Wind loads on roof-mounted solar panels

If it seems like solar modules are popping up everywhere, you’re right. In 2006, a new solar energy system was installed, on average, every 80 minutes in the US, and by 2013, installers were building a new system every four minutes. And the installations haven’t slowed down. In 2016, the US reached 1 million installations, which took over 40 years. Currently at 1.7 million installations, the U.S. is projected to reach 2 million by the end of 2018, a mere two years after reaching the 1 million milestone.

But you don’t need statistics to recognize the growth of solar. If you’ve recently occupied the window seat of a commercial flight during takeoff or landing, you’ve no doubt seen for yourself the increased deployment of solar technology in the city below.

An enabling development in the success of solar has been better awareness of and appreciation for the role of wind in array design. Techniques pioneered right here at CPP have empowered more and more solar developers to design novel mounting systems that can withstand all that mother nature throws at them.

The roof of a building isn’t very accommodating to solar modules. Because they’re tilted toward the horizon, solar panels are, aerodynamically speaking, just small wings. The further north you are, the greater the tilt. You feel the effect of tilt when you stick your hand out the window while riding in a car. Leave your hand horizontal and you feel almost nothing. But tilt your hand into the wind, and a powerful force tries to push it away from the ground.

But it’s not just the wing effect that makes roofs particularly dangerous. A building itself induces airflow changes that conspire to make conditions worse than if the building weren’t there in the first place. Flow features called vortices, which are like little tornados, form at the corners of buildings and generate more uplifting power than the straight line wind itself.

When laying out a solar array on a flat roof, engineers need to account for overall building size and shape, the local wind climate, and the design of the modules and racking system. All of these factors play a role in whether the array will weather the storm, suffer damage, or even catastrophically fail.

If you work in the solar industry, you understand that deadlines, permitting, and razor-thin margins leave little room for uncertainty in product design. Contact CPP today, and let our experienced wind engineers save you time, money, and headaches on your next project.

Originally published: April 6, 2014