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"Wireless electricity is something we used to talk about years ago almost as a bit of a joke when we made predictions about the future," says Michael Brook, editor of the gadget magazine, T3. "To a lot of people it sounds insane that you could even do it – like some kind of witchcraft – but we're seeing a lot of interest in the first wireless chargers. It's going to take off in a big way." If not witchcraft, how does it work? Here's the science: Current from the mains is wired into a transmitter coil in the charging mat. This generates an electromagnetic field. A receiver coil in the phone's case takes the power from the magnetic field and converts it back into electricity that charges the device. By separating those coils, induction charging takes the 150-year-old principle used in the transformers found in most electric devices and splits it in half. No more tripping over laptop leads and their power bricks or diving under your desk to plug in your charger – just put your gadget on the mat and induction takes care of the rest.
But wireless induction, which, in a less-sophisticated form has charged electric toothbrush chargers and some medical implants for years, isn't perfect. Advances mean it's now viable for more demanding devices, but in the case of the PowerPad, it requires a case that adds bulk to what is already a hefty handset. Another drawback is the lack of compatibility – a phone with a PowerPad case will not charge on a PowerMat.
A growing group of electronics firms want to sdeal with the problem. The Wireless Power Consortium (WPC) includes Gear4 and the mobile phone giants, Nokia, Samsung and RIM, makers of the Blackberry. "These companies think there won't be a mass market for wireless charging unless there is a standard," says Menno Treffers, chairman of the consortium's steering group and a director at Philips.
Learning their lesson from the hopeless incompatibility of wired chargers, supporters of WPC's Qi ("chi") standard will put universal coils in devices that will work without cumbersome cases. They'll also be compatible with any charging mat, whether it's on your desk or recessed in a table at Starbucks. Treffers expects the first Qi-compatible devices to hit shelves next year.
But there remains a major flaw in charging mats – their need for proximity. Separation of even a millimetre renders most mats useless. Take your laptop to your bedroom to watch a DVD and you'll need a second mat or a cable. For a truly wireless scenario, electricity must make a giant leap.
Marin Soljacic is a Croatia-born physics professor at Massachusetts Institute of Technology (MIT). In 2002, he got annoyed when his wife's mobile phone woke him up with beeping when its battery ran low. "Not only did I have to wake up to plug it in but had to find the charger in the dark," he says. "I thought, power is everywhere – sockets all over the house – yet it isn't close enough." Soljacic was sure there must be a way to bridge the gap. He wanted his wife's phone to charge while it was still in her handbag. Two years ago, after months of equation crunching and computer modelling, Soljacic literally had a light bulb moment when he flicked the switch of a 60-watt lamp. No big deal except that the electricity powering the light was travelling two metres through thin air.
Soljacic and his team at MIT have since formed a company called WiTricity. Last July, its chief executive, Eric Giler, came to Oxford to demonstrate a wireless television. In front of an amazed audience at a technology conference, he powered up a giant plasma screen TV that had no cables. Electricity sprung from a sleek unit on the floor to a receiver mounted on the back of the screen. Last month, Giler travelled to Japan to show off a wirelessly-charged electric car. "Every time I show people they're blown away," Giler says. "When you see it up close it does appear almost magical."
Soljacic's magic takes the split-transformer model that powers charging mats and adds a key ingredient to make electricity fly. It's called resonance, the phenomenon that means a singer who matches the acoustic frequency of a wine glass can shatter it. Soljacic knew that two resonant objects of the same resonant frequency tend to exchange energy efficiently – imagine a tuning fork causing a nearby fork with the same frequency to chime sympathetically. His breakthrough was to work out a way to use resonance in magnetic form to transfer not sound but electricity. He explains: "By coupling the magnetic field that surrounds a resonant coil to another coil resonating at the same frequency, we can make the electricity hop from one to the other."
WiTricity's strongly coupled magnetic resonance means cars, TVs, free-standing lamps, and computers – anything that requires electricity – can be powered or charged from a central source in the ceiling or under the floor. And it's all totally safe. "The fields that we are generating in are about the same as the earth's magnetic field," Giler says. "We live in a magnetic field."
Giler and his team are in talks with big-name electronics manufacturers, including many of those who are putting their names to the Qi standard for charging mats. Giler says proximity charging is "first-generation stuff; by the end of next year you'll start seeing devices with WiTricity components built in". If he is right, homes and offices could soon be fully wireless. "It's a fundamental breakthrough in science and a game changer for the industry," he says. "Cut the cords and the world's going to change."
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