Japan has opened the world’s second osmotic power plant, using an age-old method to produce clean energy. If successful, it could establish the blueprint for other countries to establish their own facilities and gradually develop the largely unheard-of industry. This shows promise for companies looking to decarbonise operations, as investment in alternative forms of clean energy could help to cut emissions.
Japan launched its plant in August in the south-western city of Fukuoka. The facility is expected to produce roughly 880,000 kilowatt hours of electricity each year, which is enough to help power the associated desalination plant, which supplies fresh water to the city and surrounding areas. It produces enough energy to power the equivalent of 220 Japanese households. While the plant is relatively small compared to alternative energy-producing facilities, it could be scaled up in the future if successful.
The plant uses the osmosis method, a process by which molecules of a solvent pass through a semipermeable membrane from a less concentrated solution into a more concentrated one, which balances the concentration on both sides. Salt water and fresh water are put on either side of a membrane, with the seawater being slightly pressurised. As water flows through the membrane to the saltier side, it boosts the volume of pressurised solution to be harnessed to produce energy.
While wind and solar power production can only take place when the sun is shining or the wind is blowing, osmotic technology can be used to produce energy at all hours of the day and night, requiring just the mix of fresh and salt water to work. In Japan’s new plant, fresh water or treated wastewater is placed on one side of a membrane, and seawater is on the other side. The seawater gradually increases in pressure and decreases in salinity, allowing excess water to run through a turbine that is connected to a generator to produce power.
This is only the second Osmotic Power Plant globally, the other of which was developed in Mariager, Denmark, in 2023 by the venture company SaltPower. The Fukuoka plant is bigger than that of Mariager, although they use similar methods. Norway, South Korea, Spain, and Qatar have also trialled the technology.
While it shows promise on a small scale, scaling up the technology is more complicated, as a significant quantity of energy is lost as the water is pumped into the power plant and as it flows through the membranes. “While energy is released when the salt water is mixed with fresh water, a lot of energy is lost in pumping the two streams into the power plant and from the frictional loss across the membranes. This means that the net energy that can be gained is small,” Sandra Kentish, a professor from the University of Melbourne, explained.
Nevertheless, the new plant shows how investment in alternative clean energy techniques can provide power, particularly for small-scale facilities that might otherwise rely on fossil fuels.
The project builds on Japan’s existing expertise in waterpower, with several hydroelectric and tidal power plants across the country. In 2024, hydropower contributed roughly 14 percent of Japan’s total power generation capacity, while in 2023 it accounted for 8 percent of its total power generation. Japan plans to expand its hydropower sector in the coming decades in line with plans for a green transition, with a CAGR of around 0.01 percent between 2023 and 2035.
In March, the governments of Indonesia and Japan announced plans to partner on the development of Southeast Asia’s largest hydropower plant in Indonesia, with the signing of a letter of intent. The project is expected to cost $17.8 billion and will help support regional decarbonisation aims, as well as strengthen energy cooperation between the two countries. Japan will use its industry expertise to advise and could gain valuable experience to further develop its own hydropower sector.
Earlier this year, the U.K.-based tidal energy company Proteus Marine Renewables (PMR) installed a 1.1 MW tidal turbine in Japan’s Naru Strait, which is expected to help decarbonise the electricity supply of the Goto Islands. This followed a successful 2021 pilot project in the region.
Philip Archer, the Managing Director of Proteus Operations Japan, stated, “The result reinforces tidal energy’s potential as a dependable renewable source in Japan. Our next immediate focus is the commissioning of the turbine, Japan’s first ever MW-scale grid-connected tidal system, and the subsequent testing and accreditation phase.”
While several of Japan’s water-related energy-producing operations are in the nascent stage of development, they show that the East Asian country is dedicated to investing in alternative clean energy projects and trialling new technologies. This could help Japan to develop a highly diversified clean energy mix, rather than relying on conventional renewable energy sources, such as solar and wind.
By Felicity Bradstock for Oilprice.com
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