The approach selected is the fabrication of holographic optical elements, which will focus sunlight to either a line or a point. A concentrating mirror is replicated in the hologram which consists of dichromate gelatin exposed to a laser beam. The dichromate gelatin can be processed to produce a nonuniform microstructure, which gives the hologram a significant waveband width. Even so, it becomes necessary to stack at least three holograms, with each hologram reflecting a different region of the solar spectrum, if we are to reflect most of the solar energy. To achieve high efficiency, it is necessary to obtain adjacent quasi-square waves for the efficiency-wavelength profile of each of the holograms in the stack. Profile information was obtained by the use of a monochromator coupled to a computer. An optical efficiency in excess of 50 percent was measured for a three hologram stack. This represents approximately 70 percent of the efficiency achievable within the limited measuring range of the monochromator. A line-focus holographic concentrator model has been built for demonstration purposes. A cost analysis for mass producing holographic concentrators indicates that holographic concentrators become cost effective in relation to mass-produced conventional concentrators when the holographic optical efficiency exceeds 70 percent. To surpass this number, it becomes necessary to produce a five hologram stack and to broaden the monochromator optical sensitivity range.

Date Published: 23 February 1987
PDF: 7 pages
Proc. SPIE 0692, Materials and Optics for Solar Energy Conversion and Advanced Lightning Technology, (23 February 1987); doi: 10.1117/12.936675

Published in SPIE Proceedings Vol. 0692:
Materials and Optics for Solar Energy Conversion and Advanced Lightning Technology
Sandor Holly; Carl M. Lampert, Editor(s)