The Solar Tower, according to wired, "is one of the most ambitious alternative energy projects on the planet: a renewable energy plant that pumps out the same power as a small reactor but is totally safe." Hollow in the middle, the tower has a base with a solar collector, a 25,000-acre "skirt." As air under the collector is heated by the sun, it's funneled up the chimney by convection, as it accelerates to 35 m.p.h., it begins driving 32 wind turbines that in turn generate electricity much like wind farms do. But unlike traditional wind farms and solar generators, the Solar Tower can operate round the clock, even when there's no wind, because it has banks of solar cells which can store heat energy.
Though the tower could generate up to 200 megawatts--enough electricity to power 200,000 homes and will keep 830,000 tons of greenhouse gases out of the atmosphere annually—it comes at high cost; with production costs somewhere between $500 million to $750 million these things don't come cheap. ::Wired News [by MO]