Volume Holographic Optical Elements as Solar Concentrators: An Overview

Generally, to reduce the area of a photovoltaic cell, which is typically very expensive, solar concentrators based on a set of mirrors or mechanical structures are used. However, such solar concentrators have some drawbacks, as they need a tracking system to track the sun's position and also they suffer for the overheat due to the concentration of both light and heat on the solar cell. The fundamental advantages of volume holographic optical elements are very appealing for lightweight and cheap solar concentrators applications and can become a valuable asset that can be integrated into solar panels. In this paper, a review of volume holographic-based solar concentrators recorded on different holographic materials is presented. The physical principles and main advantages and disadvantages, such as their cool light concentration, selective wavelength concentrations and the possibility to implement passive solar tracking, are discussed. Different configurations and strategies are illustrated and the state-of-the-art is presented including commercially available systems.