Numerical Study on the Early Out-of-Plane Mechanical Response of Glass–Glass Building-Integrated Photovoltaics Exposed to Increasing Temperature and Fire

Glass–glass photovoltaic (PV) technologies for building-integrated PV (BIPV) applications are increasingly used in construction, for many positive aspects. These multi-functional systems are rather complex to characterize and need the technical knowledge of many experts due to the combination of electrical, mechanical, and architectural needs. Structurally speaking, glass–glass BIPVs are in fact required to withstand possible superimposed thermal and mechanical loads under normal operational conditions, as well as in accidental scenarios. As such, the impact of their geometrical features and mechanical details on their overall performance is a key issue in safety assessments. Glass cracking, for example, represents a critical condition, but additional important phenomena can take place before fracture. In this paper, attention is paid to the elaboration of thermal and mechanical considerations for glass–glass BIPVs under increasing temperatures. For comparative purposes, a 400 × 400 mm tempered prototype is investigated. Based on a robust Finite Element (FE) numerical approach, the present study investigates some important thermo-mechanical mechanisms of the first heating stage (i.e., ≈150–250 s of exposure, for the examined configurations), before glass cracks. It is shown that—even in the elastic stage before glass cracking—important modifications of temperature-dependent materials can reduce the load-bearing capacity of the examined BIPV systems. Also, variations in cross-sectional composition (i.e., thickness of glass covers) and/or in the mechanical restraints (4L, 2L, and 4P, in the following) can have significant, critical impacts on the reference performance indicators, such as the global bending stiffness, the stress evolution and peaks in the BIPV components, and the deflection.