Simulation guided design of flexible photovoltaic laminates

Photovoltaic (PV) modules are manufactured using various PV cell technologies. The packaging requirements vary for each of the PV technologies and depend on their inherent thermo-mechanical properties and environmental stability of the cell. Thin film PV has the relative advantage of flexibility vis-à-vis their rigid and brittle competitors. This paper discusses the use of Finite Element Analysis (FEA) to develop a framework for guiding the design of flexible Building Integrated Photovoltaic (BIPV) shingles utilizing thin film PV cells. Microglass (0.2-0.3 mm thick glass) was chosen as the top barrier layer to exploit the flexibility of the thin film PV material. However, microglass alone does not provide sufficient protection to the shingle to meet regulatory impact resistance requirements. This paper discusses the use of FEA to guide the selection of reinforcing polymer layers and their placement around the microglass to enable microglass-based flexible laminates to sustain hail impact. FEA was used to guide the selection of reinforcing polymers and their placement in the laminate structure. Hail impact was modeled as static indentation and stresses were calculated in all layers of the laminate. This model was used to compare around 50 laminates generated through systematic variation of the polymer mechanical properties and laminate designs. Based on the analysis of the stresses generated in the microglass and other layers in these laminates, it is found that the optimal laminate design would consist of an elastomeric reinforcing layer above the microglass and a rigid polymer layer below it. An additional layer of a rigid polymer above the elastomeric layer can further reduce stresses in the laminate; however, relatively large thickness of this layer might be needed to get any significant stress reduction. The ideal location for the rigid reinforcing layer has been identified to be between the cell and the bottom barrier layer. The model predictions have been partially validated through hail impact testing.