Emerging Renewables: Solar Updraft Tower

For centuries, architects have taken advantage of rising heat to help cool some structures. Solar chimneys allow the rising air to go out of the building, taking the heat with it. Today, Australian entrepreneur Roger Davey wants to take advantage of that phenomenon -- with a twist.

He wants to create, capture and control hot air to help power cities. He plans to build a huge solar updraft tower, 2,600 feet tall, in the Arizona desert. As the hot air moves into the tower, it would turn 32 turbines, spinning them fast enough to create mechanical energy, which generators convert to electricity. His company, EnviroMission, says such a tower can create up to 200 megawatts of power, enough to power 100,000 homes. He says they don't intend to put coal or nuclear or alternative power out of business, but want to be a strong, no-carbon emission supplementary source.

"One of the most important things I think that differentiates this from anything else is its ability to produce power as and when required," said Davey, chief executive and executive director of EnviroMission, the company behind the solar updraft tower. That sets it apart from solar (not available at night) and wind energy (not available on a calm day), which he referred to as "spasmodic." He also touted its ability to produce power without the use of water to generate electricity. Coal-fired and nuclear plants use massive quantities of water (40% of all U.S. freshwater) and solar panels need to be washed frequently to keep them working well.