and final phase in its four-project Broadview wind portfolio, totaling 324 MW. The four projects are split between Curry County, New Mexico (241 MW), and Deaf Smith County, Texas (83 MW), and took five years to complete. The Broadview projects were kickstarted by a coalition by the same name composed of NRS and local landowners who acted as leaseholders and investors.

The system is made of 141 Siemens SWT-2.3-108 wind turbines, each generating 2.3 MW of energy. Siemens is providing remote monitoring and diagnostic services on the wind farms.

WINDPOWER ENGINEERING & DEVELOPMENT // 2021 RENEWABLE ENERGY HANDBOOK

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WINDPOWER

MAJOR PROJECTS Mortenson constructs 248.2-MW Oklahoma wind farm amidst the pandemic

Mortenson completed construction of the 248.2MW King Plains Wind Project in Garber, Oklahoma, in September. The wind farm was commissioned by ENGIE North America, with turbine erection starting shortly after COVID-19 lockdowns in April. The project is comprised of 88 2.82-MW GE Turbines and spans approximately 60 square miles. Mortenson acted as EPC on King Plains, which, at peak construction, created approximately 250 on-site jobs and is expected to generate nearly $50 million during its 30year lifespan.

200-MW Reading Wind Facility is offsetting Royal Caribbean Cruises carbon emissions

The 200-MW Reading Wind Facility in Osage and Lyon Counties in Kansas came online in June and is offsetting approximately 10% of Royal Caribbean Cruises emissions production under a 12-year PPA. Renewable Energy Systems developed and constructed the project, which is made of 62 turbines supplied by Siemens Gamesa, who is contracted for up-tower maintenance for 20 years. Southern Power acquired the Reading Wind project in August 2018.

During its construction, Reading Wind created 200 jobs.

Avangrid Renewables’ 307-MW Texas wind farm is supplying power to Nike

Avangrid Renewables brought the 307.06-MW Karankawa Wind Farm online in early 2020. The system spans 18,000 acres, hosted by 64 landowners in San Patricio and Bee counties and is composed of 124 GE wind turbines. Karankawa is supporting the sustainability goals of sports apparel manufacturer Nike and utility Austin Energy. The Texas wind farm is Avangrid’s largest project to date.

306-MW La Joya Wind Farm supports Public Service Company of New Mexico

Avangrid Renewables is expected to complete a 111-turbine, 306-MW wind farm in Torrance County, New Mexico, by the end of 2020. La Joya Wind Farm is sited on 35,000 acres of state trust land, and will supply the Public Service Company of New Mexico with renewable energy. The tax equity from the wind farm will generate more than $41 million directed to New Mexico public schools.

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Missouri electric cooperative powered by 242-MW Tenaska Clear Creek wind farm

Tenaska brought its 242-MW northwest Missouri wind farm online in May. Tenaska Clear Creek consists of 111 Vestas wind turbines installed across 31,000 acres in Nodaway County. Springfield-based Associated Electric Cooperative arranged a 25-year PPA and will provide wholesale power to six regional cooperatives. Construction on the wind farm began in Spring 2019, and Tenaska hired 350 workers and invested approximately $30 million in contracts to regional businesses.

Colorado brings 170-MW Mountain Breeze Wind Farm online

Leeward Renewable Energy's 170-MW wind project in Weld County, Colorado, should be completed in December. Xcel Energy Colorado entered a long-term PPA on the Mountain Breeze Wind Farm that consists of 62 GE 2.3 and 2.82 turbines. Leeward will own and operate Mountain Breeze Wind Farm for the long term.

EDP Renewables completes 200-MW Harvest Wind Farm

EDP Renewables brought online the 200-MW Harvest Ridge Wind Farm in Douglas County, Illinois, in July. The project created 10 full-time jobs. Over its lifetime, Harvest Ridge is expected to contribute $50 million in tax equity to public services in Douglas County. Three customers signed PPAs on the wind farm’s generating capacity: Wabash Valley Power Alliance (100 MW), Walmart (50 MW) and a private offtaker (50 MW).

Final phase of construction finished on 338-MW Texas wind project

Ørsted finished the final phase of its 338-MW Sage Draw Wind project, located on the borders of Garza and Lynn Counties in Texas. The final phase of the project was 120 MW, giving the wind farm the capacity to power 120,000 homes. Sage Draw Wind brings Ørsted’s operational installed wind capacity to 1.3 GW.

Scout Clean Energy constructs 130-MW Bitter Ridge Farm in Indiana

Bitter Ridge Wind Farm, a 130MW wind project, was completed in October. Colorado developer Scout Clean Energy constructed the wind farm in Jay County, Indiana.

Development on Bitter Ridge started in 2016 and construction began in August 2019. The wind farm uses GE 2.82-MW turbines. Constellation, an Exelon company, signed a long-term PPA for the generating capacity of Bitter Ridge.

WINDPOWER ENGINEERING & DEVELOPMENT // 2021 RENEWABLE ENERGY HANDBOOK

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Congratulations!

2020 LEADERSHIP IN

WIND ENERGY Celebrating the companies and individuals leading the wind power industry.

Windpower Engineering & Development announces the winners of our Leadership in Wind program. Nominees were released in our February issue, and our user community voted on which companies they felt best exemplify wind leadership. Congratulations to the winners!

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WINDPOWER ENGINEERING & DEVELOPMENT // 2021 RENEWABLE ENERGY HANDBOOK

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SA F E T Y

HOW DIGITALIZATION AND PRIVATE WIRELESS ARE INCREASING WIND FARM SAFETY AND PRODUCTIVITY

BY DAVID CHRISTOPHE • DIRECTOR OF UTILITY SOLUTIONS MARKETING • NOKIA

AS WIND POWER projects continue to increase their turbine size and move further offshore, the importance of industrial-grade private wireless connectivity only increases. A constant, reliable network enables workers to operate safely and in new ways during construction and operation as they remotely monitor, inspect and optimize wind turbine performance in real time.

Additionally, this connectivity allows for the movement of large amounts of data for digital workflows, implementation of IoT based predictive maintenance and improved voice and video communications.

Ultimately, pervasive and seamless broadband connectivity go a long way toward improving the overall functionality and productivity of the entire wind farm.

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What is private wireless and how can it help?

Long Term Evolution (LTE) is a 4G technology that has long been used for public mobile networks. The growing availability of wireless spectrum for private networks such as LTE (4.9G) and 5G is revolutionizing communications. An industrial-grade version, which is a self-contained, secure, independent and resilient solution, enables wind farm operators to take advantage of this spectrum, in support of two universal use cases.

The first is to provide critical voice communications for workers alongside broadband data and video capabilities, which have traditionally presented challenges at offshore sites. A private wireless network allows workers to stay connected with co-workers, support vessels, helicopters and suppliers. Maintaining clear voice communications between all these different disciplines and organizations is essential for safety, enhancing productivity to reduce the time to deploy and maintenance costs.

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WINDPOWER

SA F E T Y

In addition, broadband provides connectivity to support personal protection equipment (PPE), digital workflows with an ability to share largesized work plans and drawings and use of video for on-site remote support. Not only does this offer greater flexibility for data and voice applications, but it can cover the entire wind farm, transit route and operations at port, rather than being limited by geography. Further, it allows a much higher level of control over security and delivers coverage where public networks have a weak or non-existent signal.

The second use case is about ensuring the uptime and longevity of capital-intensive assets through incremental remote monitoring beyond current SCADA capabilities, and enhancing site physical security. It is essential to monitor wind turbines in order to prevent damage and schedule preventive maintenance. The repair costs associated with a turbine failure are exceptionally high. Estimated costs just to deploy the required crane to an onshore site are in excess of $150,000 (and more for offshore). Compounding this is the lost value of energy that could have been produced during downtime.

As a result, IoT sensor technology for data such as vibration, temperature and humidity, along with cameras for video surveillance, which utilize private wireless networks, play an increasingly important role in enhancing the monitoring of turbines and sites, which would otherwise only be possible through an in-person visual inspection.

Critically, the ability to remotely monitor equipment and schedule maintenance saves money and improves overall safety.

Expanding the possibilities A large number of sensors are required for effective monitoring on wind farms, and each collects data that must be transferred to central computing resources at the wind farm or onshore data center. This requires a pervasive communications network, and though many wind farms have an existing fiber network for SCADA, private wireless is better suited to the task. This is because it possesses the bandwidth and flexibility to not only handle large amounts of data, but

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it can more rapidly and cost-effectively extend connectivity to future sensor additions offering new innovative capabilities.

In particular, private wireless allows for a comprehensive IoT solution that can connect onshore and offshore teams with sensor data from the wind turbines. Each base station provides secure, high bandwidth connectivity, which can reliably interact with turbines, workers and vessels many miles away. This ensures that the entire wind farm area can be covered by one network for all applications with just a few base stations. Plus, it provides a communications platform for exploring various automation, drone monitoring and predictive maintenance use cases in the future.

Enabling data analysis and action Once data has been collected, operators can apply powerful analytics to yield insights to increase productivity and optimize asset lifecycles. Using machine learning, wind farm analytics can adjust asset maintenance programs in real time. Additionally, these analytics provide failure time predictions by drawing on additional sources that include maintenance records, weather and traffic. From this, an optimized repair schedule can be created and implemented. This has the net effect of saving time and money due to reduced downtime and operational costs.

In addition, video from cameras serving as sensors for machine learning enable video analytics to enhance situational awareness. This improves the safety and security of workers and offshore structures.

Technological advancements in digitalization and automation are changing the way that the industry operates. Wind farms are moving further offshore and to more remote land-based operations to meet increased demand. It is therefore more critical to have a pervasive network in place that securely supports increased and advanced communications. This ultimately has the resulting effect of improving safety and optimizing asset performance. Ubiquitous, reliable private wireless can help to ensure the safety of workers, improve productivity and support future capabilities as new use cases inevitably arise. WPE

WINDPOWER ENGINEERING & DEVELOPMENT // 2021 RENEWABLE ENERGY HANDBOOK

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GENERATORS

WINDING DOWN MAINTENANCE COSTS IN WIND TURBINE GENERATOR REPAIRS

BY MARK MEYER • SALES MANAGER • NORTH AMERICA AT SIFCO ASC

It is no secret that the wind turbine market is growing. Seen by many as the long-term answer to the future of power generation, the sector is expected to grow at a CAGR of more than 10% during the forecast period 2020-2025, according to Mordor Intelligence.

However, this renewable energy source still faces stiff competition for electricity sales. Fossil fuel power generation is still cost-competitive in many markets, while other renewable energies like solar power and hydro power are also rapidly advancing and driving down costs.

For wind turbine operators, the challenge is clear – costs must be driven down wherever possible to ensure wind power can continue to have a part to play in future energy generation.

One such area where costs can quickly add up is in the repair and maintenance of the generators. This is especially the case in the bearing journals of the turbine and the slip rings that transfer the current from the rotors to the generator, where wear and tear happens daily.

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When bearing seats and slip rings wear In wind turbine generators, or any generators or rotating machinery for that matter, wear often occurs in the rotating parts of the machine. In the specific example of bearing seats, over time the seat and the bearing ring can wear due to creep and/or fretting. They also can deteriorate from corrosive substances in the air, for example sea salt on offshore wind farms.

As the shaft and the bearing ring wear, tolerances increase, and the bearing fit continues to loosen. Over time, this

WINDPOWER ENGINEERING & DEVELOPMENT // 2021 RENEWABLE ENERGY HANDBOOK

can lead to increased vibrations further exacerbating the problem and, in extreme cases, causing bearing ring failure and bearing seizure. When this happens, the shaft and bearing are likely to be a complete loss and must be replaced at great cost. There’s also the cost of lost production due to the unexpected downtime and emergency swap-out of the generator.

It is therefore of great importance that even small signs of wear on bearing seats get addressed by cleaning the worn area and building the bearing seat on the shaft back to original specifications. Ideally, this will be done during periodic maintenance cycles.

Another component subject to wear and requiring periodic maintenance and refurbishment are slip rings.

Wear is caused by the mechanical action of brushes on the rings, often made worse by micro and macro particles. If oil or lubricant gets on the surface, these particles can create a highly efficient grinding paste which wears down the surface of the ring. Another important

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wear mechanism present in slip rings is electrical discharge from the rotor currents they collect that can create grooves in the rings.

The slip rings themselves are usually made from copper and frequently plated with silver to improve conductivity. As the rotor of the turbine generator spins, the electrical current produced is conducted through the rotating slip ring to a set of carbon brushes. Typically, these brushes are held in optimum position by static brush holders with springs that allow them to move and stay in contact with the slip ring.

However, when these brushes lose contact with the slip ring, electrical discharges occur that damage the rings. Known as ‘friction chatter,’ this loss of contact between the brush and slip ring interface leads to arcing, which first strips away the silver plating on the rings and then the copper underneath it, too.

Once this occurs, not only does conductivity between the rotor and the slip ring lose effectiveness and the efficiency of the power transmission system suffers, but the slip rings will also be damaged.

Repair and renew with selective electroplating Thankfully, spotting the signs of wear and tear is becoming easier. Advanced diagnostic equipment like sensors and computer modeling, along with preventative maintenance procedures, can usually stop components from getting damaged beyond repair.

Once wear is spotted, it then becomes a choice of what restoration method to choose. For bearing seats and slip rings, selective electroplating is a proven, efficient and economical way of performing these repairs.

Also known as brush plating, this surface treatment technology, such as the SIFCO Process, is a portable plating method used to enhance, repair and refurbish localized areas on manufactured components.

The process uses fundamental electrochemical principles. An electrolyte solution, which contains ions of the metal to be deposited, is introduced

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between the negatively charged part to be plated and the positively charged plating tool, or anode. A portable powerpack provides the required direct current and allows precise control of amperage, voltage and plating time for high quality and accurate plating results.

The circuit is completed when the anode touches the surface of the part to be plated. A suitable wrap around the tool provides a reservoir to evenly distribute the electrolyte. The current causes the metal ions in the electrolyte to bond with the surface of the part and build up the plating layer.

Compared to alternative methods of repair available, selective electroplating has a number of key advantages.

Less preparation and machining The first of those reasons is in preparation of the components for repair. Selective electroplating is a precisely targeted approach to repairing a damaged area. Preparation of the area to be plated requires minimal pre-plate machining. All that is needed is to clean up any corroded, fretted or otherwise mechanically damaged area in order to have a smooth starting area.

In fact, the less material removed, the better and the quicker the repair can be completed. Slip rings frequently require no machining but can be prepared by manually smoothing.

Because selective plating is precise, minimal masking is required too. Repairs are targeted only at the worn areas, making brush plating also highly suitable for repairing small slip rings or grooves as small as a 1/4-in. in width and depth.

With alternative repair procedures like welding and thermal spray, much larger amounts of the original material need to be machined away. This is so they can provide sufficient final

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layer thickness to give the repair enough strength and provide reasonable adhesion. Not only does this take more time during the preparation phase, but it can lead to other issues too.

High strength, durability and bonds For bearing seats in particular, which are subjected to high loads, these other issues can include fundamental changes to the original component’s specification and properties that can create structural weaknesses.

Selective electroplating overcomes these issues as technicians can build the bearing seats and slip rings back to nominal specification by adding only minimal plating thickness that also has excellent adhesion. Using a metal plating like nickel, hardness and toughness can be tailored to meet the requirements of the original component.

This means the component performs as it is expected to, if not better. With other methods, due to the way that they can change the metallurgy or because of how much of the original component is machined off, a suitable repair may not be feasible without introducing risks of stress fractures or cracks when under operation.

As well as no loss of structural integrity, selective electroplating also creates a bond on the atomic level which is much stronger than the mechanical bond which thermal spray relies on. The atomic bond of selective plating with the SIFCO Process is resistant to cyclical temperature fluctuations and direct impact. The dense, non-porous structure that can be achieved with selective plating provides excellent corrosion protection, frequently surpassing that of the original base material, making it much more durable.

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Tests run in accordance with ASTM C633‑13 on the SIFCO Process show that two commonly used nickel deposits had a bond strength exceeding the strength of the bonding agent used in the test.

Little to no post-repair processes Selective plating is done at or near room temperature and, unlike welding, does not change the metallurgical structure of the base material.

Therefore, selective plating requires no post plating heat treatment to restore the original properties of the base material.

Welding and thermal spray also deposit thick coatings that always require post plating machining to bring the part back to specified dimensions. In many cases, selective plating can bring a part back to original dimensions without the need for post plating machining, or only requires minimal machining. In the case of slip rings, light hand sanding to create the desired surface finish can suffice.

Another advantage of selective plating is that different materials can be seamlessly deposited on top of each other. An example of this is if a slip ring is badly worn beyond the original silver layer and into the underlying copper. Selective electroplating allows technicians to first build the copper back to the dimensional specification and then add the silver for enhanced conductivity and lubricity on top of the copper, all in the same plating session.

Why not go tank plating?

Electroplating can also be achieved by the process of tank plating, which is based on the same electrochemical principles as selective plating.

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Unlike the SIFCO process, which uses a minimal amount of electrolyte to target the repair to precise areas, tank plating involves completely submerging the part to be repaired in a tank of solution to electroplate it.

This requires extensive masking of that component so areas that do not need to be plated are not affected. In the case of most repairs, the area requiring plating is relatively small compared to the overall part. Masking most of a part is time-consuming and costly.

Plating time is also much longer and more expensive with tank plating, in comparison to selective electroplating. This is because of the way the two methods differ during the exchange of electrolyte solution.

Due to the brushing action of selective plating, this disturbs the boundary layer in the electrolyte during plating. This then ensures a good exchange of fresh electrolyte solution continuously reaches the surface of the part, and metal content of selective plating electrolytes can be higher than in those used for tank plating. These are two of the factors that result in plating rates that can be 50-times higher than in a tank.

Environmentally speaking, brush plating is also much friendlier.

Unlike tank plating, brush plating uses only small amounts of electrolytes. This results in less evaporative loss and less waste.

Brush plating equipment is small, lightweight and portable.

This allows the process to come to the part, eliminating the need to ship a large part to a specialist plating house. This saves time

and shipping cost, which with the typical size of components in the power generation industry can be significant. SIFCO ASC has even performed up tower repairs. When talking about generator components, in most cases they are usually too large to fit into a tank typically used for tank plating, thus eliminating tank plating as an option altogether.

All of this means that selective plating tends to be the more cost-effective and viable of the two electroplating methods.

Selective plating can change the future of the wind power industry While there are continuous calls to use renewable energy sources to fuel power generation, this can only be achieved if it is economical.

For wind farm operators, this ultimately means that they must continue to find ways to bring expenses down, whether that is from initial installation, operation, maintenance and servicing or otherwise.

Brush plating presents operators with the answer to two common wear issues seen in wind turbine generators: bearing seat damage and slip ring wear. By being able to repair and build the thickness of these components back to specification in a fast and economical way, they become longer lasting, and capital outlay is reduced by not having to replace parts.

In one small way, this can help bring about the winds of change and lead to a future where wind power leads the way to a world powered by clean energy. WPE

WINDPOWER ENGINEERING & DEVELOPMENT // 2021 RENEWABLE ENERGY HANDBOOK

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WINDPOWER

LIGHTNING

LIGHTNING, WIND TURBINES AND FORCE MAJEURE — A RISKY MIX

BY M. MALKIN AND A. BYRNE • DNV GL

LIGHTNING DAMAGE is a concern for operational wind projects around the world.

Disputes between wind turbine owners and manufacturers regarding lightning damage to wind turbines, most commonly to blades, are at the intersection of technical and commercial spaces. Further, the interaction between lightning and wind turbines carries considerable uncertainty, in that the intensity of lightning is difficult to know with confidence and the damage it causes is unpredictable.

Commercial contracts, such as turbine supply agreements and service and maintenance agreements, typically treat lightning as a force majeure event, and responsibility for repairs (or replacements) and associated costs, such as lost production due to lightning damage, are not typically covered by warranty provisions. As a result, when lightning damage occurs, turbine owners are often in the position of paying the costs related to the damage. Insurance may provide coverage, depending on the specifics of the insurance policy. Insurance policy language and premiums may reflect perceived risk levels.

Lightning protection systems (LPS) are designed to minimize the risk of lightning damage. Some damage is expected from extreme strikes; however, damage that impairs the function of the turbine is expected to be limited to extreme lightning events —

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LIGHTNING

When lightning damage occurs, problems may arise for owners and insurers because of the combination of two factors. First, contracts typically consider all lightning damage force majeure and assign responsibility for rectification to owners regardless of whether the damaging event was within the design capability of the LPS or not. Second, it is typically unknown if the lightning event was within, or outside of, the design capability of the LPS; therefore, it is not possible in most cases to use the lightning characteristics relative to the LPS design capability as the basis for assigning responsibility.

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lightning events that exceed the design capabilities of the LPS. As a parallel, extreme weather events (e.g., tornadoes) may be expected to exceed design conditions for wind turbines and cause damage.

Contracts will define in each of these scenarios what constitutes a force majeure event.

There are good reasons to change the current practice of considering lightning a force majeure event.

Modern wind turbine LPS design is intended to safely intercept most strikes and conduct the lightning energy safely to ground. LPS are designed and tested to standards such as IEC 61400-24. This design and test effort suggests that lightning, similar to excessive wind speed or wind turbulence, is an environmental effect against which we can engineer effective protection.

Given that the LPS has design requirements, it seems unreasonable to treat all lightning as force majeure.

If not all lightning is considered force majeure, then contracts should identify an effective means for assigning responsibility when lightning damage occurs. Factors to consider when drafting contract language include: • Lightning damage not being a force majeure event by default.

• Clear definition of “function-impairing damage.”

• Consideration of uncertainties in the assessment of LPS performance, with possible adjustments of assigned responsibility between the turbine manufacturer and owner based on those uncertainties.

• A path for dispute resolution, such as consultation with an independent third party.

Turbine-mounted lightning measurement devices, with appropriate verification of function and calibration, provide an opportunity for reducing the uncertainty associated with assessing the intensity of damaging lightning strikes. In the event that function-impairing damage occurs, then the results from the measurements could be compared to the design capability of the LPS, informing assignment of responsibility for remediation.

Removing lightning from force majeure clauses has the potential to drive improvements in LPS technology. As turbine tip heights increase, the effects of interaction between lightning and wind turbines are likely to become more uncertain. Installations of turbines continue, and unless current contractual practices change, lightning damage will continue to be a contentious and challenging problem for wind turbine owners and operators. WPE

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BOLTING

WHY DO BOLTS LOOSEN?

BY JULIE PEREYRA • SALES ENGINEER • NORD-LOCK GROUP

DEPENDING ON the application, bolt loosening can have profound consequences.

One loose bolt can bring a whole production plant to a standstill and cost a company thousands. In other applications, loose bolts can pose a significant safety hazard. So, why do bolts loosen?

Broadly speaking, there are two main causes: 1. Spontaneous loosening – shock, vibration, dynamic load 2. Slackening – settlement, creep, relaxation “The main causes and the consequences of failure depend on the purpose of the bolted joints, on the environment and usually on the industry,” said Georg Dinger, Siegenia-Aubi KG, who has studied the causes and effects of selfloosening of bolts extensively.

“For example, the petrochemical industry is primarily concerned with corrosion problems, while fatigue and vibration loosening are usually of minor concern. On the other hand, the automotive industry would probably name selfloosening and corrosion as the two main problems. The primary concerns for the

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structural steel industry are joint slip and corrosion, but self-loosening and leakage are less common. The aerospace industry would probably list fatigue first.”

Repeated relative displacements between the contact surfaces, which are under the influence of the shank torque and result from the thread pitch torque, can lead to a gradual rotation of the bolt or the nut.

“This causes a bolt preload loss and consequently a loss of function in the bolt connection. The effect is well known, but prevention is usually performed experimentally only after the occurrence of self-loosening events,” Dinger said.

An ounce of prevention To prevent spontaneous bolt loosening, the slip between the joined parts needs to be eliminated or at least reduced to below critical levels. This can be achieved by increasing the axial tension or the friction between the clamped parts or decreasing the cyclic loading (for example, shock, vibration or cyclic thermal loading).

Another common method is to increase the friction between the bolt threads.

Although there are several effective ways

WINDPOWER ENGINEERING & DEVELOPMENT // 2021 RENEWABLE ENERGY HANDBOOK

to do this, some have disadvantages worth considering.

For example, glue or adhesives can be an effective friction-based method, but dried glue can be problematic when dissembling and removing the bolt.

Furthermore, increasing the friction between threads would decrease the achievable preload at a specific torque level. Locking wire is a common method in the aviation industry.

Fatigue is permanent damage or deformation in the bolt and clamped parts.

It’s caused by loss of preload resulting in an opening in the joint. Spontaneous loosening and slackening are the two basic mechanisms for loss of preload.

Essentially, spontaneous loosening or rotational self-loosening occurs when a bolt rotates loose because of shock, vibration or dynamic loads. Even a slight rotation can be enough for a bolted joint to lose all of its preload. This is the most typical cause of bolt loosening.

Slackening is caused by three mechanisms: settlement, creep or relaxation.

“Settlement is critical when it happens due to dynamic loads. It is the permanent

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BOLTING

deformation of the clamped material when the joint is subjected to the increase of stress from dynamic working loads,” explained Harlen Seow, technical manager with the Nord-Lock Group. “Most parts of a bolted joint will revert to shape after being released if the stress in the parts has not gone beyond their yield strengths.”

This means some materials in the contact surface, such as paint, will most likely deform permanently.

Creep is a permanent deformation that occurs due to long-term exposure to high levels of stress below the yield strength of the materials in the joint. It’s more severe in hightemperature applications.

Relaxation is when the microstructure in the materials of a joint restructure, converting existing elastic deformation to plastic deformation over a period of time. Unlike settlement or creep, the clamp length does not change, which makes it more difficult to detect.

“One way to measure preload loss is to measure bolt length after a period in operation and compare to the bolt length immediately after tightening,” Seow said. “However, this will not detect relaxation, which makes it more problematic.”

The key to avoiding fatigue is good design, which has grown in importance in recent years because of the increased demands on many bolted joints and increased use of lightweight materials. It’s important to avoid solely focusing on the tensile capacity of bolts while overlooking other parameters — such as elasticity and stiffness, which can also be important.

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“Correct joint design is the key to achieving a high strength friction grip connection with a high preload level, and thus a high slip resistance over the entire lifetime,” Dinger said. “Up until now the focus for design engineers has been on the failure with bolts breaking.

Other failure mechanisms have become more and more important as performance is increased and the weight of joints is decreased. The mechanisms of preload relaxation and self-loosening are more and more common in lightweight designs.”

Depending on the bolt, the application and the cause of preload loss, there are generally multiple options for designing more optimal bolted joints.

“In cases where there’s thermal loading, the joint can be optimized by choosing materials with equal thermal expansion coefficient for the clamped parts,” Dinger said. “To help minimize settlement and maintain a high preload during operation, you can reduce the roughness between contact surfaces. Measures such as fine hole diameters or toothed surfaces can help minimize relative displacement.”

Overall, achieving the optimal bolted joint involves factoring in multiple variables and design options.

“In general, a good bolted joint is made up of very elastic bolts and very stiff clamp parts, and there are different ways of achieving this,” Seow said. “One way of improving bolt elastically is to have long clamp length. But if you have a flange, where the clamp length can’t be too long, you can change the design by using more but smaller bolts. So instead of using five bolts, you can use ten smaller bolts, which will create a more elastic joint.” WPE

WINDPOWER ENGINEERING & DEVELOPMENT // 2021 RENEWABLE ENERGY HANDBOOK

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OPERATIONS & MAINTENANCE

POLYMERIC REPAIR: AN ATTRACTIVE AND CONVENIENT SOLUTION FOR DAMAGED WIND TURBINE SHAFTS

BY ARTHUR MENDONÇA • TECHNICAL SERVICES ENGINEER • BELZONA

AS WITH ANY OTHER piece of equipment, shafts are subject to damage from corrosion and wear that can be accelerated by specific environmental conditions, insufficient lubrication of mechanical components or improper grounding for galvanic isolation.

Worn and defective shafts can not only accelerate the wear of other components, but they can also potentially shut down the entire machine, halting production and resulting in revenue loss. Once damaged, they are conventionally repaired using hot processes, such as welding or metal spraying, and then machined down to the specific design parameters. If not carefully controlled, these conventional methods can cause residual damage to the shaft by generating potential thermal stresses, distortion and undesired metallurgical alterations.

These repair methods also require the disassembly of the machine, which can be time consuming and expensive when considering the downtime of the equipment.

In the wind turbine industry, replacement or disassembly generally involves contracting a crane service, lowering the components, transporting them to a fabricating shop and re-assembling the machine. This process can take weeks to be completed.

The repair method The problem and limitations of conventional methods can be avoided by using polymeric nonmetallic compounds in a cold applied

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in-situ repair solution. The repair consists of injecting or forming the nonmetallic repair material using split formers. Such formers are pre-fabricated considering the design dimensions of the shaft being repaired. The repair procedure can be carried out in situ without the need for specialty equipment or hot work permits. Nonmetallic materials needed for the application are readily available and the standardized application procedure allows contracting or incumbent personnel to be effectively trained within hours.

Avoiding the disassembly of the system represents one of the biggest advantages of polymeric repairs over conventional methods because downtime and its consequential production losses are greatly minimized.

Different polymeric materials can be used to repair and rebuild shafts suffering from metal loss. However, some applications require products that can withstand harsher demanding service conditions than others without failure, including elevated temperatures, corrosive marine environment or the combined action of erosion-corrosion. In addition, the repair system must be designed so that the operational limitations of the rebuilding compound are not exceeded within the desired lifetime of the shaft being repaired.

At least one manufacturer of nonmetallic polymer compounds recommends the use of 100% solids epoxy materials in environments prone to corrosion and wear. These 100% solids epoxy materials can be chemically designed

with superior properties to withstand the environmental conditions to which they may be exposed.

Some of these properties include: • Solvent-Free Materials – 100% solid epoxy rebuilding materials are designed so there are no volatile compounds leaving the adhesive material through evaporation at normal temperature and pressure. Thus, it is safer for the applicators to use, especially in confined spaces or small habitats.

• Quick Return to Service – 100% solid epoxies cure through exothermic reactions. The heat generated by the chemical reaction influences the drying times. Quick curing indeed provides a definite appeal for asset owners as it enables quick project turnarounds.

• Excellent Resistance to Compression, Tension and Corrosion – Solvent-free epoxies have superior tension and compression strength when compared to other solvented rebuilding materials. In addition, they can perform well in highly corrosive environments.

WINDPOWER ENGINEERING & DEVELOPMENT // 2021 RENEWABLE ENERGY HANDBOOK

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OPERATIONS & MAINTENANCE

At least one 100% solids epoxy manufacturer subjects its products to sensible testing protocols to ensure conformance with the most stringent standards set forth by the industry. These tests not only help us understand the performance of the product and fitness for service, but they are also useful to fully characterize a material.

Manufacturers decide which tests will best highlight their product properties; then, they employ a range of internal and external testing to verify the product’s performance. Some manufacturers benchmark their products to the requirements of internationally recognized industry standards such as ISO, ASME and ASTM. This allows asset owners to establish comparisons among different products and select those that best fit their needs. However, most asset owners are usually interested in performing further tests to simulate an environment that resembles their service conditions.

FIG 1. Isometric view of assembled component with split former

FIG 2. Front view of split former for injection of fluid grade epoxy material

FIG 3. Lower and upper sections of split former

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Case studies — The problem During the maintenance schedule of a wind farm, the nacelle of the wind turbine was removed to inspect its internal components. Inspection revealed moisture ingress in the nacelle due to the humid environment and improper weatherproofing of the external surface of the turbine. Excessive humidity inside the turbine and lack of lubrication caused the shaft to corrode and wear, respectively. As aforementioned, the metal loss on shafts can cause inefficient operation of the mechanisms inside the nacelle.

Repairs were required to prevent further corrosion and reinstate the operational efficiency of the components. Two conventional approaches were first considered: replacement and welding. Replacing the generator shaft for a new one would require the contracting services of a crane and proper installation and reassembly of the shaft into the nacelle. The cost of such procedures was estimated to be $300,000, not to mention the monetary impact of a two-week downtime and a non-operational turbine. The second

WINDPOWER ENGINEERING & DEVELOPMENT // 2021 RENEWABLE ENERGY HANDBOOK

option considered was to lower the equipment and transport the shaft to a fabricating shop for weld repairs to be performed. Although this option was $25,000 cheaper than the first option, doing so would also require a crane contractor and transportation logistics. The time estimation was also from two to three weeks.

To avoid excessive disruption of the operation of the turbine, a third option was proposed to the asset owner. This unconventional solution was a suitable in-situ repair using nonmetallic 100% solids epoxy polymers.

The repair could be completed in 24 hours for different diameters shafts operating in the nacelle.

Applying the solution Before commencement of any maintenance procedure, all personnel involved in the repair gained full understanding of the repair extent, procedure and application logistics. Although both hand-applied forming and injection technique had demonstrable in-field testing evidence and success track records in different industries, the injection technique was chosen as the preferred method of application for this repair. After discussing different options, the following application method procedure was implemented: • Design: The split former was constructed as per design (Figure 1) to be consistent with the length of repair area and diameter of the shaft being repaired (Figure 2). Holes were drilled and threaded to serve as injection and venting ports for the 100% solids epoxy fluid grade material (Figure 3).

FIG 3

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OPERATIONS & MAINTENANCE

FIG 4. Repair area after surface preparation

FIG 5. Clamping the split mold into place

FIG 6. Injection of 100% solid fluid grade epoxy through pneumatic injection gun

FIG 7. Product allowed to cure after application is completed

•

•

•

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Surface Preparation: The damaged area of the shaft was mechanically prepared to the requirements of SSPC-SP11, Power Tool Cleaning to Bare Metal. A rough surface and minimum average profile depth of 1.6 mm around the circumference of the shaft were achieved to optimize the adhesion of the 100% solid epoxy to the substrate (Figure 4).

A release agent was evenly applied onto the internal surfaces of the split former to facilitate removal of the former after full cure of epoxy material.

The formers were then placed around the damaged area. The length of the former was confirmed to extend beyond the damage area to proper seal and mold to

•

•

•

the dimensions needed. Once properly aligned, the former is clamped by using 4 M10 bolts (Figure 5).

The fluid grade 100% epoxy was mixed in accordance with the manufacturer’s instructions and then poured into the injection cartridge. The cartridge was inserted into a pneumatic injection gun and injection procedure commenced. The material was slowly injected until the cavity was filled. This was confirmed by the product exiting through the ventilation ports. Injection ports were capped with a bolt as the product reached them.

The fluid grade epoxy was subsequently allowed to cure in accordance with the manufacturer’s recommendations. The ventilation ports were removed, and the application was completed (Figure 7).

After full cure of the fluid grade epoxy, the former was removed. The product was mechanically abraded by a fine sandpaper to smoothen any flashing and possible protuberances caused by the injection and venting ports (Figure 8). To remove the formers, extraction jacking bolts were used in each side of the mold.

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OPERATIONS & MAINTENANCE

FIG 8. Injection application completed

Conclusions Several conclusions can be drawn: 1. Using cold applied 100% solid epoxies is an effective and proven solution for shaft maintenance when conventional repairs such as welding and replacement are not feasible.

Such polymeric materials allow for equipment or assets to be repaired in situ, with no heat, and in an easy and safe manner.

2. This method offers the best compromise between cost and performance when compared to shaft replacement and welding repair procedures. Without the need for disassembly of the equipment and with faster turnaround times, the cost of the epoxy material solution is quickly offset by the savings in production and revenue loss caused by extensive downtime.

3. When repairing wear and corrosion damage of shafts with a non-metallic material, the root cause of the problem is being solved. 100% solid epoxies will provide excellent corrosion and abrasion resistance to minimize future wear mechanisms. WPE

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OFFSHORE

WHY SEA FASTENING IS CRITICAL TO SAFE AND EFFICIENT OFFSHORE WIND INSTALLATION

BY MARK GOALEN • OFFSHORE ENGINEERING DIRECTOR • HOULDER LTD

THE OFFSHORE WIND MARKET is maturing rapidly as the world transitions to cleaner energy. Indeed, the BP Energy Outlook 2019 anticipates significant growth of the sector, suggesting that the percentage of generated wind energy in the renewable market will be more than double by 2040. Meeting this rapid growth in demand presents huge challenges in design, technology and engineering. To make the transition economical, wind farm developers and operators are prioritizing efficiencies in cost and performance across all aspects of the operation.

Sea fastening is the routine practice of fastening cargos to the ship for transport, either to the site of installation or transit

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from port to port. As component sizes increase, the challenge of transportation becomes more acute. Executed properly, sea fastening enables the safe and efficient transportation of project equipment, minimizing the number of trips required to install the wind farm equipment. This critical stage of the installation process must not be underestimated — not least in terms of the value it has the potential to deliver.

Sea fastening, but not as you know it Over the last 30 years, the blade diameters of offshore wind turbines have more than quadrupled. Indeed some of the newest blade designs are double the length of a Boeing 747, and it is anticipated that this growth will continue.

As experience is gained, and the technology

WINDPOWER ENGINEERING & DEVELOPMENT // 2021 RENEWABLE ENERGY HANDBOOK

develops, the turbines get larger to generate more power.

As the components increase in size and at a significant rate, the industry is pondering the optimum design for the next generation of installation vessel. In the meantime, however, the existing fleet is being pushed to the limit.

Particularly as there is commercial pressure to maximize the amount of equipment on the vessel per trip to help decrease the overall cost of offshore wind farm installation. This significantly increases the project risks associated with transportation and installation.

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OFFSHORE

The importance of sea fastening in this context is often undervalued — this is not as simple as a standard offshore container sitting on a deck well within the allowable variable deck load. For today’s wind farm installations, the components do not only differ in size and weight, but also shape. The blades need to be transported in racks, the monopiles in cradles, and the towers on grillages; all of which must be designed to fit. This is sea fastening, but not as we knew it.

Stability and motion analysis informs effective design When particularly large equipment is secured to a vessel, the loading conditions must be checked to ensure the vessel remains stable and within the operationally compliant restraints of draught and trim.

Additionally, the weight and height of these components adjusts the vessel’s motion characteristics. Therefore, bespoke vessel motion must be derived to determine the forces the equipment will impart into the hull as the vessel rolls and pitches while at sea. The length of the blades and sometimes monopiles means that they can overhang the edges of the hull, meaning additional green water analysis may be required.

The structural analysis, design and engineering work follows confirmation of stability and the determination of vessel motions. It is essential that the structural interface for each piece of equipment is designed to transmit the loads into the vessel structure without overstressing and damaging the hull or the connecting interface.

For jack up vessels, it is also important to check hull strength in the jacked-up condition, and that the forces pushing down on each of the legs does not exceed the allowable seabed limitations. The leg forces can vary significantly when the vessel crane lifts the wind farm components, and so several scenarios must be considered.

Integrated thinking across structural analysis, design and engineering Experienced, practical analysis is essential to ensure proper securing and sea fastening of high-value cargoes to guarantee a project’s success. Developing an offshore wind farm involves specific and expert engineering, from concept design to installation, into operation and finally decommissioning. Every element is closely interlinked and therefore decisions must not be taken in isolation — the wider picture must always be considered.

This is why analytical capability alone is insufficient; structural analysis is just one piece of the puzzle. There is a seamless chronology between understanding stability and vessel motions before then delivering on design. For example, what are the

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.08 .05 800.359.0372 • NTCWIND.COM .0625 • JWBRUCE@NTCWIND.COM .0625 .14

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practicable options when an allowable vessel limit is exceeded or is so close to exceedance that further calculation is required to prove it is acceptable?

Every decision has a knock on effect, which is why — throughout the entire process — considerable experience is needed across each and every element to engineer reliable solutions that facilitate safe, timely and costefficient delivery.

Progress necessitates change in the swiftly advancing offshore wind space, particularly as global societal pressure increases the move to cleaner energy sources, while development costs continue to be driven down. To safeguard investment, protect assets and maximize efficiencies, integrated design and engineering remains critical in navigating the evolving challenges of this swiftly emerging sector. WPE

It is common to install the foundations,

For the turbine typically in one trip you may install:

transition pieces and monopiles in

•

4-6 off towers typically 6-m in diameter and 85-m high,

one campaign, and then the turbine,

weighing in at 350-400Te each, that would need a deck

towers, nacelles and blades in a

grillage that was 30-m long, 20-m wide, 1.5-m heigh which

separate campaign.

in itself weighs 250-300Te.

For the foundation campaign typically: •

2 off TPs approximately 400Te, supported by a grillage that is

•

•

4-6 nacelles 20-m long, 8-m wide, 10-m high and typically weigh 350Te each (4-6 off), fixed directly to the deck.

•

12-18 blades 75-m long, 30Te each, supported by a root end

20-m long by 10-m wide by 1.2-m

and tip end blade racks that are structures typically 20-m

high and weighs 100Te.

high by 20-m wide and 10-20-m long, weighing 20-50Te.

2 off monopiles 5.5-m in diameter,

•

Blade racks usually sit on a substructure that is

65-m in length and weigh up to

typically substructure 20-m by 20-m by 6-m and weighs

550Te supported by cradles, that

approximately 50Te.

can be 10-m long, 6-m wide, 8-m high and weigh typically 50Te.

72

WINDPOWER ENGINEERING & DEVELOPMENT // 2021 RENEWABLE ENERGY HANDBOOK

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WINDPOWER

PITCH CONTROL VALVES

PITCH CONTROL VALVES: BUILT TO LAST LONGER AND LOWER O&M COSTS

BY EDUARDO GIMENEZ • CEO LEN KASTER • PE, CFPE, TECHNICAL SALES SUPPORT MADELINE HANLEY • TECHNICAL MARKETING AND SALES ALA INDUSTRIES

THE UNITED STATES is a leader in wind energy — wind generates 7% of the electricity Americans use. But it's still behind the Europe Union, which receives 12% of its electricity generation from wind turbines.

The two markets also show differences in O&M, something that should not be ignored in the still-growing American industry.

Blade maintenance is continuously being refined as a fine science, but one of the largest issues is the difficulty in controlling pitch. A sophisticated pitch

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control system with three high-speed proportional valves accounts for up to 23% of all downtime on wind turbines, more than any other component or subsystem. Pitch control valves independently change each blade’s angle facing the wind, sometimes as often as 10 or 20 times a second, based on incoming signals from a main controller on the wind turbine. These signals are a result of the wind conditions that the turbine is experiencing at a given time. Much like the rest of the turbine, the pitch control valve’s performance and lifetime are affected by the weather conditions around it.

Modern wind turbine energy systems were developed in an industrial scale in Europe, and pitch control subsystems were developed for those unique conditions. These valves need to be replaced three to five times over a wind

turbine’s lifetime in Europe, which equates to a five- to 10-year expected lifespan. When the same highly developed European technologies were introduced into the United States around 2007, pitch control valve life was noted to be remarkably shorter than was common in Europe. Valve failures were much more frequent in North America.

European manufacturers dominated in the United States until General Electric jumped into the fray with its own technologies, including a different way to address pitch control using electric — instead of hydraulic — devices. No matter which pitch control technology is used, America’s high winds keep pushing products into higher performance and longer life.

It became abundantly clear to wind project owners that normal American wind conditions were very destructive to pitch control valves. When analyzing wind conditions, tornadoes are at the apex, with 100- to 150-mph winds concentrated over small areas. Tornadoes are common in the United States but relatively uncommon elsewhere. Winds in these storm cells can gust at 90 mph over long periods of time and large distances, before reaching tornadic form and

WINDPOWER ENGINEERING & DEVELOPMENT // 2021 RENEWABLE ENERGY HANDBOOK

73

WINDPOWER

PITCH CONTROL VALVES

intensity. High, variable wind speeds create intense vibrations, especially in the blades that feather by design at 55 mph.

Feathered blades in 90-mph winds vibrate violently, resulting in acceleration forces as high as 20 G's. Valves in European wind farms seldom experience such extreme conditions that are so common throughout the United States. Extreme vibration destroys the delicate balance that exists in any normal proportional valves. The manifold and valves are not in a sealed environment; therefore, they sense the effects of hail, rain, sleet and snow. A few valve manufacturers have addressed these issues — one U.S. company doubled up with a pilot valve, adding power and structural strength. A major Asian manufacturer addressed the same problems by ruggedizing the exterior and strengthening the interior of the valve. Both valves have been successful in addressing the shortened valve life due to vibration.

The Asian manufacturer has successfully replaced nearly 4,000 failed valves installed in American wind farms, beginning in 2014.

The cost of pitch control valve failures is very high. Nearly one-quarter of all downtime in the industry is attributable

74

to this form of failure. It is expensive for a wind turbine to go off-line for days or weeks. Sending a crew up the nacelle is also expensive. The cost of the valve itself is nearly irrelevant in the overall downtime cost. If this one aspect of O&M represents nearly 25% of all downtime experienced by the industry, its reduction is the highest priority for most owners and O&M crews.

Maintenance costs have to be reduced.

Components of the turbine, such as the pitch control valve, need to be reliable and easily installed. “Plug and play” components will provide simple operation and user-friendliness. “Plug and play” for pitch control valves means the valve can be mechanically mounted and bolted down in the same location as the valve it replaces,

WINDPOWER ENGINEERING & DEVELOPMENT // 2021 RENEWABLE ENERGY HANDBOOK

as well as accepting the same electrical plug with the same pin pattern for power and input signals. The replacing valve must be equal in form, fit and function as the originally installed valve. In addition: Response Characteristics: A closedloop structure provided by incorporating a differential transformer for spool position detection enables feedback control, achieving high response equivalent to a simple servo valve.

High Accuracy: The valve has a hysteresis of 0.1% or less, achieving high accuracy equivalent to that of servo valves.

The normal 2% overlap type with linear no-load flow characteristics suitable for position and pressure control in machinery equipment.

Safety and Reliability: The valves support a fail-safe function to ensure safe operation in the event of electrical failure.

Electrical failures can include power failure, power cable disconnection, etc. Also, with a proportional valve of this magnitude, feedback of the valve’s performance can be monitored by the wind turbine owner or technicians. Steps have also been taken to reinforce the interior and exterior of the pitch control valve in order to provide an extended lifetime for the valve. By doing so, the valve can withstand severe wind conditions that U.S. wind turbine owners experience.

Overall, with the current short life span of wind turbines, replacement components within them must be constructed to combat the O&M costs placed upon owners. These components, such as the pitch control valve, must also be designed to withstand the harsh weather conditions that come with residing in the United States. The objective for the ruggedized pitch valve is to diminish failure rates, extend lifetime and reduce O&M costs of the wind turbines. Wind farm owners should look to invest in pitch control valves of this caliber in order to realize these benefits. WPE

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We make our

pitch control valves to last more than 5 years.

We warranty them for 3 years.

No one else does.

UNEXCELLED IN SPEED AND LIFE You can trust Yuken proportional valves, linear servo valves and servo-controlled systems.

Master Distributor: ALA INDUSTRIES LIMITED • Portage, IN • 877-419-8536 • www.yuken-usa.com Yuken 2020_REVISED_FINAL2 11-20.indd 1

11/19/20 11:52 AM

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2021 RENEWABLE ENERGY HANDBOOK

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1400 Shoals Way, Portland, TN 37148 Solar Power World 2019.pdf Solar Power World 2019.pdf

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