Construction And Photothermal Performance Of Arc-shaped Absorber Composite Parabolic Concentrato

The rapid development of science and technology and the increasing economic growth have accelerated the consumption of traditional fossil energy.The long-term exploitation and utilization of traditional energy have not only accelerated the depletion of primary energy,but also brought serious environmental pollution.With the deepening of the "two-carbon" strategic goal,it is imperative to actively promote the energy revolution.New energy,as an alternative to fossil energy,is the energy cornerstone of human society in the future.As a new energy source,solar energy is widely used because of its abundant resources,wide distribution and continuous regeneration.Solar compound parabolic concentrator(CPC)which can collect scattered solar radiation and use it efficiently has been widely studied by researchers.In this paper,according to the design principle of CPC and the theory of differential geometric curve,a mathematical model is constructed to solve the reflector shape of CPC,and an A-CPC is proposed which can concentrate the incident rays less than the receiving half angle in a section of the arc of the vacuum tube.The optical performance of A-CPC is verified by theory and experiment.At the same time,the annual daylighting model and heat transfer model of A-CPC were constructed,and the experimental platform of A-CPC photothermal conversion was built to study its photothermal conversion performance.The main contents and conclusions of the study are as follows:(1)Based on the principle of edge ray and the law of geometrical optical reflection,a mathematical model for solving the reflector shape of the non-concave absorption non-imaging solar compound parabolic concentrator(CPC)is constructed according to the theory of differential geometric curve.The reflector shape equation of the CPC of several common absorbers(plate,vertical plate,circle)is solved by using this method.The solution results verify the convenience and reliability of the established equations.(2)Based on the circular absorber CPC,a novel A-CPC is proposed,which can focus the incident rays not more than the receiving half angle in a section of the arc of the vacuum tube.The reflector shape equation of A-CPC is obtained by differential geometry theory.According to Monte Carlo ray tracing theory,the correctness of the model is verified by combining theory and experiment.In addition,the optical aperture width and model height of A-CPC are reduced by 15.6% and 30.3% respectively compared with that of C-CPC with the same absorber radius and receiving half angle,thus reducing the manufacturing cost.(3)According to the Monte Carlo ray tracing method,the optical efficiency difference between A-CPC and C-CPC was obtained by simulation.The receiving half angle of A-CPC was increased to ±38°,which could collect solar radiation in A wider range.Moreover,the energy flux density of A-CPC absorber in the range of 40°to 140° was improved.The convective heat transfer loss between the upper surface of the absorber and the sky is reduced.Combined with the solar direct scatter radiation separation theory and typical annual meteorological data,the annual daylighting model of CPC was established.VC++ programming was used to obtain the direct scatter radiation collected by C-CPC and A-CPC.The comparison showed that the total solar radiation collected by A-CPC was 25.70% higher than that by C-CPC.Moreover,the average daily effective working hours of A-CPC direct radiation collection have also been increased.(4)In order to explore the photothermal conversion performance of the A-CPC model,combining the law of conservation of energy and the numerical model of the ACPC system,it is found through the experimental platform that the theoretical values of the inlet and outlet temperatures are in good agreement with the experimental values,and the maximum relative error is-6.37%.The experimental photothermal conversion efficiency is higher than the theoretical value,the maximum relative error between the theoretical value and the experimental value is-8.35%,the average theoretical and experimental photothermal conversion efficiency is 60.36% and 57.62%,respectively,the maximum relative error is-4.76%,which better verifies the reliability of the A-CPC photothermal conversion experimental platform.