$CWET Here's how it works: water is pumped into the giant hollow tower and sprayed as a fine mist into the hot, dry air at the top. The mist evaporates, cooling the surrounding air and making it dense and heavier. This weightier air then falls inside the tower at speeds up to 100 mph, turning large wind turbines at its base. The fast-flowing air is funneled through these turbines into generators, which then produce low cost electricity.