Magnetic fields may open door to efficient wireless power
Cambridge (MA) - Scientists from the Massachusetts Institute of Technology (MIT) have demonstrated a new method to wirelessly transfer power from a power source to an electronic device. The MIT claims that the new approach may be efficient enough to even run notebooks over room-sized distances and decrease our dependency on batteries overall.
The idea of wireless power isn’t exactly new and has been discussed and even demonstrated fore more than 100 years. Nicholas Joseph Callan is recognized as the first person to have transferred power between two devices without using coils in 1836. However, wireless power has not become a feasible mass market application, mainly because of its inefficiency : Generally, wireless power is distributed via electromagnetic radiation, where radiation spreads in all directions, which mens that the vast majority of power ends up in free space and is wasted.
MIT researchers now say that they have found a new method to direct a wireless power stream into a specific direction. Their "WiTricity" ("Wireless elecTricity") method uses coupled resonant objects, which aims to create a scenario where two objects - the power source and the receiver - interact strongly with eachother, while there is weak interaction with everything else. The MIT project focused on magnetically coupled resonants, which revealed that this approach can identify the strongly coupled object in this system, even when the distance between them was several times larger than the sizes of the resonant objects.
According to a report published by the project group, magnetic coupling may be particularly suitable for everyday applications, "because most common materials interact only very weakly with magnetic fields, so interactions with extraneous environmental objects are suppressed even further." Considering the potential negative effects of electromagnetic radiation on biological organisms, a magnetically directed power stream could also alleviate the safety concerns around this technology.
In a first demonstration, the research group said that it was able to light a 60W light bulb from a power source seven feet away. The experiment setup used two copper coils - one attached to the power source (sender) and the other to the light bulb (receiver) - which both acted as self-resonant systems. The sending unit filled the space around it with a non-radiative magnetic field oscillating at MHz frequencies, which mediated the power exchange with the receiving coil. The scientists found that most of the power not picked up by the receiving coil remained bound to the vicinity of the sending unit and therefore did not get lost. The achieved efficiency was described to be sufficient to run a laptop over "room-sized distances nearly omni-directionally."
"As long as the laptop is in a room equipped with a source of such wireless power, it would charge automatically, without having to be plugged in. In fact, it would not even need a battery to operate inside of such a room," Prof. Peter Fisher of the MIT’s Department of Physics said. At least in theory, the experiment indicates that this technology could reduce our dependency on batteries one day.
The group did not say if and when their technology could be available on a commercial basis.