Optimization of the building-integrated transparent photovoltaic configuration based on daylight and energy performance in school buildings in the tropics

Introduction: Numerous previous studies addressed the use of vertical facades for side lighting. They were found to be an effective daylighting aperture that helps to establish a pleasant environment, improve academic performance in schools, and promote better health. Recent studies also identified the potential for using vertical facades on high-rise buildings as building-integrated photovoltaic (BIPV) systems thanks to the large available area. In the tropics, this potential use is also supported by the availability of abundant solar energy. The technology of transparent PV (TPV) offers the opportunity to meet both needs. It serves as a side lighting aperture and building-integrated transparent photovoltaic (BITPV) depending on several factors, such as the visible transmittance (VT) value and the number of cells. For side lighting, a higher VT value is required to allow for optimal daylight penetration. However, more cell numbers and lower VT are preferable for BITPV. Previous studies found that BITPV is suggested for buildings with a window-to-wall ratio (WWR) of 45 % or more, which seems too high for tropical buildings where the suggested WWR is typically in the range of 30–40 %. Purpose of the study: This study aims to find the optimum configuration and present a systematic method for optimizing BITPV for tropical school building facades. Methods: An experimental approach using simulation as a tool was employed to achieve the objective. A site with a typical school layout in the tropics was selected as the research context. Treatment based on VT and cell numbers was applied to create several post-test models. Results and discussion: In the tropics, when using low-transparency TPV, BITPV with 31.25 % WWR and 30 % cell coverage ratio is found to provide the optimum visual health and comfort, as well as energy performance. Meanwhile, BITPV with 31.25 % WWR and 50 % cell coverage ratio is found to be the optimum configuration when using high-transparency TPV. Furthermore, this study presents a systematic method for designing BITPV for a multi-story school building in the tropics.