On a humid morning in Fukuoka, a coastal city in southern Japan, a new kind of power came online. Japan has launched Asia’s first osmotic power plant, which generates electricity by mixing fresh water with salt water.
“It’s a meaningful plan—the start of a plan, perhaps—in our response against climate change,” said Kenji Hirokawa, director of the Seawater Desalination Center, which runs the facility, as per Gizmodo.
Fukuoka’s plant is only the second of its kind worldwide, following one in Denmark that opened in 2023. Japan’s version is larger and marks a step forward for this little-used but promising renewable energy source.
The plant will generate about 880,000 kilowatt hours of electricity per year—enough to help run a nearby desalination facility and supply around 220 homes. That equals the output of two soccer fields of solar panels, but osmotic power keeps running day and night, in any weather.
Osmosis is the same process that helps plants draw water from soil and allows our cells to stay hydrated. Put simply, it’s the movement of water from areas with low salt concentration (like fresh water) to areas with high salt concentration (like seawater) through a special membrane.
Osmotic power plants put this passive movement to work.
Fresh water—or treated wastewater—is placed on one side of a membrane. On the other side is seawater, made even saltier by concentrating leftover brine from a desalination process. The difference in saltiness pulls the fresh water across the membrane, increasing the pressure on the saltwater side. That pressure is then used to drive a turbine, generating electricity.
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