Annual Solar Irradiance Anomaly Features Over the USA During 1998-2017 Using NSRDB V3: Preprint

Research output: Contribution to conferencePaper


Annual solar irradiance anomalies (or departures from the long-term mean annual value) have a direct effect on various phases of solar energy projects, from prefeasibility to deploy-ment. Anomalies can happen because of normal climate varia-bility or exceptional weather patterns. This study investigates such anomalies for both global horizontal irradiance (GHI) and direct normal irradiance (DNI) using Version 3 of the National Solar Radiation Database (NSRDB V3) and surface irradiance measurements at eight U.S. locations. At each site, the annual anomaly is analyzed here by evaluating the irradi-ance deviation from the long-term average for each specific year during 1998–2017. A positive anomaly indicates that the solar resource was higher than the long-term average during that specific year, and vice versa in the case of a negative anomaly. The results show that, in most cases, the anomaly is within ±5% for GHI and ±10% for DNI, using either ground-based irradiance measurements or modeled data from the NSRDB.
Original languageAmerican English
Number of pages8
StatePublished - 2020
Event47th IEEE Photovoltaic Specialists Conference (PVSC 47) -
Duration: 15 Jun 202021 Aug 2020


Conference47th IEEE Photovoltaic Specialists Conference (PVSC 47)

Bibliographical note

See NREL/CP-5D00-79301 for paper as published in proceedings

NREL Publication Number

  • NREL/CP-5D00-76858


  • anomaly
  • direct normal irradiance
  • DNI
  • GHI
  • global horizontal irradiance
  • photovoltaic
  • PV
  • resource
  • solar radiation


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