Reevaluating hailstorm damage at the Fighting Jays solar project

In mid-March 2024, a series of very severe spring hailstorms careened across Fort Bend County, Texas, directly southwest of Houston. Because of its proximity the country’s largest municipal user of renewable energy, Fort Bend County is home to more than 1.2 GW of large utility-scale solar project capacity. Houston residents—and solar industry stakeholders everywhere—took notice when catastrophic hail losses the Fighting Jays solar project made headlines.

Though the if-it-bleeds-it-leads tendency in journalism is nothing new, the most interesting story coming out of Fort Bend County is not that 1-in-500-year hail events in Texas can wreak havoc on the built environment. Rather, it is the news that hail stow protocols successfully prevented widespread physical damage at several utility-scale solar farms near Fighting Jays that were also exposed to very severe hail.

Our forensic investigations show that operational hail stow protocols are effective for weathering 1-in-500-year severe convective storm events—even in Texas. Unfortunately, these success stories are not getting the attention they deserve.

Fort Bend County case study

As the president of a technical advisory firm that specializes in hail risk assessment, mitigation, and consulting services, I wanted to learn as much as possible about the estimated multi-million-dollar Fighting Jays solar project hail loss event. What we learned from our meteorological and forensic analyses—with the help of others in the technical due diligence and project stakeholder communities—exceeded our expectations. Here are brief summaries of some of our key findings.

Three severe hail producing storm events occurred within a 12-hour period. To better understand event meteorology, our team reviewed NOAA’s next-generation weather radar (NEXRAD) data. Specifically, we analyzed the maximum expected size of hail (MESH) in the Fort Bend County area around the time of the hail loss event. Based on this analysis, we know that two major hailstorms occurred after noon on Friday, March 15, 2024. Additionally, a rare overnight hailstorm struck the area in the early morning hours of Saturday, March 16, 2024.

All three of these hailstorms met >500-year event severity criteria. To understand event severity, we compared event-specific maximum hail size estimates to location-specific hail return intervals. The return interval metric characterizes the estimated amount of time between discrete events, such as the number of years between baseball-sized hail at a specific location. Comparing NEXRAD hail size estimates to naturally occurring hail return data in ArcGIS Online, we observed that the MESH values for all three of these severe storm events exceeded 500-year fixed hail return intervals for Fort Bend County. Our meteorological models predict that the 500-year fixed hail return interval for the Fort Bend County area is ≥65-mm (≈2.5-in) hail. Based on this hailstone diameter threshold, all three of these severe convective storms were 1-in-500-year events.

Lessons from null loss events

At the 2024 PV Module Reliability Workshop, an annual event hosted by the National Renewable Energy Laboratory (NREL), our hail team leader, Jon Previtali, presented a poster introducing a public hail forensics database for PV power plants to be located on the DuraMat Data Hub. As part of this effort, VDE Americas is working in collaboration with NREL, SEIA, FM Global, CAC Specialty and others on a null hail event study, which is a study of zero-loss hail events at utility solar farms.

Why so much ado about nothing? Because null loss events are in many ways the missing link in our evolving understanding of solar project hail resilience.

Though we have strong evidence, shown here in Figure 2, that the number of utility solar farms exposed to very large hail is considerably larger than the number of hail-related insurance claims, a database of confirmed null loss events is challenging to compile. After all, no one ever calls a forensic investigator when things go to plan. The Fort Bend County case study is consequential because it definitively validates the efficacy of solar project hail stow protocols.

With the support of Array Technologies, VDE Americas was able to study pre-event hail stow protocols and post-event damage reports for three utility solar farms located within 15 km (≈9.3 mi) of the hail-damaged Fort Bend County solar farm. All three of the projects studied—specifically, Cutlass I, Cutlass II, and Old 300—were exposed to >500-year hail events. Two of the projects sustained no direct hail-related damages. At the third site, a few dozen modules sustained damaged due to hail and wind-blown objects. Importantly, hail-related damages at this 270-MWp PV project site were limited to an area where a tracker motor issue prevented complete hail stow.

These results provide conclusive evidence that operationalized stow protocols are effective at preventing solar module glass breakage during a severe hail event. On the one hand, we found that PV modules in a hail-stow position sustained no direct hail-related damaged form a 1-in-500-year hailstorm. On the other hand, we found a relatively modest amount of hail damage at a portion of the plant that we know did not achieve complete hail stow. This clearly indicates that overall site damages could have been much worse if not for successful solar project hail stow protocols.

These real-world results validate outcomes that our team’s work has long predicted. Our deterministic meteorological and financial hail loss models consistently indicate that common sense hail defenses can prevent or mitigate hail-related damaged. The Fort Bend case study is proof positive that even though severe hail risk is inevitable in some locations, large project losses are not.

—This article originally appeared in at PV-Tech.org, the number one source for in-depth and up-to-the-minute news, technical articles, blogs and reviews on the international solar PV supply chain.