Research On The Design Method Of Solar Concentrator With Lightguide

With regard to the solar concentrator with lightguide,neither imaging optics nor nonimaging optics can be applied to meet the system design requirements because of its complex structure.Based on the practical requirements of the solar concentrator with lightguide,the design project can be found by connecting imaging optics and non-imaging optics.This paper focuses on the research of the design methods of solar concentrator with lightguide to establish a concentrator design theory for high concentration ratio and high efficiency and provides a series of optical solutions for the concentrators with lightguide.In the first stage,a solar concentrator design method is proposed to solve the falling coupling efficiency caused by alignment error between the collector array and lightguide in existing solar concentrators with lightguide;and two types of solar concentrators with lightguide are established.The solar concentrator with lightguide based on artificial optical compound eye adopts the collector design with cylinder and eliminates the alignment error in traditional solar concentrators with lightguide,tethered to the lightguide through an optical coupling structure.At the same time,the proposed solar concentrator can simplify the traditional dual-axis solar tracking mode and save the design cost because of the property of the cylinder lens.The solar concentrator with lightguide based on paraboloid array adopts part of paraboloid as the reflecting surface of the collector,adding triangular prism coupling structure to the bottom surface of the collector to free the alignment error between the collectors and lightguide from correction.In this design of the solar concentrator with lightguide,the angle between the concentrated rays and horizontal plane can be decreased,and the propagating length between total inner reflections can be increased,which can reduce the possibility of the ray leakage from the lightguide.However,both cylinder and paraboloid belong to conventional surface which has low design freeform and limited capacity to control the rays.It is necessary to find an optical design method with high design freeform to offset the limited capacity problem in conventional surfaces.The work in the second stage of this paper is oriented toward the freeform surface design methods to solve the limited capacity of the conventional surfaces in the first stage according to the high design freedom characteristic in freeform surfaces.A Fresnel solar concentrator with lightguide is proposed firstly,which decreases the system aspect ratio because of the sawtooth structure with ultra-short focal length total inner reflection based on freeform surface.At the same time,the falling efficiency caused by surface shape error can be improved by a modified freeform discrete shape design method.Due to the progress of the sunlight focusing and forming a circle spot with predetermined distribution by solar concentrators,which is viewed as an optimal transportation problem,an elliptic Monge-Amp?re equation in optimal transportation problem is derived in mathematics level.The freeform reflected surface shape is solved combining Snell law with law of the conservation of energy with an elliptic MongeAmp?re equation construction with nonlinear boundary conditions.The proposed design method has high efficiency and design freedom and provides a well optical solution to the concentrator freeform shape.But part of rays can leak from the subsequent coupling structures in lightguide,which impact the efficiency.In the third stage,two ray-leakage-free methods specially designed for point-focusing and line-focusing lightguide types are proposed to solve the ray-leakage problems in the first two stages;and two examples are proposed to validate the suggested methods correctness when collector shape is paraboloid.Under the ray-leakage-free premise,the point-focusing and linefocusing lightguides are improved to solve the problem of short ray-leakage-free distance,which increases the geometrical concentration ratio with high efficiency.Finally,the maximal ray-leakage-free concentration ratio and concentration abilities of the two types of rayleakage-free concentrators with lightguide are compared.The design method of ray-leakagefree lightguides,proposed in this stage,can maintain high efficiency and geometrical concentration ratio for solar concentrators with lightguide and promote further development in solar concentrators with lightguide.