The Absorptance of Selective Solar Absorber Working in High Vacuum

Russo, R.; Monti, Matteo; D’Alessandro, Carmine; Maio, Davide De; Musto, Marilena; Koral, Can; Andreone, A.; Giamberardino, Francesco Di; Palmieri, V.G.

doi:10.1049/cp.2018.1665

Cited by 6 publications

(9 citation statements)

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“…where, τ Glass is the glass transmittance and Sub is the equivalent emissivity relative to the absorber back side and the vessel and it is assumed to be temperature independent. For Mirotherm R , a previous work [22] has shown that Sub =0.045 provides an excellent fit to experimental data; it is in agreement with the spectrally averaged emissivity calculate by FTIR measurement. We can validate eq.…”

Section: Resultssupporting

confidence: 86%

“…We can validate eq. 5 using an experimental setup [22,38] which allows to evaluate the overall efficiency of the absorber by performing stagnation temperature measurements in high vacuum. The experimental set-up, named Mini-Test-Box (MTB), consists of a stainless steel high-vacuum chamber, closed in the upper side by an extra-clear float glass, which can host a flat absorber suspended by four springs of negligible thermal conductivity.…”

Section: Resultsmentioning

confidence: 99%

“…The core component in a solar thermal collector is the Selective Solar Absorber (SSA). The idea was first introduced at the end of '50, and since then, several works have been devoted to study and to optimize SSA [9][10][11][12][13][14][15][16][17][18][19][20][21][22]. The ideal SSA should efficiently absorb solar radiation (solar absorptance α=1), whereas its thermal emission should be minimal (emissivity =0).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Efficiency of Selective Solar Absorber in High Vacuum Flat Solar Thermal Panels: The Role of Emissivity and Cut-Off Wavelength

Maio¹,

D’Alessandro²,

Caldarelli³

et al. 2020

Preprint

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A multilayer structure on a metallic substrate has been optically simulated and the optimization procedure aimed at obtaining Selective Solar Absorber (SSA) is discussed. This study refers to flat high vacuum thermal collectors and the overall Sun-to-thermal conversion efficiency has been evaluated using analytical formula and numerical thermal model. Both methods are in agreement and they have been validated using experimental results on a commercial absorber. The importance of a low emittance value to obtain high thermal efficiency at high temperatures and high stagnation temperature in selective solar absorber is highlighted. Optimized absorbers can be 8% more efficient than the commercial alternative at 250 °C operating temperatures and up to 27% more efficient at 300 °C. A stagnation temperature higher than 400 °C can be reached without Sun concentration if the proper design is adopted.

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Section: Resultssupporting

confidence: 86%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Efficiency of Selective Solar Absorber in High Vacuum Flat Solar Thermal Panels: The Role of Emissivity and Cut-Off Wavelength

Maio¹,

D’Alessandro²,

Caldarelli³

et al. 2020

Preprint

View full text Add to dashboard Cite

show abstract

“…where τ Glass is the glass transmittance, and ε Sub is the equivalent thermal emittance relative to the absorber back-side and the vessel and it is assumed to be temperature independent. For Mirotherm R , a previous work [31] has shown that ε Sub =0.045 provides an excellent fit to experimental data; it is in agreement with the spectrally averaged emissivity calculated by Fourier-transform infrared spectroscopy (FTIR) measurement. We validated eq.…”

Section: Resultssupporting

confidence: 85%

“…We validated eq. 2 by using an home-made experimental setup, the so called Mini-Test-Box (MTB) [31,32], which allows to evaluate the overall efficiency of the absorber by performing stagnation temperature measurements in high vacuum (see Material and Methods section for further details). Fig.…”

Section: Resultsmentioning

confidence: 99%

Efficiency of Selective Solar Absorber in High Vacuum Flat Solar Thermal Panels: The Role of Emissivity

Maio¹,

D’Alessandro²,

Caldarelli³

et al. 2020

Preprint

View full text Add to dashboard Cite

This study refers to the optimization of a Selective Solar Absorber to improve the Sun-to-thermal conversion efficiency at mid temperatures in high vacuum flat thermal collectors. Efficiency has been evaluated by using analytical formula and a numerical thermal model. Both results have been experimentally validated using a commercial absorber in a custom experimental set-up. The optimization procedure aimed at obtaining Selective Solar Absorber is presented and discussed in the case of a metal dielectric multilayer based on Cr2O3 and Ti. The importance of adopting a real spectral emissivity curve to estimate high thermal efficiency at high temperatures in selective solar absorber is outlined. Optimized absorber multilayers can be 8% more efficient than the commercial alternative at 250 °C operating temperatures and up to 27% more efficient at 300 °C. Once the multilayer has been optimized the choice of a very low emissivity substrate such as copper allows to further improve efficiency and to reach stagnation temperature higher than 400 °C without Sun concentration.

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Characterization and thermal aging tests of Cr based multilayer for unconcentrated solar thermal applications

et al. 2021

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The Absorptance of Selective Solar Absorber Working in High Vacuum

Cited by 6 publications

References 0 publications

Efficiency of Selective Solar Absorber in High Vacuum Flat Solar Thermal Panels: The Role of Emissivity and Cut-Off Wavelength

Efficiency of Selective Solar Absorber in High Vacuum Flat Solar Thermal Panels: The Role of Emissivity and Cut-Off Wavelength

Efficiency of Selective Solar Absorber in High Vacuum Flat Solar Thermal Panels: The Role of Emissivity

Characterization and thermal aging tests of Cr based multilayer for unconcentrated solar thermal applications

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