Description
Cell temperature models (e.g. SAPM, PVsyst, Faiman) expect 'poa_global' as input. POA global is the irradiance incident on the module surface (before reflection and not adjusted for spectrum). This is the appropriate input when it is available, since the temperature models are calibrated to irradiance measured in the plane of array with (most likely) a pyranometer.
In many cases, it would be acceptable to use 'effective_irradiance' in place of 'poa_global', because the relative difference between these quantities is small, and the effect on cell temperature of swapping irradiance values is small and acceptable. In some use cases 'effective_irradiance' is available (e.g. when measured with a reference cell) and 'poa_global' is not.
Describe the solution you'd like
It would be helpful for ModelChain to substitute 'effective_irradiance' for 'poa_global' when the latter is not available in data input to e.g. ModelChain.run_model_from_effective_irradiance. Users should be notified of the substitution, and possibly could turn this feature on/off.