Study On The Optical Properties Of The Point Focusing Fresnel System

China officially put forward the carbon peaking and carbon neutrality goals in 2020.Among all the industries in China,the electric power industry has the highest carbon dioxide emissions.Therefore,low-carbon transformation of the electric power industry is imperative,and replacing fossil fuels with clean energy is the development direction of the future power system.Solar tower thermal electricity is one of the main technologies of future electrical power system,which can realize 24 hours continuous power generation by using solar energy.It is important to calculate solar flux distribution with a precise and simple method for the design and optimization of solar tower systems.In this paper,a function method and a system efficiency calculation method are developed for calculating the flux density distribution formed by the point focusing Fresnel mirrors on the receiver.And on this basis,a new design to move the receiver laterally is presented.The method of optimization aims to get the maximum annual average optical efficiency,which takes into account the changes of solar energy resources from moment to moment within a year,and considers the design scheme of the heliostat field as well as atmospheric absorption,optical error,absorption and heat loss of the receiver,reflectivity of the heliostat and other physical factors.The receiver position of the point focusing Fresnel system is optimized in this paper Within a certain range of space,taking the cosine factor and intercept factor as the primary goal of decision-making,the optimal positions of the receiver are calculated at different solar elevation.The receiver moves laterally at a height of 34 meters whose tilt angle is 35 degrees after optimizing,the solar elevation for the direction of the heliostat fixed at the shaft is 45 degrees,and the best minimum solar elevation without shading and blocking to decide the distance of the adjacent row of heliostat is 27 degrees.The performance analysis of the optimized design shows that the annual averaged optical efficiency is about 81%with a geometrical concentration ratio of 300.Its optical efficiency is about 6%higher than that before optimization of the receiver,and about 23%higher than that of the conventional solar tower system PS10.The research content in this paper has a certain significance for our electric power industry’s low-carbon transition and the realization of carbon peaking and carbon neutrality goals as scheduled.