Numerical Simulation And Performance Analysis Of Hybrid Solar-geothermal Power Generation System

Solar energy is widely distributed and easy to obtain,but due to climatic conditions,solar power generation is discontinuous and unstable.The geothermal resources are abundant in reserves and the power generation has a good stability.However,the geothermal resources in China are mainly medium and low temperature,and the power generation efficiency is low.In the view of their respective limitations,multi-energy complementary hybrid power generation technology has been widely concerned.This paper focuses on the multi-energy complementary ideas to construct a model of solar and geothermal hybrid organic Rankine power generation system.The effects of environmental temperature,working fluid evaporating temperature,geothermal fluid inlet temperature,geothermal fluid inlet mass flow rate and solar collector area on system performance are analyzed.Based on the first and second laws of thermodynamics,the thermal efficiency of the hybrid power generation system and the energy loss of each component(evaporator,condenser,solar collector,etc.)are analyzed,which provides a reference for the optimization of the system.Based on the proposed power-increasing and geothermal energy-saving power generation schemes,the advantages of the hybrid power generation system in terms of power output and geothermal energy savings compared to the stand-alone geothermal power generation system are analyzed.According to the characteristics of China’s regions and resources,this paper selects the four regions of Lhasa,Tianjin,Guangzhou and Xi’an to conduct time-by-time simulation calculations to analyze the effects of solar radiation intensity,geothermal reservoir temperature and environmental temperature on the performance of hybrid power generation systems.The introduction of the LEC(Levelized Energy Costs),investment payback period,net present value and internal rate of return as evaluation indicators,economic analysis and evaluation of independent geothermal and hybrid power generation systems,comparing the economics of the two power generation systems.The following conclusions are drawn:After the geothermal power station is coupled with solar energy,with the increase of solar collector area,the power generation and thermal efficiency increase gradually,and the efficiency of the exergy efficiency decreases.The change in the proportion of solar collector exergy losses to total exergy losses is the largest,accounting for 22.15% of the summer solstice and 5.22% of the winter solstice.When the power-increasing hybrid power generation scheme is adopted,the percentage increase in power generation from high to small is Lhasa,Xi’an,Guangzhou,and Tianjin.When using the geothermal energy-saving scheme,the percentage of geothermal water savings varies according to the characteristics of different regions.The economics of a power station is mainly affected by three factors: the initial investment of the power station,the operation management fee and power station sales revenue.The sales revenue of power stations has the greatest impact on the economics of stand-alone geothermal power plants and hybrid power plants.Compared with a stand-alone geothermal power station,the hybrid power station has a higher LEC and a longer payback period,but the net present value of the hybrid power station is slightly higher than that of a stand-alone geothermal power station.This shows that the long-term operation of the hybrid power plant will have higher profits than the stand-alone geothermal power station.