Design And Experimental Study Of Tracking-free Linear Fresnel Solar Concentrating Collector

The rapid development of the world economy depends on the widespread use of non-renewable energy sources such as oil,natural gas and coal.However,due to the increasing consumption of non-renewable energy,a worldwide energy crisis has been triggered.Because of its clean,environmentally friendly,inexhaustible and wide-ranging characteristics,solar energy has received great attention.The design of solar collectors with low cost,high efficiency and simple structure is the main research goal of all countries.At present,the widely used concentrating solar collectors include:parabolic trough,tower,Fresnel and dish solar collectors.In order to improve the efficiency of solar energy utilization,a variety of different types of tracking solar collectors have been designed and studied,including tracking-free,single-axis tracking and dual-axis tracking solar collectors.In view of the high cost,low efficiency and complex tracking structure of the above different types of solar collectors,this paper proposes a low-cost,efficient and simple structure-free linear Fresnel concentrating set.The heat exchanger describes the design method and working principle of the collector,and the 3D modeling of the created collector is imported into the simulation software Tracepro for spot simulation analysis.Finally,the experimental platform of the tracking-free linear Fresnel concentrating collector system is built,and the concentrating and collecting performance experiments are carried out.The collector efficiency of the collector is calculated,and the experimental data and simulation are obtained.The resulting data is compared.The main research contents and conclusions are as follows:(1)Based on the three laws of linear propagation,refraction and reflection of light,this paper analyzes the principle of concentrating the linear Fresnel lens to determine the installation position of the vacuum collector.At the same time,based on the edge ray principle of ray tracing and the mathematical expression of involute,a design method of compound parabolic concentrator(CPC)is obtained.According to the law of the whole year of the sun,combined with the local geographic latitude position,the expression of the installation angle of the Fresnel lens is determined.Finally,this paper combines a compound parabolic concentrator and a linear Fresnel lens to design a linear Fresnel solar collector that can achieve tracking-free to some extent,and its working principle is carried out.(2)In the 3D drawing software SolidWorks,the designed tracking-free linear Fresnel solar collector is modeled,and the model is imported into the optical simulation software TracePro,and the ray tracing simulation analysis is carried out.In this paper,the receiver installation position is simulated and the best installation position is 600 mm.This paper analyzes the concentrating performance of this collector under different solar irradiances,and simulates the optical path of the sun during one day(the solar declination angle is-21°),and calculates the average optical of the collector.The efficiency is 46.34%and the maximum optical efficiency is 52.59%.This paper simulates the trajectory of the sun in one year,and obtains the annual average optical efficiency of the collector when there is slippage is 51.37%,and the annual average optical efficiency without slip is 18.57%,which changes through optical efficiency.The situation analysis shows that the concentrating effect of the collector when there is slippage is better than that of the collector without slip.(3)Based on the theoretical design and optical path simulation analysis of the tracking-free linear Fresnel solar collector,an experimental platform for tracking-free linear Fresnel solar collector system is built.This paper introduces the three main experimental systems of this collector and screens the experimental measurement equipment.In the sunny weather conditions with solar irradiance of about 700 W/m~2,the collectors were subjected to heat collection experiments with slip and no slip,and the heat collection efficiency was calculated by measuring the data.The results show that the average heat collection efficiency with slip is 22.9%,and the average heat collection efficiency without slip is 6.40%.Therefore,when there is slip,the collector has higher heat collection efficiency than when there is no slip.Finally,when the loss coefficient is 0.88,the experimental results are in good agreement with the simulation results,and the accuracy of the simulation results is verified.