16 ms·
Simple, solar-powered water desalination (2020)
- carl_dr 5y agoThis device "could" produce 1.5 gallons per day, per square metre of solar collecting area. The researchers estimate a system suitable for a family might be built for $100, so double or triple that after profits etc. I assume that the 1.5 gallons was the highest yield they would have had from a single day, had they had a 1 square metre solar panel, and the expected average yield would be less (accounting for cloud cover etc.) But even with reduced yield, for very small communities of a few dozen people, this definitely could work out.
- tromp 5y agoThe article says "per hour", not per day. Although that would seem able to support dozens of users rather than just 1.
- carl_dr 5y agoThanks for spotting that. I'm a little confused then, later in the article it says "The team estimates that a system with a roughly 1-square-meter solar collecting area could meet the daily drinking water needs of one person." So something doesn't add up. [Edit: the paper is available at https://pubs.rsc.org/en/content/articlehtml/2020/ee/c9ee04122b#imgfig3 https://pubs.rsc.org/en/content/articlehtml/2020/ee/c9ee0412.... It says, "To meet the average daily water intake for one adult (≈3.2 L),49 100 TMSS devices can be placed into a 10 × 10 array, filling an 1 m2 area, which would provide approximately 10–20 L of clean water every day depending on the weather condition." The lower bound of 10l is outdoor performance on a partly sunny day. So I think they are just being conservative by saying it would meet the requirements of one person - coastal areas are frequently cloudy, and in some locations, there might be little sun for extended periods of time.]
- londons_explore 5y ago'drinking water' often doesn't mean the water a human literally drinks, but all the clean water necessary for living everyday life (bathing, flushing toilets, washing dishes, cleaning clothes, cooking etc.).
- celticninja 5y agoI am pretty sure if you had to get your water from one of these devices you would not be using it to flush toilets or other non-essential use. And actually it does seem like 'drinking water' is actually drinking water and not for all those other uses you mentioned. As 3.7 litres is the amount required for a human male each day. https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/water/art-20044256 https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-h...
- lyschoening 5y agoFrom Wikipedia: > Drinking water, also known as potable water, is water that is safe to drink or use for food preparation. 40-50L per day would seem to about cover one person's essential uses of potable water.
- kingsuper20 5y ago>I am pretty sure if you had to get your water from one of these devices you would not be using it to flush toilets or other non-essential use. Are you suggesting that toilets, showers, washing machines use salt water?
- celticninja 5y agoIs there a problem with flushing a toilet with salt water?
- kingsuper20 5y agoOffhand I'd say that you are doubling the plumbing system plus you are using a much more corrosive fluid. It would be an interesting experiment, since toilets use a great deal of water. Take a beach town, build a separate pressure water and sewer system, see if it's worth it. It's certainly more complicated than a sailboat's set up.
- kingsuper20 5y agoThe average US citizen uses 82 gallons of potable water per day.
- finiteloops 5y agoSounded astonishingly high, but a quick search from a few sources (one cited [1]) checks out. Now to go down a rabbit hole of how this 82 gallons breaks down and what I can do to reduce my consumption... [1] https://www.usgs.gov/special-topic/water-science-school/science/water-qa-how-much-water-do-i-use-home-each-day?qt-science_center_objects=0#qt-science_center_objects https://www.usgs.gov/special-topic/water-science-school/scie...
- crackercrews 5y agoFor those curious what the 385% refers to > the team’s demonstration device can achieve an overall efficiency of 385 percent in converting the energy of sunlight into the energy of water evaporation. Honestly I still don't know what that means, or how efficiency can be over 100%.
- est 5y agoI guess water evaporates naturally, adding sunlight speed up the process.
- OJFord 5y agoAnd my perpetual motion machine uses naturally running hamsters.
- kbenson 5y agoI think maybe it means "3.85 times as efficient as sunlight in evaporative filtering" ?
- TheSmiddy 5y agoI think it means 3.85x more water is evaporated compared to just leaving the water outside in the sun.
- OJFord 5y agoI'm not even sure what 'the energy of water evaporation' means? Gravitational potential of the mass of water evaporated (and condensed at some height)?
- fuzzybear3965 5y agoI think they mean latent heat/enthalpy of evaporation.
- eigart 5y agoMy understanding: As the water condenses onto the next surface layer in the stack, the solar heat is recycled. This is because the transition from gas to liquid releases heat. Really clever stuff! Edit: mixed up evaporate/condense
- kzrdude 5y agoIs the water pumping also passive? I'm just assuming that you'll have salt water on a lower level, and you'll need to lift it up to this installation to process it.. with a pump.
- h0l0cube 5y agoThe article suggests it could float: > In a free-floating configuration, any salt that accumulates during the day would simply be carried back out at night through the wicking material and back into the seawater, according to the researchers.
- sonicggg 5y agoWhat's the point here? Is electricity even the bottleneck of water desalination? I thought the biggest issue with these plans is the brine. That is the major pollutant, and no amount of solar panels will solve that.
- hnhg 5y agoThe article directly addresses your point.
- Johnythree 5y agoIt doesn't. Any salt extraction creates brine which must be disposed of somehow.
- neilwilson 5y agoThe trick is to flow seawater past the still and take only, say, 1% of the water from each litre that flows past, which you can do with a still as opposed to a filter. It's a bit like slingshotting a space probe past venus. Technically to move Venus a bit closer to the sun, but not enough to make a difference.
- shoto_io 5y agoReading the article might help: > Unlike some desalination systems, there is no accumulation of salt or concentrated brines to be disposed of. In a free-floating configuration, any salt that accumulates during the day would simply be carried back out at night through the wicking material and back into the seawater, according to the researchers.
- andromeduck 5y agoIt makes no difference how concentrated the output brine is if it's the diluted to same concentration at the outlet and the same amount of fresh water is extracted.
- 5y ago
- eterevsky 5y ago> 1.5 gallons of fresh drinking water per hour for every square meter 7 litres per m^2 per hour.
- vagrantJin 5y agoThank you.
- im__so__meta 5y ago5.78 liters per square meter actually, per the article.
- sdoering 5y agoSo in ideal conditions one could expect to provide about 12 to 15 people with drinking water per square meter. For me this is an impressive number. If I calculate one unit with 300 dollars this would mean 5.5 cents per person per day for one year for fresh drinking water. And after that only a little bit for maintenance probably.
- _0ffh 5y agoHmmm, yes it is. It's nearly too impressive! From the article "The team estimates that a system with a roughly 1-square-meter solar collecting area could meet the daily drinking water needs of one person.", which sounds very different. On this Q&A page [1] Zhang is quoted "Our current strategy, for example, is to use an assembly of 100 of these devices to achieve an area of 1 m2, which will increase the total production by 100 times to create 10-20 liters of clean water per day." I don't want to sound too negative, but something doesn't add up here. Still, enough water for one person per square meter of desalination plant is an impressive result I think. The oceans are big. [1] https://www.techbriefs.com/component/content/article/tb/features/qa/36379 https://www.techbriefs.com/component/content/article/tb/feat...
- hexane360 5y ago96.3 um/s! That's enough to drain a 6 foot deep swimming pool in 5.27 hours.
- hinoki 5y agoIt sounds like they figured out how to make the distillation version of a compound steam engine [0]. Like others, I’m confused by the efficiency number. Are they producing 385% more water for the same energy compared to the best single state result? [0] https://en.m.wikipedia.org/wiki/Compound_steam_engine https://en.m.wikipedia.org/wiki/Compound_steam_engine
- andromeduck 5y agoThat's already a thing. https://en.wikipedia.org/wiki/Multi-stage_flash_distillation https://en.wikipedia.org/wiki/Multi-stage_flash_distillation
- stubish 5y agoI like the idea that brine is disposed over time at night, which will greatly reduce the disposal problems.
- lvs 5y agoDoes anyone actually believe a word of this?
- azinman2 5y agoYes. Why wouldn’t you?
- kumarvvr 5y agoThe 385% seems to refer to obtaining de salination in lesser solar collection area requirements.
- vr46 5y agoThis is the winning sentence for me: Unlike some desalination systems, there is no accumulation of salt or concentrated brines to be disposed of.
- creshal 5y agoOr is it? > In a free-floating configuration, any salt that accumulates during the day would simply be carried back out at night through the wicking material and back into the seawater, according to the researchers. This is fine for a small scale demonstration unit, but with bigger plants you will again run into the problem of over-salinating seawater, destroying the environment (and reducing your still's efficiency). So once you get past a certain scale, you'll again need to redirect the wick into some waste brine tank and figure out logistics for disposing it.
- hoseja 5y agoThat would have to be a very small sea indeed.
- creshal 5y agoI'll assume the device isn't using an infinitely long wick, so you face the same outflow problems as traditional plants: https://en.wikipedia.org/wiki/Desalination#Outflow https://en.wikipedia.org/wiki/Desalination#Outflow
- Chris2048 5y agoCan salt be compressed and then just buried?
- creshal 5y agoSure, it's just that in this regard it has no advantage over other desalination technologies. You always have to deal with the excess salt, MIT is dishonest in waving away these concerns.
- NiceWayToDoIT 5y agoHow much would it cost on industrial scale? (for irrigation system for farming purposes traditional/hydroponic/aquaponics (considering that aqua systems use 1/10th of the water of soil-based gardening) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4483736/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4483736/
- NiceWayToDoIT 5y agoThinking about California drought problem and what scale of investment would it be needed to fix it.
- owaisin 5y agoHow much cost?
- drawkbox 5y agoThis is essentially a solar still that uses the natural water cycle to produce fresh water. Learning about desalinization should be taught in all schools for more innovations in this area. It would be a cosmic joke to run out of water on a water planet, we'd look like universal dunces. USGS site has a great overview of desalinization that is a good place to start, you can even try your own solar still in your backyard. USGS Desalination site [1] Build your own backyard desalinization system (solar still) [2] > You can make your own personal desalination plant > Remember looking at the picture at the top of this page of a floating solar still [3]? The same process that drives that device can also be applied if you find yourself in the desert in need of a drink of water. > The low-tech approach to accomplish this is to construct a "solar still" which uses heat from the sun to run a distillation process to cause dew to form on something like plastic sheeting. The diagram to the right illustrates this. [2] Using seawater or plant material in the body of the distiller creates humid air, which, because of the enclosure created by the plastic sheet, is warmed by the sun. The humid air condenses water droplets on the underside of the plastic sheet, and because of surface tension, the water drops stick to the sheet and move downward into a trough, from which it can be consumed. > You can try this at home! [2] > - Dig a pit in the ground > - Place a bowl at the bottom of the pit that will be used to catch the condensed water > - Cover the pit loosley with a plastic sheet (you can use stones or other heavy objects to hold it in place over the pit > - Be sure that the lowest part of the plastic sheet hovers directly over the bowl > - Leave your water "trap" overnight and water can be collected from the bowl in the morning We need to put tons of money in desalinization. California is already a leader in that but we need more. Israel and Saudi Arabia are also pretty good at desalinization due to more dire water situations. Additionally we need geoengineering in terms of helping create moisture/rain in areas that feed the Colorado. The better bet is desalinization that uses the nature water cycle, it makes for cleaner water as well. Saudi Arabia is doing a solar dome to test this [4], we need more of this. [1] https://www.usgs.gov/special-topic/water-science-school/science/desalination?qt-science_center_objects=0#qt-science_center_objects https://www.usgs.gov/special-topic/water-science-school/scie... [2] https://www.usgs.gov/media/images/how-build-your-own-solar-still https://www.usgs.gov/media/images/how-build-your-own-solar-s... [3] https://www.usgs.gov/media/images/a-floating-solar-still-desalinate-seawater https://www.usgs.gov/media/images/a-floating-solar-still-des... [4] https://wired.me/science/environment/desalination-solar-dome-saudi-arabia-neom/ https://wired.me/science/environment/desalination-solar-dome...
- rorykoehler 5y agoWould it be possible to re-green deserts with this technology? Does anyone know of any studies on using this technology to combat climate change?
- underwater 5y agoYishan Wong, of Reddit CEO infamy, has been working on this for a few years: https://www.terraformation.com/ https://www.terraformation.com/
- kevmo 5y agoI seriously considered taking a job there (I did not for personal reasons, namely not wanting to move) and would recommend looking at them to others. I think they are poised to be a key player in the forestry and reforestation space in the next 2 decades.
- justshowpost 5y agoBut... the reforestation occurs naturally for last 2 decades (at least, more like for 3 or even 4)
- jarenmf 5y agoGreening deserts is not a good solution for climate change. In fact it might worsen climate change due to albedo changes. A nice video about this: https://www.youtube.com/watch?v=lfo8XHGFAIQ https://www.youtube.com/watch?v=lfo8XHGFAIQ
- youngtaff 5y agoChallenge with that video is it takes a very industrial approach to green deserts - mono cultures for trees, massive desalination plants to provide water etc Some of the original ideas for greening deserts are permaculture based (https://www.youtube.com/watch?v=sohI6vnWZmk https://www.youtube.com/watch?v=sohI6vnWZmk) which are a way more sustainable approach but won't bring around carbon reduction fast enough.
- timonoko 5y agoYou need exactly 3 litres per day. Or rather: I do and I did it for several years. This would mean tiny portable and durable device and it would make many places totally habitable. Not just Baja California.
- bigbizisverywyz 5y ago"Tests on an MIT building rooftop showed that a simple proof-of-concept desalination device could produce..." So doesn't look like they've even hooked it up to the sea yet, so still a bit to go for a real implementation, but still sounds interesting. I harbour a small dream that I could buy some seaside land someday on a Greek island and hook one of these desalination devices up to the sea and build myself a small oasis.
- gregoriol 5y agoThe device itself would not be "on" the sea, it would just get water from it with a pipe/pump. I don't really see any reason it wouldn't work the same way by the sea: the main problem seems to be how to remove the salt, efficiently, not how to get water into the device, which is easier. Getting enough sun might even be harder than getting sea water.
- bigbizisverywyz 5y agoYep, and that's what I basically meant by 'hooking it up'. I guess you would need a pump to bring the seawater to the device, something to pump it elsewhere (for storage, or irrigation), and also some mechanism to dump the brine back in the sea when you're no longer desalinating. And for maximum ecological efficiency that could be powered by solar panels. I wonder how maintenance free you could build such a device, and just leave it to work away by itself for months on end.
- bjackman 5y agoDoes anyone know of any designs for DIY passive desalinators? My mum has a house on an island that doesn't have a natural source of fresh water (except rain of course), and it just occurred to me that a desalinator would be a fun thing to build there. Normally if there's a long drought she would have to have drinking water delivered by sea.
- ratsforhorses 5y agoI'm sure you'll get better answers but I really liked the idea of ventilating greenhouses with salt water.... could be a good way to get the extra liquid needs..a quick google found me this https://www.sciencedirect.com/science/article/pii/S0011916417302400 https://www.sciencedirect.com/science/article/pii/S001191641...
- Cthulhu_ 5y agoThe most simple ones ("survival" type, but it won't produce enough water unless you scale up) is spanning clear plastic over a pool of (shallow) salt water, weigh it down with a rock in the middle, and put a collector in the center underneath so the evaporated water runs down it. But I'm sure there's commercial solutions out there.
- Ice_cream_suit 5y ago" Using a low-cost and free-of-salt accumulation TMSS architecture, we experimentally demonstrated a record-high solar-to-vapor conversion efficiency of 385% with a production rate of 5.78 L m−2 h−1 under one-sun illumination, where more than 75% of the total production was collected through condensation. " Abstract is available here: https://pubs.rsc.org/en/content/articlelanding/2020/ee/c9ee04122b#!divAbstract https://pubs.rsc.org/en/content/articlelanding/2020/ee/c9ee0... The original journal article is available here as a pdf: https://pubs.rsc.org/en/content/articlepdf/2020/ee/c9ee04122b https://pubs.rsc.org/en/content/articlepdf/2020/ee/c9ee04122...
- reizorc 5y agoThere's still the issue of what you do with all that salt
- konschubert 5y agoput it back into the ocean where it came from?
- Johnythree 5y agoBrine is toxic unless it can be diluted. Which ends up being a huge problem in large plants.
- deleted 5y ago[deleted]
- dsign 5y agoThis reminds me of how many places we have on the planet which are beautiful but inhospitable. Fixing the inhospitable part will come its own environmental impact, and the places will end up being less "beautiful". I vote we go to live elsewhere and leave the planet as a giant touristic resort :) .
- ppf 5y agoIt's incredibly disappointing to see MIT put its name to some apparently PhD-level research that claims over-unity efficiency, and apparently (according to the picture) using a few baking trays and tinfoil. It also does not explain how to deal with the increased salination of the water source, nor how water can continue to condense on the successive layers of the device as they are heated due to that condensation.
- linschn 5y agoThis is for small scale, family-sized units, where power and cost are the limiting factor, so brine will not be an issue at this scale. As for condensation, the plate is hot, but colder that the vapor, and heated by the vapor only, so when it is too hot, condensation stops, the temperature drops quickly due to evaporation on the other side, and condensation can continue. At equilibrium, each successive plate is colder than the next, the last one using the sea water as a heat sink. This is actually innovative and the optimization of the design parameters (e.g. The distance between the plates) is not trivial. I think you are overly dismissive of this solid piece of engineering.
- einpoklum 5y ago> The system delivered pure water That's toxic! We can't drink pure water. You have to maintain _some_ of the minerals in there, you just want to take most of the NaCL out. Does the system avoid this over-distillation? i.e. is the water properly potable, or is it just not-salty?
- c618b9b695c4 5y agoIt is my understanding that it is incredibly difficult to keep water pure. Transporting it any amount of distance from the source is likely to leech quite a few minerals from the available pipes.
- jokoon 5y agoJust add some artificial minerals, it can come in some powder form I guess.
- regularfry 5y agoA few years back Coca-Cola got in trouble by doing exactly this. What they were doing was taking tap-water, and purifying it so they could sell it as "Dasani" - not a mineral water product, exactly, but a "lifestyle drink" they called it. The thing about water when it's pure enough is that it's remarkably odd. It's unpleasant stuff: it'll weaken concrete if it leaks onto it, apparently it'll damage brass and steel, and it'll leach the minerals out of your teeth, but only until the water is no longer pure enough to do so. So what people do is, as you say, add buffer minerals back into the purified water to take the edge off. What Coca-Cola got wrong was the dosing: they put ten times the amount of buffer minerals into the water as they should have, and made it toxic. So they'd taken a perfectly safe tap-water supply and ruined it.
- 6nf 5y agoI drink distilled water all the time, it's not toxic in normal quantities.
- einpoklum 5y ago
- jokoon 5y agoWhat is this aerogel thing, and this "capillary wick"? Not bad for $100, but I'm more interested in durability, if parts needs to be replaced and maintained, and if yes what is required to make those parts.
- MauranKilom 5y agoThe capillary wick is literally a paper towel.
- inglor_cz 5y agoThis article is 17 months old. Has anything happened in the meantime? (Aside from Covid, of course.)
- baybal2 5y agoThe article in question: https://pubs.rsc.org/en/content/articlepdf/2020/ee/c9ee04122b https://pubs.rsc.org/en/content/articlepdf/2020/ee/c9ee04122...
- squarefoot 5y agoFTA: "Unlike some desalination systems, there is no accumulation of salt or concentrated brines to be disposed of. In a free-floating configuration, any salt that accumulates during the day would simply be carried back out at night through the wicking material and back into the seawater, according to the researchers." The capabilities are freaking interesting, but let's say someone builds a big enough settlement on a coastline or island in which every building has one or more of these devices on its rooftop. Would this release back enough salt so that the surrounding seawater becomes hostile to its previous lifeforms? Also, since then the water used in the process would contain more salt, how much would that render the device less efficient?
- dystroy 5y agoSalt release is already a huge environmental concern with exiting desalinization systems. Energy consumption and installation costs aren't the sole (and probably not the main) problems. Desalinization is inherently a pollution.
- Someone 5y agoA small part of it can be avoided by combining this with a salt evaporation pond (https://en.wikipedia.org/wiki/Salt_evaporation_pond https://en.wikipedia.org/wiki/Salt_evaporation_pond) Problem will be that we’ll get way too much salt (a few grams of salt per liter of water), so it won’t help much.
- throwaway894345 5y agoWhy not release the salt back to the sea? Presumably it would not increase the salt content of the ocean very much considering the vastness of the ocean and the sheer quantity of fresh water that is being added to it by melting glaciers, etc? What am I missing?
- dystroy 5y agoThe salt you release isn't instantly diluted in the whole ocean and we're speaking, for a plant, of millions cubic meters of salt enriched water per day. The release area is just dying.
- neilwilson 5y agoPresumably you could use the same technology on liquid effluent to create a 'toilet to tap' cycle
- fabbari 5y agoI had the "stupid moment" of the day. The thermal effects of evaporation on a surface is that the surface actually cools down -- so I could not get the "it produces heat" part. After drinking my morning coffee I realized that the heat transfer is from the surface to the water droplets/vapors that then carry it to the next layer of this still. Ergo: coffee makes you smarter and I shouldn't be on HN so early in the morning.
- raarts 5y ago[Feb 2020]
- pfdietz 5y agoAn issue with desalination systems of this type (that have water vapor in a carrier gas, so called HDH or Humidification-Dehumidification desalination systems) is the retardation of mass transfer to the cold surface by the carrier gas. Multieffect distillation (MED) systems usually operate without a carrier gas for this reason, but this means they operate below atmospheric pressure, so they have to be sturdy to resist pressure loads. A few years ago, some people at MIT solved this problem with a bubble heat exchanger: the humidified carrier gas is bubbled up through trays of water (at progressively lower temperatures). The surfaces of the bubbles provide a very large surface area for heat/mass transfer. https://news.mit.edu/2013/produced-water-cleanup-0205 https://news.mit.edu/2013/produced-water-cleanup-0205 https://dspace.mit.edu/handle/1721.1/86334 https://dspace.mit.edu/handle/1721.1/86334 http://web.mit.edu/lienhard/www/papers/reviews/HDH-Desalination-chapter-2014.pdf http://web.mit.edu/lienhard/www/papers/reviews/HDH-Desalinat... Some of those involved went on to form a company to commercialize the technology, which has been used to recycle/purify brine from natural gas wells and other industrial tasks. I think they ended up being bought out after several years.
- Gravityloss 5y agoThe opposite of bubbles, mist, might also work. Extremely high surface area.
- deleted 5y ago[deleted]
- throwaway894345 5y agoThe comments here are all upset about the efficiency number presented in the article, but I was hoping for more commentary on the 1.5 gallons per square meter thing with respect to improving lives in the developing world.
- hiroshirama 5y agoWe can now have enough salt to last forever!
- deleted 5y ago[deleted]
- The_rationalist 5y agoNuclear desalination is more efficient though https://www.forbes.com/sites/jamesconca/2019/07/14/megadroughts-and-desalination-another-pressing-need-for-nuclear-power/ https://www.forbes.com/sites/jamesconca/2019/07/14/megadroug...
- bondolo 5y agoWhen the $100 system can run for 5 years of continuous production get back to me. I would be surprised if the system, as described, would work beyond a couple of days. Other than for emergency situations this isn't useful.
- tsjq 5y agoCalifornia is building the largest desalination plant in the US.(2015) Is this ready yet ?? https://news.ycombinator.com/item?id=10343296 https://news.ycombinator.com/item?id=10343296
- midnightclubbed 5y agoLargest SOLAR desalination plant in the US. The article doesn't seem to list the numbers but this article https://www.businessinsider.com/california-waterfx-solar-desalination-technology-aaron-mandell-2014-3 https://www.businessinsider.com/california-waterfx-solar-des... seems to indicate the next step up from their demo plant was a plant capable of 2M gal/day. Hopefully they are still developing the technology, it seems like it could be a life-changer for small farming communities around the world. By contrast the biggest 'traditional' desalination plant in the US makes 50M gal/day and the biggest plant in the world makes around 260M gal/day (US gallons).
- gumby 5y agoOver a decade ago I saw simple solar stills installed in India with the cascades built of concrete and a glass panel. This was at Maharana Prtap university in Udaipur. So “proud” of my Alma mater university for developing an exotic technology that uses aerogels and such ... sure, it’s more efficient, but those folks In Udaipur, without a big PR office like MIT’s, built something that could be built by anyone using everyday material.
- walrus01 5y ago> which was tested on an MIT building rooftop. The system delivered pure water that exceeded city drinking water standards, at a rate of 5.78 liters per square meter I would be very interested to see data on this vs. sunlight and climate conditions, in what weeks/month of the year they tested it. I think its effectiveness would be highest at MIT's location from late April to end of September and considerably less in colder/overcast/less sunny weather and winter.
- tenfourwookie 5y agoI imagine a trillion of these floating along the coast of the western United States, little landing pads (and solar powered charging stations) for a trillion drones that can move the freshly desalinated water from the ocean to the nearest forest fire. You need a drone cloud 500 million strong to deliver 100 million gallons of fresh water to X location immediately? No problem. Need a drone cloud to water your 20,000 acre vineyard? Coming right up. Who needs clouds?
- snek_case 5y agoWater is very heavy though. For watering crops I think you would do better in terms of energy efficiency with land-based infrastructure. At the very least, if you're going with drones, you ideally want something more energy-efficient than quadcopters.
- afterburner 5y agoA trillion? Well I guess efficiency doesn't concern you...
- tenfourwookie 5y agoIt's wild ass guess, but imagine a drone fleet capable of delivering that quantity of water on demand. We will see this in our lifetimes. Rain on demand.
- jvanderbot 5y agoI don't think we will. Except in the case of fighting fires in remote areas, if you want water in some area, you use pipes. For fighting remote fires, we already have piloted vehicles and in some cases uncrewed vehicles delivering water in bursts ... so perhaps.
- pomian 5y agoAnother interesting use for this system, and I didn't see it mentioned, is for water purification. That may be even more useful across the world especially in remote regions.
- Covzire 5y agoAs I understand desalination, a huge bottleneck besides cost is what to do with the brine. Why can't they build a gigantic pool/lake out in the desert and pump the brine there and let it dry into salt and other minerals. A 10 square mile pit/pool with a clay or other barrier to prevent it from sinking into the aquifers would allow for a massive amount of brine to be safely contained in one place wouldn't it?
- okareaman 5y agobrine disposable seems like a made up problem to me. We're not going to raise the salt content of the world's oceans by pumping the salt back from whence it came. I understand we don't want to put the high salt discharge near sea life, but that is not a hard problem.
- travisporter 5y ago> We're not going to raise the salt content of the world's oceans by pumping the salt back from whence it came. Sorry, maybe dumb question but why not? We're taking out water and leaving behind salt
- okareaman 5y agoI meant the salinity content per liter of the world's oceans would rise an insignificant amount, especially since fresh water flows back to the sea for the most part. If someone can tell me otherwise, I'm ready to be educated.
- mixmastamyk 5y agoIt takes a while to disperse. Meanwhile salinity in the region has gone up, say 2%. Apparently sea life is very sensitive to it. I agree there are a number of solutions though. Adding to treated sewage is a good one.
- okareaman 5y ago
- dang 5y agoDiscussed at the time: Simple, solar-powered water desalination - https://news.ycombinator.com/item?id=22269115 https://news.ycombinator.com/item?id=22269115 - Feb 2020 (192 comments)
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- specialist 5y agoHow can we couple this with carbon sequestration? Use byproducts (sodium, chloride, calcium, etc) as feed stock for useful compounds. eg Phosgene COCl2 is a valuable industrial product. Create artificial salt water marshes, which are pretty good at carbon capture. Everyone's trash is someone else's gold. People are clever. They can find good use for the salt.
- ohgreatwtf 5y agoThese are all extremely cool approaches to the problem but unfortunately they are all high tech and most require a substantial amount of complex component fabrication to work. I have been thinking about a passive, low cost system. It would use series of rows of shell-like structures with fresnel attributes and coatings that simultaneously cause water to condense on heated surfaces and then drain into subsequent rows of shells, a process that passively cycles with the heat of the sun. A large fraction of each row's output collects in a tank that is periodically raised to backflush the row and reduce the saline buildup.
- marco_craveiro 5y agoAmazing. I wonder if there has been an update since 2020, in particular with regards to mass-production...