Thermodynamic Analysis of a Solar-Coal Hybrid Poly-Generation Process for Methanol Synthesis and Power Generation

To advance the utilization of the solar energy and coal resources as well as improve the flexibility of coal-based power plant, an improved solar-coal hybrid system for methanol production and power generation is proposed and thermodynamically analyzed. In the proposed system, the concentrated solar energy at high-temperature is used for heating the coal gasification to produce syngas for methanol synthesis; the waste material and heat from coal-to-methanol process are efficiently recovered in the conjunct power generation system; and the surplus electric power is optionally used for methanol synthesis by electrolysis process during the off-peak period. Through employing the proposed system, the solar energy and electricity (optional) could be effectively converted into methanol as stable chemical energy together with a preferable overall system thermal efficiency. The thermodynamic analysis results showed that, the overall energy and exergy efficiencies reaches 48.6 and 47.3%, respectively; the equivalent solar-to-methanol conversion efficiency can soar to 66.2%; and the net electricity-to-methanol efficiency reaches 61.6% with the power load reducing from 48.7% to 31.0%.