By Ovidiu Sandru | 17 January 2011, 14:44 BST
TV and radio signals are electromagnetic waves, and all electromagnetic waves possess some amount of electromagnetic energy. All you need is an appropriate device to convert this energy into usable electricity
The schematic above is a device that you can build using simple components. It is a proof-of-concept device demonstrating that electricity can be generated from radio waves (basically a simple radio receiver, but tuned for energy harvesting).
The device consists of an antenna that is connected to a variety of devices such as capacitors, variable capacitors, inductors, diodes, chokes, and resistors in a specific order. Many of these components are grounded. At the other end of this network, the terminals keep providing electric current continuously. With a number of such devices, you could generate enough electricity for your home (obviously, one is by far not enough).
I've personally tried building the schematic in this video and succeeded getting small amounts of power (3 microamperes and 2 volts, but nevertheless proved the concept), and then tried the one in "Tesla's Secret." It contains an improved circuit that you can actually tune on different frequency ranges to get much more power (it's on page 25).
Source: The Green Optimistic