With Tropical Storm Erin showing the potential to become the first major Atlantic hurricane of 2025, solar owners on the East Coast are likely keeping resilience front of mind. A recent report from the nonprofit Rocky Mountain Institute (RMI) provides updates to best practices for designing and installing solar PV systems in hurricane-prone regions.
The report, Solar Under Storm III, builds on the findings of Solar Under Storm (2018) and Solar Under Storm II (2020), which identified “key design and construction choices” that enabled some solar systems to survive Category 5 hurricanes like Irma and Maria, while others failed. This latest edition incorporates lessons from Hurricane Beryl in 2024— the earliest Category 5 hurricane ever recorded in the Atlantic.
The new report follows field investigations of three ground-mounted systems directly hit by Beryl, and updates technical recommendations based on real-world damage assessments. RMI emphasized “proven practices” such as dual-post piers, through-bolting, lateral racking support, and vibration-resistant connections, as well as identifying common failure points such as inadequate load design, low-cycle fatigue of module frames, and the use of top-down clamps and self-tapping screws.
In addition to engineering specifications, the report also stresses the importance of industry collaboration to strengthen resilience standards. It encourages shared testing protocols, material certification, and ongoing information exchange — supported by the PV Resiliency Working Group on the online Caribbean Renewable Energy Community (CAREC).
What works best?
In the report, RMI broke down common attributes in systems that failed and in systems that survived hurricanes.
Similarities of failed systems in the wake of Hurricanes Irma and Maria and “further validated” by investigations in the Grenadines after Hurricane Beryl include:
- Top down or T clamp failure of modules
- Undersized rack or rack not designed for wind load
- Lack of lateral racking support (rack not properly designed for wind loading from the side)
- Undersized bolts
- Under-torqued bolts
- Lack of vibration-resistant connections
- PV module design pressure too low for environment
- PV module frame experience low-cycle fatigue failure
- Use of self-tapping screws instead of through bolting
On the other hand, some common ground-mount PV attributes of surviving systems include:
- Dual post piers
- Through bolting of solar modules (no top down or T clamps
- Lateral racking supports
- Structural calculations on record
- Owner’s engineer of record with QA/QC program
- Vibration-resistant module bolted connections such as Nylocs
RMI’s report also provided an updated list of recommendations for building more resilient solar PV power plants, including avoiding self-tapping screws; specifying the bolt QA/QC process; specifying high-load PV modules based on structural calculations; and requiring structural engineering in accordance with ASCE 7 and site conditions, with engineer sealed calculations for wind forces, reactions, and attachment design.
Download the full report here.
