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Power without plugs...
11/06/2007 12:57 - (SA)
Brian Bergstein
Cambridge, Massachusetts - Massachusetts Institute of Technology researchers announced they had made a 60-watt light bulb glow by sending it energy wirelessly, potentially previewing a future in which cellphones and other gadgets get juice without having to be plugged in.
The breakthrough, disclosed in Science Express, an online publication of the journal Science, is being called "WiTricity" by the scientists.
The concept of sending power wirelessly is not new, but its wide-scale use has been dismissed as inefficient because electromagnetic energy generated by the charging device would radiate in all directions.
Last autumn, though, MIT physics professor Marin Soljacic explained how to do the power transfer with specially tuned waves. The key is to get the charging device and a gadget to resonate at the same frequency - allowing them to efficiently exchange energy.
It is similar to how an opera star can break a wine glass that happens to resonate at the same frequency as her voice. In fact, the concept is so basic in physics that inventor Nikola Tesla sought a century ago to build a huge tower on Long Island that would wirelessly beam power along with communications.
The new step described in Science was that the MIT team put the concept into action. The scientists lit a 60-watt bulb that was 2 metres away from the power-generating appliance.
"It was quite exciting," Soljacic said. The process is "very reproducible", he added. "We can just go to the lab and do it whenever we want."
Within reach
The development raises the prospect that we might eliminate some of the clutter of cables in our ever-more electronic world. Is that necessarily a good thing? Soljacic acknowledged "that it's far from obvious how crucial people will find this".
But at least one benefit could be that if devices can get their power through the air, they might not need batteries and their attendant toxic chemicals.
Before that can happen, the technology has a ways to go.
The MIT system is about 40% to 45% efficient - meaning that most of the energy from the charging device does not make it to the light bulb. Soljacic believes it needs to become twice as efficient to be on par with the old-fashioned way portable gadgets get their batteries charged.
Also, the copper coils that relay the power are almost 60cm wide for now - too big to be feasible for, say, laptops. And the two-metre range of this wireless handoff could be increased -presumably so that one charging device could automatically power all the gadgets in a room.
Soljacic believes all those improvements are within reach. The next step is to fire up more than just light bulbs, perhaps a Roomba robotic vacuum or a laptop.
The MIT team stresses that the "magnetic coupling" process involved in WiTricity is safe on humans and other living things. And in the initial experiments on the light bulb, nothing bad happened to the cellphones, electronic equipment and credit cards in the room - though more research on that is needed.
The harmlessness apparently extends both ways: The researchers noted that putting people and other things between the coils - even when they block the line of sight - generally has no effect on the power transfer.
- SAPA
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