It’s ironic that wireless gadgets don’t live up to their name. Even the best wireless gizmo will run out of juice and die without regular plugging in and charging up. Not anymore. Wireless electricity has arrived and you can now watch TV and recharge your camera and iPod without any cables at all. Tripping over a rat’s nest of wires behind your computer is a thing of the past.
Like most brilliant inventions, the idea of wireless electricity is not new. In the late 1800s the great electrical pioneer Nikola Tesla proved to the world that it was possible to transfer electricity through the air. When electricity was still in its infancy, Tesla and others saw wireless transfer as the ideal method. Tesla even built the 39 metre high Wardenclyffe Tower in New York to test it out on a large scale. However, his project ran into financial difficulties, petered out and was largely forgotten. A hundred years later, thanks to the proliferation of wireless devices in need of constant recharging, wireless electricity has made a comeback.
There are many methods of wirelessly transmitting energy, such through microwaves, radio waves and lasers. Microwaves have obvious disadvantages (heating up your head and making it explode) while lasers only operate in a straight line, and radio waves don’t provide much power. The best, and most popular, system is magnetic induction.
The system exploits the phenomenon of resonance, whereby energy transfer is more efficient when two objects have the same resonant frequency. Electricity is directed through a ring made of magnetic wire to create an electromagnetic field, which resonates energy at a certain frequency. The electromagnetic energy is transmitted through the air to another magnetic coil which resonates at the same frequency as the first coil, converting the energy into electricity. Think of it in terms of sound: noise at the right frequency can destroy a glass but at the wrong frequency has no effect. The equivalent of the exploding glass is the coil picking up and generating electricity.
A common fear is that wireless electricity will fry your brain and make your head explode like a popped water balloon. But wireless electricity is safe because most of the energy is transferred through magnetic fields and not electric fields. Even when metal objects get between the power source and receiver, the metal does not heat up because energy is only absorbed by the resonating coil.
The biggest shortfall of wireless electricity is that efficiency declines rapidly with distance. Most companies are only aiming to transfer energy over short distances - several metres at the most. Another problem is poor efficiency - between 60% to 90% efficiency is the norm, although this is improving. However, if wireless electricity replaces disposable batteries, the environmental benefits would be worth it as 40 billion (yes, billion) disposable batteries are produced every year.
The potential applications of wireless electricity are huge. For one, you’d never have to worry about charging your gadgets. Just leave them somewhere in your house and they’d charge automatically - and you’d be able to charge a dozen gadgets at a time. Just drive your electric car into the garage and it would start charging immediately. Hang your TV anywhere on the wall and never worry about fiddly cables - the possibilities are endless. There are many important medical applications too, such as pacemakers that would never need replacing or new batteries.
There are many companies currently working on or mass-producing wireless electricity and wirelessly powered products, from Bosch to Toshiba. In October last year Sony debuted a wireless TV, which operated at 80% efficiency at a distance of 50 cm from the power source, while Fulton Innovation is currently selling its eCoupled system for recharging electrical devices.
One of the pioneers behind wireless electricity is the American company WiTricity, which was set up by physicists from the Massachusetts Institute of Technology (MIT), and has produced wirelessly powered cellphones and TV sets. In January this year, Chinese manufacturer Haier showed off a 32 inch wireless TV set, which was developed in cooperation with WiTricity. The companies aim to be the first to deploy a wireless TV in the next few years. You should also look out for clip-on wireless chargers for your iPhone and laptop.
Experts, such as Eric Giler from WiTricity, estimate that wireless electricity will be the norm in five years time. Wirelessly powered gadgets are already here and will only become more common, more efficient and useable at greater distances. We are standing on the edge of the wireless revolution.
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