Improving Angular Response of Crossed Compound Parabolic Concentrators Using Rectangular Entry Aperture

A novel design of crossed compound parabolic concentrator (CCPC) that has a rectangular entry aperture is presented, which has the advantage of considerably improved angular response compared to a conventional CCPC that has a square entry aperture. It is found that the half acceptance angle of this novel design is 40° for a 4.0x rectangular concentrator when operating in the “east-west” direction, which is approximately 10° larger than that of a conventional square concentrator of the same concentration ratio. This is a substantial increase and completely unexpected because the design theory for this type of concentrators predicted a much smaller half acceptance angle of 26.6°. Experimental and simulation work reported in this paper confirms this discovery. The results reveals that the observed improvement is attributed to multiple light reflection inside the concentrator, which was not considered in the commonly employed design theory. An important implication of this work is that the multiple light reflection plays an important role in the angular response of the CCPC and its effect cannot be neglected in the design.