A spectral splitting planar solar concentrator with a linear compound parabolic lightguide for optical fiber daylighting

For the sake of taking full advantage of solar energy, an optical fiber daylighting system is proposed in this paper. To achieve a uniform irradiance distribution and a great concentration ratio at high level, innovative collectors and compound parabolic lightguide (CPL) are designed based on edge-ray principle and total internal reflection (TIR). The surface of the collectors is designed as paraboloid to drive the concentrated rays possessing a certain level of oblique angles before coupling into the lightguide, which simplifies the design difficulty and processing difficulty of the couplers and suppresses the light leakage. The beam splitters can separate full spectrum rays into visible and invisible parts. The invisible light for compensation is collected by collector array and reflected into the solar cell which converts solar energy to electricity and drives the LED array together with the extra electricity. The LED array is considered as the compensation part because it can adjust the luminous intensity at any time according to the changes of the illuminance from the visible part. The CPL can improve the geometric concentration ratio compared to traditional planar lightguide. The simulation and experimental results show that the proposed optical fiber daylighting has geometric concentration of 200 and optical efficiency of 50%, and its concentrating characteristics can maximize the use of solar energy.