Review of physical vapor deposited (PVD) spectrally selective coatings for mid- and high-temperature solar thermal applications

Selvakumar, N.; Barshilia, Harish C.

doi:10.1016/j.solmat.2011.10.028

Cited by 571 publications

(257 citation statements)

References 194 publications

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“…For temperatures in the range of 100-300 °C convective losses become more important, but can be eliminated through the use of an evacuated transparent enclosure as mentioned earlier (Bermel et al, 2012;Mills, 2004). Using highly transparent enclosures and wavelength selective absorbers (surfaces with high absorptance in the solar spectrum but low emittance in the infrared (IR) spectrum) can lead to high efficiencies for these operating temperatures (Hiller et al, 2002;Selvakumar and Barshilia, 2012). For higher temperatures radiative losses dominate due to the fourth power dependence on absorber temperature and good efficiencies are typically achieved through the use of optical concentration, sometimes in combination with vacuum enclosures, wavelength selective surfaces, or other strategies (Fernández-García et al, 2010;Mills, 2004).…”

Section: Introductionmentioning

confidence: 99%

“…This can be achieved with photonic crystals (Hamam et al, 2011;Shen et al, 2014), grooved surfaces (Hollands, 1963;Perlmutter and Howell, 1963), and optical cavities (Braun et al, 2013;Gordon et al, 2004;Luque and Araújo, 1990). Using photonic crystals for solar thermal applications can be problematic as elemental diffusion between layers at high temperatures can ruin their radiative properties (Selvakumar and Barshilia, 2012). Adding grooves to a surface greatly increases the surface area, increasing radiative losses and making grooved surface absorbers non-ideal for solar receivers in practice.…”

Section: Introductionmentioning

confidence: 99%

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Optical cavity for improved performance of solar receivers in solar-thermal systems

et al. 2014

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Abstract:A principal loss mechanism for solar receivers in solar-thermal systems is radiation from the absorbing surface. This loss can be reduced by using the concept of directional selectivity in which radiation is suppressed at angles larger than the incident angle of the sunlight striking the absorber. Directional selectivity can achieve efficiencies similar to high solar concentration, without the drawbacks associated with large heat fluxes. A specularly reflective hemispherical cavity placed over the absorber can reflect emitted radiation back to the absorber, effectively suppressing emission losses. An aperture in the cavity will still allow sunlight to reach the absorber surface when used with point focus concentrating systems. In this paper the reduction in radiative losses through the use of a hemispherical cavity is predicted using ray tracing simulations, and the effects of cavity size and absorber alignment are investigated. Simulated results are validated with proof of concept experiments that show reductions in radiative losses of more than 75% from a near blackbody absorber surface. The demonstrated cavity system is shown to be capable of achieving receiver efficiencies comparable to idealized spectrally selective absorbers across a wide range of operating temperatures. Highlights:-A specularly reflective cavity placed over a solar absorber reduces radiative losses -Cavity performance is sensitive to cavity size and cavity-absorber alignment -Radiative loss reduction validated with proof of concept experiments -Losses from near blackbody absorber reduced by over 75% -Receiver efficiency shown to be comparable to idealized wavelength selective absorber

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Optical cavity for improved performance of solar receivers in solar-thermal systems

et al. 2014

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“…These α values of the Ni-Al coatings are larger than those of Ni-5Al solar absorbers and related coatings such as Ni-25 graphite and WC-25 Ni prepared by the thermal spray technique without heat treatment for 6 h at 600 °C [10]. However, the α of this coating is relatively lower than those of commercial solar selective coatings that are prepared using advanced coating technology under vacuum conditions (sputtering, vacuum evaporation, chemical vapor deposition, and pulsed laser deposition) for the high operating temperature of solar thermal applications [5,6]. Figure 5b shows the spectral R in the wavelength ranges of the IR region.…”

Section: Resultsmentioning

confidence: 99%

“…All the collected radiation is then converted into thermal energy [2,3]. One important task is the development of a solar selective absorber to achieve high solar absorptance (α) or low reflectance (R) over the whole range of the solar spectrum (300-2500 nm) and low emittance (ε) of long wavelength infrared (IR) radiation at 2.5-20 μm [4][5][6].…”

Section: Introductionmentioning

confidence: 99%

Influence of Ni–Al coating thickness on spectral selectivity and thermal performance of parabolic trough collector

Suriwong

Bunmephiphit

Wamae

et al. 2018

Mater Renew Sustain Energy

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This study investigates the influence of Ni-Al coating thickness on the spectral selectivity and thermal performance of a parabolic trough collector (PTC). Three thicknesses of Ni-Al coating for use as solar absorber material were successfully prepared on the outer surface of a stainless steel 316L (SS) tube by flame spray. The phase, morphology, and reflectance (R) of the Ni-Al coatings were characterized using several techniques. The PTC and solar receiver tube were specially designed and constructed for observing the collector thermal performance by following ASHRAE . Looking at the results, the actual average thicknesses of the three Ni-Al coatings turn out to be 195, 215, and 299 μm. The morphology and chemical composition of all three thicknesses are similar. The chemical composition in the cross-sectional view exhibits non-uniform distribution. The three thicknesses of the coating are composed of NiO and Al 2 O 3 phases, which also corresponded to the results of SEM-EDX mapping. The differences in a solar absorptance (α) of the three thicknesses of Ni-Al coating are not statistically significant, with an average α value of 0.74-0.75. However, there are differences in thermal efficiency of the PTC depending on the thickness of the Ni-Al coating. Of the three samples, the thickest one (299 µm) demonstrates the highest ability to convert solar radiation into thermal energy.

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“…Uma dessas técnicas, utilizadas comercialmente, é a eletrodeposição, que quando aplicada para a produção de revestimentos a base de cromo negro apresenta algumas vantagens em relação as demais, tais como a estabilidade térmica (400°C no vácuo e 350°C no ar), baixa emissividade (0,03-0,10) e alta absortância (0,97) (KENNEDY, 2002;SELVAKUMAR;BARSHILIA, 2012).…”

Section: Introductionunclassified

Avaliação Da Interferência Dos Parâmetros De Eletrodeposição Nos Níveis De Absorção De Superfícies Seletivas

Medeiros¹,

Neto²,

Leite³

et al. 2017

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Review of physical vapor deposited (PVD) spectrally selective coatings for mid- and high-temperature solar thermal applications

Cited by 571 publications

References 194 publications

Optical cavity for improved performance of solar receivers in solar-thermal systems

Optical cavity for improved performance of solar receivers in solar-thermal systems

Influence of Ni–Al coating thickness on spectral selectivity and thermal performance of parabolic trough collector

Avaliação Da Interferência Dos Parâmetros De Eletrodeposição Nos Níveis De Absorção De Superfícies Seletivas

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