A team from MIT has experimentally demonstrated an important step toward wireless power transfer for cell phones, household robots, mp3 players, laptop computers and other portable electronics.
They transfered 60 Watts over distances in excess of two meters, with approximately 40% efficiency. They’re calling it Wi-tricity — short for “wireless electricity.”
The team used two copper coils, coupled mostly through their magnetic fields. One of the coils, attached to the power source, is the sending unit. It emits a non-radiative magnetic field oscillating at MHz frequencies. The receiving unit is designed to resonate with the field. The resonant nature of the process ensures efficiency, while the interaction with the rest of the environment is weak, claim the researchers.
The team leader, Professor Marin Soljacic, got the idea while standing in his pajamas, staring at his cell phone. As he told the MIT News:
“It was probably the sixth time that month that I was awakened by my cell phone beeping to let me know that I had forgotten to charge it. It occurred to me that it would be so great if the thing took care of its own charging.” To make this possible, one would have to have a way to transmit power wirelessly, so Soljacic started thinking about which physical phenomena could help make this wish a reality.
The team believes an object the size of a laptop could be recharged within a few metres of a wireless power source. It could mean the end of cords for laptops, cell phones and iPods — and more headaches for the tin foil hat brigade.
