Evaluating the Sources of Uncertainties in the Measurements from Multiple Pyranometers and Pyrheliometers

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Description

Known and traceable measurement uncertainties in radiometric data are essential for climate model validation, validating satellite-based models for estimating solar resources, and validating solar radiation forecasts. The current state-of-the-art radiometers have uncertainties in the range of 2% to 5% and sometimes higher. The measurement uncertainty depends on the instrument specification, measurement condition, operation and maintenance practices, etc. The National Renewable Energy Laboratory (NREL) and others are identifying and improving radiometric measurement performance and developing consensus methodology for acquiring radiometric data. This study analyzes the impact of differing specifications such as cosine response, thermal offset, spectral response, and others on the accuracy of radiometric data for various radiometers. The results will help users to understand the variations of the radiometric measurements that can result from different radiometer models. The study will also provide insight on how to perform a measurement uncertainty analysis and how to reduce the impact of some of the sources of uncertainties.