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Intelligent functional glazing with self-cleaning properties to improve the energy efficiency of the built environment

Periodic Reporting for period 3 - IntelGlazing (Intelligent functional glazing with self-cleaning properties to improve the energy efficiency of the built environment)

Reporting period: 2019-03-01 to 2020-08-31

The latest forecast by the International Energy Agency for the CO2 emissions of the built environment portrays a gloomy picture. It is anticipated that those emissions will reach 15.2 Gt in 2050, double their 2007 levels. Rapid urbanisation and economic development is the driving force behind this growth. Buildings consume 40% of the primary energy in developed countries with heating and cooling alone accounting for 63% of the energy spent indoors. These trends are on an ascending trajectory - the energy demand for air conditioning in the EU has been growing by 17% per year on average, for example. Counterbalancing actions are urgently required to impede the above trends.

The objective of this proposal is to develop intelligent window insulation technologies that will deliver unprecedented savings to the energy needed for regulating the indoor temperature of commercial, residential, industrial and public buildings. Recognising the different requirements between newly built and existing infrastructure, two parallel concepts are developed in this ERC project: i) a new class of highly-performing, energy-saving glazing for new window installations, and, ii) a flexible, polymer film to retrofit existing window installations and convert them into energy-saving surfaces. Both solutions are enhanced with unique self-cleaning properties bringing about additional economic benefits through a substantial reduction in maintenance costs and environmental benefits by removing the need for cleaning chemicals. The proposed technologies are planned around sustainable materials and scalable engineering processes intended to shorten the path from the laboratory to the market. IntelGlazing will culminate in large scale prototyping and outdoors testing to objectively assess the potential of the developed technologies under real environmental conditions.

The functional material underpinning the proposed intelligent glazing is vanadium dioxide, a sustainable thermochromic material that responds reversibly to the ambient temperature. During hot periods, our developed products will reject the majority of the Sun’s infrared radiation, significantly reducing the requirements for air-conditioning. In cold periods, the windows will be transparent at both visible and infrared (IR) wavelengths from the Sun while they will not allow the thermal energy generated inside the building to escape. The need for heating will thus be reduced. This is a generation beyond existing static solar control glazing products like low-E coatings, which transmit a constant amount of infrared radiation throughout the year. Such static products are not optimum for energy saving purposes as, for example, on cold periods the rejected IR energy should ideally have been used to heat up the buildings’ interior. Some dynamic glazing technologies do already exist. However, our proposed thermochromic technology has a significantly lower cost, zero-energy consumption and is fully compatible with modern window installations. Furthermore, visible transmission is maintained for our thermochromic windows, this is not the case for some other technologies.

Overall, we aim to develop intelligent insulation technologies that combine: i) power savings of >250 W/m2 of glazing capable of delivering >25% of energy efficiency improvements in buildings and efficiency improvements >50% compared with existing solutions like low-emissivity coatings; ii) visible transparency of >60% to comply with the strictest EU standards for windows; iii) hefty energy savings delivered during both hot and cold periods, as opposed to current technologies that only save energy during a single period, and, iii) self-cleaning properties that introduce a cost balance and do not interfere with the windows’ main functionality. Intelligent glazing insulation with such unique features and high specifications exists neither in the market nor at experimental stage in laboratories. A number of technological breakthroughs are required to develop a viable solution, which are delivered in this project by the seamless integration of nanotechnology engineering, photonic innovations, advanced material synthesis and thin-film deposition and large-scale, high-yield manufacturing processes.
During the first phase of the project we focused on developing the underpinning technologies and know-how that will allow us to create the smart windows with the targeted functionality and performance. More specifically, we made advances in the following areas:

- We have developed scalable and cost-efficient nanofabrication processes to fabricate anti-reflective structures on a number of technologically relevant substrates that include glass, semiconductors and popular in architecture plastics. This technology can find application in areas beyond smart windows that include displays, aviation, industrial plants and elsewhere.

- We have developed multiple pathways to depositing thin-films of thermochromic material (vanadium dioxide), the basic constituent of our smart windows. These methods are converging to industrially used processes which may facilitate their translation into real-life products in the near future.

- We have started developing the processes to deposit ultrathin-films of vanadium dioxide on irregular surfaces decorated with antireflective structures. This will allow true multi-functionality to be embedded in our windows.

- We have developed recipes to produce thermochromic nanoparticles of controlled size that will be used to produce the smart polymer foils.

- We have started investigating how to embed the thermochromic nanoparticles in polymer foils.
We anticipate the following main outputs from our project:

- The first output will be a next generation, multifunctional smart glazing. Our windows will be self-cleaning and will be able to modulate the solar heat gain passively. We are also aiming to enhance the durability of our product by developing appropriate protective layers as we aim to be as close as satisfying the stringent building regulations in the EU for window lifetime as possible.

- We aim to have our windows subjected to extensive accelerating testing as well as monitor their performance under real environmental conditions. These fundamental tests will be coordinated with our industrial partners and will provide us with essential information on the applicability and practical aspects of the developed technology

- The second output will be the development of a smart, thermochromic foil that will be used to retrofit existing window installations. This will be a product which may require more frequent replacement but will be very cost efficient and will have significantly shorter payback times.

As secondary outputs we expect the following:

- We will develop a scalable method to fabricate antireflective and self-cleaning nanostructures compatible with existing industrial processes. These nanostructures could find wide usage and be tailored to different applications including self-cleaning, anti-glare screens and displays, surfaces that reduce drag, surfaces that delay ice-formation, surfaces that prevent water condensation and other.

- We will develop processes to conformally deposit ultra-thin layers of functional coatings. Apart for energy efficiency purposes, these processes can be used in a great variety of other applications like for example surface enhanced raman spectroscopy, antibacterial-antimicrobial surfaces, surfaces that prevent bio-fouling and other

- We will develop methods to increase loading of polymer host material with metal-oxide nanoparticles. These methods will be generic enough to be able to work with other materials and hence by relevant to a number of industrial applications.