TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred System: The thermal source is a solar concentrator that focuses sunlight on a receiver to produce a temperature high enough to decompose SO3 into SO2, where at least one of the first reactor and the second reactor comprises a catalyst for converting SO3 into SO2 and O2 or SO2 and O2 to produce SO3. The first reactor converts SO3 into SO2 and O2 at a temperature of 600-1200 degrees C. The second reactor converts SO2 and O2 to produce SO3 at a temperature of less than 800 degrees C. The system further comprises an oxygen storage material that traps and stores a portion of O2 produced by the first reactor converting SO3 into SO2 and O2, where at least one of the oxygen storage material the temperature of oxygen storage material are chosen to adsorb and release O2 at an O2 partial pressure of 0.01-3 bar. The pressure is maintained at 1-100 (preferably 5-15) bar. The system further comprises: a first electrochemical cell is located downstream of the first reactor and is exposed on one side to a process stream and on the other side to the ambient air, the first electrochemical cell removes O2 formed by the first reactor from the process stream and pumps it into the ambient air; and a second electrochemical cell is located upstream of the second reactor and is exposed on one side to the process stream and on the other side to the ambient air, the second electrochemical cell pumps O2 from the ambient air into the process stream to be used by the second reactor. The system additionally comprises a first electrochemical cell is located downstream of the process that converts SO3 into SO2 and O2 and is exposed on one side of this electrochemical cell to the process stream and on the other side of this electrochemical cell to a vessel containing an oxygen storage material, and a second electrochemical cell is located upstream of the process that converts SO2 and O2 to produce SO3 and is exposed on one side the this electrochemical cell to the process stream and on the other side of this electrochemical cell to a vessel containing an oxygen storage material where: the first electrochemical cell removes O2 formed in the conversion of SO3 into SO2 and O2 from the process stream and pumps it into the vessel containing the oxygen storage material, the second electrochemical cell pumps O2 from the vessel containing the oxygen storage material into the process stream to be used in the conversion of SO2 and O2 to produce SO3. The first reactor includes an electrochemical cell that removes oxygen from the first reactor to allow a higher conversion of SO3 to SO2. The second reactor includes an electrochemical cell that produces electrical power from the conversion Of SO2 and O2 to produce SO3. Preferred Method: In the method, at least a portion of O2 produced in the first reactor by the decomposition of SO3 into SO2 and O2 is trapped on an oxygen storage material. The method further involves: a first electrochemical cell that pumps O2 produced in the first reactor by the decomposition of SO3 into SO2 and O2 to one of ambient air and a vessel containing an oxygen storage material; a second electrochemical cell that pumps O2 from one of ambient air and a vessel containing an oxygen storage material to react with SO2 in the second reactor to produce SO3.