Design Of Domestic Fuel Cell Combined Heat And Power System

Facing the current energy crisis,it is very important to study fuel cell technology,especially in the field of fuel cell cogeneration technology.This thesis starts from the proton exchange membrane fuel cell(PEMFC)model to study the influence of different parameters on the output performance of the stack.And then builds a PEMFC thermal management system with the stack as the core to study it.Secondly,a PEMFC combined heat and power system(PEMFC-CHP)is established on the basis of the thermal management system.The efficiency of the system is studied and analyzed.Finally,based on the PEMFC-CHP system,a CHP system combined with solar energy is established.And its heating performance is studied.The main research work and conclusions are as follows:1.The simulation model of PEMFC is established by MATLAB software,and the dynamic response characteristics of the stack are studied.The effects of current density,operating temperature,two-pole inlet pressure,and inlet relative humidity on the output performance of the PEMFC stack were analyzed.In the PEMFC thermal management system,three different controllers,common PID,Fuzzy-PID and RBF-PID,are used to control the stack inlet temperature,and the control effects are compared and analyzed.The results show that the output performance of the stack can be improved by increasing the working temperature,the two-pole intake air pressure and the inlet relative humidity,and the performance improvement of increasing the inlet relative humidity is more obvious,while the increase of the working temperature is relatively weak.In the range of 0～1.78A/cm~2,the output electric power of the system increases with the increase of the current density.When the current density is 1.78A/cm~2,the system output power reaches the maximum value of 6859.9W.Under the same conditions,the RBF-PID controller can obtain shorter rise time and regulating time,smaller overshoot,and more energy saving.So its control effect is the best,followed by Fuzzy-PID controller.2.Based on the PEMFC model,a PEMFC-CHP system model is built,and the effects of different cooling water flow rates and external loads on the electrical efficiency,thermal efficiency and cogeneration efficiency of the CHP system are analyzed.The change of temperature and water storage volume of the hot water storage tank were studied and analyzed.The results show that,within a certain range,the increase of cooling water flow has little effect on the electrical efficiency,but the thermal efficiency increases with the increase of cooling water flow.In the power load range,as the external load increases,the electrical efficiency of the PEMFC-CHP system increases,while the thermal efficiency decreases slightly,but the total cogeneration efficiency increases,and the maximum efficiency can reach 85%.When the simulated system runs for 24 hours and the preset water storage capacity is 120L,the total drainage is about 280L.When the preset water storage capacity increases by 10L,the drainage volume also increases by 10L,but the drainage time is about 1.5 hours later.The amount of water replenishment is only related to the temperature.3.Based on the established PEMFC-CHP system,a common flat-plate solar collector is added to build a solar PEMFC-CHP system.According to the characteristics of the system,two operating modes are designed:PEMFC mode and solar-PEMFC mode.The influence of solar radiation intensity on the temperature of the water tank and stack’s inlet are studied and analyzed.Taking Wuhan’s winter as the research object,the influence of the average solar radiation intensity of each month in winter on the water’s temperature of the tank is analyzed.And the hot water storage tank is used as the heating source of the floor heating system to study the indoor heating condition.The results show that when the system operates in solar-PEMFC mode,the stack’s inlet temperature will fluctuate due to solar radiation.But the error range of temperature’s fluctuation is within±1.5℃,and the system can operate normally.After solar energy was absorbed by the system,the water’s temperature of the tank can increase by about 12.5℃.When running the system in Wuhan’s winter,the temperature of the hot water storage tank can reach above 67℃.And when the tank is used as the heating source for floor heating,the heating temperature of a room with an area of 25m~2can reach above 22℃.The PEMFC-CHP system’s design and research on simulation in this thesis have certain reference value,which can provide theoretical guidance for the application of fuel cell CHP system.