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What's the point here? Is electricity even the bottleneck of water desalination? I thought the biggest issue with these plans is the brine. That is the major po

What's the point here? Is electricity even the bottleneck of water desalination? I thought the biggest issue with these plans is the brine. That is the major pollutant, and no amount of solar panels will solve that.

hnhg 5y ago
The article directly addresses your point.
- Johnythree 5y ago
  It doesn't. Any salt extraction creates brine which must be disposed of somehow.
  - neilwilson 5y ago
    The trick is to flow seawater past the still and take only, say, 1% of the water from each litre that flows past, which you can do with a still as opposed to a filter. It's a bit like slingshotting a space probe past venus. Technically to move Venus a bit closer to the sun, but not enough to make a difference.
shoto_io 5y ago
Reading the article might help: > Unlike some desalination systems, there is no accumulation of salt or concentrated brines to be disposed of. In a free-floating configuration, any salt that accumulates during the day would simply be carried back out at night through the wicking material and back into the seawater, according to the researchers.
- andromeduck 5y ago
  It makes no difference how concentrated the output brine is if it's the diluted to same concentration at the outlet and the same amount of fresh water is extracted.
  - Johnythree 5y ago
    You completely miss the point. Extracting fresh water from salt water creates brine and in a large scale plant it is extremely difficult to dilute it sufficiently. The only answer is to pipe the brine into areas with strong currents, or dilute it by distributing it over a very large area.
- spockz 5y ago
  Yes. So it is not an issue for the device. However, the salt does end up back in the ocean where at scale the salt levels will be higher leading to the (edit: local) environmental issues mentioned by the GP.
  - kitd 5y ago
    Is the water cycle not a thing any more?
    - pa7x1 5y ago
      Not an expert but I could imagine some local negative effects. Salt concentration may get higher in the area where the brine is returned. Depending on volume, currents, etc...
    - shellfishgene 5y ago
      A large part of the fresh water generated may be used for watering crops or gardens, and would thus evaporate in part. The evaporated water in desert areas would probably rain back down far way, and take long to mix with the sea near the plant again. For example, the Red Sea has much higher salinity that other oceans due to high evaporation and narrow connections to the other oceans. I doubt the effect is large though.
      - EricE 5y ago
        Indeed - the dead sea has stupid high salinity because the only way water leaves is via evaporation :) It is a very odd sensation to "swim" in the dead sea. Even floating is pretty hard because you are so buoyant. It's probably the closes to true weightlessness I will ever get.
  - FartyMcFarter 5y ago
    The sea is a big place. I could imagine perhaps some very localised effects near the plant, but even this isn't obvious.
    - 5y ago
- Johnythree 5y ago
  Your rely is not helpful. The problem with any desalination system is that it creates brine. And brine in large amounts is toxic to the marine environment. The only difference with this example is its small scale. Once it is scaled up it will have the same problem as any existing desalinating plant.
  - ghshephard 5y ago
    But you would never scale this system up - it's entirely inefficient compared to reverse osmosis, on a cost basis. This is the type of system that you would use for just a few people, and as such - brine would never be an issue.
Arnt 5y ago
Brine is the biggest issue with some desalinators, not this one. Power can be a constraint, too. It depends on how much power you have available or can pay for, how much fresh water you need and how pure, how much you can buffer, etc. In short, power/cost is a constraint sometimes.
connorproctor 5y ago
This doesn’t use electricity at all, the “solar power” is heat from the sun causing the water to evaporate. It’s a still, not a filter. According to the article the salt/brine freely flows back into the body of water.
- Johnythree 5y ago
  Which by definition will increase the salinity in the local environment.

hnhg 5y ago

The article directly addresses your point.

Johnythree 5y ago
It doesn't. Any salt extraction creates brine which must be disposed of somehow.
- neilwilson 5y ago
  The trick is to flow seawater past the still and take only, say, 1% of the water from each litre that flows past, which you can do with a still as opposed to a filter. It's a bit like slingshotting a space probe past venus. Technically to move Venus a bit closer to the sun, but not enough to make a difference.

shoto_io 5y ago

Reading the article might help: > Unlike some desalination systems, there is no accumulation of salt or concentrated brines to be disposed of. In a free-floating configuration, any salt that accumulates during the day would simply be carried back out at night through the wicking material and back into the seawater, according to the researchers.

andromeduck 5y ago
It makes no difference how concentrated the output brine is if it's the diluted to same concentration at the outlet and the same amount of fresh water is extracted.
- Johnythree 5y ago
  You completely miss the point. Extracting fresh water from salt water creates brine and in a large scale plant it is extremely difficult to dilute it sufficiently. The only answer is to pipe the brine into areas with strong currents, or dilute it by distributing it over a very large area.
spockz 5y ago
Yes. So it is not an issue for the device. However, the salt does end up back in the ocean where at scale the salt levels will be higher leading to the (edit: local) environmental issues mentioned by the GP.
- kitd 5y ago
  Is the water cycle not a thing any more?
  - pa7x1 5y ago
    Not an expert but I could imagine some local negative effects. Salt concentration may get higher in the area where the brine is returned. Depending on volume, currents, etc...
  - shellfishgene 5y ago
    A large part of the fresh water generated may be used for watering crops or gardens, and would thus evaporate in part. The evaporated water in desert areas would probably rain back down far way, and take long to mix with the sea near the plant again. For example, the Red Sea has much higher salinity that other oceans due to high evaporation and narrow connections to the other oceans. I doubt the effect is large though.
    - EricE 5y ago
      Indeed - the dead sea has stupid high salinity because the only way water leaves is via evaporation :) It is a very odd sensation to "swim" in the dead sea. Even floating is pretty hard because you are so buoyant. It's probably the closes to true weightlessness I will ever get.
- FartyMcFarter 5y ago
  The sea is a big place. I could imagine perhaps some very localised effects near the plant, but even this isn't obvious.
  - 5y ago
Johnythree 5y ago
Your rely is not helpful. The problem with any desalination system is that it creates brine. And brine in large amounts is toxic to the marine environment. The only difference with this example is its small scale. Once it is scaled up it will have the same problem as any existing desalinating plant.
- ghshephard 5y ago
  But you would never scale this system up - it's entirely inefficient compared to reverse osmosis, on a cost basis. This is the type of system that you would use for just a few people, and as such - brine would never be an issue.

Arnt 5y ago

Brine is the biggest issue with some desalinators, not this one. Power can be a constraint, too. It depends on how much power you have available or can pay for, how much fresh water you need and how pure, how much you can buffer, etc. In short, power/cost is a constraint sometimes.

connorproctor 5y ago

This doesn’t use electricity at all, the “solar power” is heat from the sun causing the water to evaporate. It’s a still, not a filter. According to the article the salt/brine freely flows back into the body of water.

Johnythree 5y ago
Which by definition will increase the salinity in the local environment.