Chapter 1: Direct Normal Radiation

Daryl Myers

Research output: Chapter in Book/Report/Conference proceedingChapter


This chapter addresses the quantitative and qualitative aspects of the solar resource, the direct solar radiation. It discusses the total or integrated broadband direct beam extraterrestrial radiation (ETR). This total integrated irradiance is comprised of photons of electromagnetic radiation. The chapter also discusses the impact of the atmosphere and its effect upon the direct normal irradiance (DNI) beam radiation. The gases and particulates present in the atmosphere traversed by the direct beam reflect, absorb, and scatter differing spectral regions and proportions of the direct beam, and act as a variable filter. Knowledge of the available broadband DNI beam radiation resource data is essential in designing a concentrating photovoltaic (CPV) system. Spectral variations in the DNI beam radiation affect the performance of a CPV system depending on the solar cell technology used. The chapter describes propagation and scattering processes of circumsolar radiation (CSR), which includes the Mie scattering from large particles.
Original languageAmerican English
Title of host publicationHandbook of Concentrator Photovoltaic Technology
EditorsC. Algora, I. Rey-Stolle
StatePublished - 2016

NREL Publication Number

  • NREL/CH-5500-66846


  • circumsolar radiation
  • concentrating photovoltaic system
  • direct beam extraterrestrial radiation
  • direct normal irradiance beam radiation
  • electromagnetic radiation
  • Mie scattering


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