I swear I've heard about this before... is this one of those stories that emerges about a technology that never seems to enter the market? That "super slick" coating for condiment container interiors is another that springs to mind.
Desalinization is already with about a factor of 2 or 3 of the thermodynamic optimum, so improvements can't be revolutionary. Desalinization mostly needs cheap clean energy.
Are you talking about the brine? This is trivial if you just put a pipe a few hundred yards out to sea. The concentration is diluted extremely quickly. (The only exception is if your desalination plant is below sea level because then you have to pump the brine up hill, which costs some energy.)
I've seen the assumption that the brine dissipates quickly challenged.
Fluids can remain subbornly un-mixed, over large distances and for long times. Given that brine is heavier than seawater, it will almost certainly tend to sink and flow along bathymetric contours, perhaps pooling in local low spots. And sealife can be exceedingly sensitive to changes in temperature, ion density, salt content, etc.
This reminds me of a book in which an ecologist described a discussion with a chemist over the concentration of some pollutant in seawater. Roughly, "Assuming a well-mixed solution..." starts the chemist. "How are you planning to stir the oceans?" asks the ecologist....
> A state-of-the-art facility is now within a factor of two of the theoretical energy minimum, and only 25 percent higher than the realistic minimum for the current reverse osmosis process. In short, it’s going to be tough to squeeze too much more energy out of reverse osmosis, and we’re unlikely to find an alternative method of desalination that will provide a significant boost over that.
> But that doesn’t mean that there are no other ways of getting better output for our energy. The total process of desalination turns out to require three to four times the theoretical minimal energy use, since the salt water must be pumped and pretreated, the membranes maintained, and the resulting brine handled afterwards. Some of these things might be amenable to further improvements, and there has been work put into developing membranes that don’t clog up as easily or better pre-filtering of biological materials.
Not really. Basic thermodynamics tells you that if your only input is water with a certain salt concentration and your output is water with a lower salt concentration (plus either brine -- very salty water -- or dry salt), then there is a minimum free energy cost.
> Based on thermodynamic principles and practical kinetic requirements, the theoretical minimal energy for desalination with FO is always higher than that without FO. In other words, using FO cannot reduce the minimum energy of separation.
The idea behind forward osmosis is to replace the salt in water with some other solute, like sugar. A strict 1-particle-to-1-particle replacement can (I think) have arbitrarily low free energy cost, but then you're just stuck with sugar water instead of salt water. In certain special cases this is fine (like for emergency water generation at sea, when you don't mind drinking sugar water). Insofar as low levels of sugar can't be tasted, and insofar as you have access to free sugar, you can avoid the energetic cost of removing some of the salt by replacing it with sugar. But I don't think this is very much before it becomes noticeable, and sugar isn't free.
If you happen to have excess thermal energy from some source, there are also ways to harvest some of this using forward osmosis, but this is really just another way to smuggle in free energy. In principle, you could use the heat gradient to generate electricity and then use that to power normal reverse osmosis, although which is more efficient will depend on the details of your equipment losses.
OK, but then, forgetting about desalination, you'd be able to just build a power plant with this substance and sea water, right? The fact that very few such plants exit then tells us that it would probably be cheaper to just do your desalination with reverse osmosis powered by a conventional power plant.
Baring some yet undiscovered and very bizarre (but thermodynamically viable) chemistry that requires you to involve saltwater in a practical implementation, yes. Otherwise saltwater (which has a positive heat of mixing) is just fighting your actual process.
You can buy that as Rust-Oleum® NeverWet®. It works great at first, but it wears out fast. It works by creating a surface with tiny spikes. Water has so much surface tension that it rolls across the spikes, rather than breaking up and getting down to the base layer. So the contact area is tiny and the adhesion is low.
The surface is fragile, because it's composed of tiny spikes. Rubbing will destroy it. It's hard to fix this, because the property that makes it useful is the same as the one that makes it fragile.
Just a perfect explanation, thank you. There always seem to be those catch-22's in these techs; I just wish the articles didn't come out in this predictable pattern of pulses.
Yes, it is. My understanding is that there are still barriers to producing enough graphene at a large enough scale to make many of its uses commercially viable.
Production appears to be what they are improving here:
> But it has been difficult to produce large quantities of single-layer graphene using existing methods, such as chemical vapour deposition (CVD). Current production routes are also quite costly.
> On the other hand, said Dr Nair, "graphene oxide can be produced by simple oxidation in the lab".
> "In terms of scalability and the cost of the material, graphene oxide has a potential advantage over single-layered graphene."
Is that really still true in the world we live in today though? Previously we were unable to instantly share information so freely and collaborate with people around the world with so little effort.
I'm not saying it shouldn't take time to develop these things, but surely the 30-40 year timeline is significantly reduced due to information sharing today?
I'd question the 30-40 years figure. I suspect "it depends".
Check out the book "Skunk Works" sometime and marvel at what they managed to do on the frontiers with such small numbers of people and crappy computers (with relatively small budgets and tight deadlines to boot).
Peter Thiel riffs on this idea a lot. Despite our incredible advances in computing and networks, it seems like progress in everything else has slowed down. (Randomly found video with his basic stack of points: http://bigthink.com/embeds/video_idea/48434?width=512&height...)
Another example, consider how long it takes to build any skyscraper in the US. This isn't even new tech, it's well understood, but it still takes a long time from planning to legal stuff to the actual construction. And yet there's a guy in China who builds other kinds of skyscrapers at a rate of two floors per day. Slowness is not a fundamental thing.
Indeed; I would assume a big part of the bureaucratic layer exists to make everything work mostly correct even though there will be cheaters and thieves at every stage of the construction process.
I'm sure it's faster now due to reasons you're describing. Also, cold war is gone - so that kind of helps too. Thing is, this isn't your average ruby on rails app and JSON API. Applied research in chemistry, physics, and industrial scale production takes certain breakthroughs, test methodologies, etc. all of which take a lot of talent and money. From what I remember we've seen significant (for certain amounts of significant) funding in applied r&d for graphene around the same time Nobel was won for it in 2010. So, even if r&d is accelerated now significantly, we're still probably at least around 10-20 years away from seeing anything utilising it in a significant and widespread manner.
That speed should be much faster now due to the information age and globalized competition. It may not approach Ray Kurzweil's predictions, but it's certainly shorter than previous generations of commercialization.
I was thinking the same thing although I've been unable to locate the paper that I recall reading about it. There are lots of papers which discuss nano-pores in graphene as membrane but I recall something that required a current in the graphene.
