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Research Papers

Influence of Measurement Equipment on the Uncertainty of Performance Data from Test Loops for Concentrating Solar Collectors

[+] Author and Article Information
Nicole Janotte

Institute of Technical Thermodynamics Solar Research, German Aerospace Center (DLR), 51147 Köln, Germanynicole.janotte@dlr.de

Eckhard Lüpfert, Robert Pitz-Paal

Institute of Technical Thermodynamics Solar Research, German Aerospace Center (DLR), 51147 Köln, Germany

Klaus Pottler

Institute of Technical Thermodynamics Solar Research, Plataforma Solar de Almería (PSA), P.O. Box 39, 04200 Tabernas, Spain

Markus Eck

Institute of Technical Thermodynamics Solar Research, German Aerospace Center (DLR), Pfaffenwaldring 38-40, 70569 Stuttgart, Germany

Eduardo Zarza

Ciemat, Plataforma Solar de Almería (PSA), P.O. Box 22, 04200 Tabernas, Spain

Klaus-Jürgen Riffelmann

 Flagsol GmbH, Agrippinawerft 22, 50678 Köln, Germany

In the special case of fluids with linear HTF characteristics such as cp of Syltherm 800 this can be simplified using the mean fluid temperature Tm and cp(Tm).

Raising the cleanliness value χ to the power of 3/2 would include the assumption of glass envelopes of receivers being soiled to a similar degree as mirrors.

J. Sol. Energy Eng 132(3), 031003 (Jun 04, 2010) (7 pages) doi:10.1115/1.4001476 History: Received September 22, 2008; Revised March 22, 2010; Published June 04, 2010; Online June 04, 2010

Parabolic trough concentrating collectors play a major role in the energy efficiency and economics of concentrating solar power plants. Therefore, existing collector systems are constantly enhanced and new types were developed. Thermal performance testing is one step generally required in the course of their testing and qualification. For outdoor tests of prototypes, a heat transfer fluid loop (single collector or entire loop) needs to be equipped with measurement sensors for inlet, outlet, and ambient temperature as well as irradiance, wind speed, and mass or volumetric flow rate to evaluate the heat balance. Assessing the individual measurement uncertainties and their impact on the combined uncertainty of the desired measurement quantity one obtains the significance of the testing results. The method has been applied to a set of EuroTrough collector tests performed at Plataforma Solar de Almería, Spain. Test results include the uncertainty range of the resulting modeling function and exemplify the effects of sensors and their specifications on the parameters leading to an uncertainty of ±1.7% points for the optical collector efficiency. The measurement uncertainties of direct normal irradiance and mass flow rate are identified as determining uncertainty contributions and indicate room for improvement. Extended multiple sensor deployment and improved calibration procedures are the key to further reducing measurement uncertainty and hence increasing testing significance.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Rectangular distribution (type B)

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Figure 2

Schematic representation of a recommended fitting procedure (7)

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Figure 3

Uncertainty contributions of measured quantities to optical and thermal efficiency results

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Figure 4

Fitting results of the efficiency test data (a) and the 95% probability range for thermal efficiency predictions using the best fit (b), DNI=1000 W/m2, from EuroTrough collector tests at PSA

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