Outdoor meteorological broadband and spectral conditions for evaluating photovoltaic modules

The choice of conditions that should be used for rating photovoltaic modules is revisited to assess how well they represent the real world. One part of this study looks at the meteorological conditions and broadband characteristics of the irradiance when the global irradiance is 1000 W/m(2). Global normal irradiance on a 2-axis-tracked surface of 1000 W/m(2) was found to be correlated with a direct normal irradiance of 836 W/m(2), an ambient temperature of 23.7 degrees C, a wind speed of 4.5 m/s, a total water vapor of 1.4 cm, an aerosol optical depth of 0.08, and an air mass of 1.43. The second part of the study investigates the direct normal spectra that are commonly observed and concludes that of the two reference spectra that are commonly used, the global 37 degrees tilt reference spectrum (ASTM #E892) better represents observed data. Spectral modeling identifies a set of conditions for which the direct normal spectrum is very similar to ASTM #E892.