Ray Trace Analysis for Concentrating Sunlight Onto an Optical Fiber Bundle

A two-axis concentrating solar collector/receiver is being designed to concentrate visible solar irradiance and distribute it inside a building for daylighting via a bundle of polymer optical fibers. This paper is concerned with the optics that will provide uniform illuminance of the visible spectrum on the entrance of the fiber optic bundle. A fiber optic bundle made of 3mm diameter fibers and a non-imaging device along with the solar collector’s primary and secondary mirrors has been modeled in a ray-tracing software package, TracePro 3.3. Fiber optic bundles of two different geometries were considered, viz. a square bundle with 225 fibers and a round bundle consisting of 126 fibers. The purpose of this research is to determine the optimum length of the non-imaging device that could provide uniform illuminance on the entrance area of the fiber optic bundles. Sensitivity analyses are conducted to see the variations in the output due to different possible off-set conditions, such as distance between the primary and the secondary mirror, the secondary mirror off-set from the primary mirror optical axis, and misalignment due to tracking error. The results of the sensitivity analyses are presented, and recommendations are made for the design of the non-imaging device. It is shown that the square non-imaging device and fiber bundle is superior to the round non-imaging device and fiber bundle.