Solar Panels Offer Passive Energy Bonuses

Energy Boom, Jeanne Roberts

According to a report soon to be published in Solar Energy, solar photovoltaic (PV) panels on roofs are also doing a good job of keeping houses and buildings cooler in summer and warmer in winter.

The best cooling effect is found with tilted solar panels, according to the report by Jan Kleissl, a professor of environmental engineering at the University of California's Jacobs School of Engineering in San Diego. Tilted panels are so successful because they allow air to pass between panel and roof.

Five degrees (Fahrenheit) cooler, to be exact, Kleissl and fellow researchers noted when they examined the roof of the Powell Structural Systems Laboratory with a thermal camera that tracks infrared.

The Powell roof supports not only tilted panels to take advantage of the sun’s average declination in Southern California, which is about 78 degrees in summer, but panels mounted flat to the roof and even a section of bare roof, all of which made the Kleissl team's real-world measurements both more accurate and more reliable.

What works for cooling a roof, and the building under it, also works for keeping heat inside in the winter. Kleissl estimates that the cooling and heating energy savings of a roof equipped with solar panels was equivalent to saving 5% on the cost of the panels themselves.

As the rising number of rooftop solar installations across the U.S makes it more important than ever to consider their impact on buildings' total energy costs.

Equally as important, the passive cooling and heating provided by solar panels actually increases their value from a consumer perspective, and might be an additional selling point to solar installation firms, especially those working in hot climates.