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Flux density measurement for industrial-scale solar power towers

Offergeld, Matthias and Röger, Marc and Stadler, Hannes and Hoffschmidt, Bernhard (2014) Flux density measurement for industrial-scale solar power towers. 11th SOLLAB Doctoral Colloquium, 2.-4. März 2015, Melchsee-Frutt, Schweiz.

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For separate acceptance tests of a solar power tower’s heliostat field and receiver, it is necessary to determine the solar flux density distribution over the whole absorber surface. Integrating the flux density delivers the receiver input power, which is required for calculating the energy conversion efficiencies of both heliostat field and receiver. Furthermore, flux density measurement is valuable for supervision and control during operation of a power tower. Flux density at small-scale prototype receivers has mostly been measured by using a camera and a moving bar so far. The moving bar is a white diffusely reflecting target which is moved quickly through the radiation’s focus in front of the receiver surface. At the same time, a digital camera cap-tures the radiation reflected off the moving bar, which allows determining the incident flux density. At industrial-scale receivers though, the installation of a moving bar is hardly feasible due to difficult construction and high costs. Therefore, the development of a measurement method without any mov-ing parts is aspired. For this purpose, the radiation reflected off the absorber itself can be measured in order to calculate the incident flux density [1]. Preliminary work on this method is still immature and has not yet lead to a reliable and satisfying measuring accuracy under all conditions [2]; achieving this is a main aim of the presented thesis. The central challenge with measuring flux density by reflection off the absorber is the absorber’s non-diffusive reflectivity, which depends especially on the direction of the incident radiation as well as on the observation angle [1]. Hence, detailed understanding of reflection at the structured surface of open volumetric receivers as well as tube receivers and following software-aided correction of these effects are essential for reducing the measurement uncertainty. The improvements will be imple-mented and tested at the Solar Tower Jülich. Finally, the improved flux density measurement system is planned to be used in a demonstrational acceptance testing at the Solar Tower Jülich, including a comparison of measurements and simulation results.

Item URL in elib:https://elib.dlr.de/95109/
Document Type:Conference or Workshop Item (Speech)
Title:Flux density measurement for industrial-scale solar power towers
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Offergeld, MatthiasInstitut für SolarforschungUNSPECIFIEDUNSPECIFIED
Date:3 March 2014
Refereed publication:No
Open Access:No
Gold Open Access:No
In ISI Web of Science:No
Keywords:flux density measurements, absorber reflection, acceptance test, heliostat field, receiver, supervision and control during operation,
Event Title:11th SOLLAB Doctoral Colloquium
Event Location:Melchsee-Frutt, Schweiz
Event Type:international Conference
Event Dates:2.-4. März 2015
Organizer:ETH Zürich
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:30 Jun 2015 13:06
Last Modified:30 Jun 2015 13:06

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