Japan’s first osmotic power plant in Fukuoka

August 25, 2025

Japan has officially unveiled its first osmotic power plant in the southwestern city of Fukuoka, marking a major step forward in renewable energy innovation. This facility is only the second osmotic power station in the world, and it is projected to generate approximately 880,000 kilowatt-hours of electricity annually.

That amount of energy is enough to help run a nearby desalination plant, providing fresh water to Fukuoka and surrounding regions. In practical terms, it could supply power equivalent to about 220 average Japanese households, according to Dr. Ali Altaee from the University of Technology Sydney (UTS), an expert in sustainable water and energy systems.

Unlike wind or solar, osmotic energy has a unique advantage: it delivers continuous, round-the-clock power, independent of weather or daylight. By simply harnessing the natural interaction of fresh water and salt water, osmotic power offers a stable and predictable renewable energy source.

What is osmotic power?

Osmotic power, also known as salinity gradient energy, is based on the natural process of osmosis. Osmosis occurs when water flows across a semi-permeable membrane from a low-salinity solution (such as freshwater) into a high-salinity solution (such as seawater) in order to equalize concentration levels.

In osmotic power plants, this principle is applied on a large scale:

Fresh water and seawater are placed on opposite sides of a special membrane.

The seawater side is slightly pressurized.

As fresh water moves toward the saltier side, it increases the pressure.

This pressurized flow drives a turbine connected to a generator, producing electricity.

At the Fukuoka facility, engineers use freshwater or treated wastewater alongside seawater. The system then channels the pressurized flow through turbines to generate clean power.

Where else Is osmotic power being used?

The Fukuoka project is only the second full-scale osmotic power plant in the world. The first was launched in 2023 in Mariager, Denmark, by the clean-tech company SaltPower.

While Japan’s facility is physically larger, both plants operate at similar capacities. Other pilot projects have also been tested in Norway and South Korea, with additional prototypes developed in Spain, Qatar, and Australia.

Dr. Altaee noted that UTS in Sydney had developed its own prototype, though momentum slowed during the Covid-19 pandemic. With renewed government support, the technology could be restarted and scaled further in Australia.

Key challenges in osmotic power

Despite its promise, osmotic energy still faces technical and efficiency challenges:

Energy losses occur when pumping fresh and salt water into the system.

Friction in membranes reduces the net output.

According to Professor Sandra Kentish from the University of Melbourne, these issues make large-scale production complex. However, she notes that advances in membrane efficiency and pump technology are rapidly reducing energy losses.

Importantly, Japan’s Fukuoka facility leverages concentrated seawater brine, a byproduct of desalination. By using brine instead of standard seawater, the plant creates a stronger salinity difference, which boosts overall energy output.

What does the future hold?

Experts see Japan’s osmotic power plant as a landmark achievement that demonstrates the technology’s real-world potential. As improvements in materials, membranes, and scaling methods continue, osmotic energy could become a valuable addition to the global renewable energy mix.

Dr. Altaee emphasizes that Australia also holds significant potential, with its salt lakes and technical expertise. With proper investment and policy support, osmotic plants similar to Fukuoka’s could one day power parts of Sydney and New South Wales, contributing to a cleaner, more resilient energy grid.