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Earth Notes: Honoring the Sun I: Solar Panels’ Side Benefit

Rooftop Shading

This month, as nights grow long, Earth Notes pays homage to the sun and to some of the lesser-known ways it can fuel our lives.

It’s well known that photovoltaic solar panels produce clean, renewable energy. But a new study suggests that they can have an unintended consequence: in some climates, panels mounted on roofs may help keep interiors cool in summer and warm in winter.

University of California engineers noted these side effects last spring when they used an infrared camera to monitor a university building in San Diego. They determined that parts of a roof covered with solar panels were five degrees cooler than sections exposed directly to the sun.

Overall, the amount of heat reaching the building’s roof was trimmed by 38 percent. This means the electric-powered cooling system didn’t need to consume as much energy on warm days.

The same shade keeps sunlight from warming those roof areas on cold winter days. But the scientists point out that the panels are likely to keep heat in on cold nights. During winter, these two effects are likely to cancel each other out, while the summertime shading effect should produce real energy savings.

The research team plans to develop a calculator that could predict the cooling and heating advantages of solar panels in specific areas. The near-daily sunshine of the Southwest means that roof-mounted solar panels could play a big role in not only producing electricity, but reducing our overall need for it.