Beam Me Up Scotty - Energy from Thin Air

[Zydor]

Ok .... its official .... I'm getting old .....

Researchers at Duke University have created a device that collects stray energy from Wi-Fi and other wireless signals and converts it into electricity that can charge as efficiently as solar cells.

http://www.computerworld.com/s/article/ ... 2013-11-13

*sigh*

[Woodles]

So if you put a tuned antenna into a waveguide you can detect a signal? Who would have thought it!  :shock:

[UBT - Timbo]

With so many sources of signals, (mobile phones, microwave links, wifi routers etc), it doesn't take a rocket scientist to figure out that with just a bit of circuitry, one could collect the radio frequencies and turn them into another form of energy...

After all, isn't that what an AM radio does - turns RF into sound?

So, what I want is a small device that collects said RF signals, plugs into a micro-usb port, so I can recharge my smartphone for free....!!!!

regards
Tim

[Woodles]

With so many sources of signals, (mobile phones, microwave links, wifi routers etc), it doesn't take a rocket scientist to figure out that with just a bit of circuitry, one could collect the radio frequencies and turn them into another form of energy...

It is very rare for broadcast radio signals to exceed 0.00025 mw/m2 inside a house, with VHF/UHF signals rarely exceeding 0.000007 mw/m2.
At a distance of 25 - 100m from a mobile phone base station, power levels of 0.1 mW/m2 - 3.0 mW/m2 may be expected.
So mobile 'phone signals will generally swamp any television/radio ones.
A 1 square metre RF antenna would collect 0.1 - 3 watts of power.
At the same efficiency as current solar panels, it would produce 0.012 - 0.51 watts of power.

(The experiment in the paper was performed at 16000 mW per square metre RF power  :o )

After all, isn't that what an AM radio does - turns RF into sound?

Your standard radio consumes much more power than it produces!

So, what I want is a small device that collects said RF signals, plugs into a micro-usb port, so I can recharge my smartphone for free....!!!!

An iPhone battery produces ~ 5.5 watts. @ 70% efficiency charging, it needs 7.8 watts to fully charge. An S3 battery produces ~ 7.98 watts, 11.4 watts to charge.

Use solar power to charge your 'phone, use USB to charge your 'phone but harvesting power from thin air won't charge your 'phone unless you're sitting under a mobile 'phone mast with an umbrella sized antenna and have 15 - 950 hours to spare!

[UBT - Timbo]

It is very rare for broadcast radio signals to exceed 0.00025 mw/m2 inside a house, with VHF/UHF signals rarely exceeding 0.000007 mw/m2.
At a distance of 25 - 100m from a mobile phone base station, power levels of 0.1 mW/m2 - 3.0 mW/m2 may be expected.
So mobile 'phone signals will generally swamp any television/radio ones.
A 1 square metre RF antenna would collect 0.1 - 3 watts of power.
At the same efficiency as current solar panels, it would produce 0.012 - 0.51 watts of power.

(The experiment in the paper was performed at 16000 mW per square metre RF power  :o )

Thanks for the maths on this...I'm just imagining having roof tiles that could harvest said energy (for the nights and days when solar panels aren't so good....

Your standard radio consumes much more power than it produces!

Yup - fully realise this...but intrinsically it does convert RF to another form of energy, although it's not for free.....and it's inefficient

An iPhone battery produces ~ 5.5 watts. @ 70% efficiency charging, it needs 7.8 watts to fully charge. An S3 battery produces ~ 7.98 watts, 11.4 watts to charge.

Use solar power to charge your 'phone, use USB to charge your 'phone but harvesting power from thin air won't charge your 'phone unless you're sitting under a mobile 'phone mast with an umbrella sized antenna and have 15 - 950 hours to spare!

It just seems a shame that there's only limited power available and it is cumbersome, inefficient, etc to try and collect it, as well as being "outdone" by some other energy capture tech...so as solar.

regards
Tim

[Woodles]

It just seems a shame that there's only limited power available and it is cumbersome, inefficient, etc to try and collect it, as well as being "outdone" by some other energy capture tech...so as solar.
regards
Tim

Well the output power of transmitters could be increased to make it worthwhile collecting the stray emmissions ... but we'd all be cooked to a crisp by then!  :D