byJennifer Kho, ContributorPublished: 2010-06-17
California, United States –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.
A Symbiotic Relationship
Pairing solar heat and electricity is an attractive idea because, companies say, a combined system would cost less than two separate systems, and could be far more competitive compared to the price of both a heating and an electric system added together. On top of that, the technologies fit well together, according to Jenny Chase, lead solar analyst for Bloomberg New Energy Finance. “Generally speaking, you have something that wants heat and something that wants to get rid of heat,” she says. All photovoltaic cells lose their efficiencies at higher temperatures, and that challenge is exacerbated with concentrating-photovoltaic technologies, which get very hot, she explains. Solar-thermal technologies could potentially use that heat, keeping the photovoltaic systems cool.
And as solar prices continue to fall and conventional electricity prices remain low, companies are looking for ways to stand out from the competition and to do more with less, such as by boosting the value of solar energy. Technologies have improved, reducing the expected prices of combined heat-and-power solar systems and raising their efficiencies, and state and federal policies pushing more renewable energy. “People are starting to think more broadly,” Weaver says. “People are realizing that in a lot of places, electricity is not the largest part of the energy bill and are taking a more holistic
View the Original article