Simulation And Performance Analysis Of Multi-source Cogeneration System Based On TRNSYS

The demand for energy is rising with the persistent growth of Chinese economy.The contradiction between the rapid increase of the energy consumption and environmental issues is increasingly prominent.Consequently,it has been an inevitable trend to develop alternative and renewable energy sources.This paper creates a multi-source cogeneration system based on solar photovoltaic solar-thermal collectors,ground source heat pump and fuel cell.This system can utilise renewable energy sources collectively,which in turn considerably increases consumption efficiency and meets users’ demand of thermal electricity at the same time.It is believed that this cogeneration system has great potential in energy saving and emission reduction.Based on an example house located in Tianjin rural area,this article calculates the dynamic load distribution of the building,designs a multi-source cogeneration system,and builds an instantaneous simulation system using TRNSYS software as the research platform.The main research contents are as follows:1.A systematic analysis of the mathematical model of solar photovoltaic solar thermal collectors is carried out,which summarises the factors affecting the efficiency of photovoltaic power generation and provides implications for improving the photoelectric conversion efficiency in the multi-source cogeneration system.2.An instantaneous simulation model of the building is created and the dynamic load distribution of the building is calculated simultaneously.3.The solar photovoltaic solar thermal collectors,underground heat exchangers,and heat pumps are systematically designed so two working modes are proposed accordingly.As a result,a complete and matching simulation system is established.4.The simulation results of the typical working days in the heating season and non-heating season are analysed and then compared with the PV / T collector without cooling cycle.Additionally,the simulated soil temperature after 40 years of system operation is calculated.Furthermore,the annual power generation of the fuel cell is calculated with the optimisation of the collector inclination.The main findings are as follows:1.Through the analysis of the mathematical model,it is concluded that the temperature of the back plate of the photovoltaic collector plate is the main reason behind the photoelectric conversion rate.The use of coolant water to cool down the photovoltaic panel is conducive to improve the photoelectric conversion efficiency.More importantly,the residual heat can be utilised to,in turn,improve the utilization rate of solar energy.The annual power generation of PV / T system with cooling cycle is 814 kW · h more than that of PV / T system without cooling cycle.Specifically,the former is 49.64% higher than the latter.When the PV / T system is insufficient to meet the user’s electricity demand,the fuel cell can be involved to produce more energy.The fuel cell power generation power is 5.167 kW and the annual power generation capacity is 45263 kW · h.2.The system is equipped with a hot water storage tank.Particularly,during the heating season,the solar collector is used to increase the inlet temperature of the evaporator.While the energy efficiency ratio of the system is increasing,the power generation rate of the PV / T system grows synchronously.In terms of the non-heating season,excess heat can be recharged underground.The maximum instantaneous heat replenishment is 24320.3103 kJ / h,the minimum is 886.7716 kJ / h and the total heat replenishment throughout the day is 180223.7451 kJ.3.The soil temperature has been simulated for an operation period of 40 years.The simulation results demonstrate that the average soil temperature is stable regardless of the length of operation period of the system.Notably,compared with the average soil temperature of 13.4 ℃ in the first year,the average soil temperature after40 years is 13.92 ℃,showing a slight increase of 0.52 ℃.Interestingly,the increase of the soil temperature is conducive to the operation of the ground source heat pump by improving the energy efficiency ratio.Besides,it is friendly to the ecological environment of the soil.