Among Scott Stephens’ many job responsibilities is seeing the future. As head of technology at Clearway Energy Group, a developer and operator of solar, wind and energy storage projects across the United States, Stephens is charged with clearly understanding the technologies and equipment that will eventually become mainstream in the company’s projects.

“My responsibilities are primarily on the procurement and technology side,” said Stephens. “What do we think those projects are going to look like a year, two or three years from now as new technologies come to the industry? And what is the best procurement strategy to achieve the most value from new technologies and design?”

As Stephens considers the future of Clearway’s utility-scale and community solar projects, it’s clear that large format modules with power ratings above 500 watts will be increasingly important. The reason propelling the influx of large modules is one that is familiar to anybody who has watched the mainstreaming of solar energy over the past decade: it’s all about improved economics. In fact, when Stephens examines large format modules, he sees them offering four cost reduction opportunities.

The first is that large modules offer panel manufacturers a straightforward way to reduce their own costs on a per watt basis. “Even though they need more glass, for example, it’s still cheaper to buy, on a per area basis, a larger sheet of glass than a smaller one,” said Stephens. The second area of cost reduction Stephens sees comes from the potential that trackers can be built in a more cost-effective way to mount larger modules.

Stephens sees a third cost reduction opportunity coming from labor savings: it simply takes less time to install the total capacity of a solar power plant when each module has a larger power rating. The fourth cost savings opportunity relates to wiring. “The DC electrical savings that you can have by having more watts per string because you have more watts per panel,” said Stephens. “Those are the four but it’s also worth mentioning that there are potential energy performance benefits that include improving bifacial performance with larger format modules.”

As these potential benefits become clear, solar developers worldwide are increasingly pondering how to maximize the benefits of large modules because manufacturers are rapidly ramping up their production and unveiling new products.

Industry analyst PV Infolink now estimates that by the end of 2021, nearly 200GW of large-format cell manufacturing capacity will be online. This includes both 182mm and 210mm wafer sizes. Within these two cell formats, multiple module form factor products have been announced from all leading PV module manufacturers over the past 2 quarters. The range of available module products on the roadmap for utility-scale developers has never been greater.

But for solar developers, EPCs, project owners and investors, what is far more critical than the trend towards large modules itself is the potential these new products have of improving solar’s levelized cost of energy (LCOE).

“Growing the size of the module incrementally means you can reduce the number of panels you need per megawatt and reduce the number of electrical strings per megawatt. All of this is happening as the cell efficiency is going up a little bit as well,” said Greg Beardsworth, director of product management at Fremont, California-based Nextracker, Inc., the world’s largest solar tracker and software company. “It’s apparent that this is going to improve the economics of solar. But for downstream companies, the systems need to be ready for these larger modules for any benefits to be realized.”

Retooling design and engineering analysis

Being prepared to incorporate the many potential benefits of large solar modules is not a bad challenge to face. But the implications of using larger and more powerful modules are not inconsequential.

For example, effectively pairing large modules with trackers means understanding the structural and mechanical design considerations that come with using heavier panels with more surface area. “The most important structural and mechanical design consideration for a tracker is wind,” said Beardsworth. “The array of panels acts like a large sail, and we’ve now grown the size of that sail. Obviously, there’s going to be more load going through the structure and you’re putting up more surface area that’s catching more wind. You’ve got to deal with that somehow as a system.”

In other words, while large modules installed on trackers have tremendous potential to improve the economics of solar projects, the industry needs to be clear-eyed about the due diligence and research needed to safely and effectively secure those benefits. Specifically, solar project developers and owners must understand how to use design, engineering and procurement to best mitigate the impacts of severe weather, particularly high winds and hail.

There is plenty of evidence that severe weather can imperil solar projects, even before large modules are widely available in the U.S. Data published by the renewable energy insurance specialist GCube found that severe weather is responsible for most solar insurance claims. The insurance loss adjusting company Lloyd Warwick International also reports that weather-related damages account for more than 80% of solar claims value.

All of this emphasizes the importance of working with tracker companies that have sufficiently retooled their wind and weather analysis to account for the unique characteristics and design challenges of large modules. “As you grow the module, the surface area goes up, the wind loads go up and the weight goes up. It elevates the importance of all this dynamic analysis and stability analysis,” said Beardsworth. “As you put more weight on the rows and create a bigger form factor, the risk of getting the dynamic analysis wrong is greater. If a company is marginal at wind engineering with legacy size modules and hasn’t retooled for larger modules, that can introduce a lot of risk.”

Preparing for a wave of large modules

About nine months ago, Nextracker made significant investments in its design and engineering analysis capabilities to help customers prepare for the coming wave of large modules. “We now have the entire design space fully covered in our wind engineering so that it includes both static and dynamic analysis,” said Beardsworth. “Historically, it’s the dynamic events that have killed poorly designed trackers, including when galloping events happen at low wind speeds. Our expanded analysis includes these larger form factors from both a static and dynamic perspective.”

As part of its expanded analysis capabilities, Nextracker has acknowledged the reality that there likely won’t be a single large module form factor that will dominate the market. Instead, the company seeks to provide objective analysis about the range of large modules available and how they can be incorporated into projects most effectively. “We see an opportunity to really help our customers work through the process of figuring out the right options by evaluating all of these panels,” said Beardsworth. “We want to give them confidence that no matter which one they pick, they will get a vetted, well-engineered, low-risk and high-performing asset.”

This type of rigorous analysis is important to McCarthy Building Companies, which provides design-build EPC services to a wide variety of market sectors, including renewable energy and energy storage. In designing and building about 4.5 gigawatts of mostly utility-scale solar projects, McCarthy understandably has a thorough process for evaluating new products, like large modules, as well as how they can be best integrated into the design of a project.  

Large modules will be incorporated into many of McCarthy’s projects in late 2021. This is happening because McCarthy has gained confidence that large modules paired with trackers will deliver long-term value to the owners of the solar projects it builds – confidence that comes from its own analysis as well as design and engineering guidance from Nextracker. “Structural design is so important and we have to understand how these larger form factors impact the tracker system,” said Dhruv Patel, senior vice president, EPC at McCarthy. “The Nextracker team has amazing in-house structural engineering capabilities that leads their tracker design and gives us confidence in the value our projects can provide to customers.”

Patel says a number of projects with large modules and trackers are planned for the U.S. Midwest, where the firm constructs utility-scale solar plants and has experience with the area’s undulating terrain and severe weather which are key factors shaping project design. Large modules and trackers can make the economics of projects in relatively new markets work in a way that has never been possible before. Working with Nextracker on these projects gives Patel design flexibility and confidence that the trackers will perform well in the unique weather conditions in the region.

“Midwest projects have several things to worry about, from wind speed and snow to hailstorms. Nextracker has stow features and flood sensors and software that can improve the production at these sites,” said Patel. “Not only does their system offer flexibility from a layout perspective and controls to handle severe weather, they also have an innovation mindset that is important. We are in an industry where new innovation happens every 12 to 18 months and you must have partners committed to continuous innovation.”