Desalination system could produce fresh water that is cheaper than tap water
eurekalert.org
eurekalert.org
On a sunny day, total solar energy hitting the top of the atmosphere gives about 1360 watts per square meter (source - top result from google, something something NASA). It takes about 4.184 joules to raise one ml of water by 1 degree celsius. Let's suppose that the "suitcase" proposed in the article has 1 square meter of space (a pretty large suitcase) and is able to capture 100 percent of solar energy (unreasonably effective). Then pure solar energy-wise, there is enough energy to raise 325 ml of water by one degree of celsius per second in a square meter. If the water is, say, at 16 degrees (the temperature of the ocean near me), in would take 84 seconds to bring 325 ml of water to boiling temperature. To transform boiling water to steam, each ml of water takes an additional 2257 joules. In 540 seconds, the 325 ml of water is now converted to steam.
In total, it has taken 624 seconds to steamify 325 ml of water (under very optimistic circumstances). Morally one could do this almost 6 times in an hour, giving approximately 2 litres of water per hour.
(Edit): Looking a bit closer, I see that the article's description of their work suggests that they recapture some of the energy from condensing the steam back into water. I didn't account for this. Even a moderate amount of recapture changes the math very favorably.
This makes me suspect that their claim of 4-6 liters per hour would require a rather large "suitcase"-sized device, but is within the ballpark of reason.
> if each stage were scaled up to a square meter, it would produce up to 5 liters of drinking water per hour
so 1m², times the number of layers.
What would the math look like if they aren't necessarily going to boil?
[1] https://www.sciencedirect.com/science/article/abs/pii/S13594...
Edit: If you're thinking of something like an ultrasonic humidifier, I don't think these actually evaporate the water[2]. The mist these produce would still contain salt if you tried to use them for desalination.
[2] https://en.wikipedia.org/wiki/Humidifier#Ultrasonic_humidifi...
Aside:
I have a home-built ultrasonic humidifier. If I run it with Boulder, CO tap water that is low in TDS, it only takes a day or so to have a PM2.5 >600 in my house. For this to work I had to install an RO filter in order to humidify with ultrasonic and not degrade air quality.
I didn't know that legionella can kill macrophages from the inside. That's nasty.
Of course on the flip side, your goal is fresh liquid water, so you need to condense the vapor. Condensing hot vapor is easy, just expose it to cooler ambient conditions. Condensing ambient vapor is harder, and will require you to run something like a refrigeration cycle or a chemical desiccant system which will need energy to be regenerated.
Most commercial systems use vacuum distillation which boils water at low temperatures and pressures, which has its own drawbacks but is generally more efficient.
You are incorrect that at ambient temperature the lower energy bound is set by the latent heat of vaporisation, as others have pointed out this is theoretically recoverable.
At ambient temperature there is however still a fundamental physical limit: the solvation energy of the salt in the water: https://en.wikipedia.org/wiki/Solvation#Solvation_energy_and...
Now the whole globe does not have the same ambient temperature, and as you know about global warming it would be great to shed some energy in the form of heat.
There are many forms of desalination. Another way to desalinate is freezing: when salty water freezes, it pushes out the salt, so while desalinated water ice forms, the liquid water surrounding the ice will increase in salinity and become brine. One could then use simple nets or grills to separate ice from brine.
Suppose one has a space elevator, or even a tether from a balloon, but capable of carrying significant weight.
The temperature falls roughly adiabatically with height. Above the tropopause the atmosphere is essentially cloud-free, CO2 free and below freezing point (say -60 deg C). Hence the latent heat of fusion (freezing) can be shed to outer space. So it should be possible to lift salty water up an elevator, allow it to freeze over, separate brine from ice at the top, then lower the separated brine and ice.
The energy required to lift the brackish water is compensated by the energy released by lowering the freeze-distilled water and brine. What comes up must go down, so simplistically speaking a pulley in equilibrium, so that the only energy intentionally exerted is lost to pulley and air friction. Then one would be cooling the planet and receiving frozen freeze-distilled water at the same time.
The law of conservation of misery is typically not a fundamental law of nature, but imposed by reluctance to study of those who dictate artificial laws.
With regard to the energy expenditure for reaching that temperature: if we were merely raising the temperature of the water and then cooling it down again, I think it would be correct to say that with a completely efficient contra-flow heat exchanger, perfect insulation, and no pumping losses, the steady-state heat input could be arbitrarily low.
If we now modify this system to evaporate and then condense some of the water at the point of highest temperature, we would have to supply, and then extract, the latent heat at whatever temperature the evaporation is performed at. Once that has been performed, the outflow would comprise of the same amount of water as before (and at the same temperature), and it would be equally available to warm up the incoming stream as in the initial scenario (though now we would need two heat exchangers in order to keep the fresh water separate.)
Of course, both the heat exchanger and the insulation will have losses, but we are rejecting quite a bit of heat in the condenser, and it is at the highest temperature in the system. Would that, in principle, be available to make up for any losses elsewhere? This makes me wonder if, counter-intuitively, it could be more efficient to do the distillation at higher temperatures, at least up to the point where the diminishing latent heat can no longer compensate for the losses of running at a higher temperature?
I'm leaving out some considerations that I don't know how to handle (and probably others that have not occurred to me.) For one thing, there's the question of what happens if the evaporation occurs into a chamber containing some air, rather than just steam (my guess is that the relevant temperature is determined by the water vapor partial pressure.) For another, what difference does having salt dissolved in the water make? And this may all be moot, as this system has no moving parts, so the pressure is probably atmospheric (or somewhat below, if the condensation can be exploited to create a partial vacuum.)
I have no idea if any of this makes the slightest bit of sense, and it's probably wrong - as you say, most systems run at reduced pressure.
[1] https://www.engineeringtoolbox.com/water-properties-d_1573.h...
With perfect insulation and heat recovery (zero loss) all that matters is the change in entropy between the starting and end products. Both the energy for raising the temperature and for the vaporization is theoretically recoverable (when you condense a vapor back to a liquid it releases the same amount of heat that it took to vaporize it). But you can't have perfect insulation and heat recovery in practice, and the losses become worse with increasing temperature - or more accurately increasing temperature difference, so trying to cool things down below ambient won't help you either.
I Don't think that can be right - for example, at 18 °C, the isobaric specific heat of water is 4.18 kJ/(kg.K), while the rate of change of the latent heat with temperature is only 2.4 kJ/(kg.K), and at 100 °C, the figures are 4.22 kJ/(kg.K) and 2.7 kJ/(kg.K) respectively.
> Both the energy for raising the temperature and for the vaporization is theoretically recoverable (when you condense a vapor back to a liquid it releases the same amount of heat that it took to vaporize it).
Only up to a point: you cannot condense steam at 100 °C in a condenser where the incoming coolant is also at 100 °C. Using only passive methods (heat exchangers) you cannot, even assuming perfect efficiency, recover all of the heat needed in a distillation process for reuse within that distillation process.
While distilling at higher temperatures need not be anywhere near as inefficient as it seems if you don't include the use of heat exchangers, the numbers given above don't seem different enough to justify distilling at a higher temperature than necessary, under realistic assumptions of efficiency, which is not surprising, given that it does not seem to be done.
You use the cold incoming water to condense the hot vapor, thus pre-heating it prior to distillation. You get out all the heat you put in, the issue is that vapor has higher entropy than liquid water so you can't use that heat efficiently enough to vaporize the same quantity of water. That's in the efficiency term we are handwaving away.
If it works less well on cool days, well you don't need as much water on cool days as you do on hot ones.
There are definitely efficiencies to be had, though I don't know enough of the math to judge one vs. the other. During my brief patent career, I wrote the patents for a distillation system where the main elements involved heating water that was distributed across rotating blades (heat + surface area + air movement) to evaporate the water. When the water was collected, it passed through a heat exchanger that exchanged heat with the in-flowing water. The result was a very efficient system on a small scale, at least.
*edit: although window and wall unit HVAC use the blades to fling water around so the condenser gets the coolest possible air
Essentially, they find an equilibrium between the cold water coming in, warming in the sun, an increasing amount evaporating into the warm, damp chamber, and the remaining brackish water being cooled by the new water.
Aren't they all sunny at the top of the atmosphere?
> gives about 1360 watts per square meter
I assume that's very much latitude dependent
There’s also more atmosphere in the way the further you go from the equator which will affect how much solar radiation reaches the earth. Overall only about half of solar radiation reaches the surface.
If heating water is the goal then going directly to heating the water is more than 4x the power capture of a solar panel. Dropping one solar panel on your roof for a water heater pays off its just that the solar heaters are kind of expensive dealing with all the other aspects, like if the pump fails or its too cold and the water would freeze etc etc. Those other aspects are probably going to dominate the complexity and cost of the devices.
(Not affiliated, no idea if that particular one is any good, it was just one of the first results)
A solar thermal heater typically lasts 10 years, its a pretty harsh environment and they have pumps and expansion vessels and water in the heat range of -25 through +80 C is just damaging over time. Where as a solar panel has a rated 80% output at 25 years. That mismatch is problematic for Solar panel payoff, 10 years is only just past break even point. Whereas the solar thermal heaters typically pay off within a few years so the reduced lifetime isn't such a big problem (but both are driven by local gas and electrical prices).
Companies are trying to do this better and products exist to do it. The added installation complexity and reduced expected lifetime are all a bit of an issue. Currently I suspect most people are better off with a dedicated solar heater and solar panels separately, at least for now until the water channels in the panels at least are reliable enough that they meet the panel lifetime and then the pump is installed in the roof cavity so its cheap and easy to replace. Work still needs to be done to work out the details and make the parts that fail easily swappable.
Right now most people are better off (from a total cost of ownership perspective) with PV panels + heat pump water heater. The latter can achieve a COP of 3.0 (300% "efficiency"), and also can just use grid electricity on a cloudy day. Unless you are off-grid, the additional cost/complexity of running plumbing to the roof for a solar water heater doesn't pencil out.
Some premium hot water heaters like the SanCO2 can achieve COP of up to 5.0 [2], so high that they don't need backup resistance elements, even in northern climates.
1. https://www.energystar.gov/productfinder/product/certified-w...
2. https://www.smallplanetsupply.com/small-planet-blog/2021/1/7...
It would be really nice if manufacturers published delta-T vs COP curves.
They use concentrated PV to generate electricity directly, and the cooling water goes into a pond (with insulation on top) that reaches ~90C. They also have a “cool pond” cooled using a heat pump to just above freezing.
The combination of the heat and cold reservoirs are used to run a turbine with a low boiling point fluid.
Obviously with the low temperature differentials it’s not terribly thermally efficient, but the proponents claimed the cost of electricity combined with the storage will make it viable in sunny locations.
Doesn't feel like there is a gross thermodynamic reason it wouldn't work.
4 to 6 liters is 5-8% of that.
5-8% of 1200 watts is 60-96 watts.
If you remember the numbers right, that thing is already roughly in this range. A 100 watt solar panel might fold into a briefcase.
The steam is very hot, and the condensed fresh water is also pretty hot. You can use a heat exchanger to transfer this heat into your 16°C ocean water, preheating it so the sun doesn't have to do all the work.
This wouldn't mean magically getting free energy. Your output fresh water would otherwise be really hot, and that's where the energy comes from.
Obviously there are limits. If you have 100°C fresh water coming out and 16°C ocean water going in, a heat exchanger will at best average their temperatures to 58°C. You could in theory overcome this with a heat pump, but that's pretty elaborate.
(I'm not trying to design the perfect desalination system here. The point is there may be some easy efficiency wins.)
According to GPT4, the numbers come out to 760 J/L for seawater with a salt concentration of 35 g/L. That would mean a limit of around 2 L/s*m2 for full intensity sunlight.
Part of my idea is to use desalinated water to build artificial lakes and rivers. Specifically, a river system along interstate highways, especially in the US west and alongside that infra build highspeed railways. These two things along with interstate highway will allow new towns and cities to flourish which will help with economic activity recouping some of the cost but also solve homelessness, climate goals and even social unrest and instability. It passed my poorly done napkin math.
If hitler had plans to dam the mediterranean and turn the sahara into an fertile land and generate crapton of energy wth are we doing today with all the peace, economic health and insane amounts of technical progress? $300B in subsidizing ev car chargers (car makers should pay for) instead of high speed railways makes me sad.
In Melbourne, Australia, since tap water mostly comes from catchments in national parks, water requires very little treatment (some fluoride and chlorine is added), so it works out cheap: ~$25 AUD per million liters. Desalinated water, by contrast, cost about 24 times more (~$600 AUD per million liters).
from the historical net loss rate approaching the lows one can estimate the required backup desalination flow rate.
For human consumption: this is pretty much true. Desalinization works just fine for people. The biggest issue is where to put the extra salty waste products.
When people talk about the "water crisis" in the US, for example, it's always about big agribusinesses doing farming.
The U.S. has "salt farms" where they evaporate water to produce salt. Sounds like colocating near the desalination plant would make those cheaper to operate.
I know I would.
Yes, you'll never have to worry about your basic supply of 50 gal/d/person being threatened in a drought, but just think about this for a second: the population of Melbourne is around 5 million people. In the 2020-2021 year, Melbourne Water delivered 439 billion liters (116 billion gallons) of fresh water[1]. That is roughly 318 million gallons of water consumption on an average day. What kind of drought would reduce the available water from 318 million gallons to 25 million gallons per day?
Personal consumption (drinking, showering, household washing) is not the primary driver of water use. In general, it is dominated by agriculture, and to a lesser extent by industry. The economics of these activities would not permit an order of magnitude increase in the cost of fresh water.
Australia uses a estimated ~16T liters of water per year [1] for all uses including personal and agricultural. That is 16M ML * 600 AUD/ML for a total of ~10B AUD.
Australia has a population of ~25M. So that is ~400 AUD/person to completely replace all water usage in Australia. As Australia is a island, I assume they do most of their own agriculture, so for additional 400 AUD on their food bill a year they never need to worry about a drought ever again.
The Australian government appears to have a budget of ~500B/year which is around 25% of GDP [2]. So, for ~2% of the government budget or ~0.5% of GDP the economics are completely managed.
[1] https://www.worldometers.info/water/
[2] https://www.aph.gov.au/About_Parliament/Parliamentary_Depart...
You can see the numbers don't match up; you're using a figure of 16T liters annually, whereas 25 million people * 50 gallons / day-person * 365 days * 3.785 liters/gallon is 1.727T trillion liters annually.
Anyway, I am suspicious of the 600 AUD/ML figure, or else a lot more Gulf states would be food independent.
600 AUD/ML is ~400 USD/ML. The Sorek B plant in Israel is profitably contracted at ~0.40 USD/m^3 [1] which is comparable. That is one of the largest plants with cutting edge technology and one of the cheapest prices I have seen in my research. A quote of 600 AUD/ML for desalinated water right now in Australia seems a tad questionable, but not outside of what is possible. 2-3x that number is almost certainly believable (though they almost certainly do not have bulk scale) and would only increase the costs to 1.5% of GDP.
The cost of simply keeping it turned off is $500,000 a day.
Simply building bigger dam walls would be a far better choice.
Raising the few dam walls that service Sydney is nowhere near the same cost but people are very angry about it ever happening because it would basically remove entire flood zones from the planning maps and encourage development in their areas.
How? I don't understand what that money is being spent on.
Go on then.
Yet another MIT paper on desalination jumping the gun and announcing a breakthrough, that could be scaled up to modestly useful sizes if only they had the time and the meagre budget to do so.
Here’s[1] a previous announcement from Feb 2022 of a device that could produce water for a small family for only $4 of materials, that they didn’t bother building.
[1] https://news.mit.edu/2022/solar-desalination-system-inexpens...
Specialization is great, glad someone is focused on continually pushing the research and improving the designs, and this one supposedly improves on last year's design. There are others who are better at scaling & commercializing, and those types are probably a lot worse at basic research.
Every inventor and researcher doesn't need to start a startup.
Are there thermodynamic limits to how efficiently water can be desalinated?
Doesn't this feel like a problem where a Carnot-like argument can be made?
PV-driven RO, even without energy recovery, is going to produce much more water than this scheme.
Kind of analogous to ICE vs electric cars; electric cars are simpler in principle but the most important components require access to advanced semiconductor and battery manufacturing, while all the components, in theory, of an ideal "ICE car" can be recreated with early 20th century machine shop technology
https://en.wikipedia.org/wiki/History_of_the_electric_vehicl...
Desalination has a fundamental energy cost, and solar energy is fundamentally limited by what is received. The real question is whether it is cheaper to set up a solar-thermal desalinator, or set up solar panels that can power more efficient desalination methods.
Solar panels are cheap and getting cheaper quickly as there is an incredible economy of scale. While desalination systems could likewise be mass produced, there will never be as large a demand for that one specific application of solar power as for general solar power. Further, photovoltaics are reasonably simple solid state devices which are well suited to mass production. I am highly skeptical a priori that a solar thermal system could compete on economic terms. Perhaps in a space confined situation it makes sense, but it's tough to run out of space in the ocean.
Seems like it uses energy from the sun, but also requires a location with ocean currents. So finding good installation locations along the shoreline where it is both deep enough to work while being shallow enough to maintain may be a limit on how much capacity you could have.
Hopefully they are able to try a scaled up version in a LESS controlled environment to see if additional problems arise.
> From these tests, the researchers calculated that if each stage were scaled up to a square meter, it would produce up to 5 liters of drinking water per hour
So 1) They haven't yet tried this at the scale of one square meter. So this is a lab project that is nowhere close to commercialization but that doesn't stop them from making grand vague pronouncements about its potential. Classic MIT tbqh.
2) 5 liters per square meter per hour is trash. An average American uses a bit more than 300 liters of water a day, so you need 60 square meters of this to support one average American. So you'd need more than 5000 square kilometers of this to provide water to NYC. Does this sound like it's going to be cheaper than the tap water they already have?
Unit check. 5 liters per hour is 120 liters per day. So you need 2.5 m^2 per American (ignoring whether the hourly rate is sustainable, just correcting units).
This is about a third of the projected area of a typical car, so in terms of surface-area-per-person we're at about half that of cars (given about 2/3 of a car per American).
Here is one for sale: https://www.jains.com/Pipefittings/JainPEPipes/spacial%20fit...
Even if 100% of grey water runoff is mixed with the brine, the resulting concentration is still high enough to cause a localized collapse in the ocean if it isn't properly regulated.
Brine > Uses: https://en.wikipedia.org/wiki/Brine :
> Culinary, Chlorine generation, Refrigerating fluid, Water softening and purification, De-icing, Quenching
Uses for Brine / NaCl not listed on Wikipedia:
Hypochlorite generation. Hypochlorite is the sanitizing primary component of household bleach. Hypochlorite can be made with a 5V USB Hypochlorite generator, salt, water, and watts of electricity.
Salt-based cleaning products; "Non-Toxic Cleaners and EPA Disinfectants" https://saltbased.com/
Energy storage; thermal battery (as heated by concentrated solar, for example)
Energy storage; /? brine NaCl batteries:
Sodium-ion Battery: https://en.wikipedia.org/wiki/Sodium-ion_battery
/? Proton battery brine / sodium
Not brine, but if you're already processing seawater:
Diesel can be made by processing lots of seawater
Hydrolysis and Electrolysis; [Green] Hydrogen production
Nuclear Fusion; to extract D, T, He3, and He4 from (Helion,)
What can be made with Brine and/or NaCl with modern sustainable production processes involving e.g. lasers and fusion heat?
Salt belt: https://en.wikipedia.org/wiki/Salt_Belt :
> The Salt Belt is the U.S. region in which road salt is used in winter to control snow and ice.
Nebraska roadways are treated with brine to pre-treat and de-ice roadways (instead of rock salt, which corrodes many metals).
Though listed as a DIY weed killer ingredient, sodium is a dessicant which dries and prevents plant growth, so salt on the lawn will kill weeds but then leave a dead patch.
Does discharge of fresh water into the ocean by desalination plants, for example, affect the thermal content of the water due to formation of halocines and other thermochemical effects?
Solar pond: https://en.wikipedia.org/wiki/Solar_pond :
> A solar pond is a pool of saltwater which collects and stores solar thermal energy. The saltwater naturally forms a vertical salinity gradient also known as a "halocline", in which low-salinity water floats on top of high-salinity water.
But yes. You’ve hit on the one of the absurdities of the headline: drinking water costs vary wildly based on a large number of factors including the source and treatments.
This seems like it would be extremely useful if it pans out.
We see these articles all the time, and they somehow don't get scaled up. You'd think they'd at least scale this up to the size of a typical rooftop solar panel before issuing a press release. So what's the problem? Uses some expensive material? Hard to fabricate at scale? Doesn't actually hold up in bright sunlight?
Go back and read their previous "breakthrough announcement" from 2020.[1] That has more useful info. That system used some expensive aerogel. The process is a bit clearer, During the daytime it evaporates salt water and condenses the vapor. During the night it back-washes the wicking material. Whether this can actually work with some simple device floating in a pool of salt water is not clear. The experimental systems all have plumbing, pumps, and instrumentation.
If this is for real, please scale it up to at least kiddie-pool size before turning on the PR department.
[1] https://news.mit.edu/2020/passive-solar-powered-water-desali...
oh, you had a clever idea, but can't do anything practical with it? here's your gold star. now go have some milk and cookies and get ready for your nap.
We saw with LK99 the world rally around a promising lead and discover some interesting things very quickly. Why not run these kinds of science/eng research problems like we do open source projects?
Having good desal is an incredibly important problem that should inspire this kind of collective action. It's not super esoteric research.
Relatedly, Howard energy efficiency be affected if you didn't heat the water to be desalinated, but just evaporated it using low pressure? Would it be less, more, or equally efficient than using heat alone?
Article doesn't mention how this part would work. Peltier cooler? Heat pump? Is that included in the "suitcase sized" concept? What powers it?
The average American uses 82 gallons of water a day.
Assuming 10 hours of sunlight, that requires 8-12 of these per American.
I wonder how practical that is?
We also shouldn’t forget that after disposing of the water, the local municipality can recycle it! For island nations, a few strategic water reserves could be cleaned and stored for future use.
And then obviously, for more developing nations, they already use a lot of grey water for daily activities, so this becomes a source of consistent clean drinking water.
It would be great if they can scale it up and make it widely available
https://svalbardi.com/blogs/water/distilled-safety
A casual application of math to the concentrations of minerals in tap water would show you that simply eating vegetables would provide much more in the way of minerals (namely calcium and magnesium). If you drink 2L of 60mg/L Ca and 25mg/L Mg, that's only 12% daily value.
"Unsafe to drink DI water" is a myth. If your diet is that marginal that +/-12% matters, take a supplement.
Bombastic.
> It looks like they're creating distilled water.
"distilled water" can mean many similar things. It is not a binary property of water:
Consider a water still that has 3 ports: one intake port of seawater, an output port of brine and an output port of water with a lower salt concentration than seawater.
Distilled can in this case refer to the water exiting the third port, even though it still contains some salts.
Distillation and purification in general is a process with diminishing returns: to get ever lower ppm's of mineral content requires ever more patience or energy.
In the context of seawater desalination, "distilled water" typically means water with sufficient salt removed to be now potable. Either way even if the third port was effectively Sigma-Aldrich 100% pure H20, the simple fix would be to dilute a tiny amount of the brine into the distilled water to restore the mineral content to potable levels.
You did not reference the study or page of the supposed WHO conclusion.
When I was studying at university I recalled the concensus basically being that the adverse health effects are a myth, since 95% of our salt intake comes from food.
Remember sailors have been drinking distilled water for over a hundred years.
Steamboats needed the ability to desalinate water anyway.
It is quite conceivable, that this myth starts as a counter-myth for a prior myth.
Scientifically different types of desalinated, deionized and distilled waters are closer to pure H2O than normal waters.
Linguistically pure is the antonym of impure.
The mere existence of distilled or pure water in the scientific literature conceivably caused purity zealots to opt for drinking distilled waters, falsely claiming health benefits.
Just like taking 10x vitamin C doses will not make you 10x healthier, neither would drinking distilled water. But it "sounds" purer.
In order to counteract obsessions about drinking distilled water, and to counter the false and disinformative claims of health benefits, some started opting to use the same tactics and weapons to stop the "pure water zealots", and the countery-myth is born.
That was my interpretation at university. So it surprises me to learn that WHO would recommend against drinking distilled water.
Of course only drinking distilled water would not be healthy indeed: you also need to eat, breathe, etc.
So I first did the easy check: wikipedia.
On wikipedia the same vague statement of the WHO concluding something along the lines of it being unhealthy is reiterated, but with a [citation needed] appended. Recall anyone can edit wikipedia. Such citation was never provided.
So next I tried to find the source myself, and downloaded the 312 page Drinking Water and Health: Volume 4 1982.
What page am I supposed to be looking at?
As I said at the start, its a non problem, because adding back in some mineral salts to the desired ppm is easy to do.
If you eat a normal diet, the minerals lost in distilled water are a faction of what you consume with your food.
If they could build platforms in the ocean with some way to get the water to land, maybe this could work, but the Western US is screwed unless we can find other ways to save water, even if this tech were totally free.
https://www.google.com/maps/place/Claude+%22Bud%22+Lewis+Car...
That's only if you intend to supply 100% of water from desal, which nobody is suggesting.