Unfortunately RF energy harvesting is not free.
As many harvesting devices, as higher the RF energy required to be radiated
for properly run the other communication devices.

The ground+antenna powered MW radios in the early radio ages is just a
simple example of free RF harvesting.
That resonant LC circuit it was able to light easily a LED. The problem was
in that time (1965-1975) that LED was not available yet. Now you can power
the internet of things thing, even with a MW radio oscillating circuit.
Not too fancy because the ferrite antenna is quite big.

Vasile


On Wed, Sep 30, 2015 at 7:06 PM, Charles Craft <chucksea@mindspring.com>
wrote:

>
> http://arstechnica.co.uk/gadgets/2015/09/freevolt-perpetual-free-rf-energ=
y-harvesting-to-power-the-internet-of-things/
>
> I think I've learned here on the piclist to run when the words "perpetual=
"
> and "energy/power" are used in the same sentence. :-)
>
> "Freevolt harvests free volts (!) from a wide variety of RF radiation
> sources, which can then be used to power the various sensors and
> microcontrollers that make up the (are we there yet?) Internet of Things.=
"
>
>
>
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist
>
--=20
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.