Wireless Power Demonstrated

Necroloth and other readers sent in the story of Witricity's latest demo at the TED Global conference in Oxford, UK. The company is developing a system that can deliver power to devices without the need for wires. The idea is not new — electrical pioneers Thomas Edison and Nicola Tesla assumed that power would be delivered wirelessly. The BBC quotes the inventor behind Witricity's tech as saying that Tesla and Edison "...couldn't imagine dragging this vast infrastructure of metallic wires across every continent." eWeek Europe notes some hurdles the technology must overcome: "The 2007 experiment it is based on had an efficiency of only around 45 percent, but [Witricity's CEO] promised power delivered wirelessly would start out 15 percent more expensive than wires, and improve on that." Intel has also demonstrated wireless charging.

Comments

Standard interface?

[elwinc]

Resonant transfer is great stuff, but what we need even more is a standard interface so that all our rechargable devices can recharge at the same source.

Re:Standard interface?

[dgatwood]

I think that's massive overkill. Just provide a 12V rail, a 5V rail, and a ground using a polarized plug. Heck, you can probably dispense with the 12V rail. A 5V rail by itself should cover the vast majority of portable electronics these days. Amperage negotiation? Build the supply so that if it is under too much load, it sheds power connections, then periodically switches which jacks are shed. That's much cheaper to design, and it doesn't unnecessarily add to the complexity of the devices that use it.

Thomas Edison ???

[nurb432]

Electrical pioneer my ass, he just got lucky once and was able to afford to hire good talent ( like Nikola ). But i totally agree that Tesla proved it was possible ( and WAS a pioneer ). But he also proved that it takes more then tech to make such a project work, it also needs funding. As brilliant as he was, a businessman he wasn't, and we were set decades behind on projects such as this.

Re:Thomas Edison ???

[lawnboy5-O]

My grandmother worked for Thomas Edison - so I the FUD on Edison I can speak to directly as she was my intellectual mentor growing up - and yes we spent hours and hours talking about that crazy Edison.

Some points you should know:
Most of the consumer devices you use today are direct descendants of Edison's inventions.
Edison was no Crook either - even if only paying my sweet grandmother ~17 cents a day around the 1920's.
He was indeed eccentric toward the later years of his life however, and experienced what many would consider a form dementia today.

His list of inventions towers over just about all other modern inventors - I suggest all of you look them up - there are many, many stories to tell. From movies to music, refrigeration to your TV, he's been involved in some way.
...and by the way - it was Marconi that invented most of what was later attributed to Tesla... and returned to Marconi only recently by world courts.

Re:Thomas Edison ???

[Heed00]

Bah. He came up with that cool electric hammer that was recently discovered as well as the extra hinged legs on chairs to stop you falling over if you lean back too far.

Retarded.

[girlintraining]

Blasting large amounts of EMI solely to avoid the need to put a battery in something is stupid. Right now EM radiation is controlled to the lowest levels it can practically be in order to achieve some transfer of information between two or more points. Any power transfer system is going to muck up what's already in the air. It's called Shannon's Law -- and no matter how you sex up the technology, the fact is you're raising the noise floor doing this.

Bad engineer. No cookie for you.

Re:Edison?

[n3umh]

It's not only possible, but really damn easy to do.

You can build a reasonably efficient resonant power transfer doohickey in your backyard out of some copper tubing, some low loss tuning capacitors, a RF power generator, and some diodes and filter caps on the far end to turn the received RF into DC.

I've built one to couple 4MHz pulses across to a rotating experiment for ultrasound measurement: http://n3ox.net/files/us_ring.jpg

You couple 'em that tightly, and they're like 99% efficient at transferring power.

But even with Tesla aside, this isn't new... it's just not as vastly useful as people re-discovering it seem to think it is. It doesn't work over gigantic distances, only moderate ones, and there's no engineering you can do to get around that. It's near-field coupling between resonant circuits. That said, I think it might end up pretty useful for non-contact charging of your electric car like TFA suggests. That's a *good* application for it, and it has more efficiency than "ordinary" inductive coupling.

As a physicist...

[The Master Control P]

I'd like to be the first to complain that resonant power transfer has nothing to do with quantum entanglement.

You'll be getting a memo from the Tesla Death Ray department shortly; Not observing it won't save you.

not all wireless power is the same

[stevenj]

There are several very different schemes currently being explored for wireless power transfer, with different strengths and weaknesses.

• Radiative transfer: send a directed beam of energy from a source to a receiver. The advantage is that this can work over long distances, the disadvantage is that you need to either have fixed locations or some active tracking system to keep pointing at the receiver as it moves around, and you need some kind of automated kill switch to make sure you don't accidentally fry anything that walks between the transmitter and receiver or waste power when the receiver is not there. It looks like PowerCast and PowerBeam fall into this category.
• Traditional inductive, non-radiative power transfer. This works well, and does not transfer power when the receiver is absent, but is extremely short-range if you want any kind of efficiency; typically, the device to be charged must be sitting directly on or adjacent to the charger. The Wireless Power Consortium is pursuing this kind of approach.
• Resonant, non-radiative power transfer. This relies on the source and receiver being electrical resonators at the same frequency, so that they preferentially transfer energy to one another rather than to other objects in the environment via resonant coupling. This is the approach being pursued by WiTricity, where they additionally rely on resonators that couple primarily via magnetic fields (the electric-field energy is mostly in capacitors inside the devices), which have the advantage that most materials are non-magnetic at these frequencies so the power source dissipates very little energy into extraneous objects (or people). (In contrast, Tesla coils produce strong electric fields external to the device, which interact much more strongly with matter; it's no coincidence that Tesla coils are used as lightning generators.) This operates efficiently at mid-range distances although not as far as radiative transfer (meters at most), does not transfer or dissipate power when the receiver is absent, and is not directional so does not require active "pointing" of the power at the receiver. But it is more complicated than the short-range non-resonant inductive transfer, and requires careful impedance-matching of the source and receiver.

Full disclosure: I know Prof. Soljacic at MIT, who founded WiTricity, although I personally have no financial interest in the company; all of the above information is public and published, however.