They really fail to explain a key point here. The reason you colocate this with a desalination plant is because you use the super-salty wastewater from desalination as the salty side of the osmosis power plant. Then you find some wastewater which is low in salt (such as semi-treated sewage), and use that as the fresh side of the osmosis power plant.
The end result is that the salty wastewater is partially diluted, which means it has a lower environmental impact when it is discharged to the ocean.
Yeah, this is the coolest part. The leftover brine from desalination is generally just a problem. It's harmful to the marine habitat if you just put it back into the ocean, and there isn't a lot else good to be done with it. (Basically you have to dilute it first.) But this way you get useful work out of the dilution!
The article also doesn't say if it produces more power than the attached desalination plant requires. I doubt it as you'd be getting close to a perpetual motion machine if so. In which case basically what you've got is a very energy efficient desalination plant, more than a power plant.
Fukuoka's desalination plant treats about 16400 m^3 of water per day. Assuming 3kWh per m^3 of water, this works out to a time-averaged power consuption of ~2000kW.
The osmotic power plant generates about 100kW, so it's about 5% of the total desalination energy requirement.
Depends on the CAPEX and OPEX requirements. If it is cheap to do, it could be a solid win, but if the plant requires a lot of capital, it might be cheaper to just take the hit on efficiency
Yes the brine could just be diluted wih gray water to reduce the environnemental impact without the energy recovery of the osmotic plant and the capital can be invested in other renewable with better efficiency.
That being said it's a first so it's a pilot project needed to have feedback on a real plant in operation and not just back of the enveloppe calculations and suppositions. Sometime you need to just build the thing to encounter problems, issues or non-issues.
> The article also doesn't say if it produces more power than the attached desalination plant requires. I doubt it as you'd be getting close to a perpetual motion machine if so.
Not really. Even if it would generate enough to power the plant, it would still rely on work being done outside of the plant, i.e. the flow of semi-treated waste-water and possibly the brine itself.
It's harmful to a tiny watershed of marine habitat immediately downstream of the discharge pipe, and dilutes rapidly. With that said - if you can harvest a meaningful amount of energy from desal anything helps. I don't know that 5% is a meaningful amount, however.
> They really fail to explain a key point here. The reason you colocate this with a desalination plant is because you use the super-salty wastewater from desalination as the salty side of the osmosis power plant. Then you find some wastewater which is low in salt (such as semi-treated sewage), and use that as the fresh side of the osmosis power plant.
They do hint at it at end:
> “It is also noteworthy that the Japanese plant uses concentrated seawater, the brine left after removal of fresh water in a desalination plant, as the feed, which increases the difference in salt concentrations and thus the energy available.”
And the "fresh" water is also "treated wastewater". That could mean a bunch of things but in most cases it's water that's released into the environment by the water treatment plant. Its quality can be as good as clean water, but most municipalities wouldn't feed that right back to the consumer, they dump in a river or lake instead.
Aren't there better uses for the treated water than this? Can't you use it instead of desalinating salt water? Or just run this treated water through the same RO and you won't produce any brine and the result will be just as pure.
Yeah I think that's the difficulty here, the technology needs just the right kind of placement and the right surrounding setup. There is a desalinization plant nearby, they feed the water into the city, the city uses the water, the sewage comes to the water treatment plant, they clean it up to environmental release standards and instead of dumping it back into a river or the ocean, they use it together with stronger brine from the desalinization plant to produce some electrical power.
From what I understand most municipalities do not directly feed sewage treated water right back to the consumer, normally they dump it into a lake or river first. A lot of that may just be an informal "yuk" factor not necessarily not having the technology.
It's cool but everything sort of has to be aligned for it to work well.
Usually you loop the treated waste water through nature for dilution (and more filtering if you use ground water) in case there is some problem with the treatment process.
Also it is kinda hard to sell to people the concept of “you are drinking literal shit/piss” even though if you stop and think about it all lake/river/reservoir water is full of fish, bird, etc shit.
This sounds pretty awesome, recycling the waterwaste in a sort of feedback loop resulting in drinking water and power.
I am kind of curious on how much you can/should optimize this process until it becomes dangerous or unmaintainable. And can we do this on more places on this planet? For instance somewhere on a desert coast or something? Could be cool to build some of those between Sahara desert and the ocean, combined with solar panels or something.
I find 100 kW a lot more tangible than some nonround number of thousands of kW times hours. People use kW for car charging, for heaters (toasters, microwaves, space heaters are all the same), etc. so you can directly say how many of those fit in the nice round 100 kW
But if you happen to know that a typical person in a rich country like you're probably in (5th percentile of the world population) uses about 1.5 MWh/year, I guess you can also approximate a MWh figure by saying 1 MWh/year is close enough, so I'd understand if someone says that works for them
> a typical person in a rich country [...] uses about 1.5 MWh/year
That's just electricity, not energy. The real figure is probably ballpark 50 to 100 percent higher (probably mainly depending on climate for heating/cooling demands and the heating method being used) but I haven't looked that up now. Just wanted to remark this (can't edit anymore) so it's no longer completely misleading
I totally agree. "kWh/year" might be what people in the industry use (some people still use British Thermal Units, in the USA ...) but for a scientifically literate lay person "about 100 kW" is far easier to understand than "about 880,000 kilowatt hours of electricity each year". (I hope I calculated that correctly.)
Expecting it to operate most of the time is a safer bet than expecting it to have a peak output that’s substantially higher than the average. It’s be smart to try to align it with power usage, but in truth it’ll lag behind peak water usage by however long it takes to top off the tanks. I don’t know when that is but I would suspect before morning rush hour.
Probably this thing peaks at 120-150KW which isn’t going to fix the grid.
You might use this as a big battery where you store the desalination brine during the day when you have excess solar power and run the recombination in the evening and overnight when solar drops.
What do you mean sensible units?
kW is instantaneous power whilst kWh is the amount of power created in a unit of time. In other words, this power plant generates 100kW of power and produce 876MWh in a year.
If you have an average of MWh a city needs, having MWh is a helpful metric, as well as kW to make sure you can power the city on peak consumption. No?
This one is pretty annoying coz even if you support the idea of "kilowatt hours", it's common to discuss power station capacity in terms of Watts (plus for journalists the obligatory "this is enough to power N homes / a city the size of Coventry"). So it's like they're deliberately choosing to be obscure here!
This energy is not free. Solar cells and wind embody the cost of production of the device as the input cost along with cost of construction, and transmission, but the primary energy input is predicated on a real externality: Wind and Sun.
This system depends on using a LOT of energy to maintain an osmotic pressure gradient. That it turn depends on pumping water across a boundary. Energy has to be expended. Now, if you run a de-salination plant and/or waste water treatment you have to expend MOST of this cost anyway, so you are scavenging energy back from an unavoidable, non-externality cost.
This is a big difference. Wind and Solar bring energy in from the Sun and weather, outside human expenditure. This brings BACK some expended energy, doing another job.
I suppose hypothetically, given immensely saline water CLOSE to less saline water you could expend significantly less energy to arrive at the boundary condition but its for kilowatts, not gigawatts or even megawatts. The places which have these conditions might also have high sunlight or wind conditions no?
I think it's meant to help reduce the salinity of waste from the desalination plant in a process that recovers some energy to make the whole system a bit more efficient.
1. I take a shower and produce non-salty waste water
2. That waste water and brine from a desalinization plant can be used in this plant.
3. The result is concentrated waste water and less salty brine and some power
4. The power can be used to (partially) power the desalinization plant produces fresh water from sea water and brine.
5. I get fresh water for my shower.
And the diluted brine from step 3 goes to the sea? Or can it be run through the desalinization plant again? Does concentrating the waste water in step 3 also help with the eventual treatment of it
The article mentions "partially treated wastewater", which I take to mean "water that we're ok with dumping into the ocean, but not ok with drinking". I think you can generally read this as a way of gaining some utility out of this partially-treated wastewater before you dump it into the ocean by mixing it with the extra-salty brine from the desalinization plant. The utility you get is:
- a bit of energy that would have just been wasted
- a more environmentally friendly product to dump in the ocean than just straight brine
I imagine someone out there does a cost-benefit analysis to compare this system to just fully treating and reusing the wastewater and thus needing to desalinate less saltwater.
The diluted brine goes out to sea. It's less harmful than dumping the concentrated brine you had before, with the bonus that you got some power out of it.
The concentrated waste probably gets disposed of rather than trying to get the remaining water. You treat it like the results of a waste treatment plant. You might dehydrate it a bit, just so you don't have to ship the water, but you probably won't try to recover any more water than you already have.
Does it generate enough electricity from freshwater to offset the energy used to desalinate more water? Would it be more efficient to just treat the freshwater that would have been used to run the plant for drinking water and desalinate less water?
No, the fresh water always produces less energy than it took to desalinate the fresh water to begin with. If the freshwater is recoverable, that will always be energetically better. But if you can't recover the fresh water for some reason, like say there is a particular contaminant that is impractical to remove, or it's going to be used for some application like irrigation or feeding a nature preserve where higher salinity is tolerable but you're never getting the water back, then it reduces the overall system losses.
On the other hand, there are often restrictions on how concentrated your brine can be when released so it doesn't cause environmental problems. If you have to dilute your brine anyways, might as well get a little energy back.
It seems like it would have to be more efficient to further treat the semi-treated wastewater. However there is often resistance to putting treated waste-water into reservoirs.
If you're using water at the end of a process that's just going to get mixed anyway, you're just extracting waste energy from the mixing process. Basically the fresh, used water and the highly saline water are in a lower-entropy state, and normally we'd just dump both in the ocean and allow the entropy to increase without extracting energy. But in this case we allow their entropy to increase in a controlled environment and so we're able to extract some energy in that process.
> While it is still an emerging technology being used only on a modest scale as yet, it does have an advantage over some other renewable energies in that it is available around the clock.
I notice the 'some' here, and the absence of the word 'nuclear' from the article, which of course is also available around the clock. Most readers will know something about Japan's troubled relationship with nuclear power and can fill in that context themselves, but to my eyes, it's a startling omission.
Nuclear is quite exhaustible. If we use it to power everything, we have about 100 years worth. It's just another kind of fossil fuel, storing energy that was captured long ago.
According to some quick googling and rough math, there's about 5.5 billion years worth of U-235 present in the Earth's crust on the top 15km. If we consider that we can maybe reach 0.5km down, (deepest gold mine is 4km), and assuming it's evenly distributed, then that's only 180 million years!! (2024 global electricity usage)
Think we can figure out breeder reactors in 180 million years? If we're going all nuclear, I'd expect them in under 1,000 years, but I'm not an expert.
Idk why this is downvoted. People should look it up before you thinking someone isn't contributing to the conversation
> The European Commission said in 2001 that at the current level of uranium consumption, known uranium resources would last 42 years. When added to military and secondary sources, the resources could be stretched to 72 years. Yet this rate of usage assumes that nuclear power continues to provide only a fraction of the world's energy supply.
Or depends also on what we're willing to pay for the power but critics already call it too expensive compared to be viable given renewables' price and price history
The estimate is outdated but I didn't quickly find newer info and it's just generally not a weird notion to say it's exhaustible
Imo we should make use of what we have and not wait for everyone to put solar on their roofs to supply like 10% of what we need and then wonder how else we're going to reach net zero (especially in local winter), but that's another discussion
I think those numbers unfairly assume many things, including:
- breeder reactors will not exist in time
- we will not find more uranium on Earth than we have already
- we will not be able to economically extract uranium from seawater, phosphate minerals, coal fly ash or other sources
- other materials besides uranium will not be used in the future
- synthetic production will not become viable
To say that nothing will change in the next 40-70 years and we will simply run out of material and stop using nuclear altogether, just seems quite far-fetched in my opinion.
I love that you can post whatever you want on the internet. “Nuclear is quite exhaustible”, “The earth is flat”, “Ernest Borgnine killed JFK” you can just put words together and put them online. Such a thrill
No but technology improves. Breeder reactors can take the current fissile material (assuming estimates of the total fissile material are accurate, which isn’t necessarily accurate) and extend it by about 60x, meaning thousands of years or even closer to tens of thousands of years. And we don’t need it to last forever. Just long enough to get to fusion.
Fusion will be the permanent end of all known life in the universe, as we compete with each other to boil the most ocean to make more bitcoins, leading to a planet with a helium atmosphere and no water.
I’m just having fun posting online as an expert on nuclear energy that’s never heard of fusion, breeder reactors or thorium it is a blast because you can just write numbers. 100 100,000 100,000,000 are all the same to me
Exactly. Nuclear power is not eternal because uranium is finite whereas solar will last forever because the aluminium, cadmium, copper, gallium, indium, lead, molybdenum, nickel, silicon, silver, selenium, tellurium, tin and zinc to make the panels exist in infinite quantities
If we can extract minerals from the Earth then we can extract them from PV panels to refurbish/build new PV panels.
If you don't like that, then there's also concentrated solar. We're not going to run out of mirrors.
Fissile isotopes on the other hand, once they're gone, they're gone. You can build new reactors that run on different fuel but that's not the same thing as you were doing before, so you can't call the original process renewable.
1) It's actually not that expensive, but the regulations made it so. I remember something from titans of nuclear or some Jordan Peterson podcast. I'll try to write the gist of it here:
There was some rule, that the cost of safety (like how thick concrete should be in some places), could be so high, that the usually cheaper fission energy would be equal in cost with the other sources (like burning oil). Then came the oil crisis of the 70's in USA. The safety margins got boosted to crazy levels, without any realistic gains. Moving from 99.999% to 99.9999% safety (just an example).
When the oil prices dropped, safety standards stayed and now fission energy is expensive. At least in USA and EU. Not in France or South Korea, which streamlined the regulations.
2) not with the modern technology, it isn't. And there are even safer alternatives like marble balls reactors that can't meltdown even if cooling is shut down.
3) not using it is bad for the environment. Fuel requirements are minimal compared to other plants. Even some types of renewables pollute more per W of energy produced. Like wind turbines that will fill up landfills at some point.
4) Thorium reactors. If we just give the fission energy some research & development, we can burn all the spent fuel up in thorium reactors.
Same reason why Germany closed it's nuclear plants ahead of time or switched to burning gas in "green" propane gas-burning powerplants. Regulations.
You add tariffs and you make steel production profitable in US. China subsidizes it's electric cars industry and they can sell EVs in Europe for half the price of European cars, literally killing the market.
You subsidize renewables heavily and you get windfarms that are unprofitable once subsidizing ends.
I'm sure that in a free market situation, your comment would make lot of sense. But this is not the case and you should read up a little.
I believe that one should aim to, in spite of their political views, try to see the big picture. Like why there's so little nuclear vs sun or wind.
Germany had a badly designed prototype reactor with 80 incidents in 4 years of operation and one particular incident on the 4th of May 1986 - a week after Chernobyl accident, where reactor operator was lying about it. No wonder they have those regulations and general public distrust in anything nuclear: https://en.wikipedia.org/wiki/THTR-300
Requirement 73 of the IAEA's Safety of Nuclear Power Plants would be a start. That rule is so stringent that it requires bag in/bag out procedures for changing HEPA filters at nuclear power plants.
Bag in/bag out was developed for labs handling infectious micro-organisms. It involves a complicated bagging system, which, if done properly, isolates a contaminated filter from the environment during filter change outs.
But for nuclear the bag only protects from alpha particles and electrons. It has zero impact on photon dose. If workers are wearing bunny suits and respirators they are already protected from alphas and electrons. The extra change out time required by Bag In/Bag Out increased the worker photon dose.
This regulation actually increases workers’ exposure to radiation.
OK so how does that reduce the cost of nuclear effectively? That has to be a savings of a few tens or maybe a hundred grand over a year, it's peanuts. I'm asking for big examples, ones that would convince someone that regulations truly are stifling nuclear.
They're all in France, whose construction began under a military dictatorship to ensure energy security whenever the US starts a war in a place supplying it with energy.
This strategy was proven decisively correct in 2022, and also applies to solar and wind when the US (and by proxy, the whole West) inevitably gets into it with China and suddenly your degrading solar panels and growing need for energy become major problems (and thus forces you to build out nuclear anyway).
Cost isn't the only factor here, and it would be short-sighted to take the cheaper short-term option by buying Chinese rather than paying our own people to regain and retain that engineering and construction experience we foolishly squandered 30 years ago.
"Excessive regulation" is always the excuse but I have literally never seen someone show how that is the case. They'll show you one or two low-hanging fruits and then extrapolate that into saving billions of dollars on construction or something. It's ludicrous that anyone even repeats this argument without even knowing what they are talking about.
Humans haven't had agriculture for twenty thousand years yet.
Also, this line of inquiry is still just tilting at windmills; "somehow, future Fred Flintstone manages to get a hold of equipment capable of digging out a mile of concrete and yet somehow not know what radiation is" is not a productive line of thinking at best and a bad-faith argument at worst.
Humanity's mechanical capacity to dig that deep actually post-dates its discovery of radioactivity, too. If they have the technology for it for them digging it up to become an issue, they'll be able to identify, trivially, that it is an issue.
And if humanity can’t do anything that it hasn’t done before, why should we care about power generation or any problem that wasn’t completely solved before today? (Like today. The day that you are reading this.)
I know because storage of spent nuclear fuel is a pretty big deal, and right now the USA is simply sequestering it on-site with no plans beyond 50-100 years because there is NO solution for long-term (20k years) storage.
Nobody asked you about what’s a big deal or not. You answered a question that nobody asked you. I asked you how do you know that humanity has never stored anything for 20,000 years. You would need a list of every thing that was ever buried by a human and then proof that everything on that list has been dug up.
“Nuclear waste makes me nervous” is not proof that we have dug up everything that has ever been buried.
Given the (possibly intentional?) inability to parse language here, to make sure that you’re not a bot, is it possible for you to answer the question? If yes say yes and then answer it, if no just write something vaguely anti-nuclear
I'm not anti-nuclear, I'm realistic and I understand the technology and it's pitfalls. I was trained to operate nuclear power plants, I understand how they work and I'm not scared of the tech. I'm scared of letting American corporations who have zero accountability construct and operate them.
We could reprocess it but choose not to. This is what France does. It’s not a novel process. Instead we stupidly let it sit there and pay to secure it.
I am quite rational, thanks. See my other comment.
Also, France has a state-owned company operating the plants. I would not be averse to an American version of that, or perhaps just expand and enhance the training they already do for the naval nuclear power program and send navy nukes to operate them. I don't trust American corporations to operate them properly.
As well as diluting the brine produced by desalination. Unclear if it's worthwhile though. As another commenter pointed out, you could treat the source of your low salinity water to produce fresh water instead and bypass a lot of this.
In 1998 when I was in high school I dreamt up this kind of power plant and asked my physics teacher where the power really came from. Not happy with his answer I asked a university physics Q&A service [1]. Not happy with their answer either I did a masters in engineering physics and kept asking this question whenever I got the chance. Never got a really good answer. But I’m glad to see it works.
My instinct here is just to wave it away saying "I bet the temperature of the system falls when you do this, and you need a minimum temperature for it to work over a given salinity gradient". Is it not that simple?
The freshwater used in this osmotic power plant is produced by a wastewater treatment plant, and the high-salinity water used is the wastewater generated by a seawater desalination plant
So, if the freshwater produced by wastewater treatment plants is further processed into usable freshwater to replace the freshwater produced by seawater desalination plants, soon one water treatment plant could replace both the seawater desalination plant and the osmotic power plant, reducing steps. I believe this would greatly improve efficiency
Fukouka isn't particularly in short supply of access to water, it's just not convenient for them.
The region is humid and rainy for over half the year and it's only particularly dry for about a quarter of the year. And they have a comprehensive system for evacuating stormwater during the rainy season as well.
So I'd reason a guess that they have a waste water excess 1/2 to 3/4 of the year but still need the baseload capacity of the desalination plant for the remaining chunk of the year. And while you could probably switch over to plain seawater for the portion where you are running negative, it may not be worth the added maintenance/cleanup cost of having to deal with salt or brackish water for only a small portion of the year. So instead you just eat the losses for that window in exchange for the increased efficiency/lower complexity/lower operating costs.
220 households, at say $2k/year of power bills is just under $500k/year revenue, plus whatever else from "disposing" of hypersaline water (if that's even a reverse stream?)
I hope this is just meant to be a tech demo, and doesn't have any advantages of scaling yet.
Exactly. Well not exactly. The desalinization plant produces brine (very salty water) as a waste product. Rather than disposing of it directly, they use the brine to generate electricity. This electricity is then used partly to run the desalinization plant.
As an imperfect car analogy, the way a turbocharger uses energy from the exhaust to inject energy into the intake, in the form of compressed air.
Neither is a perpetual motion engine, but both make the useful work more energy efficient.
Japan seems to really be into osmotic pressure for whatever reason. It reminds me how in Splatoon, the reason given for why the character die when they touch water is osmotic pressure and there's a whole scientific explanation about it.[1] However, that all got cut out in the international localization for some reason.
Maybe there's a cultural reason why Japan is more aware this is a thing that exists? Dunno
It's routinely featured in Japanese equivalent of SAT tests. So anyone with a high school diploma at least have heard about it, most with a degree from a Japanese university have made attempts to solve a quiz involving it, and anyone with any degree from any of national universities have solved a question on that topic at least once.
They like reading random Wikipedia articles I think. It's normal in kids' stories for a character to do a cool technique and then a third character to explain how the cool technique worked based on the Wikipedia article the author just read.
The end result is that the salty wastewater is partially diluted, which means it has a lower environmental impact when it is discharged to the ocean.
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