The Green Benefits Of Wireless Power

This runs counter to my intuition: if the wasted energy would otherwise come out as heat, it’s hard to see how it can become low-entropy electric energy instead, but eWEEK hasn’t had a detailed description.

Overall, the technology can easily reach nearly 90 percent efficiency, said Giler, because it involves four efficient processes. Firstly, the system turns mains electricity into DC, using a rectifier: the efficiency of this can be well over 90 percent, and depends on how much you spend. Researchers have produced recitifiers that are over 99 percent efficient.

Secondly, the radio-frequency (RF) signal is generated, at around 99 percent efficiency. The magnetic coupling efficiency varies from ten percent up to more than 90 percent, as Giler said above, and it is then rectified again to DC, with an efficiency around 99 percent.

“These all multiply together,” said Giler, so it’s possible to get well over 90 percent efficiency if the magnetic coupling stage is run reasonably efficiently.

Witricity competes with batteries, not wires

Witricity is green, he says, because it is not usually competing with wires, but with disposable batteries.And here, the potential savings, in terms of money and the environment, are massive.

The Witricity system uses electricity from the grid, at a cost of around five pence per kiloWatt, while disposable batteries, which deliver around 2000mAh each at 1.5V, produce a cost of maybe £300 per kiloWatt hour – along with a heavy environmental cost in their disposal.

“When you buy a PC, it comes with a free keyboard and mouse, but people feel compelled to waste money on a wireless keyboard and mouse,” he said, “despite the inefficiency.”

What about the magnetic fields?

The Witricity system doesn’t produce stray magnetic fiels which could wipe credit cards or destroy Oyster cards, said Giler. “The range of resonance is so tight, it is virtually impossible to interact with anything else. It’s not like putting a magnet on a CRT; interference is virtually impossible.”

With all this going for it, the system could make it into devices very quickly, he said. “In 18 months it will be in common products – starting with an electric vehicle before the end of this year.” The company has made demonstration backs for the Nokia N97, and the Blackberry Curve as well as the Android G1 phone. Only Apple devices need an additional sleeve, because they are designed not to be opened.

Because of the chicken-and-egg situation, the first products will be “closed” systems, where the charger and device are sold together. This is similar to the Palm Pre’s Touchstone, although that is an inductive device nothing like Witricity, said Giler.

However the Touchstone costs $70 and Witricity could be available much cheaper, he said: “It could be added to the device for a materials cost of around $2, and the source would cost $5.”