INCREASING THE RANGE OF WIRELESS POWER

Current wireless power transfer (WPT) systems, the system that allows for wireless electricity, remain limited to charging cradles for phones and other gadgets.  It is little more than a niche feature for a limited range of electronics, rather than the norm.

Moreover, because of the need to keep the gadget on top of the charging pad, its functionality is hampered. If you move the gadget away from the pad, you don’t get any power. So why not just have it plugged in? At least the wire gives you some range of movement.

Even the latest commercial technology is only capable of extending that wireless charging range to a maximum of 5 meters.

Part of the thing preventing any mainstream adoption of wireless power technologies is that transferring power across air (rather than through cords and wire) is an inefficient process. When MIT scientists powered up a 60-watt light bulb from a distance of two meters to demonstrate the feasibility of WPT, they were only able to do so at 45% transfer efficiency.

Now, researchers at Giricond Research Institute, both in Saint Petersburg, Russia, have developed a new WPT system that allows for better transfer.

(Left) Illustration and (right) experimental setup of the wireless power transfer system. Power is transferred from one ceramic sphere to the other using the spheres’ identical magnetic resonance. Credit: Song, et al.

In their study published at Applied Physics Letters, their proposed system is able to maintain an 80% transfer efficiency and sustain that across a distance of 20 centimeters with little loss associated with further distance. It is also able to operate when the power transmitter and receiver is in misalignment with an efficiency of 70% at 90 degrees misalignment, meaning that the transmitter and receiver are not facing each other at all.

This WPT proposal is based on resonance coupling similar to that of other proposals. Resonance coupling functions by inducing two copper coils to resonate at similar frequencies, allowing energy to transfer between each other. This is often accomplished via magnetic fields to ensure that magnetic fields from sources like the human body do not interfere with this frequency and prevent energy transfer.

FROM THEORY TO REALITY

What allowed the researchers to accomplish this higher efficiency is the use of “high-permittivity low-loss dielectric resonators” instead of the copper coils. This new material had a higher refractive index which allows it to slow down an electromagnetic wave travelling across them. By doing so, this allowed the receiver and transmitter in the WPT system to have stronger resonances and develop frequencies closer to that of each other and increase efficiency.

They were also able to develop a workaround for the problem of orientation by using a higher-order resonant frequency mode. While previous WPT systems utilized magnetic dipole mode, their proposed system used magnetic quadrupole instead that allowed it to not only decrease radiation loss of energy but also to make the system less sensitive to orientation between the transmitter and receiver.

The researchers assert that their next step in research is to figure out how to improve the sensitivity of the receiver to orientation and reduce the size of the resonators for practical use. With this, the world is one step closer to Nikola Tesla’s dream of wireless electricity.


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