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Recently I came across this quote on the internet, about a person who apparently set up devices to extract electricity from the "air", on his own property:

I read an article a couple of years ago about this very thing, Someone had lined the edge of their property with devices to capture bleed-off from the transmission lines and was using it to power the house. They were able to cut power bill to less than 10% of normal and the power company sued them and won. It is illegal to "harvest" unused power from transmission lines. I don't know if the same would apply to radar/radio/etc... I would do some checking before I spent a lot of money on equipment.

I'm not interested in the legal side of things, but I'm wondering if one set up a device to extract energy in this way, will this method simply be scavenging energy that would otherwise be wasted, or is he somehow stealing the energy that would otherwise be used in the transmission lines?

Please explain the physics behind your response.

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2 Answers 2

up vote 2 down vote accepted

There exists a way to harvest electromagnetic energy which is otherwise lost, and thus it is not stealing from anybody.

Previous efforts were scavenging only from narrow bands. That led to tiny amounts of power. In order to have a significant amount of power, we thought we should be able to scavenge energy from the whole frequency range. To do that, we developed extremely wide-band antennas. We managed to do this in a very cost-effective and environmentally-friendly way. We developed in-house ink jet printer technology where we can ink jet print circuits or metals on very low cost substrates like paper or plastic.

The third trick we utilized was finding efficient ways to keep storing this energy. It’s like having to collect small droplets of water [from all different directions] in a single cup. We developed some ways using a super-capacitor where we can store this energy. After we reach the amount of power we want, we utilize it in a spurt and that activates a sensor or some very small communication device.

If the power company won the suit, the fellow must have been bleeding power from the line: set up an AC circuit which drew power directly, by a capacitive or inductive coupling without touching the line.

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The rumour I heard involved induction coils in a barn, so that would involve back-EMF and thus stealing power. –  Retarded Potential Feb 2 '13 at 0:01
    
Also, as I recall in some places the laws about electricity generation are somewhat weird, so that one cannot conclude that they were stealing power by the fact that the power company won the case. –  Retarded Potential Feb 2 '13 at 0:03
    
@RetardedPotential also the claim is for 90% savings and as the link i supplied shows technology has not reached that level. –  anna v Feb 2 '13 at 4:39

I would add, however, that any modification of the environment near the transmission lines changes the net impedance (the effective AC resistance) of the circuit carrying the power. So, even while for the most part you are just collecting leaked energy, you are also lowering the amount of transmitted energy. If you build an electric circuit containing a coil and this will deliver the a certain amount of energy to all components. You can then bring a second coil near the first, without touching it, and the currents, potential drops and power in the elements will change.

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protected by Qmechanic Feb 11 '13 at 12:51

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