ZPEnergy.com - Looking Into the Sun

If David Slawson is right about solar power, our days of oil dependency are numbered.
From: Inc. Magazine, July 2005 | Page 76 By: David H. Freedman Photographs by: Brad Wilson

"...Slawson’s company, Stirling Energy Systems, has some interesting credentials, including ownership of technology developed by McDonnell Douglas, Southern California Edison, and others at a cost of $400 million; $3 million in grants from the Department of Energy; a steady flow of angel investment that he says has averaged $2 million a year for nine years; a preliminary agreement to provide a major utility with up to $2.7 billion worth of electricity over 20 years; and another $1.3 billion deal on tap with another utility...

...Solar energy seems like a no-brainer—hey, free energy from the sky, what’s not to like?—but on closer inspection some thorny issues pop up. The biggest one is the “conversion efficiency” issue. Sunlight is energy, all right, but it needs to be converted to a form that can be used to run cars, heat homes, and display Leno. Electricity fills the bill, but a funny thing happens when you enlist sunlight to create electricity: Most of the energy flits away uselessly. The most common approach is to use sunlight to knock electrons out of a semiconducting material like silicon, creating an electric current. But the efficiency of even the very best photovoltaic systems, as the approach is called, tops out around 15%—in other words, 85% of the sunlight’s energy is wasted. Big, expensive solar panels in very sunny areas produce relatively little power, which winds up costing about 25 cents per kilowatt hour of electricity. (A kilowatt is about enough to power 14 75-watt bulbs.) Electricity from a conventional natural-gas-burning power station, by contrast, costs about seven cents per kilowatt hour.

Slawson’s library raid turned up a book that detailed a different approach: a thermoelectric solar dish system developed by McDonnell Douglas (later absorbed into Boeing) with a Swedish firm called Kockums, technology that was later sold to and tested by Southern California Edison. Instead of using rays of sunlight to knock out electrons, the dish reflects and concentrates the rays in order to heat and thus expand a gas. That expansion is then put to work by a device called a Stirling engine to turn a conventional electric generator. The approach is nearly twice as efficient as most photovoltaic systems—while doing away with semiconductors and other expensive materials..."

Read the whole article here: Looking Into the Sun