Direct Solar Reduction of CO₂ to Fuel:  First Prototype Results

Direct solar reduction of CO 2 to CO and oxygen has been demonstrated using only solar energy. Known thermochemical, kinetic, and spectral properties of the CO 2 /CO/O 2 system enable the process. In this first prototype system, a solar focusing mirror and secondary concentrator were used to provide high solar intensity around a ceramic rod. This high-temperature, high solar irradiance environment provided strong heating of CO 2 with the resultant dissociation to CO and oxygen. Quenching of the back reaction was provided by the geometry and gas dynamics of the system and by cool gas quencher jets just downstream. The best measured net conversion of CO 2 to CO was near 6%, which is compared to a plant design target of 12%. The peak observed conversion of solar energy to chemical energy was 5%. Calculations indicate that a mature system will yield 20% solar-to-chemical energy conversion with an additional 25% electrical energy.