Projects / Programmes
Thermo- and Photo-Active Coatings for Windows
| Code |
Science |
Field |
Subfield |
| 2.03.03 |
Engineering sciences and technologies |
Energy engineering |
Renewable resources and technologies |
| Code |
Science |
Field |
| T155 |
Technological sciences |
Coatings and surface treatment |
| Code |
Science |
Field |
| 2.03 |
Engineering and Technology |
Mechanical engineering |
sol-gel technology, thermochromic and photocatalytic coatings, energy efficient window, "green" window, structural, optical and functional properties
Researchers (23)
Organisations (5)
Abstract
Nowadays, a great amount of energy is consumed for heating and cooling of buildings. Windows remain the weakest point in terms of heat losses and therefore there is a strong need for further improvement of existing windows by applying new coatings that enable smart light and heat management (variable VIS transmittance, low emissivity, IR modulation, UV-cut, glare reduction and self-cleaning features).
In this proposal, we will focus on the synthesis of new materials based on transition metal oxides as functional coatings on glazing surfaces to make “green” windows: environmental and energy efficient. To this aim, we formed several research directions to accomplish our goals: (i) preparation of thermochromic coatings on glass and plastics, (ii) preparation of photocatalytic coatings on glass and plastics and UV-protective coatings on wood, (iii) their application in design and modelling of a window, (iv) exploring their physicochemical properties in order to relate them with functional characteristics of a window – illumination and thermal comfort, pollutant removal, self-cleaning, self-sterilizing and anti-fogging surface.
Preparation of coatings will be based on a low-temperature sol-gel method and the use of pigment dispersions. For the construction of “green window”, we will originate from a line of windows “Nature Optimo XLS” of M SORA manufacturer while new functional elements will be added to windows. Coatings with a high optical transmission and desired thermochromic (TC) and photochromic (PC) exhibited on a laboratory scale with be used.
TC effect will be achieved with coatings based on VO2, which enables modulation of the coatings`s transmittance and reflectance in the near infrared and thermal infrared spectral range, depending on the temperature. The temperature of the phase transition of TC coatings from semiconducting (NIR and IR transmitting state) to metallic state (NIR absorbing and reflecting state) will be adjusted by introducing various dopants to VO2 (W, Mo, etc.), while addition of Mg will increase their transmittance in the visible part of the solar spectrum and the alternation of the whole solar transmission during phase transition. Preparation of the pigment dispersions will be done by milling of VO2 pigments in the presence of various dispersants, following already known routes.
PC effect will be obtained with TiO2 based coatings, which under solar illumination catalyze pollutants degradation and enhance their removal due to photoinduced superhydrophilicity on the surface of the semiconductor. Synthesis route is based on the preparation of the acidic aqueous sol with a silicate binder. UV-protection effect for wooden window frame will be based on preparation of pigment dispersions from UV absorbers, such as TiO2, CeO2 or ZnO. Solution or dispersion formulation will be optimized for three types of surface. When using plastic surfaces, possible degradation of the substrate will be prevented with additional intermediate protecting layer or with deposition of a gradient coating.
Structural, mechanic and functional properties of the prepared coatings will be determined with different methodologies, mastered among project partners. An understanding the role of glazing components on window light transmittance and heat balance will be obtained by computer modelling. Model calculations will be compared with experimental results of Uw value determination on a test wall (MSR-ECO-500 IFT Rosenheim). The testing wall enables us to define thermal transmittance through the window and to measure local temperatures on the window considering different climatic conditions. Collaboration of four different Slovenian research institutions (UNG, KI, FKKT, FGG), foreign research groups and Slovenian window manufacturer M SORA d.d. gives a solid base for a successful execution of the project tasks with the aim to produce even more energy efficient “green” window.
Significance for science
Sol-gel coatings have not reached state of development, which should allow their wide spread applications and mostly coatings based on organic polymers are used. Practical use of coatings with embedded well defined nanoparticles are also not widely spread, since they are hindered by the fact that agglomeration and flocculation of the nanoparticles are difficult to prevent without using effective dispersants. This project proposal therefore represents a step towards application of sol-gel technology in an important area of energy efficient building elements. Furthermore, sol-gel coatings with the incorporated nanoparticles will be derived from the water-borne systems. The outcomes of the proposed project will be easily transferable to other fields and applications, where thin, durable, optically transparent coatings are needed. Typical examples are glazing for solar thermal collectors, photovoltaic modules, etc.
Significance for the country
In Slovenia, total turnover in windows industry annually reaches impressive 350 mil Euros. This amount of money is obtained by selling relatively simple, standardized windows made of plastic or wooden frames and glass panels. Even though windows standards in Slovenia increase, we may even say that in worldwide scale we are on the top. 80% of customers are still buying standardized windows; wooden windows with 68 mm thick window profile with triple glazing (Ug ( 0,7 W/m2K). Worldwide, these characteristics represent superior and low energy windows. Because of customers' demands for intelligent windows solutions, each year quality level of windows is increasing. Competition of European companies causes classical windows getting hard to sell. Slovenian companies are on the top of European windows production industry, and for high windows quality production they use latest materials and technology. We are aware of the fact that only with development and investment in the new solution and improvement of each window component we can maintain market share and full production in the future.
Efficient cooperation among different laboratories and industry represents an important factor for development of practically used products with high added value originating from development of new functional materials based on nanoscience. Undoubtedly, this is what we will achieve in this project; UNG, KI and FKKT focus on fundamental research, development of materials, their characterization and production of functional nanostructured coatings. Knowledge of using functional coatings as active layers in windows construction will be obtained by model calculations created at FGG. Collaboration of these partners will ensure proper knowledge and materials background for M SORA company, for building lighter and more energy efficient windows, which will provide intelligent control of the light flow inside the building (and heat in the opposite direction) and at the same time will have self-cleaning ability. Synthesis of different nanostructured materials in a big extent is foreseen, and it will be done in order to enable production of coatings in sufficient amount (fine chemical syntheses) for production of smart glazing which will be used in M SORA normal sized windows at the final phase of this project.
Successful development of self-cleaning and other nanostructured coatings is a big step forward in use of intelligent and transparent surfaces on buildings envelope. That will enable better and easier use for the customer. Coatings of high potential should attract major manufacturers of glasses in Slovenia and Europe. Epilogue of the project will be short presentation of products to at least five glass manufacturers in Europe, and gaining their feedback on the products could lead to new industrial projects and cooperation.
Most important scientific results
Interim report,
final report
Most important socioeconomically and culturally relevant results
Interim report,
final report
