VALIDATION OF DIRECT BEAM IRRADIANCE MEASUREMENTS FROM ROTATING SHADOWBAND PYRANOMETERS IN A DIFFERENT CLIMATE

Rotating Shadowband Pyranometers (RSPs) are the preferable type of radiation sensors for measurement of direct solar beam irradiance at remote sites where daily maintenance of the instruments is not feasible or practicable. Their primordial lower accuracy due to systematic deviations of the photodiode sensor can be improved significantly with a thorough calibration of each RSP against high precision sensors and application of suitable corrections on the raw data. With corrections derived by DLR, RSP data coincide with the high precision reference measurements within 2 to 3% RMSD for instantaneous direct beam irradiance and meet the annual irradiation sum within 1.5%. This accuracy could be validated and confirmed with a parallel measurement campaign of 6 RSPs in the United Arab Emirates performed by Masdar and CSP Services. The results are presented in this paper.