Windows are vital elements in the built environment that have a large impact on the energy consumption in indoor spaces, affecting heating and cooling and artificial lighting requirements. Moreover, they play an important role in sustaining human health and well-being. In this review, we discuss the next generation of smart windows based on organic materials which can change their properties by reflecting or transmitting excess solar energy (infrared radiation) in such a way that comfortable indoor temperatures can be maintained throughout the year. Moreover, we place emphasis on windows that maintain transparency in the visible region so that additional energy is not required to retain natural illumination. We discuss a number of ways to fabricate windows which remain as permanent infrared control elements throughout the year as well as windows which can alter transmission properties in presence of external stimuli like electric fields, temperature and incident light intensity. We also show the potential impact of these windows on energy saving in different climate conditions.

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Infrared regulating smart window based on organic materials

Chemical deposition method for metal chalcogenide thin films

Semiconductor thin films by chemical bath deposition for solar energy related applications

Nanoparticles of copper sulfide have been synthesized by reacting a copper ammonia complex with an equimolar thiourea solution in Triton-X 100/cyclohexane water-in-oil microemulsions. The presence of an exceptionally sharp and blue-shifted peak at 475 ± 2 nm in the UV−vis spectrum reveals the formation of quasi-monodispersed, size-quantized particles. Using absorption spectroscopy, the formation of a chalchocite (Cu2S) phase is inferred. The peak position in the absorption spectra was found to be independent of net micellar water content as well as aging effect. It is attributed to the formation of a Cu(I) thiourea complex on the surface of the particles, which are hydrogen bonded to the polyoxyethylene (POE) chain of Triton-X 100 (TX-100). The role of thiourea in the tailoring of particles to the micellar periphery was confirmed by synthesizing the nanoparticles using other S2- agents like H2S, and Na2S. The role of the POE chain in mediating the adsorption was brought out by carrying out the reaction in...

Synthesis and Characterization of Copper Sulfide Nanoparticles in Triton-X 100 Water-in-Oil Microemulsions

Spray pyrolysis deposition of CuS thin films

A mathematical model to predict the shading coefficients (SC) and solar rejection factor (SRF) of various types of chemically deposited solar control coatings is presented. The values of SC and SRF are presented for coatings with soar absorptance in the 50-75% range and solar reflectance in the 10-25% range for typical exterior temperature of 10-50 degrees C. Chemically deposited solar control coatings with a protective polymer coating applied on 6 mm thick sheet glass in architectural windows are seen to provide SC in the 0.3 to 0.75 range depending on the optical characteristics and exterior temperatures. A solar rejection factor of 33-56% is available from the coatings already reported.

http://iopscience.iop.org/article/10.1088/0022-3727/26/8/023/pdf

Theoretical analysis of the thermal performance of chemically deposited solar control coatings

Solar control characteristics are described for chemically deposited thin film coatings consisting of an initial layer of Bi[sub 2]S[sub 3] film of [approximately] 0.05 [mu]m thickness deposited at room temperature (25 C) for 45-76 min from baths containing bismuth nitrate, triethanolamine (TEA) and thioacetamide and a Cu[sub x]S thin film of 0.1-0.25 [mu]m thickness deposited either at room temperature, for 3-6 h, or at 50 C, for 1-2 h using baths consisting of copper(II) chloride, TEA, thioureau (TU), NaOH and NH[sub 3](aq). Air annealing of these films at 150 C for 30 min yield well-desired solar control characteristics: sheet resistance in a range which signifies a low thermal emittance; integrated transmittance of 15-32% in the visible region and 11-22% in the near-infrared region; integrated transmittance of [approximately]13-25% for solar radiation and a range of shades in reflected daylight. Using a mathematical model, the solar control performance of these coatings in a 6 mm sheet glass is predicted for an architectural window in a tropical location showing that solar radiation rejection of [approximately] 50% is obtainable for a integrated transmittance of 17%.

Chemically deposited Bi[sub 2]S[sub 3]-Cu[sub x]S solar control coatings

Theoretical analysis of the thermal performance of all-glass evacuated tube solar collectors with absorber coating on the outside or inside of the inner tube

Thermal performance of an architectural window with chemically deposited SnSCuxS solar control coating

Theoretical efficiencies of an evacuated-tube solar collector using a chemically deposited SnS-CuxS absorber thin film ( alpha =0.91) in contact with the working fluid are presented. A mathematical model is developed and solved numerically to yield photothermal conversion efficiencies eta of the collector for the heat transfer coefficient hb of 0.026 W m-2 K-1 (good vacuum). The analysis shows that the eta of such a collector would be unacceptably low, approximately=25%, for the operating parameter f approximately=0.1 degrees C m2 W-1 which represents the typical operating condition of an evacuated-tube solar collector. However, the use of a low emissivity ( epsilon ) transparent coating applied to the outer surface of the absorber tube (i.e. in the place of the spectrally selective solar absorber coating in the conventional all-glass evacuated-tube collector) can yield eta approximately=75% for f approximately=0.1 degrees C m2 W-1 for epsilon =0.1 with water as the heat transfer fluid and eta approximately=68% with a mineral oil as the heat transfer fluid.

P.K. Nair

Papers

Theoretical analysis of the thermal performance of chemically deposited solar control coatings

Chemically deposited Bi[sub 2]S[sub 3]-Cu[sub x]S solar control coatings

Theoretical analysis of the thermal performance of all-glass evacuated tube solar collectors with absorber coating on the outside or inside of the inner tube

Thermal performance of an architectural window with chemically deposited SnSCuxS solar control coating

Theoretical efficiency of an all-glass tubular solar collector using a chemically deposited SnS-CuxS absorber inside the inner tube