Simulation Research On Domestic CCHP System Based On SOFC

With the increasing global energy issue,the utilization of renewable energy has drawn great attention and gradually become the main technique applied in the engineering field.Hydrogen fuel cell is a green and efficient technique.When it is combined with CCHP(combined cooling,heating and power)system,which is a typical energy cascade utilization,the overall energy consumption in buildings can be effectively alleviated.This study presents a micro hydrogen SOFC(Solid Oxide Fuel Cell)-CCHP system designed for residential buildings.By analyzing the system performance and optimization,this study aims to provide theoretical basis and reference for the further development of SOFC-CCHP system in the field of new energy based buildings.The SOFC-CCHP system is developed by using MATLAB/Simulink.For the main components,the accuracy of the SOFC stack and two-stage Li Br absorption chiller are validated with reference data.The SOFC-CCHP system is derived based on the validated models and used in the following analysis.The heating and cooling demands are derived from typical residential buildings in summer and winter conditions.The system performances under such conditions are analyzed by considering two operation principles and are evaluated by comparing the primary energy efficiency ratio.In order to realize optimization of the SOFC-CCHP system,the impact of stack current to the system performance is also discussed in detail.Considering the load demands in residential buildings,the SOFC stack by using hydrogen is designed for 2kW.The simulated adsorption chiller matched reference values within ±1% and the COP is 1.392.“Determining heat by power” and “determining power by heat” are two operation strategies that used in CCHP system.The way of “determining heat by power” is better than the other when running the simulation.In such operation strategy,it is give priority to meet cooling and electric demands,and the excess heat generated by the system is used for cascade utilization.Results indicate that for the summer season,the energy saving rates of heat recovery in high and medium temperature regions are 9-28% and 3-42%,respectively.The heat recovery in low temperature region can increase domestic water temperature up to 66.83°C.For the winter season,the energy saving rate of heat recovery in high temperature region is 6-24%,and the heat recovery in low and medium temperature region can increase domestic water temperature up to 49.99°C.Based on the further thermodynamic evaluation of the SOFC-CCHP system proposed in this study,it is found that the primary energy efficiency ratio is 76.0%-90.8% in summer and 73.4%-94.5% in winter.The system performance can be optimized by adjusting the stack current.When the current is around 30 A,the primary energy efficiency reaches highest value of 95.4%.Finally,The high performance and low performance modes are adopted to run the system...