Solar Window Films Research Articles

Multi-Criteria Decision-Making for Selecting Solar Window Film Sheets for Energy Saving in Buildings

Recently, there have been several advancements in the field of sustainable energy solutions, particularly in the selection of solar window film sheets. In this research, a multi-criteria decision-making approach was applied to compare three different types of window film sheets, Silver 35, TrueVue 15, and Sterling 40, to aid in selecting the most suitable window film based on the United Arab Emirates market. The primary aim of this work is to provide decision-makers with a structured approach to enhance their choices for selecting window film sheets. The methodology employed involves evaluating various criteria, including visible light transmittance, solar energy rejected, energy transmittance, energy absorptance, cost, glare reduction, visible light reflectance interior, and fade reduction. These criteria are assessed using the Analytic Hierarchy Process (AHP) and Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS). The results demonstrate that Sterling 40 is the best choice followed by Silver 35. Based on the final TOPSIS results, the difference between the scores of these two window film sheets was not significant, while they were far from the score of TrueVue 15.

Climate change and thermo-solar patterns of office buildings with/without window films in extreme hot-arid climate of Kuwait

This research attempts to develop a systematic method to address climate changes by studying temperature-humidity patterns as the two major meteorological parameters and to moderate these effects using a commercially available window film on interior windows of an office building with double-glazing. A three-floor educational building at Australian College of Kuwait (ACK) was equipped with temperature, humidity and illuminance sensors for two similar size offices, one with 3 M Neutral 20 window films. Total readings of 50,000 entries from each sensor was recorded every 3 min by a home-designed microprocessor-based logging system for three months of June, July, and August 2019. In parallel, the ACK building was simulated in EnergyPlus and DesignBuilder software and calibrated with the experimental measurements. Histograms and a probability density function (PDF) of temperature and humidity are built by a representative rational function as a model of main climate parameters variations. By examining min-mean-max values of data, it is observed that the office with window films has increased indoor humidity and, in most instances, reduced temperature by 2–5 °C compared to double-glazed bare windows which can significantly reduce cooling loads in extreme hot-arid climates. Simulation results are presented on the energy saved and the reduced CO2 footprints by applying the solar window films in the ACK building.

Experimental study on the performance of solar window films in office buildings in Kuwait

This work examines the solar performance of double-glazed windows in four offices in ACK buildings with and without solar window film in actual working conditions. Window films are passive thin films stick to the interior or exterior of windows to effect various solar-optical impacts including energy saving, UV reduction, and increased thermal comfort. For this study, the 3M Neutral 20 and 70 are selected which are made of multilayer nanofilms of 220 SAN25/THV 95-nm thick reflective layers. Real-time measurements of temperature, humidity, and luminous were conducted in 5 min intervals over the months of June, July, and August 2019 and data stored through WiFi system in iClouds. Arduino-type microprocessors and various temperature-humidity, and LUX sensors were assembled and programmed to transfer and store data in real time. Exploring and analyzing the data collected for four offices with and without window films in summer of Kuwait, it is evident that window film has good potential to save water by preserving interior humidity to the level of human comfort, decrease interior temperature to save energy and reduce CO2 footprints, to restrict the solar UV rays to minimum level, and to reduce visual impacts of high solar luminous. The benefits and drawbacks of the selected window films are discussed here for the weather condition of Kuwait.

Impact of Window Films on the Overall Energy Consumption of Existing UK Hotel Buildings

Recently, considerable attention has justifiably been directed towards energy savings in buildings as they account for up to 20–40% of total energy consumption in developed countries. In the United Kingdom, studies have revealed that buildings’ CO2 emissions for account for at least 43% of total emissions. Window panels are a major component of the building fabric with considerable influence on the façade energy performance and are accountable for up to 60% of a building’s overall energy loss. Therefore, the thermal performance of glazing materials is an important issue within the built environment. This work evaluates the impact of solar window films on the overall energy consumption of an existing commercial building via the use of a case study U.K. hotel and TAS dynamic simulation software. The study results demonstrated that the impact of window films on the overall energy consumption of the case study hotel is approximately 2%. However, an evaluation of various overall energy consumption components showed that the window films reduce the annual total cooling energy consumption by up to 35% along with a marginal 2% increase in the annual total heating energy consumption. They can also provide overall cost and CO2 emissions savings of up to 3%.

Evaluation methods for retroreflectors and quantitative analysis of near-infrared upward reflective solar control window film—Part II: Optical properties evaluation and verification results

In recent years, cool materials that have high solar reflectivity and thermal emittance properties have been applied for building surfaces in the urban environment. However, when such highly reflective materials reflect all or part of the solar radiation downwards or towards the ground, there are concerns that it leads to deterioration of the thermal environment of pedestrian spaces.A newly developed near-infrared (NIR) upward reflective solar control window film (URSCF) has come to the market. The film reflects NIR upwards to the sky, and shields a building’s interior from solar radiation without deteriorating the thermal environment of pedestrian spaces.In order to quantify the reflected solar radiation, it is necessary to clarify the reflectivity and transmissivity properties of retro-reflective materials, which is desirably performed through measurement in a stable environment using artificial light sources. This required development of the evaluation methods using apparatus including an integrating sphere, allowing the measurement of directional-hemispherical spectral reflectivity at large incident polar angles, as well as the selective measurement of directional-upward spectral reflectivity from retro-reflective surfaces.It was confirmed that these results are appropriate through verification with the results obtained from commercially available apparatus and from optical simulations. With respect to the effect of NIR URSCF, it was confirmed that downward reflectance of solar radiation at the incident polar angle of 70° and the incident azimuth angle of 0° was approximately half of that of conventional specular reflective solar control window film.

Evaluation methods for retroreflectors and quantitative analysis of near-infrared upward reflective solar control window film — Part I: Theory and evaluation methods

In recent years, research has been actively conducted on the application of cool materials that have high solar reflectivity and high thermal emittance to building envelopes (roofs and walls) and other surfaces in the urban environment. They have been applied to decrease solar absorption and increase the urban albedo as an effective technique to mitigate the Urban Heat Island effect and to reduce global warming. It has been a concern that reflected solar radiation onto the streets (downward reflection) leads to thermal environmental deterioration of pedestrian spaces. In cases where building facades have specular or diffusive reflectivity, solar radiation is reflected downward to pedestrian spaces.As there is currently a lack of evaluation methods for such retro-reflective materials, this study mainly aims at developing evaluation methods and measurements of reflectivity and transmissivity properties of retro-reflective materials. This required further development of evaluation methods and the apparatus including an integrating sphere, allowing the measurement of directional-hemispherical spectral reflectivity (DHSR) at large incident polar angles that are equivalent to the daytime solar elevation at a south-facing vertical surface, as well as the selective measurement of spectral reflectivity in the upward direction with the horizontal plane as the boundary. Furthermore, evaluation methods of DHSR including the retro-reflected beam that leaks from the incident opening are developed with a new measurement method using an integrating sphere and half mirror.This article mainly describes theory and methods of the above-mentioned evaluation, and evaluates results of beam leakage compensated DHSR. Verification of the measurement results is discussed in Part II of this article, together with the properties and effects of the upward reflective solar control window film that was evaluated in this study.

Optical properties and field test results of spectrally-selective solar control window film that enables not increasing downward reflection

Recently high reflective materials such as high reflectance paint for wall and solar control film or Low-E glass for window are utilized as a building façade aiming for reducing the cooling load of the buildings. From a view point of the direction of reflected rays, almost half of the energy goes upward due to diffuse reflection in case of paint, meanwhile most of energy goes down to the ground due to specular reflection by the glass. This leads to deterioration of thermal environment of surrounding buildings, and is one of causes of urban heat island. Retro-reflective façade materials are promising candidates for mitigation of urban heat island. The authors successfully developed a new type of transparent solar control window film Albeedo that selectively reflects near-infrared rays towards the sky. The film has a saw-tooth microstructure with a spectrally-selective reflection layer. This microstructure is able to reflect infra-red rays toward the sky. The upward reflectance of the film is measured by our custom made spectroscope. Firstly, the sample is placed in a large scale integrating sphere. Then, solar energy absorptive materials are arranged under the sample to absorb the transmitted component and positioned where the downward reflection goes to. Finally, a halogen lamp irradiates the sample at an incident angle of 60° as a light source. The result of the upward reflectance of near-infrared is about 33%. We also conducted field test measurements to evaluate the energy savings of the interior of the building and the degree of reflection of the exterior.

Simulation of Energy Demand for HVAC in a Shopping Centre – Case Study

The target of this contribution is the energy simulation of energy demand for heating system in winter period and for cooling system in summer period. The object of the energy simulation is the shopping centre. It is solved the main passage of the centre that is basically the internal enclosed multi-stories space (atrium). The passage has large glass surfaces on the exterior walls and on the roof. Mainly because of this state the cost to cooling system operation are very high in summer period. There are proposed and analysed two variants of shading devices, active and passive. The passive devices are solar window films, the active devices are dynamic window blinds. The energy simulation of all proposed variants is elaborated in order to achieve more effective operation of the cooling system on the one hand and of the heating system on the other hand in term of energy demand. For our target of this article we used simulation software called DesignBuilder.

Lean Strategies for Window Retrofit of Italian Office Buildings: Impact on Energy Use, Thermal and Visual Comfort

The aim of this paper is to explore lean retrofit strategies for transparent envelope of existing Italian office buildings, to improve their performance and to ensure low energy use and a good thermal and visual comfort.Solar and light control is necessary to prevent overheating in office buildings those generally present high internal loads. The effectiveness of solar window films use in Italian buildings context is here investigated, in comparison with other strategies like the use of internal roller blinds and the substitution of the existing window panes with high performance ones. A sensitivity analysis was assessed to evaluate the office unit primary energy use under different retrofit solution, weather conditions and window to wall ratio. A conventional existing office unit was modeled in EnergyPlus and LBNL Radiance to assess heating, cooling and lighting energy demand coupled with visual comfort parameters. Thermal comfort was evaluated hourly in accordance with ISO 7730. The results are presented with a cost - benefit analysis to understand the best retrofit solution.

Experimental and theoretical study on the effect of window films on building energy consumption

Solar control films are designed to absorb or reflect the incident solar radiation, in order to reduce solar transmission through window glass. In the present study, the glass surface temperatures were measured for selected solar window films on various applications, and compared to the cases of the same window glass types without solar window films. Dynamic simulation models are also developed with the aid of the building energy simulation program EnergyPlus. After experimental validations, the computer models are used to evaluate the energy saving potentials of the subject samples of solar window films as applied onto glazing of three different function rooms in Hong Kong, namely office, shopping mall and hotel guest room. The results show that the thermal performance of the film applications on clear glass is better than on tinted or laminated glass windows. Solar films have very good energy saving potential when applied to all three functional areas in commercial buildings, and the best results are found in office applications.

Case study: Energy savings from solar window film in two commercial buildings in Shanghai

The objective of this study was to understand the energy savings from applying solar window films in a commercial building with large, curtain wall areas in Shanghai, China. eQUEST was used to simulate the annual building performance with and without the solar window film. The simulation model was calibrated against the measured monthly and daily electrical consumption. The simulation results indicated that two factors significantly influence the effect of the window film. These factors include the position of the installed window film and the configuration of the original glazing system. The effect of the window film on the performance of the curtain wall glazing system varies greatly, depending on the type of film and how it is applied. The film can decrease the shading coefficient and solar heat gain coefficient by 44% and 22% if applied on the outside and inside of the existing windows, respectively. For a double pane, low-E glazing system, the building cooling load through the windows on design day is reduced by 27.5% and 2.2% for outside and inside window films, separately. Adding the window film inside of the curtain wall was not effective because the increased window conductive heat transfer offsets the decreased cooling load from solar radiation.

Solar Gard window film cuts carbon emissions worldwide

Solar Gard window film cuts carbon emissions worldwide

Energy Saving and Tourism Sustainability: Solar Control Window Film in Hotel Rooms

This paper investigates solar control film as an energy saver in the fast growing hotel sector in southern China. It investigates claims made for this low-cost retrofitted material in hotel rooms, calibrating reductions in solar gain in summer. It provides reliable and independent data about the performance and economic viability of solar control film in real hotel environments. The study found that, by limiting solar gain, the film helps limit tourism's impact on global warming and climate change. The paper also foreshadows new technical glazing developments.

Energy Saving and Tourism Sustainability: Solar Control Window Film in Hotel Rooms

This paper investigates solar control film as an energy saver in the fast growing hotel sector in southern China. It investigates claims made for this low-cost retrofitted material in hotel rooms, calibrating reductions in solar gain in summer. It provides reliable and independent data about the performance and economic viability of solar control film in real hotel environments. The study found that, by limiting solar gain, the film helps limit tourism's impact on global warming and climate change. The paper also foreshadows new technical glazing developments.

Thermodynamic evaluation of the In–Sn–O system

Thermodynamic evaluation of the In–Sn–O system was made, because indium-tin-oxide (ITO) system is used for instance in transparent electrodes for display devices, transparent coatings for solar energy heat mirrors and window films in n–p heterojunction solar cells. The thermodynamic data is limited, so the phase diagram for In–Sn–O system is somewhat tentative.

Effects of Solar Control Window Films on Color Changes of Upholstery Fabrics Exposed to Sunlight

The influence of semi–transparent Mylar® solar control window films on color changes of three upholstery fabrics was investigated through exposure of the fabrics in outdoor chambers. Comparisons were made among fabrics exposed in racks equipped with window glass without film and identical fabrics exposed in racks containing window glass onto which three different solar control films were applied. Changes in color of the fabrics were assessed at two–week intervals over a 24–week exposure period.

Sputtering system for multicharacteristic solar window films

A flexible substrate sputter coating apparatus is described, and thin film composites fabricated by the multicathode system are analyzed. Auger spectroscopy, X-ray diffraction and scanning electron microscopy diagnostics are used to investigate resulting films produced by in-line multilayer film deposition. The primary application for the films is in the selective solar window film markets. The large-area coating capability also lends itself to a wide field of specially defined uses. Antistatic, thermal control, electrical flexible circuitry, transparent conductors, electromagnetic pulse shielding and vertical magnetics as well as other metal and metal oxide coatings are discussed and production techniques are described.