Spotlight on Extreme Weather Risk Mitigation for Utility Solar Plants

The images of solar power plants damaged by extreme weather are sobering. Rows of PV modules, their front glass shattered by hail. Trackers twisted and tossed like toys by high winds. Large-scale solar farms inundated with floodwaters caused by torrential downpours.

Although the risk of damage caused by extreme weather to most utility solar plants is relatively low, the financial and performance impacts when it does occur can be high, even catastrophic, to the tune of tens of millions of dollars and extended periods of lost production. Weather-related damages to solar facilities account for 80% of insurance claims values, according to insurance loss-adjustment specialists Lloyd Warwick International. With the industry scaling toward hundreds of gigawatts of installed capacity, even 1% risk represents the potential for significant losses.

As the deployment of large-scale solar accelerates into areas more prone to severe weather events, the focus on how to manage those weather risks has grown sharper. Thankfully, there are ways to mitigate extreme weather risks by addressing site- and region-specific conditions in advance and making strategic design, engineering, and procurement choices to lower those risks.

Nextracker has been one of the leaders in addressing the extreme weather challenge to large-scale solar plants. For example, we have:

  • Doubled down on making our trackers even more resilient, durable, and smarter.
  • Worked with independent testing labs to understand the effects of high winds, flooding, snow, and hail impacts on our systems
  • Helped plant owners optimize their plants and get ahead of severe weather events.
  • Partnered with insurance companies to help improve risk management maturity in the industry.

In addition, our NX Navigator software offers plant owners and operators another layer of monitoring and control capability, increasing production yield, and enabling reliable operation across a wide range of severe weather conditions.

Over the past few weeks, we have been busy spreading the gospel of heavy weather risk mitigation for utility solar plants. We published a well-received technical white paper titled “Mitigating Extreme Weather Risk Part 1: Understanding How Differentiated Design and Control Strategies Unlock New Opportunities for Solar Development” (downloadable here). We have also participated in several online events, including the GTM webinar “Strategies in Climate Risk Mitigation: Keeping the Power on with Advanced Solar Software” and the extreme weather panel held as part of pv magazine’s virtual Quality Roundtable USA.

There’s too much to unpack here, so let me share a few key takeaways.

1. Hail Risk Is Increasing

Large-diameter hail is increasing over time due to climate change, and more large-scale solar projects are being built in hail-prone areas like Texas. At the same time, PV modules are getting bigger while the thickness and strength of module front glass on some of these supersized modules are decreasing, making them more vulnerable to hail strikes. Because of this and other extreme weather events, insurance companies are reacting and charging higher premiums for equipment that is not designed with hail damage mitigation in mind.

2. Resilient Design and Smart Controls Lower the Risk

Nextracker is working with our module partners to provide additional mechanical durability for these larger modules being integrated with our trackers. In addition, a connected power plant can use NX Navigator’s advanced weather forecasting and smart hail-stow capability, which quickly moves trackers into a safe 60-degree stow angle in advance of the hailstorm and triples the hail resistance of PV modules compared to stowing horizontally. Rotating away from the incident angle is crucial, as this prevents initial cracking in the module glass and the subsequent propagation of visible cracking and microcracking that may decrease module production over time.

To understand why having active controls is so vital to a long-lasting large-scale solar system, one must first understand how large hail is caused. Thunderstorms cause hail when warm air is pulled through an updraft and creates hail through the large downdraft, sending the hailstones hurtling toward the ground. Temperature is one of the biggest factors that produce large hail, with elevation and seasonal occurrences also playing their parts. It’s no coincidence that “hail alley” in the Midwestern U.S. (shown in the figure below) is where elevation begins to dramatically increase in the middle of the continent. (The same conditions occur in Australia, where social media-worthy, grapefruit-size hail occurs in the Queensland highlands.) Seasonal effects also play a role, where colder spring thunderstorms produce the largest hailstones.  A review of the known hail-affected solar projects in the U.S. reveals the common denominator is damage from April to June, which could well be called hail season.

3. Hail and High Wind Are Not Always A Package Deal

The final piece of hail-prone damage relates to wind speed, a relationship misunderstood by many in the solar community. Since hail occurs during thunderstorms, hail and wind occurrence will likely coincide but not necessarily at the ground level. PV arrays at ground level may experience hail but not necessarily wind speed that correlates to common tracker stow-speed thresholds. Beyond this, wind is dynamic, where in reality a wind event is a series of gusts dispersed throughout a large area. With the size of projects today different wind speeds are recorded throughout the site giving variable loads on modules and tracker alike. As demonstrated in the graphic below, solar trackers inherently change the course of wind speeds through a project site as well, where rows on the outer edges will shelter those on the inner portions of the array.

But wind speed is not the full story. What is rarely discussed is the fall rate; according to U.S. National Oceanic and Atmospheric Administration data, large-size hail (2-4 in.) has double the fall rate of small-size hail (1-2 in.). This creates a very vulnerable situation for solar trackers, where the most damaging hail could be coming down around solar noon. Since the PV panels would be aligned in a horizontal position and fully exposed to the hail impacts, significant damage to the systems could result without smart tracking solutions responding in real-time and stowing the panels out of harm’s way. Understanding the risks from the combination of hail and wind as well as the need for trackers integrated with intelligent monitoring and control to mitigate those risks will be critical for owners and insurers, so they can separate robust, data-driven solutions from marketing-based, technically flawed solutions among the tracker competitors.

4. Insurance Companies Are Learning How to Manage the Risk

Michael Kolodner of Marsh, leader of the insurance firm’s U.S. renewable energy practice, provided a cogent explanation of the challenges facing underwriters during the GTM webinar. He put catastrophic risk (low frequency, high severity) in context, calling it the most difficult component in the underwriting process to get right, given there’s not much data on which to build estimates. But he noted that even locations with natural hazard risks have a potential upside if the benefits of a mature risk management approach can be quantified.

Those that demonstrate greater risk management maturity have historically had:

  • Greater access to risk capital
  • Greater flexibility in negotiating terms and conditions
  • The ability to turn risk into opportunity

Kolodner already sees a flight to quality in this regard, with risk aggregators increasingly leveraging scale and sophistication to generate outsized value. Working with smart materials and systems providers like Nextracker really does matter, bringing confidence to underwriters looking to help de-risk projects in regions prone to extreme weather.

How much risk are plant owners willing to take when it comes to extreme weather mitigation for the long haul? The good news is these weather events do not have to be catastrophic to utility solar power plants. Nextracker and others in the industry have made good progress over the past year in researching the issues, developing tools, and finding solutions. These continuing collaborative efforts will go a long way toward educating stakeholders and mitigating the increasing short- and long-term risks to large-scale solar assets caused by the changing climate.

To download the Nextracker white paper, “Mitigating Extreme Weather Risk Part 1: Understanding How Differentiated Design and Control Strategies Unlock New Opportunities for Solar Development”, click here.

Alex Roedel is the Senior Director of Design and Engineering at Nextracker. He leads a global team of design engineers and is the company’s customer-facing technical lead with developers and EPCs worldwide.