Wireless energy transfer comes in many forms. One form already used in the consumer market. "Induction," as in cell phone charging mats or the Palm Touchstone system, have been available for years. Also known as Electrodynamic Near Field Method, the idea here is to generate a small electromagnetic field in a primary coil. Once the secondary coil in brought within that field a current is induced. The main issue here is that distance, even fractions of millimeters, will greatly reduce the efficiency of the power transfer.
Palm Pre on the Palm Touchstone inductive chagning station
Nikola Tesla was the first to invent and demonstrate the aspect of using wireless energy. He could illuminate a light bulb, seemingly by magic, yards away from his Tesla Coil. I know child’s play right? You have to remember though that was done in the mid to late 1800’s when light bulbs were just being invented. Tesla's famous, now somewhere mythical, demonstrations of wireless energy transfer is called the "Electrostatic Method" or Capacitive Coupling. An electric field of alternating current, high potential, high frequency is generated across a ground plane. The sending conductor (primary) must have a matched frequency receiving conductor (secondary) in order to maintain high efficiency in energy transfer. And if several devices are tuned to the transmitter, they can all tap off the power. I have over simplified the concept, so read more here if you wish: http://www.teslatech.info/ttmagazine/v1n4/valone.htm
Tesla demonstrating wireless energy transfer
Now another Croatian scientist aims to implement the idea of wireless transfer of electricity for use in charging our gadgets. Marin Soljacic, an Associate Professor of Physics at MIT, learned that if you could get two magnetic fields to resonate -- to sing the same note, in effect -- they could transfer an electric current. With two large magnetic coils, he found, you can throw 60 watts across a room, powering a light bulb. The constant need to power our many devices have inspired the MIT researcher to bring Tesla's concepts to practical market. Soljacic spent several years running lab experiments before he built a system that worked reliably using two resonators. After patenting his technology he went on to start a company called ‘WiTricity’ that’s hard at work proving that Soljacic's magnetic coils can power almost any electrical device. However the design being used is rather too bulky and needs to be scaled down to be able to fit inside the gadgets themselves. Now in steps the company "Witricity." In July of 2009 Eric Giler, CEO of the US firm WiTricity, at the TED Global Conference held at Oxford, demonstrated a 60 watt light bulb being powered at 7 feet from a transmitter. Even when the direct line of sight was blocked, the bulb was still powered. In this case the transmitting coil and receiving were turned to 9.9 MHz (30m wavelength) and oriented along the same axis. An approximate 45% efficiency was achieved. The best part, all the wireless power is completely safe, falling under FCC specifications for being dangerous to living creatures. Unfortunately the technology is still in the prototype phase. Witricity is busy getting accolades, awards, and generating buzz. But I hope they finish strutting about, and we see this technology soon.
Witricity's artistic concept
After this, perhaps we can work on Tesla's Death Ray?