Reduction of uncertainties for photovoltaic reference cells

This paper presents the latest implementation of the ESTI reference cell set at the European Solar Test Installation. The set consists of five photovoltaic reference cells used to measure solar irradiance. Each cell has been calibrated multiple times by primary methods. The stability of the set has been maintained and monitored over a long term (up to 20 years). Taken together this allowed a rigorous determination of the assigned calibration value for each cell based on the weighted average, together with its uncertainty. This has led to unprecedented low uncertainties of 0.23% (k=2), which are at least a factor of two smaller than achievable with any single primary calibration. Using these cells for calibrating secondary reference with a dedicated set-up leads to uncertainties for these secondary calibrated cells which is of the same order as the best primary calibration methods.JRC.F.7-Renewables and Energy Efficienc