Rivers flowing into the sea offer vast potential as electricity source

The latest episode in the American Chemical Society's (ACS') award-winning Global Challenges/Chemistry Solutions podcast series describes a process that could pave the way for a new genre of electric power-generating stations. These 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.

Based on a report by Menachem Elimelech, Ph.D., and Ngai Yin Yip in the ACS journal Environmental Science & Technology, the new podcast is available without charge at iTunes and from www.acs.org/globalchallenges.

In the report, Elimelech and Yip explain that the little-known process, called pressure-retarded osmosis (PRO), exploits the difference in saltiness between freshwater and seawater. PRO requires no fuel, is sustainable and releases no carbon dioxide (the main greenhouse gas).

In PRO, freshwater flows naturally 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 plant was inaugurated in Norway in 2009. With PRO appearing to have great potential, the scientists set out to make better calculations on how much it actually could contribute to future energy needs under real-world conditions.

Elimelech and Yip concluded that PRO power-generating stations using just one-tenth of the global river water flow into the oceans could generate enough power to meet the electricity needs of 520 million people, without emitting carbon dioxide. The same amount of electricity, if produced by a coal-fired power plant, would release more than 1 billion metric tons of greenhouse gases every year.

Provided by American Chemical Society