Research On The Light-to-heat Conversion Characteristics Of The Circular Absorber Composite Plane Concentrator

The step of progress in human society has gradually been accelerating,especially in the rapid development of the industrial revolution.The prelude to the consumption of traditional energy had been fully opened.The utilization of large amounts of energy provides a powerful driving force for the development in nowadays society,which also results in energy crisis times.Therefore,renewable energy has become more and more attention.The proportion of renewable energy in the world’s energy structure is increasing,and the research on solar energy is the most active.In the field of solar energy utilization,the compound parabolic concentrator(CPC,in short)attracts extensive attention due to the more stable performance when it operates statically.However,the high requirement of its manufacturing technology because of the arc-shaped structure of CPC makes it difficult to apply industrially,which limits the development of CPC.Hence,this thesis presented that the surface shape structure of the traditional CPC was optimized.A contrastive study of both optical and experimental efficiency was implemented according to the construction of the surface shape of the compound plane concentrator,and its main tasks include in as follows:(1)The surface shaper structure of CPC was theoretically constructed based on edge ray principle.The optical characteristics of a solar collecting system coupled with CPC were verified by optical design software(it’s Trace Pro),and its concentration ratio achieved the requirement of ideal concentrating.The yearly radiant energy compiled by the solar thermal system coupled with CPC or the traditional solar thermal system was respectively 14278.26MJ,10607.67MJ according to the separation theory of direct-scattering and the typical meteorological year data of Kunming,and their relative increasing ratio was 34.57%.(2)The structure of surface shape for the compound plane concentrator(CPLC)was theoretically constructed in term of the surface shape structure of CPC via the theory of equal escape half-angle,and its optical efficiency was obtained.A result of optical verification showed that the more dimensions of CPLC would bring about the higher optical efficiency of solar collecting model coupled with the CPLC.The optical efficiency of CPLC approximated CPC’S when the planarization dimension N tended to be infinite.The optical efficiency with a flattened dimension N of 4 is96.65%.The factors affecting CPLC were theoretically analyzed,including the heat loss of all-glass vacuum tube,the transmittance of all-glass vacuum outer tube,the absorptivity of all-glass vacuum inner tube,and the optical efficiency of quartering CPLC influenced by the reflectance of high reflecting film.It was found that the optical efficiency of the incoming light at different angles fluctuates when using optical design software(it was Trace Pro)trace rays,the reason of which was that the incoming light at different angles requires different reflective surfaces.(3)The integrating thermal characteristics of solar collecting system coupled with CPLC-4D and the traditional solar collecting system under sunny weather conditions were researched with the use of an all-glass vacuum tube as an absorber.The results illustrated that the integrating thermal efficiency of solar collecting system coupled with CPLC-4D compared to the traditional solar collector system was increased by 18.20%,when the average total radiation was 737.36W/m~2.And the rate of rising temperature for solar collecting system coupled with CPLC-4D was higher than that of traditional solar collectors.