Engineers Boost Output of Solar Desalination System By 50 Percent (phys.org) 45
An anonymous reader quotes a report from Phys.Org: Researchers in Rice's Laboratory for Nanophotonics (LANP) this week showed they could boost the efficiency of their solar-powered desalination system by more than 50% simply by adding inexpensive plastic lenses to concentrate sunlight into "hot spots." The results are available online in the Proceedings of the National Academy of Sciences. "The typical way to boost performance in solar-driven systems is to add solar concentrators and bring in more light," said Pratiksha Dongare, a graduate student in applied physics at Rice's Brown School of Engineering and co-lead author of the paper. "The big difference here is that we're using the same amount of light. We've shown it's possible to inexpensively redistribute that power and dramatically increase the rate of purified water production."
In conventional membrane distillation, hot, salty water is flowed across one side of a sheetlike membrane while cool, filtered water flows across the other. The temperature difference creates a difference in vapor pressure that drives water vapor from the heated side through the membrane toward the cooler, lower-pressure side. Scaling up the technology is difficult because the temperature difference across the membrane -- and the resulting output of clean water -- decreases as the size of the membrane increases. Rice's "nanophotonics-enabled solar membrane distillation" (NESMD) technology addresses this by using light-absorbing nanoparticles to turn the membrane itself into a solar-driven heating element. Dongare and colleagues, including study co-lead author Alessandro Alabastri, coat the top layer of their membranes with low-cost, commercially available nanoparticles that are designed to convert more than 80% of sunlight energy into heat. The solar-driven nanoparticle heating reduces production costs, and Rice engineers are working to scale up the technology for applications in remote areas that have no access to electricity.
In conventional membrane distillation, hot, salty water is flowed across one side of a sheetlike membrane while cool, filtered water flows across the other. The temperature difference creates a difference in vapor pressure that drives water vapor from the heated side through the membrane toward the cooler, lower-pressure side. Scaling up the technology is difficult because the temperature difference across the membrane -- and the resulting output of clean water -- decreases as the size of the membrane increases. Rice's "nanophotonics-enabled solar membrane distillation" (NESMD) technology addresses this by using light-absorbing nanoparticles to turn the membrane itself into a solar-driven heating element. Dongare and colleagues, including study co-lead author Alessandro Alabastri, coat the top layer of their membranes with low-cost, commercially available nanoparticles that are designed to convert more than 80% of sunlight energy into heat. The solar-driven nanoparticle heating reduces production costs, and Rice engineers are working to scale up the technology for applications in remote areas that have no access to electricity.
The future! (Score:1, Interesting)
This is how it's going to be ongoing, with "free energy" systems that harness the ambient wasted energies around us that we're not collecting and using becoming more efficient, cheaper, and more widely used.
Now make a million units!
Re: The future! (Score:5, Funny)
Boy are you going to be surprised when you discover where most tap water comes from. To be fair it's probably somebody else's urine and not your own that you're drinking.
Re: (Score:1)
Thanks to the Republican's
Nice try but all Mayor's of Flint Michigan since 1975 have been Democrats [wikipedia.org]
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"For example, maybe they'd rather you drink your own urine rather than drink tap water."
Depending on where in the US you live, it might be better.
The tap water might contain arsenic, lead and it might even burn a little.
Yup $10. Nope! (Score:2)
Re: Yup $10. Nope! (Score:1)
Fluid dynamics are interesting. You never know where fluids will go or how different temperature fluids will behave!
Re: (Score:2)
Its called.. fluid dynamics.
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https://www.pnas.org/content/pnas/early/2019/06/11/1905311116.full.pdf
Or you could click on the 2nd link in the OP, then click where it says 'PDF'
Had you tried to actually read the paper after doing either of those, you would have realized that only gets you the abstract and footnotes. The full paper is paywalled.
Hey look, someone who doesn't understand, is lying (Score:1)
100% False, actually... the salinity of the output is the same. You seem to be implying that's a problem somehow anyway, if it were happening. It's not.
What about the waste? (Score:3)
I'll be more impressed when someone figures out what to do with the waste. If that was solved then the rest of the system can slowly be optimized.
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What can they do with salty water solutions, that's your question? The membrane itself doesn't get changed out 'that often' and really isn't a lot of waste over the life of it considering the output. Salt water goes right on the ground, done.
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Zero liquid discharge and taking advantage of trace minerals in the seawater shows promise, but you are still talking about 15-20 tons of salt waste per US household water consumption per year.
Maybe we can fill back all of those salt mines...
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Also, from a systems perspective, the solution to brine pollution is dilution. Neither the salt nor the water are being created or destroyed by the process, so you are at equilibrium if you distribute the brine waste adequately.
ZLD is a balance to that, especially in areas where there is a trend for increasing salinity over time like Salton Sea, or where you are essentially importing salts or exporting “fresh” water.
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> Maybe we can fill back all of those salt mines...
Just give Applebee's a call.
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Low grade salt is useful in many applications, including cleaning of waste water and removing limescale from underground water. Also handy for use on roads in the winter etc. With a bit of effort it can be consumed by humans too, although we should probably cut back.
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I'll be more impressed when someone figures out what to do with the waste.
You mean the sea salt? Do you have any idea how much people pay for that stuff? Talk about a win-win.
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I'll be more impressed when someone figures out what to do with the waste.
You mean the sea salt? Do you have any idea how much people pay for that stuff? Talk about a win-win.
High-volume desalination would drop the price of sea salt through the floor. Which isn't to say it wouldn't still be saleable. I expect that most of it would simply get dumped back into the ocean, though -- which is completely and totally fine. That's precisely what happens to the same waste that's left behind when water evaporates from the surface of the ocean, except that in that case the quantity is on the order of 38 billion tons per day, on average. Of course, it's also uniformly distributed and wa
Re:What about the waste? (Score:4, Informative)
Dump it in the ocean?
It's not like the pure water produced by the system isn't going to end up back in the ocean anyway....
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The output is 1-1.5x brine to water. The waste is not salt, it is hot brine, which is toxic to aquatic life.
https://www.nationalgeographic.com/environment/2019/01/desalination-plants-produce-twice-as-much-waste-brine-as-thought/
The copper and chlorine that is added to the water in the process (control bateria, corrosion) ends up in the brine too.
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Bonneville Salt Flats Utah.
The place has been loosing usuable area for years. Replentish the salt flat.
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Solar desalination? Let nature do all the work (Score:2)
Just collect what falls out of the sky all by itself and pump it to wherever you need it.