Research On Hybrid Solar-geothermal Power Generation System Based On Organic Rankine Cycle

Solar energy and geothermal energy are currently being widely used as renewable energy,solar and geothermal is likely to be the main alternative energy to fossil fuels.Solar energy is a kind of clean energy with huge reserves,but it has some disadvantages.Geothermal energy is a stable renewable energy,but its high-temperature reserves are small.Therefore,this paper designs a hybrid solar-geothermal power generation system based on the idea of multi-energy complementary,and studies the built hybrid solar-geothermal power generation system.This paper conducted the following research:After analyze the solar collector,it comes to a conclusion that parabolic trough type solar collector is widely used at present,the article selected ET150 solar collector,and built a mathematical model based on its parameters to calculate the temperature of solar collector heat conduction oil.After obtain the distribution of solar energy in our country and the information such as the radiation intensity in the solar year,heat conduction oil temperature calculation system on the basis of the mathematical model is programmed using Matlab.This paper summarizes four kinds of common geothermal power generation systems by reading literature and analyzing the thermodynamic properties of the systems,and designs a hybrid solar-geothermal power generation system using geothermal energy as the main energy and solar energy as the auxiliary energy.Hybrid solar-geothermal power generation system consists of solar preheating cycle,upper organic Rankine cycle and lower organic Rankine cycle.Based on the simulated temperature,isopentane and butane were selected as the working media of the upper and lower organic Rankine cycles.Based on the thermal process and mathematical model of the hybrid solar-geothermal power generation system,the thermodynamic characteristics of the hybrid generation system were calculated,and exergy distribution and exergy loss distribution of the system were obtained through analysis.The net work output of hybrid solar-geothermal power generation system under design conditions is 13.33 MW·h,the thermal efficiency and exergy efficiency of hybrid solar-geothermal power generation system are 15.17% and 23.16% respectively;exergy loss distribution shows that exergy loss of solar collectors is the largest,accounting for 47%,followed by exergy loss of solar preheating heat exchanger,accounting for 12%,that is,exergy loss of solar preheating cycle accounts for nearly 60%.To analyze the effects of various parameters on system thermodynamic performance,the article selected pinch point temperature difference,working medium evaporation pressure,degree of superheat and the heat source temperature to do sensitivity analysis.The results show that heat source temperature and evaporating pressure had significant effect on the thermodynamic properties to the system,and the pinch point temperature difference and degree of superheat has little effect on the system thermal efficiency and exergy efficiency results.Since the hybrid solar-geothermal power generation system can be applied to regional power supply,and the users have the demand for heating,if using electric energy for heating,the utilization efficiency of energy is low,so this paper designs parallel heating hybrid solar-geothermal power generation system.Through modeling and calculation of the system,it can be obtained that the output water temperature is 94.2℃.On this basis,three system optimization schemes are proposed,and the output water temperature is 96.7℃,90.6℃ and109.6℃ respectively.Exergy efficiency of the above four schemes is 28.35%,25.18%,23.08% and 27.31%respectively.Exergy efficiency of the schemes increased to some extent except scheme 3.