Cogenra’s Double Whammy: Solar Arrays that Generate Electricity and Hot Water

7/18/11

A Silicon Valley startup is trying to squeeze more energy out of sunlight by combining photovoltaic arrays with a technology to generate hot water, to lower the costs of both electricity and heat.

Based in Mountain View, CA, and backed venture capitalist Vinod Khosla among others, Cogenra Solar has fielded only two installations thus far. But CEO Gilad Almogy says Cogenra aims at a huge swath of industries and applications that require both electricity and heat, including food processing plants, pharmaceutical factories, hospitals, jails, and apartment complexes.

“Everywhere there is a significant use of heat, our systems make sense,” Almogy said.

The company, formerly known as Skywatch Energy, made a splash in November when former British Prime Minister Tony Blair took part in the unveiling of a Cogenra installation at Graton, CA-based Sonoma Wine Company, which uses the hot water to wash out wine barrels.

Cogenra employs several technical tricks to coax more than 75 percent of the energy from sunlight—most of this in the form of hot water—versus the 20 to 25 percent of an efficient photovoltaic array.

Its systems are long half-cylinders of reflective material that concentrate sunlight on a photovoltaic strip running the long way down the focal point of the array.

In addition to converting part of the sun’s rays into electrical energy, the metal in the photovoltaic strip becomes extremely hot. Cogenra runs water though an insulated metal tube behind the photovoltaic array, thus capturing that heat and using it to warm water to anywhere from 70 to 170 degrees Fahrenheit, depending on customer need.

Cogenra says customers who install its systems qualify for solar hot water system rebates, such as those provided by the California Solar Initiative (CSI), as well as rebates for electricity-generating photovoltaic systems. Taking its thermal and electricity rebates together, Cogenra says … Next Page »

Tom Abate is a freelance writer in the San Francisco Bay Area who has covered science, high-tech, biotech, and economics. Follow @

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