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This is incredibly inefficient compared to existing desalinization devices. My boat has a watermaker that uses 4w/liter and it isn't even state of the art. This

This is incredibly inefficient compared to existing desalinization devices. My boat has a watermaker that uses 4w/liter and it isn't even state of the art. This is 5x less efficient. It is also incredibly low volume. There is novelty in the method, and in not using filter mediums. But those differences aren't going to matter if it isn't an order of magnitude more efficient. You could buy an inflatable evaporative device off amazon today to desalinate seawater that makes far more water with no electrical input at all. I'm a bit saddened to see this show up on HN after it made the rounds on FB groups a month ago, where it was debunked. The world has fresh water problems and desalinization at scale with higher efficiency would be a huge unlock. That is exciting. But I'm not sure why this particular approach is getting attention given it underperforms so badly. Except maybe that the letters MIT and a lot of journalists that don't care as long as you clicked.

deleted 4y ago
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Commodore63 4y ago
Not using filters is huge! RO watermakers are really sensitive to poor quality water. Algae from last year's heat wave knocked out a lot of watermakers in Pacific waters.
- sitkack 4y ago
  From the paper > The portable system desalinates brackish water and seawater (2.5−45 g/L) into drinkable water (defined by WHO guideline), with the energy consumptions of 0.4−4 (brackish water) and 15.6−26.6 W h/L (seawater), respectively. So it consumes 26Wh/L turning nasty lowtide into drinkable water with no filter. A 300W solar panel could then produce 10L of water per hour for probably 5 hours a day. 50L a day per panel. That is amazing!
kirrent 4y ago
Without knowing more about this device it's a bit hard to make a true comparison to existing marine RO devices but there are a few reasons I've been following with (skeptical) interest: - Low volume - RO devices don't scale down well. The Katadyn 40E is the smallest watermaker I can find and it produces 6l/h. This is an insane amount of water that I have no use for. 10l a day would be enough for two people. Unfortunately there aren't cheaper and lighter options available. - Storage - No pickling would be really nice. - Membrane - Not needing to replace membranes would also be nice. - Efficiency - I don't care too much about efficiency because most of the time during the day we have plenty of power from 400W of solar panels sized for days and days of cloud. That said, smaller RO devices also have poorer efficiency, e.g. 9Wh/l in the 40E. Other results in the literature suggests there could be plenty of room left to improve in efficiency from the MIT prototype. Depending on cost, I think there's a niche for something that addresses the lower end of the market in watermakers.
- unwind 4y ago
  As someone who uses a kitchen more than a galley (i.e. I'm a land crab), I had to look up if "pickling" had a special meaning here. It turns out to be kinda true, nobody is putting components of their watermaking system [1] in acidic solution for preservation and flavor, but they are putting them in sodium metabisulphite solution and that chemical seems to be useful for disinfecting and so on [2]. [1]: https://www.openoceanwatermakers.co.nz/pickling-your-system.html https://www.openoceanwatermakers.co.nz/pickling-your-system.... [2]: https://en.wikipedia.org/wiki/Sodium_metabisulfite https://en.wikipedia.org/wiki/Sodium_metabisulfite
- salty_biscuits 4y ago
  If you can lower the transmembrane pressure you will get less output for less power and no fouling of the membrane. The economics of consumer choice drive design towards higher outputs and fouling.
adrianN 4y ago
I wonder how much energy it takes to make the RO membranes.
Xylakant 4y ago
This device was discussed earlier on HN and that article goes a little further into the design decisions for the device. (1) The focus is not efficiency or volume. It's compact, portable, robust, maintenance free. No filters, no high pressure components, suitcase size, able to use brackish water. They are not trying to solve industrial scale efficient desalination. They are trying to solve small scale portable desalination. You are measuring them against metrics they're not trying to achieve and it's no surprising they fail at this test. (1) https://news.ycombinator.com/item?id=31200793 https://news.ycombinator.com/item?id=31200793, also linked in the article for this post.
- capableweb 4y ago
  Not to mention that the perspective siliconescapee boils down to "You could buy X off amazon today" which is not even possible for loads of people, as Amazon doesn't operate in many countries, and there are plenty of countries where Amazon doesn't even ship to. Then we have the 10% of people who live in poverty and wouldn't be able to afford ordering it anyways. Those are the groups that would be most helped by a device with these characteristics as well (easy maintenance and low ongoing cost).
  - Out_of_Characte 4y ago
    But this device has the exact same problem you're describing, is less efficient, costs more and requires power. Novelty is the only upside
    - Xylakant 4y ago
      The only device I could find on Amazon that fits the description of an inflatable desalination device is https://www.amazon.com/Aquamate-Solar-Emergency-Purification-Inflatable/dp/B004TOAELS/ref=zg_bs_3402151_55/146-1059240-0331150?pd_rd_i=B004TOAELS&psc=1 https://www.amazon.com/Aquamate-Solar-Emergency-Purification... and it reportedly produces between 0.5 and 2 liters of water per day. That’s great if you have none, but the device being discussed here produces substantially more. So it’s not just a novelty thing.
    - 4y ago
beefield 4y ago
> watermaker that uses 4w/liter I think you have a typo there, but I am not sure what you mean. Maybe 4Wh/liter? (Knowing nothing about desalination, that sounds low, though)
- danbruc 4y ago
  Seems about right, the Katadyn PowerSurvivor 40E/12 V mentioned in another comment is 12 V, 4 A and 5.7 l/h, i.e. 8.4 Wh/l.
- helsinkiandrew 4y ago
  Yes, this device (first I found from google) produces 100L/hour using 400 Watts https://www.nauticexpo.com/prod/schenker/product-23417-555673.html https://www.nauticexpo.com/prod/schenker/product-23417-55567...
Cthulhu_ 4y ago
If it doesn't use filter mediums, where does the salt and contaminants go?
- Xylakant 4y ago
  Even devices that use Reverse Osmosis usually don't aim to catch all contaminants in the filter - they use a membrane/filter to separate the clean water output from a waste water stream that contains the contaminants/salts in higher concentration. This device effectively tries to replace the filter/membrane with an electrical current: From https://news.mit.edu/2022/portable-desalination-drinking-water-0428 https://news.mit.edu/2022/portable-desalination-drinking-wat...: > their unit relies on a technique called ion concentration polarization (ICP), which was pioneered by Han’s group more than 10 years ago. Rather than filtering water, the ICP process applies an electrical field to membranes placed above and below a channel of water. The membranes repel positively or negatively charged particles — including salt molecules, bacteria, and viruses — as they flow past. The charged particles are funneled into a second stream of water that is eventually discharged.
- relaxing 4y ago
  Down the drain.
darksaints 4y ago
I don't know why some people are so obsessed with efficiency. Efficiency is, at best, one attribute of many which make something practical. We have had engines that are 50% thermally efficient for decades now, but no automaker has attempted to produce them because they are impractical in hundreds of other ways. Not only would I buy this for my boat, but I would replace my more efficient spectra watermaker with it. Less noise and less maintenance are massive advantages.
- konschubert 4y ago
  Yea. - "This energy storage is only 30% efficient". - "Yes but it's dirt cheap and so is solar peak power."
- ncmncm 4y ago
  Right. Panels are so cheap now that, unless you are limited in how many panels you can physically install, lower efficiency just means another panel. Even then, maybe you cant a pair of them in place of one so one picks up morning light, and the other afternoon.
dragontamer 4y ago
I'd imagine that most beachfront properties have basically unlimited water, but are instead throttled by electricity costs. Output water vs input water efficiency (20% in this case? 1-liter output from 5-liters input saltwater) matters in some cases, but not others. Since we all live in different terrains and locations, some inventions will be useful in some areas, while other inventions are useful in others.
- ncmncm 4y ago
  You can imagine that, but a solar panel is cheap if it delivers 50L/day.
deleted 4y ago
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deleted 4y ago

[deleted]

Commodore63 4y ago

Not using filters is huge! RO watermakers are really sensitive to poor quality water. Algae from last year's heat wave knocked out a lot of watermakers in Pacific waters.

sitkack 4y ago
From the paper > The portable system desalinates brackish water and seawater (2.5−45 g/L) into drinkable water (defined by WHO guideline), with the energy consumptions of 0.4−4 (brackish water) and 15.6−26.6 W h/L (seawater), respectively. So it consumes 26Wh/L turning nasty lowtide into drinkable water with no filter. A 300W solar panel could then produce 10L of water per hour for probably 5 hours a day. 50L a day per panel. That is amazing!

kirrent 4y ago

Without knowing more about this device it's a bit hard to make a true comparison to existing marine RO devices but there are a few reasons I've been following with (skeptical) interest: - Low volume - RO devices don't scale down well. The Katadyn 40E is the smallest watermaker I can find and it produces 6l/h. This is an insane amount of water that I have no use for. 10l a day would be enough for two people. Unfortunately there aren't cheaper and lighter options available. - Storage - No pickling would be really nice. - Membrane - Not needing to replace membranes would also be nice. - Efficiency - I don't care too much about efficiency because most of the time during the day we have plenty of power from 400W of solar panels sized for days and days of cloud. That said, smaller RO devices also have poorer efficiency, e.g. 9Wh/l in the 40E. Other results in the literature suggests there could be plenty of room left to improve in efficiency from the MIT prototype. Depending on cost, I think there's a niche for something that addresses the lower end of the market in watermakers.

unwind 4y ago
As someone who uses a kitchen more than a galley (i.e. I'm a land crab), I had to look up if "pickling" had a special meaning here. It turns out to be kinda true, nobody is putting components of their watermaking system [1] in acidic solution for preservation and flavor, but they are putting them in sodium metabisulphite solution and that chemical seems to be useful for disinfecting and so on [2]. [1]: https://www.openoceanwatermakers.co.nz/pickling-your-system.html https://www.openoceanwatermakers.co.nz/pickling-your-system.... [2]: https://en.wikipedia.org/wiki/Sodium_metabisulfite https://en.wikipedia.org/wiki/Sodium_metabisulfite
salty_biscuits 4y ago
If you can lower the transmembrane pressure you will get less output for less power and no fouling of the membrane. The economics of consumer choice drive design towards higher outputs and fouling.

adrianN 4y ago

I wonder how much energy it takes to make the RO membranes.

Xylakant 4y ago

This device was discussed earlier on HN and that article goes a little further into the design decisions for the device. (1) The focus is not efficiency or volume. It's compact, portable, robust, maintenance free. No filters, no high pressure components, suitcase size, able to use brackish water. They are not trying to solve industrial scale efficient desalination. They are trying to solve small scale portable desalination. You are measuring them against metrics they're not trying to achieve and it's no surprising they fail at this test. (1) https://news.ycombinator.com/item?id=31200793 https://news.ycombinator.com/item?id=31200793, also linked in the article for this post.

capableweb 4y ago
Not to mention that the perspective siliconescapee boils down to "You could buy X off amazon today" which is not even possible for loads of people, as Amazon doesn't operate in many countries, and there are plenty of countries where Amazon doesn't even ship to. Then we have the 10% of people who live in poverty and wouldn't be able to afford ordering it anyways. Those are the groups that would be most helped by a device with these characteristics as well (easy maintenance and low ongoing cost).
- Out_of_Characte 4y ago
  But this device has the exact same problem you're describing, is less efficient, costs more and requires power. Novelty is the only upside
  - Xylakant 4y ago
    The only device I could find on Amazon that fits the description of an inflatable desalination device is https://www.amazon.com/Aquamate-Solar-Emergency-Purification-Inflatable/dp/B004TOAELS/ref=zg_bs_3402151_55/146-1059240-0331150?pd_rd_i=B004TOAELS&psc=1 https://www.amazon.com/Aquamate-Solar-Emergency-Purification... and it reportedly produces between 0.5 and 2 liters of water per day. That’s great if you have none, but the device being discussed here produces substantially more. So it’s not just a novelty thing.
  - 4y ago

beefield 4y ago

> watermaker that uses 4w/liter I think you have a typo there, but I am not sure what you mean. Maybe 4Wh/liter? (Knowing nothing about desalination, that sounds low, though)

danbruc 4y ago
Seems about right, the Katadyn PowerSurvivor 40E/12 V mentioned in another comment is 12 V, 4 A and 5.7 l/h, i.e. 8.4 Wh/l.
helsinkiandrew 4y ago
Yes, this device (first I found from google) produces 100L/hour using 400 Watts https://www.nauticexpo.com/prod/schenker/product-23417-555673.html https://www.nauticexpo.com/prod/schenker/product-23417-55567...

Cthulhu_ 4y ago

If it doesn't use filter mediums, where does the salt and contaminants go?

Xylakant 4y ago
Even devices that use Reverse Osmosis usually don't aim to catch all contaminants in the filter - they use a membrane/filter to separate the clean water output from a waste water stream that contains the contaminants/salts in higher concentration. This device effectively tries to replace the filter/membrane with an electrical current: From https://news.mit.edu/2022/portable-desalination-drinking-water-0428 https://news.mit.edu/2022/portable-desalination-drinking-wat...: > their unit relies on a technique called ion concentration polarization (ICP), which was pioneered by Han’s group more than 10 years ago. Rather than filtering water, the ICP process applies an electrical field to membranes placed above and below a channel of water. The membranes repel positively or negatively charged particles — including salt molecules, bacteria, and viruses — as they flow past. The charged particles are funneled into a second stream of water that is eventually discharged.
relaxing 4y ago
Down the drain.

darksaints 4y ago

I don't know why some people are so obsessed with efficiency. Efficiency is, at best, one attribute of many which make something practical. We have had engines that are 50% thermally efficient for decades now, but no automaker has attempted to produce them because they are impractical in hundreds of other ways. Not only would I buy this for my boat, but I would replace my more efficient spectra watermaker with it. Less noise and less maintenance are massive advantages.

konschubert 4y ago
Yea. - "This energy storage is only 30% efficient". - "Yes but it's dirt cheap and so is solar peak power."
ncmncm 4y ago
Right. Panels are so cheap now that, unless you are limited in how many panels you can physically install, lower efficiency just means another panel. Even then, maybe you cant a pair of them in place of one so one picks up morning light, and the other afternoon.

dragontamer 4y ago

I'd imagine that most beachfront properties have basically unlimited water, but are instead throttled by electricity costs. Output water vs input water efficiency (20% in this case? 1-liter output from 5-liters input saltwater) matters in some cases, but not others. Since we all live in different terrains and locations, some inventions will be useful in some areas, while other inventions are useful in others.

ncmncm 4y ago
You can imagine that, but a solar panel is cheap if it delivers 50L/day.

deleted 4y ago

[deleted]