Recycling energy

There is a lot of energy around, and is not doing anything else.
The first devices to be powered entirely by ambient energy are likely to be sensors, calculators and clocks. But the hope is that music-players, e-readers and mobile phones will eventually follow.
The aim is to harvest radiation from multiple sources.
Markku Rouvala, an engineer at Nokia Research Centre in Cambridge, England, harvested as much as 5 milliwatts of power using a wide band receiver capable of mopping up radio signals between 500MHz and 10GHz including radio, TV, Wi-Fi and mobile-phone signals from nearby transmitters.
Advocates of satellite solar power, for example, dream of beaming gigawatts of solar power down to Earth from geostationary satellites more than 35,000km up.
The same approach has been used in ground-based experiments to beam one kilowatt of power over a distance of several kilometers.
A little over a century ago, the inventor Nikola Tesla drew up ambitious plans to transmit electrical power without wires.
He carried out a series of experiments in which electric lights were illuminated via electrostatic induction, by connecting them to metal sheets suspended in a strong electric field produced by a distant transmitter.
In 1898 he proposed a world system of giant towers that would form both a global wireless communications network and a means of delivering electricity over large areas without wires.
Today several firms are pursuing various technologies that deliver electrical power without Wires.