Integration Analysis And Optimization On A PEMFC-based Micro-CCHP System Integrated With Geothermal-assisted Methanol Reforming

The excessive consumption of fossil fuels and the environmental problems they bring are increasingly prominent,and human survival is facing great tests.Changing the mode of energy utilization,improving energy efficiency,and developing renewable energy are important ways to solve energy and environmental problems.Aiming at the problems of large fuel consumption,high cost,and low energy utilization rate of conventional fuel cell-based CCHP systems,this paper proposes a PEMFC-based micro-CCHP system integrated with geothermal-assisted methanol reforming.The geothermal energy is the heat source of the CCHP system,and the hydrogen produced is used as the direct fuel of the fuel cell system.The electrochemical reaction of fuel cell generates electricity,and the heat generated is recovered as waste heat for cooling and domestic hot water.The comprehensive evaluation method was used to evaluate the system,and the thermodynamic,economic,and environmental performance of the PEMFC-based micro-CCHP system integrated with geothermal-assisted methanol reforming was explained.The evolutionary algorithm is introduced as an optimization tool,which optimizes all aspects of the system index,and provides a new method for the optimization research of the CCHP system.The main research contents of this paper:First,the thermodynamic study of a PEMFC-based micro-CCHP system integrated with geothermal-assisted methanol reforming.With the help of parameter analysis methods,the effects of main operating parameters（geothermal temperature,ratio of water to methanol）on the thermodynamic performance（electric power,efficiency,primary energy saving rate,etc.）of the CCHP system were discussed.The results show that the total electric power,thermal power and cooling capacity of the system increase with the increase of geothermal temperature.As the ratio of water to methanol increases,the heating power and cooling capacity increase.In contrast,due to the reduction in the gas turbine power,the overall electrical power decreases.CCHP system efficiency increases with increasing geothermal temperature and ratio of water to methanol,and tends to saturate when ratio of water to methanol exceeds1.0.In addition,the output power fluctuates with a change inτ.Whenτis 1.0,the system can reach the maximum output power.Secondly,the economics and environmental performance of a PEMFC-based micro-CCHP system integrated with geothermal-assisted methanol reforming are studied.Economic indicators（average annual cost and levelized cost of energy）were used to assess the economic potential of the system,and environmental indicators（direct carbon dioxide footprint emissions）were used to evaluate the system’s environmental performance.The results show that the geothermal temperature,ratio of water to methanol and some economic parameters have a great impact on the economic and environmental characteristics of the system.Direct CO₂ footprint emissions decrease with increasing geothermal temperature and ratio of water to methanol,and the minimum emissions can be reduced to 0.493kg/k W.The increase in hydrogen price and service life has also increased the average annual cost savings rate.In addition,as the price of methanol,geothermal temperature,and ratio of water to methanol increase,the average annual cost savings rate decreases.Compared with the reference CCHP system,the proposed system has obvious economic advantages.Finally,the PEMFC-based micro-CCHP system integrated with geothermal-assisted methanol reforming was evaluated from three aspects:thermodynamic performance,economic cost,and environmental impact.The total power,levelized cost of energy,and direct CO₂ footprint were used to reduce emissions.The quantity is the optimization target,and the two evolutionary algorithms of NSGA-II and fgoalattain are used to optimize the system.The conclusions are:although low geothermal temperature will increase the total power,it will increase the levelized cost of energy and direct CO₂ footprint reduction;increasing the ratio of water to methanol is not conducive to the reduction of total electric power and direct CO₂footprint reduction,but it reduces the levelized cost of energy.The CCHP system has better performance after optimization.