Salinity Gradient Energy?

[Harold Squared]

Who knows what? Obviously taking salt out of water costs energy so it is possible to get energy from adding salts(ions) to this water. Or not. If not, why not, and is it worth commercial interest and development?

 

Looking forwards to various opinions facts figures from all sides.

[pavelcherepan]

Who knows what? Obviously taking salt out of water costs energy so it is possible to get energy from adding salts(ions) to this water. Or not. If not, why not, and is it worth commercial interest and development?

 

Looking forwards to various opinions facts figures from all sides.

 

Actually dissolution of crystallic salts is an endothermic process. You need to supply energy to break crystal structure as ions dissolved in liquid have higher entropy than in the form of crystal lattice. On the other hand crystallisation is an exothermic process and you can possibly get energy that way, although I haven't seen any such designs.

 

<Thermodynamic view on crystallisation>

 

EDIT: Come to think of it, difference in salinity changes water density and that's the leading cause for Gulf Stream, so it's possible to get energy from water flows due to difference in salinity, but I'm not sure if you'd get a net energy gain.

Edited April 6, 2015 by pavelcherepan

[Fuzzwood]

It is possible, in a way: allow fresh water to pass by saline water separated by a membrane that allows only water to pass through (and no ions), you can create a pressure differential strong enough to power a turbine.

 

http://en.wikipedia.org/wiki/Osmotic_power

Edited April 6, 2015 by Fuzzwood

[Harold Squared]

Thank you for your comments. Obviously harvesting such energy without disturbing the activities of anadromous and catadromous fish would be an additional hurdle.

 

Suppose brine from desalination operations were allowed to descend to the abyss due to its greater density? It would be too salty to support piscine life of any kind, and the fish at those depths are rare and do not venture to the surface, let alone inland. In the cold and dark waters remote operations might be feasible, after all interplanetary probes function at much greater distances.

Edited April 10, 2015 by Harold Squared