Water is an ancient power source, one usually exploited by harnessing its flow. For decades, though, scientists have been working on another kind of water power—one relying on salt. Yarek Waszul This technique exploits the natural process of osmosis. When fresh water is separated from salt water by a selective membrane, pure water from the fresh side will pass through, leaving the salts behind. The rising water level on the salty side, kept under moderate pressure, can then be siphoned off to run a turbine. This approach is ideal for places where fresh water and salt water come together—where a river meets the sea, for instance. The technology is appealing because it is clean, renewable and reliable. The problem is cost: It takes a vast membrane to obtain any significant amount of electricity. But now researchers at the Massachusetts Institute of Technology and Saudi Arabia’s King Fahd University of […]