Residents of the Japanese coastal city of Fukuoka are pioneering the world’s first full-sized osmotic power plant — which generates electricity by mixing fresh water with saltwater. The plant, which opened on August 5, generates about 880,000 kilowatt-hours of electricity per year, enough to run a nearby desalination facility and supply about 220 nearby homes.
The concept of osmotic power is based on the principles of osmosis, the same process that helps plants draw water from soil and allows human cells to stay hydrated. Osmotic energy can be generated as water moves from areas with low salt concentration (fresh water) to areas with high salt concentration (seawater) through a special membrane.
To capture this “blue energy,” ions migrate from the saltier side to the less salty side of the membrane in pursuit of equilibrium. The movement of water and ions generates a pressure differential that can be harnessed to drive a turbine to produce electricity. To maximize the impact, the Japanese plant uses concentrated seawater — the brine left after removal of fresh water in the nearby desalination plant.
Osmotic power, now viewed by the World Economic Forum as one of the ten emerging technologies to watch in 2025, emerged in the 1970s in response to the first Earth Day.
The simple reason, as explained recently by Nicolas Heuzé, whose company Sweetch Energy is working to bring the technology to scale, is that “osmotic power is clean, completely natural, available 24 hours a day in all coastal zones, can be turned on almost instantly and modulated very easily.”
Kenji Hirokawa, director of the Seawater Desalination Center, which operates the Fukuoka plant, boasts that osmotic power produces no carbon dioxide and is completely renewable. Because oceans and seas are virtually boundless, and desalination is increasingly being relied upon for freshwater supplies, osmotic power is a stable source of electricity that can operate 24/7/365 – unlike wind and solar.
The first osmotic energy researchers were unable to design membranes efficient enough for effective ion exchange — a crucial process for net energy production. In 2009, Norway’s state-owned green energy company Statkraft launched an osmotic energy demonstrator; it ceased operations in 2013 due to concerns about economic viability and insufficient energy output.
In 2014, the Dutch company Redstack installed a demonstration plant that operates on a very small scale on a dike. But the first company to open a fully functioning osmotic power plant was the Danish venture firm SaltPower. The plant, located at Nobians saltworks in Mariager, Denmark, uses hollow-fiber forward osmosis (FO) membranes manufactured by the 150-year-old Japanese firm Toyobo Co., Ltd.
Toyobo, which began in 1882 as a cotton spinning operation, today manufactures, processes, and sells various products in the fields of film, life sciences, environmental and functional materials, and functional textiles. In the 1970s, Toyobo developed a hollow-fiber semi-permeable membrane that permeates water molecules — but not molecules and ions above a certain size — by applying a spinning technology the company had developed in its textile production business.
For years, Toyobo has sold the product to desalination plants as a reverse osmosis (RO) membrane for converting seawater into fresh water. Its RO membranes are currently used to produce about 1.6 million tons per day of fresh water, enough for about 6.4 million people.
The Toyobo membranes being used at the SaltPower facility have excellent pressure resistance and can operate under the high operating pressure required for efficient osmotic power generation and maintain high power generation efficiency.
At the Danish plant, concentrated saltwater is pumped from underground rock salt deposits after water is fed from aboveground into the salt layers via hydraulic pumps. The facility produces about 100 kilowatt-hours of power from mixing the near-saturated saltwater pumped from the saltworks with fresh water via the membrane.
SaltPower plans to actively promote osmotic power plants using Toyobo’s FO membranes at other sites across Europe — without the need for seawater. Saltworks using solution mining and the chlor alkali industry can benefit immediately. Osmotic power can also be used to generate energy when building salt caverns for seasonal storage for hydrogen.
Professor Sandra Kentish, a chemical engineer at the University of Melbourne, says the chief obstacle to osmotic energy’s commercial viability is that a lot of energy is lost in pumping the two streams (saltwater and freshwater) into the power plant and from the frictional loss across the membranes. Incremental gains have been achieved — and the Fukuoka plant will provide a true test of whether constant osmotic power is ready to compete with intermittent wind and solar.
Interest in osmotic power is growing. Besides the small Danish plant and the larger Japanese facility, pilot projects are under way in Norway, South Korea, Spain, and Qatar — though an Australian prototype plant at the University of Technology Sydney has not reopened since it was shuttered during the COVID pandemic.
At the launch of the Fukuoka facility, Akihiko Tanioka, professor emeritus at the Institute of Science Tokyo and a pioneer in the field, said, “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.”
With the heavy push from the World Economic Forum (WEF), funding for further research into making osmotic energy production more efficient is likely to increase. Such gains are not unprecedented, as exemplified by the auto industry’s successes in increasing engine efficiency.
Wherever fresh water meets saltwater (or wherever there are salt mines) there is potential for osmotic power. With growing worldwide demand for electric energy, osmotic energy could — if power losses can be brought lower — meet up to 15% of global energy demand by 2050, according to some estimates. That would make osmotic energy the largest untapped renewable resource on Earth.
Carbon-free. 24/7/365. No mining (salt mines excluded) involved. Available anywhere fresh water and saltwater meet. Works in conjunction with desalination plants. What’s not to like — at the right price?
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I guess anything that creates motion or heat can be used to generate electricity. The question is how much and at what cost?
Yes, for the entire system, what’s Energy Invested V Energy Returned?
In other words, is it as stupid as hydrogen, where, 52.5MWh of electrical energy are required to make 1 tonne of “green” hydrogen through the electrolysis of water . . . and then that 1 tonne of hydrogen will deliver 15MWh AT BEST!!
https://www.powermag.com/osmotic-power-from-the-ocean/
Theoretically you can get over 200 psi differential across the membrane…..unfortunately only enough fluid transport to result in .65 watts per square meter….so like many heat engine/power generator ideas, in this case the cost of osmotic membrane per square meter, rather than heat exchanger area cost/sq.meter results in a hard stop at the “money required” section of the funding application.
O. Levenspiel wrote about this in a very understandable paper in 1974 but the NIH site on which it resides is off-line due to present fed site funding shutdown.
Interesting. Might be viable for niche markets. Given the limited number of places where this can be applied, I doubt it will ever be more than a niche markets.
We’ll see whether it can make enough money to justify capital and maintenance costs.
The green energy enthusiasts are desperate to avoid anything that used the word “nuclear”. This thing looks just like another antinuclear propaganda stunt.
880,000KWh a year? One might also say it produces 100KW. Build 10,000 of it to replace one nuclear reactor, but ok..
The desalination facility nearby, on which it depends on for the high salinity water, consumes about a 100times more energy. So yes, the whole complex improved its energy efficiency by… 1%. Awesome!
I was confused at first by the idea of mixing fresh water from the desalination plant with the concentrated brine from the same plant; what kind of lousy perpetual motion machine have the greenies dreamt up now?
But I think what they’re doing is mixing the concentrated brine with ordinary seawater. I suppose it’s like recovering some heat energy from exhaust. Better than nothing, and it may matter in a prop fighter plane eking out a few more mph. But it sure doesn’t seem worthwhile for terrestrial power generation. Presumably it’s a demonstration plant, and they think the glamour will convince someone to give them more money for an industrial scale process.
Sure seems like a waste.
I thought they were mixing the brine with ordinary river water.
The only reason to have a desalination plant is to produce fresh water. Why the dickens would they throw away any fresh water like that, whether it came from a river or the desalination plant? That’s getting right back into perpetual motion country.
I have reread the article and it never mentions my idea of seawater and concentrated brine from the desalination plant. The very first paragraphs says so.
If they’ve got fresh water to generate the power, why not just ship that fresh water to that nearby location instead of building a desalination facility?
If the desalination facility was already there and they just wanted a new source of power, it would be cheaper to decommission the desalination facility and pipe the fresh water directly to its nearby customers.
The article makes no sense. I give up.
The article looks to be a press release. That means it tells us only what the marketing types want us to know. One unanswered question I think anyone who has spent much time in Japan would ask is why there would be a desalinization plant in Fukuoka. Japan in general is a very rainy place. Substantially wetter than places we Anglo-Europeans think of as wet like Seattle or London. Fukuoka gets roughly 1.6m (63in) of rain in an average year. It seems unlikely they have an ongoing fresh water shortage.
The internet isn’t entirely helpful, but it suggests that the local topography doesn’t allow for a lot of fresh water storage and the plant may have been built to provide fresh water during the (very?) occasional drought. see https://www.fukuoka-now.com/en/fukuoka-city-waterworks-to-celebrate-100-years/
I would point out that the ‘fresh’ water doesn’t need to be drinking water. It could, for example, be “gray” water from sewage treatment plants. And the brine doesn’t have to come from reverse osmosis desalinization plants. It could come from a solar or geothermal powered desalinization facility. Also some underground water is very saline.
So. As someone suggests above, maybe some real world niche applications.
That’s all I have time for. Need to water the plants and feed the dogs before they show up then sit and stare at me balefully accusing me of (yet again) ignoring their needs.
It is possible that the fresh water they are using is not potable for some other reason. It is all vague.
Typical RO system separates about 10% of the sea water into fresh water. The brine coming out is about 3.85 wt% instead of 3.5%. That is very little driving force to produce power.
You are mixing kWhrs with kW. So 880000/8760=1000kW or 1mw. It would take about 800 of these to displace one nuke.
I think your calculator is broken
You are a genius!
Err, no. You are off by a factor of 10. 880000 kWh in a year is a steady 100kW of power, or 0.1 MW. It would take about 10000 of these to match a typical nuclear plant.
But 880,000kWh (don’t look behind the curtain to see the time period) sounds much better than 100kW and that is the aim.
Baffle the crows with large, impressive numbers
Perhaps you have a typo. Should it not be 880,000 Wh (not kWh)?
I went back and reread the article. It does state 880,000 kWh.
I apologize for my error.
I don’t know about this. I thought the purpose of a desalination plant was to provide usable water to a population from sea water? It sounds like they are talking about using the desalinated water to produce energy instead of for the use by the population. What quantities of water are we talking about here? What happens to the fresh water that been turned back into salt water by osmosis? It sounds like the process is more efficient using water more salty than seawater. What kind of infrastructure is needed for the osmosis process? I don’t see this as a way to produce fresh water for a population and energy to boot.
They never specify where they are getting the fresh water from. It was my assumption that they were using something like well or river water.
This plant uses fresh water to produce power to make less fresh water than it used. What a green idea!
I note these statements:
“global energy demand” and “Available anywhere fresh water and saltwater meet.”
Is that just “electricity” demand? It doesn’t say.
“Anywhere” is not appropriate. Total continental coastline meets saltwater. Coastline is often occupied. See NYC’s “The Battery and east to the Brooklyn Bridge. Or not conducive, see Dover and the White Cliffs thereof. Or try Sagres on the Algarve Coast of Portugal.
About 10 years ago, or 15, wave and current projects were news makers.
One of the filters under my kitchen sink is osmotic, called “reverse osmosis” by one purveyor.
A source with an even lower energy density than wind.
Looks like another “green energy” pipe dream to me. Can it compete with wind and solar? Who cares? That’s like asking if a tortoise can compete with a snail.
What’s not to like? All of it!
This article is a “green” puff piece. It’s clear that the author is very naive and knows very little about science and technology.
This hyper-inefficient, freshwater-destroying, low-density energy-producing method is just another “green”, idiotic construction used to try to avoid the only realistic and rational power source, nuclear power.
That a Danish company is behind this is no surprise, as Denmark’s official religion is Climate Change with its religious symbol: the windmill.
While I fully agree, there is a different perspective needed.
We should be evaluating all of these concepts properly via Engineering and Scientific principles.
How knows when the next real discovery will be found?
I fully agree. Committing substantial economic resources to an unproven technology is sinful. We have seen this too many times. It is time for humanity to put on its big boy pants and start acting like adults.
“Look! Grasshoppers!” is not a valid way forward.
“Carbon-free. 24/7/365.”
Nice concept as a curiosity. But who cares about the “carbon free” part? Life on earth is all about carbon. Stop glamorizing the interesting but inefficient ways to produce electricity. This is similar to tidal energy. Sounds great, until you realize the problems of capital cost and scale.
A related point: If you have fresh water in your possession or under your control, from which to make drinking water or to supply irrigation systems, why would you want to degrade it back to a condition unsuitable for those uses?
I should add, “This is similar to tidal energy and wave energy.”
I remember that. I think they actually tried it once. It looked better on paper than in reality.
How about scalability? 880,000 kWH per year is about 58 KW steady output. At best this will make a slight reduction in the power required to run the necessary desalination plant. For comparison, a single server rack in an AI-focused data center requires 30-60 KW.
880,000 kWH sounds like a lot, but if I take the “energy charge” at the highest tier plus the “fuel charge” from my latest Georgia Power bill, they come to $0.1889 / kWH, so the total retail value of the power produced annually by this plant is $166,272. This isn’t enough to cover the fully-burdened cost of a single US-based engineering-class employee, let alone all the other operating and capital costs.
In addition the whole point of a desal plant is to produce fresh water, some of which is then made salty again by migrating through the osmotic membrane. You have to take the capital and operating costs of the osmotic power plant and add to that the lost value of the fresh water.
Alan Watt: Good point. A quick search provides a good overview of the process involved and seems to be real. However, like many “green energy” schemes this one looks economically untenable. Just another brewing boondoggle like green hydrogen, direct air carbon capture and bio-diesel. Another opportunity for subsidy mining.
so dumping fresh water into sea water can run a machine separating freshwater from sea water.
sounds legit
Every time a river empties into a sea or ocean, there’s heat given off. That’s the vapour you see rising at the mouth of a river. That’s the heat being given off by this chemical reaction.
However, the energy being produced is far too diffuse to be useful in any way. This is simply a grift by Sweetch Energy looking for donors/investors/suckers for another bogus “green” energy delusion.
I live less than a kilometer from a river delta, where fresh water pours into seawater and I have never seen the slightest evidence of heat being emitted there.
Run raw river water through an RO membrane?
It won’t last long without some type of pretreatment.
Add the cost of a water treatment plant and it’s operation to the process.
I can see how this works. Salt water evaporates using solar radiation and the water vapour condenses to pure water. Then this pure water is used together with the concentrate brine to recover the original energy that came from solar radiation.
Now, how does this process compare with other ways of collecting and storing and delivering renewable energy? Not too well I suspect.
The principle of conserving fossil fuels, in particular oil which is an essential ingredient for the entire petrochemical industry is easy to accept. Coal is more abundant and inherently suitable for static power generation. By what democratic process was coal cancelled?
Oh, in China they did not cancel coal.
Given the shortage of clean water, where does it come from? How much fresh water does it take?
At the Danish plant, concentrated saltwater is pumped from underground rock salt deposits after water is fed from aboveground into the salt layers via hydraulic pumps. The facility produces about 100 kilowatt-hours of power from mixing the near-saturated saltwater pumped from the saltworks with fresh water via the membrane.
kilowatt hours = energy
kilowatts = power
If the writer can’t get that right why should I trust that anything else in the article is right?
Seconded, I can get about 100MW from a capacitor for about a microsecond but MWh is rather less! Basis of spot welding.
I’m struggling with it producing electricity to power the nearby desalination plant which supplies it with the brine to provide the power to provide the brine to provide the power to produce the brine which … my head aches.. and has some left over to power nearby homes – proving energy can be created.
Sound too much like Perpetual Motion.
Re: The Danish salt plant. Pumping water into a subterranean salt body seems like a good way to create a future sink-hole disaster.
Can you spot the basic physics scam that is involved with “osmotic power” as discussed in the above article?
This: nowhere is there mention of the power consumed in performing the desalinization of sea water (to obtain the needed fresh water for the process) compared to the power produced by subsequently allowing that freshwater to mix with concentrated salt water across the osmotic membrane.
The Second Law of Thermodynamics . . . you know, the one that describes entropy . . . says that more power will be consumed than that which is generated. Otherwise, one has the basis for an infinite energy-producing scheme.
Finally, why am I not at all surprised that the World Economic Forum would view this farce as “one of the ten emerging technologies to watch in 2025“.
Why not just build a dam for the freshwater to produce the hydro power to power the desalination plant to eat the spider that the lady swallowed to eat the bug … I forget how the rest of it goes.
(But I do remember it has no connection to reality.)
I don’t know why she swallowed the fly. Perhaps she’ll die?
Must you spoil the fun? At this point it would take but a little push, and the clowns would trumpet their great new solution to the solar panels not working at night: floodlights.
The brochure from a Danish firm, a leader in osmosis electricity, stoutly tells us the 200 bar osmotic pressure is the equivalent to a 2 km height for an hydroelectric dam. 200 bar does correspond to the pressure at the bottom of a column of water 2km deep.
That statement is totally irrelevant and is disinformation – misinformation.
The osmotic process in use is a form of energy scavenging, much less effective than burning garbage which yields only a few percent compared to burning coal, and far worse pollutants. Scavengers are tertiary energy consumers or producers. The articles strictly avoid an EROI or FCOE analysis.
So it sounds like electricity is used from another source to convert sea water into fresh water by reverse osmosis. Then fresh water is allowed to diffuse through another membrane back into the brine, recovering some energy. If you have a source of fresh water to do this, why do you need to have an RO plant in the first place? The forward osmosis will always be less efficient than the original reverse osmosis due to the second law of thermodynamics. I suppose if you had an abundant and free source of fresh water from a large river and a source of brine, you could generate some energy. However, this clearly cannot be efficient or economical. What a con.