Research On Distributed System Integrated With Solid Oxide Electrolysis Cells

In view of the rapid growth of energy demand and the increasingly prominent problem of global warming,renewable alternative energy and advanced power systems are being researched all over the world under the background of sustainable development.Solar energy is an important way to solve human energy problems.However,its utilization has the shortcomings such as volatility and unpredictable.It is necessary to find reliable energy carrier to solve the problem of intermittent storage.Because of its high energy density and environmental friendliness,hydrogen has become one of the most promising solar fuel.Hydrogen production from water electrolysis driven by solar energy is an ideal way to convert solar energy into hydrogen energy for storage.Among various types of electrolytic cells,solid oxide electrolysis cell(SOEC)has advantages over low temperature proton exchange membrane electrolyzer and alkaline electrolyzer due to its low power consumption and high energy conversion efficiency.However,the application of SOEC has not yet been commercialized and is still in the research and development stage,so more researchers and scholars are needed to conduct in-depth research to improve its performance.In this paper,based on the idea of coupling solar energy and SOEC to produce hydrogen,the SOEC hydrogen production system driven by photovoltaic and trough photothermal synergy and the tower solar thermal power generation-SOEC hydrogen production system are integrated and designed.In the SOEC hydrogen production system driven by photovoltaic and parabolic trough photothermal technologies,a white box model of SOEC based on physical equations is established and its parameters analysis is performed.The electrical energy needed for the electrolysis process is provided by photovoltaic devices,and the trough solar collectors are used for evaporating and superheating feed water.The meteorological parameters of summer solstice in Beijing are selected as disturbances,and the fluctuation characteristics of trough collectors and photovoltaic cells with solar direct normal irradiance(DNI)and their effects on hydrogen production and oxygen production are analyzed.Finally,the energy and exergy analysises of the overall system are carried out.The results show that the maximum energy and efficiencies of the coupled solar energy system are 19.1%and 20.3%,respectively.The maximum exergy loss of the system occurs in the photoelectric conversion process,and the exergy loss ratio is as high as 87%.In the tower solar thermal power generation system integrated with SOEC,through the use of area specific resistance(ASR)parameters based on experimental data,the calculation of polarization loss is integrated,and a simplified SOEC grey box model is established.The sensitivity analysis of this model shows that the input power of the electrolyzer has great influence on its operating temperature and mode,and the total energy efficiency of the system is inversely related to the cell power and hydrogen production.By considering waste heat utilization and changing the extraction steam position,the integration process of SOEC and solar power plant is optimized,and the highest energy efficiency of the system is 25%.Finally,according to different solar multiples,heat storage capacity and hydrogen storage capacity,the annual performance of the system is analyzed.When the solar multiple is 1,the heat storage capacity is 15 h,and the hydrogen storage capacity is 5 h,the maximum annual operating efficiency of the system is 25.9%.