As the turbines spin, clean renewable energy will flow into the power grid. In short, it's an interesting mix of the best of both solar and wind power; but unlike solar and wind, the mechanical energy created by Davey’s machine allows the unit to operate 24/7. As for cost, the project has a $750 million price tag. According to a 2005 industry report, this would imply about 10 cents per kilowatt-hour, which is roughly one-third the cost of electricity from current solar cells and almost half of the cost from nuclear power. Financial models suggest the tower will pay for itself in 11 years; engineers believe the tower will have a life span of 80 years. Once it’s built, Davey’s tower can be expected to produce power with virtually no maintenance. Better yet, it requires no "feed stock" — nothing but air and sunlight spin the turbines...Instead, hot air rushes out of the huge, towering mouth of Davey's creation — enough hot air, in fact, to turn a massive turbin...