A smart semi-translucent building-integrated PV module based on integrated-tracking micro-concentration providing high power density and active daylight management

Abstract

Building-integrated photovoltaics (BIPV) can support the green energy transition by enabling building envelopes as solar generators. However, current development rates are insufficient, partly due to the low efficiency of conventional semi-transparent modules and the difficult integration of the high-glare illumination they produce. This work introduces a smart semi-translucent double-glazed BIPV module utilizing concentrator photovoltaics with integrated tracking. The module concentrates direct irradiance on the solar cells to produce electricity and allows transmission of diffuse irradiance to create comfortable daylighting with very low glare, avoiding the need of blinds. Depending on user needs, tracking can be switched to a high-transmission mode, where direct light is deviated from the cells towards the interior of the building to increase daylighting. This concept can be integrated into roof components (e.g., a skylight), façade components (e.g., a curtain wall) or other exterior elements (e.g., solar shading) of buildings. The optical design employs asymmetric linear Fresnel lenses to concentrate light on an array of 2.3 mm-wide solar cells strips (10X). The focal line moves with solar position, so the cell plane is shifted to collect concentrated light using a micro-tracking system. We evaluate optical efficiency, angular tolerance, and daylighting properties using ray-tracing simulations with realistic material and solar properties. A peak efficiency of 76 % is obtained and it is kept above 60 % for transverse angles of incidence beyond 55° when a secondary optical element is added. Furthermore, photorealistic rendering demonstrates the comfortable daylighting (low glare) produced by the module, showcasing its advantages over conventional semi-transparent BIPV.