Standby mode is often accused of being the scourge of the planet, insidiously draining resources while offering little benefit other than a small red light and extra convenience for couch potatos. But now Nokia reckons a mobile phone that is always left in standby mode could be just what the environment needs.

A new prototype charging system from the company is able to power itself on nothing more than ambient radiowaves – the weak TV, radio and mobile phone signals that permanently surround us. The power harvested is small but it is almost enough to power a mobile in standby mode indefinitely without ever needing to plug it into the mains, according to Markku Rouvala, one of the researchers who developed the device at the Nokia Research Centre in Cambridge, UK.

This may sound too good to be true but Oyster cards used by London commuters perform a similar trick, powering themselves from radiowaves emitted by the reader devices as they are swiped. And similarly old crystal radio sets and more recently modern radio frequency identification (RFID) tags, increasingly used in shipping and as antitheft devices, are powered purely by radiowaves.

The difference with Nokia’s prototype is that instead of harvesting tiny amounts of power (a few microwatts) from dedicated transmitters, Nokia claims it is able to scavenge relatively large amounts of power — around a thousand times as much — from signals coming from miles away. Individually the energy available in each of these signals is miniscule. But by harvesting radiowaves across a wide range of frequencies it all adds up, said Rouvala.

Wonder if I could use this tech to keep my coffee warm.