BIPV shading estimation methods key for uptake, says IEA-PVPS

The International Energy Agency Photovoltaic Power Systems Programme (IEA-PVPS) Task 15 has conducted a global survey on BIPV design workflows and methods. The team surveyed 80 professionals from 10 professional groups involved in BIPV, including architects, engineers, researchers, PV installers, and property developers, across the globe.

The survey identified methods, approaches, and workflows in BIPV design and analysis under four key areas: solar irradiation, BIPV power output, building performance, and financial and design outcome.

It found that “there’s a lack of awareness among the respondents on the methods and models used to estimate [plane of array], power output, embodied emissions, heat island impact, thermal, daylighting, structural and fire requirements of BIPV projects,” the authors wrote.

With respect to shading, the survey revealed that more than 25% of respondents are unsure of what’s the most suitable method for estimating shading in BIPV projects. The ray-tracking approach was chosen by the largest cohort of professionals, followed by the shading percentage method, and then the far-field shading horizon map tool.

“To do that work right, we need better building design tools,” Rebecca Yang, associate professor at RMIT University in Melbourne and co-author of the report, told pv magazine.

Existing building design tools currently use suboptimal shading estimation methods, Yang said.

First, these tools often lack many PV products in their database, resulting in calculations using inaccurate parameters. Second, the shading estimates are usually done for large surfaces of the building and over a short time interval, rather than at the individual panel level over a long time period. The reason, according to Yang, is that the latter calculations would be very time-consuming and take a large amount of computing power.

BIPV professionals may also lack the technical knowledge to work with the existing tools, according to Yang. Information on how to use these tools is also often not readily available.

“A lot of firms don’t use complex building design software, which makes the simulation very conceptual and high level, and cannot provide very detailed simulations,” she said.

The IEA-PVPS report concluded that research and development into the most suitable methods for BIPV shading estimation, among many others, is required to improve its uptake.

“Due to the cross-functional nature of BIPV as a building material and an electro-technical device, there’s a need to improve the knowledge and awareness of both the [architecture, engineering, and construction] industry and BIPV industry professionals on the BIPV design and analysis methods and workflow,” the authors said.