Intercomparison of two primary reference cell calibration methods

For the first time the ASTM E1125 National Renewable Energy Laboratory (NREL) direct normal and Sandia/NIST standard lamp methods for primary reference cell calibrations will be evaluated by separate external groups. The intercomparison consisting of a set of packaged solar cells with attached temperature sensors will be conducted by NREL, Sandia and Fraunhofer Institute for Solar Energy Systems (ISE). This paper describes in detail variations in the equipment and procedures followed by the three photovoltaic calibration laboratories. Uncertainty estimates by the three laboratories for these reference cell calibration methods are also compared. Differences in the estimated uncertainty can arise because of differing assumptions in the uncertainty in the spectral correction factor, uncertainty in the standard lamp calibration, cavity radiometer calibration, and other random and nonrandom error sources