Batteries to Draw Power From Ambient RF

June 11, 2009 by Rico Mossesgeld  
Filed under Peripherals

The concept is easy to understand: design a system that can create power from radio frequency energies to charge batteries. The potential for this is huge, since RF devices are practically ubiquitous—at least for those who need to charge batteries on a regular basis. WiFi and cellphone antennas are just some of the examples of RF-creating items that the proposed charging system can utilize. The full news report below:


Nokia Prototype Generates Power from Ambient Radiation
Shane McGlaun

Future Nokia devices may charge batteries without needing an AC outlet

Markku Rouvala, a researcher from the Nokia Research Centre in Cambridge, U.K., and a group of researchers are working towards a development that could lead to phones that are able to top off their batteries by harvesting power from ambient RF signals.

The type of radiation that the researchers are trying to harvest for the power comes from Wi-Fi transmitters, cell phones, TV antennas and other sources. Rouvala says that the prototype device that has been developed could harvest as much as 50 milliwatts of power. That amount of power would be sufficient to charge a phone that is switched off.

The current prototype is capable of harvesting only three to five milliwatts. Two passive circuits are required in the prototype device.

Rouvala said, “Even if you are only getting microwatts, you can still harvest energy, provided your circuit is not using more power than it’s receiving.”

Generating power in this method isn’t a new break through; the same method is used to generate power for wireless sensors and RFID tags. Technology Review reports that this year a researcher at the University of Washington developed a temperature and humidity sensor that was able to draw the power it needs to operate from a signal emitted by a 1-megawatt TV antenna 4.1km away, but the device needed only 60 microwatts.

Nokia’s plans are to generate much higher levels of power from ambient signals. To develop 50 milliwatts would need about 1000 strong signals and an antenna that can pick up such a wide range of frequencies would suffer from efficiency losses.

Researcher and physicist Steve Beeby works on vibrational energy. He said, “If they can get 50 milliwatts out of ambient RF, that would put me out of business.”

Nokia is mum on the details of its plan, but Rouvala says, “I would say it is possible to put this into a product within three to four years.”
The technology would not be used to power a phone alone; it would be combined with other energy-harvesting technology like solar cells. This sort of power generating technology would be especially welcome on Nokia handsets designed for emerging markets.

(Image courtesy Encyclopedia Britannica)

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