Energy-Source Matching And Optimization Analysis Of A Hybrid Solar-Geothermal Power Generation System

Solar energy is clean,safe,and abundant,while geothermal energy provides electricity with preferable stability and continuity.In recent years,hybrid power generation has been widely researched,among which the solar-geothermal hybrid power generation draws attention at home and abroad.In this study,the energy match and optimization of trough solar energy collection system and low grade geothermal ORC(Organic Rankine Cycle)power generation system is analyzed,in which the temperature of the geothermal fluid is125℃and the mass flow rate is 30 kg/s,and four hybrid power generation models,including preheat model,superheat model,preheat-evaporation model and evaporation-superheat model are established,and the net power output,thermal and exergy efficiency are studied with the climate condition in Lhasa on the summer and winter solstice hour by hour.The environment temperature,the temperature and mass flow rate of the geothermal fluid and the area of the solar collectors is optimized.The evaporating temperature of the net power output of the preheat model is optimized of hour by hour.Economic analyze of the LEC(Levelized Energy Costs)and annual profit of the four solar-geothermal hybrid power generation models and the standalone geothermal power generation model.The simulation results show that a solar-geothermal hybrid power plant,which offsets the negative influence on the thermodynamics property caused by the increase of the environment temperature during the daytime all day and the summer all over the year,contributes more net power output than a standalone geothermal power plant.When the environment temperature increase,the direct radiation is increases as well.Thus,solar energy and geothermal energy cooperate and complement each other.The order of the four models from the highest average net power output per day to the lowest one is shown as below:preheat model,evaporation-superheat model,preheat-evaporationmodel,superheatmodel.Inthepreheatmodel,evaporation-superheat model,solar energy not only provides extra heat source,but also improves the working ability of the geothermal energy.Under the optimal evaporating temperatures,the LEC of the hybrid power plant increases at first and then decreases,when the area of the solar energy collectors increases.As the area of the solar energy collectors is above 600 m~2,the LEC of the of the hybrid power plant is lower than the standalone geothermal power plant and provides more profit,and decreases as the area of the solar energy collectors increases.Solar-geothermal hybrid power plant is suitable in the districts where there exists drought sand abundant solar and geothermal energy resource and the environmental factors have less influence on power generation which has advantage on economics and the development of distributed energy because of more stable power supply and less influence on the electricity network and the users.