The Increasing Importance of the Substructure for PV Modules Under High Mechanical Loads

Abstract

With the introduction of new cell formats M10, M10R, and especially M12, PV modules have significantly increased in size. The availability of thin tempered glass (<2 mm) has led to a rise in glass-glass modules, which offer a high moisture barrier and minimize cell breakage by placing cells in the neutral axis. However, this increase in size also results in higher weight. To mitigate this, both glass thickness and frame height are being reduced, which brings the mechanical load-bearing capacity of glass and frames into focus. The mechanical stiffness of current frames (28 to 35mm height) is considerably lower than older frames (40mm and above), leading to greater flexibility and deformation under mechanical loads. As material thickness remains typically constant, the strength requirements for components increase. Increased deflection can cause contact between the PV module and substructure at loads significantly below 2,400 Pa (IEC 61215-2 minimum load). While this was not a major concern in the past, module manufacturers now actively exploit it for load approvals. Installers of small PV systems must carefully read installation manuals to understand permissible loads. The situation is even more critical for large systems that utilize bifaciality, as the entire load is transferred through the frame and clamps/screws. Finite element simulations and mechanical load tests demonstrate the importance of using the correct substructure for testing the mechanical load capacity of PV modules and highlight potential interactions. Various module sizes and substructure variants are simulated to compare deformation and stress results.