Follow Slashdot stories on Twitter

 



Forgot your password?
typodupeerror
Earth Technology News Science

MIT Unveils Portable, Solar-Powered Water Desalination System 117

Posted by Soulskill
from the water-the-chances dept.
An anonymous reader writes "A team from the Massachusetts Institute of Technology's Field and Space Robotic Laboratory has designed a new solar-powered water desalination system to provide drinking water to disaster zones and disadvantaged parts of the planet. Desalination systems often require a lot of energy and a large infrastructure to support them, but MIT's compact system is able to cope due to its ingenious design. The system's photovoltaic panel is able to generate power for the pump, which in turn pushes undrinkable seawater through a permeable membrane. MIT's prototype can reportedly produce 80 gallons of drinking water per day, depending on weather conditions."
This discussion has been archived. No new comments can be posted.

MIT Unveils Portable, Solar-Powered Water Desalination System

Comments Filter:
  • 80 US gallons (Score:5, Interesting)

    by MichaelSmith (789609) on Tuesday October 19, 2010 @12:11AM (#33942870) Homepage Journal

    Thats 300 liters. Maybe enough for ten people if you are careful. Or a hundred people if you only need drinking water to keep them alive.

    • by T Murphy (1054674)
      FTA:

      the group built a small prototype [...] the prototype is capable of producing 80 gallons of water a day [...] They estimate that a larger version of the unit, which would cost about $8,000 to construct, could provide about 1,000 gallons of water per day.

      So based on your metric this supplies drinking water for over 1000 people. Still need a lot of these for bigger disasters, but $8/person isn't too bad.

      • by timeOday (582209)
        Continuing to quote the article: "...The design team also claim that two dozen desalination units could be transported in a single C-130 cargo airplane, providing water for more than 10,000 people."

        Think about Haiti in the days after the disaster when clean water was unavailable, the airport was partially inoperable and hopelessly overwhelmed, when airlifting hundreds of thousands of gallons of water (or diesel) was infeasible.

        • "...providing water for more than 100,000 people..." Wow, that's promising.
      • Re:80 US gallons (Score:5, Interesting)

        by afidel (530433) on Tuesday October 19, 2010 @12:34AM (#33942966)
        FTFA 24 of them will fit on a C130 and provide water for "more than 10,000 people", so I'm thinking more like 500 people per large unit and that's under ideal conditions. That's as opposed to a more traditional [usbr.gov] unit about the size of a cargo container that can do 200k gallons a day or enough for 40-50k people. Personally I think for large scale disasters it makes a LOT more sense to drop 2 of those and two fuel/generator sets and supply 10x more people with fresh water since every cargo flight counts.
        • but then the university students would have nothing to make them feel accomplished...

          the second i read "permeable membrane" i saw this as throw-away tech.

          • by kg8484 (1755554)
            Reverse osmosis works using permeable membranes - that isn't really the limiting factor since huge reverse osmosis plants exist in a number of places. The issue is that it takes a lot of energy to push water through one of these membranes, and solar probably isn't cutting it.
        • by kg8484 (1755554)
          The system you linked certainly does look impressive. However, it is billed as a water purification rather than a desalination system. Later in the page, it does say that it can handle saline water. Does that mean it can handle seawater, like a reverse osmosis system, or is it designed to work from a river and so its limit is brackish water?
        • Personally I think for large scale disasters it makes a LOT more sense to drop 2 of those and two fuel/generator sets and supply 10x more people with fresh water since every cargo flight counts.

          then you just have to keep air dropping or trucking in diesel every couple days as well. I think the point of it being solar is that it doesn't use up fuel resources which will likely also be quite scarce in a situation like this.

          • by afidel (530433)
            Say the initial tank is good for 2 days, with the initial drop you've provided the equivalent of 20 days with the solar load. If you can't get another fuel drop in in less than 20 days the place is absolutely screwed anyways.
        • Re: (Score:3, Insightful)

          by LongearedBat (1665481)

          for large scale disasters it makes a LOT more sense to drop 2 of those and two fuel/generator sets and supply 10x more people with fresh water since every cargo flight counts.

          That may depend on how close together those people are.
          If people are spread across a large area in many small villages, then perhaps many small setups is a more suitable option.

          • by afidel (530433)
            Yeah, after I posted I thought about that. Perhaps having both options available is a good thing =)
        • by Firethorn (177587)

          24 units at 1k gallons each = 24k gallons, for 10k people that's 2 gallons per person, per day.

          For yours it's 200k gallons for 50k people, which is 4 gallons per person, per day, or double the water ration.

          Going by the same standard you'd be supplying 100k people on the standard system using the MIT kid's standard.

          As for 'saline water', if it's like the systems I'm used it, it'll handle salt water and even sewage and spit out safe water, if nasty tasting.

    • Re: (Score:3, Informative)

      by kurokame (1764228)
      Longer, if they don't like their kids much.
    • I think your math is wrong - you're saying that people drink 8 gallons of water a day? The figure that always gets thrown around is "drink 8 8oz glasses of water a day", which is 64oz, or half a gallon.

      At half a gallon of water per day (which, still, is more than most people drink), that would be 160 people every day getting their recommended amount of water.

      • I am also thinking about cleaning clothing and cooking equipment, medical needs, hydration in hot climates. Supporting rescue workers doing hard physical work. That sort of stuff.

      • by Rogerborg (306625)
        If you're trying to perpetuate the stereotype that nerds don't wash, then congratulations, you win an internets.
      • The figure that always gets thrown around is "drink 8 8oz glasses of water a day", which is 64oz, or half a gallon.

        That's in addition to all the beer, not instead of it, right?

    • My god man, your bladder must be made of steel.

      Or are you that alienated from the real world that you think people in disasters zones first priority is a daily long hot shower and flushing toilets?

      Yes, we use a LOT of water in the west because... well because we can. When the shit hits the fan, 3-5 liters a day can and must be enough. And that is actually a rather liberal amount. Enough to drink, do some cleaning and cook. No it won't give you a life of comfort but guess what, it isn't. It is disaster rel

    • by VShael (62735)

      Thats 300 liters. Maybe enough for ten people if you are careful.

      You think a person needs to use 30 litres of water per day?

      Holy shit. We could solve our water problems by teaching people like you.

    • Better then none, and that is also by machine, put 10 machines side by side on the ocean floor all lined up with the same tubing, you can fill those tubes up enough that it spills into a container and keeps the water there for the people, sort of like a water tower....

    • That is rather good. As this doesn't seem that much bigger then a pool pump.

      You can truck it in. and hook it up and you have water for a family or too. The big ones that do a lot more needs a full infrastructure which is hard to deploy.

      It is like City Water vs Well water. You have the big plants to give water to a City you have this for water for the individual home, out side the infrastructure.

    • by bl8n8r (649187)

      > maybe enough for ten people if you are careful.

      Or enough for 100 people who wouldn't otherwise have .8 gals of water a day to drink.

    • I think they could make these cheaper.

      http://www.thefarm.org/charities/i4at/surv/sstill.htm [thefarm.org]

      They have no moving parts to break, require no electric.

      Add a few reflectors such as aluminum foil and increase
      your evaporation rate quite a bit.

  • by kurokame (1764228) on Tuesday October 19, 2010 @12:18AM (#33942902)

    Pump-fed nanofilters are sort of an old idea at this point. The summary leaves off some critical points like how much it costs and how long the filter lasts.

    According to the article, it costs $8000, which is a lot for some things but probably accessible for others. Let's just say it's not going to solve the world's water problem overnight, but it might be handy for relief efforts.

    Surfing through to the parent MITnews article [mit.edu], we get a bit more information, but it's still lacking anything about how long the system can operate or what its maintenance costs and requirements are. Does it last a week then you're out most of another $8000? Does it require a lot of technical expertise to maintain? It doesn't say...

    • Re: (Score:3, Informative)

      by wagnerrp (1305589)

      Pump-fed nanofilters are sort of an old idea at this point. The summary leaves off some critical points like how much it costs and how long the filter lasts.

      Exactly. The panels and pump are probably going to last several years without significant maintenance, but they will need a steady supply of filters to keep the thing going. They could extend the lifetime of them by running them in reverse for some amount of time to clean them out, but you can't do that indefinitely, and the system isn't usable while being back-flushed.

    • I don't mean to troll here, but has anyone else noticed that MIT has been producing a lot of things that seem mostly not very interesting? I had a similar thoughts as you, that it's hard to see what is particularly innovative about this. Did they really just fit some solar panels on a standard water filter? Kind of cool, but is it really better than things you'll see in Make?
      • by kurokame (1764228)

        MIT is a big school. You get all sorts of projects, really. You also get the usual fluff coverage in the media which tells you next to nothing about the actual project.

        MAKE also has coverage ranging from some pretty serious projects to "The Most Useless Machine" and "PLCs: What the heck are they" so it might not be a great comparison against all research churned out by a major academic institution. It has great stuff and it usually does a good job of catering to its audience, but at the end of the day it's

      • Simple is good. Its easy to maintain and easy to teach local people to take over maintenance.

      • Re: (Score:3, Interesting)

        by drinkypoo (153816)

        This is precisely what I was thinking. The water filter is neat but it is NOT solar-powered. It is electrically powered, and it is in this case coupled with a solar system which provides the power to operate it. I was excited because I would like a better, cheaper solar-powered desalinator.

    • According to the article, it costs $8000, which is a lot for some things but probably accessible for others. Let's just say it's not going to solve the world's water problem overnight, but it might be handy for relief efforts.

      Actually, the 8000$ was the expected cost of a larger 1000 gallon version.

      A larger version is also being designed, which will cost $8,000 and will be able to provide 1,000 gallons of water daily.

      1000 gallons a day is already a pretty nice amount, but as you said, the maintenance work and costs are unknown.

  • Not revolutionary (Score:2, Insightful)

    by Anonymous Coward

    While this design is a step up, and it certainly must have been a great engineering challenge to build and integrate, there is no groundbreaking technology that goes into this. It's a simple reverse osmosis plant, based on technology that's already being used at commercial scale. The summary is also misleading - this system also requires a lot of energy, it just has a power source with it. In fact, it's almost certainly less efficient than a conventional RO system, both in terms of energy used and embedded

    • by grantek (979387)

      That's what I was thinking - surely a hand pump would be much more useful most of the time? The solar panel would be good for keeping the unit busy when no one's around, but for a portable emergency supply you'd get more useful energy from people winding up a spring using a handle.

      • by delinear (991444)
        It probably depends where, when and how you deploy it - in the immediate vicinity of a disaster, where all hands are already employed with the more immediate task of rescuing trapped/injured people, then having a unit you can stick in the sun and come back to fresh water is probably not a bad thing. Once the immediate danger has passed, it might be more practical to use people power, or to ship in some generators and fuel as an interim solution.
  • by canatech (982314) on Tuesday October 19, 2010 @12:25AM (#33942932)

    And for about 8 more dollars, they could attach a big funnel and bucket for those days when it rains and the solar part doesn't work so well.

  • The obvious issue here is cost. But if they can get it low enough, they could sell this virtually anywhere to private residents, and I don't mean just 3rd world countries. Think about places like Australia where they frequently don't have enough water.
    • We have plenty of water in most places in Australia, however we've just recently started to realise that maybe we shouldn't be wasting so much on things like keeping cars clean and maintaining gardens that are reminiscent of England.
      • Re: (Score:3, Insightful)

        by sempir (1916194)
        Yup...that car and garden water could be better put to use in ..MAKING BEER!
    • Desalination plants are being installed in several parts of Australia including a controversial one in Victoria. The funny bit is that our drought broke just as construction got under way.

    • by tehcyder (746570)

      Think about places like Australia where they frequently don't have enough water.

      If you're in the middle of a drought, having a desalination plant is only useful if you're on the coast, the dry bits in the middle of Australia are quite a way from the sea.

  • Boats (Score:5, Insightful)

    by WindBourne (631190) on Tuesday October 19, 2010 @12:39AM (#33942994) Journal
    To get the price down, they need production of this. One simple way to do that, is to adopt it to boats in the western world. By doing this, the boats will be able to have clean water on-board available from offshore. Then as production increases, the costs go down. Then it allows these units to be produced CHEAPLY.
    • Re: (Score:3, Interesting)

      by TooMuchToDo (882796)

      Most commercial vessels (cruise ships, cargo/oil tankers, etc) already use evaporative systems (waste heat from engines/generators is used to flash heat water to steam, which is than condensed back into clean drinking water). A possible market would be smaller yachts and sail boats that sail around the Caribbean.

      • Re: (Score:2, Informative)

        by rmccoy (318169)

        Small reverse osmosis systems have been available for personal cruising boats for years. From units powered from the 12 volt battery system down to hand-pumped emergency units.

      • Note the word boat in mine and ship in yours.
        For example a 45' viking that is running out of Jupiter is ideal of this. The one advantage of a solar cell approach is that if a boat has an outage (diesel goes out), then you still have water.
  • Try it (Score:1, Interesting)

    by Anonymous Coward

    See how long those panels remain attached once the "disadvantaged" figure out what they are worth.

    • Probably not long.

      But, let's see how long the limbs of the thief remain attached to his body once his disadvantaged neighbors find out that they are about to die because of dehydration.

  • Question (Score:5, Insightful)

    by Prune (557140) on Tuesday October 19, 2010 @12:54AM (#33943082)
    Can someone comment on the comparative efficiencies of photovoltaic and solar thermal sources of energy? How much better is this really than using thermal-driven evaporative desalination? I mean, other than lacking in the "new and cool" factor
    • by Prune (557140)
      For example, vs approaches such as http://en.wikipedia.org/wiki/Solar_humidification [wikipedia.org]
    • Re:Question (Score:4, Interesting)

      by L4t3r4lu5 (1216702) on Tuesday October 19, 2010 @03:44AM (#33943772)
      More's the point, why the hell isn't their a manual pump? You don't need sunlight to hand-crank a piston. Some form of centrifugal brake* will prevent exceeding the maximum pressure of the filter, and it can run indoors with a hose out to the salt water.

      * - I don't know if this is the correct term. The faster you turn the crank, a set of weighted brake shoes (or similar) move out towards a high friction surface. The faster you spin, the harder it becomes to continue. Or some such.
    • Re:Question (Score:4, Interesting)

      by Biogenesis (670772) <overclocker...br ... shome...com...au> on Tuesday October 19, 2010 @03:58AM (#33943826) Homepage
      Here's a quick and dirty stab at some calculations:

      Wikipedia claims that reverse osmosis requires 6kWh to produce 1000L of water, or 21.6 kJ/L.

      To evaporate water already at 100C requires ~41kJ/mol, or 2.3kJ/L. To heat 1L of water from 20C to 100C requires 33.6kJ. So, by this very simplistic model it would require ~34kJ/L to desalinate water by boiling.

      Now the efficiency of PV vs thermal in a solar powered system depends on the efficiencies of the collectors. PV is ~25%, at best, solar insolation -> electricity. Heating water to evaporate it is a much more difficult calculation. Basically water doesn't have to be at 100C to evaporate and the losses in a thermal system would increase as the temperature differential (system->ambient) increased but in the end I'm not really educated enough to comment accurately. Hopefully the numbers above will give you some feel for the problem though.
      • by dj245 (732906)
        As another poster said, the heat is recovered using heat exchangers. You cool down the desalinated water and brine and heat up the incoming water. But wait, there's more- every system likes this runs in a vacuum. Water boils at a much lower temperature in a vacuum. Maybe the system runs at 60C instead of 100C.

        The problem is that this temperature is too low to kill bacteria and other nasty stuff in the water. So you need to treat with UV and chemicals. This increases complexity of the system slightly
  • arched over it and you get purified, distilled H2O dripping own the clear plastic dome.

    You don't need to hail this as revolutionary.

    You can apply the principle to a pool, pond or lake full of water (better is its running water since oxygenation helps keep moss down.)

    Paint the bottom or float a black pan below the surface and you can get solar evaporation.

    The arched cover can be designed with ribs in it to carry the water down.

    • Man, that brought back memories!

      I built my first solar still in 1966 with a black garbage bag, a washed 3lb. coffee can, 4 ft. of aquarium air tubing, two rocks, and an Army surplus entrenching tool, as a Cub Scout.

      I'd guess that if I could do this from a rough sketch and a basic explanation of how it worked as an 8 year old kid, then a community with adults could also manage.

    • Its a wonder people try to do anything any more - its already been done! How many of these will we need to get the flow rate they're talking about here?

    • by mean pun (717227)

      Brilliant!! And to think that nobody who ever was thirsty and living near the sea thought of that! Let's hope the rest of the world reads Slashdot, because there sure are some world-changing insights on it now and then.

      Seriously: do the math. How many pans do you need to generate a liter per day? How much time does it take per pan to remove the salt, harvest the water, and insert new water? How much area does all this need?

  • MIT = big news (Score:2, Insightful)

    by abigsmurf (919188)
    A lot of these stories make the news not because of their validity, but because they're MIT.

    The headline idea has a lots of flaws. For $8000 you can dig a well and install a pump that can supply the water for 250 people. Not only that, you'd have enough money left over to either cover any repair costs for a long time or to put towards another pump. A lot of African villages already have problems with more complex electric pumps, not being able to afford to pay for maintenance so the pumps sit inactive. T
    • Sigh... (Score:5, Informative)

      by SmallFurryCreature (593017) on Tuesday October 19, 2010 @05:11AM (#33944080) Journal

      Is reading that hard? DISASTER relief. You can't go around digging wells in a hurry. This system is designed to be put aboard an aircraft and flown to a disaster zone in a hurry to be used until normal operations can be resumed.

      It is NOT a permanent solution.

      Maybe if you could grasp this from the summary YOU could have gone to MIT and wouldn't be so upset.

      What really is so hard to understand about the difference between disaster relief techonology and permanent solutions?

      • by abigsmurf (919188)
        I was only giving an example, you're the one that seems to be upset.

        This needs to be set up (need to find a good location, need to assemble it, can't start it working in the night), a steady supply of salt water is needed to feed into it, people need to be trained to clean or change the filters.

        This isn't going to be a rapid response system either. A lot of the examples given in the article (desert farmland, Haiti 1 year on) are situations where a medium to long term solution is needed.
    • Given that it's MIT, the salt water they used was probably provided by either Evian or Fuji.
    • by jelle (14827)
      The salt doesn't clog an RO filter. Salty water is pumped into the filter, and two streams of water come out, one not salty and one more salty than the input. You dump the more salty water back into the ocean and that's how you get rid of the salt. It gets washed you continuously, actually it doesn't have to: The minerals remain dissolved. The filter will last at least months, probably years.

      Sure, wells are a more permanent solution, but can you airdrop a water well, and is it producing drinkable water on t
      • by abigsmurf (919188)
        "Ask your favourite well-driller if he'll let you airdrop him into a remote disaster zone to drill a water well today for $8k"

        Considering lots of wells are dug by people living in these nations, I'd imagine that if you offered someone $8K ($3K more than the typical cost) for a weeks work (depending on the depth and nature of the well), they'd bite your hand off.

        There'd be plenty of money left to transport enough water to last people until the well was ready to use. Alternatively you could just drop a
    • by Locke2005 (849178)
      For $8000 you can dig a well and install a pump that can supply the water for 250 people. Not in a boat, you can't. Nor can you in islands like the Bahamas where there is no salt-free groundwater to pump out. Personally, I think the real market for this is sailing yachts, not disaster relief, but that's just me. As far as the filters, you have a series of filters of decreasing mesh size. The bigger screen filters catch the bigger impurities and are easily cleaned by reversing the flow through them. But I'd
  • Innovation????? (Score:4, Insightful)

    by abarrow (117740) on Tuesday October 19, 2010 @06:49AM (#33944582) Homepage

    Sorry, but this just looks like a bog-standard boat desalinization system hooked up to some solar cells. I fail to see what is so earth-shattering about it.

    • by icebrain (944107)

      The trick for this application (and I don't know if MIT solved it or not) isn't the concept, which is obvious to almost anyone with an engineering or technical background. Rather, it's the implementation that will make it big. Anyone can hook up a desalinization system to solar cells; what you need to be able to do for this situation is make it cheap, light, mass-producible, rugged, reliable, and easy to operate and maintain.

    • by eh2o (471262)

      Actually the project is a testbed for some software algorithms for optimal control of systems in the context of variable power availability (as is the case with solar). Presumably this "smart" controller can achieve significantly higher throughput than a naive approach, for example it can probably optimize the process so that the power-consuming components are operating in their most efficient range over a wide range of input power availability.

      The components of the device are all off the shelf items, the

  • ....The Third Worlders will quickly strip everything shiny off the systems and sell the metal to make a quick buck.

    Not a prediction; reality. I've been there and seen it. Why do you think no-one really gives a damn about Haiti?

  • What would be really impressive is a hydro-powered desalinization plant. Like you put salt water in the top and out the bottom comes fresh water, and the extract goes into a bucket which you can sell to saltwater aquarium enthusiasts.
  • by JimMcc (31079) on Tuesday October 19, 2010 @10:56AM (#33947490) Homepage

    The photo of the unit shows what appears to be a Clark Pump as used in Spectra Watermaker systems. (http://www.spectrawatermakers.com [spectrawatermakers.com]) These are popular in recreation long distance sailboats as they require less power for a given output than traditional RO systems.

    As for reliability and longevity, much depends on the design. If you keep pressures reasonable, and flow excess raw water back to its source, the RO membranes will last many years and thousands of hours of use. The key is not running pressures so high that the membrane gets clogged with solids from the raw water. Pre filtering the raw water also is critical to not fouling the membranes. We run a 30 micron then 10 micron filter before out high pressure pump. The prefilters only need to be changed when fouled so their life span depends on the turbidity of the raw water.

    We live aboard our boat and run a watermaker instead of using shoreside water sources. The unit is not as energy efficient as the MIT units. We have used it for years, have over 500 hours on it, and it has had near zero maintenance. In cold water, currently seawater is about 48F, we get 15gph, at 55F+ we get 18gph which is the max rated output, and above that we need to run at lower pressures to not saturate the membrane. We can get greater throughput by adding additional membranes. Adding a second membrane would double our output. (Sorry for the non metric units.) The Clark Pump system will get lower output, but the longevity of the membranes should be comparable. Membrane prices vary, but are typically in the US$250-US$500 range.

    • by merphant (672048)
      Spectra has been selling a "Solar Cube" [spectrawatermakers.com] system for years now, which seems to be just what these folks from MIT are making. Same application and everything. I wonder how different the MIT thing is.
  • Solar PV? (Score:2, Informative)

    by Eclipse-now (987359)
    The moment I read Solar PV I knew these guys had lost the plot. Why on earth do we need it to even have a pump, let alone moving parts and a costly Solar PV array to power it? If it's a big enough emergency, dump thousands of "Life Straws" [vestergaard-frandsen.com] into the field and let the wonder of the human mouth suck the water through the straw directly from the river, which filters it by the time it hits the lips. Solar PV? Are they trying to kill people by making this more expensive than it has to be? The Life Straw is also m

Mediocrity finds safety in standardization. -- Frederick Crane

Working...