Component-based SHGC determination of BIPV glazing for product comparison

• Published in: Energy and buildings 2024-10, Vol.320, p.114592, Article 114592
• Main Authors: Wilson, Helen Rose, Kuhn, Tilmann E., Ishii, Hisashi, Valencia-Caballero, Daniel, Martin Chivelet, Nuria, Peng, Jinqing, Yang, Rebecca Jing, Zang, Yukun, Ge, Hua, Ye, Kai, Jonsson, Jacob C., Kapsis, Konstantinos
• Format: Article
• Language: English
• Subjects: BIPV glazing; Electricity extraction; g value; MPP state; OC state; Optical inhomogeneity; PV cell coverage ratio; SHGC; SOLAR ENERGY; Solar Heat Gain Coefficient; Total Solar Energy Transmittance
• ISSN: 0378-7788
• DOI: 10.1016/j.enbuild.2024.114592

•An easily implemented, measurement-based calculation procedure to determine the SHGC of BIPV glazing for product comparison is proposed.•The component-based SHGC procedure for BIPV glazing takes optical inhomogeneity and the extraction of electricity into account.•The adopted area-weighting approach allows the SHGC to be determined for a large variety of dimensions and cell coverage ratios in BIPV glazing from a small set of input data.•The absolute reduction in SHGC due to extraction of electricity is greater for single PV laminates providing relatively little thermal insulation than multiple-pane BIPV glazing units.•SHGC values for BIPV glazing products depend sensitively on the choice of boundary conditions assumed. Building-integrated photovoltaic (BIPV) systems are intrinsically designed to generate electricity and to provide at least one building-related function. When BIPV modules act as glazing products in windows, skylights or curtain walls, their ability to control the transmission of solar energy into the building must be characterised by a Solar Heat Gain Coefficient (SHGC) or g value (also known as Total Solar Energy Transmittance – TSET – or “solar factor”). For the comparison of BIPV glazing products consisting of one PV laminate and possibly further, conventional glazing layers separated by gas-filled cavities, the procedures documented in international standards for architectural glazing (e.g. ISO 9050 and EN 410) form a suitable starting point. Easily implemented modifications to these procedures are proposed to take both optical inhomogeneity (if relevant) and extraction of electricity from BIPV glazing units into account. Geometrically complex glazing and shading devices, and light-scattering glazing layers, are outside the scope of the proposed methodology; SHGC determination for obliquely incident solar radiation is also excluded. For these cases, the experimental calorimetric approach documented in [ISO 19467:2017; ISO 19467-2:2021] is recommended. The paper also presents results and conclusions from an implementation exercise and sensitivity study carried out by participants of the IEA-PVPS Task 15 on BIPV. The cell coverage ratio in the PV laminate, the thermal resistance offered by the glazing configuration, the choice of boundary conditions and the effect of extracting electricity were all identified as parameters which significantly affect the SHGC value determined for a given type of BIPV glazing. A practicable approach to acc