April 18, 2012--Rivers flowing into the sea offer vast potential as electricity source (Science Daily)

A new genre of electric power-generating stations could supply electricity for more than a half billion people by tapping just one-tenth of the global potential of a little-known energy source that exists where rivers flow into the ocean, a new analysis has concluded. A report on the process -- which requires no fuel, is sustainable and releases no carbon dioxide (the main greenhouse gas) -- appears in ACS' journal Environmental Science & Technology. Menachem Elimelech and Ngai Yin Yip explain that the little-known process, called pressure-retarded osmosis (PRO), exploits the so-called salinity gradient -- or difference in saltiness -- between freshwater and seawater. In PRO, freshwater flows naturally by osmosis through a special membrane to dilute seawater on the other side. The pressure from the flow spins a turbine generator and produces electricity. The world's first PRO prototype power pla