When it comes to power, Seattle is already one of the greenest cities in America, generating nearly half its electricity supply from renewable sources. Hydroelectricity, wind turbines, solar panels, biomass and waste incinerators will be familiar enough but scientists here have just managed to harness one of the nation’s last great untapped resources — television.

All terrestrial television broadcasts (as well as mobile phone, Bluetooth and GPS signals) are radio frequency waves carrying a small amount of energy. Intel Research Seattle, a division of the computer-chip maker, has designed a device that is able to convert those radio waves into usable electricity, in effect plucking free power from thin air.

Its so-called wireless resonant energy link (WREL) picks up broadcasts from a local news channel on a standard “rabbit ear” antenna and powers a digital weather station that normally requires an AA battery. Although it generates enough electricity to display temperature, pressure and humidity levels, the amount of energy harvested from a typical TV show is not enough to run, say, a mobile phone.

The system relies on the theory of resonance, using precisely tuned coils to amplify energy. With several years of development, Intel envisages that future phones and laptops could use its technology to keep their batteries topped up.

Another possible application for WREL technology lies in reducing the number of power cords around the home. Intel has already demonstrated a wireless power system that can light a 60W bulb from several feet away. It’s fairly efficient and, because it uses magnetic rather than electric fields, there’s no chance of anyone receiving an electric shock.

In the home of the future, all manner of cordless gadgets might have WREL receiver units installed, allowing them to refresh their batteries from a central transmitter without the need for cables, adaptors or chargers.

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