In November 2009, a prototype osmotic power station went online on the banks of the Oslo fjord in Norway. It generates power using osmosis, which occurs naturally when two solutions of different concentrations meet each other at a semi-permeable membrane. The pressure difference generated as one liquid passes through the membrane can be converted to electricity. In this prototype power station, the two liquids used are salt water from the sea and fresh water from run-off into the sea. The station’s initial capacity is around 4 kilowatts, enough to heat a large kettle, but scientists hope that this can be increased to 25 megawatts by 2015.
