Charging faraway batteries through thin air

Rather than irradiate an area with electromagnetic waves, a power transmitter would fill surrounding space with a nonradiative electromagnetic field. Only items designed to resonate with the field would pick up the energy. The emitter would reabsorb most of the remaining energy.

Transmission ranges are proportional to receiver size; smaller receivers must sit closer to the power source. The team calculates that a laptop could recharge within a few meters of a power source. A source in each room would provide coverage throughout a home, for example. Wireless power systems could recharge batteries in household robotic vacuum cleaners or in freely roaming industrial robots on the shop floor.