Outdoor performance evaluation of a holographic solar concentrator optimized for building integration

Abstract

A holographic solar concentrating system with a Silicon photovoltaic (PV) cell is designed, constructed and characterized. The design is based on a previous system and is further optimized. The cylindrical holographic lenses forming the concentrating system are modeled with a ray-tracing algorithm based on Coupled Wave Theory and are recorded on Bayfol® HX photopolymer. Measurements are carried out outdoors with solar illumination and provide a current density of 146 mA/cm2 with a current concentration factor of 3.48, validating the theoretical simulations results (172 mA/cm2 and 3.81, respectively). The effect of the temperature on the performance of the Holographic Optical Elements (HOEs) is studied and taking it into account by assuming a 1.3° tilt of the fringes of the hologram caused by thermal expansion (which is reversible if the HOEs are encapsulated and sealed) provides simulation results closer to the experimental ones (a current density value of 155 mA/cm2 and current concentration of 3.43). The ageing of HOEs recorded in Bayfol® HX photopolymer due to the outdoor environmental conditions is also analyzed, revealing the need of encapsulation and sealing.