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Abstract

An apparatus and method for storing electrical energy as chemical energy and recovering electrical energy from stored chemical energy. A solid oxide electrolyte electrochemical cell is operated in two modes. The first, energy storage, mode comprises steps of: (A) supplying electrical energy and steam to a solid oxide electrolyte electrochemical cell operating between 600.degree. C. and 1200.degree. C. as an electrolysis cell, to produce H.sub.2 and O.sub.2 ; (B) passing the H.sub.2 gas so produced into an energy storage reactor containing iron oxide, to produce iron metal and steam; (C) recirculating the steam produced in the energy storage reactor to the cathode of the electrolysis cell; and (D) repeating steps (A) to (C) until the iron oxide is converted to iron metal, for chemical storage of electrical energy. The second, energy recovery, mode comprises steps of: (E) supplying steam to the energy storage reactor containing iron metal, to produce iron oxides and H.sub.2 gas; (F) passing this H.sub.2 gas to the fuel anode of an electrochemical cell operating as a fuel cell, and supplying O.sub.2 gas to the air cathode of the electrochemical cell, to produce electrical energy and steam at the fuel anode; (G) recirculating the steam so produced to the energy storage reactor bed; (H) repeating steps (E) to (G) until the iron metal is converted to iron oxide and H.sub.2 gas; and (I) recovering the electrical energy produced.

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