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Technical Briefs

Error Analysis of the Radiative Power Determined From Flux Distributions Measured With a Camera in a Xe Arc Lamp-Based Solar Simulator

[+] Author and Article Information
Ivo Alxneit

 Solar Technology Laboratory, Department General Energy, Paul Scherrer Institute (PSI), CH-5232, Villigen PSI, Switzerlandivo.alxneit@psi.ch

J. Sol. Energy Eng 134(4), 044501 (Oct 04, 2012) (4 pages) doi:10.1115/1.4007493 History: Received November 30, 2011; Revised May 16, 2012; Published October 04, 2012; Online October 04, 2012

The CCD camera-based flux measurement at Paul Scherrer Institute’s (PSI) high flux solar simulator (HFSS) is influenced by a spatially variable spectrum of the concentrated radiation characteristic for arc lamp-based solar simulators. This results in a substantial error in the radiative power determined by integration of the flux distribution. This systematic error is assessed by numerically modeling the response of the CCD camera in use. Measured spectra of concentrated radiation obtained at different points in the flux distribution, measured transmission characteristics of all optical elements, and published data for the spectral sensitivity of the CCD chip are applied in the model. The response of a water calorimeter is used as baseline case. It is shown that the magnitude of the error depends strongly on the region analyzed, i.e., on aperture size, on the wavelength band analyzed, and, unfortunately, also on the number of lamps in operation. A relative error in the range of 10–30% is observed if an aperture with 1 cm in diameter covering the region of peak concentration is considered. It will be shown that the error arises due to the fact that a photon counter (CCD camera) is used to determine the thermal power.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

Grahic Jump Location
Figure 1

Water calorimeter (left) and water-cooled Lambertian target (right) with a flux map superimposed as seen by the CCD camera

Grahic Jump Location
Figure 2

Transmission characteristics of an OD 0.9 neutral density filter (TND) of the camera lens (Tlens) and spectral sensitivity S(λ) of the camera. The effective sensitivity Seff is obtained from Seff=TNDTlensS(λ) after normalization.

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Figure 3

Error analysis for a single lamp in operation. Curves are reported for the two limiting cases (filters centered at 400 nm and 820 nm), best case (filter centered at 900 nm), and camera used at its full spectral bandwidth. (a) Radiative power P intercepted by aperture of radius Ra normalized at Ra=3 cm. (b) Absolute error Eabs=(P-Pref). (c) Relative error (Erel=Eabs/Pref).

Grahic Jump Location
Figure 4

Error analysis for all lamps in operation. Curves are reported for the two limiting cases (filters centered at 400 nm, corresponding to the best case and 820 nm) and camera used at its full spectral bandwidth. (a) Radiative power intercepted by aperture of radius Ra normalized at Ra=3 cm. (b) Absolute error (Eabs=P - Pref). (c) Relative error (Erel=Eabs/Pref).

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