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Research Papers

Improvement of Radiative Performances of High Temperature Solar Particle Receivers Using Coated Particles and Mixtures

[+] Author and Article Information
Freddy Ordóñez

Processes, Materials and Solar,
Energy Laboratory,
PROMES-CNRS,
7 rue du Four Solaire,
Font-Romeu-Odeillo 66120, France
e-mail: f.ordonez.m@gmail.com

Cyril Caliot

Processes, Materials and Solar,
Energy Laboratory,
PROMES-CNRS,
7 rue du Four Solaire,
Font-Romeu-Odeillo 66120, France
e-mail: cyril.caliot@promes.cnrs.fr

Françoise Bataille

Department of Mathematics,
Florida State University,
1017 Academic Way,
Tallahassee, FL 32306

Guy Lauriat

Laboratoire de Modélisation et Simulation
Multi Echelle,
Université Paris-Est,
MSME UMR 8208 CNRS,
5, Bvd Descartes,
Marne-la-Vallée 77454, France

Contributed by the Solar Energy Division of ASME for publication in the JOURNAL OF SOLAR ENERGY ENGINEERING: INCLUDING WIND ENERGY AND BUILDING ENERGY CONSERVATION. Manuscript received February 5, 2014; final manuscript received September 1, 2014; published online October 8, 2014. Editor: Gilles Flamant.

J. Sol. Energy Eng 137(2), 021009 (Oct 08, 2014) (8 pages) Paper No: SOL-14-1048; doi: 10.1115/1.4028562 History: Received February 05, 2014; Revised September 01, 2014

The use of HfB2, ZrB2, HfC, ZrC, W, and SiC particles in a high temperature solar particle receiver (SPR) is analyzed. The SPR is modeled as a 1D slab of spherical particles dispersion, submitted to a concentrated and collimated solar flux (q0 = 1500 kW/m2). The temperature inside the SPR is taken constant (T = 1300 K), as for a well-stirred receiver. For the W and SiC, the refractive indexes reported in the literature are retained while the real and imaginary parts of the refractive indexes of the others materials are obtained from available reflectance data, using the Kramers–Kronig (KK) relationships. Three SPR configurations are considered: a homogeneous medium with only one kind of particles, a medium with a mixture of two materials and a medium with coated particles. The three configuration results are compared with those obtained using particles made with an ideal material. For the first configuration, the lowest radiative losses are found using small particles of sizes close to d = 2 μm. For the second configuration, non-noticeable improvements are found by the use of mixtures of the studied materials. For the third configuration, when the SiC is used as mantle, the radiative losses decrease to approach the ideal minimum. The best combination corresponds to a particle with a core of W coated by SiC. Improvements of 2.6% and 2.8% may be achieved using coating thickness of 50 nm with particles of d = 2 μm and d = 100 μm, respectively. The use of coated particles may thus lead to significant improvements in the radiative performances of a SPR working at high temperature.

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References

Figures

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Fig. 1

Schematic of a 1D, isothermal, homogeneous SPR

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Fig. 2

Comparison of the spectral radiative losses for the SPR model using the optimized ideal material reported by Ordóñez et al. [10]. MC means Monte Carlo method and TS means two-stream method

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Fig. 3

Normal reflectance for four UHTCs suggested as selective materials to be used in high temperature SPRs. The solar spectrum is shown in the insets (black continuous line). (Reproduced by permission from Sani et al. Copyright 2012 by Sani et al.) [13].

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Fig. 4

Real and imaginary parts of the refractive index (a) and (b) for the hafnium diboride, hafnium carbide, and silicon carbide, (c) and (d) for the zirconium diboride, zirconium carbide, and tungsten

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Fig. 5

Real and imaginary part of the refractive indexes for an ideal material that minimize the radiative losses. In circles obtained with the Lorenz–Mie theory and the PSO algorithm. In continuous line computed from the reflectivity using the KK dispersion relations. In both cases the solar flux is taken as the blackbody emission at 5777 K normalized to q0 = 1500 kW/m2. The temperature profile is constant at T = 1300 K.

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Fig. 6

Normal reflectivity computed from the two computed refractive indexes shown in Fig. 4

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Fig. 7

Radiative losses of a SPR using different mixtures of materials of two sizes: (a) d = 2 μm, (b) d = 100 μm. In both subfigures a mixing ratio of 1 means a 100% SiC medium.

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Fig. 8

Radiative losses of a SPR using coated particles. W and UHTCs are used for the core and SiC for the mantle. In both subfigures, a core/mantle ratio of 1 means that no coating exist.

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Fig. 9

Comparisons of the absorption Mie-efficiency (Qabs) (a), scattering Mie-efficiency (Qsca) (b) and asymmetry factor (g) for W, SiC, and W coated with SiC particles in regard of the optimized ideal material for a particle diameter d = 100 μm

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