Japan just became the second country in the world to launch a commercial-scale osmotic energy plant, a big win for the little-known form of clean energy generation that first broke ground in Denmark. While osmotic energy is nascent and its testing grounds remain limited, it has big potential – The World Economic Forum recently named osmotic power systems as one of the top 10 emerging technologies to watch in 2025.
This form of carbon-free energy generation uses osmosis between freshwater and saltwater to create power. In other words, it works by moving water from a less concentrated solution to a more concentrated one across a semipermeable membrane. “When freshwater and seawater meet, a natural gradient in salinity is created, prompting ions to migrate from the saltier side to the less salty side in pursuit of equilibrium,” an Earth.org article explains in layman’s terms. “The movement of water and ions generates a pressure differential that can be harnessed to produce electricity.”
The result is a baseload form of totally clean and carbon-free energy production that is available 24 hours a day, seven days a week, 365 days a year. This is critical for energy security, as the majority of clean energy capacity, namely wind and solar, is variable. This means that osmotic energy could be an excellent alternative clean power from an energy security perspective.
Denmark brought the world’s first commercial-scale osmotic power plant online in 2023. This month, Japan followed suit with a brand new plant in Fukuoka. The plant began operations on August 5, and will produce 880,000 kilowatt-hours a year. The plant was developed in tandem with a local desalination plant. The use of extra-salinated water leftover from the desalination process lends itself perfectly to the osmosis model by increasing efficiency while also reducing waste. “Those stronger gradients boost efficiency and grounds osmotic generation in existing systems rather than the lab,” reports New Atlas.
“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,” Akihiko Tanioka, professor emeritus at the Institute of Science Tokyo, told Kyodo News.
Pilot-scale osmotic energy models have already been developed in other nations around the world including Norway, France, and South Korea. Other coastal nations will likely soon follow suit as Denmark and Japan demonstrate the utility of their own plants. Proponents believe that the benefits of the nascent sector will speak for themselves.
“Osmotic power is clean, completely natural, available 24 hours a day in all coastal areas, can be turned on almost instantly and modulated very easily,” Nicolas Heuzé, co-founder of osmotic energy firm Sweetch Energy, told the World Economic Forum.
If and when osmotic energy takes off, its productive potential would be enormous. Almost 30,000 TWh of osmotic energy is naturally released by deltas and estuaries each and every year – it just needs to be harnessed. The Dubai Future Foundation calculates that osmotic systems could eventually produce approximately 5,177 terawatt-hours (TWh) annually – that’s almost a fifth of global electricity needs.
However, scaling the technology can be difficult due to low energy efficiency. While the Japanese plant gets a relatively high energy output thanks to the concentrated brine it sources from its associated desalination plant, models elsewhere can’t necessarily expect the same level of performance. But in places where the technology makes sense, the potential is significant.
“Globally, and particularly in salt-rich areas like Australia and the Middle East, where access to brackish or seawater exceeds access to freshwater, these power systems hold huge potential for baseload energy and clean water production,” Dr. Katherine Daniell, Director of the Australian National University’s School of Cybernetics, was quoted by the World Economic Forum.
By Haley Zaremba for Oilprice.com
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