UPDATE OF ALGORITHM TO CORRECT DIRECT NORMAL IRRADIANCE MEASUREMENTS MADE WITH A ROTATING SHADOW BAND PYRANOMETER

摘要

The accuracy and reliability of direct beam solar irradiance data and measurements are of great importance in the development of concentrating solar power technologies. Confirmation of site-specific irradiance levels and seasonal and diurnal patterns with on-site measurements is often required during the process of developing project plans and financing arrangements. The high cost of such measurements with typical high quality thermopile irradiance measurement is often a serious impediment to deployment. This effort was an attempt to improve the accuracy of a lower cost direct beam measurement system. This paper describes corrections to the original correction algorithm first presented at the ASES 2002 conference on the same subject in a paper entitled "Improving the Accuracy of Direct Beam Measurements". These corrections are the result of an extension to the NREL sponsored research project described in that paper and below. That research project was extended to allow additional field measurements and to address a marked inaccuracy in the previously developed correction algorithm over a solar zenith angle range of 75 to 85 degrees. This paper supercedes the original paper.