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.
64 citations
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.
47 citations
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.
41 citations
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.
20 citations
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.
17 citations
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TL;DR: In this paper, the solar control characteristics of chemically deposited PbS and CuxS thin films in the glass-PbS-CuxS structure are reported, and a 15 min air bake at 150 degrees C has been found to reduce the sheet resistance of the Cux s films by two to three orders of magnitude, which in turn drastically decreases the integrated NIR transmittance, T*(IR), of the Pb s-CoxS combination (typically from 46% to 14%).
Abstract: Solar control characteristics of chemically deposited PbS and CuxS thin films in the glass-PbS-CuxS structure are reported. This combination offers pleasing colours: bluish, greenish, greenish-yellow etc in reflected daylight and low NIR transmittance-not possible with PbS-only coatings, while providing a high-enough NIR solar reflectance-not achievable with CuxS-only coatings. A 15 min air bake at 150 degrees C has been found to reduce the sheet resistance of the CuxS films by two to three orders of magnitude, which in turn drastically decreases the integrated NIR transmittance, T*(IR), of the PbS-CuxS combination (typically from 46% to 14%), while retaining the integrated transmittance, T*(vis), and the integrated reflectance, R*(vis), in the visible region to within 14-30% and 15-20% respectively for the various PbS-CuxS combinations. The major advantage of the PbS-CuxS thin film combinations as solar control coatings is that by controlling the thicknesses of the individual films a range of combinations of T*(vis), R*(vis), T*(IR), R*(IR) and colour in reflected daylight is achievable. This makes them very versatile for architectural glazing applications to suit different space conditioning, illumination level and cosmetic requirements.
59 citations
TL;DR: In this paper, CuxS thin films, deposited from chemical baths on glass substrates and air-annealed at 150 degrees C and then given a polymer protective coating, have been found to offer optical transmission and reflection characteristics near to ideal solar control characteristics.
Abstract: CUxS thin films, deposited from chemical baths on glass substrates and air-annealed at 150 degrees C and then given a polymer protective coating, have been found to offer optical transmission and reflection characteristics near to ideal solar control characteristics. The transmission spectra in the visible region resembles the phototopic vision spectra, with an integrated transmittance of approximately=30%-providing a greenish-yellow illumination of the interior under daylight. The low integrated visible reflectance of approximately=9% prevents glare and the mild bluish-purple colour in reflected daylight improves cosmetic appearance. Due to the low sheet resistance of the films approximately=30 Omega Square Operator -1, the integrated infrared transmittance is very low, approximately=10% and the integrated infrared reflectance is acceptably high, 25%. The total optical and thermal transmittance into the interior through the CuxS coated glazing is in the 30-35% range, assuring substantial saving in the cooling costs when these glazings are employed in regions with a generally warm climate. Various possibilities in the commercial production of the coatings are suggested.
42 citations
TL;DR: In this paper, physical vapour deposited CdSexTe1-x thin films of thickness about 0.1 mu m were studied for solar control applications and the films were characterized with respect to film parameters such as film thickness, substrate temperature and deposition rate to get films with good solar control characteristics.
Abstract: Solar control coatings used in architectural glazings of buildings in warm climates should exhibit controlled optical transmittance (10-50%) in the visible region and must reflect effectively (90%) in the IR region. Physical vapour deposited CdSexTe1-x thin films were studied for solar control applications. The films were characterised with respect to film parameters such as film thickness, substrate temperature and deposition rate to get films with good solar control characteristics. The solar control characteristics of the films were calculated in the range 0.40-2.40 mu m. It was observed that the solar control parameters of the films are composition dependent but depend also on the above film parameters. CdSexTe1-x thin films of thickness about 0.1 mu m exhibited better solar control characteristics than metallic coatings and other films such as CuxS and PbS.
25 citations
12 Nov 1987
TL;DR: A detailed investigation of a multilayer design for a temperature resistant low emissivity and highly electrical conductive coating is performed in this article, where optical transmittance, reflectance and the color coordinates are discussed.
Abstract: A detailed investigation of a multilayer design for a temperature resistant low emissivity and highly electrical conductive coating is performed. The optical transmittance, reflectance and the color coordinates are discussed. A good agreement with computer simulated spectra and experimental data was achieved. The layer system was prepared by high rate magnetron sputtering on large float glass sheets. By gravity bending in normal atmosphere these coated substrates were formed and then further processed to heated windshields and curved double glazed units. The performance characteristics of these final products are discussed.
15 citations
11 citations