Research On The Performance Of A New Type Of Solar Energy And Geothermal Energy Combined Cooling, Electricity And Fresh Water Supply Syste

With the growth of population and the improvement of people’s living standards,people’s demand for electricity,refrigeration and fresh water is increasing,especially in some island countries,the demand for electricity,refrigeration and fresh water is greater.Therefore,on the basis of previous studies and based on organic Rankine cycle,jet refrigeration cycle and multi-effect seawater desalination system,this paper designs a new type of solar energy and geothermal energy combined drive cold,electricity and fresh water supply system.In the alleviation of energy shortage and environmental pollution problems,but also to meet people’s needs for electricity,refrigeration,fresh water.MATLABR2020b and REFPROP9.0 are used to model the proposed solar energy and geothermal energy combined cooling,electricity and fresh water supply system,including the establishment of thermodynamic model and system evaluation index model.11 input parameters are selected to analyze the sensitivity of key output parameters and evaluation index of the system.The influence of 11 input parameters on the system performance is studied.The working condition optimization and the optimization of circulating working medium are carried out by using genetic algorithm based on different objective functions.Taking refrigerant R601a as the circulating working medium of system,exergy energy utilization coefficient of system is 18.80%,exergy efficiency is 30.27%,net work of system is327.46k W,cooling capacity is 92.03k W,fresh water production cost is 0.58$/m3,and total unit product cost of system is 51.49$/MWh.The system unit product environment impact is769.97mpts/MWh.Exergy analysis shows that a turbine,low pressure reheater,low pressure steam generator and condensate heat exchanger are the main components responsible for Exergy loss.Exergy efficiency and improvement potential show that a low pressure reheater has the greatest improvement potential,followed by a turbine.Through sensitivity analysis,it is found that 11 input parameters of the system have certain influence on the evaluation index of the system,and the influence of 11 input parameters on the system performance is explored,which provides theoretical guidance for the later production practice.The MATLAB genetic algorithm toolbox was used to optimize the system.Taking the minimum fresh water production cost,the minimum unit product total cost,the minimum unit product environmental impact,the maximum exergic efficiency of the system and the maximum energy utilization coefficient as the objective functions,the minimum fresh water production cost of the system was 0.3025$/m~3 under set constraints.The minimum total cost per unit product of the system was$25.22/MWh,the SUBP of the minimum unit product environmental impact was636.25mpts/MWh,the maximum energy utilization coefficient of the system was 45.72%,and the maximum exergic efficiency of the system was 39.39%.Under the basic parameter setting of the above optimal working conditions,the influences of different circulating working medium on different evaluation indexes were studied.The results show that:with the minimum fresh water production cost as the objective function,the working medium R365mfc is the best working medium.The minimum unit product cost of the system was taken as the objective function,and the working medium hexane was the optimal working medium.The maximum exergic efficiency of the system is the objective function,and working medium R141b is the optimal working medium.A comparative analysis of the performance of the system put forward in this paper and the power-cooling combined supply system of the uncoupled multi-effect seawater desalination system found that various performances of the system had improved greatly,as the energy utilization coefficient of exergy rose by up to 18.97 percentage points,while the exergic efficiency rose by up to 7.14 percentage points.At the same time,for the five optimal working conditions above,exergic exergy can be put into operation in an area with a large demand for cold capacity as the target function of minimum fresh water production cost,while for an area with a large demand for power,exergy can be put into operation in an optimal working condition with maximum exergy efficiency or minimum total cost per unit product of the system as the target function.However,if exergic exergy efficiency of the system was put into production in a working condition of minimum environmental impact per unit product of the system and maximum exergic efficiency of the system as the target function,the fresh water production of the system was relatively small,while cooling capacity and electricity generation were relatively small.Considering people’s demands for work,cooling capacity and fresh water,as well as the higher unit product cost of the system,these two optimal working conditions are not recommended for actual production.