We evaluated the durability of a 3D-curved crystalline Si solar module for vehicle integrated photovoltaics (VIPV) installed on the roof of a commercial vehicle by performing practical operation test for 4 years with a driving distance of ~60,000 km on public roads. To achieve aesthetic design together with high power-output expected for the VIPV module, we utilized heterojunction back contact (HBC) crystalline Si (c-Si) solar cells employed a cell shingling structure. Additionally, we used flat braided copper wires as cell-to-cell connector to enhance the reliability of cell-interconnection, aiming to improve durability against 3D-curvature structure and mechanical stress which should be induced during driving. We demonstrated its advantage in resistance to temperature cycling tests for the HBC c-Si solar cells with the cell shingling structure. By applying these technologies to our 3D-curved solar module, we confirmed that it maintained equivalent power-output performance and appearance after the practical operation test.
