Scientists and engineers from the water supply company of Fukuoka city (Japan) launched an osmotic power plant with annual output of 880,000 KW*h — enough for covering the needs of desalination plant supplying potable water to the city and adjacent communities.
Osmotic power plants represent a new generation of renewable energy sources. This is the first facility of such type in Japan and the second one in the world: a similar power plant was opened in Denmark in 2023.
The main feature of this technology from wind and solar generation is that the energy source is available round-the-clock irrespective of the weather. Osmosis is a natural process when water is going through the semi-permeable membrane from the less saline solution to the more saline brine equalizing the concentration. This flow creates the pressure, which may be converted into electricity.
At the Fukuoka power plant fresh water (or treated effluents) is supplied to one side of the membrane, and sea water is supplied to the other side. The water tends to pass to the saline side and increases the pressure, the generated flow rotates the turbine connected with the generator.
The developers were facing a number of serious engineering challenges. At the early stages of the research the efficiency of such plants went down due to big losses of energy during pumping water and its coming through the membranes. Modern materials and new energy-efficient pumps allowed for minimizing such losses.
Another important solution was using not ordinary sea water for creating saline environment, but concentrated brine — a side product of desalination plants. Due to this the difference in concentration grows, hence, the amount of the generated energy is higher.
The Fukuoka osmotic power plant is capable of generating energy enough to cover the needs of approximately 220 households.
So far, such type of resumable energy is a niche area in the industry. However, launching the plant in Japan demonstrated that this technology is moving out from the experimental area and is claiming to become a commercially used one.
If it will reach the scale of application comparable to other RES, it will provide for another stable and environmentally clean way of receiving power. Similar projects were already tested in Norway, South Korea and Australia, where they are looking into the possibility of using the saline lakes of New South Wales.
This technology has especially high potential for coastal cities, where desalination plants are already in operation: in this case, water treatment and power generation may be integrated into a single system.
