I have no idea if this (which I got to via Instapundit and then Walter Russell Mead) is for real, but it sure sounds good:
A defense contractor better known for building jet fighters and lethal missiles says it has found a way to slash the amount of energy needed to remove salt from seawater, potentially making it vastly cheaper to produce clean water at a time when scarcity has become a global security issue.
How does it work?
The process, officials and engineers at Lockheed Martin Corp say, would enable filter manufacturers to produce thin carbon membranes with regular holes about a nanometer in size that are large enough to allow water to pass through but small enough to block the molecules of salt in seawater. A nanometer is a billionth of a meter.
Because the sheets of pure carbon known as graphene are so thin – just one atom in thickness – it takes much less energy to push the seawater through the filter with the force required to separate the salt from the water, they said.
So, is this a genuine prospect, or is it, to use a phrase from an earlier techno comment thread here, geek porn? Mead is careful to say that whereas such inventiveness is, in general, good, this particular inventiveness may come to nothing.
At most sites these days there are either too few comments to be bothering with, or far too many comments to be bothering with. Mead has no commenters at all to tell him if it makes sense to be optimistic about this new technique or not, and Instapundit only has occasional emailed-in updates.
Here, on the other hand, we not only do have comments, but we get a middlingly useful number of comments on most of our postings, and what is more comments that are often well worth reading, especially on subjects like this one.
So, might these carbon membranes work their water purification magic, or is this just hype?
LATER: Tim Worstall explains it a bit more, and there are some interesting comments there also.
How is this different from reverse osmosis? I’m not saying it isn’t – really asking.
What is this now, a Sheldon Cooper fan-blog?
(Graphene sheets, boys and girls, graphene sheets . . . . )
Is it geek pr*n? Impossible to say until we understand the cost model. I’ve absolutely no doubt that it works exactly as advertized – that it does exactly what it says on the tin. The question now is – how much does the tin cost?
llater,
llamas
Alisa – it is reverse osmosis but, apparently, much much more efficient: http://www.adamsmith.org/blog/energy-environment/we-create-resources-by-inventing-the-technology-that-does-so
If it works then I’m pretty sure the costs will plummet in due course.
This seems to be a new take on a fairly old technology. We’ve been using reverse osmosis filtration on a small scale for decades. Some of your fancier yachters, for instance, prefer to transmute seawater into potable water rather than rely on stored water. Therefore, I imagine that this is a real possibility, and may simply have greater applications than previous osmosis technologies. Hmm, there are any number of seacoast cities that could benefit from a great huge freshwater extractor off the coast.
I’d think that an official press release like this from a publicly-held company would get the company in all kinds of trouble with the SEC if it weren’t substantially true: the company’s stock is for sale in a regulated market, and upping its price with the help of a false report would amount to fraud.
On the other hand, ‘they’ have discovered the cure for cancer how many times, now?
Well, we’ll see.
Jamess: thanks. The difference seems to have to do with pressure. Either less pressure is needed (a thinner filter, as mentioned?), or they found a way to apply the same amount of pressure more efficiently – none of the links I see here explain that.
Sounds like MUCH lower pressures than current reverse osmosis filters hence less energy required.
Currently, R/O systems for seawater ( read yachts ) run in the 500 to 100 PSI range.
……… 500 to 1000 …………
Sorry.
You will write
‘read BEFORE you post’
5000 times on the board today after school Jerry !!!
Jerry: right. Question is, how do they achieve the reduction in the required pressure? Thinner filters would do it, I think, but how significant is that? Also, there’s the issue of a filter life-span – the thinner the filter, the shorter its life. Wouldn’t that offset at least some of the savings on energy costs?
I am guessing that it reduces the pressure needed because the filter will have many more holes in it per square metre than existing filters. For a given rate of water production the pressure can be lower. If that is correct you could think of current filters being like a colander and a graphene filter being like a sieve.
The structure of graphene is sheets of hexagonally arranged carbon atoms. The hexagons that make up the graphene will presumably be big enough to let water molecules through but too small to let salt molecules through.
The filter is supposed to be one atom thick graphene. You can’t get much thinner than that.
At today’s costs, it’s approximately $800 to desalinate brackish ground water. To get to seawater is more expensive, $3,000. Agriculture works just fine with a cost of $400/acre foot and a bit higher. If it truly reduces the cost of desalination as advertised by two orders of magnitude, seawater desalination goes to $30/acre foot. If it merely reduces costs by one order of magnitude, seawater desalination for agricultural purposes becomes cost effective at the coast.
If it works, this is a very big deal.
Gareth: indeed, it is the holes’ density rather than thickness that counts.
The problem, as far as I have read, with graphene is that the technology to create large sheets of the stuff does not currently exist, this makes it impractical to use as a filter (the largest sheet so far created is the size of a finger nail). Also I am fairly sure this idea came about quite a long time ago. It is published in my chemistry textbook being my main evidence for this… Again, I would like to emphasise that I could be very wrong or out of date about this.
Also of interest are the second order effects.
If the cost of living in coastal cities in arid regions is decreased, then more people will flock to those coastal cities.
That will increase real estate prices in those coastal cities, up to the point where real estate prices will prevent a further influx of people.
You are free to draw your own conclusions. (But keep in mind the uncertainties about this technology.)
For those who predicted the next world conflict would be over water, this is one of those “up to our armpits in horse manure” moments.
Alisa, I wasn’t aware that holes had “density”. I rather thought they were, well, sort of empty. Live and learn.
🙂
I have been reliably informed that my head is both “dense” and has “a big #$% hole” in it. So apparently holes can have density.
I suspect both the number and through-length of the channels transiting the membrane influence pressure/flow. It is much more difficult to pump viscous liquid through a long hose than through an opening the same diameter as the hose.
What I’m wondering about this is the manufacturing cost of the support matrix. How to support a one atom thick film full of holes and under (still significant) pressure seems to me a non trivial problem.
This could fit in with a ‘big-picture’ idea that I had a while back. Set up power plants along the coast of Australia, of any kind, and use the power to desalinate the water, AND then sell the water to a dirigible, which would carry it inland to whoever would pay for it! A flexible ‘pipeline’ from the coast to all points inland! A further refinement could be to use electrolasys to break the water molecules into hydrogen and oxygen, and sell the hydrogen. The dirigibles could use it for lift and fuel, and sell the cooled liquid hydrogen, which could be burned to give power and water!
If this product is feasible, it could be part of this process.
Couple of thoughts: yes to Midwesterner, it’s flow rate I care about and the cost of it. And not just operating (energy) cost, but capital cost: how long does the membrane last, what cost to produce? And what mechanism clears the clogged up side of the membrane of all the salt so that fresh (salt)water can get to the pores. But don’t despair about this technology, if it has some merit and the cost reductions are anything like hinted at in these comments ($3000 to process a quantity of seawater, $400 as the cost to produce that same quantity of water is attractive to capitalist farmers), there are scads of membrane technologies under development, including customization of the pore sizes to allow passage of specific molecules, or in hand that will be adapted for this application; the underpinning science is already used to design application specific membranes. As someone said, this could be huge. But if Lockheed Martin doesn’t already have patents surrounding the patents, we should probably relax. Too soon to buy LMT.
Instead of aiming for the perfect membrane, if this technology could be used to make a sufficiently cheaper/better membrane that allows reverse osmosis to work on the pressure produce by a typical tidal range then plentiful cheap water should be just around the corner.
The government will then need to work out something else to keep us afraid and reliant on them.
Oh well, Samisdata behind the curve again when it comes to thinking laterally. If you can produce a filter that selective, sea salt isn’t the only molecule can be filtered. You’d be looking at a whole revolution in numerous industries. Initially, maybe, where the capital cost of the filter is less critical.
Here’s a clue. Try gas separation.
Never trust the press release. This *might* reduce the energy cost of RO water by a factor of a few, but not tens, much a hundred. The thermodynamic floor for reverse osmosis is about 0.8 kWhr/m3, and current plants can achieve about 3 kWhr/m3. Granted, cutting energy demand in half would be impressive and useful, but not earthshaking.
This sort of thing happens often, a technical person gives a cool spec, then the marketing person garbles this in the press release.
References:
http://www.ijesd.org/papers/243-B20001.pdf
(see table 1 on page 5)
http://arstechnica.com/science/2011/08/desalinization-is-this-as-good-as-it-gets/
http://urila.tripod.com/
http://urila.tripod.com/Seawater.htm
To clarify, 0.8 kWhr/m3 is the demand for separating fresh water from seawater which has about 35,000 ppm dissolved solids; the osmotic pressure is about 27 bar. Home RO units only have to contend with less than 1000 ppm, and need only the roughly 3 bar of municipal water supply. The worst I’ve measured in Mojave California (where much of the supply is from wells) was about 650 ppm, and the RO unit got that down to 25 ppm in the permeate.