Assessment of Uncertainty in the Numerical Simulation of Solar Irradiance Over Inclined PV Panels: New Algorithms Using Measurements and Modeling Tools

Yu Xie, Manajit Sengupta, Mike Dooraghi

Research output: Contribution to journalArticlepeer-review

27 Scopus Citations


Development of accurate transposition models to simulate plane-of-array (POA) irradiance from horizontal measurements or simulations is a complex process mainly because of the anisotropic distribution of diffuse solar radiation in the atmosphere. The limited availability of reliable POA measurements at large temporal and spatial scales leads to difficulties in the comprehensive evaluation of transposition models. This paper proposes new algorithms to assess the uncertainty of transposition models using both surface-based observations and modeling tools. We reviewed the analytical derivation of POA irradiance and the approximation of isotropic diffuse radiation that simplifies the computation. Two transposition models are evaluated against the computation by the rigorous analytical solution. We proposed a new algorithm to evaluate transposition models using the clear-sky measurements at the National Renewable Energy Laboratory's (NREL's) Solar Radiation Research Laboratory (SRRL) and a radiative transfer model that integrates diffuse radiances of various sky-viewing angles. We found that the radiative transfer model and a transposition model based on empirical regressions are superior to the isotropic models when compared to measurements. We further compared the radiative transfer model to the transposition models under an extensive range of idealized conditions. Our results suggest that the empirical transposition model has slightly higher cloudy-sky POA irradiance than the radiative transfer model, but performs better than the isotropic models under clear-sky conditions. Significantly smaller POA irradiances computed by the transposition models are observed when the photovoltaics (PV) panel deviates from the azimuthal direction of the sun. The new algorithms developed in the current study have opened the door to a more comprehensive evaluation of transposition models for various atmospheric conditions and solar and PV orientations.

Original languageAmerican English
Pages (from-to)55-64
Number of pages10
JournalSolar Energy
StatePublished - 2018

Bibliographical note

Publisher Copyright:
© 2018 Elsevier Ltd

NREL Publication Number

  • NREL/JA-5D00-66180


  • Model uncertainty
  • POA irradiance
  • Radiative transfer
  • Solar radiation


Dive into the research topics of 'Assessment of Uncertainty in the Numerical Simulation of Solar Irradiance Over Inclined PV Panels: New Algorithms Using Measurements and Modeling Tools'. Together they form a unique fingerprint.

Cite this