MIT researchers have found a (theorical) way to wirelessly charge portable devices.

The main technology is already known as "inductive coupling": the current is passed through wires of the "charger" part of the system, producing a magnetic field that induces a current in the wires of a nearby portable device. This device has to be at maximum 5 meters of the charger.

The idea which seems to be the solution to the problem we first imagine, i.e. the radiation and the energy loss .. the idea, then, is the resonance and the use of low-frequency electromagnetic radiation between 4 MHz and 10 MHz. The receivers are resonating at an identical frequency than the transmitters (chargers) and obstacles should not decrease the efficiency of the transfert. The non-used energy is recovered . By who, that's another story, since the idea is just theorical for the moment. A prototype could appear in one year. Researchers are now thinking about a unique charger in the ceil, that would distribute energy to all devices in the house.

MIT suspects that people will be uneasy at first about having electricity being transmitted through the air but explains that while the electric field could be harmful for humans, the magnetic field would be a lot safer .


Source: Technology Review, tuesday.

For those who do not know:
- Wireless energy transfert already exists in such a manner, in particular with the passive RFID tags and the phone SplashPad of SlashPower.

- A magnetic field is that part of the electromagnetic field that exerts a force on a moving charge. A magnetic field can be caused either by another moving charge (i.e., by an electric current) or by a changing electric field.
- The space surrounding an electric charge has a property called an electric field. This electric field exerts a force on other charged objects. The concept of electric field was introduced by Michael Faraday.
==> (*) Charges do not only produce electric fields. As they move, they generate magnetic fields, and if the magnetic field changes, it generates electric fields.