Produce Electricity from unused Radio waves?

[supratim1]

Hello everyone!

I was just thinking about whether it will be possible to utilise the energy transmitted through the radio waves to produce back electricity for a household. Most of the houses in the world are blanketed by radio waves from all directions. Will it be possible to use an antenna and suitable circuit to convert that energy to electricity? Also, will it be efficient enough and feasible?

Please give your thoughts.

Thank you.

 

[fss]

It's already being done in small scale applications.

http://en.wikipedia.org/wiki/Wireless_energy_transfer

Large-scale applications, like households, are a long ways off.

 

[Born2bwire]

Possible? Yes. Feasible? No.

It's already being done in small scale applications.

http://en.wikipedia.org/wiki/Wireless_energy_transfer

Large-scale applications, like households, are a long ways off.

Those are different though. The OP is talking about harvesting the existing radiation in the air. Wireless energy transference is done by intentionally creating a strong directed (or inductive) electromagnetic field for the purpose of being harvested by the target device.

The background radiation though is not targeted. Radio transmissions, TV transmission, wifi, cell phone, etc. are emitted in a more or less blanketed fashion. There is some directivity involved but on the whole the idea is to blanket an area to provide reception to a large number of customers or recipients. In this manner, even though they use kilowatts or megawatts of energy to transmit, the energy density received by the consumer is low. In fact, a crystal radio is the only device I can think of off-hand that is completely powered by the received radiation. Every other application requires that the received signal undergo amplification. So in the end, with a device of moderate size the physical aperture presented by your antenna is going to be too small to harvest any meaningful amounts of energy.

 

[supratim1]

yes i was thinking about that too. it will be economically unfeasible. but what if we increase the antenna area? suppose we embed antennas in all the walls and roof, like a faraday cage? will it work? could it just be enough to power up 3 bulbs and a fan? if so, it would be most useful for millions of villages around the world. what do you think?

 

[fss]

yes i was thinking about that too. it will be economically unfeasible.

Stop right there. That's all you need to know.

 

[skeptic2]

Doing this efficiently enough to be useful would alter the radiation pattern of the transmitting station and at least in the U.S. is illegal. You would be stealing power from the transmitting station.

 

[supratim1]

Stop right there. That's all you need to know.

economic concerns don't stop research for improvement.

 

[jollyPHYSICS]

economic concerns don't stop research for improvement.

precisely! environmental safety comes first... Anything that'll secure our ozone guy, ain't illegal. ;-)

 

[Ryan_m_b]

economic concerns don't stop research for improvement.

I think the poster meant economical in terms of efficiency rather than dollar value.

I.e. if technology did develop to allow wireless transfer of electricity via radio waves it would still be inefficient compared to other mechanisms

 

[guillefix]

Could Tesla's idea have been possible though? By Tesla's idea I mean his idea of powering the whole world by charging the air and the ground by his famous Tesla's coils, or in this case towers because they needed to be very big to give electricity to a considerable area: http://en.wikipedia.org/wiki/Wardenclyffe_Tower"

 

[pallidin]

Doing this efficiently enough to be useful would alter the radiation pattern of the transmitting station and at least in the U.S. is illegal. You would be stealing power from the transmitting station.

That is only true if the interception degrades transmission to other, potential, users.
If the interception does not do this there is no problem.

An example would be, say, collecting said energy that is directed to the ground.
As no-one is below you(in some cases) there is no degradation.
Hence in no way illegal.

It's wasted anyway, might as well collect it!

Just my opinion...

 

[supratim1]

yes, i agree with Mr. Palladin. i was thinking the same thing.

 

[SteamKing]

I think you also must look at the power some of the biggest stations transmit. For radio, a super size AM transmitter might consume 50,000 watts (or 50 Kw, the power produced by a modest size generator). These powerful stations might produce a signal which can be received in several different states. Small, local stations can be set up with as little as 5000 watts, and the range of reception is reduced substantially. When you start looking at the proportion of energy available to a typical household, it would probably be more feasible to develop gerbil power, or use the flush from your toilet in a home hydroelectric power station.

 

[davenn]

Hello everyone!
I was just thinking about whether it will be possible to utilise the energy transmitted through the radio waves to produce back electricity for a household. Most of the houses in the world are blanketed by radio waves from all directions. Will it be possible to use an antenna and suitable circuit to convert that energy to electricity? Also, will it be efficient enough and feasible?
Please give your thoughts.
Thank you.

There's just so many fundamental flaws in this plan.

for example the signal strength of say even a 250kW TV transmitter arriving at your house 20km away is just a few microVolts. It isn't going to light a LED (light emitting diode) let alone any incandescent globes. The inverse square law sees to that ;)

just building a bigger antenna isn't going to work.
a bigger antenna is practically going to be resonant at a lower frequency and no good at higher freqs.
You cannot have a highly efficient antenna that will work of all the RF "floating around" your house. Our radio/TV transmitter/receiver systems work as well as they do because we use antennas resonant to the intended freq of use so that they "receive/harvest" (dont really like either of those terms, but will do for the discussion) the maximum amount of energy at that freq.
a hi gain antenna at say 100MHz will receive a good few microVolts from the 88 - 108MHz FM radio stations but will be useless at receiving UHF TV signals at 500MHz

A bit of reading on the basic concepts of Rf transmission, power levels, received signal strengths and the physics of it all, will quickly show you how futile the effort would be

cheers
Dave

 

[sophiecentaur]

Add up the powers of all the transmitters within, say 20km of your house and then divide it amongst all your neighbours (thousands and thousands of them). Then allow for the fact that the transmissions will surely spread out so that most of the power, actually, will end up in space or heating up rocks and water vapour in the air - not in the antennae of the householders. If you end up with more than a few watts per household then I should be very surprised. Considering the cost of this installation, you'd be far better to put a square metre of PV panel on the roof an get the same amount of power or more for a lot less money.

 

[bayners123]

My Mum sent me an email asking me this very question this morning: turns out that there's a shady company called teslasecret.com who are flogging this idea as "Free Electricity" to power tomorrow's world...

 

[sophiecentaur]

If an offer looks too good to be true then it probably is!
Mr Tesla has a lot to answer for.

 

[supratim1]

and what about using the cosmic background radiation and also the Earth's magnetic field fluctuations due to constantly fluctuating magnetosphere?

 

[sophiecentaur]

This is an Engineering topic. As such, the actual numbers involved are important when deciding if it's worth while bothering with.
Just consider the fact that PV conversion of sunlight is only just financially viable. That is for an incoming energy flux of about 1kW/sq metre from the Sun. The sum total of all the other forms of EM energy is a tiny fraction of this. How, then, can one justify any scheme to get this 'free energy' when it would cost many times its total value (over a vast length of time) to implement.
Just because you can measure an electrical signal doesn't mean that it constitutes a usefull source of energy.

 

[supratim1]

yes you are right. so the best way forward is to increase the efficiency of our PV cells.

 

[sophiecentaur]

Absolutely

 

[kiran vaghela]

anybody have a ckt of this small scale transmissin?/

 

[sophiecentaur]

anybody have a ckt of this small scale transmissin?/

Meaning what?

 

[skeptic2]

Doing this efficiently enough to be useful would alter the radiation pattern of the transmitting station and at least in the U.S. is illegal. You would be stealing power from the transmitting station.

That is only true if the interception degrades transmission to other, potential, users.
If the interception does not do this there is no problem.

An example would be, say, collecting said energy that is directed to the ground.
As no-one is below you(in some cases) there is no degradation.
Hence in no way illegal.

It's wasted anyway, might as well collect it!

Just my opinion...

The interception does not have to be in the direction of the recipients. Several years ago the FCC made it mandatory for anyone constructing a tower in the vicinity of an AM broadcast station to get the permission of the broadcast station owner before constructing the tower. Although the new tower does not capture energy from the broadcast station as you are suggesting, the effect is similar.

 

[Vanadium 50]

You're all making this way, way too hard. How much power is radiated? 50,000W is the AM limit, and most stations are smaller. If you add up AM, FM and TV for a large metropolitan area you get maybe 1 MW for 10 million people - or 1/10 of a watt per person. That's the best you could ever hope to do.

Even with magic technology, it's impractical.

 

[ajroberts001]

Hey what if a produce a electromagnetic radio wave from my 240v wall socket converting that to 10v which produces a radio wave at say 2.4ghz then harvest it from 30meters away to a small copper antenna which the produces the radiation back into electricity to glow a led.

 

[russ_watters]

Hey what if a produce a electromagnetic radio wave from my 240v wall socket converting that to 10v which produces a radio wave at say 2.4ghz then harvest it from 30meters away to a small copper antenna which the produces the radiation back into electricity to glow a led.

Welcome to PF!

What if what? Could you do it successfully? Probably. Is that what you are asking?

 

[ajroberts001]

Welcome to PF!

What if what? Could you do it successfully? Probably. Is that what you are asking?

Thanks man

 

[ajroberts001]

Welcome to PF!

What if what? Could you do it successfully? Probably. Is that what you are asking?

Do you know how?

 

[cosmik debris]

Doing this efficiently enough to be useful would alter the radiation pattern of the transmitting station and at least in the U.S. is illegal. You would be stealing power from the transmitting station.

Yeah, if the radiation is useful it is stealing, if it's harmful it isn't ours it's your problem.