While there's been no shortage of attempts to incorporate wireless power transmission technology into our furniture, garages and living rooms, reality has not quite caught up with the futuristic ideals of untethered wireless freedom. That said, we might be inching closer to it with Disney Research's recent demonstration of a new method for wireless power transmission that could charge your devices automatically the moment you walk into a room, making electrical cords and charging cradles a thing of the past.
At present, wireless charging is stymied by two challenges: range and health concerns. Despite their reach, radiative transfer methods, which are used for radio communication, have not found much favor elsewhere due to health and safety concerns. On the other hand, while safe, non-radiative methods such as near-field coupling are highly localized and require the devices to be placed near the charging source.
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To circumvent these limitations, Disney Research scientists, led by associate lab director and principal research scientist Alanson Sample, turned to a method called Quasistatic Cavity Resonance (QSCR), which induces electrical currents in an enclosed metallic structure. For the purposes of this proof-of-concept, the researchers constructed a 16-by-16-foot room with aluminum walls, ceiling and floor bolted to an aluminum frame. A copper pole, with a small gap into which discrete capacitors were inserted, was placed in the center of the room.
A signal generator located outside the room produces a 1.32 MHz tone, which is given a boost by a power amplifier. A coil receiver then connects this signal to the capacitors in the pole and this system enables power to be transmitted to receiving coils that operate at the same resonant frequency as the magnetic fields. By channeling the induced currents that flow through the walls, ceiling and floor in the room, the capacitors set the electromagnetic frequency of the structure and confine the electric fields, isolating potentially harmful electrical fields at the same time.
On a separate note, because of the way the magnetic fields swirl around the pole, the device has to be situated perpendicularly or orthogonally to the magnetic fields to receive power. If the receiver coil is parallel to the plane, it receives no power, which defeats the idea behind this project since the point is to enable people to charge their devices anywhere in the room. To get around this issue, the researchers came up with a receiver design with three orthogonal coils so at least one of them would be able to receive power regardless of where it's located.
"This new innovative method will make it possible for electrical power to become as ubiquitous as Wi-Fi," says Sample, adding that it could in turn "enable new applications for robots and other small mobile devices by eliminating the need to replace batteries and wires for charging."
Though the room had to be custom-built for this study, Sample believes the need for such metallic surfaces will be significantly reduced once the QSCR technology is optimized. Building owners will then be able to retrofit existing structures via modular panels or conductive paint, and in the case of larger spaces, by inserting multiple copper poles.
One advantage this method is said to offer is that since the coupled resonators only share energy with devices of the same resonant frequency, these low megahertz frequency magnetic waves have little effect on common everyday materials – unlike low frequency inductive systems that result in eddy current heating – thus allowing for home and office furnishing to be included in the room. In addition, the high Q-factor and sub-wavelength operation of the QSCR room allows for the inclusion of windows and doors without any significant impact on system performance.
Now for the 64,000 dollar question: will being in this room fry your brain? While the researchers ensured the study was conducted according to Federal safety guidelines, there are a few things worth pointing out. First, there is a limit to the amount of power you can pump into the room. As the authors note in their study, while it is possible to safely transmit 1.9 kilowatts of power to a receiver at 90 percent efficiency (the equivalent of charging 320 devices), due to the amount of unused power stored in the room, the appliances in the space would have to use and receive that much power.
Secondly, while around 100 watts of power can be transmitted into the room safely, there would need to be a significant amount of utility taking place. For larger amounts, standard methods such as real-time power tracking can be used to ensure safe operation. Finally, as per SAR (specific absorption rate) requirements, safety strategies such as intrusion detection or a decorative wall would need to be employed to ensure that people do not venture within 46 cm of the pole.
Though work on this project is still in its nascent stage, the researchers believe this form of wireless power has the potential to eliminate the need for wires and batteries by enabling users to charge their devices simply by walking into a QSCR-enabled space, thus allowing an unprecedented amount of spatial charging freedom. One interesting advantage it has over other solutions we've covered is that it can be scaled to size, depending on the application. The researchers did not mention what plans Disney has for this technology but one can imagine how it can be used in its theme parks, for starters.
"In this work, we've demonstrated room-scale wireless power, but there's no reason we couldn't scale this down to the size of a toy chest or up to the size of a warehouse," concludes Sample.
Watch the video below to see how QSCR-enabled wireless power transmission works.
The study was published in PLOS One.
Source: Disney Research