Webinar Lead
Array Technologies

How Technology is Protecting Solar Farms Against Extreme Weather

In October 2023, John Sedgwick, president of VDE Americas, joined Brown & Brown’s Michael Perron and Array Technologies’ Brandon Taylor to discuss lessons learned about and best practices for protecting utility-scale solar assets and portfolios from severe convective storm risks. Here, we summarize the Top 10 takeaways from this webinar.

John Sedgwick
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Michael Perron

| Brown & Brown

#1. Hail claims account for a majority of insured solar losses.

In his introduction, Michael Perron—senior managing director of Brown & Brown’s global energy and climate tech risk solutions—notes that hail has become an essential issue for insurance industry stakeholders in recent years. One insurer estimates that hail claims represent 55% of all insured losses to solar PV assets. While module glass thickness is important for hail risk mitigation, using single-axis trackers to move modules away from direct hail impacts is perhaps even more critical.    

#2. Defensive stow failures correlate to significant loss events.

Though limited, the available data suggest that stowing single-axis tracker–mounted PV modules at a high-tilt angle significantly reduces PV module damage. The largest solar loss events have all occurred at projects that either did not stow defensively in advance of a hailstorm or failed to stow completely. Stowing modules horizontally during construction elevates hail risk. Hail risk mitigation is compromised when defensive wind-stow protocols take priority over hail-stow optimization. Risk mitigation fails if weather alerts are not received and acted upon promptly.

Taylor headshot

Brandon Taylor

| Array Technologies

#3. Face modules out of the wind at maximum tilt for hail resilience.

Array Technologies optimized its tracker’s defensive hail stow capabilities based on the results of VDE Americas’ hail risk advisory services. These third-party studies compared hail risk across various tilt-angles, facing both into and out of the wind. Based on these comparative risk assessments, Array Technologies realized that stowing modules at a maximum tilt angle facing away from the wind reduces the effective kinetic energy and damage potential of hail impacts. Informed by this catastrophic risk assessment report, Array Technologies was able to develop and implement a defensive stow protocol optimized for hail risk mitigation.

#4. Effective structural design accounts for both hail and wind.

Severe convective storm risk is not binary, as severe hail and high wind are coincident risks. According to NOAA, a severe thunderstorm produces hail greater than or equal to 1 inch (25 millimeters) in diameter and/or wind speeds greater than or equal to 58 miles per hour (25 meters per second). For effective risk mitigation, users must address the risks associated with both hail and wind. Since Array Technologies'  linked-row trackers are capable of withstanding the full wind speed at a site, regardless of wind direction, project stakeholders do not need to choose between hail or wind stow during a severe storm.

#5. Automate tracker defensive hail stow to reduce project risk.

Since severe convective storm alerts may provide plant operators with little advanced warning, remote operation center protocols that rely on manual intervention could lead to a failure to stow in advance of a hail event. Array Technologies has developed automated hail response capabilities to address this vulnerability. DTN’s weather service data informs the automatic hail response, eliminating the need for manual intervention. This feature establishes a virtual geofence around the property. The controller will move all tracker rows to a maximum tilt angle if a severe convective storm crosses this perimeter.

#6. Be aware of severe weather risks during construction.

Depending on the size of the project, construction on a large utility solar project could range from six months to two years. If the support structure can withstand full site-design windspeeds at any tilt angle, have installers position each tracker row at a maximum tilt angle as soon as they install the glass. This defensive stow posture will mitigate against hail and wind damage before energization. VDE Americas’ catastrophic risk reports can characterize probabilistic storm approach distributions and optimal pre-energization tilt direction for any project site.

JTS headshot

John Sedgwick

| VDE Americas

#7. Solar market and technology trends are increasing hail risk.

Utility-scale solar installations have increased dramatically in some of the most-hail-exposed areas on the planet. Whereas hail risk was relatively benign in early solar markets, such as California and Germany, today’s leading solar markets include hail-exposed regions, such as West Texas. Also, a warming climate may contribute to a general increase in storm severity and frequency. At the same time, manufacturers’ value-engineering efforts have made modules less resilient to hail. Technology trends that increase vulnerability to hail and wind damage include larger aperture areas and thinner glass, wafers, and frames.

#8. PV module qualification tests do not characterize hail resilience.

Core PV module safety and performance standards in IEC 61215 are pass/fail in nature and do not differentiate product designs based on long-term in-field durability. The modest kinetic energies required for product certification are inadequate for characterizing resilience to severe hail. Working with RETC (Renewable Energy Text Center) and other industry stakeholders, VDE Americas is developing statistically significant hail test standards. Differential hail risk data—such as edge-of-module versus center-of-module resiliency—are a key factor for determining the financial risks associated with hail.

#9. Financial risk due to hail is a function of solar project characteristics. 

VDE Americas hail risk advisory products characterize financial risk based on site-specific meteorological data and product-specific technical details. These products include probable maximum loss (PML) and Poisson risk exposure (PRE) reports. Project stakeholders can use the pro forma and downside risk estimates in a PML report to rationalize insurance premiums, terms, and conditions. Meanwhile, the PRE report characterizes risk exposure outside of insurance over a user-specified financial hold period. Beneficiaries of these innovative hail risk advisory services include project developers, owners, tax equity investors, lenders, insurers, asset operators, tracker manufacturers, and module companies.

#10. Adhere to the mantra, “Stow early and stow often.”

Solar irradiance is minimal during severe storm events. Performance modeling indicates that proactive stowing during potential hail events has very little impact on annual plant production. When a severe convective storm approaches a fielded solar project, the single most important thing stakeholders can do to minimize risk is get the project to the optimal defensive stow position as early as possible.

Hail Stow

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