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No. 29432
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1,5 MB, 20 pages
5,7 MB, 19 pages
Reversed electrodialysis (RED) is a method of extracting electrical power out of salinity gradient energy between seawater and freshwater. It functions similar to any other electrochemical method, effectively it is a fuel cell that uses ions from seasalt as fuel. Ions are exchanged through selective membranes, so that cations and anions flow in opposite directions, effectively creating an electrical current that is balanced by opposite-equal flow of electrons through the electrical circuit it feeds.
How much energy is available for harvesting this way?
>In the Netherlands, for example, more than 3,300 m³ fresh water runs into the sea per second on average. The membrane halves the pressure differences which results in a water column of approximately 135 meters. The energy potential is therefore e=mgΔh=3.3*106 kg/s*10 m/s2*135 meters ca.= 4.5*109 Joule per second, Power=4.5 gigawatts.
What's Ernst's opinion on this readily available source of energy?
No. 29437
I had a "young physician" kit, where it was proposed to conduct this experiment.
It must be calculated how much metal you need for economically viable energy output.
No. 29438
Seems like you need a small house full of machinery to produce the same power as a car battery.
No. 29445
Yes, it's not a technology that works on small scale... but it might be a viable alternative industrial energy source if you have a river you can utilise.
No. 30002
So if you were able to redirect every drop of water that reaches the shores in the netherlands all you get is about 1 nuclear powerplant?
No. 30006
I have serious doubt in the practicality on a greater scale. How are the Nerherlands supposed to put a membrane between the land and the sea? Maybe they could put a membrane over one or some arms of the Rhine delta, but that would cover just a percentage of the supposedely 3,300 m³ fresh water/4.5 gigawatt potential. Also I see a problem with keeping that membrane free from debris and penetration by same debris.

As practical applications ocean power plants that generate energy from waves and tidal
power plants that generate power from tidal streams seem to make more sense.

Given that higher salinity provides higer energy densities, preprocessing the seawater using solar desalination should provide a higher energy generation per square meter of membrane,
so for the time being my conclusion is Reversed electrodialysis (RED) might rather have a potential for countries that already generate drinking water from desalination, and therefore already produce huge amounts of brine as a waste product of the desalination process
(Arabs, Australia, Israel, Singapore etc.).