Alexander Storch, Jan Schindl
Business Unit Renewable Energy
Osterreichisches Forschungs — und Prufzentrum Arsenal GesmbH
Faradaygasse 3, A-1030 Vienna
Phone +43(0)50550-6381; Fax -6390
alexander. storch@arsenal. ac. at

The presented project surveyed the quality of irradiance sensors used for applications in solar systems. By analysing an outdoor measurement, the accuracies of ten commercially available irradiance sensors were evaluated, comparing their results to those of a calibrated Kipp&Zonen pyranometer CM21. Furthermore, as a simple method for improving the quality of the results, for each sensor an irradiance-calibration was carried out and examined for its effectiveness.

Irradiance sensors in thermal solar systems

Irradiance sensors have two major fields of application in thermal solar systems. First, they can provide input parameters for an automated control and supervision of thermal solar systems. For this application, the accuracy of the instantaneous measurements is crucial. The second application is the measurement of sums of irradiation for a monitoring. To meet the rising demand for quality assurance, the monitoring of solar systems is an increasingly requested method for observing the performance and controlling the function of thermal solar facilities. The recorded sums are needed for the calculation of certain characteristic values which are used for the comprehensive rating of the solar systems. To support an increased implementation of monitoring devices, the costs of the measurement equipment has to be kept as low as possible while maintaining a necessary accuracy. Due to their low costs of about a tenth of those of a pyranometer, irradiance sensors are now commonly used in monitoring devices for irradiance measurements. Some of the suppliers guarantee an accuracy of less than 5 % for the annual sum.