Side Benefits from Solar Panels: Rooftop Cooling, Warming

According to a team of researchers at UC San Diego Jacobs School of Engineering, rooftop solar panels can do more than just generate electricity or heat; they can help cool your roof in the summer and warm it during the winter, resulting in additional energy savings. In a study in an upcoming issue of Solar Energy, researchers, led by Jan Kleissl, provide details of a study that shows that solar panels act as shade during warmer months and as a form of insulator during the winter. The savings are not huge--just 5 percent--but they strengthen the case for solar panels on the roofs of commercial buildings such as hotels. Researchers found that the roof itself stays cooler in the summer as well as the ceilings of the rooms just below the roof.

Data for the study was gathered over three days in April on the roof of the Powell Structural Systems Laboratory at the Jacobs School of Engineering with a thermal infrared camera. The building is equipped with tilted solar panels and solar panels that are flush with the roof. Some portions of the roof are not covered by panels. The idea for the study came about when Kleissl, Dominguez and a group of undergraduate students were preparing for an upcoming conference. They decided the undergraduates should take pictures of Powell’s roof with a thermal infrared camera. The data confirmed the team’s suspicion that the solar panels were indeed cooling the roof, and the building’s ceiling as well.

In an article on the UC San Diego Jacobs School of Engineering website, Kleissl said, “There are more efficient ways to passively cool buildings, such as reflective roof membranes. But, if you are considering installing solar photovoltaic, depending on your roof thermal properties, you can expect a large reduction in the amount of energy you use to cool your residence or business.”