Solar control characteristics of Cu2Se coatings
TL;DR: In this article, the solar control properties of Cu2Se thin film coatings were investigated and the results are presented, which show that they exhibit superior solar control characteristics in certain respects over the metallic and PbS coatings and have comparable characteristics with CuxS films.
Abstract: Solar control coatings required for architectural glazing applications in tropical locations warrant much attention due to their vital role in energy conservation. The solar control properties of Cu2Se thin film coatings were investigated and the results are presented. It was observed that Cu2Se coatings have moderate optical transmittance and low reflectance in the visible region and high reflectance and low transmittance in the IR region. These characteristics are useful for the above purpose. The evaluation of their solar control parameters in the visible and IR region showed that they exhibit superior solar control characteristics in certain respects over the metallic and PbS coatings and have comparable characteristics with CuxS films.
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TL;DR: In this article, the authors presented a mathematical model and results of numerical simulations of a double sheet ventilated glass window, where the incident solar radiation heats up the air between the glass sheets creating buoyancy forces that induces upward flow of air.
Abstract: This paper presents a mathematical model and the results of numerical simulations of a double sheet ventilated glass window. The incident solar radiation heats up the air between the glass sheets creating buoyancy forces that induces upward flow of air. The two-dimensional transient model is formulated based upon the fundamental equations of mass conservation, momentum and energy, the associated constant and time varying boundary conditions and is solved by finite difference approach and the ADI (alternating direction implicit) scheme. The numerical grid and the time increment were optimized and the numerical results were validated against available data. Results of the temperature field along and across the channel are obtained for different spacing between the glass sheets and incident radiation conditions. The effects on the solar heat gain coefficient and the shading coefficient were also presented and discussed.
61 citations
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TL;DR: In this paper, the authors presented a study on a ventilated window composed of two glass sheets separated by a spacing through which air is forced to flow, and the model is one dimensional and unsteady based upon global energy balance over the glass sheets and the flowing fluid.
Abstract: This paper presents a study on a ventilated window composed of two glass sheets separated by a spacing through which air is forced to flow. The proposed model is one dimensional and unsteady based upon global energy balance over the glass sheets and the flowing fluid. The external glass sheet of the cavity is subjected to variable heat flow due to the solar radiation as well as variable external ambient temperature. The exchange of radiation energy (infrared radiation) between the glass sheets is also included in the formulation. Effects of the spacing between the glass sheets, variation of the forced mass flow rate on the total heat gain and the shading coefficients are investigated. The results show that the effect of the increase of the mass flow rate is found to reduce the mean solar heat gain and the shading coefficients while the increase of the fluid entry temperature is found to deteriorate the window thermal performance.
38 citations
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TL;DR: In this paper, a mathematical model with numerical simulations of the heat transfer across a simple glass window is presented, which is two-dimensional, transient based upon the energy equation with a source term to account for the solar radiation absorbed through the glass sheet.
Abstract: This paper presents a mathematical model with numerical simulations of the heat transfer across a simple glass window. The model is two-dimensional, transient based upon the energy equation with a source term to account for the solar radiation absorbed through the glass sheet. Variable incident solar radiation and external ambient temperature are considered in the numerical simulations. The governing equations and the associated boundary conditions are discretized by the finite difference approach and the ADI scheme. Numerical simulations are realized for the cases of clear and absorbing glass to show the effect of the glass thickness on the total heat gain, the solar heat gain and the shading coefficient.
37 citations
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TL;DR: In this paper, the structure of the films was analyzed using Grazing Incidence X-ray Diffraction (GIXRD) and High Resolution Transmission Electron Microscopy (HRTEM) analyses.
Abstract: Cu2Se nanocrystal (NC) films of different nanocrystal sizes were synthesized using vacuum deposition technique. The structure of the films was analyzed using Grazing Incidence X-ray Diffraction (GIXRD) and High Resolution Transmission Electron Microscopy (HRTEM) analyses. Band gaps of the films were found to decrease with increase in grain size. Analysis of the Raman spectra of the Cu2Se NC films showed that the exciton-phonon coupling in the films could be tuned by varying the grain size. DC conductivity of the films was found to increase and the activation energy for conduction to decrease with increase in the grain size of the samples. The grain size dependent conductivity along with the optical properties of the Cu2Se NC films may find practical applications such as window material for solar cells.
12 citations
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TL;DR: In this paper, the thermal behavior of a ventilated double glass window with a solar reflective film is numerically investigated and validated against results available in the literature, and the results show that in order to reduce the heat gain in the internal ambient, the optimum spacing between the glass sheets should be at least 2.5 cm.
Abstract: In the present study, the thermal behavior of a ventilated double glass window with a solar reflective film is numerically investigated and validated against results available in the literature. The objectives of the study are to develop a validated robust thermal model for the ventilated double glass window, make it versatile so that it can incorporate different inserts (such as reflective and absorptive films, etc.), different glass sheets and different fluids and can be integrated with other available design tools. The proposed ventilated double window is composed of two glass sheets separated by a gap forming a channel having a solar reflective film on the internal surface of outer glass sheet. The model is based on the equations of mass, momentum and the energy conservation equations in steady state. Boussinesq approximation is used to evaluate buoyancy term. The discretization of conservative equations is done using the finite volume method. A numerical code is developed and validated against available experimental and numerical results. Thermal performance of the ventilated double glass window is assessed under different conditions and the results show that in order to reduce the heat gain in the internal ambient, the optimum spacing between the glass sheets should be at least 2.5 cm. The solar reflective film in a ventilated double glass window can reduce the penetrating solar energy by about 64.7% in comparison with a traditional double glass window.
10 citations
References
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TL;DR: In this article, a range of combination of rsquare operator approximately 30 Omega to 1 M Omega and T% (500 nm) approximately 1 to 65 and a color of reflected daylight (golden yellow, purple, blue, green, etc.) can be obtained from chemical baths constituted from copper(II) chloride, triethanolamine and thiourea at appropriate pH.
Abstract: CuxS thin films with a wide range of sheet resistances (rSquare Operator ) and optical transmittance (T%), indicating different composition x, have been obtained from chemical baths constituted from copper(II) chloride, triethanolamine and thiourea at appropriate pH (10-12). Depending on the deposition parameters, a range of combination of rSquare Operator approximately=30 Omega to 1 M Omega and T% (500 nm) approximately=1 to 65 and a range of colour of reflected daylight (golden yellow, purple, blue, green, etc.) can be obtained. The films have been found to be stable with respect to electrical and optical properties on storage under ambient. Various possible large area applications such as in architectural glazing, photothermal and photovoltaic conversions are discussed.
162 citations
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TL;DR: In this paper, the basic requirements of solar control coatings are presented and a comparison of the characteristics of PbS and CuxS coatings against commercially available coatings is provided.
Abstract: Solar control coatings, required for architectural glazing applications in warm climates, must provide controlled optical transmission ( approximately 10-50%) of the solar radiation in the visible region and should reflect efficiently in the infrared (>0.7 mu m) region to create a cool interior in the buildings. Thin films of PbS and CuxS on glass substrates, deposited from chemical baths, are shown to possess excellent solar control characteristics-superior or comparable to the metallic solar control coatings. For example, for an acceptable range of integrated optical transmittance ( approximately 10-20%) in the visible region, the integrated infrared reflectance for AM2 solar spectrum for the different glazings are: PbS coated glass, 50%; CuxS coated glass, 14%; stainless steel/Cu coated glass, 25% and tinted glass, 4%. The CuxS and PbS coatings also have the advantage of giving pleasant reflected colours (golden, purple, blue, etc), which improves the cosmetic appearance. This paper presents the basic requirements of solar control coatings and provides a comparison of the characteristics of PbS and CuxS coatings against commercially available coatings.
133 citations
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TL;DR: In this paper, the safety and cost and the optimisation of chemically deposited PbS thin films for solar control applications are presented. But the results of the analysis are limited to the case of 3 mm thick clear glass with a shading coefficient of approximately 50%.
Abstract: Assessments of safety and cost and the optimisation of chemically deposited PbS thin films for solar control applications are presented. The maximum integrated infrared reflectance, 44%, is obtained at a PbS thin film thickness of approximately=95 nm. The corresponding value of the solar control parameters (AM2 case) are: integrated infrared transmittance, 45%; integrated visible transmittance, 17% (yellowish appearance); integrated visible reflectance, 21% (purple appearance); and integrated solar absorptance, 36%. The total solar radiation and heat transfer into the building through a glazing with such a PbS coating is less than 44%, as compared with the approximately=84% of 3 mm thick clear glass, giving a shading coefficient of approximately=50%. A film thickness of 95 nm is obtainable with a deposition time of 50 min from a bath (at 24 degrees C) containing Pb2+ ions and thiourea in the 1:3 molar ratio. However, molar ratios up to 1:5 may be employed, thereby enabling the reduction of deposition time to 35 min. Analyses of the safety and the cost of these coatings have shown excellent promise for their application as medium-efficiency low-cost solar control coatings appropriate for small-scale industrial and 'do-it-yourself' production of the coatings.
94 citations
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TL;DR: In this paper, the electrical and optical properties of thin films of highly doped oxides of In and Sn were investigated and the free electron mobility was limited mainly by ionized impurity scattering.
Abstract: The electrical and optical properties of thin films of the highly doped oxides of In and Sn are investigated. Maximum free electron densities of 15 × 10 20 cm −3 in In 2 O 3 and 7 × 10 20 cm −3 in SnO 2 are obtained in films prepared by the hot spray technique by appropriate doping. Free electron density and mobility are strongly influenced by additional oxygen. The free electron mobility is limited mainly by ionized impurity scattering. Optimized filters are designed for solar collector and window applications, taking into account a modified Drude behaviour.
76 citations
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TL;DR: In this paper, chemical deposition of lead sulfide thin films on glass substrates was used to satisfy the basic requirements for solar control coatings for window glazing applications in warm climates, where a low transmittance ( ∼10% to 30% ) in the visible region is coupled with an appreciable reflectance for infrared radiation.
Abstract: Chemically deposited lead sulfide thin films on glass substrates are found to satisfy the basic requirements for solar control coatings for window glazing applications in warm climates, where a low transmittance ( ∼10%–30% ) in the visible region is to be coupled with an appreciable reflectance for infrared radiation The depositions were made on glass substrates from alkaline/ ammoniacal baths of lead acetate, thiourea and small amounts of triethanolamine The coating can produce a gray, purple or bluish appearance in reflected daylight with near normal specular reflectance (visible region) of ∼15%–25% These coatings appear yellowish in transmitted daylight with 7%–25% transmittance, depending on the duration of deposition The integrated infrared (070 to 25 μm) reflectance for air mass (AM) 2 solar spectrum of typical PbS coated glass is ∼37% as compared to ∼7% for the uncoated glass The advantages of chemical deposition for large area coatings, the desirable features of PbS as a solar control coating, and toxicity considerations are discussed
63 citations