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MIT Unveils Portable, Solar-Powered Water Desalination System

Soulskill posted more than 3 years ago | from the water-the-chances dept.

Earth 117

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."

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80 US gallons (4, Interesting)

MichaelSmith (789609) | more than 3 years ago | (#33942870)

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.

Re:80 US gallons (1)

T Murphy (1054674) | more than 3 years ago | (#33942898)

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.

Re:80 US gallons (1)

timeOday (582209) | more than 3 years ago | (#33942964)

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.

Re:80 US gallons (0)

Anonymous Coward | more than 3 years ago | (#33943332)

I fail to see the point. Any random creek has a flow of at least 1 L/s, which is more than what this unit can provide. Just sit next to one with a paper cup and you're all set.

Re:80 US gallons (1)

MichaelSmith (789609) | more than 3 years ago | (#33943500)

Many random creeks have contaminated water. Sometimes boiling makes them drinkable, often not.

Re:80 US gallons (4, Funny)

sempir (1916194) | more than 3 years ago | (#33943736)

Getting random creeks into a C130 has it's own inherent problems...leakage being one. Stacking is another, causes apeshittedness big time.

Re:80 US gallons (0)

Anonymous Coward | more than 3 years ago | (#33943984)

they'll go in there if you weave them

Re:80 US gallons (3, Funny)

deimtee (762122) | more than 3 years ago | (#33944828)

And you really have to be careful not to cross the streams.

Re:80 US gallons (1)

kg8484 (1755554) | more than 3 years ago | (#33944474)

It is for areas of the world where there aren't random creeks (if there were enough random creeks in Haiti, they would be sending water purification tablets and jugs or pots and tea kettles and telling everyone to boil their own water). This is a desalination system, so it can work off of seawater. Industrial scale reverse osmosis desalination plants do exist, showing that there are places where there isn't enough freshwater for the population even in good times.

Re:80 US gallons (0)

Anonymous Coward | more than 3 years ago | (#33944958)

Might I suggest not living in areas which are unlivable?

Re:80 US gallons (0)

Anonymous Coward | more than 3 years ago | (#33945716)

Yeah, like in San Diego where my father-in-law has worked on these plants.

Re:80 US gallons (1)

necro81 (917438) | more than 3 years ago | (#33944866)

Any random creek has a flow of at least 1 L/s, which is more than what this unit can provide. Just sit next to one with a paper cup and you're all set.

If you've got a creek handy that isn't filled with serious pollutants, human waste, decomposing bodies, and loads of pathogens, then yeah, you're idea of relying on random creeks sounds good.

Oh, and be sure to have some cups for the million or so other people who might also want to have a drink.

Re:80 US gallons (1)

JustFisher (1123293) | more than 3 years ago | (#33943376)

"...providing water for more than 100,000 people..." Wow, that's promising.

Re:80 US gallons (5, Interesting)

afidel (530433) | more than 3 years ago | (#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.

Re:80 US gallons (1)

MichaelKristopeit 66 (1920336) | more than 3 years ago | (#33943024)

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.

Re:80 US gallons (1)

kg8484 (1755554) | more than 3 years ago | (#33944410)

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.

Re:80 US gallons (1)

kg8484 (1755554) | more than 3 years ago | (#33944438)

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?

Re:80 US gallons (1)

snookerhog (1835110) | more than 3 years ago | (#33945164)

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.

Re:80 US gallons (1)

afidel (530433) | more than 3 years ago | (#33945320)

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:80 US gallons (2, Insightful)

LongearedBat (1665481) | more than 3 years ago | (#33945610)

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.

Re:80 US gallons (1)

afidel (530433) | more than 3 years ago | (#33946352)

Yeah, after I posted I thought about that. Perhaps having both options available is a good thing =)

Re:80 US gallons (2, Informative)

kurokame (1764228) | more than 3 years ago | (#33942910)

Longer, if they don't like their kids much.

Re:80 US gallons (0)

Anonymous Coward | more than 3 years ago | (#33943848)

"I do the job... and then I get paid. Go run your little world."

Re:80 US gallons (0)

Anonymous Coward | more than 3 years ago | (#33942958)

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.

Wait... are you drinking 8 gallons of water per day? Daily showers are a convenience, not a necessity.

Re:80 US gallons (1)

MichaelSmith (789609) | more than 3 years ago | (#33943508)

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.

Wait... are you drinking 8 gallons of water per day? Daily showers are a convenience, not a necessity.

Washing may be vital after a disaster when disease starts to spread.

Re:80 US gallons (1)

Sarten-X (1102295) | more than 3 years ago | (#33944748)

You can wash with salt water, at least enough to survive.

Re:80 US gallons (1)

DrEldarion (114072) | more than 3 years ago | (#33942970)

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.

Re:80 US gallons (1)

MichaelSmith (789609) | more than 3 years ago | (#33943466)

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.

Re:80 US gallons (0)

Anonymous Coward | more than 3 years ago | (#33943788)

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 a fairly low estimate for daily water intake. Someone outdoors in a hot or tropical environment will require a good deal more than half a gallon a day. Add in physical activity and still more water will be required, the amount increasing as physical activity increases.

Re:80 US gallons (1)

Rogerborg (306625) | more than 3 years ago | (#33944608)

If you're trying to perpetuate the stereotype that nerds don't wash, then congratulations, you win an internets.

Re:80 US gallons (1)

Hognoxious (631665) | more than 3 years ago | (#33944704)

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?

Re:80 US gallons (0)

Anonymous Coward | more than 3 years ago | (#33943114)

I get more water than that per day from the RO/DI (Reverse Osmosis/DeIonization) unit making fresh water for my marine aquariums.

Oh look, they've put a solar panel on a RO/DI unit. Big deal! World news! Fucking modders.

Re:80 US gallons (1)

vegiVamp (518171) | more than 3 years ago | (#33944012)

How much power does that RO/DI unit of yours pull ? Could it run off a solar panel ?

Re:80 US gallons (0)

Anonymous Coward | more than 3 years ago | (#33943214)

or 1 American..

Re:80 US gallons (0)

Anonymous Coward | more than 3 years ago | (#33943946)

or 1 American..

That SUV needs to be washed, too! And I want my damn lush, green lawn in the middle of the desert!

You need 30 liters a day? (0, Troll)

SmallFurryCreature (593017) | more than 3 years ago | (#33944064)

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 relief. Not disaster go away. That comes when the normal systems are replaced. If they ever were there in the first place.

You do know that some people have to carry their water for miles by hand? Do you REALLY think these people carry 30 liters a day for every person? What next, you are going to complain a disaster relief food package doesn't contain Ben & Jerry icecream and that just won't do? Entitled, you sure seem to think you are.

Re:You need 30 liters a day? (1)

MichaelSmith (789609) | more than 3 years ago | (#33944178)

Well you could be right but I was trained to estimate high, deliver low.

Re:You need 30 liters a day? (0)

icebrain (944107) | more than 3 years ago | (#33944482)

Or, maybe you could pull your head out of your ass and wipe the smug off of it. A number like 30L/day isn't just "oh, I feel like drinking a lot of water and taking nice long showers". If you're in a disaster relief setting, you need to account for a lot more than just basic drinking water for otherwise healthy and not super-active people. You're going to be dealing with very dehydrated people, either because they've been trapped for days with no drinkable water, or they have a disease (cholera maybe?) that requires lots of fluids, or they are working their asses off doing rescue and support work and need to replenish fluids lost through sweat. You have medical needs for the water--cleaning and sterilizing linens and instruments, irrigating wounds, replacing fluids lost, and so on. You need water for food prep--rice takes water to cook, for example. If you're planning for contingencies it's always good to make conservative estimates and account for things beyond the bare minimum of water required to stay alive.

And even in situations that aren't disaster areas, wouldn't it be nice if we could supply more water than the absolute bare minimum to people? Maybe you could actually be useful and try to figure out how something like this could improve the lives of people instead of trying to come up with reasons to bash someone else.

Re:80 US gallons (1)

VShael (62735) | more than 3 years ago | (#33944594)

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.

Re:80 US gallons (1)

Pastis (145655) | more than 3 years ago | (#33944674)

Even Lithuania was using more than twice that in 2003:
http://www.grid.unep.ch/product/publication/freshwater_europe/consumption.php [grid.unep.ch]

Re:80 US gallons (1)

VShael (62735) | more than 3 years ago | (#33945862)

You need to pay more attention to this part :
"The leakage in pipes is very high and is often counted as consumption."

Re:80 US gallons (1)

Pastis (145655) | more than 3 years ago | (#33946446)

Try again.

"Leakage is generally high and in many cases 30-50% of the water is lost." Even with that, we have the lowest consumer country using at least as much as what you found to be a enormous amount.

http://www.grid.unep.ch/product/publication/freshwater_europe/images/eurohousehold.jpg [grid.unep.ch]

Logistics, logistics, logistics... (0)

icebrain (944107) | more than 3 years ago | (#33945036)

We could solve a lot of problems by teaching people like you to think of big-picture logistical issues associated with real-world problems instead of jumping on the "lets bash this guy for being 'wasteful' so we can feel better about how 'socially conscious' we are" bandwagon.

30L/day/person isn't unreasonable at all for a disaster relief scenario--if anything, it might be on the low side. I know it makes you feel good to assume GP is talking about luxuries of washing cars and green lawns and long hot showers, but if you're going to try to bash him on the grounds of "not thinking about what the people really need" you really need to think outside the box of "how much water do I drink in a normal, sedentary, climate-controlled day?"

Remember, this device is planned for use in disaster relief operations. You have a lot of things to worry about, like:

Drinking water - When you have a disaster on the scale of Haiti, Katrina, etc. you're going to have a lot of people who have been trapped or otherwise isolated from fresh water, and are severely dehydrated. You will also have rescue and medical workers performing very strenuous physical activity, quite possibly in very hot and humid conditions. People like these are going to need a lot more than the "three liters a day" that some other posters have mentioned. I don't know how much experience you have doing that kind of work, but I've done some disaster cleanup and first responder work in hot and humid locations. I once went through over a gallon of water (about 4L for you metric types) on a single extrication call on the side of the highway in mid-July. All we did was pull the guy out of the car, board and collar him, take vitals, and put down absorbent pads to soak up spilled gasoline, and just doing that took a full gallon to get rid of dehydration symptoms--and I'd been well-hydrated before that point.

Cooking - In a major disaster relief effort, you'll probably see field kitchens preparing basic staple foods. Many of those foods, like rice, require clean water for preparation. You'll also need water for cleaning the cooking equipment.

Cleaning - You need clean water if you're going to be cleaning things. I'm not talking about luxurious hot showers or keeping new SUVs sparkling and shiny. Instead, I'm talking about the basic handwashing, bathing, and hygiene habits that help prevent the spread of some really nasty diseases. Or the laundering of field hospital linens and steam sterilization of surgical instruments, or irrigation of wounds to flush out debris. Or washing off days of accumulated mud, dirt, and other nastier things from people that have been trapped in buildings, or those who helped pull them out. You also have to account for some amount of vehicle cleaning and maintenance; the helicopters, aircraft, bulldozers, trucks, and other equipment do need to at least have dirt and mud washed off on occasion so they can continue to function, and except for a few special cases, you can't really do that with salt water--you'll corrode them out very quickly.

Also, bear in mind that it is sound engineering planning practice to provide some form of margin in an estimate. If you're planning for a disaster relief scenario, you don't base your plans on the absolute minimum of supplies needed for survival when things are functioning normally. Instead, you add margin to account for spillage, leaks, mechanical trouble, evaporation, and so on. It's far, far better to have extra water available than not enough.

So next time, give the poster the benefit of the doubt and try to examine his post before you accuse him of making assumptions and being narrow-minded.

Re:80 US gallons (1)

hesaigo999ca (786966) | more than 3 years ago | (#33945218)

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....

Re:80 US gallons (1)

jellomizer (103300) | more than 3 years ago | (#33945350)

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.

Damn you, science jornalism. (5, Insightful)

kurokame (1764228) | more than 3 years ago | (#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:Damn you, science jornalism. (2, Informative)

wagnerrp (1305589) | more than 3 years ago | (#33942928)

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.

Re:Damn you, science jornalism. (0)

Anonymous Coward | more than 3 years ago | (#33943058)

Did you just search the article for a dollar sign? The $8000 model would provide 1,000 gallons per day. Even if it lasts just a week, you still get 26 tons of water for just $8000.

Re:Damn you, science jornalism. (1)

kurokame (1764228) | more than 3 years ago | (#33943398)

Hi, AC. Since 1000 gallons of water comes out to about 4.2 short tons (1000 gallons * 3785 cc per gallon * 1 g per cc of water / 907185 g per short ton), you would actually get about 29 tons in a week. If you want to round more, 4 x 7 is 28. Congratulations, you can mostly do basic unit conversions. What was your point? Filter cost and maintainability are still major unreported issues. Also, that $8000 doesn't count incidentals - getting the water there, personnel, transportation, distribution.

P.S. if you still think $8000 is a good deal on 7000 gallons, it may interest you to note that distilled water tends to be about $0.70 stateside, or about $4900 for that 29 tons of drinking water. Now, that doesn't get it to your disadvantaged disaster zone either...unless it's also stateside and you can hire a truck for under $2000 plus whatever it would have cost you to transport 7000 gallons of salt water to the site then operate and maintain the equipment for a week...or even rope in some volunteers...

Re:Damn you, science jornalism. (1)

phantomfive (622387) | more than 3 years ago | (#33943060)

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?

Re:Damn you, science jornalism. (1)

kurokame (1764228) | more than 3 years ago | (#33943378)

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 a magazine for popular consumption. You can easily find one-off examples where this article in MAKE is more compelling than this media piece about an MIT project...but that much is meaningless.

Re:Damn you, science jornalism. (1)

MichaelSmith (789609) | more than 3 years ago | (#33943512)

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

Re:Damn you, science jornalism. (2, Interesting)

drinkypoo (153816) | more than 3 years ago | (#33944486)

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.

Re:Damn you, science jornalism. (1)

Engeekneer (1564917) | more than 3 years ago | (#33943594)

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 (2, Insightful)

Anonymous Coward | more than 3 years ago | (#33942904)

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 energy in the solar panel and equipment used up over the equipment's lifetime. Bravo for making it modular, but what went into it is pretty clearly old news.

Re:Not revolutionary (1)

grantek (979387) | more than 3 years ago | (#33943314)

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.

Re:Not revolutionary (1)

delinear (991444) | more than 3 years ago | (#33945306)

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.

Optional attachments... (3, Insightful)

canatech (982314) | more than 3 years ago | (#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.

Cost (1)

sonicmerlin (1505111) | more than 3 years ago | (#33942976)

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.

Re:Cost (1)

Dexter Herbivore (1322345) | more than 3 years ago | (#33943302)

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:Cost (0)

Anonymous Coward | more than 3 years ago | (#33943354)

In australia , the few places that we need water either need it on an industrial scale ie drought struck farmers or there is no water to purifiy.

Re:Cost (3, Insightful)

sempir (1916194) | more than 3 years ago | (#33943792)

Yup...that car and garden water could be better put to use in ..MAKING BEER!

Re:Cost (1)

MichaelSmith (789609) | more than 3 years ago | (#33943542)

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.

Re:Cost (1)

TheCarp (96830) | more than 3 years ago | (#33944630)

May seem funny but you know... will need it for the next one.

Boats (5, Insightful)

WindBourne (631190) | more than 3 years ago | (#33942994)

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:Boats (2, Interesting)

TooMuchToDo (882796) | more than 3 years ago | (#33943318)

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:Boats (2, Informative)

rmccoy (318169) | more than 3 years ago | (#33944912)

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.

Re:Boats (1)

WindBourne (631190) | more than 3 years ago | (#33946136)

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.

Re:Boats (0)

Anonymous Coward | more than 3 years ago | (#33943666)

yeah, the same thing with flying cars!

Try it (1, Interesting)

Anonymous Coward | more than 3 years ago | (#33943064)

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

Re:Try it (1)

dtml-try MyNick (453562) | more than 3 years ago | (#33944700)

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 (4, Insightful)

Prune (557140) | more than 3 years ago | (#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

Re:Question (3, Interesting)

L4t3r4lu5 (1216702) | more than 3 years ago | (#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 (3, Interesting)

Biogenesis (670772) | more than 3 years ago | (#33943826)

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.

A shallow black pan and some clear plastic, (1)

crovira (10242) | more than 3 years ago | (#33943380)

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.

Solar Still FTW!!! (1)

rts008 (812749) | more than 3 years ago | (#33943634)

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.

Re:Solar Still FTW!!! (0)

Anonymous Coward | more than 3 years ago | (#33943786)

I too was a cub scout for all of six months and distinctly remember this. While obviously not as efficient as the MIT solution it's simplicity is probably beneficial in many situations and if the $8000 price tag I saw mentioned in another post is correct then it's about $7995 cheaper too.

Re:A shallow black pan and some clear plastic, (1)

badboy_tw2002 (524611) | more than 3 years ago | (#33943790)

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?

Re:A shallow black pan and some clear plastic, (1)

mean pun (717227) | more than 3 years ago | (#33943832)

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?

Re:A shallow black pan and some clear plastic, (0)

Anonymous Coward | more than 3 years ago | (#33945114)

That will totally supply a thousand liters a day. I'm sure glad this topic came up on slashdot, you may have just saved my island.

Re:A shallow black pan and some clear plastic, (0)

Anonymous Coward | more than 3 years ago | (#33946096)

That's simply too low on the gee whiz, Rube Goldberg, publicity whore scale. Totally unworthy of a highly relevant institution like MIT.

Even if they used some kind of hand pumped pressurization setup, it might have made this thing more practical, but NOoooo.

On a serious note, I can already smell the 2011 Nobel Peace Prize prospects for this team.

MIT = big news (2, Insightful)

abigsmurf (919188) | more than 3 years ago | (#33943796)

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. This desalination plant will have the same issue but with the added expense of filters.

How often do you need to replace the filter? 300litres of salt water means 10kg of salt that presumably is stopped by the filter so it would quickly clog up and have to be rinsed several times a day. More problematic are the 450g of other impurities the filter would pick up that may not wash out. I can't see a filter lasting long.

Sigh... (4, Informative)

SmallFurryCreature (593017) | more than 3 years ago | (#33944080)

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?

Re:Sigh... (1)

abigsmurf (919188) | more than 3 years ago | (#33944536)

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.

Re:MIT = big news (1)

ThatsNotPudding (1045640) | more than 3 years ago | (#33944584)

Given that it's MIT, the salt water they used was probably provided by either Evian or Fuji.

Re:MIT = big news (1)

jelle (14827) | more than 3 years ago | (#33944914)

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 the same day? I mean, this desalination system was designed to "can be cost-effectively assembled from standard parts and put into operation within hours using local human capital."

Try telling a group of desperate and thirsty people in a disaster zone to go digg a well to get their water. They need water first, then they can begin rebuilding their infrastructure.

The benefit of simple water producing systems such as this is not having to bring in all the bottled water and/or generator fuel every day from day one, freeing up the local infrastructure and logistics for other relief/rebuilding efforts.

How many people in disaster area's starved for water know how to dig/drill a water well, or operate the drilling equipment to do so without damaging themselves or the equipment? 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.

Re:MIT = big news (1)

abigsmurf (919188) | more than 3 years ago | (#33946048)

"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 few of these alongside a well worker : http://www.treehugger.com/files/2009/09/water_transport_ross.php [treehugger.com] . Same principle, 1/20th the cost and they have the advantage of working in the dark and providing a way of transporting the water.

Re:MIT = big news (1)

Locke2005 (849178) | more than 3 years ago | (#33947776)

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 be interested in seeing what the total cost of operation for this thing is in the real world too.

will it work on bacon? (0)

Anonymous Coward | more than 3 years ago | (#33944346)

just kidding. great idea. could save many of us?

Re:will it work on bacon? (0)

Anonymous Coward | more than 3 years ago | (#33945712)

Save your bacon?

Innovation????? (3, Insightful)

abarrow (117740) | more than 3 years ago | (#33944582)

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.

Re:Innovation????? (1)

icebrain (944107) | more than 3 years ago | (#33945588)

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.

Overly Complex? (0)

Anonymous Coward | more than 3 years ago | (#33945348)

Is it just me or is this thing overly complex? Pumps? Solar Cells? Electricity? Why not just use the steam cycle? You have 3 reservoirs, One large one with cold salt water on the top, that feeds into a small reservoir that is heated to ~250D by a solar concentrator, steam from it is piped (insulated/non-thermally conductive pipeline) up to an enclosed area on the bottom of the large cold reservoir where it condenses back into water, the salt is left in the small heated reservoir until it is cleaned at night. It probably can't produce as much as MITs device & may require someone to check it every hour or so but its a LOT cheaper, probably $50-100, getting it to fit in a compact area for transport might be difficult but should be possible.

Aha! A flaw in the technology! (0)

Anonymous Coward | more than 3 years ago | (#33945536)

> MIT's prototype can reportedly produce 80 gallons of drinking water per day, depending on weather conditions.

I see it depends on a continuos supply of sunlight; but what if it rains for days in a row?

Re:Aha! A flaw in the technology! (1)

MyLongNickName (822545) | more than 3 years ago | (#33945854)

,i>I see it depends on a continuos supply of sunlight; but what if it rains for days in a row?

I sincerely hope this was a joke or a troll. If the natives can't figure out how to get fresh water when it is raining, then we have a real problem.

Re:Aha! A flaw in the technology! (1)

MyLongNickName (822545) | more than 3 years ago | (#33946034)

And I sincerely hope I figure out how to type tags correctly.

Meanwhile, over in the real world.... (1)

Hasai (131313) | more than 3 years ago | (#33946366)

....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?

That's nice, but... (1)

tompaulco (629533) | more than 3 years ago | (#33946686)

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.

Longevity and Recreational Marine Use (4, Informative)

JimMcc (31079) | more than 3 years ago | (#33947490)

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.

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