Thermal Emittance

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Harish C Arshilia - One of the best experts on this subject based on the ideXlab platform.

  • control of Thermal Emittance of stainless steel using sputtered tungsten thin films for solar Thermal power applications
    Solar Energy Materials and Solar Cells, 2015
    Co-Authors: K P Sibi, Siju Joh, Harish C Arshilia
    Abstract:

    Low infrared (IR) Emittance is the key factor of a solar collector. For high temperature solar Thermal applications, low Emittance is an important parameter, because the Thermal radiative losses of the absorbers increase proportionally by T4. Our primary motivation for carrying out this work has been to lower the IR Emittance of stainless steel substrate (intrinsic Emittance = 0.12-0.13) by coating a thin film of high IR reflecting tungsten (W). Tungsten thin films were deposited on stainless steel substrates using a glow discharge direct current magnetron sputtering system. Emittance as low as 0.03 was obtained by varying the thickness of W coating on stainless steel subsrtae. The influences of structural, morphological and electrical properties of the W coating on its Emittance values are studied. The effect of substrate roughness on the Emittance of W coating is also examined. Thermal stability of the W coatings is studied in both vacuum and air. Solar selective coatings of AlTiN/AlTiON/AlTiO tandem absorber were deposited on W coated stainless steel substrates, which exhibited absorptance of 0.955 and Emittance of 0.08 with a Thermal stability of 600°C in vacuum.

  • review of physical vapor deposited pvd spectrally selective coatings for mid and high temperature solar Thermal applications
    Solar Energy Materials and Solar Cells, 2012
    Co-Authors: N Selvakuma, Harish C Arshilia
    Abstract:

    Abstract Solar energy is the most abundant source of renewable energy. The direct method of harnessing solar energy is the solar Thermal conversion method using solar absorbers. The absorbers are coated with solar selective coatings with high absorptance and low Thermal Emittance. Spectrally selective coatings which are stable up to temperatures ≤300 °C (in air and vacuum) have been developed in the past. These coatings are mainly deposited from wet chemical routes (e.g., electrodeposition) and have been reviewed widely in the literature. Because of the environmental issues as well as low Thermal stability of these wet chemical deposited coatings, researchers all over the world started looking for other alternative routes such as physical vapor deposited (PVD) coatings. A great deal of research has been carried out since 1990s to develop PVD coatings for both mid- and high-temperature applications. The mid-temperature coatings are used mainly for solar hot water and industrial process heat applications, whereas, the high-temperature absorber coatings are used in concentrating solar power systems for solar Thermal power generation. It is well recognized that in order to increase the efficiency of solar Thermal power plants, solar selective coatings with high Thermal stability are required. In recent years, significant efforts have been made in the field of solar selective coatings to achieve high solar absorptance and low Thermal Emittance at higher temperatures ( T ≥400 °C). Transition metal based cermets have emerged as novel high temperature solar selective coatings, which are currently being used for solar Thermal power plants for electricity generation. Solar selective coatings based on transition metal nitrides, oxides and oxynitrides also hold great potential for high-temperature applications because of their excellent mechanical and optical properties, which are yet to be commercialized. In this review, we present the state-of-the-art of the physical vapor deposited solar selective coatings used for solar Thermal applications with an emphasis on sputter deposited coatings for high-temperature applications. A detailed survey, covering the period 1970-present, has been made for the PVD deposited solar selective coatings with high absorptance and low Emittance. This review article also describes in detail about the commercially available PVD coatings for flat-plate/evacuated tube collectors and solar Thermal power generation applications.

E Sani - One of the best experts on this subject based on the ideXlab platform.

  • ultra refractory diboride ceramics for solar plant receivers
    Energy Procedia, 2014
    Co-Authors: Luca Mercatelli, Jeanlouis Sans, E Sani, D Jafrancesco, Paola Sansoni, D Fontani, Marco Meucci, S Coraggia, L Marconi, Eric Eche
    Abstract:

    Abstract Concentrating Solar Power (CSP) is considered to be one of the most promising and sustainable technologies for electricity production in the future, and as efficiency of solar Thermal systems rapidly increases with increasing working temperature, the big challenge for future is to develop novel solutions for solar receivers. In this framework, Ultra-High Temperature Ceramics (UHTCs) are mainly studied as Thermal protection materials for aerospace and military applications, but their peculiar properties (very high melting points and good thermo-mechanical properties at high temperatures) can be advantageously exploited to increase the operating temperature of thermodynamic solar plants in concentrating solar power systems. This work is devoted to the study and characterization of the spectral reflectance of hafnium and zirconium diborides containing MoSi2 as secondary phase in order to evaluate their potential as novel solar absorbers. To assess the spectral selectivity properties, room-temperature hemispherical reflectance spectra were measured from the UV wavelength region to the mid-infrared, considering different levels of porosity for each system, in order to understand how porosity affect spectral reflectance. Moreover, for zirconium diboride and hafnium diboride composites containing 10vol% of MoSi2 sintering aid, the Thermal Emittance was measured in the 1100–1400K temperature range in PROMES-CNRS solar furnace. Data obtained were compared with spectral characteristics and high temperature Emittance of a monolithic silicon carbide.

  • suitability of ultra refractory diboride ceramics as absorbers for solar energy applications
    Solar Energy Materials and Solar Cells, 2013
    Co-Authors: Diletta Sciti, Laura Silvestroni, Luca Mercatelli, Jeanlouis Sans, E Sani
    Abstract:

    Abstract Ultra-refractory diborides are currently studied mainly as Thermal protection materials for aerospace and military applications. However, their favorable properties (very high melting points and good thermo-mechanical properties at high temperatures) can be advantageously exploited to increase the operating temperature of thermodynamic solar plants in concentrating solar power systems. This paper reports on the spectral reflectance characterization of hafnium and zirconium diborides containing MoSi 2 as secondary phase to evaluate their potential as novel solar absorbers. To assess the spectral selectivity properties, room-temperature hemispherical reflectance spectra were measured from the UV wavelength region to the mid-infrared, considering different levels of porosity for each system. Moreover, for zirconium diboride and hafnium diboride composites containing 10 vol% of MoSi 2 sintering aid, the Thermal Emittance was measured in the 1100–1400 K temperature range. Room temperature spectral characteristics and high temperature Emittance were compared to that of a monolithic silicon carbide.

Luca Mercatelli - One of the best experts on this subject based on the ideXlab platform.

  • ultra refractory diboride ceramics for solar plant receivers
    Energy Procedia, 2014
    Co-Authors: Luca Mercatelli, Jeanlouis Sans, E Sani, D Jafrancesco, Paola Sansoni, D Fontani, Marco Meucci, S Coraggia, L Marconi, Eric Eche
    Abstract:

    Abstract Concentrating Solar Power (CSP) is considered to be one of the most promising and sustainable technologies for electricity production in the future, and as efficiency of solar Thermal systems rapidly increases with increasing working temperature, the big challenge for future is to develop novel solutions for solar receivers. In this framework, Ultra-High Temperature Ceramics (UHTCs) are mainly studied as Thermal protection materials for aerospace and military applications, but their peculiar properties (very high melting points and good thermo-mechanical properties at high temperatures) can be advantageously exploited to increase the operating temperature of thermodynamic solar plants in concentrating solar power systems. This work is devoted to the study and characterization of the spectral reflectance of hafnium and zirconium diborides containing MoSi2 as secondary phase in order to evaluate their potential as novel solar absorbers. To assess the spectral selectivity properties, room-temperature hemispherical reflectance spectra were measured from the UV wavelength region to the mid-infrared, considering different levels of porosity for each system, in order to understand how porosity affect spectral reflectance. Moreover, for zirconium diboride and hafnium diboride composites containing 10vol% of MoSi2 sintering aid, the Thermal Emittance was measured in the 1100–1400K temperature range in PROMES-CNRS solar furnace. Data obtained were compared with spectral characteristics and high temperature Emittance of a monolithic silicon carbide.

  • suitability of ultra refractory diboride ceramics as absorbers for solar energy applications
    Solar Energy Materials and Solar Cells, 2013
    Co-Authors: Diletta Sciti, Laura Silvestroni, Luca Mercatelli, Jeanlouis Sans, E Sani
    Abstract:

    Abstract Ultra-refractory diborides are currently studied mainly as Thermal protection materials for aerospace and military applications. However, their favorable properties (very high melting points and good thermo-mechanical properties at high temperatures) can be advantageously exploited to increase the operating temperature of thermodynamic solar plants in concentrating solar power systems. This paper reports on the spectral reflectance characterization of hafnium and zirconium diborides containing MoSi 2 as secondary phase to evaluate their potential as novel solar absorbers. To assess the spectral selectivity properties, room-temperature hemispherical reflectance spectra were measured from the UV wavelength region to the mid-infrared, considering different levels of porosity for each system. Moreover, for zirconium diboride and hafnium diboride composites containing 10 vol% of MoSi 2 sintering aid, the Thermal Emittance was measured in the 1100–1400 K temperature range. Room temperature spectral characteristics and high temperature Emittance were compared to that of a monolithic silicon carbide.

Jeanlouis Sans - One of the best experts on this subject based on the ideXlab platform.

  • ultra refractory diboride ceramics for solar plant receivers
    Energy Procedia, 2014
    Co-Authors: Luca Mercatelli, Jeanlouis Sans, E Sani, D Jafrancesco, Paola Sansoni, D Fontani, Marco Meucci, S Coraggia, L Marconi, Eric Eche
    Abstract:

    Abstract Concentrating Solar Power (CSP) is considered to be one of the most promising and sustainable technologies for electricity production in the future, and as efficiency of solar Thermal systems rapidly increases with increasing working temperature, the big challenge for future is to develop novel solutions for solar receivers. In this framework, Ultra-High Temperature Ceramics (UHTCs) are mainly studied as Thermal protection materials for aerospace and military applications, but their peculiar properties (very high melting points and good thermo-mechanical properties at high temperatures) can be advantageously exploited to increase the operating temperature of thermodynamic solar plants in concentrating solar power systems. This work is devoted to the study and characterization of the spectral reflectance of hafnium and zirconium diborides containing MoSi2 as secondary phase in order to evaluate their potential as novel solar absorbers. To assess the spectral selectivity properties, room-temperature hemispherical reflectance spectra were measured from the UV wavelength region to the mid-infrared, considering different levels of porosity for each system, in order to understand how porosity affect spectral reflectance. Moreover, for zirconium diboride and hafnium diboride composites containing 10vol% of MoSi2 sintering aid, the Thermal Emittance was measured in the 1100–1400K temperature range in PROMES-CNRS solar furnace. Data obtained were compared with spectral characteristics and high temperature Emittance of a monolithic silicon carbide.

  • suitability of ultra refractory diboride ceramics as absorbers for solar energy applications
    Solar Energy Materials and Solar Cells, 2013
    Co-Authors: Diletta Sciti, Laura Silvestroni, Luca Mercatelli, Jeanlouis Sans, E Sani
    Abstract:

    Abstract Ultra-refractory diborides are currently studied mainly as Thermal protection materials for aerospace and military applications. However, their favorable properties (very high melting points and good thermo-mechanical properties at high temperatures) can be advantageously exploited to increase the operating temperature of thermodynamic solar plants in concentrating solar power systems. This paper reports on the spectral reflectance characterization of hafnium and zirconium diborides containing MoSi 2 as secondary phase to evaluate their potential as novel solar absorbers. To assess the spectral selectivity properties, room-temperature hemispherical reflectance spectra were measured from the UV wavelength region to the mid-infrared, considering different levels of porosity for each system. Moreover, for zirconium diboride and hafnium diboride composites containing 10 vol% of MoSi 2 sintering aid, the Thermal Emittance was measured in the 1100–1400 K temperature range. Room temperature spectral characteristics and high temperature Emittance were compared to that of a monolithic silicon carbide.

Eric Eche - One of the best experts on this subject based on the ideXlab platform.

  • ultra refractory diboride ceramics for solar plant receivers
    Energy Procedia, 2014
    Co-Authors: Luca Mercatelli, Jeanlouis Sans, E Sani, D Jafrancesco, Paola Sansoni, D Fontani, Marco Meucci, S Coraggia, L Marconi, Eric Eche
    Abstract:

    Abstract Concentrating Solar Power (CSP) is considered to be one of the most promising and sustainable technologies for electricity production in the future, and as efficiency of solar Thermal systems rapidly increases with increasing working temperature, the big challenge for future is to develop novel solutions for solar receivers. In this framework, Ultra-High Temperature Ceramics (UHTCs) are mainly studied as Thermal protection materials for aerospace and military applications, but their peculiar properties (very high melting points and good thermo-mechanical properties at high temperatures) can be advantageously exploited to increase the operating temperature of thermodynamic solar plants in concentrating solar power systems. This work is devoted to the study and characterization of the spectral reflectance of hafnium and zirconium diborides containing MoSi2 as secondary phase in order to evaluate their potential as novel solar absorbers. To assess the spectral selectivity properties, room-temperature hemispherical reflectance spectra were measured from the UV wavelength region to the mid-infrared, considering different levels of porosity for each system, in order to understand how porosity affect spectral reflectance. Moreover, for zirconium diboride and hafnium diboride composites containing 10vol% of MoSi2 sintering aid, the Thermal Emittance was measured in the 1100–1400K temperature range in PROMES-CNRS solar furnace. Data obtained were compared with spectral characteristics and high temperature Emittance of a monolithic silicon carbide.