Spectroradiometer Intercomparison and Impact on Characterizing Photovoltaic Device Performance

Indoor and outdoor testing of photovoltaic (PV) device performance requires the use of solar simulators and natural solar radiation, respectively. This performance characterization requires accurate knowledge of spectral irradiance distribution that is incident on the devices. Spectroradiometers are used to measure the spectral distribution of solar simulators and solar radiation. On September 17, 2013, a global spectral irradiance intercomparison using spectroradiometers was organized by the Solar Radiation Research Laboratory (SRRL) at the National Renewable Energy Laboratory (NREL). 10 spectroradiometers from different laboratories participated in the intercomparison. The intercomparison was aimed to understand the performance of the different spectroradiometers and to achieve internal performance-based measurement and calibration qualitycontrol checks undertaken by the laboratories. The Simple Model of the Atmospheric Radiative Transfer of Sunshine (SMARTS) model outputs were used in the outdoor intercomparison as an explanatory tool. The intent was to better understand how well the SMARTS-modeled spectra compare to various types of spectroradiometers considering that the model has a finer resolution than the instruments under scrutiny. Aside from spectral regions corresponding to sharp absorption bands and fast-changing sky conditions, the overall results of the comparison demonstrated less than 10% difference among the participating spectroradiometers and between the measured and SMARTS outputs. The results of this first intercomparison will help to decrease systematic inter-laboratory differences in the measurements of the outputs or efficiencies of PV devices and harmonize laboratory experimental procedures.