Design, fabrication, and integration of holographic dispersive solar concentrator for terrestrial applications

Abstract

Dichromated gelatin layers facilitate the design and fabrication of large format (1 m²) holographic optical elements (HOE) that exhibit high optical quality and diffraction efficiency. In this paper we present the results achieved in the development and fabrication of such layers and elucidate upon their applicability as holographic solar concentrators. The objective of this report is the presentation of the experience gained in the design and manufacturing of large format spectrally selective solar concentrators. The holographic lens diffracts the white sunlight into various spectral ranges outfitted with solar cells that have appropriately selected band gaps. The purpose of the holographic concentrator is the spectral and spatial separation of the incident solar radiation in order to achieve an improved overall conversion efficiency. A number of manufacturing techniques were especially developed for the design, optimization and fabrication of the specialized holographic concentrators. The HOEs needed for the construction of the integrated collector optics are: lenses and/or lens arrays and phase-correction plates. The HOES are designed by means of computer programs that facilitate the optimization of the recording geometry and provide information for the correction procedures needed for optimized performance. The HOEs are recorded in dichromated gelatin films (DCG) and are subsequently subjected to chemical and thermal treatment processes in order to promote the desired characteristics and suppress the undesired properties. These procedures guarantee the realization of HOEs with high diffraction efficiencies and low scattering losses. The optimized holographic process: exposure, development and after-treatment, was described explicitly in previous publications. The emphasis is placed on the development of a novel copying technique for the batch reproduction and manufacturing of large format holographic lenses for solar concentrators.