Nokia is developing technology that could draw enough power from ambient radio waves, so we don't need to charge the battery. Ambient electromagnetic radiation, the sort of stuff that is given off by our WI-FI transmitters, Mobile phone antenna and even giant TV mast, could be harnessed and converted into sufficient electrical power to top our battery simply as we walk. The Nokia devices will work as the same principle as a crystal radio set by converting electromagnetic waves into an electrical signal. The way that crystal set radio works, it uses no power. The circuit consists of an inductor (called a coil), a variable capacitor, a germanium diode, a filtering capacitor and finally very high impedance headphones. Rouvala, a researcher from the Nokia Research Centre, in Cambridge, U.K, said that the prototype needs to harvest 50 milliwatts of power in order to charge the phone with power. With today's technology, the prototype is able to harvest only three to five milliwatts. Therefore, as it mentioned in the article, Nokia needs a wideband receiver to capture signals from between 500 megahertz and 10 gigahertz; a range to cover many different radio signals. As it mentioned other universities are working on different projects related to use the power that the device is capable of harvesting from ambient RF.
"Earlier this year, Joshua Smith at Intel and Alanson Sample at the University of Washington, in Seattle, developed a temperature-and-humidity sensor that draws its power from the signal emitted by a 1.0-megawatt TV antenna 4.1 kilometers away. However, this only involved generating 60 microwatts.
Smith says that 50 milliwatts could require around 1,000 strong signals and that an antenna capable of picking up such a wide range of frequencies would cause efficiency losses along the way." It has been mentioned that it is possible to see this capability in the cell phones within three to four years. According to the other article this technology is not going to be used only for Nokia but it should be used for any other devices which are capable of working with the less power. Nokia plans to use this technology in combination of other energy-harvesting approaches like solar cells that could be embedded in the outside case of handset.
This technology, harvesting ambient electromagnetic radiation and converting to electrical power, would be the best one for most of the cell phone users. I personally will get the phone that has this technology so I wouldn't need to carry the cell phone charger with myself, since sometimes I will forget to charge it. But there is a question regarding that, is this technology depends on the atmosphere condition or not? Some researchers on the ambient radiation, in Hong Kong, agreed that the radiation level will be changed depends on the weather condition. According to the rain, wind, tropical cyclone, and even seasonal changes make changes to the radiation level. Therefore, I believe it's not going to work perfectly for all over the world.
Source:
http://www.technologyreview.com/communications/22764/
Other Sources:
http://www.dailytech.com/Nokia+Prototype+Generates+Power+from+Ambient+Radiation/article15382.htm
http://www.weather.gov.hk/radiation/tidbit/200512/ambient_radiation_level_e.htm#
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