Solar Under Storm Part II

This report provides engineering and design best practices to improve the resilience of rooftop solar PV systems against hurricane-force winds, primarily in the Caribbean. Based on an analysis of failures from 2017-2019, it identifies top-down clip failure and joint loosening as primary root causes of system collapse. Key recommendations include using vibration-resistant fasteners, avoiding ballasted-only systems in favor of mechanical attachments, and ensuring modules are not installed over roof edges or in high-pressure 'Zone 3' areas. Implementing these measures is estimated to increase EPC costs by roughly 5%.

• The most frequent failure mode for rooftop PV systems in high-wind events is the failure of top-down clips, which was observed in 96% of applicable projects (21 out of 22). This often leads to a cascading failure where the loss of one module allows the liberation of adjacent modules, subsequently causing debris and impact damage to the rest of the system.
• To prevent cascading failures, the report recommends using top-down clips that hold modules individually or independently, or alternatively, through-bolting the modules. It specifically advises against the use of shared middle clips.
• Joint loosening due to transverse vibration is a significant contributor to connection failure. The report recommends using vibration-resistant fasteners (such as nylock, loctite, or double-nuts) and avoiding self-tapping screws for structural connections.
• Ballasted-only systems are not recommended for high-wind zones due to the risk of cascading failure and 'walking' (lateral displacement). All systems should have positive mechanical attachments to the building structure, including at the corner module of every array.
• PV modules should be installed within the envelope of the roof structure and avoided in 'Zone 3' (high pressure regions), as the wind pressure in this zone is approximately 50% higher than in Zone 2. Modules overhanging roof edges are almost universally lost during hurricanes.
• Implementing these resilience best practices is estimated to increase engineering, procurement, and construction (EPC) costs by approximately 5% compared to standard Category 3 or 4 rated installations. For a 263 kW system in Puerto Rico, achieving a 175 mph rating instead of 145 mph increased costs by 5.5%.

APA

BURGESS, C., DETWEILER, S., NEEDHAM, C., & OUDHEUSDEN, F. (2020). Solar Under Storm Part II. RMI. https://rmi.org/app/uploads/2026/05/Solar_Under_Storm_Part_Two.pdf

Chicago

BURGESS, CHRISTOPHER, SANYA DETWEILER, CHRIS NEEDHAM, and FRANK OUDHEUSDEN. Solar Under Storm Part II. RMI, 2020. https://rmi.org/app/uploads/2026/05/Solar_Under_Storm_Part_Two.pdf.

Wikipedia

{{cite report |last1=BURGESS |first1=CHRISTOPHER |last2=DETWEILER |first2=SANYA |last3=NEEDHAM |first3=CHRIS |last4=OUDHEUSDEN |first4=FRANK |title=Solar Under Storm Part II |publisher=RMI |date=February 2020 |url=https://rmi.org/app/uploads/2026/05/Solar_Under_Storm_Part_Two.pdf |access-date=17 August 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{burgess2020solar, author = {BURGESS, CHRISTOPHER and DETWEILER, SANYA and NEEDHAM, CHRIS and OUDHEUSDEN, FRANK}, title = {{Solar Under Storm Part II}}, institution = {RMI}, year = {2020}, month = feb, url = {https://rmi.org/app/uploads/2026/05/Solar_Under_Storm_Part_Two.pdf}, urldate = {2026-08-17}, note = {Indexed by Climate Insights Directory} }