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Science

MIT Researchers Build Solar-Powered Low-Cost Drinking Water Desalination System (mit.edu) 54

MIT engineers have built a solar-powered desalination system that "ramps up its desalting process and automatically adjusts to any sudden variation in sunlight, for example by dialing down in response to a passing cloud or revving up as the skies clear."

While traditional reverse osmosis systems typically require steady power levels, "the MIT system requires no extra batteries for energy storage, nor a supplemental power supply, such as from the grid." And their results were pretty impressive: The engineers tested a community-scale prototype on groundwater wells in New Mexico over six months, working in variable weather conditions and water types. The system harnessed on average over 94 percent of the electrical energy generated from the system's solar panels to produce up to 5,000 liters of water per day despite large swings in weather and available sunlight... "Being able to make drinking water with renewables, without requiring battery storage, is a massive grand challenge," says Amos Winter, the Germeshausen Professor of Mechanical Engineering and director of the K. Lisa Yang Global Engineering and Research Center at MIT. "And we've done it."

The system is geared toward desalinating brackish groundwater — a salty source of water that is found in underground reservoirs and is more prevalent than fresh groundwater resources. The researchers see brackish groundwater as a huge untapped source of potential drinking water, particularly as reserves of fresh water are stressed in parts of the world. They envision that the new renewable, battery-free system could provide much-needed drinking water at low costs, especially for inland communities where access to seawater and grid power are limited...

The researchers' report details the new system in a paper appearing in Nature Water. The study's co-authors are Bessette, Winter, and staff engineer Shane Pratt... "Our focus now is on testing, maximizing reliability, and building out a product line that can provide desalinated water using renewables to multiple markets around the world," Pratt adds. The team will be launching a company based on their technology in the coming months.

This research was supported in part by the National Science Foundation, the Julia Burke Foundation, and the MIT Morningside Academy of Design. This work was additionally supported in-kind by Veolia Water Technologies and Solutions and Xylem Goulds.

Thanks to long-time Slashdot reader schwit1 for sharing the news.
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MIT Researchers Build Solar-Powered Low-Cost Drinking Water Desalination System

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  • I'm confused. There is the concept of using solar energy to produce electricity and there is the concept of using electric power to drive desalination. Old stuff. Is the good stuff here that they connected the two? Maybe I need to read the article. I'm going to Jersey Mike's tonight and get a Philly Cheese Steak Sandwich. But, I'm going to drive a Tesla to pick it up. Get I get funding to do that?
    • Re:Huh? (Score:5, Informative)

      by Torodung ( 31985 ) on Saturday October 19, 2024 @03:28PM (#64877919) Journal

      You needed to RTFS:

      traditional reverse osmosis systems typically require steady power levels

      Solar power is not steady. They figured out how to make the desalination process adjust to the lack of steady power. No batteries either. Just solar panels.

      It's all there. You can safely skip TFA like the rest of Slashdot.

      • This is really the best way to store energy... produce something necessary and easily storable at a variable rate using whatever variable energy is available.

        I wish somebody could set up aluminum smelting to work like that.

        • I'm waiting for heat pumps/air conditioners to work this way too. For example attach solar panels to a building HVAC, without batteries. You'd have plenty of cooling in the summer. It would work during the day, and it could also freeze water, which could be used to cool the building at night. For heating, you might need grid backup, but it might often work without it.
        • by q_e_t ( 5104099 )
          They are working on schemes for aluminium smelting and otter processes using intermittent excess, but it's not easy to design and make it economically viable. If there is no excess power what do you do with the staff not required that day? What if the excess power is at 3am on a Sunday morning?
          • Yeah, other than "automation" I don't know. I'm sure it would already be done if it were easy.
            • by q_e_t ( 5104099 )
              If the process is always running, just more of it some days than others, then people would always be on-site to provide decision-making (there's lots of automation in monitoring always). The issue is having the ability for stop-start processes. Even a biscuit factory can't easily be stop-start given the need to cook the biscuits - you can delay a batch going into the oven but you can't easily turn off the oven half way through without ruining that batch. Even delaying a batch has a time limitation.
      • by AmiMoJo ( 196126 )

        I'm not sure we really need a zero battery solution, given how cheap batteries are now, but it's still an interesting proof-of-concept that demonstrates one way we might take advantage of basically free renewable energy.

        You over-build renewables so that they cover the lowest sun/wind periods, and end up with vast amounts of cheap energy much of the time. Any process that can take advantage of intermittently available energy becomes very attractive. You can easily imagine things like farmers installing large

        • by e3m4n ( 947977 )

          Do you really want your access to disaster relief equipment to be bottlenecked by some embargo china decides to impose as it flexes some level of world dominance? Rare earth metals are a finite resource. We can’t battery every fucking thing. Pretty sure if we BEV every damn car it will bankrupt quite a few supplies of rare earth metals. Plus they are heavy. Not exactly village portable.

          • by AmiMoJo ( 196126 )

            What does China have to do with this? They don't have a monopoly on renewable energy, batteries, or desalination.

            Besides, it's projection anyway.

            • by e3m4n ( 947977 )

              you would be better off taking the residual salts from the process to build ad-hok sodium batteries. you dont need much battery, just enough to serve as a capacitor to fill the gaps if a cloud moves by. Portability is the #1 goal of this. This concept has a 3 pronged approach.

              First sales will naturally go to the Industrial military complex. If you suddenly need to setup a forward outpost somewhere you can air drop something like this, with just enough equipment to dig a very small well and set one of these

    • But, I'm going to drive a Tesla to pick it up. Get I get funding to do that?

      It's one thing to not understand something, but it's quite another to question whether the thing you don't understand was worth funding. Are you a member of congress by any chance?

  • Help me understand - (Score:5, Interesting)

    by az-saguaro ( 1231754 ) on Saturday October 19, 2024 @03:53PM (#64877965)

    When I look at the picture in the article, there is a truck with the solar panel and a trailer with the desalination system. So, it is portable, can be driven where needed. They can process 5000 liters per day, approx 1320 gallons. Water usage statistics in the US can be found online for water districts and municipalities - rates vary some, but 300 gallons per day per household seems to be a fair average. Relatively dry places might use much less, so I am estimating maybe as low as 300-400 liters per day per household, let's say 333. Then 5000 / 333 = 15, so one daily batch of processed clean water can serve a water-frugal household for 15 days. A service could drive a truck around to the customers, spend one day on site to make enough water for one house for 2 weeks, then drive to the next customer, then repeat the circuit every 2 weeks, 14 customers net for each rig. Of course, if used in small villages, the business or process model might be different, one truck making enough water for 15 households, repeat every day. You can scale up the technology, make bigger trucks, put more trucks in service or on site, etc.

    But here is what I don't get. The project engineers seemed to be obsessively, compulsively, morbidly obsessed with minimizing or eliminating battery storage from the process. Why? If their main goal was to prove that they can match load, their machine, to available power, the sun, and thereby keep the equipment running as efficiently as possible using their ideas about control based on frequent sampling - okay, they proved it. But why not use batteries?

    It seems that countless electrical systems are now incorporating battery storage into their machines, even the power utilities themselves. As battery technology and energy storage have developed in the past 10-20 years, it seems like batteries will be a crucial component of nearly all power systems in the future. Why waste capturable energy when you can store it, then use it off hours when the sun isn't shining?

    So, why do these guys want to avoid batteries like the plague? Seems like battery would be a useful component to keep the desalination running "off hours", increasing throughput and net yield, perhaps doubling capacity for each truck.

    Anyone here on Slashdot have experience with these things and has some insight?

    • My guess: Batteries are expensive. Which may affect the "low-cost" aspect of this.

    • my guess is that being able to remove the battery reduces the cost of the device. Which means it is easier to produce more.

      Assuming you can maintain reliability the same, you would rather not have to service a battery, especially in co text with salty water.

    • If the desalination equipment uses 100% of the electricity created by the panels what would be the advantage of adding batteries? Why make water later with efficiency losses if you can make it now without them? And then of course, like others have mentioned, batteries are a lot cheaper than they used to be but they sure aren't free. On the note of trucking the equipment around, that could potentially be useful in some specific scenarios like natural disasters (Actually probably not now that I think about i
    • by q_e_t ( 5104099 )
      Batteries are relatively expensive. That's an issue for initial purchase in areas where both capital and loans are hard to get. With loans it will increase the cost per unit volume of water. Accepting slower output for a lower cost per unit of volume makes sense. Batteries also, to maintain optimal condition, currently require cooling with typical current chemistries. The cooling would also drive up costs, especially in any location that's fairly hot.

      The final use case is more likely a fixed installation in

    • But why not use batteries?

      Cost. That's just it. One word. One simple idea: the idea that not everyone has endless amounts of money to spend on something and that throwing batteries at everything isn't a viable solution.

    • But here is what I don't get. The project engineers seemed to be obsessively, compulsively, morbidly obsessed with minimizing or eliminating battery storage from the process. Why?

      This is very, very obvious if you think of it from a practical standpoint, also meaning cost. The batteries are the most expensive part of the system by far. If you can eliminate them, you can build more systems to handle your needs. Putting it on a truck isn't what makes sense long term, it's what makes sense for a technology demonstrator. It gives you two special abilities, one the ability to trivially re-site the experiment, two you can take it to different places to do demos (and those are just more sit

    • by e3m4n ( 947977 )

      Because rare earth metals are being dominated and controlled mostly by china. This is a finite resource dedicated mostly to EV as of late. Also 300gal per day includes shit like hollywood showers and laundry. In a pinch you can wash your clothes in a wash basin outside with brackish water. Filtered brakish water is sufficient enough to clean yourself with. After seeing the mudpools people in Afghanistan wash their shit in, anything is possible in a crisis. What you beed fresh water fir is drinking and cooki

    • So, why do these guys want to avoid batteries like the plague? Seems like battery would be a useful component to keep the desalination running "off hours", increasing throughput and net yield, perhaps doubling capacity for each truck.

      It's a good question, but I think the engineers might have deliberately avoided batteries for a few reasons.

      First, batteries introduce inefficiencies -- about 10-20% of energy is lost during charging and discharging. For a system that's already dealing with variable energy input from the sun, avoiding this extra layer of inefficiency might make sense. By directly using the sunlight to desalinate water, they can maximize how much clean water they produce.

      Second, batteries are expensive and require maintenanc

  • I thought we already had one of those, and it could provide enough drinking water for the whole country.
    Its called the Gulf of Mexico.

  • by Retired Chemist ( 5039029 ) on Saturday October 19, 2024 @05:20PM (#64878063)
    What ever happened to the basic solar still, that requires no fancy technology at all?
    • by drnb ( 2434720 )

      What ever happened to the basic solar still, that requires no fancy technology at all?

      Thin, rugged, transparent plastic sheets are a marvel of modern technology. :-) So would be glass panels if they were to create some form of greenhouse, or should it be called a wet house?

    • by q_e_t ( 5104099 )
      Efficiency.
    • What ever happened to the basic solar still, that requires no fancy technology at all?

      It's a question of units. They want to produce 5000 litres of water per day, not 5000 micro-litres of water per day.

    • What ever happened to the basic solar still, that requires no fancy technology at all?

      A business can not be built around that; therefore, unless you do it yourself, it will not exist.

  • So the solar panels convert 21% of the sun's energy. So the process isn't about how much sunlight was converted (very little), but rather being able to use as much as available. This is not a breakthrough in solar panels. It is an decrease in energy loss after conversion which was already high.
    • by q_e_t ( 5104099 )
      It's at least as much a way to store any excess power as a usable and storable resource without the need for expensive batteries. If you ran a shoe factory only when there waa excess power you could store excess energy as footwear.
  • So the solar panels convert 21% of the sun's energy. So it's not about how they converted more sunlight. It's about how they lost less energy in the conversion process (which was already quite low). This is an incremental increase in efficiency touted as a breakthrough. This was already possible with batteries. They just happened to change the process to adjust the speed of conversion instead of using a capacitor to store the power until there was enough to perform the conversion. It's a trade-off. Time to
  • For the past 50 years I have been reading about low cost desaliniation systems that will change the world forever.

Blinding speed can compensate for a lot of deficiencies. -- David Nichols

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