Why don't we get our drinking water by taking salt out seawater? (2008)
scientificamerican.com
scientificamerican.com
In the bay area, I'm paying ~$2.80 per cubic meter.
I don't see why it's not feasible.
Yes, there are transmission/pumping costs. Assuming the water we're getting now is free, that's still only ~50-75% increase in cost over current costs.
I haven't seen a detailed analysis, but this could look good for California, notwithstanding the other problems with desalination (ecological).
But anyway, arguments about cost of making drinking water are moot. We need it, so eventually all options will be explored as needs increase.
Also desalinated water does not to be used the moment it is produced. One can run desalination facility at full blast during the day using renewable energy and at a lower or even trickling speed during the night using cheaper, often wasted otherwise energy from the grid.
The advantage is that you need a smaller desalination facility, as it can run at 100% duty cycle. Pumped hydroelectricity could do something similar, but why not have a go at removing the losses of converting back to electricity. (Then again, if you have an electric pump you already have most of the equipment required to produce hydroelectricity by running it in reverse, so pumped hydro might be better because it is more versatile?)
The drinkable water can be viewed by itself as "salty water + stored energy". If you produce it at any time where electricity demand is low/or production exceeds demand you store energy already produced, be it by nuclear or renewable power plants.
And then you can build the pumped-hydroelectric power station where it makes sense, not being limited to the coast line/big city being close.
Even if one lives on a desert coast there may be times where it makes more sense to purify and store water from say flash floods than desalinate it from the sea.
IMHO your idea may work if we think about some isolated location not attached to the grid and without some power plant running 24/7. No idea at which scale pumped hydroelectric starts to be viable.
Which to me sounds completely negligible in real world terms.
https://www.unep.org/news-and-stories/story/five-things-know...
https://web.archive.org/web/20190114220150/https://www.reute...
I have no idea how much of an impact that would have though.
Of course building infrastructure affects nature, on land and in the oceans.
I see you didn't click my second link, and/or research it yourself. ;)
But even if the magnitude of harm were unknown, that doesn't mean we can just default to "ignore it."
Additional sources:
https://www.frontiersin.org/articles/10.3389/fmars.2022.8451...
I think you confused it for The Hague, which is in The Netherlands.
The sun doesn’t shine at night, the wind doesn’t blow all the time, and batteries often are astronomically expensive and impractical at large scales. Solar and wind vary greatly, both over an individual 24-hour period, and seasonally throughout the year. A nuclear plant is producing its maximum capacity 93% of the time, as opposed to wind (34%) and solar (24%). To get 1 GW of reliable energy at any given time, you need 3-4 GW of wind and solar in the hope it will be enough, as opposed to 1.1 GW of nuclear. (Worth noting that coal is only 48% reliable).[1][3]
In order to build a grid that is able to meet demand consistently and reliably, you would have to massively overbuild renewables so they were able to meet peek demand, and deal with the issue of huge load shedding during times of overproduction. See section 5 and 6 of [1] for a study of what it would take to reach 80% and 100% renewables for California. To reach 0% fossil fuels, a total of about 7GW of nuclear power (the equivalent of 4 Diablo Canyon plants) would reduce needed wind by 11.5GW (the equivalent of over 5 million wind turbines) and solar by 5.7GW (the equivalent of 1.8 million rooftop systems). When you only need 40% the capacity, even double the cost is cheaper. Nuclear is only expensive when you compare it to coal and natural gas, which are baseload generating power sources. Again, with intermittent renewables, it is cheaper to build nuclear than to massively overbuild solar, wind, and grid level batteries.
[1] https://www.eia.gov/electricity/monthly/epm_table_grapher.ph...
[3] https://www.energy.gov/ne/articles/what-generation-capacity
No nuclear power plant ever created has stopped costing money yet, even ones that have been closed for 30+ years. They are costing taxpayers millions per year, each, for the foreseeable future. How can anyone know for sure what the actual cost will end up being?
Meanwhile, the cost per Mwh of batteries is very likely to fall, considering that almost every major economic centre started building battery gigafactories during the pandemic and new chemistries are already viable for cars.
I suspect that energy storage will soon be so obviously the right choice that even if someone decides to make a nuclear plant today, they won't finish it because it won't make financial sense.
Nuclear power is prohibitively expensive even in a best-case scenario. All estimates that have indicated otherwise simply ignore most of the costs. Political decisions socialize the costs to the state and future generations. Even in the US.
Read up on the current costs of closed plants like Rancho Seco in the US, recent developments around EDF in France, and the statements from Sweden's riksgalden for more info about this. TLDR, you are paying for closed nuclear plants already, and so will your great great great grandchildren. They will pay all their lives for plants that won't give them a single watthour of power. This is a monumentally bad idea IMO.
How about we instead make a nationwide push on things like hydrogen gas from seawater and solar?
When the hydrogen gas is burnt, it creates salt-free H2O as a byproduct, and in the meantime it's a good energy storage solution to solve the intermittence of renewables.
Your grandchildren will praise you instead of curse you.
Realistically speaking, because buying water rights from existing farmers is probably even cheaper.
https://www.youtube.com/watch?v=9nlkW16t5lM
It's probable the reason water costs that much for you is because people are still willing to pay that price for it.
Capitalism truly sucks.
Except the core premise is not true, so far as I can tell. To confirm this I went on Uber Eats, looked for chain restaurants near Salesforce Tower, and surveyed their beverage menus. At initial glance, most restaurants charged more for "water" than for soda. However, on further inspection this is because in those cases, the soda was dispensed from a fountain and the water was bottled. The latter obviously would cost more than the former, because of the cost of having to transport individual bottles. This can hardly be attributed to "Capitalism truly sucks". Furthermore, in cases where a soda fountain is available, the restaurant is legally mandated to provide the water to you for free[1], which makes the cost of water in those places $0. Of the places that only sell bottled beverages (there's surprisingly few):
* California Pizza Kitchen charges the same for water as for canned soda, and gives you more water[2]
* Chipotle Mexican Grill's cheapest beverage is bottled water[3]. The second cheapest option? San Pellegrino sparkling water, shipped all the way to California from Italy.
That said, the economic principle of "thing x costs more because people are willing to pay for it" is probably true (see for instance, airfare that's bought late), but this isn't one of those cases.
[1] All restaurants are technically supposed to, but having a soda fountain virtually guarantees that they can't weasel out of it by saying that they only serve bottled beverages and don't have cups for serving tap water
[2] https://www.ubereats.com/store/california-pizza-kitchen-53-t...
[3] https://www.ubereats.com/store/chipotle-mexican-grill-211-su...
What do you mean? I'm not arguing that cheaper water options don't exist- just that the fact that you seem to be surrounded by said options doesn't mean that everyone is.
The video may very well be true for certain regions, it's absolutely not a universal fact or rule of any kind, but I proposed it as a possible explanation, in an attempt to be helpful.
Actually, the exact wording used by the video is a "service station". Luckily uber eats also delivers from those, and after sampling some in my area I can say that the statement is also false for them.
Of course, you can't prove a negative. However, considering that the video just asserts the fact without evidence, and I actually have hard numbers, I think it's fair to say that we can tentatively conclude that the statement is false. I suppose you could make the argument that the actual claim isn't that the phenomena is widespread or common, but that it merely exists. However, that wouldn't make sense in the context of the original comment, which uses that video to conclude "Capitalism truly sucks". If most establishments are pricing water and soda "correctly", and there's a few outliers that don't, it doesn't make much sense to cite that and conclude "Capitalism truly sucks".
I think capitalism sucks, not because there is not a single place on earth where it is detrimental, but because there are plenty of places where it is. There are obviously the big offenders - the faceless megacorporations in the US and stuff like that. It's not like I'm saying it's impossible to get capitalism to work. I'm just saying that it sucks that it incentivizes stuff like this to happen, even if it doesn't happen everywhere.
and remember... "most establishments" in your area. Some people, live in different areas than you, and the relative price difference is not necessarily the same worldwide.
I don't want to repeat it again, so I hope this explanation is good enough. Just because the video isn't true for you doesn't mean it can't possibly be useful to anyone, if they happen to be in an area where water is more expensive and they're trying to figure out why.
But really, your argument just doesn't make sense to me. It feels sort of like "works on my machine", except it's "water isn't more expensive in my area". Mh.
Olive oil from California is also much cheaper than Olive Oil from Italy.
In both cases, it's up to you to decide if you think there is any actual quality difference, and if such a thing is worth money to you.
Alternatively, the soviets usually only had one (maybe two-three if it was military equipment) brands or models for any one thing. So there is that alternative.
Where do you buy cheap Californian olive oil? Whenever I’ve seen it for sale (rarely) it’s always a more premium product available only in medium sized glass bottles while Italian olive oil is available in large plastic containers.
If you go to Safeway.com, there are clearly a couple different ‘markets’ or sub-verticals in olive oil. Glass bottle ‘fancy’, plastic jug ‘bulk’, and large metal jug/tin ‘medium fancy bulk’.
Looking at the sub-categories, it it seems like Italian extra virgin is typically about 2x in price of Californian equivalents within a given sub-category, but there are some Californian brands coming close to equivalent.
Like Californian wines vs French.
Each sub-category for oil has its equivalent of 2 buck chuck of course.
There was a period of time where I did switch to water, when I first started my ADHD medication. And you're right, even though I didn't find the water "tasty", I was perfectly fine drinking it and just using the feeling of it instead of the taste.
It did take a while even after the meds stopped working for me to switch back to soda. I think it actually happened just because we ran out of water bottles and I was still thirsty. Which I guess proves that I still have thirst at least.
How many different places have you had tap water? The tap water in SoCal, west Texas, Seattle, and Hawaii all have distinctive tastes. Or have you tried distilled or R/O water?
My hope is that one day, small scale nuclear power (sometimes called "modular nuclear power") will make this a reality.
Using the above methodology, I ran numbers for a desalination factobattery and it's really bad, like two orders of magnitude more expensive than just buying a Li battery to buffer the unreliable energy and running desal 24/7.
Thanks for educating me!
Amortized capital costs for desalination runs about 40%,[0] so if you "charge" for 12 hours and "discharge" for 12 hours then your facility doubles in size, so your desalination cost increase by (at least) 40%. This doesn't even account for added maintenance btw.
If you charge for 6 hours (ie the solar peak) and discharge for 18 hours, you need a facility 4x as large, and your desalination costs increase by at least 160%.
Desalination isn't 'free' energy storage.
[0] https://www.advisian.com/en/global-perspectives/the-cost-of-...
Also, the concentrated brine is a real problem in any area that has regular sealife. Maybe not a big problem in the salt ponds already, but it will kill off anything normal.
I studied in a tangent area and either I'm dumb or DOE had a lapse of reason that day.
Having five reactors per site is going to be worse than two of equal installed power in almost every respect. USA is the fourth largest country in the world, how is reduced footprint even a consideration?
If you're still interested you can start at the DOE site and follow those links, NuScale (https://www.nuscalepower.com/en) has a bunch of stuff to, they will send you white papers). Anyway, I doubt they are going to go anywhere before the first round of the climate apocalypse gives people the "You can either put in a nuclear power plant or you can all die, which do you want to do?" choice.
A power plant is only ever "done" when it finds itself on a far more valuable land than when it was built or when your politicians decide to go back to fossil fuels, something that should pretty much never happen.
That said, if it does need to happen, traditional 500MW PWR sites have been restored to green field condition.
SMRs are expected to by 1.5-2x as expensive as traditional nukes, it's borderline fraud at this point.
I know I’m already at that point. Just experiencing the southwest heat and lack of water for my life has been enough. It strikes me that the US could absolutely resolve so many of its problems with known tech today, but refuses. And definitely it takes some shattering moment to wake people up. We recently had the hugest wildfires known and I don’t quite see much difference locally. But these things take time.
1) Get a library card for university (this will more reliably get you papers than sci-hub). Sometimes you can just pay them for one, sometimes you have to register for a course (1 unit courses in the US can be inexpensive and even if they are in basket weaving as a "student" you get to get a library card :-)
2) With the assistance of the reference librarian find the journals that cover the topic you're trying to master and go through the papers. There will be some "highly cited" papers that everyone refers to, some "medium levels of citations" and then typically you'll see papers that take the research in one of a few directions. You can choose to either stay in "survey" mode at this point or dive down one of those directions.
3) Read the papers and learn from the results, you may find subjects that you didn't learn as much as you needed to in order to read the paper (math, chemistry, physics, etc) for each of those, you find text books or things like the Chaum's notes for the subject to bring you up to the level you need in order to understand the paper.
If you keep at this for a while you will start finding that when you read a paper you both understand what they are doing and may instantly develop an opinion on whether or not you think it is "good" and will be able to explain why it is or isn't good.
At that point you are now the "master" of that topic. You don't have the degree but you didn't have to write a thesis either so there is that :-). If the university you chose in step 1 has professors doing stuff in the area you could probably co-write papers with them.
Even the RBMK reactors, which had lecturers in the 1960s pointing out safety flaws, needed human intervention (and quite a lot of materials fraud) to actually go boom. TMI similarly needed some humans to fix it until it was broken (also why there is a genuine good-faith lobbying argument to mandate less maintenance sometimes, especially as higher-quality equipment wears slower).
You'd still need security, and frankly security for the security, though.
Maintenance is basically pulling the pipe up every couple of years and replacing the membrane which will become fouled over time, but generally it would be deep enough that it would not get barnacles and other mollusks on it.
Have we ever built a working prototype/plant that does this?
The problem is, your fresh water is now several hundred feet below the surface. To raise it up to where you are, you need pumps to push up the same exact pressure differential that you got by putting the membrane so deep. And if you need to do that anyway, just use surface level water and pumps for ease of maintenance and access.
You pump out the top x feet of water from the pipe. The equalizing levels of inside and outside the pipe is what drives the upward flow through the membrane.
Perhaps the advantage is that you can lift in multiple stages, so each pump doesn't bear the full column pressure. Also the pumps aren't exposed to salt.
Am I missing something here?
The pressure at the membrane will only ever be the difference. It has nothing to do with the depth the membrane is actually under the water.
Air pressure increases slightly as you descend a well, but not enough to change the outcome.
What you’re saying would imply that the Titan submersible would be at the same pressure whether under an ocean of water, or in a well the same depth. No. The former is 375atm, the latter is a bit more than 1atm.
You only need to lift the top layer of water a little bit. The rest of the water column would come up after it. Of course, you cannot lift the top of the siphon more than 10m above sea level.
While operating, it's basically a deep open well with a bit of water at the bottom. You need to pump that water out to keep the process going.
It is incontrovertible that this system would have to push the water up from below.
I don't think the math works out all that spectacularly though. The pressure difference would be a about 1.1 MPa, and desalination of seawater takes ~6MPa, so by running a pipe down to the bottom of Monterey Canyon you could... save almost 20% of the energy costs.
Which makes sense. You can't build a perpetual motion machine by sticking a pipe with a membrane at the bottom and a turbine at the top into the ocean. Even if it's a very long pipe.
If we can run those for hundreds of miles through water, pumping thick sludge that is crude oil....
There absolutely is.
All you need is a bunch of mirrors to direct the sun at a chamber filled with water. The water will evaporate, the expansion into steam creates significant pressure so you can run it through a turbine, and then once the steam cools down and liquifies again, it won't have any salt in it.
It's not even remotely expensive. Mirrors are cheap. The turbines/etc are basically the same as a coal or gas power plant and mirrors are a hell of a lot cheaper than mining coal or gas. Also if you're boiling a usable quantity of water you'll be generating a lot of power, which is a handy byproduct (more valuable than the water to be honest).
"Not in our back yard" is the real issue. The chamber is generally at the top of a tower, and even painted black all that sunlight focused onto it is very bright. People generally don't want a really bright object on top of a tower anywhere near them. I guess you could build a wall around it or something, but you'll still get complaints from aircraft/etc.
Driving into the sunset or sunrise is annoying. Imagine if that was all day every day instead of just for 20 minutes or so.
Having said that, if you're in a remote area to counter the NIMBY issue, and clean water is hard to find, then the system I've described is very effective and they are being used for cost competitive farming of cheap crops.
Anyone who actually wants to desalinate seawater can do it. It's just that almost nobody wants to right now.
How big a tower are we talking about for the steam volume necessary to turn a reasonably sized turbine?
Why use so many words when there is literally a very old term well established in use?
They have their own issues and they require quite a bit of real estate. Not something that was easily obtained in Sunnyvale but I'm sure that there are places where they would work.
> People generally don't want a really bright object on top of a tower anywhere near them.
There is a stretch of road near the tower that is uncomfortable to drive on during the day, the tower is so bright. I honestly can imagine that many a child has hurt themselves staring at it, it is extremely eye catching and there's really nothing else to look at in that desert.
I'm all for green power (I have an electric car that I feed from roof-mounted solar) but these towers should be very far from population centers.
0. https://sfpuc.org/sites/default/files/accounts-and-services/...
Basically you put a reverse-osmosis membrane at least 231 meters deep in the ocean. If you put it deeper, you could potentially extract both freshwater and energy.
I didn’t get to the whole paper, but I imagine the challenges of keeping that membrane clean are remarkable.
Ok, I’m being brief but you seem genuinely curious, so, lemme explain what I mean:
In thermo, you would draw a line around a closed system, and say basically conservation of energy applies in this system. Energy in = work out + losses.
In a system where one input is the ocean, you basically just consider that infinite because of the size differences. One dinky little pipe compared to the mass flow into the system from the ocean, that math would be silly to bother with. That said, to swat down the stupid “this is perpetual motion” comments from people with Reddit engineering degrees, you also have to add in the energy input into the system of the sun, which is keeping the water from freezing over the course of 1 million years as it runs someone’s sarcastic water wheel.
Adding salt is endothermic, it absorbs energy.
Most people have this mentally backwards since it's currently so hard to separate salt and water and they don't really notice the water getting cold when they stir in salt. But... there's no reason a process couldn't separate them and give off energy from a thermodynamics point of view.
The separated state has an easy way to receive energy to overcome that hump. It just needs agitation. There should be a way to reverse it and gain energy but we haven't found a good way yet.
That is separating salt from water releases energy. There's nothing perpetual motion about a process that separates fresh water and salt and also gives energy. I'm not sure if the above works or not but physically there's no issue with this.
Think about it - if it really worked you have invented a perpetual motion machine, since you could just feed the fresh water through a little water wheel back into the ocean.
You don't need to do any maths at all to know that his maths has gone drastically wrong somewhere.
Saying “maths” instead of just math sounds quite odd, why are you making it plural? Is solving one equation “a math” and solving multiple equations “maths”?
> So, get off your ath, let's do some math.
Still a minority in people right?
The sun isn't what causes pressure in the ocean...
The Anglo-American linguistic divide is always fun to examine. We don't always come out ahead, but now and then we get winner like "acclimate."
If you don't like something coming between "mathematics" and "are", how about "I can prove Fermat's Last Theorem, but the mathematics are pretty high level." One could argue that many people would say "the math is pretty high level", but I think I've heard each before. It doesn't feel odd to write at all.
Maybe a single mathematic would be a single concept/subject, like arithmetic or algebra?
The four mathematics are arithmetic, geometry, music, and astronomy.
> maths
That's what it's called in the UK (and maybe Australia & NZ). Shortening of mathematics. I could say the same about "legos". :)
It may be wrong but it really isn't "obviously delusional."
Also - 231 meters deep is where, in theory, you'll just start getting fresh water coming through your membrane. Which is 231m deep. Fresh water that you'll spend plenty of $energy to pump up to the ocean surface.
(For reference - Hoover Dam, when brim-full, has a slightly lesser drop from the water surface in the reservoir to the output of the hydroelectric turbines. You'll be pumping $energy in, to lift each ounce of your "free" fresh water up to where it is useful.)
[Edit - from some quick calculations, and the density of sea water relative to fresh water...it looks like the "don't need to pay to pump the fresh water back up" version of this scheme will need to run its osmotic membranes at the bottom of the Challenger Deep (~11,000m), or something pretty close to that.]
Sounds like a cool sci-fi premise.
Best case scenario, pumping 1 kg of water 230 meters costs 2.3kJ.
Elsewhere in this thread it was mentioned that typical desalination approaches need 10-15kJ/kg.
All of these sorts of repairs are also required for land-based water treatment facilities, of course, but now you have to perform them all at 230m underwater. That’s gotta be mega-expensive. Furthermore, all of your equipment needs to be able to survive at those depths, with saltwater attacking exposed surfaces and seals, requiring much more expensive materials and tighter tolerances.
It really doesn’t seem very economical to me!
I think a good analogy for this is oil extraction. These days we extract oil from places where it's more expensive and difficult to do so, because we can no longer meet demand with the cheaper options (many of which have simply dried up over time). But we'd never go after the expensive-to-extract oil 40 years ago (or whatever) when cheaper options were available that could meet demand.
You add your osmosis filter at the end of a long flexible hose. For maintenance, you reel it back in.
From what I can gather, oil rigs have profit margins below 20% (at best) and margins decline as the pressure in the well head drops, until they become totally unprofitable and shut down to wait for oil prices to go up. Water prices would have to increase by more than 2 orders of magnitude to make this strategy begin to approach profitability!
A cubic meter is ~264 gallons.
Here in my area of California (CA has lots of water agencies, so YMMV) 1000 gallons costs $38.66 (varies based on total consumption).
So that's $10.21 for a cubic meter.
...straws surrounded by air don't work beyond 10 meters, because the external pressure at the bottom of the pipe doesn't exceed 1 atmosphere.
Obviously this isn't true if the pipe does down into the ocean.
If you have a pump 230 meters below sea level trying to push water up a pipe, to get water to the surface that pump must be exerting the same amount of pressure as you'd be experiencing 230 meters below sea level (since otherwise it wouldn't be strong enough to push up the water column). So you might as well just take the pump up to sea level and have it pump water through the membrane, since it would be exerting the same amount of pressure.
Or alternatively, you could just find a hill that is 230 meters high, pump sea water to the top of it, and then have the sea water come down in a pipe and go through a membrane in the bottom. Should be totally equivalent without requiring anything underwater.
The reason you don't need to "pump" to force the water through the reverse-osmosis filter when you're down that low is because the overall pressure at that depth is sufficient to push the water through as-is. Merely raising water up 230m in the air and "dropping" it through a pipe into a filter sitting on the ground would not give you the same amount of pressure.
Put another way, the pressure of the water in a 230m-tall pipe on the filter on the ground is much lower than the pressure of all the water 230m under the surface of the ocean pushing on that submerged filter. While the pipe ensures that the water stays confined, it is not putting pressure on the water in the same way all the water in the ocean is putting pressure on the water that's being pushed into a 230m-submerged filter.
I imagine there is some way to do what you describe above-ground, my my intuition is that it would require essentially recreating a large ocean, suspended in the air (not as large as the Atlantic, say, but still fairly large). Much more efficient to just use the ocean we already have.
For the submerged filter approach, I think the biggest challenges are probably maintenance and keeping things stable and functioning at the pressures present at >230m below the surface. Those challenges might make it infeasible. I don't think the need to pump the desalinated water back to the surface is all that large a problem in comparison.
So you couldn't run a filter or anything, unless it's literally magic.
If someone put a pump at -230m and pumped out the water on one side of the membrane so that on one side the pressure was 'ocean' at -230m, and the other side was mean sea level, then yeah the membrane would work.
Notably, this requires roughly the same amount of work and energy as pumping water from the ocean at sea level into a filter so it has roughly the same pressure you would find if you did the first thing.
There is no free lunch.
The water at the ground level on the ocean will have the same pressure as the water at ground level in the pipe. The water at 230m down in the pipe will be the same as the water 230m down in the ocean.
Even if the pipe is capped on both ends.
The post I replied to said the opposite - that the pressure at the surface of the ocean would be the same as the pressure at the end of a pipe going under water, if there was a pipe.
Which clearly isn’t true or we’d have a trivial perpetual motion machine.
Edit: it looks like they changed their post?
which really puts into perspective how insane desalination, with it's order of magnitude higher energy costs is. why spend all that energy when we could simply build more infrastructure to capture more peak runoff from the sierras
If we use the water at depth. I think the way to go is underwater living pods.
If we go this route, I propose we also kickoff a solid Merpeople program (Mermaids, Merman, etc). The goal woukd be to gradually move the human race to be Merpeople. One day we will be viewed as the Neanderthals and Merpeople the people. As everyone knows, the hallmark of any reputable Merpeople program I'd breathing underwater, indefinitely, in Salt water. If we've been able to achieve that it's reasonable to assume we'd also be able to engineer the ability to "drink" seawater directly.
All this to say, I guess there isn't really an application for this.
We need way more daylight than most people realise, look at what goes into a submarine who are already living in a what is effectively a cramped mobile blacked out cave.
Living under water in pods has been done before but damp was the biggest issue from what I remember.
I'd imagine there are stepping stones along the way. We won't make it all the way to fish people right away, we'll likely have amphibian people first. Those people, amphibian people, should be pretty good in living in damp environments.
All that to say, I think we're good.
I like the idea of wave energy but the economics are really difficult in large part because the ocean is a difficult environment.
If the membrane requires 231 meters of pressure differential, it would stop moving water when the water was still about 230 meters from the surface.
Why Is Desalination So Difficult? - https://www.youtube.com/watch?v=mxqOPdEUNTs
"The idea behind the process is simple. It combines two unlimited resources - sunlight and seawater - to provide ideal growing conditions for crops in hot, arid environments.
The innovation utilises the cooling and humidifying power of water vapour produced from evaporating salt water. Using modeling and simulation techniques developed in collaboration with our partners at Aston University, we are able to process local climate data to predict greenhouse performance and inform the design. The combined effect of reducing temperature and increasing humidity, together with providing a protected environment for crops, results in up to 90% reduction in evapotranspiration. This greatly reduces irrigation requirements, which can be provided by desalination, and improved growing conditions.
As a result operating costs are lower, yields increase, and farmers can benefit from year-round production of high-value horticultural produce. "
Given average water use per person in US is 310 liters/day (82 gallons) [1] and average electricity cost/kwh is $0.17 [2], and assuming 14 kJ/kg. 310 * (14 / 3600) * $0.17 = $0.20.
[1] https://www.epa.gov/watersense/statistics-and-facts
[2] https://www.bls.gov/regions/midwest/data/averageenergyprices...
This study found these uses for indoor residential use: 18 gpd toilet (~10 flushes), 15 gpd washer (~1 load every few days), 11 gpd shower (~5 minutes), 11 gpd from faucet (~5min of flow, this one surprises me), 9.5 gpd from leaks, 1 gpd dishwashing
that's 65gpd right there. A ten minute shower and slightly more frequent laundry would easily get you 82gpd on indoor use only, ignoring any irrigation / outdoor use.
Is that wild?
Perhaps in the sense of "on average, families have 1.6 children" (or whatever it is) — i.e, these are aggregate numbers, not to be taken as specific examples of actual households. Interpreting statistics can be tricky like that.
Also, to be fair, that study (I briefly looked) just lists toilet per-capita GPD in the quoted section ("Daily Per Capita Use"); it does not equate it to a number of flushes. They do have a whole section devoted to toilet flushes though — see "ULF Toilet Savings".
That translates to about 3.25 watt-hours/gallon as the theoretical limit, if my math is correct.
Source: https://www.desware.net/Energy-Requirements-Desalination-Pro....
E.g. https://www.nationalgeographic.com/science/article/partner-c....
And this is not by choice: Greece has to deal with extreme volatility in resource consumption throughout the year. Add to that it has ~6000 islands (around 200 being inhabited year round -- 227 as I google). And the tourist island/islet focus changes throughout the years. With this context, there can be no "I will create a pipeline of fresh water" or any other project like that really.
We're playing silly buggers with economics again here; when it's rainy, "DeSaL iS uNcOmPeTiTiVe", because the "market rate" for water is pennies per meter cubed. Except, oh wait; suddenly it's dry, the "market rate" skyrockets" and large parts of your economy collapse. The "market rate" was always giving a massive* surplus to consumers, and now it's gone.
This is A Bad Thing.
Turns out it would have been better to have a slightly more expensive water source that was reliable. This fact is somehow obvious to everyone except economists, who should (at least in Europe) be called out as frauds for universally advocating along such idiotic lines.
The energy costs are tied to oil because thats the cheapest option. Well, besides coal. If solar were cheaper wed be using it.
The current record price for solar is slightly over one cent per kWh and still people will write that oil is the cheapest option.
The installation rate for solar is such a steep graph that drawing it legibly is a real problem, see https://nitter.net/pic/orig/media%2FFOoa6xYXIAQKUnv.jpg for example, and still people will write that "if solar […] we'd be using it".
But running the desalination when energy is cheap makes a lot of sense. Especially when not providing all the water but topping up when supply is low. The only problem is the capital costs of desalination plant that isn't used all the time.
If power costs are the driver then solar will be the answer
A great thing about desalination with stills is it uses the natural water cycle, the water that comes out is cleaner than any other as it uses that.
> A concentrated solar still is a system that uses the same quantity of solar heat input (same solar collection area) as a simple solar still but can produce a volume of freshwater that is many times greater. While a simple solar still is a way of distilling water by using the heat of the sun to drive evaporation from a water source and ambient air to cool a condenser film, a concentrated solar still uses a concentrated solar thermal collector to concentrate solar heat and deliver it to a multi-effect evaporation process for distillation, thus increasing the natural rate of evaporation. The concentrated solar still is capable of large-scale water production in areas with plentiful solar energy.
In a handful of places, it is. In the rest, it's so much more expensive than alternatives that it's borderline insanity to use it.
Like ice: ice is cheap in Antarctica! But importing Antarctic ice to a desert would be absurd.
We just haven't found a good process. That's it. Cheap desalination is not physically impossible. The deep ocean separation that someone here mentioned seems quite promising and gives off energy which is expected. Salt has weak bonds in water and when they reform the na-cl bond there's a lot of energy to be had.
I wonder what is the reality now.
Like this Creating Drinking Water Using Ocean Wave Power (https://news.ycombinator.com/item?id=10522700)
But what happens to them? Initiatives never seem to go anywhere far....... energy requirements.... no financial incentive/interest? Same sort of tepid interest as general climate change initiatives?
As mentioned in another post. Basic utilities can easily become affordable with proper regulation.
Desalination is economical in the middle east because they export oil. In Israel it's economical because they export tech knowhow, and have foreign income sources from their diaspora networks. Some people will moan about "tax havens! for the filthy rich!" But really it's just viable habitation for locations without a lot of resources to export. Favourable capital rules are a valuable export. We do this in customs-free zones around the world today. If you have those rules in an area that needs a desalination plant to survive, I guarantee you it's going to work really, really well.
For Australia the correct thing is to store the damn (or should I say dam) water that falls where people live.
I remember reading about light driven sodium and chloride pumps, if we could make these transport ions across some biomembrane we could desalinate water.
Clean drinking water. Hydrogen for for fuel.
Really mostly nimbys. Greens have relented.
Nuclear desalination would solve a lot of the fresh water problems but we can't have solutions now can we?
Head in the Sandies is probably even more encompassing. From people that tink the solution is drilling for oil in national parks to people thinking suing developers and separating their trash is all you need to do. They're stupid people. Neither should be influencing policy.
Seems to me that the usual historical options aren't acceptable. Business as usual looks bad. The traditional solution, genocidal warfare seems like a really bad idea for someone living in an industrial civilization. We could degrowth. But the Khmer Rouge tried that in the 1970's and back to the rice fields didn't work very well for most people.
So seems like technological mitigation is all we can hope for.
The state approved 3 new plants this year alone and more are coming.
We’d find new ways to desalinate in a week!
It depends on the country though, countries like Saudi Arabia get most of their water though desalination.
For decades, the weather report in Israel would include the water level of the Sea of Galilee, the only real lake in the country and the source of most of the nation's drinkable water. It would be a major concern during droughts. Now there's so much desalinated water that some are actually being pumped into the lake, for environmental reasons.
money.
Think of everything good in the world we could have but don't because we and everyone else want to keep as much money as possible.
Otherwise you could solve these problem by printing money.
Collecting money is just a side-effect of people being selfish.
https://time.com/personal-finance/article/average-american-s...
"American households, on average, have $41,600 in savings, according to data last collected by the Federal Reserve in 2019. The median balance for American households is $5,300, according to the same data."
We also might find more efficient (cheaper) ways to do desalination, which could tip the scales toward it earlier.
https://scitechdaily.com/new-device-purifies-saltwater-over-...
It's just still much more expensive that just pumping free fresh water from rivers, lakes, and ground water. So you'd only do it if water were actually scarce.
I think this is why the scare-mongering over fresh water availability (agriculture excluded) is mostly just hot air. Fresh water is only scarce at ridiculously low prices. Raise the price and the market will solve the problem quickly. That matters for agriculture, but not for human consumption.
Even many dry regions that are far from the ocean, like the southwest US, only have water problems because most of it is used for agriculture at ridiculously low prices. Price it appropriately and that will end very quickly and there won't be any shortage.
I'd love to see an aqueduct covered in solar panels roughly along I-40. Drain the too-wet southeast to irrigate the too-dry southwest.
The reason for the dearth of pests is that it's a desert. If you change that, the pests will arrive just like everything else does.
Agree that the current system in the southwest/western US around agricultural water rights is just stupid, though. Agriculture uses water in some disgustingly inefficient and wasteful ways, because they're incentivized to do so.