The Science of Science Fiction: Energy from Hot Air

I saw this article on CNN yesterday and thought it had an interesting idea for an energy source. Since hot air naturally rises (because it's less dense than cold air), an Australian entrepreneur wants to use it as a potential source of energy. The idea would be to build a very tall tower (2,600 feet) and surround the ground around it with a canopy. The sun would heat the air under the canopy, which would then flow into the tower. As the air rises, it would spin turbines which would be used to create electricity--enough to power 100,000 homes every day. Is the idea feasible? There are some concerns about how long the tower would stand and if it really would produce as much energy as promised. But if it works, it would offset the environmental costs in less than three years. Funding still has to be secured, but whether or not the real tower is built, it's still a concept that might be used in near-future science fiction.