Improved precision of the outdoor performance measurements of photovoltaic modules by using the photovoltaic irradiance sensor

•Precise outdoor performance measurement is achieved even under unstable irradiance.•The solar irradiance was measured with a PV module irradiance sensor (PVMS).•The I-V curves were corrected for temperature by a new translation formula.•The present results are useful for improving onsite measurement precision. Highly precise outdoor current-voltage (I-V) curve measurement of crystalline silicon photovoltaic (PV) modules has been achieved, by monitoring the solar irradiance with a PV module irradiance sensor (PVMS), measuring the curves in 0.2–0.5 s, and filtering out the data affected by spatial nonuniformity of irradiance. The I-V curves were corrected for temperature by using a recently developed translation formula. Good reproducibility in the short circuit current ISC, open circuit voltage VOC, and maximum power Pmax measurements was confirmed, based on repeated measurements for one week. Small values of relative standard deviation σ, i.e., 0.1–0.23% and 0.24–0.42% for the ISC/GPVMS and Pmax/GPVMS, respectively, were confirmed even on partially sunny days and cloudy days when the solar irradiance is very unstable. Here, GPVMS denotes the irradiance measured by using a PVMS. The values of σ for various kinds of commercial crystalline silicon modules, including the p-type BSF, p-type PERC, n-type backside contact and silicon heterojunction, were also investigated in longer periods including different seasons of the year, which were 0.1–0.5% and 0.5–1.3% in the irradiance ranges of 0.9–1.1 kW/m2 and 0.3–0.5 kW/m2, respectively. The results have demonstrated that precise outdoor I-V curve measurements are possible in wide range of irradiance under various weather conditions. They are useful for improving the throughput and accuracy of onsite I-V measurements in operation and maintenance. Possible sources of residual measurement error and methods to further improve the precision are also discussed.