Most of the sunlight that hits the Earth is absorbed by its surfaces, oceans and atmosphere. As a result of this warming, infrared radiation is constantly emitted around us.
Estimated in millions of gigawatts per second, this residual infrared radiation is able to supply the energy demand of humanity thousands of times.
A team from Rey Abdalá University of Science and Technology, in Saudi Arabia, has developed a device that can take advantage of this energy, as well as the residual heat of industrial processes, and transform it into useful electricity.
Unlike solar panels that are limited by daylight hours and weather conditions, infrared heat can be collected 24 hours a day. One way to achieve this is to treat the excess infrared heat as high frequency electromagnetic waves.
Using antennas designed specifically for this research, the collected electromagnetic waves are sent to a rectifier, typically a semiconductor diode, which converts the alternating signals into DC load for batteries or electrical devices.
The process is achieved by the manufacture of a rectenna or rectena, ( rectifying antennaor antenna rectificadora), a special type of antenna that is used to directly convert microwaves into direct current. In this investigation, since the length of the infrared waves is extremely short, in order to take advantage of them it was necessary to build really tiny rectenas.
In addition, infrared waves oscillate thousands of times faster than a typical semiconductor. “There is no commercial diode in the world that can operate so frequently,” explains Atif Shamim, KAUST project leader, in a statement . That’s why they have used the tunnel effect.
The tunnel effect is a quantum phenomenon that allows a particle to overcome a barrier that in theory could not pass through due to lack of capacity. For example, a bullet fired from the base of a mountain needs a certain amount of energy to reach the top and reach the other side. But a quantum bullet can not: it can reach the other side of the mountain thanks to the indeterminacy of its position, which is the basis of any quantum phenomenon.
Well, that tunnel effect, according to the researchers, can help to build the aforementioned nanometric antennas and obtain energy from nature: electrons can cross a small barrier, thanks to a diode governed by the tunneling effect (Metal-Insulator-Metal) , and transform the infrared waves into electrical current.
Nano-antenna with diode
They have verified it by constructing a nano-antenna in the form of a butterfly that incorporates a very thin insulating film between two metallic arms slightly coated with gold and titanium.
The invention is capable of generating intense electric fields, necessary for the proper functioning of the nano-antenna. The MIM diode has successfully captured infrared radiation and only turns on when necessary.
And although at the moment it is only a stage of the innovative process successfully overcome, there are still many technical problems to be solved before the viability of the device can be confirmed.
One of the problems to solve is that it consumes a lot of energy, but if the investigations are carried out as planned, it will be possible to connect millions of micro-antennas to increase the production of electricity in a country or region. A whole revolution for the energy sector.
It is not the first time that you try to obtain electricity from the electromagnetic spectrum. In 2014, North American researchers tried it with a “emissive energy collector” and also with rectenas, as they explained in an article published in PNAS.