Statkraft Osmotic Power Plant, Tofte, Norway

The Statkraft osmotic power plant at Tofte, Norway, is the first osmotic power or salinity gradient power generation plant in the world. The prototype based on osmotic technology was constructed and owned by Statkraft. It is operated by SINTEF Energy Research, a research division of SINTEF Group.

The prototype will be opened on 24 November 2009 by Crown Princess Mette-Marit of Norway. The completely commercialised osmotic power plant will be ready by 2015.

The plant generates renewable and emissions-free energy and thus contributes to eco-friendly power production.

It is estimated that the osmotic technology will produce 1,600TWh-1,700TWh a year, which is about 13 times the hydro power generated in Norway annually. Out of the total estimated osmotic power of 200TWh that is expected to be generated in Europe, 12TWh will be generated in Norway.

Tofte plant history

The generation of electric energy through osmosis was developed by Sidney Loeb during the 1970s.Work on the theoretical potential of the osmotic power was carried out by Torleif Holt and Thor Thorsen during the 1980s.

In 1997, a project to implement the osmotic power generation technology was established by Holt and Thorsen in collaboration with the renewable energy company Statkraft.

EU funds were awarded to osmotic power research in 2001. The funds awarded accelerated the research work being carried out, leading to the first environmental study also being carried out in 2001. Statkcraft filed the first patent for osmotic power membranes in 2003, after which the company began work on a test facility at Sunndalsøra.

The prototype of osmotic power plant was constructed in 2008 at Tofte, Hurum, in Buskerud County, Norway.

Construction

Osmotic power plants are constructed where fresh water flows out into the sea. The concentration of salt in the seawater should be sufficiently high to generate the required pressure.

The premises of Sodra Cell Tofte, a paper pulp factory, were leased by Statkraft to construct the osmotic power prototype. The site is an industrial area with access to both fresh and seawater.

Construction of the main building was complete by 2008. By December 2008, construction on the purification plant that maintains full control of the raw water was completed up to the first floor.

The installation of water pipe systems outside the power plant was carried out in February 2009, while the installation of pipe systems inside the power house began in March 2009.

Osmosis technology

Osmosis is a natural process used to generate power by considering the enormous energy released when freshwater meets saltwater. In this process the water is transported through a semi-permeable membrane, an organic filter with extremely small holes.

The plant incorporates two chambers separated by an artificial membrane to store freshwater and saltwater. The pressure generated by the transfer of water through the membrane in one direction is used to generate electricity. The pressure in the seawater chamber will be increased as the salt in the seawater draws the freshwater through the membrane. The plant utilises hundreds of meters of pipes to channel both salt water and freshwater into the power plant.

The pressure generated will be equal to that of a water column of 120m, and can be used in driving turbine to generate electricity.

The osmotic power plant will not discharge any pollutants to the atmosphere. Nor will it affect the sea floor or the river habitat.

Development

The prototype will be mainly used for testing and development purposes as it has limited production capacity. The development activities include work to develop a membrane, that draws required quantity of water to create effective pressure for running the turbine.

The research groups in Norway, Germany and the Netherlands along with Statkraft are involved in the development of the membrane technology.

Project Finance

The entire project is being funded by Statkraft with the aid of Enova SF (Enova) and the Research Council of Norway.

About NKr100m (approximately $18m) was invested by Statkraft in the development of the power plant technology. The prototype was supported by the Royal Norwegian Ministry of Petroleum and Energy's Enova, while the research work was supported by the Research Council of Norway.