Cooling Benefits of Solar Panels

09/14/2011 |

Photo left: A Google Earth image of the Powell Structural Systems Laboratory with a tilted solar panel array on the north side and a flush solar panel array on the center of the roof.
Photo right: A thermal infrared image of the ceiling of the Powell Structural Systems Laboratory, taken at 5:10 p.m. on April 19, 2009. The color bar shows temperatures in degrees Kelvin. The footprint of the tilted solar panel array is visible as a cool area in the center of the image.

Not only do the solar panels on your building’s roof provide clean power, they cool your workplace too, according to a team of researchers led by Jan Kleissl, a professor of environmental engineering at the University of California, San Diego (UCSD) Jacobs School of Engineering.

Using thermal imaging, researchers determined that during the day, a building’s ceiling was 5 degrees F. cooler under solar panels than under an exposed roof. At night, the panels helped hold heat in, reducing heating costs in the winter.

On the building studied, Kleissl’s team determined that the amount saved on cooling the building amounted to getting a 5% discount on the solar panels’ price over the panels’ lifetime; the savings in cooling costs amounted to selling 5% more solar energy to the grid than the panels are actually producing.

Rather than allowing the sun to beat down onto the roof, which pushes heat through the roof and inside the ceiling of the building, PV panels take the solar beating. In addition, much of the heat is removed by wind blowing between the panels and the roof. These benefits are greater if there is an open gap where air can circulate between the building and the solar panel, so tilted panels provide more cooling. The more efficient the solar panels, the bigger the cooling effect, according to Kleissl. For the building the researchers analyzed, the panels reduced the amount of heat reaching the roof by about 38%.

“There are more efficient ways to passively cool buildings, such as reflective roof membranes,” Kleissl says. “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.”


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