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Circumsolar Radiation and Beam Irradiance Measurements for Focusing Collectors

Wilbert, Stefan and Pitz-Paal, Robert and Jaus, Joachim (2012) Circumsolar Radiation and Beam Irradiance Measurements for Focusing Collectors. ES1002: Cost Wire Workshop, 22.-23. Mai 2012, Risö.

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Abstract

Depending on the present atmospheric conditions a considerable part of the direct solar radiation can be scattered into the circumsolar region closely surrounding the solar disk. This forward scattered radiation, the circumsolar radiation, is widely detected by pyrheliometers, while concentrating solar collectors can only use a concentrator specific fraction of it. This lower response to circumsoalr radiation can lead to systematic overestimations of the collector performance. when thin clouds mask the sun, this overestimation can be greater than 10% although the direct normal irradiance (DNI) is often above 200 W/M2 in such case. The fraction of the measured DNI that is caused by circumsolar radiation varies depending on the day conditions. The average of this fraction depends also on the location. Thus, representativ site specific information on the circumsolar radiation is necessary for the accurate calcuation of the expected yield of a concentrating solar plant. Beam irradiance data for concentrating solar collectors should be accompanied with information on the circumsolar radiation. However, such information is not available for locations that are now of particular interest for concentrating solar power (CSP) or concentrating photovoltaics (CPV). As a first step to overcome this complication, a reference system consisting of the Sun and Aureole Measurement System (SAM), an Aeronet sun photometer and post processing software has been developed and is used at a small number of sites. In order to provide a sufficient database, an alternative method for the determination of the sunshape is presented using less expensive and maintenance intense equipment. This method makes use of a pair of pyrheliomters with different angular acceptance functions. By comparison of the measurements of the two pyrheliomters, the amount of circumsolar irradiance can be determined. The system was tested and verified using the reference system. As a result, the necessary information for CSP and CPV systems, and a basis for the development of of modeling methods for circumsolar radiation, can now be achieved.

Item URL in elib:https://elib.dlr.de/78602/
Document Type:Conference or Workshop Item (Paper)
Title:Circumsolar Radiation and Beam Irradiance Measurements for Focusing Collectors
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Wilbert, Stefanstefan.wilbert (at) dlr.deUNSPECIFIED
Pitz-Paal, Robertrobert.pitz-paal (at) dlr.deUNSPECIFIED
Jaus, JoachimBlack Photon InstrumentsUNSPECIFIED
Date:22 May 2012
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
Status:Published
Keywords:direct normal irradiance, circumsolar radiation. Sun and Aureole Measurement system, SAM, sunshape
Event Title:ES1002: Cost Wire Workshop
Event Location:Risö
Event Type:Workshop
Event Dates:22.-23. Mai 2012
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 - Qualifizierung (old)
Location: Köln-Porz
Institutes and Institutions:Institute of Solar Research > Qualifizierung
Deposited By: Kruschinski, Anja
Deposited On:06 Dec 2012 17:15
Last Modified:12 Dec 2013 21:51

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