New Watermaking Technology: Cheap, Low-Energy Consumption

[Cyrus Safdari]

The first entry on my new blog:
The Stranded Sailor

According to a report on research at the Massachussets Institute of Technlogy, scientists at MIT and Korea have come up with a new way to desalinate water using

[S]mall, portable units that could be powered by solar cells or batteries and could deliver enough fresh water to supply the needs of a family or small village. As an added bonus, the system would also remove many contaminants, viruses and bacteria at the same time.

While the report envisions the technology to be primarily used for disaster relief, I think its potential application to boaters is self-evident. Communities that live on small islands and rely on collecting rainwater should also benefit from this new technology.

Traditional watermakers rely on a process called “reverse osmosis” which requires high-pressure pumps to force salty water through special filter membranes that separate the salt molecules from the water.

According to this report, the new approach to desalination is called “concentration polarization” and solves the biggest problems of watermakers: the need for high pressure pumps (and electricity/fuel to power them) and the fouling of osmosis membranes.

The system works at a microscopic scale, using fabrication methods developed for microfluidics devices — similar to the manufacture of microchips, but using materials such as silicone (synthetic rubber). Each individual device would only process minute amounts of water, but a large number of them — the researchers envision an array with 1,600 units fabricated on an 8-inch-diameter wafer — could produce about 15 liters of water per hour, enough to provide drinking water for several people. The whole unit could be self-contained and driven by gravity — salt water would be poured in at the top, and fresh water and concentrated brine collected from two outlets at the bottom.

And here’s the sweetest part:

If properly engineered, the proposed system would only use about as much power as a conventional lightbulb.

Yay! But don’t go tearing out your watermaker just yet — the first commercial systems are not expected to be available for a couple years.

[Abaco]

That would be a beautiful thing. Let's hope they can put the technology into full scale production.

[Cyrus Safdari]

Yeah -- imaging the boon to all of humanity if the sea could be used for drinking water -- CLEAN drinking water!

[Highlander40]

The thing is, an 8" wafer is worth a lot. Think about how many CPU's come out of one wafer.

[scotte]

I'll believe it when I see it. Hype is... well hype. The past few years we've heard that super-efficient, super-cheap solar panels will be here in a year. Hyped, but not delivered...

[GordMay]

Originally Posted by Cyrus Safdari

... And here’s the sweetest part:
If properly engineered, the proposed system would only use about as much power as a conventional lightbulb ...

I wonder what they consider a “conventional” lightbulb?

Assuming 100Watts, a 12V unit would require over 8 Amps (or if 60W = 5A @ 12V).

My old Power Survivor 35 only required 4 A to produce about 6 litres/Hr; or about 10 Amp/Hrs to produce 15 Litres. It was one of the least efficient R/O units of it’s day.

[senormechanico]

Gord,
I agree. Conventional... what's that?
After a factory update to my Spectra, I get 10 gallons per hour at 8 amps at 12 volts.
This "breakthough" sounds like pie in the sky to me.

[daddle]

It'll be cool if it's slower and smaller. The smallest Spectra is still about 10 times too big for me. I'd rather run something small "all" the time quietly than a big heavy machine weekly...

[hummingway]

They do say it uses more electricity then RO. The claim is the lowest consumption of any microfilter which would fit daddle's requirements. The goal seems to be low cost, lightweight, continous production of small amounts of clean water. Probably not being included in the energy consumption is the power to fill the gravity tank as well - it does say it works on gravity feed.

[osirissail]

They also say: "Since the separation occurs electrostatically, it doesn’t work for removing contaminants that have no electric charge." So a lot of harmful stuff can remain in the water put through this system. They suggest using charcoal filtration but that will require pumps and other systems which is significantly increase the power consumption above what R.O. needs.

[juan_grand'e]

Wht use gravity when a mariner could use the motion of their vessel through the water? Maybe use a pipe/tube over the side or towed.
John