A first-of-its-kind facility has begun operations in Fukuoka, Japan, tapping the natural movement of water between freshwater and seawater to generate electricity around the clock. The plant, developed by the Fukuoka District Waterworks Agency and inaugurated on 5 August 2025, is the first commercial-scale osmotic power facility in Asia and only the second in the world. It is designed to produce approximately 880,000 kWh annually-enough to power around 220 average households-and will supply electricity to a local desalination unit.

The technology draws on a well-known physical process called osmosis in which water moves from a region of lower salt concentration to one of higher concentration through a semipermeable membrane. At this site, treated freshwater is placed on one side of the membrane and concentrated seawater-brine leftover from desalination-is placed on the other side. As freshwater flows across, it pressurises the saltwater side, driving a turbine that generates electricity without producing carbon dioxide at the point of generation.

Project leaders emphasise the major advantage of this type of renewable generation: unlike solar or wind, the system is not dependent on daylight or weather conditions, promising a stable supply of electricity day and night.“I feel overwhelmed that we have been able to put this into practical use. I hope it spreads not just in Japan, but across the world,” said Akihiko Tanioka, professor emeritus at the Institute of Science Tokyo, at the launch ceremony.

The Fukuoka installation builds on earlier work in Europe, most notably a commercial plant in Mariager, Denmark, which came online in 2023. While that plant demonstrated the concept at scale, Japan's version is larger and located at the Uminonakamichi Nata Seawater Desalination Centre, enabling close integration with existing water infrastructure. The use of brine feedstock increases the salinity differential and thus the energy yield per unit of membrane area.

However, experts caution that the technology still faces hurdles. One significant challenge is the energy required to pump both freshwater and seawater through the system and the friction losses across membranes, which reduce the net energy gain. Professor Sandra Kentish of the University of Melbourne notes that although water mixing releases energy,“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.” That is one reason osmotic power has remained a niche technology despite its appeal.

Membrane technology and pumping efficiency are advancing, with firms such as Toyobo developing hollow-fibre membranes tailored for osmotic generation and startups exploring nano-osmotic diffusion methods to improve selectivity and reduce losses. These developments raise the prospect of scaling the technology to larger coastal or estuarine sites. In Australia, for example, researchers at the University of Technology Sydney have prototypes that could be revived in salt-lake or estuary settings if funding and regulatory support align.

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