Vertical bifacial PV systems: irradiance modeling and performance analysis of a lightweight system for flat roofsMari B. Øgaard, Vilde Stueland Nysted, Sigrid Rønneberg, Gaute Otnes, Sean Erik Foss, Trygve Mongstad and Heine N. RiiseEPJ Photovolt., 15 (2024) 13DOI: https://doi.org/10.1051/epjpv/2024012