Repetitive wind load

Repetitive wind load is the cyclic mechanical stress that outdoor wind puts on modules and their mounting during operation. Together with thermomechanical stress, it fatigues cell interconnections, typically where manufacturing weaknesses such as poor soldering or misplaced ribbons already exist, and so drives cell interconnection failure. The joint between the busbars and the string interconnect ribbon is even more prone to this fatigue than the other interconnections. Storm winds that load modules with repeated, uneven pressure can fracture cells, which is a major cause of hotspots, and cracks from wind-driven deflection can electrically isolate parts of cells and cost power. Wind loads that repeatedly exceed the allowable stress of the mounting hardware can permanently deform fasteners and support structures, and fretting can loosen bolts during wind events. High winds can also loosen cables and cause fretting inside connectors, which lets moisture in and leads to corrosion, high resistance and eventually failure. Exposure is highest near the coast and in regions prone to storms and typhoons. To reduce exposure, size structural members and connectors for cyclic wind loads, use locking nuts with specified bolt torques, choose racking built to withstand repetitive and dynamic wind loading, and fasten cables to the racking.

<!-- review notes

• sentence 1: support check: partial - Passages mention repetitive wind load from the outdoor operating environment as a stress on interconnections, but don't define it as cyclic stress on modules and their mounting.
• sentence 7: support check: partial - The passage lists high wind load near the coast and storms/typhoons in storm-prone regions as stressors, but doesn't say exposure is highest there. -->