Development of a New Dynamic Test Method to Determine the Wind Pressure Resistance of Photovoltaic Roof Assembly (PVRA)

摘要

Commercial rooftops provide extensive areas that represent the ideal platform to install a photovoltaic (PV) system. The combination of the roofing assembly and the PV system is termed a photovoltaic roofing assembly (PVRA). There was little guidance for determining the wind loads on rooftop PV systems for many years. With the efforts of the Structural Engineers Association of California and numerous wind tunnel studies conducted by reputed labs, the design methodology for determining wind loads on PV systems has been established, which has become ASCE 7-16, Minimum Design Loads for Buildings and Other Structures, and the National Building Code of Canada 2015. However, there is no guidance on the resistance aspect of the PVRA. During the life cycle of the rooftop solar array, the variable amplitude of the dynamic wind loading can lead to fatigue, which can accumulate damage in structure details. Such damages might lead to severe failures in the whole PVRA. Currently, there are no standardized test methods that determine the collective performance of a PVRA. In collaboration with the roofing and solar industry, the National Research Council Canada (NRC) is conducting a research study to address the missing link between the design and resistance of a PVRA. A unique, dynamic test method was developed to determine the wind pressure resistance of a PVRA. The test methodology applies uniform wind pressure on a 3 x 3 array. It provides a complete load path evaluating the capacity in members, connections, and PV attachments to the roof assembly. The current paper presents the PVRA test apparatus commissioning process. It details the experimental apparatus, the definition of the testing specimen, the establishment of a dynamic loading protocol, and quantification (measurements) of the system response. It also presents the results of pilot testing conducted as per the new test method. Once standardized, this new protocol will ensure that PVRA integrity is maintained and PV performance is optimized.