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
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?
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.
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.
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?
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.
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.
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
> 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.
You have a good point. Since “100 years” and “a thousand years” and “one hundred and eighty million years” are the same thing, we should not categorize nuclear as different from fossil fuel. While every number below five billion is the same thing, the number of years until the sun dies is an importantly different number that’s basically infinity. E+8 is the same as E+3 and E+9 is infinite
This reasoning isn’t transparent reasoning for folks that want to sell E+3 fuel becau
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
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.)
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.
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.
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.
Ah, so a slightly more efficient desalination plant then.
Slightly more efficient, with less waste.
Pretty solid win-win
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.
According to this delightful overview [1] of the desalination plant, the capacity overall is 12000kW so that's definitely close enough.
1. https://www.niph.go.jp/soshiki/suido/pdf/h21JPUS/abstract/r9...
Why are we assuming 3kWh per cubic meter of water?
I did some cursory research and that seems to be a common estimate for modern osmosis-based desalination energy costs.
If you have a better estimate, feel free to supply it.
> 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.
Yeah it's like regenerative braking vs losing that energy as waste heat.
Great analogy. This is similar to producing gas from sewage to feed back into the gas network, which is used to cook food, which produces sewage. (i.e. https://www.hofor.dk/english/hofor-utilities/town-gas/)
Can't we just process it into salt/lithium and whatever is there? Since its already concentrated?
If you want that much salt, then yes. But you probably don't
> 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.
Basically this is like the recouperator on early heat engines, but with a liquid gradient instead of a thermal one.
It's making desalination more efficient and the effluent a bit easier on the ecosystem.
Goes nicely with the "pressure exchanger" which recovers the pressure of the high pressure brine waste stream. Lots of heat exchanger analogies!
https://en.m.wikipedia.org/wiki/Pressure_exchanger
Yeah those are funky devices. I'll be curious to see what the production cost per cubic meter of fresh water ends up at.
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.
The amount of power consumed by the desalination process >> the amount of power produced by the osmosis power plant
It is more like it slightly reduces the power required to run the desalination process
Wow, that completely changes my opinion.
In fact, it almost seems that you could simple pull in sea water as the “low salt” water and still have a large enough delta against a brine solution.
Really interesting that it also solves the brining issue.
explains your username, explain like im like 17
thanks
> it is expected to generate about 880,000 kilowatt hours of electricity each year
100 kW, in sensible units.
I don't see how kilowatts would be more sensible than kilowatt-hours here, especially since the power output might not be consistent.
See also, "Power is not Energy": https://youtu.be/OOK5xkFijPc
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
Kilowatt hour per year is a power unit, and not a particularly useful one in my opinion.
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?
*An average of 100kW assuming 100% duty cycle.
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.
It's going to partially offset the power usage (and the effluent brine) of the desalination plant that feeds it.
A few percent of it, probably. 150 kw is peanuts for grid power generation and desalination is fairly power hungry.
I’ll take the 150 kw if you won’t
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.
Pff, there has been a 50 kW osmotic plant operating in The Netherlands since 2014, how is this news?
source: https://en.wikipedia.org/wiki/Osmotic_power
It is expected to have about 8760 hours each year.
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.
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?
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.
So let me get this straight:
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.
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.
1. https://fragelada.fysik.org/index.php?amne=Energi&stage=&key...
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
I believe Singapore does that and gets almost pure water. https://en.m.wikipedia.org/wiki/NEWater
> 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.
Some other *renewable* energies. Nuclear isn't generally considered renewable.
But it's inexhaustible. Sun will die at some point and moon will fall down to earth. Then we'll have no solar and no waves.
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.
https://en.m.wikipedia.org/wiki/Uranium_mining
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
"As a rule, strong feelings about issues do not emerge from deep understanding."
Do you believe that underground elves are continuously manufacturing more uranium, or what do you believe is the case?
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
The question is whether current nuclear power can be considered renewable. The answer is that it is not.
Renewable, to my mind, means energy that will be there in a million years. Solar. Wind. Waves. That kind of thing.
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.
You have a good point. Since “100 years” and “a thousand years” and “one hundred and eighty million years” are the same thing, we should not categorize nuclear as different from fossil fuel. While every number below five billion is the same thing, the number of years until the sun dies is an importantly different number that’s basically infinity. E+8 is the same as E+3 and E+9 is infinite
This reasoning isn’t transparent reasoning for folks that want to sell E+3 fuel becau
Bro what the fuck are you talking about. This comment is incomprehensible.
I love nuclear power and know a lot about operating them, however:
1) It's expensive. Very very expensive.
2) It's dangerous when not operated properly, and I don't trust commercial interests operating hundreds of these due to this reason.
3) It's bad for the environment, both the mining to get the uranium and all of the processes to turn it into fuel.
4) There is no answer for spent fuel.
Whereas with solar or wind you can basically remove #1, #2, and #4, however you still have to mine and process the materials.
Anyways, nuclear will be great for some niche uses, I am sure, but it isn't the answer to our green energy prayers.
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.
My rebuttal is this: where’s the nuclear plants then?
It’s not economically viable. No amount of (ugh) Jordan Peterson whining will change that.
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
> 4) There is no answer for spent fuel.
We store it. There are radioactive waste storage sites in 39 US states, for example.
https://curie.pnnl.gov/system/files/SNF%20and%20Rep%20Waste%...
Humans haven’t stored anything for twenty thousand years yet.
How do you know that?
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.)
This french startup has a pilot osmotic plant near Marseille : https://www.sweetch.energy/
It sounds like this recovers some of the energy that the desalination plant used to create fresh water and brine from ocean water?
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.
People are willing to waste energy to avoid drinking their own (treated) sewage, before it's temporarily mixed in the ocean.
It must be very wasteful in water - nearly all low-salinity water is easy to recycle, but here is wasted for a tiny powerplant.
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.
It uses high salinity brine that's a byproduct of desalination.
Your parent is talking about the "fresh" (treated wastewater) side.
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.
Coverage readable (although most images are missing) without JavaScript: https://www.independent.co.uk/climate-change/news/japan-osmo...
Wait... so they have made a plant run by the power of mixing fresh and salt water so it can separate the salt out again?
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.
Is there a more ironic way to power a desalination plant?
It has a pleasant symmetry to it, I think.
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
[1] https://youtu.be/N3bn57twbHM?si=nmxVjFPaeaxlTqyk
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.
TL;DR: They made desalination 5% more efficient.
It's achieved by extracting some energy from the dilution process of waste salty brine with freshwater before dumping it to a river.