Research On Coupling Mechanism And Thermal Character Of The Solar Supported Coal-Fired Electric Generation System

Energy conservation & consumption reduction is one of the long-time basic national policies in China.As the annual coal consumption in coal-fired plants accounts for much of the whole coal consumption in the country,energy conservation & consumption reduction in them plays a significant role.Solar supported coal-fired electric generation(SSCEG) system,which is based on the design framework of a conventional coal-fired generation unit,integrates a solar thermal utilization system into the coal-fired generation system.It opens a way for energy conservation technically in coal-fired power plants and for large-scale utilization of solar energy. Supported by some scientific tasks including the National Natural Science Foundation of China named as "Research on Coupling Mechanisms & Thermal Characters of the Integrated Thermal Electric Generation System Combined by Solar Energy and Fossil Fuel" and others,the SSCEG system has been put forward originally in this dissertation.And the work carried out in this dissertation all takes this SSCEG system as the core.The main work is as follows:Firstly,parabolic trough solar collectors are used to collect solar energy in a SSCEG system.The factors affecting the thermal efficiency of a DSG collector was discussed and analyzed.And the stable thermal conduction model was established as fluid temperature changes along fluid flowing.The calculation and the affecting factors of fluid flowing pressure drops through the collector absorber pipe were studied.Integration schemes of energy fluxes and mass flows between solar utilization subsystem and coal-fired generation subsystem were put forward.And some typical SSCEG systems were given.Based on the varying operation theories of the coal-fired plant,the integration model of optimizing topological structure and parameters of a SSCEG system was set up.And the thermal performance of the optimum SSCEG system was analyzed and calculated by applying the theory of the first law,the second law and thermo-economic analysis method on it individually.Then the effects on economic performance of integration scheme,thermal parameters of the solar field,capacity of the coal-fired power unit and whether the structure of the coal-fired unit changing or not were discussed.Finally,integration rules were summarized.Calculation method of coefficient of extemal bonds(CEB) was discussed,and the CEBs of different flows in different coal-fired units were obtained.Then the coupling mechanism of the SSCEG was researched based on the non-equivalence performance of exergy.Thermodynamic analysis model of a SSCEG system was set up.Then the thermal performance of the SSCEG system was analyzed and its unit electricity generation cost was calculated by applying the model in Lhasa and Hohhot in China.And the results show that,in Lhasa,the solar thermal electricity generation cost of the SSCPG system integrated with the national 300MW coal-fired generation is 0.57￥/kW·h.And it is 0.75￥/kW·h when integrated with the national 600MW units in Hohhot.There exist regions where the electricity generation cost of using solar thermal is equivalent to that of using other renewable energy in China.So the SSCEG technology is a promising way for energy conservation technically of cola-fired power plants and the large-scale utilization of solar energy in China.