PV and thermal- a new approach to solar energy

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.

Vinod Khosla, the former tech mogul and now energy venture capitalist, sees potential in PVT Solar. (Photo: Bloomberg)The company is currently testing electronic controllers that play traffic cop for the collected heat, pumping it automatically, using a small fan, to the basement hot-water heater, for example, or to individual rooms, or even to the swimming pool, as needs arise. If the heat is not needed in the building, the fan vents it to the outside.

Because solar panels perform better at cooler temperatures, removing heat from around the panels also has the effect of increasing their production on hot days — adding to the overall efficiency gains for the system.

And given that the system requires little or no additional infrastructure, it can be deployed with only a small amount of added cost.
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If taxpayers are to look now to support anything, shouldn't it be renewable energy that will pay them back in years to come with a sustainable planet for their children and granchildren with cheaper energy prices, more and better jobs, and cleaner safer choices? Joining phototvoltaics to thermal solar is a great way to do just that. So while we are getting all wrapped up in the 'financial crisis,' realize the other crisis this planet now faces that is even more urgent that is related to our economy and the ways in which we can make positive changes.

The solution comes up every morning.