Calibration of photovoltaic reference cells by the global sunlight method

Abstract

The global sunlight method for the calibration of reference photovoltaic cells is described and illustrated with results from recent measurements. In this method, the short circuit current of the solar cell is recorded as it tracks the sun's position. This current, corrected for temperature and total irradiance deviation, is then plotted against pressure-corrected geometric air mass (AM). The calibration value (CV) at standard test conditions (25 °C, 1000 W m−2 total irradiance with AM 1.5 spectral distribution) is extracted by a straight line fit to the data. The global sunlight method is less complex than other methods as it avoids (in particular conditions) the need for spectral irradiance measurements and corresponding relative spectral response determination. It has an estimated expanded uncertainty of 1% and agrees to better than 0.5% with the CVs of the World Photovoltaic Scale.