By using the ambient electromagnetic radiation (AER) in the air, Nokia thinks it can enable cell phones to draw power from the air by 2013, meaning millions of phone chargers would no longer need to be manufactured.

In an article in MIT's Technology Review published this week, Nokia's Research Centre in Cambridge, U.K. explains that its researchers have developed a way to convert AER from already existing structures like TV antennae, radio towers and wi-fi transmitters into enough juice to potentially charge a powered-off cell phone.

From the article, by Duncan Graham-Rowe:

[Markku Rouvala, a researcher at Nokia's Research Centre] says that his group is working towards a prototype that could harvest up to 50 milliwatts of power--enough to slowly recharge a phone that is switched off. He says current prototypes can harvest 3 to 5 milliwatts.

The Nokia device will work on the same principles as a crystal radio set or radio frequency identification (RFID) tag: by converting electromagnetic waves into an electrical signal. This requires two passive circuits. "Even if you are only getting microwatts, you can still harvest energy, provided your circuit is not using more power than it's receiving," Rouvala says.

If the researchers are successful, that could make a huge dent in the number of cell phone chargers that get produced (and discarded) every year; in February, the GSM Association, a mobile-phone industry group, estimated that 51,000 tons of cell phone chargers end up as e-waste every year.

In addition to innovations in how mobile phones draw power, another innovation in how we charge our gadgets is coming from Green Plug, a group that wants to spread one type of charger for all types of gadgets.

A lot can happen in the next four years, especially since the GSMA is going to adopt a universal charging standard by 2012, but if Nokia can get it right, surely the greenest charger is the one that you don't have to make.

Phone photo CC-licensed by Flickr user timtom.ch.