Statistical Methods for Monitoring Pyranometer Drift in Solar Radiation Operational Data

The thermopile pyranometer is widely used for solar radiation measurement in photovoltaic (PV) farms. This data is used for the daily operation of the farm, allowing to evaluate the performance of the system. Hence, it is necessary to ensure that the measurements are reliable, and that the sensor is free of drift. This paper presents two statistical methods to identify possible faulty pyranometers, based on the measurements of its neighbors. We demonstrated that both methods detected probable drift and thus can be routinely applied to generate events (alarms), helping operations by guiding the O&M team to inspect and maintain the sensor.