Abstract: In a rechargeable storage cell, the photoredox reaction and regenerating reaction of a photoredox couple in one half-cell provide the driving force for producing charged state redox couples in both first and second half-cells separated by an ion selective permeable membrane. In the primary embodiment, a thionine dye photoreacts with ferrous ions in the first dye containing half-cell to oxidize those ions. The reduced form of the dye then reacts via a selective electrode in the first half-cell connected to an electrode in the second half-cell to reduce ferric ions in the second, dye-free half-cell. When the second half-cell electrode is then connected to a first half-cell electrode which is reversible to the iron ions, the concentration cell formed by the above reactions can be discharged through a load by the redox reaction of the iron ions.