Variation in spectral correction of PV module performance based on different precipitable water estimates

The accuracy of two empirical correlations for estimating atmospheric precipitable water (Pwat) based on surface measurements of ambient temperature and relative humidity is evaluated using data from Suominet. Pwat affects the spectral composition of ground measured irradiance. Spectral effects on photovoltaic module performance are often accounted for using a metric called spectral shift (M). The sensitivity of M estimates for both cadmium telluride (CdTe) and monocrystalline-silicon (mono-Si) modules that results from the uncertainty in Pwat measurements is also investigated.