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NORWEGIAN renewable energy firm Statkraft has opened the world’s first osmotic power plant at Tofte in Norway.

The prototype plant was opened by Norwegian crown princess Mette-Marit and is the result of over ten years of work and NOK100m ($18m) of investment. The plant has been built for testing purposes, to develop technology originally trialled at pilot plants in Trondheim and Sunndalsøra. It will initially produce only very small quantities of electricity but Statkraft hopes that improvements made to the process at the Tofte plant will enable it to have a commercial plant in operation by 2015.

Freshwater and saltwater are pumped into the plant separately and filtered to remove any debris. The water is then pumped into pressure vessels in which a polymer semi-permeable membrane is coiled up. The freshwater flows across the membrane, raising the pressure on the saltwater side. The pressurised water can then be used to drive a turbine. Pressure exchangers recycle the water pressure.

Statkraft says that apart from the membrane, all the technology used in the plant is well-known and well-understood, and work at Tofte will focus on improvements to the membrane. A plant the size of a football stadium could produce enough electricity to power 30,000 homes, and could be built anywhere where freshwater runs into the sea. The company estimates that the potential global energy output from osmotic power plants could be as high as 1600–1700 TWh/y, equivalent to 50% of Europe’s electricity needs.

“This new technology generates electricity simply by mixing water. New solutions to meet the climate challenges might be closer than we expect, which makes me confident that the future looks bright,” says Statkraft ceo and president, Bård Mikkelsen.