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This chunk from the article is, unfortunately, an outright lie. By definition, removing salt from seawater leaves you with water and salt. The article handwave

by dsr_ 5y ago

This chunk from the article is, unfortunately, an outright lie. By definition, removing salt from seawater leaves you with water and salt. The article handwaves the salt away by supposing that the desalinator will float on top of the ocean. In actual production configurations other than towing it behind your sailboat, you will end up with a brine pool that needs to be disposed of, or a concentration in the wicking material that prevents low-concentration seawater from entering, or a pumping system. This is not just a common negative externality, but a casual lie about it.

KaiserPro 5y ago
> supposing that the desalinator will float on top of the ocean. I think that as its solar, you only have 50% duty cycle (more or less) so the idea is that you "just" slow down the water supply to remove the salt over night.
adrianmonk 5y ago
I don't think they are talking about the impact on the environment. I think they are talking about the procedures for operating the equipment. The way I read it, they mean whoever operates this device does not have to periodically go empty some bin/tank of salt or brine. An analogy would be to a frost-free refrigerator. When you say the freezer compartment of your fridge is frost-free, you don't mean that it never generates frost. You mean it does generate frost, but it also automatically removes it. It's "free" of frost in the sense that you are free of doing a chore that you have to do with a freezer that lacks this feature.
- dsr_ 5y ago
  If you operate it directly on the open ocean, towing it behind your sailboat, you don't have to do anything special. If you operate it in a commercial, protected context where you pump water through it, you will generate brine. If you operate it en-masse in the ocean, the things that are insignificant at the scale of 1 and 10 square meters may become significant at the scale of 1 and 10 square kilometers. All of these things are true for other desalinization systems, too. Claiming "you don't have to worry about brine" because it floats on the water surface is misleading at best. You can put any system you want on the water and make it float -- we have concrete and steel hulls, no problem -- but that doesn't solve the concentration problem.
  - jonas21 5y ago
    It sounds like they're targeting small deployments in the developing world, at the scale of 1 to 10 square meters, not large commercial systems. From the article: > In production, they think a system built to serve the needs of a family might be built for around $100... The hope is that it could ultimately play a role in alleviating water scarcity in parts of the developing world where reliable electricity is scarce but seawater and sunlight are abundant. The problem with brine from desalination plants is that it's released at high concentration in one spot. This would not suffer from that problem.
EricE 5y ago
Water in open ocean is not still - there are currents. I suppose if you had a large enough operation you could create a gradient of sufficient size to be self-sustaining without further mechanical agitation (such as your example of towing behind a ship). It would be an interesting exercise to see a large collection of these in operation. Heck even if you had to pump ocean water on land and back out to dilute the brine this process would still use significantly less energy overall than current desalinization plants. Speaking of current plants, a recently constructed one in Carlsbad CA leverages the cooling outflow of a power plant to handle the dilution. The power plant was already there and so was the outflow - these things can be planned to leverage overlapping uses to further increase efficiency.

by dsr_ 5y ago

KaiserPro 5y ago

> supposing that the desalinator will float on top of the ocean. I think that as its solar, you only have 50% duty cycle (more or less) so the idea is that you "just" slow down the water supply to remove the salt over night.

adrianmonk 5y ago

I don't think they are talking about the impact on the environment. I think they are talking about the procedures for operating the equipment. The way I read it, they mean whoever operates this device does not have to periodically go empty some bin/tank of salt or brine. An analogy would be to a frost-free refrigerator. When you say the freezer compartment of your fridge is frost-free, you don't mean that it never generates frost. You mean it does generate frost, but it also automatically removes it. It's "free" of frost in the sense that you are free of doing a chore that you have to do with a freezer that lacks this feature.

dsr_ 5y ago
If you operate it directly on the open ocean, towing it behind your sailboat, you don't have to do anything special. If you operate it in a commercial, protected context where you pump water through it, you will generate brine. If you operate it en-masse in the ocean, the things that are insignificant at the scale of 1 and 10 square meters may become significant at the scale of 1 and 10 square kilometers. All of these things are true for other desalinization systems, too. Claiming "you don't have to worry about brine" because it floats on the water surface is misleading at best. You can put any system you want on the water and make it float -- we have concrete and steel hulls, no problem -- but that doesn't solve the concentration problem.
- jonas21 5y ago
  It sounds like they're targeting small deployments in the developing world, at the scale of 1 to 10 square meters, not large commercial systems. From the article: > In production, they think a system built to serve the needs of a family might be built for around $100... The hope is that it could ultimately play a role in alleviating water scarcity in parts of the developing world where reliable electricity is scarce but seawater and sunlight are abundant. The problem with brine from desalination plants is that it's released at high concentration in one spot. This would not suffer from that problem.

EricE 5y ago

Water in open ocean is not still - there are currents. I suppose if you had a large enough operation you could create a gradient of sufficient size to be self-sustaining without further mechanical agitation (such as your example of towing behind a ship). It would be an interesting exercise to see a large collection of these in operation. Heck even if you had to pump ocean water on land and back out to dilute the brine this process would still use significantly less energy overall than current desalinization plants. Speaking of current plants, a recently constructed one in Carlsbad CA leverages the cooling outflow of a power plant to handle the dilution. The power plant was already there and so was the outflow - these things can be planned to leverage overlapping uses to further increase efficiency.