High-efficiency white-light solar window using waveguide glass plate

Abstract

A high-efficiency white-light solar window is proposed for building-integrated photovoltaic (BIPV) applications. In the solar window, incident light is scattered at a waveguide plate and guided into GaAs cell arrays at the edges of the window frame. The optical characteristics of the waveguide plate are designed and evaluated using a ray-tracing simulation, and the solar window is fabricated and assembled with three-dimensional printing. The solar window exhibits an almost constant transmittance, with an average of about 21.6% in the visible range of 400–800 nm and a color rendering index of about 97.8 for sunlight, which is a neutral color that does not distort the colors of indoor objects under sunlight through the window. The solar window achieves a geometric concentration gain of 1.14 and edge collection ratio (ECR) of about 27.0%, which is constantly obtainable regardless of the incident angle of sunlight, and it exhibits an efficiency of 6.368%, a very high value for conventional transparent solar cells and modules. The method for optimizing the window efficiency and effective indoor illuminance by increasing the size of the solar window is also presented. These results can contribute to the further development of high-performance and large-area BIPV windows.