Everyone knows what solar panels do – they convert sunlight into electricity to power homes and businesses via photovoltaics. But a recent study from the University of California San Diego Jacobs School of Engineering says solar panels are up to something else as well: By acting as a layer of insulation, they’re actually helping to keep buildings cool in the summer and warm in the winter.
The study, headed by environmental engineering professor Jan Kleissl, details the cooling capabilities of solar panels. Using thermal imaging, Kleissl’s team determined that a rooftop under solar panels is about 5 degrees Fahrenheit cooler than a rooftop exposed to the sky. Kleissl’s team also noted that at night, when temperatures drop, the panels kept heat inside the building. This means that solar panels can cut down on heating cost in the winter even if solar energy is not being used for heat.
For cooling, tilted panels were found to be more efficient than those flush with with the roof, as they allow wind to pass between the panel and the rooftop, removing excess heat. The team also found that the more efficient the solar panels, the more heat was reduced. In the building they studied, Powell Structural Systems Laboratory at UC San Diego, rooftop solar panels reduced the heat by 38 percent.
The idea for the study came about when Kleissl and some undergraduate students were preparing for a conference. The students took pictures of the Powell lab’s roof with infrared cameras and found that the areas covered by solar panels were markedly cooler than those without. “Talk about positive side-effects,” said Kleissl.
Using solar panels to passively cool buildings is not the most efficient method, Kleissl said, 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.” With more testing, the team could conceivably develop a way to calculate the cooling effect from solar panels in specific climates.