Avoiding Sun Burn: Rooftop Solar Panel Safety Tests

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New facilities use everything from guns to temperature extremes to test the safety of photovoltaics and other clean energy technologies

By David Biello

A new 2,100-square-meter building outside Frankfurt, Germany, houses a series of chambers that can simulate a hot, humid day or temperatures so frigid that metals crack, and every punishing weather scenario in between. It's all for testing one product—solar photovoltaic panels—and it's the third such facility opened since 2008.

Underwriters Laboratories, perhaps most recognizable for the ubiquitous "UL" in a circle that is printed on many gadgets, was founded back in the late 19th century by insurance companies looking to forestall the fires endemic to the new era of electrification by safety certifying electrical products. And that's exactly what UL is doing today for solar panels, which have grown from roughly 20,000 modules made or installed in the U.S. alone in 2000 to more than 520,000 modules by 2008, according to the U.S. Department of Energy.

"In the U.S. we tend to build our houses out of fuel [wood]. Then we put these solar panels on the roof," says UL CEO Keith Williams. "Most of our activity right now is related to safety testing for solar panels and modules as well as electrical components that would connect the solar panel to the house and grid."

That doesn't mean such panels aren't safe, just that they pose at least a fire threat if improperly connected. UL also tests the products' capacity to stand up to the rigors of home use. That means shooting spherical ice cubes from a pneumatic gun to mimic a hailstorm, baking panels at temperatures of up to 90 degrees Celsius, and blasting them with concentrated spotlights to put heat and thermal stress on specific parts of a given panel. The units are even subjected to high humidity followed by a chill-down to –40 degrees C—a condition unlikely to occur in the real world—to see if the PV will crack or break as the water freezes and expands.

The whole series of tests takes around six months and costs roughly $50,000 for the company looking to get its product certified. "You want to have a test that will stress the product in the ways that it's most normally going to be used and abused," Williams says, "and therefore make sure that under normal use and some forecastable abuse that the product will retain its safety."

UL's clean energy efforts are not confined to solar, of course. Its European division is now testing wind turbine components and it has opened a facility to study batteries in Taipei, Taiwan. "You're going to have in the future storage devices in a house or office building or your car," Williams says. "People are going to put them in locations they shouldn't be at times. And when you have a million electric vehicles on the road, you start to have issues with accidents and first responders."

But the company continues to expand its solar efforts, including installing 22.5 kilowatts worth of solar panels on the rooftop of its Chicago headquarters. "We're going to learn a lot about the long-term performance of solar panels by owning some of our own," Williams says.

Manufacturers ranging from Applied Solar to Sharp have had their products safety tested in order to get them ready for sale in the U.S.—and most panels on the market bear UL certification. That endorsement is not foolproof, however; UL-certified panels have been involved in incidents in California and other states. But the few fires thus far have largely been sparked by wiring failures and most involved improper installation or faulty insulation of the wires connecting the panels to the house, according to the California Solar Energy Industries Association. UL also runs a training facility in North Carolina for electrical inspectors and other building code authorities to learn what to look for when examining a home-mounted solar power installation.

In addition to existing PV testing facilities in Frankfurt, San Jose, Calif., and Suzhou, China, UL is building other solar testing facilities in Osaka, Japan, and Bangalore, India. The latter will explore another promising solar option for the developing world: stoves powered by sunlight.

"In India you already have a market for solar-powered cooking devices," Williams notes. "We think that market will grow. In large parts of the world small, stand-alone solar devices—whether for cooking or water processing—could be very important."

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