Around 75% of buildings in the EU are energy inefficient and countries are now looking to modernize old buildings to avoid costly heat leakage. But despite the brainpower invested in making buildings more energy efficient, window design hasn’t used much modern technology until recently, says Ioannis Papakonstantinou, professor of nanoengineering at University College London, UK. His Intelglazing research project is using new ideas in nanotechnology and photonics (the physics of light) to create nanometer-thin window coverings that better insulate buildings.
This had been tried before in the industry, but all previous efforts were insufficient: they blocked too little sunlight or were too expensive to manufacture. “If you start mixing these (window) coatings with nanotechnology, you can push the performance limits to much higher levels,” he said. Intelglazing glass technology consists of two parts. The first is a microscopically thin layer of nanostructured glass shaped like tiny combs that are less than a micrometer (or a thousandth of a millimeter) high. These “nanocomb” structures overlap each other and scatter sunlight, reducing glare coming through the window.
The second part is where the windows become energy efficient. Here, the researchers are experimenting with a material called vanadium oxide, which can adhere to nano combs. This chemical compound is thermochromic, which means that it can change color depending on the temperature. For example, hot days will cause vanadium oxide to change its structure, causing it to darken and reject most of the warm near-infrared sunlight, while on cold days it will lighten and let most of it in. . Manufacturers can apply this coat directly to new windows as a glazing coat, or DIY modernizers can apply it to old windows as a polymer film adhesive coat. An added benefit of this, says Professor Papakonstantinou, is that manufacturers can customize windows or films with these layers to turn them on at a different temperature point. “You can change the chemical composition of vanadium dioxide so that it can change at a higher or lower temperature,” he said. “So you have good control.”
For example, windows in southern Spain could be customized to block sunlight at a lower temperature to prevent buildings from heating up during the day. Similarly, a building in northern Sweden will want to get as much heat from the sun as possible, so its windows might only start blocking sunlight at a higher temperature.
Hydrophobic
Windows with this layer of vanadium oxide and nano-fuels are also hydrophobic (repel water) – rain runs quickly down the glass and collects dirt along the way, causing the windows to self-clean. This makes windows more efficient when used in skyscrapers, for example. The goal of the project is for your windows to reduce people’s energy use by 25% by blocking or allowing sunlight when needed, and to be more than 50% more efficient compared to window technology. existing on the market, as no additional energy is needed to activate vanadium. oxide. In fact, window update technology has changed dramatically since the project began in 2016, says Professor Papakonstantinou. He says that when he first spoke of the project in the mid-2010s, nanotechnology in windows was unheard of, but now “the field has started to grow.”
Professor Per Heiselberg from Aalborg University in Denmark says that discussions about building modernization have been around for decades, although the environmental element has only been a priority recently. “It has been the issue for 40 years, but of course the argument has changed,” he said. In the 1970s, he says people were saving energy so as not to depend on Middle Eastern countries that had an oligopoly on the supply of oil. “Now the goal is to reduce carbon emissions and avoid greenhouse gases.” Professor Heiselberg’s ReCO2ST project looks for ways to modernize all surfaces that surround a building so that they are more cost-effective and environmentally friendly.
Ventilation system
A central feature of the project is the use of smart window technology to provide ventilation to modernized buildings, where the installation of modern ventilation systems such as air conditioners is difficult or expensive. “(A window is usually the) weak part of the envelope because it usually leaks and is not that well insulated,” he said. “On the other hand, it is also where we receive some heat from the sun in our buildings. The main idea is to use smart windows both to provide better shade from the sun and to supply fresh air to the building. This is especially useful for older buildings equipped with modern windows. Since these modern windows are more airtight, they can cause moisture and emissions to build up in the building, which could require another costly upgrade to the building’s ventilation system. “It can be difficult, especially in older buildings, to find space for pipes and ventilation systems to supply fresh air to spaces, and all spaces often have access to the outside through a window,” said Professor Heiselberg. ‘ It would be more cost effective if, instead of installing a new window and ventilation system, we used the window to supply fresh air, and then we used the chimneys or chimneys that you have in old buildings to escape the air.’ His smart window idea is based on research done in a previous EU project called CLIMAWIN.
In your triple glazed window frame there is a small gap (about 5mm wide) on the lower level outside. This space allows air to pass between the layers of window glazing and be warmed by sunlight. He then enters the room through a small valve at the top of the window that looks into the building. The result is a stream of fresh, preheated air through the window that can then be expelled from the building through another vent. Right now, the team is experimenting with different materials that can store latent heat in windows during the day and then release it at night, says Professor Heiselberg. “During a time when we have sun, we can collect it and store it,” he said. “And then we also have the possibility to preheat the air in periods when the sun does not shine.”
This material could also protect itself from the sun during the summer so that instead of storing latent heat, it cools the air that passes through it. Another idea being developed is to equip the windows with sensors to know the optimal time to store and release heat, and to add miniature fans to control the direction of the air flow. “Building renovation takes place all the time because the components have a certain useful life and must be replaced,” said Professor Heiselberg. “It’s important that when we do this, we do it in the most energy efficient way so that we don’t replace an old window with a new, low-performing window.”
Original article
This article was originally published in Horizon, the EU Research and Innovation Magazine
