Research On Key Technologies Of Biomass Carbon-based Phase Change Heat Storage Dish Solar Thermal Power Generation System

Energy is the cornerstone of human survival and social and economic development.Today’s energy development is faced with three major challenges:resource shortage,environmental pollution and climate warming.In order to meet these challenges,countries around the world have successively introduced various countermeasures and energy development strategies.By formulating a series of strategies,goals and laws,flexibly using market mechanisms,actively guiding public participation,and vigorously promoting low-carbon innovative technologies,the EU has become a forerunner and leader in global low-carbon energy transition and addressing climate change,The new energy security strategy of "one cooperation"and "four revolutions" was proposed by President Xi Jinping in June 2014.At the 75th United Nations General Assembly held on September 22,2020,Chinese President Xi Jinping pointed out:"China will increase the implementation of policies and measures,enhance its nationally determined contribution,and take proactive measures to achieve carbon dioxide reduction.Emissions are expected to peak before 2030,and strive to achieve carbon neutrality and achieve balance before 2060.”From the above,we can see that China is resolutely promoting green,low-carbon and sustainable development in tackling climate change.the way.At present,China’s energy structure is also adjusting,striving to achieve a clean,low-carbon,electrified transformation,and vigorously develop non-fossil energy into electricity.Solar thermal power generation technology is a high-efficiency thermal power generation technology by means of solar concentrating.At present,this technology is in a period of vigorous development and is developing very rapidly.It may become one of the main forms of solar power generation in the next few years.In view of the development and prospect of this technology,this paper conducts in-depth research on the key technologies of biomass carbon-based phase change heat storage dish solar thermal power generation systems,and prepares composite phase change materials using pine sawdust as carbon source.The heat absorption characteristics of dish solar energy are designed as a spherical packed bed suitable for medium and low temperature heat storage of dish solar energy,and a coupled numerical model of light field-flow field-temperature field is constructed.The multi-energy complementary system of the dish solar coupled phase change heat storage auxiliary coal-fired unit is proposed,and the economics of the operation of the solar combined coal-fired unit is studied.The results show that:using pine sawdust as carbon source,porous carbon with specific pore structure was prepared by pyrolysis activation process as the matrix of composite phase change material.It was found by SEM and FTIR characterization that the melted phase change material can be uniformly filled into the pores,and at the same time It has good chemical stability in the composite process,and the thermal conductivity can be enhanced by loading metal ions.The thermal conductivity of PC-Fe can reach a maximum of 0.57 W/(m·K).The new composite phase change material is used as the heat storage medium.Packed bed heat storage experimental system,the experimental results show that the effect of biomass porous carbon addition ratio on the composite phase change material packed bed heat storage and release system is greater than the effect of inlet temperature and inlet flow rate on it.When the addition ratio of porous carbon increases from 3%When it reaches 9%.the total efficiency of the heat storage and release process increases from 61.17%to 77.02%.Taking the packed bed heat storage device in the combined cycle system of the dish-type solar-assisted coal-fired unit as the research object,the physical model of the actual size parameters and the mathematical model of the packed bed heat storage flow and heat transfer process are established.To ensure the accuracy,the research on the influence of spherical heat storage unit and heat transfer fluid on the thermal performance of the packed bed was carried out.The results show that when the heat storage unit is reduced from 90mm to 50mm,the heat storage time of the packed bed is shortened by 61.5%,and the heat release time is shortened by 62.5%.The time is shorter than that of the staggered arrangement,but the heat storage rate is lower than that of the staggered arrangement.The inlet flow rate has a greater effect on the heat storage and release performance of the packed bed,and the instantaneous heat release rate of the packed bed is optimized,and the heat release of the packed bed can be better controlled by the operation mode of variable flow rate.The installation position of the heat absorber can directly affect the energy distribution of each inner cavity surface,thus the heat absorption efficiency of the dish solar system.When the working medium flow rate of the heat absorber is constant,the medium and low temperature heat source generated by the dish solar energy increases the amplitude of the working medium temperature.It is closely related to the solar radiation intensity,and the two basically show a linear relationship:when the cavity depth and lighting radius of the heat sink are the same.among the four cavity structure heat sinks designed in this paper,the circular type heat sink has higher thermal efficiency,The heat loss of the dome heat absorber is relatively large.When the dish type solar medium and low temperature heat source is connected to the low-pressure heating condensate water circuit,the inlet of the No.8 low-pressure heater is supplemented with the solar heat source,which needs to increase the condensate water diversion amount and the flow rate of the heat conducting medium,which increases the system resistance,but can significantly improve the unit economy;When the dish-type solar combined coal-fired unit is running,the phase change heat storage system is put into operation,which can effectively reduce the coal consumption of the combined cycle unit under the condition of low irradiation.Compared with the traditional coal-fired unit,the coal saving is obvious.Therefore,the biomass carbon-based phase change heat storage dish solar thermal power generation system can effectively reduce carbon emissions and improve the unit economy,providing new ideas for the complementary utilization of medium and low temperature solar energy and coal combustion and the comprehensive utilization of biomass carbon.