Optimization And Coating Aging Test Of Concentrating And Heating System For Solar Tower Power

Solar power tower technology is considered as one of the most promising concentrated solar power technologies because of its high photothermal conversion efficiency and the scalability of heat storage system and power generation.As the front part of the whole system,the concentrating and heating system affects the energy input of the subsequent subsystems directly.In-depth study on it is beneficial to improve the photothermal conversion efficiency and hence the performance of the whole system from the source of the power generation process.In this paper,for the concentrating and heating system,research work is carried out in four aspects,namely,the heliostat field,molten salt receiver,coating characteristics and aiming strategy optimization.A heliostat simulation model was built based on geometric projection method and i HFLCAL analytical method,and then verified by the measured flux density distribution data,which the relative error of average energy flux density is 3.57%.A 3-D dynamic simulation model of receiver was established based on heat transfer mechanism and thermoelastic mechanics and then verified by the test data of the Solar Two power station,which the absolute error of outlet molten salt temperature is less than ± 1°C.Moreover,a photothermal-mechanical coupling concentrating and heating system model was developed to study the receiver’s dynamic characteristics under the single focus strategy.Results showed that the maximum temperature of the tube wall can reach 634°C and the maximum thermal stress can reach 540 MPa,which will impose a great influence on the operation safety of the receiver.The effect of coating characteristics on the receiver’s performance were also analyzed.The coating absorptivity had a significant effect on the thermal efficiency of the receiver.When the coating absorptivity decreased from 0.95 to 0.85,the thermal efficiency of the receiver decreased from 88.14% to 78.81%.Therefore,the decay characteristics of coating absorptivity were studied by aging test.Results showed that drastic temperature reduction and frequent temperature fluctuation would lead to the decay of coating absorptivity.For the aiming strategy of the heliostat field,the differential evolution algorithm was adopted to conduct a multi-objective optimization of flux distribution uniformity and energy overflow loss,and a single-objective optimization of the photothermal conversion efficiency,respectively.The former used non-dominated sorting and crowding strategy and obtained the pareto front of the heliostat field aiming strategy.The latter effectively improved the operation performance of the concentrating and heating system while ensuring the operation safety of the receiver.Under the five testing conditions of the Solar Two power station,the output power of the receiver could be increased by more than 5%.The research work of this study is expected to provide a theoretical model for the design and optimization of the concentrating and heating system as well as a reference for the operation and maintenance of the receiver in solar tower power system.