Wireless Energy Transfer: Just Science Fiction?

[Kenny Bala]

There's been some buzz about wireless energy transfer for quite some time now, but it seems really far fetched to me that we will get any significant power usage out of wireless energy transfer. What do you guys think? Does this form of energy have any significant potential at all, or is it just science fiction?

 

[Dale]

It is already being used in several different kinds of devices. It isn't science fiction, certainly.

 

[Devils]

MIT has investigated it & spun off http://www.witricity.com/

http://www.sciencedaily.com/releases/2007/06/070607171130.htm
" they were able to light a 60W light bulb from a power source seven feet (more than two meters) away; there was no physical connection between the source and the appliance. "

 

[TheDemx27]

http://www.sciencedaily.com/releases/2007/06/070607171130.htm

As a side note, I just want to mention that science daily has not been a very reliable source in my experience. Although I can't find the article now, there was one article which stated that musicians can communicate while playing using brain waves, d-waves in particular. I know this is off topic, but I think it should be noted nonetheless.

 

[nsaspook]

Buzz is the correct word, unless you are directly connected to the utility generator there is a very good chance that energy has been transferred at least once with a 'wireless' device called a transformer using magnetic fields instead of a conductor.

Most people who investigate 'wireless energy' come to the same conclusion, it works for a few applications but won't replace wired power systems in general.

http://www.vk2zay.net/article/253

 

[sophiecentaur]

'Contactless' power transmission is a very promising field. (No pun intended) The 'charging mat' is something that will surely be in general use before long. It is wireless - but only just.

Significant levels of Power transmission over a large distance will always be fraught, in terms of unwanted emissions and safety. There are claims about fancy antennae that are highly directive and efficient but the safety aspect is so important that any disturbance to radiation pattern would need to be detected and the system would have to be turned off.

But there could always be the exception where a working power link is so desirable that the technical difficulties will be solved - at great expense.

Solar is, and always will be, the best 'wireless' source of power. Hideously inefficient but who cares. in that case?

 

[AlephZero]

Wireless power transmission has been around for well over a century already. Every transformer transmits power from the primary coil to the secondary wirelessly. Every radio and TV transmitter and cellphone does the same.

Transmitting a lot of power a short distance (a transformer), or a tiny amount of power a long distance (radio communications) are both easy. The only hard part is transmitting a lot of power a long distance.

 

[phinds]

I once saw an analysis of Tesla's proposed plan for wireless energy. It DID work, but to power the homes in the USA, it was estimated that a grid of power repeaters would be required on a grid of 1 mile by 1 mile over the entire country (didn't matter if it was uninhabited desert, the transmission still require the mile-apart towers) and that the cost of buying the land and building an installing the towers and operating them for the first year would have cost the GNP of the entire world for several years. In short, it's not practical for large-scale use. Also as I recall, there were other side-effects such as killing off the entire countries population of birds. It was a particularity terrible idea, but seems to be the kind of thing that make the uninformed tout Tesla as far more of a genius than he really was.

 

[sophiecentaur]

When you say "did work", you must mean an experimental system gave an 'encouraging result', perhaps. Nothing, in Tesla's day, (or even now, aamof) was reliable enough to maintain such a large system for more than a matter of minutes. And how would the power have been delivered to all the towers? Cables with tar and paper insulation, I guess.
Just what was it about that guy that appeals to the uninformed, so much?

 

[phinds]

When you say "did work", you must mean an experimental system gave an 'encouraging result', perhaps. Nothing, in Tesla's day, (or even now, aamof) was reliable enough to maintain such a large system for more than a matter of minutes. And how would the power have been delivered to all the towers? Cables with tar and paper insulation, I guess.
Just what was it about that guy that appeals to the uninformed, so much?

Yeah, he build a very large tower and demonstrated that the idea was technologically feasible, but it wasn't REALLY, as was discussed in the analysis I referred to above. He never got funding to build the bigger tower that he felt would really show the world.

As for his widespread popularity, I can only think that it is among folks (and there are a LOT of them) who believe in alien visitations and ghosts and all kinds of crap.

 

[Kenny Bala]

Absolutely fascinating, I didn't know that this was even possible without radio waves or a laser. How do they manage to transfer energy though, without using EM waves?

 

[berkeman]

Absolutely fascinating, I didn't know that this was even possible without radio waves or a laser. How do they manage to transfer energy though, without using EM waves?

Think "air core transformer".

 

[sophiecentaur]

Absolutely fascinating, I didn't know that this was even possible without radio waves or a laser. How do they manage to transfer energy though, without using EM waves?

What gave you that idea? Don't be misled by what you may read about Tesla's inventions. They worked just the same as anything else. (Using EM)

 

[Dale]

Absolutely fascinating, I didn't know that this was even possible without radio waves or a laser. How do they manage to transfer energy though, without using EM waves?

It still uses EM waves. But in a transformer or other similar (short range) methods of wireless transmission the transmission is done primarily in the near-field, with as little energy radiated to the far field as possible.

 

[Devils]

It still uses EM waves. But in a transformer or other similar (short range) methods of wireless transmission the transmission is done primarily in the near-field, with as little energy radiated to the far field as possible.

The issue is that, in the simple implementation, the waves are radiated in all directions, and the inverse square law means you need to be very close. I believe newer systems use directional techniques to achieve longer distances.

 

[sophiecentaur]

The issue is that, in the simple implementation, the waves are radiated in all directions, and the inverse square law means you need to be very close. I believe newer systems use directional techniques to achieve longer distances.

The inverse square law is not affected by directionality. The way that the ISL can be dealt with is with an extended source - a wide enough array not to look like a point source.