Nonuniform Snow Distribution Mechanism and Load Modeling for Photovoltaic Modules in Cold Regions

Abstract As photovoltaic (PV) systems expand into high-latitude regions, snow loads have become a critical factor affecting both structural safety and energy efficiency. Existing design codes, which are derived from traditional single-slope roof methods, do not fully account for snow retention caused by module frame obstruction or wind-induced nonuniform snow deposition, potentially leading to underestimated design loads. This study combines field observations and numerical simulations to investigate snow accumulation patterns on PV modules under both calm and windblown conditions. The results show that under calm conditions, the frame-induced snow retention remains significant even at a 50° tilt angle, with nondimensional snow depth reaching approximately 0.6, which is much higher than the value specified in the Chinese load code but consistent with that in the US code for warm roofs with obstructions. Under wind action, panels with low tilt angles experience relatively uniform erosion, whereas panels with medium and high tilt angles develop pronounced nonuniform accumulation characterized by thickening at the lower edge and thinning at the upper edge due to flow separation and vortex formation. For large-span module arrays, quasi-two-dimensional flow enhances this nonuniformity, aligning with observed localized structural failures in practice. Wind speed governs redistribution behavior, with moderate speeds producing the most severe nonuniform accumulation and strong winds removing snow entirely. Based on these results, recommended nonuniform snow distribution coefficients of 1.3 and 0.7 are proposed to support PV system design and inform future revisions of snow load standards in cold-region environments.