18 June 2010

Solar Heat and Power Systems On the Horizon

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For the last few years, much of the innovation around solar technology has been aimed at generating more electricity from sunlight. But a new crop of entrepreneurs is working to use the sun more efficiently by using its heat, as well as its light, for individual business, factories and, perhaps one day, even homes.

These companies say that providing both electricity and heat reduces the amount of time it takes customers to recoup their investments. "It's a single system that provides the greatest impact on a homeowner's energy bill," says Sam Weaver, CEO of heat and power solar startup Cool Energy.

These technologies stand to benefit if natural-gas prices rise, considering that natural gas is used both for heating and for electricity. Those prices rose after the Deepwater Horizon oil rig sank and began leaking oil in the Gulf of Mexico, amid concerns that the spill could reduce natural-gas production, and prices could rise again if hurricanes hit the Gulf Coast and reduce production. A gas pipeline explosion in Texas probably doesn’t help either.

In general, the new combined-solar-heat-and-power systems are based on the same concentrating solar-thermal technology used by the big solar projects — both already built and in the works — in the Mojave Desert. (The 392-megawatt system BrightSource is building with its $1.37 billion federal loan guarantee is one of these.) The large desert systems concentrate sunlight and use it to heat fluid running in tubes. Then, that steam can be used to run a turbine and make electricity.

With the systems for homes and businesses, the heat would be used directly for warm air or hot water, or — although it may seem counterintuitive — could be used to run an air conditioner. (Heat paired with an absorption chiller, for example, can power air conditioning.) Meanwhile, some of the systems siphon a portion of the steam to make electricity, such as via a generator, while others use photovoltaic cells, and in some cases concentrators that direct sunlight to those cells, to produce electricity.

(Renewable Energy World)

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