Research On Solar Heat And Power Cogeneration System Based On Phase-Change Cooling

Solar heat and power cogeneration system is the combination of photovoltaic power system and solar collector.The photovoltaic power system converts solar energy into electric energy and generates electric income directly while solar collector takes away residual heat from the backplane of photovoltaic panel and generates thermal income.With the continuous deepening research on solar heat and power cogeneration system by scholars at home and abroad,various optimization schemes for this system have been put forward in order to improve the operation performance of the system.Also,the phase change materials have high application prospects in energy storage,residual heat utilization and thermal management due to the high thermal storage density and wide temperature range.The purpose of this subject is to further improve the operation performance of solar heat and power cogeneration system by utilizing the advantages of phase change materials,and to study the influence of phasechange materials on the electrical and thermal efficiency of the system through experiment and simulation.So the optimal operation scheme of solar cogeneration system based on phase change cooling under typical daily meteorological conditions is proposed.Firstly,the types,phase change temperature,encapsulation method and arrangement of phase change materials in solar heat and power cogeneration system based on phase-change cooling are determined through literature research.The thermal properties of the prepared pure paraffin and the composite phase change materials with different mass fractions of expanded graphite are tested respectively.Secondly,the design and construction of the experiment equipment are completed,and the experimental research on solar heat and power cogeneration system based on phase-change cooling is carried out to study the effect of phase-change cooling and flow rate on the operation performance of the system under the meteorological conditions of typical winter days in Shanghai Lin-Gang Special Area.The results show that the application of phase change materials can effectively improve the average electrical efficiency and maximum thermal efficiency of the system to 16.8% and 59.8% respectively.Then,according to the theory of heat transfer etc.,the physical model and mathematical model on solving efficiency of the solar heat and power cogeneration system are established,and the numerical simulation of the project is completed by using the self-made program.The model is validated based on themeasured meteorological data of typical days,and the results show that the simulation results are in good agreement with the experimental results.Based on the model on solving efficiency,the influence of thickness,types and arrangement of phase change materials on the operation performance is studied,and the corresponding optimal operation scheme of the system under typical winter days in Shanghai Lin-Gang Special Area is simulated.The simulation results show that the system has good performance when the phase change material is 1cm thick and arranged between the backplane of photovoltaic panel and the heat exchange pipe.For the composite materials with 5%,10% and 15% expanded graphite,the operation performance of the system is improved with the increase of mass fraction of expanded graphite.Furthermore,the operation of the system under typical summer days in Shanghai Lin-Gang Special Area is simulated and studied.The simulation results indicate that the phase change temperature of phase change materials should be close to the maximum temperature of photovoltaic panels during operation,thus an optimal operation scheme of solar heat and power cogeneration system in summer can be obtained.Through the research on this subject,the optimal operation scheme of solar heat and power cogeneration system based on phase-change cooling under typical days can be obtained,which provides guidance for the engineering application of phase change materials in solar heat and power cogeneration system.