Transparent Insulation Research Articles

Parametric analysis on the performance of flat plate collector with transparent insulation material

Abstract The transparent insulation materials (TIM) can effectively improve the performance of flat plate solar collector in cold weather. A three dimension numerical model of flat plate collector with TIM has been developed in this paper. The computational fluid dynamics (CFD) have been used to simulate the model. The Renormalization-group (RNG) k-e model and Discrete Ordinates (DO) radiation model were adopted. The influences of the environment conditions, mass flow rate, tilt angle and transmittance on the performance of the collector with TIM were analyzed. A good agreement was achieved between the CFD prediction and the previous experiment. The result shows that the collector with TIM is more efficient, when ambient temperature is low. For various wind speeds, the new collector's efficiency has a slightly change. The transmittance of TIM is a key parameter to achieve high performance for the collector. When the transmittance is below 80%, the collector with TIM has no the advantage of being good value. The optimum mass flow rate is 0.06 kg/s under corresponding conditions. The tilt angle of the collector with TIM has less effect compared with the conventional one.

Effect of the concentration ratio on energetic and exergetic performance of concentrating solar collectors with integrated transparent insulation materials

The effect of the concentration ratio on the performance of parabolic trough and central receiver collectors with integrated transparent insulation materials (TIMs) is analyzed in this work. A model based on optical, energy, and exergy analyses is developed to determine thermal and second law efficiencies of concentrated solar collectors as a function of the absorber temperature and concentration ratio. The results are compared with the respective traditional collector configurations without TIM. In general, high concentration ratios are fundamental to maintain high efficiencies. The incorporation of a TIM into concentrated solar collectors leads to higher thermal efficiencies at high operating temperatures even at low concentration ratios. An equivalent second law efficiency to that of the reference collector configuration can be achieved at lower concentration ratios by incorporating a TIM in parabolic trough or a TIM and a glass envelope in central receiver collectors. The idea of using a TIM deserves further exploration as it seems to be a promising alternative that contributes to a more efficient and cost-effective technology.

CFD investigation of a new flat plate collector with additional front side transparent insulation for use in cold regions

In cold environments, flat plate solar collectors are of limited value because high heat losses lead to low efficiency. The integration of polymethyl methacrylate (PMMA) sheet into flat plate collector is presented in this paper. The performance of this collector in cold weather was investigated using a three-dimension simulation model. A simplified experiment was conducted to verify the precision of numerical model and the simulation data can agree very well with practical ones. The effects of the thickness and location for PMMA sheet on the performance of collector efficiency following steady state were analyzed. The transmittance of transparent insulation material is the key parameter to achieve high performance for the collector. The optimum thickness of the transparent insulation material is 1 mm in simulated conditions and the best location of PMMA sheet was achieved. The result shows that the increase of the collector efficiency from the conventional collector is 11.3%, when reduced temperature difference is equal to 0.1 m2 °C/W and the ambient temperature is −20 °C.

A novel transparent thermal insulation bilayer coating based on ATO/Black TiO2

Abstract Significant progress has been made in transparent thermal insulation coating by various effective materials in recent years. More recently, Low-E coating, as a high reflection coating, has been applied in many buildings, but the coating would cause light pollution due to visible light reflection, resulting in prohibiting use in many countries. Hence, a novel transparent thermal insulation coating based on ATO/Black TiO2 is proposed in this paper. The bilayer coating exhibited a high near infrared light blocking rate of 86%, and the visible light transmittance was about 62%. Meanwhile, the structural thin films had excellent photocatalytic property, which could degrade approximately by 45% of methylene blue in 3 hours under fluorescent lamp. The double layered coating had shown a water contact angle of lower than 5° after activating. Overall, these structural films show a great potential for applications in energy conservation windows.

Facile synthesis of urchin-like Cs x WO3 particles with improved transparent thermal insulation using bacterial cellulose as a template.

Urchin-like CsxWO3 particles were synthesized using bacterial cellulose (BC) as a template by the hydrothermal method. The effects of the BC addition amount on the morphology, W5+ content and transparent thermal insulation of CsxWO3 were studied. It has been confirmed that abnormal growth of CsxWO3 rods was greatly reduced after introduction of BC into the precursor solution. Moreover, introduction of BC into the precursor solution could significantly improve the transparent thermal insulation properties of the CsxWO3 film. In particular, when the BC amount was appropriate, the prepared CsxWO3 film exhibited better visible transparency, with the visible light transmittance (TVis) more than 60%. In addition, the urchin-like particles could be transformed into small size nanorods after H2 heat-treatment, exhibiting excellent visible light transparency and thermal insulation performance. In particular, it has been proved that the 20BC-HT-CsxWO3 film exhibits excellent thermal insulation performance, and shows broad application prospects in the field of solar heat filters and energy-saving window glass.

Energy performance and economic analysis of a TIM-PCM wall under different climates

The application of an innovative translucent superinsulated latent heat storage wall, combining transparent insulation material and phase change materials (TIM-PCM wall), on the envelope of a typical office under different climates is evaluated. Energy and economic analysis related to this application are presented. The simulation process is carried out using an experimentally validated numerical model. The results show that the incorporation of the TIM-PCM wall, on the south orientation, is more efficient than the use of a double-glazed in all considered climates. The optimum TIM-PCM wall area is evaluated economically through life-cycle cost and payback period analysis. The purpose is to ensure effective performance of the wall in each climate and at the same time to ensure economic viability. The results show that, in polar and subarctic climates, the application of the TIM-PCM wall has a high economic value and the investment appears to be attractive, the payback period being 10.5 years and 7.8 years respectively. In Dras (continental climate), the use of the wall is found economically unfeasible due to low energy prices and high discount rates. At current prices, the TIM-PCM wall investment in Sacramento (Mediterranean climate) and Toronto (Humid continental) does not offer economic benefits.

One pot synthesis of Pt-doped CsxWO3 with improved near infrared shielding for energy-saving film applications

In this study, Pt-doped CsxWO3 (Ptn-CsxWO3) nanorods with improved near infrared shielding and transparent thermal insulation were synthesized by one pot solvothermal method using cheap sodium tungstate and cesium sulfate as raw materials. The role of Pt-doping on the crystal structure, morphology and transparent thermal insulation of the Ptn-CsxWO3 products was investigated. The results indicate that Pt catalysis plays an important role in promoting oxygen vacancies and W5+ generation, and can improve the near infrared shielding performance of Ptn-CsxWO3 greatly. Furthermore, the as-synthesized Ptn-CsxWO3 nanorods could achieve excellent near infrared shielding and transparent thermal insulation performance without requiring additional reduction heat-treatment. Especially, when the Pt/W molar ratio is 0.01 (n = 0.01), the as-prepared Pt0.01-CsxWO3 product with diameter of 10–30 nm and length of 20–80 nm exhibit best visible light transparency and near infrared shielding ability, with the maximum visible transmittance and near infrared shielding rate being 72% and 92% respectively. The excellent transparent thermal insulation performance of Ptn-CsxWO3 nanoparticles without needing additional heat-treatment enables them to be more suitable for energy-saving film applications in the building and automobile window glasses.

A transparent insulation façade enhanced with a selective absorber: A cooling energy load and validated building energy performance prediction model

Solar thermal façade concepts for building integration have a relevant contribution in the field of renewable solar energy exploitation. This study is focused on an experimental analysis of a transparent insulation façade (TIF) concept and the options for the prediction of its performance using building energy simulation (BES) modelling. A TIF prototype based on a transparent insulation material (TIM) and a selective absorber is tested and compared with a nonselective type of absorber. An experimental study was conducted involving full-scale climatic chamber and dynamic outdoor tests. The proposed TIF concept with a selective absorber and its solar effective layers provides the same thermal performance as conventional types of thermal insulation. As the TIM integration is potentially limited by overheating phenomena, a maximum cooling energy load obtained by dynamic outdoor conditions provides its real outdoor performance. The results show that a significant difference is measured when compared with the nonselective absorber type. Finally, a detailed comparative investigation of the thermal performance of both TIFs was conducted using the BES method. When applying the low-e functionality of the solar absorber, significant limitations were found specifically concerning the surface radiant heat exchange with the low emissivity surface affecting the air cavity enclosed zone.

Life Cycle Assessment of Solar Façade Concepts Based on Transparent Insulation Materials

Contemporary architecture and construction industry are trying to cope with increasing requirements concerning energy efficiency and environmental impacts. One of the available options is the active utilization of energy gains from the environment, specifically solar energy gains. These gains can be utilized by, for example, solar walls and facades. The solar façade concept has been under development for more than a century. However, it has not achieved widespread use for various reasons. Rather recently the concept was enhanced by the application of transparent insulation materials that have the potential to increase the efficiency of such façades. The presented study evaluates the environmental efficiency of 10 solar façade assemblies in the mild climate of the Czech Republic, Central Europe. The evaluated façade assemblies combine the principles of a solar wall with transparent insulation based on honeycomb and polycarbonate panels. The study applies Life-Cycle Assessment methodology to the calculation of environmental impacts related to the life cycle of the evaluated assemblies. The results indicate that even though there are several limiting factors, façade assemblies with transparent insulation have lower environmental impacts compared to a reference assembly with standard thermal insulation. The highest achieved difference is approx. 84% (in favor of the assembly with transparent insulation) during a modelled 50-year façade assembly service life.

Thermal, energy and life-cycle aspects of a transparent insulation façade: a case study

Research and development in the façade engineering field highlights the need for comprehensive system solutions integrating advanced materials and renewable energy use. Presented study focuses on implementation of Transparent Insulation Materials (TIMs) in a façade concept. The idea is based on sensible use of (renewable) solar energy to reduce the heating demand of buildings. The concept integrates TIMs into a Transparent Insulation Façade (TIF) based on more common “solar wall” or “Trombe wall” systems enhanced with selective absorber (SA) functionalities. The study presents analysis of thermal, solar energy and environmental performance of the concept on a case study basis. Firstly, thermal analysis based on standard calculation is introduced to describe thermal and solar performance of the concepts. Secondly, energy balance calculations are used to compare the concepts with conventional façade systems. Finally, a Life-Cycle Assessment (LCA) evaluating the environmental impacts of the façade concept is introduced. The results show that the proposed concept performs better in both energy consumption and environmental impacts compared to a common facade with external thermal insulation. The TIF has higher heating energy demand than a common façade, however this is offset by up to 178 kWh⋅m−2⋅a−1 solar heat gains. The difference in environmental impacts (up to 80%) is also in favour of the TIF.

Microstructure regulation of CsxWO3 nanoparticles by organic acid for improved transparent thermal insulation performance

In order to further improve the transparent thermal insulation of CsxWO3, controllable synthesis of CsxWO3 nanoparticles from cheap and environment-friendly Na2WO4·2H2O and Cs2SO4 by solvothermal method was conducted using different organic acids as reducing agents. The reducibility and reduction mechanisms of citric acid, tartaric acid and oxalic acid were investigated. It has been confirmed that tartaric acid has the strongest reducibility, and could produce the most W5+ and oxygen vacancies in the CsxWO3 products before heat-treatment. The CsxWO3 nanoparticles synthesized with oxalic acid after heat-treatment exhibited the best crystallinity and the visible light transmission was about 10% higher than that of tartaric acid and citric acid. It is significant for the low-cost production of CsxWO3 nanoparticles with higher transparent thermal insulation performance.

Transparent heat insulation coatings with high selective shielding ability designed with novel superstructures of copper sulfide nanoplates

In the present work, novel CuS superstructures composed of intersectional CuS nanoplates (CuS i-nanoplates) and snowflake-like CuS nanoplates (CuS s-nanoplates) were successfully synthesized at a low temperature (80 °C) by a simple chemical precipitation method. It has been found that the as-synthesized CuS superstructures were formed by the growth of CuS i-nanoplates along the direction perpendicular to the basal nanoplate with a thickness of 29.64 ± 3.16 nm and CuS s-nanoplates were prepared with the snowflake-like morphology with a thickness of 16.82 ± 3.62 nm. Subsequently, a new transparent heat insulation coating with CuS superstructures composed of CuS i-nanoplates as NIR shielding agent (coded as H–X coating) was prepared by mixing with acrylic-amino-alkyd baking varnish and coating to ordinary glass substrates. Simultaneously, another transparent heat insulation coating with s-nanoplates (coded as S–X coating) was also synthesized. Optical properties of those coatings were studied as a function of the CuS content by using ultraviolet–visible–near-infrared spectrophotometer. And the H–X coatings were shown to have a higher selective shielding ability for solar light than S–X coatings since the shielding ability of S–X coatings in the region of 1180–2500 nm rapidly weakened with increasing wavelength. The comparative study on the properties of nanomaterials with different morphologies in this paper may provide some new guidance for material design to improve its performance. Moreover, the CuS superstructure-based transparent heat insulation coatings with excellent NIR shielding property have a potential application in energy-saving windows for architectures and vehicles.

Polycarbonate multi-wall panels integrated in multi-layer solar façade concepts

Recent technological advances in transparent insulation materials’ (TIMs) production may have opened ways for new integration of these materials in buildings. This paper presents a study analysing several variants of façades incorporating TIMs on solar façade principles. The analysis is based on ongoing long-term full-scale experiments in Brno, Czech Republic. The paper introduces the test platform which is used for evaluation of specific aspects of integrated polycarbonate TIMs. The paper describes the experiment results, especially long-term thermal response and passive solar gain data. These data are applied for analysis of: influence of various polycarbonate-based TIMs on the real performance of the façades; influence of implementation of different solar absorbers on the performance of the proposed facades; effectivity of application of latent thermal energy storage (based on PCMs) as a part of heat accumulation layer and coupling of TIM with prismatic glass to enhance optical selectivity aspect. Presented results demonstrate for example significant influence of the type of solar absorber on the thermal performance of tested solar facades: the difference is up to 35% to 54%. Also the integration of prismatic glass coupled with simple two-wall polycarbonate panel can reduce solar penetration through components at the level comparable with the most complex six-wall panel.

Thermal insulation versus overheating - monitoring results

Initial design decisions regarding building external envelope may have important consequences for thermal comfort and total energy demand not only for heating but also for cooling. Before reaching for more energy-intensive solutions, effective use of passive measures to avoid overheating is necessary. In the article, special attention was paid to the influence of external wall structure on space overheating. On the basis of monitoring results it was found that the standard thermal insulation prevented excessive energy conduction into the space on very hot days and it should not be considered as a barrier for heat dissipation. The standard opaque wall was also compared with the uncovered transparent insulation, which is in summer an intensive source of energy gains. The basic dynamic characteristics of the monitored wall were analytically analysed by means of the periodic waves method.

Experimental study of solar powered ice maker using adsorption pair of activated carbon and methanol

The present study introduces an experimental work for a solar adsorption ice maker system (SAIMS) using working pair of activated carbon (AquaSorb 2000) and methanol. The isotherm and isobar characteristics of the used pair are investigated by using Dubinin-Raduskevich (D-R) equation then, the SAIMS is constructed and tested at real weather conditions of Qena, Egypt. The findings of the pairs reveal that it suitable for the solar adsorption ice making applications with adsorption capacity found to be 0.6935 kg of methanol per kg of activated carbon (AquaSorb 2000). The constructed SAIMS can produce about 0.4 kg of ice per kg of AquaSorb 2000 by using the acrylic sheets in the adsorption bed instead of glass or other bed covers. Also, the experimental results proved that by using the acrylic sheets with a good design of the adsorption bed and due to the enhancement of heat transfer and high adsorbent temperature, the mass of desorbed methanol and produced ice is increased. Therefore, both gross and net COP are improved in comparison with other previous studies with single, double and Transparent Insulation Material (TIM) in the adsorber.

Modeling and Optimization of Transparent Thermal Insulation Material

Radiative properties of transparent insulations made of a layer of parallel, small-diameter, thin-walled, visible light transparent pipes placed perpendicularly to the surface of a flat solar absorber are investigated theoretically. A formula for the radiation heat losses through the insulation is derived based on two main assumptions: the system is in steady-state and the fourth power of the temperature along each pipe is linear. Arguments in favor of the assumptions are given. The formula, combined with standard formulas for the conductive heat flux, enables prediction that a 10 cm thick transparent insulation under insolation of 1000 W/m2, at ambient temperature 20 °C, could theoretically raise the absorber temperature to 429 °C and produce 410 W mechanical power under the ideal Carnot cycle. In order to reach that high energy conversion efficiency, the insulation pipes should have diameter less than 0.5 mm and walls about 5 μm thick, which may be technologically challenging.

A Co-Precursor Approach Coupled with a Supercritical Modification Method for Constructing Highly Transparent and Superhydrophobic Polymethylsilsesquioxane Aerogels.

Polymethylsilsesquioxane (PMSQ) aerogels obtained from methyltrimethoxysilane (MTMS) are well-known high-performance porous materials. Highly transparent and hydrophobic PMSQ aerogel would play an important role in transparent vacuum insulation panels. Herein, the co-precursor approach and supercritical modification method were developed to prepare the PMSQ aerogels with high transparency and superhydrophobicity. Firstly, benefiting from the introduction of tetramethoxysilane (TMOS) in the precursor, the pore structure became more uniform and the particle size was decreased. As the TMOS content increased, the light transmittance increased gradually from 54.0% to 81.2%, whereas the contact angle of water droplet decreased from 141° to 99.9°, ascribed to the increase of hydroxyl groups on the skeleton surface. Hence, the supercritical modification method utilizing hexamethyldisilazane was also introduced to enhance the hydrophobic methyl groups on the aerogel’s surface. As a result, the obtained aerogels revealed superhydrophobicity with a contact angle of 155°. Meanwhile, the developed surface modification method did not lead to any significant changes in the pore structure resulting in the superhydrophobic aerogel with a high transparency of 77.2%. The proposed co-precursor approach and supercritical modification method provide a new horizon in the fabrication of highly transparent and superhydrophobic PMSQ aerogels.

Thermal behavior of a translucent superinsulated latent heat energy storage wall in summertime

This paper investigates the thermal performance of a translucent solar wall providing, concurrently, storage and restitution of heat, super thermal-acoustic insulation and daylighting to the interior environment. The wall is composed of glazing, silica aerogel used as a transparent insulation material (TIM) and glass bricks filled with fatty acid, an eutectic phase change material (PCM). To assess the TIM–PCM wall thermal behavior, experimentations were conducted in-situ in a full-sized test cell located in Sophia Antipolis, southern France. Experimental data shows that the tested wall is more effective in winter and might cause overheating during the summer mainly due to solar gains and un-cycling behavior of PCM which remains in liquid state. To enhance the energy performance of the wall in summertime, a numerical model describing the heat transfer mechanisms occurring in the PCM layer in combination with the other transparent wall layers is developed. Then, the model of the wall is linked to TRNSYS software to assess the thermal performance of the whole building. The numerical model is validated experimentally and a good agreement is shown comparing the simulated values with the measured data for seven consecutive days in summer and winter. The importance of considering the natural convection effect in the liquid PCM is also demonstrated. Moreover, it was shown that shading devices can effectively reduce overheating while natural night ventilation decreases the indoor temperature without affecting the PCM performance since the outdoor temperature is always higher than the phase change temperature. The use of a glass with selective solar reflection properties depending on the season instead of the ordinary glazing is shown also to be very effective way to overcome the overheating problem. Finally, the TIM-PCM wall is tested under different climate conditions and passive solutions are given to ensure thermal comfort in summer season.

Energy efficiency of the accumulation wall with a transparent insulation

This paper presents a numerical model of an accumulating solar wall with transparent insulation (ASW-TI). The objective of the simulation was to evaluate the energy efficiency of ASW-TI for different climatic conditions in Poland, i.e. for high, medium, and low irradiation. For each climate, the calculations were made for the entire heating period. As a result, temperature distributions in a wall at different times of the process and the energy balance of the wall in particular months and during the entire heating period were obtained.

Controllable synthesis of small size CsxWO3nanorods as transparent heat insulation film additives

Small size CsxWO3nanorods synthesized using pure ethanol as the solvent exhibited the best visible transparency and NIR shielding performance.