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MIT Unveils Portable, Solar-Powered Water Desalination System
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."
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.
http://michaelsmith.id.au
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, 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...
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.
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.
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.
I prefer the "u" in honour as it seems to be missing these days.
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
"Politicians and diapers must be changed often, and for the same reason."
Yup...that car and garden water could be better put to use in ..MAKING BEER!
A closed mouth gathers no foot.
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.
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?
MMO Quests are like orgasms:
You may solo them, I prefer them in a group.
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.
The photo of the unit shows what appears to be a Clark Pump as used in Spectra Watermaker systems. (http://www.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.
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" 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 more flexible. People sometimes need to be on the move in emergencies. They can take their own Life Straw with them, and drink water from whatever river they find on the way.
There are also various bottle-filter versions that also use no power. They don't need it, as the hand cranks the water through the cleaning membranes.
There is also the Watercone, which again is portable, and can desalinate seawater with solar heat (but no Solar PV needed!) http://www.watercone.com/product.html But I guess when you work for MIT's space division and you have to reinvent something as basic as the wheel, one has to spend a million dollars to make a high tech space pen that will work in zero g rather than just use a pencil! The problem here, is we are talking about saving thousands of the world's poor. They can't afford the 'space-pen' version. (Or, more accurately, they can't afford the emergency relief agencies to have cost limit supply). Instead, lets dump thousands of Life Straws and Watercones, and let *people power* and sunlight provide the energy to save their own lives.