Improvement of accuracy and precision of spectral irradiance measurements in annual spectroradiometer intercomparison, 35th EUPVSEC, Sept 2018, Brussels, Belgium

Energy yield measurement and radiation yield determination in the field of photovoltaics (PV) are subject to fast development regarding estimation uncertainties and error in prediction [1]. Both are determined mainly by constraints given by equipment development, calibration schemes and operation routines. Further, an increasing range of PV technologies is available on the market showing rather different spectral responsivities. These require precise PV device calibrations, either outdoor or indoor, with accurate measurement of the light-source. Under these boundary conditions accurate spectrally resolved solar irradiance measurements are gaining higher importance compared to recent years. Finally also PV energy yield estimations (predictions) may benefit from more accurate information on the solar spectrum.
The International Spectroradiometer and Broadband intercomparison (ISRC) is evaluating measurement devices, measurement routine and equivalence in measurement results. Last year edition involved 9 scientific institutions and 5 commercial partners of 8 countries, testingmeasurement capabilities and best practices in spectrally resolved solar irradiance between 300 nm and 1700 nm. This work compares results and best practice approaches during the recent years of intercomparison. Capability of precision improvements in measurement as well as deviation in measurement approaches, instruments and institutes are highlighted. The analysis aims to conclude on effects of harmonization efforts, spreading of best-practice measurement routines and discussions on certain aspects such as temperature control or traceability of calibration.