THE’AENEAS (the Italian agency for new technologies, energy and sustainable economic development) has patented a new one metamaterial who succeeds in cool an object or environment without heating. This is because it is able to reflect solar radiation and, instead of dissipate the heat In the surrounding environment, he sent it directly in space. As? Through a phenomenon called radiative coolingthat is, the sale of thermal energy by electromagnetic emission. The metamaterial uses a so -called atmosphere transparency windowthat is, an interval of electromagnetic frequencies that can easily cross our atmosphere until you reach the outdoor space. The material works without the use of electricity and manages to reach a temperature up to 12 ° C lower than the external temperature. Although it has not yet been proven outside, in the future it could be applied for new fabrics or for Thermal insulation of buildings.
How the Enea metamaterial works that uses passive radiative cooling
Innovation has as its protagonist metamaterialthat is, a material that is artificially produced by manipulating the structure of already existing materials in order to obtain some property non -existent in nature. In this specific case, some metal compounds have been configured in order to obtain unique optical properties, which seem almost to challenge the laws of thermodynamics.
The new material uses a phenomenon called radiative coolinga process in which a body gives heat to the surrounding environment (in fact, it cools) in the form of electromagnetic radiation, typically infrared radiation. The most common radiative cooling example is that of our planet. At night, in fact, without the sun that warms the part of the earth not turned towards our star, this gives up heat in the space in the form of infrared radiation. In this way the temperature decreases.
Just like the earth, the new material manages to cool down without dissipating heat in the surrounding environment but, rather, sending it directly into spacewhich is very cold. In this way the material manages to cool the environment without heating.
How the new material does to cool the objects without warming up
The metamaterial in question was developed to have two properties simultaneously: one high solar reflectance (i.e. the ability of a material to reflect sun radiation) and a high thermal emissivenessbut only in some intervals of wavelengths. To understand how the new material works we must first explain what the Atmosphere transparency windows.
We know that not all the wavelengths of the electromagnetic radiation of the sun manage to reach the earth and vice versa not all those emitted from the earth reach space. The wavelength intervals for which the atmosphere is transparent, allows the passage of electromagnetic radiation, are called “atmospheric windows”.

The new engineered material uses the passage of infrared rays In the interval of wavelengths included Between 8 and 13 microns (1 micron is a thousandth of a millimeter). To cool without heating, this metamaterial must therefore reflect all solar radiation except in this specific atmosphere transparency window. At the same time, always in this window interval, it must have high thermal emissiveness.
In this way the material manages to always reflect heat, except in the interval of the atmosphere transparency windowwhere it does not reflect heat but emits itand can therefore send it into the universe. These properties work thanks to the presence of spectrally selective surfaces, which emit or reflect infrared as it is better.
How this Italian metamaterial is produced
The material is produced with a process called sputteringthat is, a deposition of the material on adhesive surfaces. In the experiments carried out, the material was deposited on a metal substratethen protected by a transparent envelope in order to create a room in which the metamaterial was isolated.
In our eyes the object of the experimentation appears as a kind of rectangular box that seems empty, but is made with acrylic slabs and filled with kryptona noble gas that serves to minimize the heat convention.

Through the use of software, the refined optical properties were simulated, which then suggested in what order to lay down the materials involved. These are compounds ofsilverlayers of aluminum nitride, aluminum oxidesilicon nitrurize and the like. In short, all already existing materials but that, arranged in an unprecedented way Through the deposition process, they have acquired new properties in their new configuration.
From the first assessments of the performance, ENEA declares that the new metamaterial manages to maintain a lower temperature than the surrounding one, obtaining a temperature differenceand therefore cooling the environment, up to 12 ° C less.
Possible uses of the new metamaterial of Enea
The main advantage of the new material is that it is a method of passive coolingwhich does not use energy to cool the environment (unlike the operation of an air conditioner). The invention, after the appropriate developments, could be used to cool buildings, but also for food and fabrics or for industrial plants. We start thinking about the deposition of the layer of metal compounds on walls or on Facials of the buildingsor alternatively it could be something to integrate with a fan coil.
Meanwhile, Enea continues her experimentation; the material has yet to be tested out of the laboratory. Other experiments concern the exposure of the material to the direct sunlight And the evaluation of its performances, as well as its operation without the presence of noble gas. The project is far from being applied but it could certainly be impactful with a view to the contrast to global warming.