Gantner Instruments (Juergen Sutterlueti, https://www.gantner-instruments.com/applications/energy/pv-testing-solutions-weather-prospecting/) and Steve Ransome (www.steveransome.com), using outdoor IV measurements on a wide variety of module technologies have developed a PV module performance model based on defining loss factors that affect the shape of the IV curve. Details of this model can be found on publications listed on Ransome’s website.