Osmotic Power - A new frontier for SHP collaboration

Contributed by Edward Y. Sumoto eys@inshp.org

Traditional hydropower has long been situated at rivers and more specifically, freshwater sites. But there is increasing interest in exploiting the great power that the sea offers. Amongst such implements like floating turbines, a particularly promising and interesting technology is osmotic power.

Led by Dr. Rolf Jarle Aaberg of Statkraft, a state-owned engineering company in Norway, osmotic power has already moved out of the labs and in field tests. The company projects that with the current rate of development, the technology can be made cost competitive with other renewable power sources such as bio and tidal power (< 0.05 €/kWh) when commercialized around 2010 to 2015.

The basics of osmotic power can be described as a technology that utilizes the power released when freshwater mixes with saltwater. Hence it is somewhat of a reverse process of desalination. Pressure retarded osmosis, or the PRO concept harnesses the energy in this process to run turbines.

As freshwater passes through a semi-permeable membrane to a saltwater chamber with limited volume, pressure will theoretically rise to a maximum of 26 bars. The operating pressure in a power plant will be in the range of 11 to 15 bars, an equivalent to a water head of 100 to 145 meters in a hydropower plant, generating about 1 MW/m3s freshwater.

Osmotic power plants can be designed for installation in a number of coastal sites. A sea level PRO power plant can be designed as a run-of-the-river hydropower plant, as it takes freshwater in from a river outlet. Another is a combined conventional SHP and membrane plant that is buried in appropriate geological sites near the coastline, utilizing gravity for extra pressure. Many other flexible applications are possible.

Osmotic power is highly efficient and can operate at full capacity for more than 7000 hours a year. As it is an environmentally safe technology that exploits natural power in an area that has not been fully explored yet, there is great potential in the future for expanding its use, especially in countries with narrow land mass or those that needs alternative renewable energy sources.

As a food for thought, in the aftermath of the recent tidal wave disaster and seasonal floods, it is hoped that sustainable coastal management and defenses can be combined with such technology to balance out maintenance costs with renewable energy production, providing a dual benefit for the often impoverished and vulnerable communities in coastal areas.

For more information regarding osmotic power, visit http://www.statcraft.com/