Vast potential as carbon-free energy source

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 of Yale University 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.