New research may bring solar thermal flat panels home

A solar panel that provides hot water and electricity? Scientists from Boston College and MIT say it's on the horizon.

Solar thermal energy heats many a home's water, but someday generating electricity might also appear on its list of household chores. Boston researchers have designed a flat panel that could expand solar thermoelectric power's reach from the domain of large plants to neighborhood rooftops.

In solar thermal plants, sunlight heats water, with the resulting steam powering a turbine that generates electricity. These systems need to collect a lot of heat, and not lose it, to run at the highest efficiency. To achieve necessary temperatures, the plants often employ mirrors that direct concentrated sun rays toward fluid within vacuum-sealed tubes. Unfortunately, generating electricity in this fashion pretty much comes in one size—and that's big, as in BrightSource Energy's concentrated solar farm on thousands of desert acres in California . Meanwhile, an advantage of photovoltaic panels is that they work for utility-scale generation, as well as for distributed power through rooftop installations.

Homes do have solar thermal systems, but generally they warm water and not light bulbs. Scientists from Boston College and MIT hope this won't always be the case. Publishing yesterday in Nature Materials, they demonstrate a device that can do both. According to the study, enhanced thermoelectric nanomaterials and an improved surface used for absorbing solar energy allowed a flat panel to perform 7 to 8 times more efficiently than previous solar thermoelectric generators. No mirrors required. Instead the solar absorber, operating in a vacuum, concentrates the heat via conduction onto thermoelectric materials set upon a copper plate.

The researchers also say their device could be compatible with existing solar heaters.

Co-author Zhifeng Ren, a professor of Physics at Boston College, says in a statement:

Existing solar-thermal technologies do a good job generating hot water. For the new product, this will produce both hot water and electricity. Because of the new ability to generate valuable electricity, the system promises to give users a quicker payback on their investment.

How much quicker? The researchers say by a third. And though a commercial product has yet to see the light of day, their company GMZ Energy recently raised $7 million in funding.

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Images: NASA, Flickr/International Rivers, and Boston College

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