Progress on the National Solar Radiation Data Base (NSRDB): A New DNI Computation

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3 Scopus Citations


This study introduces a new technique to compute direct normal irradiance (DNI) for improving the National Solar Radiation Data Base (NSRDB). A finite-surface integration algorithm is developed to compute solar radiation in differential solid angles and efficiently infer its contribution to a surface perpendicular to the solar direction. A lookup table of cloud bi-directional transmittance distribution function (BTDF) is developed by use of the discrete ordinates radiative transfer (DISORT) model for possible solar and observing directions and various cloud optical and microphysical properties. In each solar incident direction, DNI is given by the cloud BTDFs from approximately 200 differential solid angles. The simulated DNI is calibrated and evaluated using surface observations at the National Renewable Energy Laboratory's (NREL's) Solar Energy Research Laboratory (SRRL) and the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) facility.

Original languageAmerican English
Number of pages3
StatePublished - 14 Jun 2020
Event47th IEEE Photovoltaic Specialists Conference, PVSC 2020 - Calgary, Canada
Duration: 15 Jun 202021 Aug 2020


Conference47th IEEE Photovoltaic Specialists Conference, PVSC 2020

Bibliographical note

See NREL/CP-5D00-75911 for preprint

NREL Publication Number

  • NREL/CP-5D00-79318


  • direct normal irradiance
  • DNI
  • National Solar Radiation Database


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