Giant solar tower could power the future

A new energy concept called a solar tower could generate enough electricity for 200,000 homes. Looking like a giant smokestack, it would release no noxious fumes — just sun-heated air.

Demonstrated more than 20 years ago, the basic design calls for solar collectors to warm the air near Earth’s surface and then channel it up the tall central tower. Turbines placed at the bottom make electricity from the updraft.
On a sunny day, the air at the top of the tower would be 70 degrees Fahrenheit (20 degrees Celsius), whereas the air in the greenhouse could reach 160 degrees Fahrenheit (70 degrees Celsius). As this hot air escapes up the tower at 34 mph (15 meters per second), it spins 32 turbines that generate up to 200 megawatts of electricity.

Even with all this power, the solar tower is less than one tenth as efficient as solar cells in converting the sun’s energy into electricity.

The advantage for a solar tower is that its materials are much less expensive.

A 200-megawatt solar tower would cost upwards of a billion dollars to build. According to a 2005 industry report, this would imply about 10 cents per kilowatt-hour, which is roughly a third of the cost of electricity from current solar cells.

However, a solar tower must be fairly big to be effective. EnviroMission has recently developed a slightly smaller design that has a maximum output of 50 megawatts that may be appropriate in some markets.

MSNBC