Photopolymer Holographic Lenses for Solar Energy Applications: A Review

Abstract

Holographic lenses (HLs) are part of holographic optical elements (HOE), and are being applied to concentrate solar energy on a focal point or focal line. In this way, the concentrated energy can be converted into electrical or thermal energy by means of a photovoltaic cell or a thermal absorber tube. HLs are able to passively track the apparent motion of the sun with a high acceptance angle, allowing tracking motors to be replaced, thus reducing the cost of support structures. This article focuses on a review of the materials used in the recording of a holographic lens (HL) or multiple HLs in photovoltaic and/or concentrating solar collectors. This review shows that the use of photopolymers for the recording of HLs enables high-performance efficiency in physical systems designed for energy transformation, and presents some important elements to be taken into account for future designs, especially those related to the characteristics of the HL recording materials. Finally, the article outlines future recommendations, emphasizing potential research opportunities and challenges for researchers entering the field of HL-based concentrating solar photovoltaic and/or concentrating solar thermal collectors.

Keywords: electrical energy; holographic lenses; photopolymers; solar energy; thermal energy.

Figure 1

Representation of solar radiation with respect to the receiving surface.

Figure 2

On-axis holographic setup.

Figure 3

Asymmetrical off-axis holographic setup.

Figure 4

Symmetrical off-axis holographic setup.

Figure 5

Holographic setup for the recording and reconstruction of reflection HLs.

Figure 6

Theoretical results based on Kogelnik’s theory for transmission holograms. (a) Theoretical comparison between volume holograms with different frequencies. Considered $n_1=0.004$ and $d=60$ $\mathsf{\mu }$m. (b) Theoretical comparison between volume holograms with different optical thicknesses (d). Considered $n_1=0.004$, $f=500$ l/mm.

Figure 7

Chemical process for hologram recording in silver halide materials.

Figure 8

Interferential pattern storage of a phase hologram by refractive index modulation in a photopolymer.

Figure 9

Schematic diagram of a holographic solar concentrator with off-axis angular multiplexing.

Figure 10

Representation scheme for the solar concentrating system of a HL and PV.

Figure 11

Representation scheme for the solar concentrating system of a HL and PV.

Figure 12

Outline of the results obtained so far for HSCs as a function of the photopolymers and strategies used [72,73,82,83,84,85,86,87,88,93,94,95,96,97,98,99,102,103].

Figure 13

Outline of the different strategies used to optimize the most important parameters in the design of holographic solar concentrators. DE: diffraction efficiency, AA: acceptance angle [72,73,82,83,84,85,86,87,88,93,94,95,96,97,98,99,102,103].

Figure 14

Comparison in terms of efficiency, durability, cost-effectiveness, and nontoxicity for Bayfol HX200 (blue), acrylamide-based photopolymers (red), and acrylate-based photopolymers (green). The comparison criteria are defined from 0 (not at all) to 10 (very much).