Ellen Macarthur Foundation


Osmosis: first tests underway in Norway

Opened on 24th November 2009, the world’s first osmotic power plant operated by Statkraft, Europe’s largest renewable energy company, is an experimental facility based on the Oslo Fjord in Norway. According to the plant’s owners, osmotic power is a “clean, renewable energy, with a global potential of 1 600 to 1 700 TWh – equal to China’s total electricity consumption in 2002.”

How does it work?

Osmosis is the natural phenomenon that occurs when a liquid solution moves across a semi-permeable membrane, separating two solutions of different concentration. This movement releases energy, which can be harnessed. When fresh water meets salt water, osmosis happens and the amount of energy developed is considerable.

“At the osmotic power plant”, Statkraft officials explain, “fresh water and salt water are guided into separate chambers, divided by an artificial membrane. The salt molecules in the sea water pulls the freshwater through the membrane, increasing the pressure on the sea water side. The pressure equals a 120 metre water column, or a significant waterfall, and can be utilized in a power generating turbine.”


What can be expected?

The Statkraft plant, opened in Tofte on the Oslo Fjord, is an experimental facility, but officials say that a commercial unit could see the light of day sometime between 2015 and 2020. The size of such a plant should remain modest, as it is estimated that a unit the size of a football pitch can produce enough electricity to supply around 30 000 homes. Osmotic power could prove very interesting for large cities, as many of them are located where large rivers meet the sea, and existing or disused industrial installations can be used (the Tofte plant itself is an old paper pulp factory).


The technology is however still very expensive to implement, and will only develop if technical partnerships are put in place, notably with membrane manufacturers – as this element is a crucial part of the system. The ecological impact of osmosis power plants is not negligible either, as it impacts on local biodiversity, just like other types of hydropower facilities (fish population, aquatic flora etc). Even if it is widely accepted that the technology is still not mature, the potential does exist and widening the range of technologies is vital when it comes to renewable sources.

For a video animation illustrating the system at work, go to statkraft and click on Osmotic power in the right hand-side menu.

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