Points of Interest | Green Energy News

March 7, 2004 – Vol.8 No.50

POINTS OF INTEREST.

A weekly collection of websites worth visiting.

When we think of solar energy the first technology that comes to mind is solar photovoltaics (PV) - electrons knocked loose from metals bombarded by photons to create an electric current.

But we often forget or ignore other solar energy technologies - thermal solar - utilizing the heat from sunlight.

It’s surprising that solar thermal technologies aren’t better recognized and appreciated. Of the many things that the sun does for our planet, what it does best is keep us warm under our greenhouse gas blanket. So you’d think that solar thermal energy should be in the forefront of energy research and development.

Perhaps it’s too easy, too obvious.

The solar thermal technology being developed and commercialized by Stirling Energy Systems (SES) uses a parabolic dish reflector to concentrate sunlight to provide heat to run a Stirling engine. Mounted in the focal point of the dish, the four-cylinder Stirling engine operating on its external heat source turns a generator to supply electricity.

While the technology, on the surface, may seem more complex than solar photovoltaics, it can provide power at far less cost. SES is quoting a price of 7.4 cents per kilowatt hour for installed systems - today. According to the U.S Department of Energy PV solar probably won’t reach that cost until 2025.

SES gives credit to its low price per kilowatt hour to the technology’s high energy efficiency now at 29.4 percent. Further, the use of tried and true methods to build the reflector dish and Stirling engine as well as common materials keeps the cost well below PV. Next generation technology from SES, due to be introduced within a year, should bring efficiencies up to 33 percent.

(By comparison, the end product, what the consumer sees, of PV solar - a solar cell - seems simple enough. But it’s the difficult manufacturing process and pricey materials that make the technology expensive.)

True, SES technology is meant for grid-connected systems and can’t be integrated into buildings the way PV solar can. The company does, however, offer a 10-kilowatt version designed for off-grid installations for rural electrification, water pumping, remote cottage industries, schools, etc.

The technology is also adaptable for hybrid installations. Other thermal sources, such as the combustion of biomass fuels, could be used as an additional source of heat for the Stirling engine generator. Visit SES at http://www.stirlingenergy.com/