MIT researchers demonstrate 'WiTricity'

Stephen Withers
Friday, 08 June 2007 03:50

Science - Energy

A team of scientists at the Massachusetts Institute of Technology have demonstrated a wireless power transfer scheme they have dubbed 'WiTricity' or wireless electricity.

While the demonstration was of a 60W globe being powered from a source over two metres (seven feet) away, a more popular application could be to recharge electronic gadgets such as mobile phones, making them truly wireless.

A key point is that WiTricity does not use electromagnetic radiation, which would be inefficient and possibly hazardous. Instead, it relies on magnetically coupled resonance which gives efficient energy transfer and interacts very weakly with most common materials including living creatures. "The fact that magnetic fields interact so weakly with biological organisms is also important for safety considerations," said researcher Andre Kurs.

The system uses a pair of copper coils. One generates a magnetic field oscillating in the megaHertz range, and the other resonates with that field and converts the energy back into electricity. In comparison with magnetic induction (as used in electrical transformers), resonant coupling remains efficient when the two coils are not very close together.

"The crucial advantage of using the non-radiative field lies in the fact that most of the power not picked up by the receiving coil remains bound to the vicinity of the sending unit, instead of being radiated into the environment and lost," said team member Robert Moffatt, an MIT physics student.

One drawback is that a smaller receiving coil means a shorter range. According to the researchers, a notebook sized coil can receive more than enough power to run the computer within the same room as the transmitter.

The project, inspired when team leader Professor Marin Soljacic repeatedly forgot to recharge his mobile phone, was funded by the US Army Research Office, National Science Foundation and Department of Energy.