Understanding the performance of bifacial PV windows with integrated blinds

Abstract

This research investigates the performance of a novel building-integrated photovoltaic (BIPV) window solution equipped with bifacial photovoltaic (bPV) cells and reflective Venetian blinds through a PV modelling approach. By modelling this PV window solution in BIGEYE, the study aims to evaluate how different types of blinds and tilt angles can help to boost the overall performance of the bPV window and to quantify the potential energy gains under varying weather conditions. First, the optical model was validated against experimental data to ensure it could accurately simulate the irradiance received at the front side of the window plane. The optical properties of the Venetian blinds were also defined to quantify the irradiance gain at the rear side of the bPV window. Then, the electrical model was also validated to make sure the model could accurately simulate the electrical behavior of the bPV window demonstrators in real operational conditions. The validated models were then used to test the effect of using different blind configurations in the bPV window’s performance.

In this way, three different types of Venetian blinds were tested: S157 (grey colored), S102 (white colored) and V95 (silver colored). The analysis revealed that, when deployed at a tilt angle of 60°, these types of blinds can help to boost the irradiance gain at the rear side of the bPV window by up to 16%, 20% and 25%, respectively, on a fully sunny day. The study also demonstrated that blinds positioned at 60° consistently achieved the greatest absolute boost in temperature-corrected performance ratio (TCPR) of the bPV window over a typical meteorological year (TMY) in Eindhoven, The Netherlands. In this way, the V95 blind type at a tilt angle of 60° demonstrated to be the optimal blind configuration for boosting the performance of this bPV window. Furthermore, an in-depth analysis was conducted to examine the influence of additional factors on the performance of this bPV window, such as the angle of incidence (AOI) between the sun and the blinds' surface normal, which showed to have an inverse correlation with the bPV window’s TCPR, highlighting that the performance of the window tends to decrease as this AOI increases.
Furthermore, the study quantified the Yearly Specific Yield (YSY) boost achievable with the optimal blind configuration, finding that a maximum boost of 19% can be attained on a TMY in Eindhoven, 18% in Stockholm, and 17% in Valencia. The difference in performance across locations is attributed to variations in meteorological and geographical factors, such as diffuse fraction and AOI. Overall, the findings provide valuable insights into how different blind configurations can enhance the performance of this bPV window and contribute to enhance the energy performance of high-rise residential towers and office buildings.