Objectives and results of the PEP´87 round-robin calibration of reference solar cells and modules

An international comparison of calibrations of reference solar cells and PV (photovoltaic) modules was carried out in 1987 to 1989. Results of comprehensive measurements performed on eight reference cells in a single-cell package, six reference cells in a multicell package, and six PV modules are presented. Amorphous Si, monocrystalline Si, and multicrystalline Si technologies were included in the round robin. A pyranometer circulated with the reference cells allowed pyranometer calibration uncertainties to be evaluated. As the standardization of calibration methods and reference devices is desired by the International Electrotechnical Commission, this comparison examined whether the many primary calibration methods evaluated were accurate enough and suitable for wide use. The effects of the definition and packaging of primary reference devices on the achievable uncertainties of the calibration in the chain from cell to module are discussed. The following achievable minimum uncertainties are considered to be realistic and are recommended for primary calibrations: U₉₅=±2% with random error of ±1%