Solar for wind disasters
Last updated 5/10/2019
Weather events like hurricanes are accompanied by wind speeds up to 200 miles per hour, and tornadoes can bring even higher speeds that threaten to damage rooftop and ground-mounted solar energy systems. It is important to know how solar energy systems hold up, and if they can be a reliable resiliency tool in the event of extreme wind events that may knock out parts of the electric grid.
Solar panels hold up well in high winds
Generally, solar panels are highly resistant to damage from windy conditions. In fact, most in the EnergySage panel database are rated to withstand significant pressure specifically from wind (and hail!). The limiting factor for solar panel wind resistance is almost never the panels themselves. In most instances where wind causes damage to a solar array, failures occur due to weaknesses in the racking system or in the roof that your panels are mounted to.
When wind blows across a roof with solar panels, it passes through the small space that typically exists between the panels and the roof (or between your panels and the ground in the case of ground-mounted systems), causing a large amount of uplift to the panels. This phenomenon is capable of tearing panels from their mounts, or the mounts from the roof or ground. In the most extreme cases, solar panels may stay anchored down, but uplift from strong winds can tear sections of your roof off. Cases like these show that a well-built solar racking system may be more resistant to high winds than your roof itself.
Another source of panel damage in wind storms can be flying debris. Although more unpredictable than wind alone, due to the variety of sizes and types of materials that can be blown around in a storm, solar panels have proven to be remarkably resistant to impact from wind-blown debri in the past. At the National Renewable Energy Laboratory (NREL) campus in Golden, Colorado, a severe hailstorm resulted in one broken panel out of 3,000 in a large rooftop array. While not a perfect predictor of solar panels’ ability to withstand any debris, this case is an encouraging reminder that solar panels are hardy devices capable of surviving varying weather events.
Building codes promote wind resistant solar arrays
If you live in an area with frequent hurricanes (like Florida) or tornadoes (like Texas or Oklahoma), your local government may have policies that mandate a level of durability for rooftop solar arrays. For example, in some areas of southern Florida where hurricane season predictably brings extreme winds every year, solar panels must be installed to withstand winds up to 170 miles per hour. This requires solar installers to test their panels and racking equipment to ensure that they will remain anchored to your roof in hurricane-level winds.
Most solar installers follow engineering guidelines set by the American Society of Civil Engineers (ASCE) in their Minimum Design Loads standards book. While ASCE doesn’t mandate a certain level of wind resistance, they outline a standard procedure for testing solar panels for a wind resistance rating. This ensures that solar panel installations nationwide are compared to a common standard, and is a good way to verify that your solar installer is putting their equipment through appropriate and accepted testing methods. Municipalities will often include ASCE 7-10, the wind-specific ASCE standard, as a part of their local building codes to ensure local solar installers are abiding by national building standards and calculations.