Thermodynamic Analysis And Optimization Of A Combined Heat Power And Hydrogen Production System Based On Solar Energy And PEMFC

As the energy demand,fossil energy consumption and pollution emissions continue to increase,looking for renewable energy alternatives to fuels and efficient and pollution-free energy utilization has become the current research focus.The multigeneration system combines solar and fuel cell realizes efficient conversion and utilization of energy,which can effectively alleviate energy shortages and environmental pollution problems.This study presents a combined heat power and hydrogen production system based on solar energy and proton exchange membrane fuel cell(PEMFC).It uses solar energy as the driving heat source,consists of dual-stage Rankine cycle,electrolysis hydrogen and fuel cell power generation technology to achieve renewable energy clean and efficient utilization.The mathematical model of the system is established,and the system parameters are analyzed for thermodynamics,economy and environment.Simultaneously,evolutionary algorithms is introduced to optimize the multi-generation system to obtain optimal operating parameters set for decision-making goals.The main research content of this article:Firstly,the thermodynamic analysis of the multi-generation system is carried out.As the fluctuation of solar radiation,the system operates in three different modes: SolarPEMFC mode,Solar-SOEC mode and PEMFC mode.The impacts of the operating parameters changes on the system efficiency is studied,and the distribution of exergy destruction is discussed.The results show that lower collection temperature,high solar radiation and current density can improve system efficiency.The energy efficiency in three modes is 42%,46% and 82%,respectively,and the maximum exergy destruction occurred on solar dish collector,accounting for 70% of the total system exergy destruction.Secondly,the multi-generation system is comprehensive evaluated.Using the levelized energy cost and greenhouse gas emission reduction as the system’s economic and environmental performance evaluation indicators,the main operating parameters on the comprehensive performance of the system is discussed.The results show that higher operating temperature can significantly reduce the system energy cost,but also greatly reduce the system’s greenhouse gas emission reduction;increasing the cathode and anode pressure will reduce the system energy cost,but increase the anode pressure will decrease the greenhouse gas emission reduction;the increase of SOEC water vapor mole fraction can improve the overall performance,while the increase of the current density can reduce the system performance.Finally,multi-objective optimization is adopted to improve the multi-generation system performance.The optimization objectives are system efficiency,levelized cost of energy and greenhouse gas emission reduction to optimize the system’s key operating parameters by the NSGA-II evolutionary algorithm.The optimization results show that the operating temperature is the most important decision-making variable of the system,and lower current density,high water vapor mole fraction,a suitable anode pressure and a high cathode pressure are more conducive to improving the system overall performance;the optimized levelized energy cost is reduced by 35% and the annual greenhouse gas emission reduction is increased by 20%.