The MPPEfficiencyModel for PV has a wrong value for alpha which leads to efficiencies larger than 1. In the cited source [Beyer2004], alpha is 0.45%/°C, thus, it should be 0.0045 and not 0.45.
Also the efficiency can have values smaller than 0 for low values of G. So a max-operator should be added to output value y.
The MPPEfficiencyModel for PV has a wrong value for alpha which leads to efficiencies larger than 1. In the cited source [Beyer2004], alpha is 0.45%/°C, thus, it should be 0.0045 and not 0.45. Also the efficiency can have values smaller than 0 for low values of G. So a max-operator should be added to output value y.