Construction Of Non-imaging Concentrator With Congruent Reflective Surface And Study Of Its Photothermal Performanc

With the gradual implementation of the global carbon neutrality target,the integrated application of new energy technologies in construction,transportation,environment,and other industries is becoming more and more extensive.The sustainable development technology related to solar energy,the effective use of solar energy combined with the solar concentrator photothermal conversion has attracted wide attention.The traditional Standard-Compound Parabolic Concentrator(S-CPC)has the excellent ability of simple structure,collecting and diffusing radiation in a specific acceptable angle.But the uneven distribution of energy flux density on the absorber is still a major problem.At the same time,when radiation converges on the surface of the circular absorber,the transformation of radiation energy and heat energy will produce corresponding thermal stress,which causes the thermal expansion and deformation between the absorber and the surface shape,thus reducing the energy obtained on the surface of the absorber.To solve this problem,this paper presents a Compound Parabolic Concentrator(CPC)designed based on Monte Carlo ray tracing method,which combined with VC/C++programming.On this basis,the optimization design of the CPC with new structure is carried out,and the photothermal conversion efficiency is verified by coupling the solar collector system.It aims to further optimize the performance of CPC and reduce the cost of market application.The key performance indexes of the concentrator are compared and studied.The results of this thesis can provide some technical reference for the development of concentrator.The research work of this paper and its results mainly include the following aspects:1.Through programming calculation,the original curved paraboloid of CPC is designed into the optimization model of M-CPC(Multi-sectioned Compound Parabolic Concentrator)with 14 plates of the same size.Use the 3D printing technology to print the designed solid model of the CCSM-CPC(Congruent Concentrating Surface M-CPC),and use the laser experimental device for experimental verification.The maximum absolute error between experimental results and calculated results is 1.70mm,and the average absolute error is 0.61mm.The annual daylighting amount of the summer half year and winter half year is 1.29%and 0.18%higher than that of the INLE-CPC(Interstice No Light Escape CPC)before optimization.2.The concentrator characteristics of the CCSM-CPC are studied.The calculation results show that the designed CCSM-CPC can significantly improve the uniformity of its energy density distribution.When the incidence angles are 0°,5°,10°,15°,20°,25°,The peak energy flux density of CCSM-CPC is 2209.33W/m~2,5946.38W/m~2,9489.53W/m~2,10467.67W/m~2,26598.81W/m~2 and 43321.44W/m~2,which less than the INLE-CPC before optimization.To a certain extent,it can effectively reduce the peak energy flux density and increase the service life of the absorber.3.According to the law of conservation of energy,a systematic photothermal conversion model was constructed by analyzing the thermal performance of the entire CCSM-CPC solar heat collection system,and the model was verified by indoor simulation and outdoor experiment.Through the combination of experiment and theory,it is found that the experimental and theoretical values of the outlet temperature of the CCSM-CPC vacuum tube are relatively consistent,the average relative error is about5.83%.When the volume flow rate is 5 m~3/h,the average heat loss of the system is19.84W,accounting for 10.66%of the energy received by the absorbing coating,89.34%of the remaining energy is transferred to the working medium on average.The calculated average heat collection efficiency is 55.06%respectively,indicating that the CCSM-CPC solar heat collection system has a high heat collection efficiency.4.Under the condition that the width and depth of the optical port remain unchanged,the number of planes composed of the concentrator surface is changed to standardize the surface shape of CCSM-CPC and explore the influence of plane concentrator surface segments on the optical and thermal properties of CPC.As the number of segments decreases from 15 to 3,the photothermal conversion efficiency of the system is 61.63%,60.40%,59.08%,57.54%,55.21%,51.99%and 44.52%.After comprehensive consideration of performance and cost,the total performance-cost factor of CCSM-CPC(15-9)remains in the range of 0.8-0.84,which showing the strong replaceability.