Reverse electrodialysis

From Open Energy Information


Reverse Electro Dialysis (RED) is a non-polluting technology to generate energy from the mixing of fresh and salt water.Advantages are: endless availability of fuel and no SO2, CO2 and NOx exhaust.


In RED, a concentrated salt solution and fresh water phase are brought into contact through an alternating series of anion exchange membranes (AEM) and cation exchange membranes (CEM). Due to concentration difference between both solutions, anions migrate through the AEM towards the anode and cation move through the CEM towards the cathode, thus generating a potential difference. Electricity is generated from the oxidation of Fe2+ and reduction of Fe3+ at the anode and cathode, respectively. The membranes necessary for RED are simpler, less robust, and therefore possible cheaper then for normal electrodialysis. Moreover, process conditions differ from electrodialysis and therefore tailor-made membranes are necessary.