Definition

resonance charging

Resonance charging is a wireless charging method for items that require large amounts of power, such as an electric car, robot, vacuum cleaner or laptop computer. The method works over small distances (3-5 meters).

For centuries, scientists have known that resonance causes objects to reverberate when energy of a certain frequency or pitch is applied. In resonance charging, two copper coils are used. One coil, attached to a power source, is the sending unit. The other coil, attached to the device to be charged, is the receiver. Both coils are tuned to the same electromagnetic frequency. When objects of the same resonant frequency are placed close to one another, the energy produced can be transferred from one to the other. Researchers have been studying the potential of "non-radiative" objects with what they call "long-lived resonance." When an electromagnetic field is activated between these objects, the energy produced remains fixed in these objects, rather than being dispersed in space.

The idea of using lasers to wirelessly charge objects was considered. However, it is not very practical as lasers require an unobstructed line of sight and can also be dangerous. The energy produced between objects with long-lived resonances has little to no effect on the environment or biological organisms, making this method of charging much safer.

Here's an example of resonance charging used to deliver power to the battery of an electric car: The garage and car would both be equipped with copper coils. The garage would contain the transmitter, while the car would be equipped with the receiver. The transmitter supplies the room with a non-radioactive magnetic field. This field will adjust the power transfer, producing a powerful correlation between the sending and receiving unit and, as a result, delivering a charge to the car's battery.

Power transfer between the sending and receiving unit can be effectively achieved regardless of room geometrics or whether other objects are placed in the middle of the coils. Other electronics in the vicinity of the sending and receiving units will not pick up on the power transfer, as long as they are not tuned to the same electromagnetic frequency.

Resonance can also be used for wireless power rather than wireless charging. For example, a laptop equipped with a receiving unit and in the same room as the sending unit could receive an automatic charge as a constant flow of energy and not require the use of its own battery.

This was last updated in March 2008
Posted by: Margaret Rouse

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