Thermal Performance Research On Solar Compound Parabolic Concentration System

Energy has become the lifeblood of the national economy.Fossil energy on the planet is limited and the recoverable age is rapidly decreasing with the acceleration of industrialization,which leads to a growing world energy crisis.At the same time,using fossil energy in the process of industrialization will produce a series of environmental pollution problems.As we all know,solar energy is the source of many renewable energy sources,but in the process of solar photothermal utilization,it will also be limited by the defects of low energy flow density,intermittent energy supply,large difference of seasonal energy supply and so on.As a result,the energy supply flow density of solar energy can be improved by focusing light technology.Among them,the Compound Parabolic Concentrator(CPC)receives researchers' widespread attention,because CPC has the characteristics of low accuracy requirement for tracing sun,coincidence of receiver position and center of gravity of concentrator,internal focusing,convenient maintenance and absorbable partial scattered light.Therefore,a new kind of CPC is designed,and the factors that affect the performance of the concentrator are analyzed and tested.Based on this,a solar compound parabolic concentration system is built to study the thermal properties of the system.Firstly,a CPC with fixed size receiver is designed and a 3D model is established.Then,using Light Tools to carry out optical simulation calculation on the influence of the placement height of the plate receiver in a single-layer glass tube and incidence Angle on the optical performance of the CPC.The results show that when the incident angle ? is 0° and 12° respectively,the light receiving rate and concentrating efficiency of the CPC increase first and then decrease with the increase of the receiver placement height(h).When the h optimum value is 20 mm and the incident angle range ? is 0?12°,the light receiving rate and concentrating efficiency of the CPC decrease with the increase of the incident deflection angle.When the incident deflection angle ? =0°,the light receiving rate and concentrating efficiency of the CPC are 99.48% and 89.53%,respectively;when the incident deflection angle ?=12°,the concentrating efficiency is 50.3%,which is 43.84% lower than the incident deflection angle ?=0°.Based on the results of optical simulation,a test bench for thermal performance of CPC is built to study the properties of different receivers embedded in single-layer glass tube.The thermal characteristics of the CPC,such as the temperature difference between inlet and outlet,the temperature in the cavity,the temperature of the glass cover,the heat collecting efficiency and so on,are tested and analyzed.Obtained: when the plate receiver is embedded in the single-layer glass tube,the average temperature difference between the two surfaces of the plate receiver is 0.5? when the mounting angle is ?=0°,and the average collector efficiency of the CPC is 32.32% higher than ?=90°.When a triangular receiver is embedded in a single-layer glass tube,tests is carried out at different flow rates.Obtained: the temperature difference between the inlet and outlet of the single-layer glass tube and the temperature in the cavity decreases with the increase of the velocity of air medium.When the air medium flow rates were 1.03,2.01 and 3.03 m/s,the concentration collection efficiency of triangular receiver is 56.8%,60.7% and 70.76%,respectively.Since the V receiver can deform inward when heated and reduce the extrusion to the single-layer glass tube.The test results show that when the velocity of air medium in the V receiver is greater than 3.03 m/s,the concentration collection efficiency is 58.97%,which can provide reference of selecting receiver for the solar compound parabolic concentration system.A solar compound parabolic concentration system with an embedded V receiver is built outdoors.The influence of the incident deflection angle of the system,the number of concentrators in series and frosting on the thermal performance of the system is tested and analyzed.The results show that the temperature rise of the concentrator shows the change trend of first increasing and then decreasing when normal incidence and the incident deflection angle ?=10°.when the incident deflection angle ?=10°,the average temperature rise of the condenser is only 3.4? less than normal incidence.When the initial temperature of the circulating air medium is 23.21?,the maximum temperature of the air medium at the outlet of each stage is 44.66?,60.24?,71.59? and 81.65? respectively after the step by step heating of four concentrator.But the concentration collection efficiency is gradually decreasing.In addition,the frosting on the surface of the glass cover plate of the condenser will affect the temperature rise of the circulating air medium and the temperature of the cavity.