Thermodynamic performance of a mid-temperature solar fuel system for cooling, heating and power generation

Abstract

Solar thermal fuel is a promising approach of solar energy utilization, in which concentrating solar energy can drive the hydrocarbon fuel decomposition or steam reforming to produce hydrogen or syngas for generating power through heat engine. In the present, most of solar thermal fuel processes have employed solar heat at above 800°C which needs higher-concentration-ratio solar cavity reactor with higher re-radiation loss, bringing about poor annually average efficiency of solar-fuel-power. Here, a mid-temperature solar thermal fuel system by using chemical looping combustion (CLC) is studied for producing cooling, heating and power. The concentrated solar heat at approximately 350°C is utilized to drive the dimethyl ether fueled-chemical looping combustion with pair of CoO/Co as oxygen carrier. By using the mid-temperature solar heat driving CLC, the low-grade solar heat is upgraded into high-grade chemical energy of metal Co as solar fuel that is further converted into high-temperature thermal energy at 900°C via oxidation of Co and drives a recuperated gas turbine for generating power. The waste heat from the gas turbine can be utilized to produce a double-effect water/lithium bromide absorption chiller for producing the cooling and the heating. The thermodynamic performance of this mid-temperature solar fuel system is analyzed and the effects of several operation parameters such as solar irradiation, production of the solar fuel and pressure ratio are examined. The annually average efficiency of solar-fuel-power can be about 21%, with approximately 5 percentage points higher than that of solar thermal power system. In addition, the reason of the improvement in the performance is revealed by the irreversibility methodology. Our results would be expected to bring a new pathway for the application of solar thermal fuel in the distributed CCHP technology.