Comparison of Uniform and Composite Matrix Diffuse Mirror Solar Concentrators and Phosphor Thin-Film Luminescent Solar Concentrator for Building Façade Applications

Urban energy resilience is needed to reduce the demand on electrical grids around the world. Building-site solar energy harvesting could aid in developing energy resilience. Building integrated photovoltaics (BIPV) are commonly used solar technologies for on-site energy production. However, when deployed on façades their performance is modest and they are unappealing. Luminescent solar concentrators (LSC) consist of a transparent plastic matrix embedded with luminescent materials that concentrate light on a much smaller area PV. They improve utilization of solar cells in vertical deployments and enhance their aesthetics. Despite these advantages, adoption of this technology is lagging due to their modest optical efficiency which is limited by escape cone losses. While methods to reduce these losses have been explored, they are limited to narrow ranges of the incident irradiance wavelength and direction. They also increase system cost. To address these issues, this study evaluated numerically the performance of a more cost-effective solar concentrator system of planar and wedge geometry that substitutes the luminescent materials with a diffuse mirror and explored the effect of matrix's index of refraction on optical efficiency. Of all systems investigated, a single matrix wedge-shaped diffuse solar concentrator with low refractive index mismatch (n = 1.14–1.18) achieved up to a 34% increase in optical efficiency at polar angles relevant to vertical BIPV applications, resulting from a higher fraction of incoming light traveling straight to the PV.