JemmyJapan has opened its first osmotic power plant – so what is it and how does it work?
Aatubewww.theguardian.com/world/2025/aug/25/japan-osm…
The site in Fukuoka is only the second power plant of its type in the world, harnessing the power of osmosis to run a desalination plant in the city
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Combine salt and water to create electricity to power a desalination plant that removes salt from water. I am sure there is more to it, but the article sounds like it’s one of those mad perpetual free energy schemes that defy the laws of physics.
They are just re-capturing some of the energy the system spent turning salt water into fresh. Because that results in extremely salty brine water waste, you can get some energy as it gets diluted back down to sea water concentration.
There no “new” energy in the system, it’s just wasting less.
If they're mostly using electricity or even combustion to evaporate the water (as opposed to sunlight), there's no chance that the concentrated saltwater creates more electricity than it costs - it's only maybe useful if the saltwater is actually a waste product.
They're using brine from a reverse osmosis plans and wastewater, so yes, that is indeed the case.
Far cry from "perpetual free energy scheme", though.
I don't think anyone claimed it was.
Isn’t efficiency just getting closer and closer to a perpetual machine? Using science and the physics to the absolute limit!
So, they're using brine from a reverse osmosis plant and wastewater to run this process, both waste products, and probably producing something roughly the same as seawater.
Sounds bizarre, but apparently it works.
The reason being that dumping the brine back into the ocean creates a dead zone wherever that dump point is, since the relative concentration of salts is higher compared to regular seawater.
They’re almost certainly recreating seawater just to help alleviate the dead zone effect and figured out how to get some free electricity out of it too
porksnortRight. It seems analogous to regenerative braking in a gas/electric hybrid car. The momentum is turned back into electricity to reclaim potential energy. Some of the energy was already spent in RO stage and this process gets some of it back.
I sounds more like it makes electricity out of fresh water, destroying it in the process (turning it into saltwater through osmosis/dilution). Sure… if there is some crazy salty water you have, and want to turn it into “still salty, but maybe less so”, you can indeed gather a tiny little fraction of the power.
But given that fresh water is also a precious resource in many places, this seems relatively niche.
From what the article says, it's actually a pretty cool way of improving desalination plants. They use the left over brine, from desalination, that has a very high concentration of salt, and use it as the high salt concentration side, with regular seawater being used on the other side. This both gives them free energy and reduces the side effects of pumping that extremely salty water into the sea by diluting it.
As desalination plant need a lot of power it is a plus. But there is always that question in background with this approach what are they gonna do with this salt ?
It's pretty common to produce table salt by dehydrating sea water. This saltwater electricity plant doesn't produce salt, though, since the basis of their electricity generation process is diluting concentrated salt water.
I swear, nobody in this comment section actually understood the article.
To my knowledge, desalination plants do not recover salt from brine. There is a European project that is studying this feasibility. Generally, brines are discharged into the sea, which is destructive for the environment due to their concentration.
NaichRight. So it's 100kW output, which is almost enough to pull the skin off a rice pudding. It also uses the brine from a desalination plant, so it's basically salinating fresh water to get some of the power back that was taken to desalinate it.
As a means of power production, it seems a bit pointless.
It generates 880.000kWh/year, where I live that enough for 180 families (2 adults, 2 kids) with an average consumption in a house, and almost 350 in apartments. That's not an insignificant amount IMO.
Doesn't sound all that economical compared with other energy sources. It probably needs to be compared to longer-term energy storage solutions that don't rely on geography like hot sand, the possibility to store the energy source (concentrated salt water) relatively cheaply is the most interesting part about it.
The upside is getting power from an otherwise waste-product. Yes it's low output compared with traditional turbine-driven power plants, but that doesn't mean in should be disregarded. Sure it's not applicable everywhere, but neither is hydro or geothermal. After all, why not use the geography of your location to your benefit? Not everywhere needs to get power in the exact same way, and what's most feasible is highly dependent on location.
Concentrated salt water might be a waste product, but the plant was built on purpose. How long does it need to operate before the costs amortisize? Even if we're looking at greenhouse gases, most building materials aren't exactly climate-friendly.
The people who designed built the plant probably calculated all this, but the article doesn't go into it and with novel technologies like this, it's generally not safe to just assume that a given plant makes any economical or environmental sense.
HumaniusWhile I agree that the cost of operation and yield are a valid concern, the same argument could have been used against renewable energies like wind and solar only 30 to 40 years ago.
The price of these energy sources has come down a lot since, for a large part thanks to the modern day widespread use. We have a lot of experience generating power this way which drives down cost, and increases yield.
Novel techniques like the one described in the article don't yet benefit from that experience and scale. And if we don't try new things every now and then they never will.
That is not to say all novel techniques will be equally fruitful, but if you don't occasionally try new things you will never learn.
Edit: Misspelled "energy" as "energie"
It’s a pop science article… they usually don’t cover things like life cycle analysis. It is however a first of its kind plant that makes its net effects less important as it kind of works as a proof of concept. It’s a relatively small scale plant that if it does work, great, lets build more of them; if it doesn’t work, that sucks, can we modify them in any way to make them work.
It is taking two ingredients that usually have to take extra energy to be able to dispose of them and combining them together to make electricity. That is really cool, and there is no reason to be overly negative about it because it might be bad based on info that you don’t have
This plant is part of a bigger chain. So while yes, on its own it seems waste of effort, as part of the entire chain it's a reasonable step to be more environmentally friendly and recover some energy in the process.
A local plant desalinates water, resulting in fresh water and a brine solution that has much higher concentration of salt in it than regular sea water.
Dumping the brine solution on its own would kill most plant and animal life around the dump site due to large saltwater concentration, so an alternative method must be found to dispose of the brine.
Waste water from other processes can be mixed with the brine to bring it more in line with seawater salinity, making it safe to reintroduce to the ocean without severe ecological impact. This waste water is deemed to difficult or intensive to purify and treat to bring it back up clean water standards, and I'm assuming tested or filtered so as not to introduce hazardous chemicals that could damage the reverse osmosis membranes as well as sea life.
Because there is way to mix the waste water and brine through membranes that can be used to generate electricity, this process is utilized to recover some of the energy expended in purifing the original batch of seawater resulting in the brine.
It's not a perfect process but it is a means of getting some use out a waste product, similar to burning garbage or rotting food rather than just dumping it into a pit and letting it rot and release methane.
Its miles better than traditional desalination - requiring so much energy that burning fossil fuels is unavoidable. And brine is chucked back in the ocean. Basically an environmental catastrophe.
If you think of it on the scale of one community - providing potable water, dealing with treated wastewater AND getting a surplus of energy while treating the brine it is actually pretty clever.
If it makes you feel better you could probably slap some solar panels on those flat roofs too.
x4740NHere before the idiots who comment misinformation about Japan show up
Seems like a good pair for desalination plants, great to see the technology develop.
I did not quite get how it's a good idea tbh. They need freshwater to dilute the saltwater/brine. And they use it to separate the brine from saltwater to make freshwater? That's definitely an energy negative cycle. So what's the benefit? Is this more energy efficient then cleaning waste water into freshwater?
It's easier to understand with a picture of the process:
It's not energy negative. Freshwater and saltwater are freely available. Using the concentrated brine from a desalination plant only increases the efficiency.
I mean the part in the picture is clear to me. But if we assume freshwater is freely available, why would they want to power a desalination plant with the generated power? Basically you can trade freshwater (or salinity gradient generally) for power or power for freshwater. But in a simple loop you'd only lose both over time due to inefficiency.
From the article:
I understood it as using water not suited for household use (+ sea water) to power a plant that can create fresh water for the community?
There would be an option run desalination on solar, and osmosis generator is a base load source. So I would imagine that energy storage made out of waste product could be a potential good investment.
Right now those are pilot programmes that discover viability of those new technologies.
Even if solar/nuclear is better it's good thing to investigate those things as in right circumstances even ski gondola can be good public transport system (La Paz)
Definitely not shitting on the tech, it's a really cool concept and definitely useful. I just wish news outlets would have asked how the cycle is beneficial. I don't doubt that it is, but I don't get it.
doesn't completely answer your question, but:
so it would seem it happens to be a net positive due to the energy "stored" in the brine
Hm from reading more on it, I think it has more to do with droughts in the area. That is why they build the desalination plant in the first place. I assume using the residual energy of the saline gradient (+ the boost from the brine) to generate new freshwater is better than further draining the naturally occuring freshwater. But still just a guess.
I don't know, so I can only guess.
The desalination plant could have been there already, because for whatever reason it was more practical (or even required) than taking the water from the river.
Or maybe the desalination plant requires very little power, maybe less than what the osmotic plant produces.
Or the whole thing is indeed energy negative, but not as energy negative as having just the desalination plant. So at least they get to use the brine from the desalination to recoup some of the energy. Because the osmotic plant is power positive.
Something stinks here and it’s not the treated sewage.
I think the idea is that if you have an unlimited supply of treated waste water, and a limited supply of fresh water and an unlimited supply of pumps and osmotic membrane and turbines you can harvest energy from the process you already need?
IDK… calling it a power plant seems like the stretch. But I’m not a languager.
The things a guy has to do to get some electricity around here.
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Fuk u oka(y)?
i recognize you probably have no racist intention.
non-English speakers and bilingual English speakers, including those who speak Asian languages, often experience that type of mocking of their language. if it happened once to one person in the history of earth, it's not racist. but the collective effect over generations and across thousands of experiences creates accumulative pressure on specific identity groups of people. the pressure and related coping/denial behaviors can manifest in unpredictable and inconsistent ways which may be why not everyone understands that racial mocking causes measurable harm.
tl;dr
it really helps if you would not do that. even more so if you could help stop others who you observe doing the same.
Wasn't a racist comment. Words that sound different in different languages can be some of the fun of learning languages and all cultures do this. When I lived in Germany, there is the classic example of "gift" sounding like poison.
In Japan good luck introducing yourself if your name is Gary - It sounds like diarrhea.
Since you are passing judgment, id say it would really help if you didn't see everything through a racist lens. It implies a degree of projection. Its ok to take some innocent pleasure out of things like language - it works in all directions and does not involve othering unless it's done with some malicious intent.
if you would reread my comment, you would see i said twice that i don't think you are trying to be racist.
however, the impact of harmlessly-intentioned statements is completely determined in the mind of the listener.
if you feel i judged you, that's an example of how my intentions are out of sync with the consequence on your feelings. i apologize. it's also reinforces my point.
to clarify, you might originate a statement, make a comment, then it leaves your mind and your body. the affect on you is done and any meaning in the words is frozen. people, myself included, tend to think our intended meaning is more explicit (denotation vs connotation) in our words than it actually is.
like a pebble in the air, that comment can land in the ground and not touch anyone, not trigger anyone's feelings.
for comments about a person or about culture that's tied to people, it's hard to argue that no one could ever have any feelings about it.
i understand you're implying that comments about funny sounds in languages are abstract and/or unavoidable, and that it's harmless to enjoy. I've also made such jokes, and I'm not immune to my own criticism. and just because this type of joke has happened for generations, that doesn't mean it's an unalterable process of the physical universe. if a human does it, that human can stop it, make it better, make it worse, etc.
just imagine your native language being mocked everyday, by the majority group surrounding you, it started before you were born, over time you can sense that it affects your family members, reduced their confidence, maybe they're highly educated but for some reason they don't achieve "success", whatever that means for your culture. maybe they were bullied in school or at work.
you might think I'm suddenly bringing up fiction and distorting the issues. scientific research has proven that culturally related mocking is linked with bullying and has racialized effects on the targeted people. racialized effects meaning, among other things, giving them the sense that if they try to participate in certain areas of life, like employment, applying for home loans, dating, politics, showbusiness, they might be rejected. that sense has also proven to be accurate in the sense that (in USA) people who have been mocked in relation to their race definitively do get rejected in all fields and endeavors more than non-mocked (majority) people. that's after adjusting for income level, education level, skill gaps, language barriers, etc.
again, to repeat, i know you probably didn't make the comment thinking "hey what's something racist i can do"
wha
You racist piece of fucking shit