Kevin Lee Wasson

Thin specialty glass for reliable thin film PV modules

Glass has long been used for photovoltaic (PV) module covers and thin-film (TF) module substrates and superstrates. These applications typically use float glass of soda-lime-silica composition and thickness ≥ 3.2 mm. Thin specialty glass is being considered as a replacement for substrates and superstrates for dual-glass laminated TF PV modules. This study focuses on module in-service stresses and their impact on mechanical reliability when using thin specialty glass. Substrate and superstrate thicknesses as low as 0.7 mm were analyzed using various support conditions. Hail impact tests were conducted according to IEC 61646 with standard ice balls (25mm diameter at 23 m/sec). Wind and snow loads as described in IEC 61646 were studied by finite element analysis. Reliability analyses were performed using experimental results, modeled stress levels, initial glass strength, and strength decrease over time (fatigue). This study concludes that thin specialty glass is reliable in the variety of configurations analyzed. Wind and snow load stresses increased systematically as glass thickness decreased. However, support structure configuration showed a greater influence on stress and reliability levels than glass thickness. High speed wind tests on full sized laminates with complete support structures provided validation of performance under realistic conditions. Thin specialty glasses are shown to be a reliable option for thin-film photovoltaic module substrates and superstrates.