The measurement principles for terrestrial photovoltaic devices are defined in the IEC60904-3 standard. One
of the main parts of the standard testing conditions (STC) is the spectral distribution of the irradiance known
as AM1.5G spectrum. The definition of these spectral data is based on realistic atmospheric and environment
parameters. These parameters are:
• Tilt of incidence plane to horizontal
• Ground reflectance albedo
• Atmospheric water content
• Atmospheric ozone content
• Turbidity
The software tool used to calculate the standard spectral distribution listed in the IEC60904-3 Ed. 1(1989)
[1] including these atmospheric properties was the BRITE model.
The dataset tabulated in Ed.1 (1989) had several shortcomings:
• It could not be reproduced by the BRITE model
• The solar receiver geometry was not well defined
• The resolution of the data was low with irregular spacing
• The meteorological data applied in the model were inconsistent
• In the tabulated data in Ed.1 (1989) are typographical errors
To overcome these inconsistencies the spectral distribution was revised by the technical committee (TC) 82
of the International Electrotechnical Commission (IEC).
The new IEC60904-3 Ed.2 (2008) [2] has a new meteorological parameter set, higher resolution, a wider
wavelength range in the UV region and is based on an up-to-date SMARTS computer model. Anyone
interested in the data is able to calculate the data by himself [3], otherwise the data are available at the IEC
for purchase.