Article puts the cost to produce a cubic meter of water at $1-$2
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.
As a person who has run through this particular loop once with local politics (Sunnyvale's northern border is the SF Bay which has former Morton Salt ponds in it) what I ran into was two things, one that there wasn't a cost effective power solution for just desalination, and two, the players don't care about water to individuals (drinking water and what not) because there is absolutely no risk whatsoever in the bay area of not having "enough" of it. The political block that kills it is a combination of local pop saying "we don't want nuclear/cheap power in our back yard" and the folks farming the desert in the central valley saying "If you can't supply farms, why would you do it?"
My hope is that one day, small scale nuclear power (sometimes called "modular nuclear power") will make this a reality.
FWIW there is a really fun "disruptive" desalination option that could work in places like Monterey Bay which is just dropping a really really long pipe down into the ocean that has the desalination membrane at the bottom of it. Top of the pipe is above the surface. Water pressure at depth drives water through the membrane and up the pipe. At the surface you just pump fresh water out of the pipe like an ordinary fresh water well.
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.
The pressure at the bottom of the ocean will need to push thru the column of water as well as the membrane - there's not enough energy to do that (otherwise, there'd be spontaneous water sprouts in the ocean!).
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.
Pumping x feet of water creates x feet of pressure difference. How is that better than doing reverse osmosis at the surface?
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.
In theory, wouldn’t you be able to just keep pumping from the surface of the pipe (increasing x) until x provided a sufficient differential pass through the membrane? It would then stay at x even while you continue pumping. The pump would merely need to lift the water from x below sea level.
Pumping from the surface, like with a vacuum? The maximum height of a drinking straw is about 10 meters. It's generally easier to lift water by pushing from the bottom than pulling from the top.
I mean the “pump” probably isn’t a vacuum pump. Maybe it’s a water screw. Maybe it’s a rope and bucket. The effect is the same, no? The water must be lifted X.
The site pressure at a bottom of a well is irrelevant. You do realize air pressure is not what matters, but pressure as a whole? That includes water pressure.
The bottom of the straw is not in a well; it’s more akin to a cassion, so you need to factor in the water pressure as well.
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.
In order for the reverse osmosis membrane to function, you need a rigid pipe at atmospheric pressure, without water in it. The pressure difference inside/outside the pipe is what powers the desalination process.
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.
Maybe the thought is that if you drop a 4000m-deep-to-surface pipe into Monterey Canyon, there will be a pressure differential at the base of the pipe (since sea water is denser than fresh water).
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.
Why would you need to lift in different stages? If you take the top 3 feet out of the pipe, the water pressure will push three more feet into the pipe.
Seawater has a higher density, about 2,5% according to Wikipedia. So 40m of water column fresh water vs seawater would be equal to 1m water column fresh water. 400m would result in a 1 bar pressure difference.
Reverse osmosis systems (like the one speculated with a membrane) has operating pressures between 40 and 82 bar when using seawater. The ocean is pretty deep but having a 16 kilometer pipe straight down seems like it has its own engineering problems.
It does sound clever at first glance. It caught me at first, too.
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.
There was a startup pursuing a test setup using an oil derrick of Santa Barbara if I recall. These guys[1] were proposing a different system (basically providing fresh water to an underwater habitat) however the paper goes over the basics pretty effectively.
> there wasn't a cost effective power solution for just desalination
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 are you handling the byproducts of the concentrated solar distillation process (ie remnants not evaporated in the focal point chamber, salt and anything else you’re not filtering out prior to steam production)? Does this solution assume a closed loop heat exchange system, where the primary loop feeds a steam generator (which is fed raw saltwater as feedstock)?
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 such a tower 50 km south of my house. We see it brightly even at this distance.
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.
I don't quite understand the rest for the turbine? Once it's steam can't you just cool it and then you have a distilled water source? I.e. steam through coils becomes water again.
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.
I think you misunderstood the comment. I agree there has to be a buffer somewhere. You're arguing that we can get a free buffer by piping the water behind a reservoir, but the cost is that the very capital-expensive desalination plant will be idle half of the time. I'm proposing that the more economical option is to buy a lithium ion battery to buffer the renewables and run the desal plant 24/7. (You can still pipe the water behind a reservoir if you want)
Desalination plants do REALLY badly when run infrequently. All the salt water, brine, etc. creates absolute havoc when it sits for random period of time, and maintenance costs are already a huge part of opex for desal plants.
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.
Yeah, it isn't going to hurt the salt ponds. What is more, we did the math and found you could harvest more salt faster for less money when starting with a higher salinity brine which would be a win for Morton.
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%.
The smaller the reactor, the worse neutron efficiency gets, good old cubes and squares. Good practices also require as many hands/eyes for normal operation a GW class reactor as a 50MW one.
>Advanced SMRs offer many advantages, such as relatively small physical footprints, reduced capital investment, ability to be sited in locations not possible for larger nuclear plants, and provisions for incremental power additions. SMRs also offer distinct safeguards, security and nonproliferation advantages.
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?
There is probably a literal ton (if you printed it out on 20# paper stock ;-)) of stuff written about how small modular reactors are a much better answer to deploying nuclear power than big LWRs. In the desal pitch the ability to scale them as needs scaled "quickly" as well as the ability to decomission them when they were done by picking the entire reactor complex up and transporting it off site were the primary selling points.
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.
Is there somewhere I could read to become very knowledgeable on all things desalinization?
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.
Have you ever done a masters degree? If not, this is how it works (and this works for ANY subject, not just desalination)
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.
Sorry to disappoint, if it was easier we would perhaps have a wider base of expertise on which to rely upon. On the plus side, the more areas you develop the faster the new ones are to develop as the base subject (math, physics, chemistry, biology, Etc.) overlap a bunch of different disciplines. I've been working through some tomes on Organic Chemistry for a plastic waste processing idea/project and that is a pretty slow slog. Beyond its use in semiconductors I've not been a huge chemistry fan.
The downside of more waster per GWH and/or greater enrichment requirement far outweighs that.
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.
Good practice should really follow the joke about airliners: the ideal flight deck crew consists of pilot and dog. The pilot is there to look after the dog, the dog is there to make sure the pilot doesn't touch anything.
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.
Additionally, if there was a nationwide push to nuclear power, we'd have cheap, clean energy -- putting a sizable dent in both clean drinking water & climate change at the same time.
I'd like to ask this here again because I haven't got a clear answer yet. What about building a plant, getting the fuel, storing the fuel, and decommissioning the plant, how is that affecting the cheap and the clean energy in total greenhouse gas emissions? Is it worthwhile compared to wind farms and solar power? And where is the fuel stored in the States, because here in Germany it's hard to find a place to store it for 10 millennia.
Some countries recycle nuclear fuel (e.g. France and some other European countries) whereas others don't (the US). It has obviously some costs, but it also decreases the waste. The re-processing center in Europe is located at La Hague (Netherlands).
>Is it worthwhile compared to wind farms and solar power?
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.
>it is cheaper to build nuclear than to massively overbuild solar, wind, and grid level batteries.
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.
>Additionally, if there was a nationwide push to nuclear power, we'd have cheap, clean energy -- putting a sizable dent in both clean drinking water & climate change at the same time.
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.
I think what you’re really saying is it won’t be until enough people demand a change to a safe path to push through political and monopolistic powers. I fear it’ll take the thing that ultimately allows progress in sciences, the eventual demise by natural causes of powered opponents. (Which may itself never come due to inheritance.)
Desalination seems to be well-positioned to take advantage of variable energy prices, particularly in dry-summer climates where demand for water increases at the same time as solar energy availability. If you run the desalination system when energy is cheapest, your energy storage problem becomes a water storage problem, but a simpler one than with pumped-hydroelectric storage.
I haven't seen a detailed analysis, but this could look good for California, notwithstanding the other problems with desalination (ecological).
Absolutely, but it's a scale problem. Say you want to produce 1000m3 a day. Well you can build a small plant that makes 41m3 ish an hour and run it 24/7. If you want to produce 1000m3 a day in the three or four hours where solar energy is very cheap you need a plant that does 250m3 an hour - or about 5x the size. So your energy is cheaper but your capital cost is 5x or so.
Maybe it could be combined with pumped hydro? Pump the water to a higher elevation during daylight hours, then use the pressure of the elevated water to drive osmosis based desalination around the clock. You would have to build a reserviour, but it only has to be big enough to hold 24 hours worth of water. If there is not a high enough hill, some/all of the elevation difference can be in the form of a hole, such as an old mine.
Assuming you use the sea water: in a hot climate if the reservoir is exposed evaporation will make the water more salty. Building covered elevated cisterns just for the salty water energy storage may be too costly compared to other options, not to mention the risk of creating a salty desert / contaminated aquifer in the case if it leaks out.
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.
> One can run desalination facility at full blast during the day
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?)
Actually one can take out renewable energy produced at the desalination facility or anywhere close to it out of equation.
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.
There's inherently no advantage to just taping the two things together. The idea is to make drinking water. Storing energy is a separate challenge. There's no advantage to combining the two.
The requirement for a large high-low point for pumped storage to be effective would limit it to a few areas wherein it could be viable. I imagine other energy storage technologies would be more viable.
If you save enough on energy, you can switch your system to save on capital. RO has a fancy nanostructured membrane but electrodialysis or MSF might be easier to build at the cost of 20-50% worse efficiency.
That also increases capital costs, putting us back to square 1. Also, have a look at the energy requirements of desal plants. "a few batteries" is pretty gargantuan hand waving
Maybe the storage could be part of the energy solution, by pumping to an uphill resovior when power is cheap, and sending it through to downhill resoviors via a hydroplant during the peak hours.
I don't think there are very many places that pumped hydro can be built, where it hasn't been built. You also need quite the significant height difference for it to be meaningfull.
That helps with storage on the output side. But what about the issues/capital costs/resource/labour usage of building huge capacity plant that only gets used 15% of the day?
I don't understand the question. Why can we only pump into aquifers 15% of the day? The point of having massive storage is that you can build a smaller plan and run it all day.
But anyway, arguments about cost of making drinking water are moot. We need it, so eventually all options will be explored as needs increase.
The problem isn't "the ocean." The problem is the brine sinks and forms a hypersaline layer, creating a dead zone in coastal waters which are typically highly biodiverse.
Solar prices have plummeted, and that use case can skip storage issues (just run when there's power available). Obviously land, labor, and infra cost are not so simple.
Desal plants need to be running constantly and incur untennable startup costs otherwise, if I am not mistaken. Perhaps state of the art has fixed that issue.
Another thing I'm curious about -- Dean Kamen's "Slingshot". Seems like we'd be well served if his vision was realized: https://www.slingshotdoc.com/the-film
Well this it's done in some parts of the world, I am not sure why they claim is not. My brother lives in Lanzarote an the water is extracted from the sea just like this. The energy comes from 2 huge wind turbines in the plant.
Might be the (2008) bit? I remember there was a bit of political hoo-hah here in Perth about a big desalination plant back then. Now most of our drinking water is from either desalination or waste water reprocessing.
Desal costs seem to have decreased a lot since 2008. Now maybe one-third as much, based on a quick image search for charts of the price trend of desalination.
that's money we could spend on building infrastructure to divert peak flows on wet years to recharging the central valley aquifer, which is several orders of magnitudes larger than all other reservoirs in the state combined
You are right, I was summing both the sewage discharge and clean water supply costs, which gets you 4.42 USD / m3. But looking for San Francisco tariffs, I see you also pay a separate fee for sewage discharge, with is approximately 5.9 USD / m3 [0]...
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
Restaraunts aren't grocery stores, though. I don't think their prices are directly comparable, nor is the simultaneous existence of cheap or free water particularly convincing evidence that the video is based on a completely false premise.
My grocery store has a free water fountain (near the bathroom area) where I can drink cold water until my belly is full. They also have bottled water options starting at $0.50. The Deli area will sell you a 40oz cup of ice water for $0.15, but they will give you a free one if you make a purchase from the deli. Please try again?
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".
> 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.
Italian sparkling water can command a higher price because... Italian.
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.
> Olive oil from California is also much cheaper than Olive Oil from Italy.
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.
Yes, but no. Water in different locations has different chemistry. The levels and kinds of dissolved minerals differ drastically and that affects the taste. In theory it's possible to take distilled or r/o water and add exact amounts of various carbonates, chlorides, and sulfates to match any water profile. In practice, it's not worth it it.
I don't like water that has a taste. It's the reason why it's so hard to get me to drink it on a consistent basis. I always go back to soda because water tastes bad. Some people say I might be tasting the hydrogen or oxygen in it, some people say it's the minerals or whatever, but either way, I find it unpleasant.
More likely? You’re conditioned to not pay attention to thirst, and to need lots of sugar and the like to drink something. I bet if you went a couple weeks without soda and drank more water, you’d probably find the water tasty and not drink any more soda for awhile.
I don't know how to tell if I'm not paying attention to thirst. I know that I can forget to eat for days at a time when I'm hyperfocusing, but I've at least gotten better at thirst management.
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.
different water brands has different taste. there is water that I can drink, and there is water that I can't. you just need to find those that you like. just get 20 different bottles and taste till you find one that is tasteless for you.
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?
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.
That article's subtitle: "In principal, but probably not in practice, fresh water can be extracted from our oceans for no expenditure of energy" [Italics mine]
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.]
Wouldn't pumping from 230 meters be exactly equivalent to just pumping through the membrane at sea level?
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.
I don't think that's correct. Pumping water from below the surface of the ocean is about overcoming gravity. The pipes themselves would need to be constructed to withstand the pressure of the water around it, of course, so the pipes don't collapse.
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.
I think you are incorrect. If you build a 230-m tall pipe and fill it up with water, the water at the ground-level end of the pipe will be at the exact same pressure as the water 230 m deep in the ocean. Hydrostatic pressure only depends on the depth, not the container shape.
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.
a pipe 230m tall with the bottom at ground level would experience the same hydrostatic pressure as water 230m under the ocean. the pressure comes from the weight of water above it, not distance from sea level. this is literally how water towers work.
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.
To be clear - unless there is work done to reduce the pressure at -230m below mean sea level, there is zero pressure gradient there. Anything sitting at -230m will feel a pressure gradient of essentially zero.
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.
Yes, this is how normal reverse osmosis filters work. However, pumping water at that pressure obviously takes a motor and consumes energy. What's interesting about the OP's concept is that in theory it can be performed with no energy expenditure at all.
I think you’re still going to get killed on maintenance costs. When the membrane gets clogged, how do you replace it cheaply? How do you repair/replace damaged/worn out pumps? What about sections of pipe and the fittings?
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.
Cost is never immaterial. We look at the various ways we have to provide fresh water, and do whatever is cheapest. If shipping fresh water from places where it's abundant to places where it's scarce is cheapest, we do that. If/when that becomes expensive enough to make desalination attractive from a cost perspective, we start doing that. If the >230m below the surface idea turns out to be cheaper than surface level plants, we do that. But I don't think anyone really knows for sure if the underwater method could be cheaper, so we're all just guessing here.
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.
Yes, economical is always important. In this case, we’re comparing a 231m deep unit with the “boring” existing design, and finding it less economical than the current designs.
It’s not just that it’s expensive, it’s also ridiculously complex. About the only thing I can think of that would be more complex is launching rockets into space in order to collect water from comets.
Straws don’t work beyond 10 metres. You need all your pumping equipment either at the bottom or distributed along the pipe. Either way, that’s going to put a ton of strain on your “flexible hose” when you try to reel it back in. And what if it breaks? Oops!
I mean, we do it with oil. ...At least sort of. Usually the wells are pressurized so pumping isn't a concern, but there's a surprising amount of infrastructure involved down at depth and the maintenance of that infrastructure is significant but largely a solved problem. Obviously economics probably favor it when oil is $75/barrel compared to ~$3 maybe for the fresh water, but still.
Your estimate for the water is way too high. I pay $2 USD (as of today's exchange rates) for a cubic metre of water from my local utility. That works out to about 32 cents per "barrel" of water. A $75 USD barrel of oil is 234 times as expensive as the same amount of water.
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!
At first glance, this suggests typical desalination has a roughly 15% to 23% efficiency. Also, desalination from some sort of submerged membrane and bringing the freshwater to the surface would itself not be 100% efficient.
the single largest consumer of power in california is the DWR's pumping plants. don't underestimate the energy costs of pumping a state's worth of water up several hundred meters.
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 I built an ocean base 231 meters below the surface, does that mean I'd get free fresh water by sticking a membrane on the outside of my base? (Ignoring the impracticality of building an underwater base, of course.)
Almost. You would have to maintain your underwater base at 1atm and you would indeed get free freshwater. The catch is that the internal volume of your underwater base would decrease and you would eventually have to eject wastewater by pushing against the deep sea pressure. Nothing's free in physics!
Pressure (N/m^2) times volumetric flow (m^3/s) equals power (N-m/s). At 231 meters the pressure is ~340 psi or ~6.3 MPa. 1 liter would take ~6.3 kJ to pump.
It seems there is one use case that would be viable.
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.
> If we use the water at depth. I think the way to go is underwater living pods.
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.
Excellent points. We need to add living without nearly as much sunlight, and living in damp or submerged environments to the goals of our Merpeople program.
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.
If you would just build a pipe that goes up to the sea level, wouldn't the fresh water naturally go up it because of pressure enacted at it at 231 meters? You would only need to pump it up from the sea level.
The pressure differential the membrane experiences (and needs to function) drops as the water gets closer to the surface. So the more the pipe filled, the less water would flow.
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.
Haven’t there been experiments with using wave motion to generate electricity? If practical, maybe wave motion at the top could be used to generate electricity for pumps at the bottom.
That is amazing! I’d never thought of leveraging the pressure of ocean depth for this, it’s a great idea. For anyone reading, the energy that OP is talking about would actually force the fresh water above the surface of the ocean without pumps.
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.
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.
So salt combining with water takes energy, and separating it gives off energy. Yet combining happens spontaneously, and separation doesn’t. Because I don’t understand this, it seems like a paradox. What am I missing?
To move to each side of the energy states you need to overcome a hump between. Think electron tunneling. The separated side is the lower energy state. It's just that we don't know a good way to 'tunnel' to that state from the higher energy state in this particular case.
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.
They’re talking about a tiny, tiny portion of the energy balance for one part of the salt in saltwater. The energy needs to actually purify it are far, far greater in practice.
No it isn't. This is just like putting a filter at the bottom of a dam, except the filter also blocks salt. The top of the dam is at sea level, so you have to bring the water back up to the surface.
Adding salt water is endothermic and separating them is exothermic fwiw.
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.
This isn’t a closed system. It’s not perpetual motion, there is an EXTRAORDINARY amount of energy added to the system by the sun.
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”?
“Maths” is the contracted form (https://www.imperial.ac.uk/brand-style-guide/writing/grammar...) of MATHematicS. It had been in use in English-speaking countries since more than a century ago. As a matter of fact, it was also used in the US during the 19th century. Yet, for some curious reason, the Americans had stopped using contractions from some time onwards. So, “maths” became “math” and “PhD” became “Ph.D.”.
I think the justification is that because maths isn't plural in practice (I've never heard anyone say "mathematics are"), it's pointless to retain the s, and only leads to an awkward megasyllable like the end of "wasps."
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."
I think "mathematics are" is a normal construction. "We have a new widget that does this, but the mathematics of mass production are troubling."
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.
That's fair. I was only thinking of it in the context of how mathematics is/are referred to as a subject, not as an actual concept. But what you say is true.
Yet another example of how the American education system is falling behind the rest of the world. Students in the US only learn one kind of math, but apparently the rest of the English speaking world is taught multiple kinds of maths.
Fair, I was being trite. The idea that the ocean is a closed system that doesn’t include all the solar energy, currents, mixing and everything else added to it plus an osmotic membrane would represent a perpetual motion machine just sounded so laughably stupid I was just trying to be equally annoying and dumb.
Not an expert, but from what I understand looking at the paper, the sun is what drives ocean mixing. Without ocean mixing, this method would eventually fully extract all the water out of the ocean water resulting in fresh water oceans on top of a floor of precipitated salt. Once that happened, the osmotic pressure would be exhausted and the system would stop working.
In the absence of the sun (which is what ultimately drives ocean mixing), eventually this would lead to a layer of pure fresh water on top of a layer of salt. The energy is being driven by osmotic pressure of salt water. Once you have extracted the water out of the salt, that pressure is exhausted. Thus it is not perpetual.
Take a long tube with an osmotic filter on it. Put it in the sea with one end out. Pressure is going to fill the tube up, no, just like a snorkel? Probably back up to sea level, possibly minus whatever force reduction caused by the filter? Boom, water filtration with no expenditure of energy.
It may be wrong but it really isn't "obviously delusional."
That's the most common way of collecting drinking water, right? Sun evaporates water from the ocean, then it condenses in clouds, and the clouds rain into a river which we suck the water out of. Boom! Plus you can get electricity out of it.
How much energy does it take to pump it back up from 231 meters, compared to traditional methods? That would be 2.25kJ of energy per liter. Normal desalination I believe is 3kJ per thousand liters.
If you had a 231 meter dam, with a membrane filter at the bottom, fresh water will come out at atmospheric pressure. It then has to be carried back up to sea level. You could power that pump with another hole in the dam, but then the non-sea side of the dam would constantly be filling up with water. Once it's full, there's no longer any pressure difference to drive a pump.
"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. "
It'd be helpful to know the minimal energy requirement to desalinate a gallon of water. With perfect technology, how expensive (in terms of energy) would it be? What's our current level of efficiency?
> Theoretically, about 0.86 kWh of energy is needed to desalinate 1 m3 of salt water (34 500 ppm). This is equivalent to 3 kJ kg-1. The present day desalination plants use 5 to 26 times as much as this theoretical minimum depending on the type of process used.
That translates to about 3.25 watt-hours/gallon as the theoretical limit, if my math is correct.
Depends a lot on what you start with and on some of the other assumptions you make, but for seawater, the theoretical limit is probably ~3 kJ/kg, and the absolute state of the art full scale desalination is probably 11-14 kJ/kg
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.
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.
10 toilet visits a day but only 5 minutes in the shower? Either this is an entire household and it stinks to high heaven in there because no one actually washes themselves, or it's a single person and they need to see a doctor because they're going to the toilet way too much. SO either way, those numbers make no sense.
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".
Cool! Showers are 2gpd minimum, so if you think someone is likely to take a longer shower then you should definitely agree that 82gpd is not "wild", per the post I was replying too. Glad we're in agreement, and thanks for being so polite!
Looking up large metropolitan water suppliers' average water treatment rates and service area sizes, ~80 gallons/person/day does seem to be a reasonable year-round average for total water consumption. (Although note that water usage is deeply seasonal--you might see 2× water consumption in summer as you do in winter).
I need to see a median number because 82 gallons indeed sounds outrageous for a consumer. Unless it is all-in calculation (agriculture + industry + consumers): America uses XXX units of water per year / # Americans.
All comments seem to focus on the cost/energy requirements of the filtration process.. but the elephant in the room is the waste. How to safely dispose off the waste water after filtration completes? That water is virtually useless
Run long tubes (1-3mi) out into then ocean with perforations so you can diffuse the highly salty water back into the ocean without disrupting local ecosystems.
This has the useful side effect that it should prevent the transfer of invasive species in ballast tanks, as most cannot survive high salinity conditions.
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.
Right, islands (and Israel) normally do because there's not the space for a large enough reservoir.
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 article sidesteps something that seems important to my naïve eye: Water is easy to store if you don't have very much of it, so this is the kind of thing you can do when the sun is shining and store for nights and rainy days. Storing water for a year or two would be hard, of course.
Places with intermittent water have lots of water storage in reservoirs. The problem is that reservoirs are up in the hills away from the coast so it would cost a lot to pump it up.
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.
Most of Texas consists of "build a dam at this convenient chokepoint and create a huge reservoir" for its freshwater. So I disagree. We don't do anything special. The biggest issue is invasive species taking up residence in the newly formed reservoirs.
Return on capital and deprecation tend to exceed energy input costs for most plants so it makes sense to run them 24x7x365 rather than over-size them and run them when energy costs are lower.
They tend to exceed energry costs because energy costs are dominated by the cost of purchasing oil, which is as easy to store as water. We're moving away from that now, towards a world where solar power plants produce power at stunningly low prices some of the time (like €0.01114/kWh on the top google hit just now) and those who need a lot of power and can adapt their usage to match solar power plants can make use of those prices.
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".
Solar is cheaper anywhere you get a decent amount of sun. Much of the resistance to solar is not due to cost, it's political: all those places with big coal economies get pissed off when their services are no longer needed, and vote you out of office if you push renewables too hard. Ditto for oil.
I've read that we are starting up use other sources of heat to do desalination projects. There's so many sources of heat that we are just dissipating into the atmosphere. Nuclear or other power plants is an obvious choice.
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.
Although it shouldn't. Adding salt to water is endothermic, it absorbs energy to add salt and releases it to separate them. The article talks about the trouble of breaking the bonds but this is wrong. It's harder to break the na-cl bond to make salt water in the first place.
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.
Solar is cheap when active, and the good news this is one of the cases where intermittency doesn't really matter. We should really explore more use of intermittent power for cases like this where the limited reliability of wind and solar is less significant.
Feels like a problem that will be solved as soon as incentives will be here, and cost of fresh water from other sources depleted or protected. The costs mentioned in this 15 years old article aren't that high in a world where we have to be careful with water.
Question: why is desalinated water costs calculated based on as if the water was immediately thrown back into the ocean? Wouldn't it rather be recycled after once desalinated?
Though there are processes that turn it back into potable water, just reusing it even once in agriculture would bring huge cost savings compared to having to desalinate it again, which is why I wonder why there doesen't seem to be any studies of the realistic likely costs of desalinated water when accounting for reasonable reuse
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?
Why not using the sun to evaporate it, then collect the salt?
Temperature have risen in the last 15 years, unless one wants to extract water only by desalination, it should be feasible, and could at least help less densely populated areas near the sea. Maintenance aside, energy costs would be negligible.
Knowing that the vast majority of water use is not the water flowing to homes for drinking, plants and washing, the government (local or federal) could subsidize it for individuals while taxing industrial water consumers.
As mentioned in another post. Basic utilities can easily become affordable with proper regulation.
If you want anything to be economical or "worth it," you create the conditions where you are providing something to external parties, and the money will come in to sustain it. The economics of desalination are trivially viable if you can set up a stable financial regulatory environment in the region that has competitive taxation internationally.
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.
Same in Australia - you've got a very wealthy population, living on the coastal outskirts of a wind/solar/coal heavy desert. Basically the perfect combo for desalination.
The coastal areas of Australia have literally some of the highest rainfall anywhere in the world. Sydney has more annual rainfall than 'rainy' Seattle or London.
For Australia the correct thing is to store the damn (or should I say dam) water that falls where people live.
I imagine agriculture, but wow, I knew Australia's population was mostly coastal, but I looked it up and out on the 25 biggest Australian cities, only Canberra is inland.
I wonder how much it would cost in electricity to run a current through salt water to produce hydrogen and oxygen, then run the hydrogen through a hydrogen powered generator to recover most of the electricity and the fresh water byproduct?
Are state of the art systems more efficient than the ion-pumps in cell membranes?
I remember reading about light driven sodium and chloride pumps, if we could make these transport ions across some biomembrane we could desalinate water.
We do in some places. But in other places like California NIMBYs and greens decided putting extra salty brine back into the ocean was worse than taking fresh water run off from the inland, worsening desertification
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?
From a cursory search, the greens have lost their bite simply because there isn't an alternative. Water supplies are drying up and the alternatives would end up being losing political power.
The state approved 3 new plants this year alone and more are coming.
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.
Usually a combination of calcium carbonate (or bicarbonate for solubility), calcium chloride, magnesium chloride, and or the sulfate versions of the chlorides.
I mean, we probably could extract industrially useful chlorine and sodium from it, if sodium batteries ever actually take off as a lithium replacement that could be extremely viable.
Qatar has no groundwater or surface water anymore AIUI. But they have an incredible oversupply of natural gas that they can’t build enough export capacity for. So it mashes sense to use the gas they can’t export to desalinate water, and they do.
I don't know about exports but for certain there's quite a lot of water Israel transfers to Jordan as part of the 90s peace accords. That's a huge deal in the Mid East.
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.
It's not a matter of greed as you seem to be implying. In this case, the money is really just a proxy for how practically difficult desalinazation is vs. the alternatives. It's the same reason why we don't ship parcels via ICBM; the alternatives are way easier on multiple dimensions. The juice isn't worth the squeeze.
In this case, that's not really the issue. Yes, the issue is money, but it's not as nefarious and cynical as you make it sound. People don't want desalination, they want fresh water. If there are cheaper ways to meet water demand than desalination -- which is currently the case for most (but not all) places in the world -- then there's no need for desalination. Certainly as water scarcity becomes more of a problem, we'll have to re-evaluate this situation, and at some point desalination may end up being competitive with the alternatives.
We also might find more efficient (cheaper) ways to do desalination, which could tip the scales toward it earlier.
That's exactly how money works. People want it, so they cut corners and/or hoard it instead of being generous with it. Printing money would just mean someone would hoard the printed money (which, as you can see, already happens).
Collecting money is just a side-effect of people being selfish.
"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."
New technology is making it easier and cheaper. There's also the fact that environmentalist suppression of nuclear power has made electricity much costlier, intermittent, and much less reliable.
It's surprisingly difficult to separate salt from water to the point that it's drinkable. That difficulty translates to it being very costly and that cost is so prohibitive that most places will choose another option. Like even building massive pipelines to transport water across 1000's of kilometers is probably going to be a better option. It's pretty much always going to be more economical to use the water that the earth is naturally desalinating for us.
Actually it's quite cheap, and Israel does it at scale, among other places.
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.
Though the southwest is a great place to farm if you have the water to leverage the sun and the relative dearth of pests. Given the economic potential of a huge fraction of the country, I'd wager that getting water there will be worthwhile within my lifetime.
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.
> Though the southwest is a great place to farm if you have the water to leverage the sun and the relative dearth of pests. Given the economic potential of a huge fraction of the country, I'd wager that getting water there will be worthwhile within my lifetime.
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.
It's true, but that'll take quite a long time and the advantage is unlikely to evaporate completely even if it erodes. And there's probably no amount of water use that humans can realistically achieve in that same time period which will take away the sunlight.
That's exactly the problem, though, no? If you keep raising the prices, then at some point desalination will be an attractive option.
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.
Not nothing or nominal, but cheap enough that it is feasible, and about the same as other options. We also recycle 80% of the water, first in the world. The second-place country does 15%,
Recycle to the point of making it potable again, or recycle for other uses, like agricultural? If the former, that is truly a wonderful achievement. (Even the latter is pretty great, though!)
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.