The Coupling Mechanism And Thermodynamic Characteristic On Solar Tower Aided Coal-fired Power Generation System

Electric power is the pillar of social development and one of the lifelines of the national economy.In China,coal-fired power generation accounts for about 70% of the total.Therefore,coal-fired power plants are generally the key research objects concerning energy conservation and emission reduction in the power sector or even the whole industry.By far,China's coal-fired power generation technology has reached an advanced level in the world.On the basis of the available technology,further energy saving relies on the development of external renewable energy.Solar thermal power generation technology uses high-temperature and high-pressure steam generated by focused solar energy to work in turbines.With similar principles to the coal-fired power generation technology,this technology has now entered the phase of commercial use.Solar aided coal-fired power generation system(Eo DSL: coupled system)integrates solar thermal power generation technology and coal-fired power generation technology to replace part of the heat source(coal)by solar thermal energy,therefore saving coal consumption or increasing power generation.Through sharing turbines and regenerative system with the coal-fired power system,smaller investment is required.The disturbance on power generation due to unstable solar resource can also be reduced by the advantageous(large capacity,high parameters,and high stability)of coal-fired power plants,so as to generate electricity in a stable manner.In this paper,the coupling mechanism and thermal characteristics of solar tower aided coal-fired power generation system are studied,and a quantitative analysis of the system is carried out by modeling and simulation.The main work and conclusions of the study are as follows:Firstly,based on the heat transfer analysis of solar tower/parabolic trough solar aided coal-fired power generation systems and coal-fired power generation systems,the static and dynamic mathematical simulation models are built and verified respectively.The static and dynamic operation characteristics are studied under the disturbances from solar radiation and electric power dispatch.Then,the models of solar thermal power generation systems and coal-fired power generation systems are integrated into solar aided coal-fired power generation systems,which provide a model for further study.Secondly,exergy and advanced exergy methods are used to analyze the exergy distribution and the reason for exergy destruction of solar tower aided coal-fired power generation system.This can point out the research orientation of the paper.The exergy destruction of each component itself is much larger than that caused by the system structure.Therefore,the thermal performance of each component should be improved in the first place,and then the external system structure should be optimized to reduce the influence of system structure on exergy destruction.The energy-saving function of solar tower aided coal-fired power generation system should be improved mainly from the boiler and the solar tower field,and the exergy efficiency of the coupled system can be improved by reducing the heat transfer temperature difference in the boiler and the solar tower field.In the next step,the solar contribution evaluation method of the coupled system is built,which is used to classify,prejudge and evaluate the coupling schemes of solar tower aided coal-fired power generation system,together with pinch point and exergy analysis methods,to acquire the best coupling scheme.The annual operation characteristics under off-design working conditions are analyzed to study the dynamic characteristics of the coupled system under variable solar radiation and electric power dispatches.These characteristics can also verify the correctness of the preferential process.The study provides a method to select the optimal coupling scheme of solar tower aided coal-fired power generation system.Finally,the financial issues(including the investment situation,the income situation and others)of solar tower aided coal-fired power plant are taken into consideration with the financial analysis models of real power plants and the thermodynamic parameters within the whole life cycle of the plant.After comparison with solar tower power plant or coal-fired power plant,the financial advantages of solar tower aided coal-fired power plant can be found,and the study can serve as a reference of the feed-in tariff for policy makers.