BY THE OPTIMIST DAILY EDITORIAL TEAM
Fukuoka, Japan, has quietly switched on a facility that could point to the future of renewable energy. The country’s first osmotic power plant (and only the second in the world) will generate roughly 880,000 kilowatt hours of electricity annually. That electricity will support the city’s desalination plant, keeping fresh water flowing to households across the region. As Dr. Ali Altaee of the University of Technology Sydney explained, that amount is “the equivalent of powering about 220 Japanese households.”
While the numbers sound small, the concept behind them is powerful: osmotic power can run continuously, day and night. Unlike solar and wind, it doesn’t rely on weather or daylight. It simply needs fresh water to meet salt water.
The science behind the current
Osmosis is a natural balancing act. Water moves through a membrane from a low-salt solution to a high-salt one, seeking equilibrium. Osmotic power plants put this to work: freshwater and seawater sit on opposite sides of a membrane, the seawater is lightly pressurized, and the movement of water increases pressure. That pressure drives a turbine, producing electricity. In Fukuoka, treated wastewater can also be used as a freshwater source, paired with seawater to turn the turbine.
A global experiment
Japan joins Denmark as one of two countries with working osmotic power stations. The first was built in 2023 in Mariager by the company SaltPower. According to University of Melbourne professor Sandra Kentish, Fukuoka’s facility is larger, though both plants operate at similar capacity. Elsewhere, pilot projects have taken shape in Norway and South Korea, while Altaee has worked on prototypes in Spain, Qatar, and Sydney. The Australian project lost momentum during the pandemic, but he says the expertise is still there to restart.
Why it’s hard to scale
Turning osmosis into practical power is more complex than the theory suggests. “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,” Kentish explained. “This means that the net energy that can be gained is small.”
But there is progress. Advances in pump and membrane design are steadily cutting down energy losses. Fukuoka’s plant also demonstrates a smart twist: it uses concentrated seawater left over from desalination. That brine makes the difference in salt levels greater, which boosts the energy potential.
Looking toward the future
Researchers see the Japanese launch as a turning point. “Communities have salt lakes around New South Wales and Sydney that could be used as a resource,” Altaee said, pointing out that Australia already has the know-how to build its own facility if funding becomes available. The UTS prototype could be revived to match the scale of Japan’s progress.
For now, Fukuoka’s contribution is modest. But as proof of concept, it matters. Osmotic power is one of the few renewable sources capable of running nonstop; no sun, no wind, no seasonal variation required. With every prototype and plant, the technology edges closer to becoming part of the world’s clean energy mix.
A quick refresher: how osmotic power works in 3 steps
- Two waters meet
Fresh water (or treated wastewater) and seawater are placed on opposite sides of a semipermeable membrane. - Water flows across
Fresh water naturally moves toward the salty side, boosting pressure in the concentrated solution. - Power is generated
That pressure is channeled through a turbine linked to a generator, producing steady renewable electricity.
