Research On Thermal Performance Evaluation And Design Optimization Of Solar Aided Coal-fired Power Generation System

Solar aided coal-fired power generation(SAPG)system is an integration system in which renewable energy and fossil energy complementarily generate power.A SAPG plant uses solar heat to replace a part or all of the extracted steam i n one or more preheating stages and save coal consumption.On the one hand,SAPG system can realize development and utilization of solar energy inexpensively and large-scale popularization of solar thermal power generation,on the other hand,SAPG system can reduce the pollution and imporve the performance of coal-fired power generation.Being a new composite power system,SAPG system is a new approach to solve the environment pollution and finite reserves of fossil energy.As part of corresponding national key scientific research programs,research in this thesis is carried on the coupling mechanism,energy consumpton apportionment and design effective Direct Normal Irradiation(DNI)distribution of SAPG system,which takes into consideration the characteristic of multiple-input-single-output and the energy quality difference of different energy in SAPG system.(1)Coupling mechanism resrarch of SAPG system.There is not the uniform coupling principle for SAPG system because of the system complexity.The energy conversion model of SAPG system is built in this study.The expression on the instantaneous solar-to-electricity efficiency of SAPG system is obtained.The performance with influence factors variation is studied.The theoretical basis for designing the SAPG system is provided.It is important to take into consideration various factors such as the unit capacity,quality of replaced extraction steam,DNI and solar aperture area to obtain the optimal perforance for SAPG system.(2)Research on energy consumption of SAPG system.A theoretical framework for the energy consumption analysis of the SAPG plant using specific consumption theory is proposed to evaluate the energy consumption of each individual component and that of the overall system.Energy consumption models for SAPG system are built based on the specific consumption theory.The specific consumption distribution characteristic of SAPG system under different operational conditions is studied and the main factors to influence the specific consumption characteristic of SAPG system are obtained.The results indicate that,the fuel-specific consumption decreases as solar energy is introduced into the coal-fired power plant.Besides,the key factor to influence the energy consumption is DNI and solar aperture area.Energy consumption distribution character and change regularity influenced by external factors in SAPG system are revealed in this study.Theoretical basis to improve thermal performance and reduce the specific costs of the SAPG is proposed based on the results of this study.(3)Research on the energy consumption cost apportionment of SAPG system.The energy consumption cost apportionment models of SAPG system are built based on the solar contribution evaluatuon method and energy consumption models of SAPG system.The solar energy consumption cost apportionment characteristic of SAPG system is studied which reveals the variation regularity of energy consumption cost apportionment casued by the variation of input energy.The energy consumption cost allocation characteristic is revealed in this study.The guidance to choose the integration scheme and operation for SAPG system is put forward.Besides,the superiority of SAPG system is certified from the view of thermal and economical performance.Meanwile,the theory basis for formulating relevant policy of SAPG system are provided based the results of the research.(4)Research on design effective DNI distribution of SAPG system.The annual performance is comparative analyzed with the annual solar-to-electricity efficiency and Leveled Energy Cost(LEC)to be the annual performance index.The optimal design effective DNI and the optimal design effective DNI distribution corresponding to the optimal annual performance is obtained.Besides,the annual and monthly performance is comparative analyzed with different design effective DNI selection methods.The optimal desin DNI distribution regularity of SAPG system is revealed in this study.The theoretical basis for large-scale development and construction to optimization design the SAPG system is provided based on the results of this research.