Novel process for direct conversion of free energy of mixing into electric power

Direct conversion of salinity gradients into electric power as well as production of an acid and a base, simultaneous to generation of electricity, was investigated. Devices that combined features of an electrodialytic pile with those of fuel cells or of electrochemical half cells were designed. Electrodes of the electrochemical half cells were restored to their initial condition by simple reversal of the flow pattern. Fuel cells in the investigated system used water as the fuel and air as the oxidant. Energy extracted from salinity gradients at power density of up to 1 W/m/sup 2/ of the membrane yields up to 0.6 MW of electric power per m/sup 3//s of river or brackish water. Sodium hydroxide is obtained in an amount which corresponds to the number of coulombs of electricity generated in the process. Part of the produced HCI is, however, lost.