The plants work by generating pressure differentials between warm and cool air at the surface. Four acres of solar panels sit around a 2,400-foot-tall chimney, and above turbine-laden tunnels. The panels heat the air closer to the chimney far faster than the air at the ends of the tunnels. The warmer, less dense air then serves as a partial vacuum, drawing in the colder, denser air at the edges through the tunnels fast enough to spin the turbines and generate electricity.