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Direct normal irradiance related definitions and applications: The circumsolar issue

Blanc, P. and Espinar, B. and Geuder, Norbert and Gueymard, Christian A. and Meyer, R. and Pitz-Paal, Robert and Reinhardt, Bernhard and Renné, David and Sengupta, M. (2014) Direct normal irradiance related definitions and applications: The circumsolar issue. Solar Energy (110), pp. 561-577. Elsevier. doi: DOI: 10.1016/j.solener.2014.10.001. ISSN 0038-092X.

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Official URL: http://www.sciencedirect.com/science/article/pii/S0038092X14004824


The direct irradiance received on a plane normal to the sun, called direct normal irradiance (DNI), is of particular relevance to concentrated solar technologies, including concentrating solar thermal plants and concentrated photovoltaic systems. Following various standards from the International Organization for Standardization (ISO), the DNI definition is related to the irradiance from a small solid angle of the sky, centered on the position of the sun. Half-angle apertures of pyrheliometers measuring DNI have varied over time, up to ≈10°. The current recommendation of the World Meteorological Organization (WMO) for this half-angle is 2.5°. Solar concentrating collectors have an angular acceptance function that can be significantly narrower, especially for technologies with high concentration ratios. The disagreement between the various interpretations of DNI, from the theoretical definition used in atmospheric physics and radiative transfer modeling to practical definitions corresponding to specific measurements or conversion technologies is significant, especially in the presence of cirrus clouds or large concentration of aerosols. Under such sky conditions, the circumsolar radiation—i.e. the diffuse radiation coming from the vicinity of the sun—contributes significantly to the DNI ground measurement, although some concentrating collectors cannot utilize the bulk of it. These issues have been identified in the EU-funded projects MACC-II (Monitoring Atmospheric Composition and Climate-Interim Implementation) and SFERA (Solar Facilities for the European Research Area), and have been discussed within a panel of international experts in the framework of the Solar Heating and Cooling (SHC) program of the International Energy Agency’s (IEA’s) Task 46 “Solar Resource Assessment and Forecasting”. In accordance with these discussions, the terms of reference related to DNI are specified here. The important role of circumsolar radiation is evidenced, and its potential contribution is evaluated for typical atmospheric conditions. For thorough analysis of performance of concentrating solar systems, it is recommended that, in addition to the conventional DNI related to 2.5° half-angle of today’s pyrheliometers, solar resource data sets also report the sunshape, the circumsolar contribution or the circumsolar ratio (CSR).

Item URL in elib:https://elib.dlr.de/91761/
Document Type:Article
Title:Direct normal irradiance related definitions and applications: The circumsolar issue
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Blanc, P.Mines Paris TechUNSPECIFIED
Espinar, B.Mines Paris TechUNSPECIFIED
Geuder, NorbertStuttgart University of Applied SciencesUNSPECIFIED
Gueymard, Christian A.Solar Consulting Services, New Smyrna Beach, FL, USAUNSPECIFIED
Meyer, R.SuntraceUNSPECIFIED
Pitz-Paal, Robertrobert.pitz-paal (at) dlr.deUNSPECIFIED
Reinhardt, Bernhardbernhard.reinhardt (at) dlr.deUNSPECIFIED
Date:December 2014
Journal or Publication Title:Solar Energy
Refereed publication:Yes
Open Access:Yes
Gold Open Access:No
In ISI Web of Science:Yes
DOI :DOI: 10.1016/j.solener.2014.10.001
Page Range:pp. 561-577
Series Name:El Sevier
Keywords:Direct normal irradiance; Circumsolar irradiance; Circumsolar ratio; Pyrheliometer; Concentrating solar technologies
HGF - Research field:Energy
HGF - Program:Renewable Energies
HGF - Program Themes:Concentrating Solar Systems (old)
DLR - Research area:Energy
DLR - Program:E SF - Solar research
DLR - Research theme (Project):E - Qualification (old)
Location: Köln-Porz
Institutes and Institutions:Institute of Solar Research > Qualifizierung
Deposited By: Kruschinski, Anja
Deposited On:10 Nov 2014 17:07
Last Modified:31 Jul 2019 19:49

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