A new solar desalination system takes in saltwater and heats it with natural sunlight. The system flushes out accumulated salt, so replacement parts aren’t needed often, meaning the system could potentially produce drinking water that is cheaper than tap water.
Engineers at MIT and in China are aiming to turn seawater into drinking water with a completely passive device that is inspired by the ocean, and powered by the sun.
In a paper appearing today in the journal Joule, the team outlines the design for a new solar desalination system that takes in saltwater and heats it with natural sunlight.
The researchers estimate that if the system is scaled up to the size of a small suitcase, it could produce about 4 to 6 liters of drinking water per hour and last several years before requiring replacement parts. At this scale and performance, the system could produce drinking water at a rate and price that is cheaper than tap water.
Article doesn't mention what the unit does with the salt waste.
I support this 100%, but desalination presents a unique problem: what do we do with all the salt? Maybe the unit uses it for something, but otherwise it just miniaturizes a problem that we're already working on.
If this works, it's better than anything we have , which costs grid energy and dumps brine all the same. If anything, the smaller scale makes it easier to distribute and dilute the output brine.
If sea levels rise as much as they're supposed to, this will be an invaluable tool for an enormous proportion of the country. My concern comes from capitalism getting its hooks into this.
Evaporate it to solid, store it if need be, or distribute it back into the sea in absorbable chunks. The water's ending up back in the sea eventually anyway, see water cycle, so it should be zero sum, just need to avoid local overloads. Seems eminently solvable.
Sounds so easy for you but what to do with the excess salt is the only real problem with desalination that we have for decades now. It's not easy to solve.
Thats the big ecological question. If we do this at scale, we'll be releasing more briny water back into the sea than we take. Over time on industrial scales, what will this do to the oceans? Is the increased salinity negligible, even at large scales? Or will it cause marine wildlife to die out?
Think of it this way. Burning a pile of wood generates CO2. So first burning a bunch of gas or coal. A couple campfires won't make a dent on the atmospheric composition. It's only when we go this en masse and at industrial scales that we add appreciable CO2 to the atmosphere and cause global warming.
The ideal way to handle desalination would be for us to use the salt that's produced, so the concentration in the ocean remains unchanged with respect to desalination.
Suitcase sized device? Only one or two of them nearby? Then that's not a problem.
If you scale it to industrial sizes/quantities then the extra salinity in the area where you dump the waste products becomes an issue.
Eg my coastal city uses about 135 megalitres of water a day. Supplying all that from seawater requires you to put about 5 metric tons of salt somewhere, every 24 hours.
Stick 5 tons of salt a day directly in one place in shallow waters just offshore and you'll end up with a dead zone a mile wide pretty quickly.
So now you've got to water that salt down into something that's only slightly saltier than usual and that can be difficult because for my example 135 million litres of water a day, you want to dilute the waste by at least 10x that (to make it approx 10 percent saltier) and now you're cycling a billion-plus litres a day around the place.
So this is pretty cool stuff, but just need to be careful with the side effects when it's scaled up.
It's able to successfully reject the salt waste, which is a success. The question will be if it can reject enough of it.
The brine itself though is a really good question. I think there's some existing uses for it, but we'd probably need to think of new applications for it as well.
I think the unit dumps it back into the surrounding water. I don't think this will replace large scale reverse osmosis, but if it can produce enough for a couple people and not require external power, replacement filters, or frequent maintenance, then it's has potential use for costal communities.
You put it back in the ocean. Laughable to think you would alter the ocean's salt content this way. All of the freshwater produced would eventually end up back in the ocean anyway.
On the large scale this is true, but the problem is that the concentrated brine doesn't instantly dilute back into the entire ocean. In large quantities, the waste outflow would damage the local coastal ecosystem before it was sufficiently diluted.
This sounds fantastic on its face, but I seem to keep on hearing about how desalination will solve all kinds of problems and we still have this particular problem.
The missing piece, it seems, is the will for it to be used as infra at scale. Meanwhile selling bottled water taken for free from public lands for several dollars a liter in single-use bottles remains a multi-billion dollar industry. (an industry, I might add, that is aggressive about lobbying to protect its interests)
Devices like this are a lifeline for communities in developing nations. Who are the first and worst affected by water shortages and salt water intrusions into their fresh water sources.
That's pretty unlikely, given that the water systems are more of less closed, and the volume of water in the oceans is so massive that it wouldn't make an appreciable difference at any reasonable scale.
Keep in mind that this isn't the creation of desalination, just making it cheaper. There are already plants that do this at a scale of 50 million gallons a day, or under 1 trillionth of the oceans.
Localized salinity changes are more likely to be an issue, but for that I think they just mix that salt back in with processed waste water, making it roughly neutral.
If care isn't taken to avoid concentrating brine going back in just one spot, sure that could create localized problems. Buuut, you realize that the oceans constantly lose water to evaporation and their salinity is more or less stable, right? Every bit of rain or snow that falls on land (most of which returns to the ocean eventually) is water the ocean can be without and still not too salty for life.
Speaking of salinity, the Atlantic Meridional Overturning Current (which in normal conditions, is the deep/cold return current from the gulf stream -> North Atlantic) is running into a big damned problem because Greenland is melting and all that fresh water pouring off of it is disrupting the return flow of cold water to the tropics. That's why the Gulf Stream has been so hot- it's not getting return feed from its radiator in the North Atlantic, and meanwhile the North Atlantic is getting colder because it's not cycling water back south, and that prevents hot Gulf Stream water from getting there.
Edit: I recently learned that concentrated brine regions in the oceans (called brine pools) are a thing. There are massive salt deposits (as much as 8km thick) under the bottom of the Gulf of Mexico today, the legacy of a time when the gulf was closed off from the oceans- when it refilled, the salt layer was covered over. Today, the deposition on top of it is heavy enough that subsidence within it squeezes the softer salt around, occasionally exposing that salt to the ocean water.
The oceans have been collecting salt from runoff for billions of years, humans reintroducing some of that salt before the water will not affect ocean salinity.
Considering how many people live near the coast it would still be a huge step forward. Right now even for most coastal cities desalination isn't cost effective and they have to import water from inland.
And by not having to deliver as much water from inland to the coast that water can be distributed more for people living inland.
Yes, it's not going to make inhospitable areas liveable but it's not just "cool".
the issue with water networks is they work great when you have the source (usually dams) upstream, water essentially is gravity fed throughout the network with only some localised pumping for certain elevated locations. wastewater again gravity fed towards treatment plants at the lowest point (usually the ocean), so usually, its fairly efficient, despite still requiring enormous amounts of energy.
this doesnt solve that. it has the source where the end point is. the desalinated water needs to be pumped up, to then be gravity fed through the network. In some places, it is worth the cost and energy due to water scarcity, and im not knocking the technology. but claiming its cheaper than tap water is patently false because the distribution cost is far higher
True...otherwise it's reverse hydro, which could be done with surplus renewables at peak times, but not at more than 10km.. This is mostly aimed at coastal communities (and sustainable floating villages 😁)
...or you could say fuck it, go full Dutch and build wind turbines and reservoirs everywhere to get water to all crops and green deserts 😊.
Since this produces distilled water, I imagine you could use it to filter any water, not just saltwater. You'd still need to boil it to make sure it was free of pathogens, in either case, and add an appropriate amount of salts and minerals back in to make it potable for the long term.
You're correct about readding a small amount of salts and minerals, but you may not actually need to boil it. Often the membranes used for distillation have pores that are so small that only individual atoms can go through them, which effectively filters out bacteria and virions.
SONOFABIT*H, I've been working on a project exactly like this with my friend for a couple years. Hella congrats they got it done and working first but damn :'( I was too slow.
Imma go sadly crush some bugles with my face stones now
Maybe you could contact them to do some joint work? If they've proven out the concept, the next step is scale up. And that's a gigantic fucking step. I should think they'll want people who are very familiar with the technology instead of people they have to train from the start. Alternatively, since this is in academia, you could work with them on commercializing it.
You've got options! I think it's probably wise to consider your next moves at this point, since they'd be likely to beat you to a patent :/.
Good luck my friend, I'm rooting for you! And if I had more expertise in transient fluid and heat dynamics I'd offer some of my help.
All this stuff is like planning to colonize mars before we stop destroying earth. There is plenty of water if we just stop fucking pumping it all out and wasting it.
you know how we can stop the massive drain on the aquifers? by not allowing everyone to tap it as much as they want, farmers will have to deal with 30% fewer yields on corn, Nestle 'n Co. will lose their money printer, but that's all we would need to save the American aquifers, to STOP FARMING INT THE DESERT
Clean freshwater isn’t evenly distributed across the world and it’s not easy or cheap to transport. This kind of tech can help the people that will be most impacted by climate change to survive.
I feel like every week we hear about some huge breakthrough that is supposed to revolutionize clean drinking water technology and save the world, but nothing ever comes of it.
I know this stuff takes time to develop, and not every idea is going to work, but it would be nice if one of these things actually did pan out and start being useful to solve our drinking water issues.
It's unfortunately not a profitability issue, at least not necessarily. I wish that it was, because then all you need is investors like silicon valley and you can run at a loss.
What the researchers have created here is a bench top device. It needs to be scaled up for widespread commercial use, and that's where things get difficult. Scale up is one of the things my field does, although I don't have personal experience with it. Scale up is where a lot of projects die because of new issues developing.
This device is relying on flow patterns and convection currents. That gives me some concern actually, because these patterns can change a lot with larger vessels. A common industry problem with fluid flow in larger tanks is that you'll get "dead zones". The internal flow dynamics are such that some parts of the vessel see no actual flow, and it's just stagnant. That's a big problem when you're relying on flow to keep your entire tank cool or to carry out precipitated salts.
It's a matter of scale. You first try designs and concepts on a bench top scale in a lab. If that works, you scale the project up. And that scale up can reveal myriad problems. The internal heat and flow dynamics are going to change, and that may require a lot of adjustments. Specifically in this case, you may find that salt deposition is negligible at bench top scales, but when you start exploring larger units, salt ends up accumulating and causing issues. Scale up is part of the scientific process like any other, and it can end in failure unfortunately.
As soon as I saw the words “powered by the sun” in the synopsis, I knew what this was. I learned this during survival training, it’s a great way to turn piss (or any other undrinkable water) into clean water. And yeah, all you need is some plastic and a cup. Let the water evaporate (power of the sun) and collect the droplets in something. Had no idea that needed a science paper.
Here’s the problem with desalination, tho: what do you do with the leftover super-brine? It’s pretty gnar stuff, like almost poison. Wide-scale desalination would produce tons of it every day. Most solutions i’ve heard are like “just dump it back in the ocean!” Which, yeah, how could that ever go wrong?
Exactly, imagine how much water can you gather in a hot climate that doesn't evaporate untilyou get it or grow algae/fungi/protozoa/things that aren good for you.
It's a good title. They don't know if it will be cheaper or not until they go and actually scale it up. Based on the prototype their projections say it should but it's very likely they would run into issues that drive up the cost.
The massic heat capacity of water is 4184 J⋅kg⁻¹⋅K⁻¹. To heat one 1 Liter (1 kg) of water from 30ºC to 100ºC it would take 4184×(100-30) = 2.929e5 J. We want 4 liters however, so we multiply that by 4 and get 2.929e5 J × 4 = 1,172e6 J To then turn that heated water into vapor it would require some more energy. The vaporization enthalpy of water is 4,066e4 J⋅mol⁻¹, and has a molar density of 1,80153e-2 kg⋅mol⁻¹(so 4 liters (4 kg) of water in moles would be 4 / 1,80153e-2 = 2,22033e2 mol), which means that to vaporize the four liters of water we would need 2,22033e2 × 4,066e4 = 9,028e6 J (I think I might have made a mistake here somewhere, because I don't think it would only need 8 times more energy to completely vaporize the water, compared to the amount of energy required to heat it, but I can't find the problem). So the total energy to heat and vaporize 30 ºC water would be 9,028e6 + 1,172e6 = 1.020e7 J
Let's take a 55x40x23 cm suitcase. And let's assume a solar irradiance of 1000 W⋅m⁻² (which is what this site says is a normal solar irradiance to be expected on a clear day on the equator). Let's assume three faces are exposed to the sun and all equally so (three faces receive 1000 W⋅m⁻² while the other three receive none, which would not happen since on a rectangular cuboid, like a suitcase, you can't have all three faces facing directly towards the sun). The box would be receiving (0.55×0.40+0.40×0.23+0.55×0.23)×1000 = 438.5 W, which means that over one hour (3600 s), it would receive 438.5×(3600) = 1,5786e6 J, which is less than the required 1.020e7 J (by almost an order of magnitude), so it wouldn't be possible to heat and vaporize 4 liters of water in an hour.
You're assuming that all heat energy input leaves with the water once it vaporises, which is unnecessary and indeed undesirable.
If you use the incoming water to condense the output vapor, you can recover and reuse a lot of the heat energy, plus you get output water at a much more reasonable temperature.
Nothing. These so called miracle bullshit devices shows up annually at random times to over promise under deliver so that media will talk about and gullible people lose their money on.
consumers already have tap water for comparison hence the title of it suggesting to be cheaper. Not as altruistic. Agreed it could help someone who doesn’t have accesss. But I disagree that simply taking it as an option of the two because one seems cheaper is not actually cheaper so much as an impact that everyone should turn to it as a sole option that is not being considered here.
If you read about this device you’ll find it’s solar powered. Solar powered desalinization boxes are nothing new, but this one doesn’t get clogged quickly like previous models have. If it scales up as well as they’re hoping this could really help a ton of people.
Solar panels also have an issue that come with it covering the earth with more black surface which is negating the point of what the ice was doing to cool the earth before it melted. Ocean water is black and solar panels are black. This is known as albedo effect.
then you have the issue of helping people. Sure, helping people who have NO ACCESS TO WATER this should definitely be an option.
But offering it to people whom already have tap water and access to water as a secondary ‘cheaper’ option is not so altruistic particularly if we don’t consider the impact as the aforementioned non reflective surface that is a much bigger impact on global warming. Hence that solar panels aren’t an all-source solution for the overall issues.
Not from Israel but our entire water system is desalinated and I've never experienced any issue with the taste, in fact the opposite is true. Pure clean drinking water.
I will agree with the hardness aspect but other than that it's perfectly good, i've tasted worse bottled mineral water.
This circulation, combined with the sun’s heat, drives water to evaporate, leaving salt behind. The resulting water vapor can then be condensed and collected as pure, drinkable water.
This is not a chemical desalination. It's a classic solar distiller. The output is distilled water. You actually want to cut it with a bit of seawater, because drinking distilled water pulls salts and minerals out of you, and then you die.
Drinking distilled water is actually not that dangerous, so long as you get salts some other way (food!). In order for distilled water to cause runaway deplasmolytic processes, you'd need to spend a lot of time only drinking that, afair from high school bio.