A Physics-Based DNI Model Assessing All-Sky Circumsolar Radiation: Article No. 100893

Yu Xie, Manajit Sengupta, Hai Long, Aron Habte, Yangang Liu, Qilong Min, Weijia Liu

Research output: Contribution to journalArticlepeer-review

15 Scopus Citations


By investigating the long-term observations at Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP), we find that the routinely used Beer-Bouguer-Lambert law and the models that empirically separate direct normal irradiance (DNI) from measurements of global horizontal irradiance (GHI) have dramatic and unexpected bias in computing cloudy-sky DNI. This bias has led to tremendous uncertainty in estimating the electricity generation by solar energy conversion systems. To effectively reduce the bias, this study proposes a physical solution of all-sky DNI that computes solar radiation in the infinite-narrow beam along the sun direction and the scattered radiation falls within the circumsolar region. In sharp contrast with the other DNI models, this method uses a finite-surface integration algorithm that computes solar radiation in differential solid angles and efficiently infers its contribution to a surface perpendicular to the sun direction. The new model substantially reduces the uncertainty in DNI by a factor of 2–7.

Original languageAmerican English
Article number100893
Number of pages18
Issue number3
StatePublished - 27 Mar 2020

Bibliographical note

Publisher Copyright:
© 2020 The Author(s)

NREL Publication Number

  • NREL/JA-5D00-74861


  • direct normal irradiance
  • DNI
  • Fast All-sky Radiation Model for Solar applications
  • GHI
  • global horizontal irradiance


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