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A group within the International Energy Agency Photovoltaic Power Systems Programme (IEA-PVPS) has developed an experimental approach to determine the solar heat gain coefficient (SHGC) for building-integrated photovoltaic (BIPV) glazing. This is part of their Task 15 effort to standardize BIPV products by addressing the need to modify SHGC calculations for these products.
The SHGC measures how much solar radiation is transmitted through building envelopes and converted into heat. However, BIPV systems, which generate electricity, reduce the amount of solar energy that would otherwise be transferred as heat into buildings. This makes it essential to understand the SHGC in BIPV systems to optimize energy efficiency, reduce cooling demand, and promote the adoption of BIPV solutions.
The Task 15 team has proposed two approaches to calculate SHGC for BIPV glazing. The first method involves adapting the internationally standardized calorimetric measurement of SHGC, taking into account the reduced heat gain due to electricity generation and extraction. The second approach calculates SHGC based on the optical and thermal properties of the glazing components and the photovoltaic conversion efficiency of the module.
The team published their research in two papers, “Component-based SHGC determination of BIPV glazing for product comparison” and “International inter-laboratory comparison of solar heat gain coefficient of building-integrated photovoltaic modules – results of tests with or without power generation and tests with PV cell coverage ratios.” Based on these findings, the team has proposed modifications to international standards, which are currently in the public inquiry phase. These modifications will improve the comparability and accuracy of SHGC assessments for BIPV glazing units.
Overall, the development of a standardized SHGC calculation for BIPV glazing will facilitate the adoption of BIPV solutions by providing a way to measure their energy-generating potential and their impact on building energy efficiency.