Solar panels keep buildings cool too, say researchers

Solar panels on building roofs don’t just provide clean energy they also cool the building, according to researchers at the University of California San Diego Jacobs School of Engineering.

In a peer-reviewed article in the journal Solar Energy, the researchers led by professor of environmental engineering Jan Kleissl show that photovoltaic panels produce a 5°F cooling effect at the building’s ceiling.

The solar panels basically act as roof shades, absorbing the incoming sun’s rays. Tilted panels provide more cooling, allowing wind and air currents to remove heat from the roof area.

The researchers estimate that the cooling effect amounts to a 5% saving on the cost of the solar panels over their lifetime.

“Talk about positive side-effects,” says Kleissl. “There are more efficient ways to passively cool buildings, such as reflective roof membranes, but if you are considering installing solar photovoltaic… you can expect a large reduction in the amount of energy you use to cool your residence or business.”

In the winter, although the panels would stop the building warming up during the day, they would keep in accumulated heat during the night, essentially cancelling out the two effects.

The researchers hope now to develop a calculator that can predict the cooling effect on individual roofs in specific climatic areas.

For further information:
Anthony Dominguez, Jan Kleissl and Jeffrey C. Luvall. Effects of solar photovoltaic panels on roof heat transfer. Solar Energy (2011), doi: 10.1016/j.solener.2011.06.010

Related stories:
US invests $27 million in reducing the cost of solar power (7-Feb)
US research lab and Vitex join forces on solar roof tiles (8-Jun 2009)
Shiny roofs and pavements could counter global warming (19-Sept 2008)

19 July 2011

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