Enhancing PV glazing prospects in solar architecture

To make it easier to adopt building integrated PV (BIPV) as a glazing material, a group within the IEA Photovoltaic Power Systems Programme (IEA-PVPS) has tackled the solar heat gain coefficient (SHGC) calculation for BIPV. It is part of IEA PVPS Task 15 international standardization efforts.

The latest report from Task 15, a global project set up to address barriers related to building integrated PV (BIPV) by the IEA Photovoltaic Power Systems Programme (IEA-PVPS), provides an experimentally-based way to determine solar heat gain coefficient (SHGC), also known as “g value”, and how standards can be modified to accommodate the way that it is calculated in BIPV products. 

The SHGC typically quantifies how much incident solar radiation is transmitted, directly or indirectly, through building envelope components and converted into heat. There is a need to modify it for BIPV because PV power generation reduces absorbed solar energy that would otherwise be transferred as heat into indoor spaces.

“Understanding this effect is essential for optimizing energy efficiency in buildings, reducing cooling demand, and supporting the broader adoption of BIPV solutions,” said the Task 15 team.

The report, “Solar Heat Gain Coefficient of BIPV Modules for Electricity-Generating Facades,” presents research on SHGC, a key metric for conventional architectural glazing to calculate building cooling demand. There are two complementary approaches proposed. One relies on adapting an internationally standardized calorimetric measurement of the SHGC, which decreases depending on the PV cell coverage ratio and the thermal properties of the glazing, taking into account what happens when electricity is generated and extracted during the measurement.

The other approach is to calculate the SHGC of the BIPV glazing from the optical and thermal properties of its components and the photovoltaic conversion efficiency of the module. It adapts international standards for conventional glazing to account for typical characteristics of BIPV, such as the optical inhomogeneity caused by the solar cell coverage and electricity generation, according to the team.

Both proposals were the result of pre-normative research by members of Task 15 and were recently published in Energy and Buildings: “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.”

In the meantime, modifications to international standards based on the research results have been proposed and are currently in the public enquiry phase.

“These modifications allow improved comparability and accuracy in SHGC assessment of BIPV glazing units,” said the team.