Design, implementation, and testing of a system for calibrating solar energy measuring devices

Abstract

According to ISO 9847, the indoor calibration of pyranometers is based on the use of light filament sources such metal halide and tungsten lamps that are similar to the sun spectrum. The application of LED light sources is currently promoted worldwide in every field. At NIS, a study on the LED pyranometer calibration system was carried out. The results revealed that, in the absence of a diffuser, the uniformity of the FEL lamp and LED source was 0.76 and 0.89, respectively; however, when a diffuser was used, the uniformity increased to 0.92 for the FEL lamp and 0.95 for the LED source. For both systems, the fixed holder’s presence decreased the divergency in repeatability; for the LED source, this was 2%, but for the FEL light, it was 11.5%. In terms of statistical analysis, although the LED calibration system is more stable than the FEL calibration system, none calibration method exhibits any sign of an out-of-control situation, indicating that changes caused by random error are controlled and satisfied. The comparison demonstrated that the filament sources in the pyranometer’s indoor calibration process might be replaced with an LED source.