Enlarge / The developers of a new wireless charging tech are thinking big—automobile battery big. (credit: Oak Ridge National Lab)

Anyone who has ever left the house without remembering to charge their cellphone can appreciate the concept of wireless power transfer. All you would have to do is remember to drop your phone on your desk, and a wireless charging mat would ensure that it has a full battery by the time you pick it up again.

But current wireless charger systems require specialized hardware on both the sending and receiving ends, and power only flows efficiently when the two are a specific (and short) distance apart. It's possible to expand that distance a bit by carefully adjusting the frequency used to induce current at a distance, but this adds to the complexity and energy overhead of the system. And even the best current systems have losses that mean wasted electricity at a time when energy efficiency is critical.

Now, researchers at Stanford have found a different way to handle wireless charging. Taking advantage of a quantum principle that also applies to the everyday world, they've created a system in which power is transferred over a wider distance with roughly 100-percent efficiency. Better still, the system adjusts itself to the distance, so careful frequency tuning becomes unnecessary. The big downside, however, is that the supporting electronics aren't especially efficient.

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