pvfactors
pvfactors is an open-source Python library for modeling diffuse shading and bifacial photovoltaic (PV) irradiance. It implements 2D geometry and view-factor mathematics to account for reflections between array surfaces including front and back sides of bifacial modules, ground, and sky. Used by PV professionals for simulation of complex shading scenarios, time-series irradiance calculations, and energy yield assessment. Maintained under the SunPower GitHub organization.