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Rivers flowing into the sea offer great potential as electricity source


July 27, 2012
By Anthony Capkun

July 26, 2012 – The latest episode in the American Chemical Society’s (ACS) Global Challenges/Chemistry Solutions podcast series describes a process that could pave the way for a new genre of electric power-generating stations; by tapping just 1/10th of the global potential of a little-known energy source that exists where rivers flow into the ocean, these stations could supply electricity for more than a half billion people.

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 for free at iTunes and from www.acs.org/globalchallenges. In the report, Elimelech and Yip explain that a process called pressure-retarded osmosis (PRO), which exploits the difference in saltiness between freshwater and seawater. PRO requires no fuel, is sustainable and releases no carbon dioxide.

In PRO, freshwater flows naturally through a membrane to dilute seawater on the other side. The pressure from the flow spins a turbine generator and produces electricity. 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 1/10th of the global river water flow into the oceans could generate enough power to meet the electricity needs of 520 million people. The same amount of electricity, were it produced by a coal-fired power plant, would release more than 1 billion metric tonnes of greenhouse gases every year.