International Energy Agency: Enhancing the Prospects of Photovoltaic Glass in BIPV

To promote the wider adoption of Building-Integrated Photovoltaics (BIPV) as a glass material, a team from the International Energy Agency Photovoltaic Power Systems Programme (IEA-PVPS) has addressed the calculation of the solar heat gain coefficient (SHGC) for BIPV. This is part of the IEA PVPS Task 15 international standardization work.

This is a global project aimed at addressing barriers associated with Building-Integrated Photovoltaics (BIPV). The task's latest report provides an experimental method for determining the solar heat gain coefficient (SHGC, also known as the "g-value") and how to modify relevant standards to accommodate the calculation of this coefficient in BIPV products. Further Reading: Green Building Darling: In-depth Analysis of the Heat Transfer Coefficient of Cadmium Telluride Solar Power Glass The solar heat gain coefficient is commonly used to quantify how much incident solar radiation is directly or indirectly converted into heat through building envelope components. Since photovoltaic generation reduces the solar energy that would otherwise be transferred to the interior as heat, adjustments to its calculation method are needed for BIPV. The Task 15 team stated: "Understanding this impact is crucial for optimizing building energy efficiency, reducing cooling demands, and promoting wider adoption of BIPV solutions." The report, titled "Solar Heat Gain Coefficient of Building-Integrated Photovoltaic Modules for Power-Generating Facades," focuses on the solar heat gain coefficient, a key indicator in traditional building glass calculations for building cooling needs. The report proposes two complementary approaches. One approach is to adjust the internationally standardized calorimetric measurement method for the solar heat gain coefficient. The solar heat gain coefficient varies with the photovoltaic cell coverage and the thermal performance of the glass, and the generation and extraction of electricity during measurement must also be considered. The other approach is to calculate the solar heat gain coefficient based on the optical and thermal properties of the BIPV glass component and the photovoltaic conversion efficiency of the component. This method adapts the international standard for traditional glass to accommodate the typical characteristics of BIPV, such as optical non-uniformity caused by solar cell coverage and power generation. These two proposals are the result of normative preliminary research conducted by Task 15 members and recently published in the journal Energy and Buildings: "Component-based determination of the solar heat gain coefficient of BIPV glass for product comparison" and "International interlaboratory comparison of the solar heat gain coefficient of building-integrated photovoltaic modules – results of tests with and without power generation and different photovoltaic cell coverage ratios." Meanwhile, recommendations for modifying international standards based on the research results have been proposed and are currently undergoing public consultation. The team stated: "These modifications improve the comparability and accuracy of the solar heat gain coefficient assessment of BIPV glass units."