Research On Performance Simulation And Energy Management Strategy Of Distributed Combined Cooling,Heating And Power Generation System Based On SOFC/PV

The distributed combined cooling,heating and power generation(DCCHP)system is a total energy system,which is located in the enduser site and integrated the different equipment into a comprehensive system to provide simultaneously the user with the supply of cooling,heating and electricity based on the so-called principle of"temperature counterpart and energy cascade utilization".The DCCHP system can save significantly the primary energy costs and reduce pollutant emissions,which opens new option for solving the energy crisis and environmental pollutions currently encounterd in China and abroad.Therefore,the developed countries all around the world,such as European Commission,the United States of America,Japan,put a high priority to the research and development of the CCHP system.As a new energy supply device,the fuel cell has the advantages such as cleanness,high-efficiency,better performance under variable working conditions,exhaust of high temperature.The fuel cell is considered as one of the best energy systems to simultaneously provide the endusers with cooling,heating and power generation.As a green renewable energy resource,solar energy has been developed and applied to a wider of application areas,which has the advantages of abundant resources,cleanness,and non-pollution.The meteorological conditiontions have great influence on the solar energy,leading to unreliable and discontinuous in the solar energy applications.As a result,a new integrated generation device is developed based on the combination of solid oxide fuel cell(SOFC)and photovoltaic(PV)in this dissertation,which generates simultaneously the electricity and useful heating and cooling according to the principle of "temperature counterpart and energy cascade utilization" for different grades of heat energies.The high-temperature waste heat generated by SOFC is recovered for generation of both heating and cooling.The energy utilization performance of the entire cogeration system along with the stability,continuity and can be improved significantly.Therefore,the development and practical application of CCHP is of importance to relieve the energy crisis and reduce environment pollution in both theoretical study and engineering applications.At present,the research on the cogeneration system based on SOFC and PV is not yet mature in our country.And few research of CCHP system has been conducted in comparison with the developed countries,which is in leading postion in the reaserch area.Under the support of the National Natural Science Foundation of China,this dissertation is mainly focused on research on performance simulation and energy management strategy of distributed combined cooling,heating and power generation system based on SOFC/PV.A portion of energy produced by PV during operation of the system will be supplied to endusers.The other portion of the generated energy will be used to produce hydrogen through electrolyzer.The hydrogen will be used as fuel for SOFC.The high-temperature waste gas exiting SOFC will be reclaimed by a heat exchanger.The exhausted gas of middle and high temperatures is used to drive the lithium bromide refrigerator to generate the required cooling capacity.The main works and contributions achieved in this dissertation are summarized as follows.On the basis of thorough investigation on the references in the area,the scheme and design concept of the DCCHP system based on SOFC/PV is discussed.The system working principle,operating principles of the related components,and integrating principle of the system are theoretically investigated.The general structure scheme of CCHP system was established according to the relevant design idea,design principle,operating principle,and the specification.The mathematic models and complete Simulink dynamic models describing the corresponding modules of CCHP system are established,which mainly include SOFC,PV,maximum power tracking device of photovoltaic,steam-fired double-efficiency lithium bromide refrigerator,electrolyzer,hydrogen storage tank,air compressor,and power conversion instruments.The performances and characteristics of the system are simulated and analyzed.Several maximum power point tracking methods for CCHP system are studied comparatively based on the power characteristic of PV,which includes perturbation and observation,conductance increment method,fuzzy control,and BP Neural Network.The effectiveness,merit and demerit of the typical control algorithm are verified and analyzed.The proposed conductance increment method is considered applicable to the cogeneration system.The short-term load forecasting technology is investigated for the capacity matching and energy management of cogeneration system.Several intelligent short-term load forecasting methods are compared including BP Neural Network,RBF Neural Network,and wavelet Neural Network.The load forecasting model is established and the simulation analysis are done.The refrigeration equipment has an important impact on the overall performance of cogeneration system.The control strategy of cooling capacity was relatively complex and one of the most challenging technologies for cogeneration system.Therefore,the energy management methods have been studied deeply based on the analysis of double-effect lithium chiller characteristics.Finally,the energy management strategy and patterns are investigated to make sure that the cogeneration system can efficiently supply steady and continuous power,cooling,and heating.