Touted as the nation's greenest public swimming pool, the recently renovated Richmond Municipal Natatorium in California is expected to save the city's recreation department up to $300,000 annually on utility bills. Built in 1926 and closed since 2001 because of structural failures, the Olympic-sized pool harvests the sun to meet half its energy needs. A 32-kilowatt solar electric system and 3,600 square feet of Heliodyne Inc. Gobi 410 solar hot water panels on the roof heat 324,000 gallons of water. A saline chlorination system generates residual chlorine by changing salt molecules to chlorine molecules using electrically charged titanium plates. Humidity is controlled naturally by opening and closing the building's 200 windows. The $7 million restoration was designed by Todd Jersey Architecture and installed by Sun Light & Power, both of Berkeley, Calif.