Earth Equity News

PV and Thermal: A New Combined Cycle. By Matthew L. Wald, NYTimes, September 30, 2008. "One of the limitations of solar photovoltaic systems is that, at the current state of the technology, no more than a quarter of the energy from the sun is converted to electric current. Most of the rest of the energy is lost as waste heat. But Vinod Khosla, the founder of Sun Microsystems and now a technology entrepreneur and alternative-energy venture capitalist, says he's found a solution that doubles or even triples the energy yield -- a gargantuan leap in a field where engineers exult over the most incremental gains. Mr. Khosla is funding a company called PVT Solar, of Berkeley, Calif., where engineers two years ago began trying to harness that wasted heat. In a sense, it was already being collected, either in the solar modules themselves, or underneath. (Solar arrays are often installed at an angle, to face the sun, thus creating a wedge-shaped space below for heat to collect.) PVT's founders decided the heat could be harnessed and pumped into the home for climate control, water heating and other uses. It is a sort of combined cycle for solar -- a marriage of solar photovoltaic technology and solar thermal systems, which gather the sun's energy in the form of heat."