3 ms·

Like others have said, there will always be a cost X to desalinate water. I think the best way to pay for X, is to use energy from an external source. External

by fallat 3y ago

Like others have said, there will always be a cost X to desalinate water. I think the best way to pay for X, is to use energy from an external source. External from the Earth. I'm obviously talking about the Sun. We could use the removed material as a general filler. I'm sure we can get creative about it. I think the problem is lack of incentives and misalignment of goals amongst people. I truly think if we can figure out how to how to use the most out of the Sun's rays - i.e. as most directly as possible - we will solve all our needs. The energy is truly free to the Earth.

eru 3y ago
You can also work on making that 'X' as small as possible. There's a thermodynamic fundamental lower limit on the amount of energy needed to desalinate water, but it's absurdly small. Much smaller than the amount of energy we use in practice with current technologies. (Just like there's a thermodynamic lower limit on how much energy a computer needs. But it's also extremely low. See https://en.wikipedia.org/wiki/Landauer%27s_principle https://en.wikipedia.org/wiki/Landauer%27s_principle )
- frotaur 3y ago
  Are you sure the thermodynamic limit on water desalination is extremely small ? I was under the impression that the salt bonds dissolved by water are quite strong and thus require a non-negligible amount of energy to reverse (for instance, if you go about it by evaporating the water, it is very much several thousands of order of magnitude above landauer levels). Edit, found in another comment : For example, desalinating seawater with a typical seawater salt concentration of 35 g L–1 (corresponding osmotic pressure of 29.7 bar) and 50% water recovery (i.e., 50% of the feed stream becomes purified water and 50% becomes brine) requires at least 1.1 kWh per cubic meter of purified water. Regardless of the desalination technology, it is impossible to desalinate water using less energy than that determined by eq 12. 1.1 KWh per cubic meter is very much NOT a negligible amount, so the landauer analogy is incorrect.
  - eru 3y ago
    Thanks for looking it up. Could you link to the sources? Thanks! I stand corrected in that case.

by fallat 3y ago

eru 3y ago

You can also work on making that 'X' as small as possible. There's a thermodynamic fundamental lower limit on the amount of energy needed to desalinate water, but it's absurdly small. Much smaller than the amount of energy we use in practice with current technologies. (Just like there's a thermodynamic lower limit on how much energy a computer needs. But it's also extremely low. See https://en.wikipedia.org/wiki/Landauer%27s_principle https://en.wikipedia.org/wiki/Landauer%27s_principle )

frotaur 3y ago
Are you sure the thermodynamic limit on water desalination is extremely small ? I was under the impression that the salt bonds dissolved by water are quite strong and thus require a non-negligible amount of energy to reverse (for instance, if you go about it by evaporating the water, it is very much several thousands of order of magnitude above landauer levels). Edit, found in another comment : For example, desalinating seawater with a typical seawater salt concentration of 35 g L–1 (corresponding osmotic pressure of 29.7 bar) and 50% water recovery (i.e., 50% of the feed stream becomes purified water and 50% becomes brine) requires at least 1.1 kWh per cubic meter of purified water. Regardless of the desalination technology, it is impossible to desalinate water using less energy than that determined by eq 12. 1.1 KWh per cubic meter is very much NOT a negligible amount, so the landauer analogy is incorrect.
- eru 3y ago
  Thanks for looking it up. Could you link to the sources? Thanks! I stand corrected in that case.