An invisible "curtain" of nanocrystals on the glass surface will allow you to arbitrarily block the rays of the visible spectrum and/or infrared rays. But before the new miracle material can be put into practice, scientists still have a lot of problems to solve.
To keep the building not only cool, but also bright, you have to spend twice as much energy in summer. In order to avoid heating the rooms and additional load on the air conditioning system, it is necessary to equip the windows with shutters or curtains. But with the shutters closed, we have to work somehow, and that's why we use artificial light. Again, electric.
American materials scientists have found one of the possible solutions to significantly reduce energy costs. A group of scientists led by chemist Anna Lordes from the Lawrence Berkeley National Laboratory published an article in the specialized journal Nature in which they demonstrated that glass coated with nanocrystals coated with a new technology can operate in three arbitrarily switchable modes.
The first mode lets most of the light through. The second mode blocks only infrared rays, without interfering with the penetration of visible light: the heat remains outside, the air conditioners can be turned on at a lower power. In the third mode, visible light is also blocked: the room not only remains cool, but also becomes "shady".
The darkening of the glasses can be achieved thanks to current-sensitive metal oxides - it is enough to change the voltage. Other parts of the light spectrum are initially cut off by glass: "Our crystals do not allow ultraviolet rays to pass through in all modes," says project manager Delia Milliron.
To obtain innovative materials, the researchers mixed nanocrystals of indium tin oxide (ITO) and niobium oxides. „We placed the crystals and their compounds in an aqueous solution, after which we applied it to glass with a conductive layer and heated it," explains Milliron production process. As a result, the crystals changed their properties and grouped into niobium compounds.“
Questions about the energy balance
Interestingly, the properties of glass using combined materials turn out to be even better than one would expect given the characteristics of the materials themselves. Scientists attribute this to nanostructures and improved particle recharge in the "cocktail" of materials. During the experiments, it turned out that niobium oxides in composite materials provide almost five times more effective dimming than individually.
The development of miracle windows is just beginning, but in the future it may allow separate control of the penetration of light and heat into apartments and offices. It is possible that smart windows will change transparency arbitrarily depending on the settings. And we will save on heating, lighting and air conditioning of the premises.
But before the time when new glass can be used for the production of windows, researchers still have many problems to solve. At the moment, they use lithium electrodes, an easily flammable and active metal that needs to be replaced for safety reasons. In addition, it is necessary to find out how long the glass will be able to retain its properties. So far, the material has proven to be very stable with about 2,000 on/off switches during experiments.
Again, it is difficult to say what the situation is with the energy balance. It is clear that innovative windows will cost more than conventional ones. But additional surpluses must be offset by energy savings, otherwise there will simply be no point in know-how. "Ideally, new windows should remain transparent or impervious to light without constant energy supply," Brian, a nanomaterials researcher, writes in the journal Nature. But how realistic this is remains to be seen.
"It is still premature to talk about practical application. It will take a lot of work: it is necessary not only to enhance the effect, but also to create prototypes, as well as to think over the issues of industrial production,“ explains Delia Milliron. In the meantime, the most effective way to protect an apartment from the summer sun is to close the curtains. Check out CCTV Rush Hour for fast-paced fun.