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California Startup Hopes to Harvest Desalinated Drinking Water from the Ocean Floor (yahoo.com) 135

Posted by EditorDavid from the sea-no-evil dept.
A startup named OceanWell has partnered with southern California's Las Virgenes Municipal Water District "to study the feasibility of harvesting drinking water from desalination pods placed on the ocean floor," reports the Los Angeles Times: The company says that by combining desalination with off-shore energy technology, it can solve many of the challenges associated with traditional, land-based desalination, including high energy costs and salty byproducts that threaten marine life. The process could produce as much as 10 million gallons of fresh water per day — a significant gain for an inland district almost entirely reliant on imported supplies...

OceanWell says its technology can use up to 40% less energy by harvesting the water in pods placed at depths of about 1,400 feet, where naturally immense water pressure can help power the filtration process... Land-based facilities try to squeeze out as much freshwater as possible to help balance high energy costs, with typical targets of 50% freshwater and 50% brine from every gallon processed. But because OceanWell uses "free" pressure from the ocean, it can operate at a lower recovery rate of 10% to 15%, producing a much less salty byproduct that can be dissolved back into ambient conditions within seconds, she said...

The partnership with Las Virgenes will allow OceanWell to "stress test" the technology's capabilities in the reservoir and collect more data, said Kalyn Simon, OceanWell's director of engagement. The current goal is to be fully operational by 2028, producing an estimated 10 million gallons of freshwater per day.
Thanks to Slashdot reader Bruce66423 for sharing the article.
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California Startup Hopes to Harvest Desalinated Drinking Water from the Ocean Floor More

California Startup Hopes to Harvest Desalinated Drinking Water from the Ocean Floor

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  • Why NOT? (Score:3)

    by redelm ( 54142 ) on Saturday September 23, 2023 @04:43PM (#63871897) Homepage

    I haven't done the calcs to determine whether 1400 ft of seawater is enough to power the membrane and the freshwater lift but it seems likely. The modules wouldn't need external power but would only be viable if placed in a deep current to carry away the brine. You might be able to power a brine turbine/backwash from the lift.

    • Re:Why NOT? (Score:5, Funny)

      by ShanghaiBill ( 739463 ) on Saturday September 23, 2023 @05:41PM (#63871971)

      TANSTAAFL. The energy needed to push the pods to depth is no different than the energy needed to pressurize the water at sea level.

      10 million gallons is 31 acre-feet. At $70 per acre-foot, that's $2170.

      It might be easier to just stop growing subsidized rice in the desert.

      • "Push"
        Uh... lead and scrap iron ballast to get it to the sea floor is pretty fucking cheap, and they then pipe it out, not raise the pods to the surface every time they want to harvest water.

        • Re:Why NOT? (Score:4, Insightful)

          by ShanghaiBill ( 739463 ) on Saturday September 23, 2023 @08:27PM (#63872167)

          "Piping it out" will take the same energy as pushing it through a traditional osmotic membrane.

          It takes energy to separate salt from water. You can't magic that away.

          The pressure drop, and the energy needed, are the same either way.

          • Um... no. Just... no. The vast majority of the energy to pump the water out to the surface will come from the weight of the ocean itself, which won't deplete in any meaningful fashion no matter how much water on the scale of human consumption is pumped out.

            • Re:Why NOT? (Score:4, Informative)

              by ShanghaiBill ( 739463 ) on Saturday September 23, 2023 @09:19PM (#63872247)

              The pressure from the seawater is expended pushing through the osmotic membrane.

              Then you need to lift the desalinated water 1400 feet (427 meters).

              Pushing the water through a membrane takes 0.833 kwh per tonne.

              Lifting water 427 meters takes 427 * 9.91 * 1000 / 3600000 = 1.16 kwh.

              There will be some pump inefficiencies in either process, but they are roughly the same.

              Even TFA doesn't claim magical free energy. Oceanwell claims the savings come from a lower salinity differential. But you could do that on the surface.

              • Then you need to lift the desalinated water 1400 feet (427 meters).

                Good news, the water pressure will help with that as well! A water pump with a lift 1 foot above the water will use about the same amount of energy for the same amount of water whether the inlet is 1 foot below the water (total 2 feet) or 10 feet(total 11). The deeper one may take a bit more juice from the friction of the increased length of the tube.

                pumping head height [creativepumps.com.au]

                Note that they measure head from the water's surface, not the pump's location or the inlet location.

                That said, reducing pumping cost means

                • Re:Why NOT? (Score:4, Informative)

                  by ShanghaiBill ( 739463 ) on Saturday September 23, 2023 @10:30PM (#63872317)

                  Good news, the water pressure will help with that as well!

                  There is no "water pressure". The pressure is expended going through the membrane against osmosis. So you have freshwater 1400 feet down with no pressure to push it up.

                  I think you are somehow envisioning a pipe full of fresh water rising to the surface where you can ladle it out with no work. It doesn't work that way.

                  Reverse osmosis has a static pressure differential of 600 psi. Even more is needed for a reasonable flow rate. That's 40 Atms. Each atm is 10 meters. So 400 meters or about 1400 feet.

                  That will be the depth of the freshwater's surface. To move it any higher, you need pumps.

                  The good news is, if you have plenty of freshwater, say from a river entering the ocean, you can run the process in reverse. You can send freshwater down the hole, generate electricity from a 1200-foot drop (twice the head of Hoover Dam), and have the freshwater pass through the membrane at the bottom and into the ocean. You can do even better if the sink is brine instead of seawater, such as the Great Salt Lake or the Dead Sea.

                  • Re: (Score:2)

                    by gweihir ( 88907 )

                    Reverse osmosis has a static pressure differential of 600 psi. Even more is needed for a reasonable flow rate. That's 40 Atms. Each atm is 10 meters. So 400 meters or about 1400 feet.

                    That will be the depth of the freshwater's surface. To move it any higher, you need pumps.

                    Indeed. Yes, you can do the osmosis "without" energy down there (if you already have an empty, cavity for the freshwater to go to), but you need to remove the fresh water up those 400m and hence you pay the full cost there. Well, since you are only pumping fresh water, you can use cheaper and possibly a bit more efficient pumps and you get a tiny advantage because freshwater is a tiny bit lighter. But overall, I just do not see it. I also expect everything you save on saltwater resistant pumps, you pay in m

                  • First the river has to reach the ocean, like the Colorado doesn't any more for example.

              • Re: (Score:2)

                by gweihir ( 88907 )

                Oceanwell claims the savings come from a lower salinity differential. But you could do that on the surface.

                Indeed. They also claim the brine created will just "dissolve". Unless they make sure there is a permanent water current, that is not going to happen. This whole thing looks like a scam to me.

              • You'd have to pump the water to land based plant and then pump it out that might leave room for the overall savings on doing the pressure down low.

              • Re: (Score:2)

                by ls671 ( 1122017 )

                Then you need to lift the desalinated water 1400 feet (427 meters).

                My guess is that the desalinated drinking water would come to the surface by itself since it has a lower density. I see no need to pump anything up at first glance, it will lift naturally all by itself.

            • OMFG you just invented the perpetuum mobile. Just drop something in the water and continuous free energy, why did nobody think of that before.

              Problem: thermodynamics, if only we had technology that could circumvent that, weâ(TM)d have free energy forever.

          • Re: (Score:2)

            by ceoyoyo ( 59147 )

            Fresh water floats.

            They're not claiming its energy free. From the summary: "combining desalination with off-shore energy technology."

            • The inside of a pipe is a closed system -- there is nothing in the pipe for the freshwater to "float" on. Sure, the whole pipe might float to the surface if allowed, but that kind of defeats the point.

      • By the time it reaches us, through at least... what? Five layers of scrutiny? Something that obvious would have been caught. It's much more likely that this is just an oversimplified description, and perhaps misrepresentative. That's usually how science reporting works.

        • TFS is poorly written but says the main benefit is a lower salinity differential.

          It does not say there is free energy from avoiding pumping (because there isn't). Many Slashdotters read it that way, but TFS didn't say that.

          • The article sorta implies it:

            "By taking the [reverse-osmosis] process to a place in nature where that pressure naturally exists, we don't have to create an artificial pressure gauge on land, as we traditionally do in desalination."

            That's a quote from someone at OceanWell, but maybe it's out of context or something. I did make an attempt at figuring out where the energy savings was coming from, but couldn't find a real explanation anywhere.

        • Sounds more like another "unicorn" startup hoping to grab some VC attention to me. There's a lot of maybe and ought to going on.

        • You give too much credit to VCs, startup business reporters and the editors here.

      • TANSTAAFL is right. But if you fill a pipe with fresh water and sink one end of it to the ocean floor, there will be a pressure differential on the deep part of the pipe. Because the fresh water weighs less than saltwater. Hope that makes sense. It is very straightforward. There is no way it is wrong. Now put a membrane there. You have pressure across the membrane. Don't see how that could be wrong. Do you?

        • The static pressure differential across an osmotic membrane with fresh water on one side and sea water on the other is 600 psi.

          That is a height difference of about 1300 feet of water.

          If you put an osmotic membrane on an empty pipe and push it down into the ocean, no water will flow into it until you reach 1300 feet. As you push lower, the level of the freshwater will not rise above 1300 feet below sea level.

          If you want to move the freshwater to sea level, you need to pump it up 1300 feet. Or 1400 feet for a

          • Seawater head is 0.444 psi per foot of depth. Freshwater head is 0.432 psi per foot of depth. The deeper you place the membrane, the greater the pressure differential. If you could place the membrane at 50,000 feet of seawater, you would have 600 psi across it, even when the freshwater side is full of freshwater. Do you see it now? The difference in density between fresh and saltwater creates an exploitable pressure difference.

            Does this create a violation of thermodynamics? No. The universe is left in a

            • In theory, that would work.

              But nowhere is the ocean 50,000 feet deep, and that is not what Oceanwell is doing. At 1400 feet, the density difference will only give about a 3% saving.

              • Agree on both counts. Even the Mariana trench is not 50,000 feet deep. And 1400 feet is only 18 psi of assist. Hard to believe that is worth it.

            • It doesn't matter because as soon as any water flows across the membrane, the pressure differential is gone. Sure, the freshwater column in the pipe will naturally end up being marginally higher than sea level without any pumping, but then you have to remove that water to create a differential again.

              Just ignore the membrane for a minute, and consider a U pipe. If you very carefully fill one side with freshwater, and the other with saltwater, and they magically don't mix, then the freshwater side will be m

              • Well, it does matter. Imagine a U shaped pipe with a membrane at the bottom. The pressure across the membrane is exactly the pressure difference between the freshwater column and the saltwater column. The flow induced by that pressure drop across the membrane is unknown. But unlikely to be zero. Also, if you put a well pump down the tube into the freshwater side, you can maintain the pressure on that side at 1 atmosphere by pumping freshwater out. This saves energy compared to sealevel RO because you don't

    • I haven't done the calcs to determine whether 1400 ft of seawater is enough to power the membrane and the freshwater lift but it seems likely.

      Every 33 feet of seawater is one atmosphere of pressure. So 1400ft is 42.4242... atmosphere of pressure. This value is obviously correct on face value.

      • If you fill up a pipe with fresh water, close off one end, and sink the pipe down in deep in the seawater, the pressure on the outside of the pipe will be larger than the pressure inside the pipe because seawater produces around 0.444 psi of static pressure per foot of depth. Fresh water is about 0.432 psi per foot of depth. So there will be a pressure differential. This is basic physics. There is no nonsense here. You then put a desalination membrane at the bottom of the pipe. Now you have a desalination m
    • Sigh. It's not just the static pressure that you need to push salt out of the water, it's the pressure differential. So they'll have to have a pump that raises the water and the brine back to the surface, or (equivalently) creates more than 1400ft of water column pressure to "push" the brine out.

      Except that now this pump is at 1400ft down in the water. Good luck servicing it.

    • Re: (Score:2)

      by gweihir ( 88907 )

      The primary problem is "ocean floor". That makes everything massively more expensive and exceptionally hard to maintain and repair. Incidentally, you get nothing for free here. The requirement to lift completely eliminates any advantage the pressure down there may have energetically. You only get a pressure differential when you pump one side out. Seawater is only a small bit heavier than freshwater. Apparently these people do not understand basic Physics.

  • Makes sense for large quantity (Score:3)

    by penguinoid ( 724646 ) on Saturday September 23, 2023 @04:50PM (#63871915) Homepage Journal

    So they can save on energy by putting their pressure differential as decompressing the freshwater, rather than compressing the salt water. Same pressure differential over a smaller volume, and the brine's compression is free so they can use as much as they like.

    • Re: (Score:2)

      by gweihir ( 88907 )

      They lose all that again, because they need to pump the freshwater up over 400m. Incidentally, water has almost no compressibility.

  • Huh? (Score:3)

    by labnet ( 457441 ) on Saturday September 23, 2023 @05:12PM (#63871947)

    I don’t get it. Where does the differential pressure come from? Is it just the density difference between fresh and brine? Ie column of freshwater is more buoyant so if you have 1km tube of fresh water in the ocean, it naturally wants to rise, and if you suck in more fresh water at the 1km deep inlet, you have a kind of perpetual option machine?

    • The hose back to the surface is one option. I had an idea a long time ago for an "artesian desalination" system that would essentially be a long pipe with a membrane in the last few meters. Your pump energy just needs to overcome the membrane pressure drop less the pressure from the density difference between the salt and fresh water. This sounds vaguely similar.

    • Re: (Score:2)

      by jwhyche ( 6192 )

      Let me see if I can explain what is going on here. I might be wrong but I'm sure someone will correct me.

      When filtering salt out of ocean water most of the energy is used to force the water through the membranes. What they are doing is sinking pods with the membranes exposed to the ocean down to 1400 meters. All the pressure from the weight of the water will force the water through the membranes eliminating energy use for this. All you have to have is negative pressure of type on the other side of

      • What people are pointing out is that much of the gain you get (free pressurization of the saltwater side) is lost because you also need to pump the water up from 1400 feet. Since freshwater is lighter than saltwater, it could still be somewhat beneficial energetically to do it this way. Also you are only pumping the fresh water. There is no point or need to pump the brine anywhere. In fact, the brine is just what is left behind after freshwater traverses the membrane. I don't know. Maybe it works out to be

        • Why would anyone go down there? Build your equipment to be only slightly heavier than water and then bring it up to work on it.

          • Yeah. It might be possible to do it that way. Like a well on land. But it might need to be pretty robust with 1400 feet of pipe in the water column. If there is any current at all it will not stay vertical unless it is tethered to the bottom with a tight line (and a heavy weight). Still probably better than sending in divers.

    • Re: (Score:2)

      by gweihir ( 88907 )

      That is the "magic" used to separate the gullible from their money! It makes all these irrelevant problems disappear!

  • Okay I can kind of see it, the pure water is lighter so it wants to rise up, needs to be refilled and pulls water through the membrane ... yet it feels somehow wrong, a free lunch. Does that really work?

    • They will have to pump up the fresh water, but there is much less fresh water than salt water.

      Where a regular RO has to pressurize everything, this rig lets ocean do the work and you only have to pump out (depressurize) maybe 10% of the water, or what ever the fresh fraction is.

      So drop it in ocean like a big crab pot, pump out fresh water, then pull it up when the membranes foul which is always the problem with RO. As a bonus the waiter down there should be cleaner so the membranes should last longer.

      • Thanks, that makes more sense.

      • As a bonus the waiter down there should be cleaner ...

        Yes, but he'll be very grumpy from all the pressure he's under. :-)

      • Re: (Score:2)

        by gweihir ( 88907 )

        Hmm. You are on to something there. The conventional plant pumps in seawater and then pumps out brine and freshwater. This one just pumps out freshwater. Nope, still do not see it. They have to maintain these pods and that will likely eat more than all savings they could have. Oh, and there is another problem: The membranes used have a lifetime that strongly depends on the water being filtered. On land, you can filter, monitor, pre-condition, etc. Down at the ocean floor, the membrane just has to take it.

      • It doesnâ(TM)t matter how much fresh water there is in the differential, you still have to get it from 1400m or whatever it is down the ocean + the amount of energy necessary to create and maintain a pressure differential across the membrane for it to do work. Whether it works at 1400m or 5m doesnâ(TM)t matter, the communicating vessels work under the same principle. Just sticking an open ended pipe down the water doesnâ(TM)t make a fountain, which is what the claim here is.

        • Re: (Score:2)

          by ceoyoyo ( 59147 )

          Just sticking an open ended pipe down the water doesnâ(TM)t make a fountain, which is what the claim here is.

          It does when you hook up a pump powered by a wind turbine to it. That's the actual claim. Is all this perpetual motion / free energy nonsense the result of nobody bothering to read to the second paragraph?

          • But how is that using "40% less energy"? Are they only counting energy drawn from the grid? That seems disingenuous, but if so, why not use bigger turbines and claim it doesn't use any energy at all?

  • Sounds like a great idea, it really does. BUT, whenever a startup says something is 5 years away .. it usually means there's some fundamental flaws that they haven't figured out.

  • Sierra Club is a joke (Score:3, Informative)

    by MacMann ( 7518492 ) on Saturday September 23, 2023 @05:36PM (#63871965)

    In the fine article they got statements from the Sierra Club on what they thought. I can't take them seriously on global warming or environmental protection so long as they continue to opposed nuclear fission as an energy source. Just so I was getting the latest on their stance on nuclear power I double checked my memories on where they stand I visited their website, and I found out they opposed nuclear fusion for energy as well.

    Considering nuclear fusion is still theoretical at this point I find it odd they felt a need to comment at all, and odder still to be opposed to even investigating the options.

    California needs freshwater, and by having access to the sea makes desalination of water something to investigate. No matter which process they use to separate the salt from the water it will take energy. Nothing is as safe, abundant, or reliable as nuclear fission for producing energy. Any issues California may have with nuclear power are far easier to solve than getting "zero carbon" energy in the quantities needed from any other source. If earthquakes, tsunami, or storms off the sea are a concern for coastal nuclear power plants then put the power plant inland somewhere and run wires to the desalination plants.

    I saw an interesting interview with Neil deGrasse Tyson where he spells out quite clearly that the problem with freshwater is one of cost, and a large part of that cost is energy. Dr. Tyson also points out another big part of that cost is supply/demand dynamics. If the water supply issue gets bad enough then it becomes cheaper to put the energy into desalination than to ship freshwater in from other states. Where should California get this energy while protecting the environment and lowering CO2 emissions? The IPCC says we need energy from nuclear fission or we will fail to meet CO2 emission reduction goals. The Sierra Club is an unserious anti-scientific organization by continuing their policy of opposing nuclear power in any form.

    The Sierra Club opposes desalination because the brine it creates could harm marine life? What about the harms to human life if there's a shortage of water to drink? They are a joke, nobody should be listening to them until they start showing some basic understanding of science and concern for human life.

    • No matter which process they use to separate the salt from the water it will take energy. Nothing is as safe, abundant, or reliable as nuclear fission for producing energy.

      A nuke a day keeps Nestle at bay. Just setting off nukes underwater will produce all the vapor-distilled water you could possibly need. What could go wrong?

    • Decades ago I contacted the Sierra Club about a local deforestation issue and they had zero interest.

      I was upset because I believed what people claimed back then. Now it's just an obvious scam organization.

    • The IPCC says we need energy from nuclear fission or we will fail to meet CO2 emission reduction goals.

      We are already failing to meet CO2 emission reduction goals, because the anti-nuclear lobbies sponsored by the fossil fuels industry successfully sabotaged nuclear development in the western world.

      Fortunately, less and less countries listen to them, and are turning toward a mix of both nuclear and renewables. Unfortunately, humanity will have to suffer more consequences from climate change than what was truly necessary. Most of the deaths will be in poor countries, while rich countries will just;.. be sligh

    • Nobody can take your credentials as an environmentalist seriously if you oppose an environmental organization simply because they don't agree with nuclear. Most don't.

      • Re: (Score:2)

        by ghoul ( 157158 )
        Most Environmental Orgs are elitist scams meant to generate employment for otherwise unemployable rich kids.
        • I didn't say "orgs." I said environmentalists. Most environmentalists don't agree with nuclear, and most oil-scum love it. If you were a real environmentalist with an upward battle to convince others, you would understand the burden was on you, not try to sabotage everyone else. Fortunately you're not one, and no one could possibly believe you are.

      • Nobody can take your credentials as an environmentalist seriously if you oppose an environmental organization simply because they don't agree with nuclear. Most don't.

        The Intergovernmental Panel on Climate Change, or IPCC, has been writing reports for years showing that global targets on CO2 emissions reductions will not be met without greater utilization of nuclear fission as an energy source. There's other reports from a number of subject matter experts that agree. What credentials do the members of the Sierra Club have to claim that nuclear power should not be considered as a part of our future energy needs?

        Scientific studies tell us that if we don't increase our ut

        • The Intergovernmental Panel on Climate Change, or IPCC, has been writing reports for years showing that global targets on CO2 emissions reductions will not be met without greater utilization of nuclear fission

          Perhaps they did in the past -- I honestly don't know -- but they don't anymore (2022 summary) [www.ipcc.ch]. They mention nuclear as an option on pg 38, but it clearly has a lower cost/benefit than wind and solar.

          On page 67 of the technical summary [www.ipcc.ch], they write

          The political, economic, social, and technical feasibil

    • Re: (Score:2)

      by jezwel ( 2451108 )

      No matter which process they use to separate the salt from the water it will take energy. Nothing is as safe, abundant, or reliable as nuclear fission for producing energy.

      Penetration of rooftop solar PV is causing negative energy prices during the day in my state, and that's not counting storage backed commercial solar plants. Batteries aside, we need other energy sinks to use this excess energy. We're seeing hydrogen production as one, and now I'm wondering if desal could be another.

      • Penetration of rooftop solar PV is causing negative energy prices during the day in my state, and that's not counting storage backed commercial solar plants.

        Negative electricity prices through the day are not a good thing, that shows that the government is throwing so much money in subsidies that it is profitable to pay people to take electricity that they normally would not want. If I'm paid to burn electricity then I'd be tempted to open up my windows and crank up the air conditioner. You want me to believe such wasteful uses of electricity don't take place with negative electricity pricing?

        Batteries aside, we need other energy sinks to use this excess energy. We're seeing hydrogen production as one, and now I'm wondering if desal could be another.

        Once there is electricity storage on the grid then any power plant

  • are roughly one and the same.

    Whatever you save on not having to make high pressure on the surface you lose right back having to pump up your product from the ocean floor.

    Serving the RO membranes in those pods? Well, let's just pretend we won't need to do that, and by the time our investors realize they've sunk their money, we'll be living it up in a pineapple under the sea...

    • From what I'm seeing, instead of pumping up the freshwater, they're banking on the brine being more dense than the newly-processed freshwater, and having the freshwater naturally rise up because of that.

    • are roughly one and the same.

      Whatever you save on not having to make high pressure on the surface you lose right back having to pump up your product from the ocean floor.

      Serving the RO membranes in those pods? Well, let's just pretend we won't need to do that, and by the time our investors realize they've sunk their money, we'll be living it up in a pineapple under the sea...

      Very spot on. Which to me suggests that is we want to use "natural pressure" We would pump seawater into holding ponds at a higher altitude, then release them similarly to the way we use hydraulic storage for power generation.

      Pump the seawater, then release it. For those who are worried about solar after dark, you just pump it during the day. Don't even need the power grid. Then you release it as needed into nice osmotic desalinators. The pumps and desalinators are all on the surface, eliminating a maint

      • Re: (Score:2)

        by ghoul ( 157158 )
        You have 10 litres of Saltwater from which you get 1 liter of fresh water. These guys are proposing pumping up 1 liter of fresh water. You are proposing pumping up 10 liters of salt water. Does the reduced maintenance cost justify a 10 times more pumping cost? As a bonus no Sierra Club activists to come along and destroy your desalination equipment on the surface.

        • Considering I have to pump that 10 liters of seawater 10 meters up versus 300+ for that one liter of freshwater, I think the math speaks for itself.

          • Re: (Score:2)

            by ghoul ( 157158 )
            How would you get the same pressure from 10 meters that you got from 300+? In fact you would need to pump it much higher when pumping up as when pumping up you are only getting the air pressure and gravity whereas at the bottom of the sea you are getting water pressure and gravity and water pressure is much higher than air pressure for the same height difference.

            • Again, doesn't matter: even 1400 ft down, you have to purge the brine somehow. And if that somehow means pumping it out of your lower pressure pod into high-pressure ocean depths, you've got the exact same problem of moving the same flow at the same pressure that you would at the surface.

        • You have 10 litres of Saltwater from which you get 1 liter of fresh water. These guys are proposing pumping up 1 liter of fresh water. You are proposing pumping up 10 liters of salt water. Does the reduced maintenance cost justify a 10 times more pumping cost? As a bonus no Sierra Club activists to come along and destroy your desalination equipment on the surface.

          What do you think the pumping cost is? If you have a pump at all, it hardly costs anything more to pump those 10 litres of seawater than that 1 liter of pure desalinated water.

          And your Sierra Club fantasy is just that - weird. Even if your enemy was planning on destroying the pumped seawater they'd be quite able to destroy the pure fresh water as well.

          Looking forward to your cost analysis

          • Re: (Score:2)

            by ghoul ( 157158 )
            Pumping cost is proportional to volume. It costs more to pump more. Even a kindergardner knows that. Why are you on slashdot?

            • Pumping cost is proportional to volume. It costs more to pump more. Even a kindergardner knows that. Why are you on slashdot?

              To make fools of people like you, who can't even supply the facts to back up your specious claim.

              Yes, it will take a minuscule amount more electricity to run a pump longer. But you need to tell us exactly how that relates to the maintenance of Osmotic desalinators and pumps on the ocean floor. Meanwhile with a surface based system using hydraulic storage for pressure, the only thing in the saltwater environment is the piping, which now has no need to be at the bottom of the ocean.

              You made the claim ghou

    • There is some possibility of energy savings. Salt water static pressure is 0.444 psi per foot of depth. Freshwater is 0.432 psi per foot of depth. So 1500 feet gets you a pressure differential of 1500 x (0.444 - 0.432) = 18 psi. Not enough to drive a reverse osmosis membrane I wouldn't think. At 50,000 feet there would be 600 psi across a membrane between salt and fresh water columns. Enough to make fresh water. I'm sure you would still need a pump to overcome friction of water flowing in pipes. But your de
  • Two very helpful things are extraordinarily abundant on this planet: Sunlight and seawater. Fresh water, however generally abundant, is conditional and subject to scarcity problems. The math is unambiguous about how to deal with these three things.
  • Las Virgenes Municipal Water District serves Calabasas, California, a city of about 22,000 in the San Fernando Valley of Los Angeles County. While separated from the Pacific by about 10 hilly miles, building a pipeline to the Malibu coast seems not unreasonable..

  • Putting your desalination plan in the bottom of the ocean increases the pressure on both sides of the membrane. The only difference is that the pump at the bottom of the ocean costs a lot more and needs much longer cables.

    This is another pseudoscience investor scam.

    Besides everybody knows the only way to separate randomly moving particles with zero energy input is Maxwell's demon.

  • Where are they going to put the brine/excess salt? Back into the ocean? ... That would be a really bad idea. How about saving and preserving water first? ... Or are they going to store it on land, in huge piles of salt? Then what's going to happen with the next flood?

    I hope authorities tripple-check this project before they greenlight it.

  • No pics of any actual devices on OceanWell'l website ! Bunch of fancy graphics and blah blah... The pilot project, which will begin in Las Virgenes' reservoir near Westlake Village, hopes to establish the nation's first-ever "blue water farm." So have they never tested it yet ? Could not find any info on reservoir depth for them to test the pods placed at depths of about 1,400 feet which they said is needed to work.

  • Very clever. Tap the water district to send money down the drain.

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