Solar energy transmission and concentration by an optical fiber bundle with a frustum-type output end

The notion of transporting concentrated solar energy radiation by flexible optical fibers or fiber bundles has been developed for a variety of uses. With the aim of CW pumping a laser crystal outside the focusing area of a primary parabolic mirror, an optical fiber bundle with a frustum-type output end was used to transmit and concentrate solar energy to a flux level high enough to pump a solid state laser. The transmission properties of a fiber optic frustum-type concentrator was first analyzed with the help of a ray-tracing program, which revealed strong influences of both output diameter and length on the transmission efficiency of a frustum concentrator. The idea of achieving an ideal angular transformer with fiber optic technology in the area of nonimaging optics was also proposed. The output section of each optical fiber was polished to form a hexagonal frustum. When seven of these polished frusta from the optical fibers were joined together, a novel solar energy concentrator was obtained. The output power from the concentrator end was 67 W, corresponding to the solar flux of 23 W/mm2. The experimental results of transporting and concentrating the solar radiation by using four fiber bundle with a square frustum output end was also reported. The maximum solar flux of 28 W/mm2 was obtained with a single optical fiber of conical output end.