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Japan has opened its first osmotic power plant in Fukuoka city, harnessing the natural mixing of saltwater and freshwater to generate clean energy
In early August, Japan quietly marked a major milestone in renewable energy: it opened Asia’s first osmotic power plant in Fukuoka City. (Representative Image/Unsplash)
In early August, Japan quietly marked a major milestone in renewable energy: it opened Asia’s first osmotic power plant in Fukuoka City. According to the Fukuoka District Waterworks Agency, the facility began operations on August 5, and it’s designed to generate 880,000 kilowatt-hours (kWh) of electricity annually, enough to power about 220 Japanese households or support a desalination plant that provides clean water to the region.
This makes it only the second operational plant in the world using this method. The first was launched by Denmark’s SaltPower company in 2023.
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But what’s unusual is the source of power: the natural interaction between saltwater and freshwater, a phenomenon driven by a process known as osmosis.
What Is Osmosis And How Does It Power This Plant?
Also known as salinity-gradient power or blue energy, osmotic power taps into the natural movement of water molecules. It works on the principle of osmosis, something as old as life itself.
Here’s the basic idea: Imagine two containers, one with freshwater and one with saltwater, separated by a special semipermeable membrane. Water naturally moves from the freshwater side to the saltier side, in an attempt to balance the concentration. This movement builds pressure, which can be harnessed to spin a turbine and generate electricity.
In Fukuoka’s case, the plant uses treated wastewater on one side and concentrated seawater brine (a by-product of desalination) on the other. This increases the difference in salt content, called the salinity gradient, and boosts the energy potential.
The setup is compact and clean. There are no emissions at the point of generation, and unlike wind or solar, the system runs continuously, regardless of weather or time of day.
Why Is This A Big Deal?
What sets osmotic power apart is its ability to provide predictable, round-the-clock energy. While wind and solar are highly weather-dependent, osmotic plants can run 24/7 as long as freshwater and saltwater are available.
The Fukuoka Waterworks Agency called it a “next-generation renewable energy source” that avoids both carbon emissions and intermittency problems faced by traditional green technologies.
Akihiko Tanioka, professor emeritus at the Institute of Science Tokyo and a long-time proponent of osmotic power, told Kyodo News: “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.”
When Was This Idea First Proposed?
Osmotic power may sound futuristic, but it’s not new.
Back in 1954, British researcher RE Pattle suggested that mixing freshwater and seawater could release usable energy. In the 1970s, Professor Sidney Loeb, co-inventor of reverse osmosis desalination, formalised a method called pressure-retarded osmosis (PRO) after observing the Jordan River flowing into the Dead Sea.
Since then, prototypes have been tested in Norway, South Korea, Spain, Qatar, and Australia, but none advanced beyond pilot stages due to technical limitations and cost issues.
The real breakthrough came in 2023, when Denmark’s SaltPower launched the first commercial-scale plant in Mariager. That facility used hollow-fibre forward-osmosis membranes developed by Toyobo, a Japanese firm, to overcome the biggest hurdle: membrane efficiency.
What Are The Technical Challenges?
Despite its promise, osmotic power isn’t perfect.
The biggest problem is energy loss. As Professor Sandra Kentish from the University of Melbourne told The Guardian: “While energy is released when 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 the net energy that can be gained is small.”
In simple terms, you lose power while trying to create it, through pumps, membrane resistance, and fluid drag.
Moreover, maintaining large, high-pressure membranes that allow only water molecules through, while rejecting salts and impurities, is a technical and financial challenge. This is one reason osmotic power is still far behind solar and wind in terms of cost competitiveness.
Still, experts say things are improving. The use of brine from desalination, saltier than regular seawater, boosts the gradient and improves output. Fukuoka’s plant smartly capitalises on this.
What’s The Global Potential And Who Else Is Exploring It?
While Japan and Denmark are the only countries with full-scale facilities, the technology is under active research elsewhere.
Dr Ali Altaee of the University of Technology Sydney, who helped develop prototypes in Australia, Spain, and Qatar, said Japan’s success is encouraging. He told The Guardian: “The Japanese plant is larger than the one in Denmark… It demonstrates real potential for scale.”
Altaee believes Australia’s salt lakes in New South Wales and other regions could host similar systems, if public funding is made available.
In France, a startup called Sweetch Energy is experimenting with Ionic Nano Osmotic Diffusion (INOD), a membrane technology using bio-sourced raw materials that may reduce energy loss and improve viability.
What Does This Mean for Japan’s Energy Mix?
The Fukuoka project may be small in scale (with just 110 kW of net capacity, as per IFL Science), but it’s symbolic for a country that still relies heavily on fossil fuels.
According to The Independent, Japan derived about 73 per cent of its electricity from coal, gas, and oil in 2022, with renewables—mainly solar and hydro—accounting for just 20 per cent. The government aims to raise that to 36–38 per cent by 2030.
As a country with limited natural resources, high energy imports, and a push to diversify post-Fukushima, Japan sees osmotic power as part of a longer-term clean energy puzzle.
Is Osmotic Energy The Future?
Not just yet, but it could be.
While current plants like Fukuoka are small, the science is sound and the technology is maturing. Experts like Professor Kentish believe that with better membranes and smarter pumping systems, osmotic energy could move closer to commercial feasibility.
Some estimates, as cited by IFL Science, suggest that if the hurdles are overcome, osmotic energy could fulfill up to 15 per cent of the world’s electricity demand by 2050.
That’s a big “if”, but in a world rapidly weaning itself off fossil fuels, every clean option counts.
About the Author
Karishma Jain, Chief Sub Editor at News18.com, writes and edits opinion pieces on a variety of subjects, including Indian politics and policy, culture and the arts, technology and social change. Follow her @kar…Read More
Karishma Jain, Chief Sub Editor at News18.com, writes and edits opinion pieces on a variety of subjects, including Indian politics and policy, culture and the arts, technology and social change. Follow her @kar… Read More
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