Solar Under Storm Part II is a response to the overwhelming reception of the original report, which provided best practices for ground-mount solar photovoltaic (PV) projects. It is also a response to stakeholder requests for a rooftop-focused report for the growing commercial and residential solar industry in the Caribbean and other vulnerable geographies with exposure to high-wind events.

High wind speeds increase risk factors for solar projects tremendously, but many solar installation companies inadvertently overlook or incorrectly apply low-wind speed designs (borrowed from Europe or the United States) for projects in high-wind zones like the Caribbean. These low-wind mistakes become catastrophic in high-wind events.

PREFACE

Solar PV failure reporting is needed because some failures are highly visible while others are not,
either because they are infrequent in occurrence or because they are privately dealt with and not publicly published. Showcasing a wide range of failures has multiple benefits:It provides proof to designers, installers, and customers that solar PV system resilience matters

Ramifications for product and project design, vendor selection, installation, and maintenance become real because they are tangibly connected to real- world failures

It helps solar professionals learn from past mistakes, which is critical as repeating mistakes damages the reputation and credibility of the solar industryLike the first version, this report provides an opportunity to address resilience for both a general and technical audience.

The report disseminates technical information to non-technical readers and creates a more informed solar professional, regulator, government official, utility, and customer. A well-informed customer base will systematically strengthen the PV industry by requiring vendors to incorporate resilience guidelines into their projects.

In an industry that has experienced drastic cost reductions year after year, in the “race-to-the- bottom” aspect of project and product design, it is critical for customers to understand best practices and not accept low-cost shortcuts that could jeopardize project life or energy production. Supplying the customer with a minimum set of guidelines raises the bar, and those guidelines can only be improved through innovation and definitive testing, which in turn creates a stronger industry.

The purpose of this document is to respond to the growing needs of the solar industry and combine field observations, photographic evidence, and expert analysis to provide actionable recommendations aimed at increasing the resilience of current and future rooftop PV systems. This report will touch upon flat- roof and pitched-roof PV power systems containing flat-mounted, tilt-mounted, fully ballasted, and hybrid ballasted/penetrating systems. It excludes canopy PV systems and ground-mounted systems (both fixed and tracking) as the recommendations for rooftop projects are specific to their application. Canopy and tracking systems may be addressed in future versions of the report if interest persists. Ground-mounted systems were addressed in the original Solar Under Storm report, which is still available from Rocky Mountain

1

This report is organized into five sections:

1. Introduction
2. Root cause identification methodology and findings
3. Failure mode and effects analysis (FMEA) 4. Technical discussion
5. Conclusion

The intended audience for Sections 2, 3, 4, and the Appendix is engineering professionals responsible for PV system design, PV system specifications, and/ or PV system construction oversight and approval. Sections 1 and 5 are intended for a more general audience of customers, governments, utilities, regulators, developers, and PV system installers who are interested in improving PV system survivability to intense wind-loading events.

Solar Under Storm Part II was developed with direct feedback from solar companies in the Caribbean that learned lessons in solar project resilience firsthand during and after Hurricanes Irma, Maria, and Dorian. Continuous feedback from the solar installer community is vital to the success for solar PV resilience. Thus, RMI and the Clinton Foundation’s Clinton Climate Initiative will host workshops and other opportunity for on-going communication on this topic—notably through the forum of the Clinton Global Initiative (CGI) Action Network on Post-Disaster Recovery.