This paper presents an overview of the World Photovoltaic Scale (WPVS) international reference cell calibration program. The WPVS provides a scale for PV performance measurements that has been established through round-robin calibration of a group of primary reference cells and is traceable to Systeme International (SI) units. Procedures for recalibration of the reference cell group have been devised, along with procedures for admittance and calibration of new reference cells. A reference cell package has been designed that meets the unique needs of the WPVS. It is hoped that the existing WPVS group will eventually be replaced with cells of the new design that have passed an acceptance test procedure

This paper presents the results of an international intercomparison of photovoltaic (PV) performance measurements and calibrations. The intercomparison, which was organized and operated by a group of experts representing national laboratories from across the globe (i.e., the authors of this paper), was accomplished by circulating two sample sets. One set consisted of twenty silicon reference cells that would, hopefully, form the basis of an international PV reference scale. A qualification procedure applied to the calibration results gave average calibration numbers with an overall standard deviation of less than 2% for the entire set. The second set was assembled from a wide range of newer technologies that present unique problems for PV measurements. As might be expected, these results showed much larger differences among laboratories. Methods were then identified that should be used to measure such devices, along with problems to avoid.