Articles | Volume 9, issue 4
Atmos. Meas. Tech., 9, 1601–1612, 2016
https://doi.org/10.5194/amt-9-1601-2016
Atmos. Meas. Tech., 9, 1601–1612, 2016
https://doi.org/10.5194/amt-9-1601-2016

Research article 12 Apr 2016

Research article | 12 Apr 2016

Calibration methods for rotating shadowband irradiometers and optimizing the calibration duration

Wilko Jessen1,2, Stefan Wilbert1, Bijan Nouri1, Norbert Geuder3, and Holger Fritz2 Wilko Jessen et al.
  • 1German Aerospace Center, Institute of Solar Research, Qualification/Solar Energy Meteorology, Plataforma Solar de Almería, Carretera de Senés s/n, km 5, 04200 Tabernas, Spain
  • 2Beuth University of Applied Sciences Berlin, Luxemburger Straße 10, 13353 Berlin, Germany
  • 3University of Applied Sciences Stuttgart, Schellingstraße 24, 70174 Stuttgart, Germany

Abstract. Resource assessment for concentrated solar power (CSP) needs accurate direct normal irradiance (DNI) measurements. An option for such measurement campaigns is the use of thoroughly calibrated rotating shadowband irradiometers (RSIs). Calibration of RSIs and Si-sensors is complex because of the inhomogeneous spectral response of these sensors and incorporates the use of several correction functions. One calibration for a given atmospheric condition and air mass might not be suitable under different conditions. This paper covers procedures and requirements of two calibration methods for the calibration of rotating shadowband irradiometers. The necessary duration of acquisition of test measurements is examined with regard to the site-specific conditions at Plataforma Solar de Almería (PSA) in Spain. Seven data sets of long-term test measurements were collected. For each data set, calibration results of varying durations were compared to its respective long-term result. Our findings show that seasonal changes of environmental conditions are causing small but noticeable fluctuation of calibration results. Calibration results within certain periods (i.e. November to January and April to May) show a higher likelihood of deviation. These effects can partially be attenuated by including more measurements from outside these periods.

Consequently, the duration of calibrations at PSA can now be selected depending on the time of year in which measurements commence.

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Short summary
This paper covers procedures and requirements of two calibration methods and examines the necessary duration of acquisition of test measurements. Site-specific seasonal changes of environmental conditions cause small but noticeable fluctuation of calibration results. Calibration results within certain periods show a higher likelihood of deviation. These effects can partially be attenuated by including more measurements from outside these periods.