Charging Your Mobile Phone Wirelessly

“Hello? Yes Ma, I want to tell you that I will be … *beep *beep *beep, dead battery.”

How many times have we encountered this surprisingly common scenario? As for me, I always end up searching for the nearest un-vandalized telephone booth. Sometimes I wish my phone came with solar cells so that I can recharge by leaving it under the sun or some portable battery mobile phone charger (I did see one which uses a 9V battery to charge, but its only for old Nokia phones).

Nokia did it. You can charge your phone anywhere, everywhere, even at night! How?

They developed a new prototype charging system, which collects the ambient and stray radio waves such as TV, radio and even mobile phone signals and convert them into electricity. The power currently harvested by the prototype is still quite far from the required power in order to keep the phone in standby indefinitely though, for now. Nevertheless, this is a good sign that it still has great potential.

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This conversion of wireless energy into an electrical form was actually demonstrated before by Nikon Tesla in 1893, in his attempt to build an intercontinental transmission tower to send power wirelessly across the Atlantic Ocean. Nokia’s version is a very simple version of it, with just a wide-band antenna and two circuits. The antenna and receiver circuits harvest signals from 500 MHZ to 10 GHZ and convert these EMG waves into electrical current and feed it into the second circuit. The feeder circuit will then feed the current to charge the battery of the mobile phone.

There is a problem though, these circuits have to use less power (power loss + consumption) compared to the amount of power harvested from the EMG waves. Currently, the amount that can be harvested is up to 5 mW. 20 mW is needed in order to charge the battery of the phone enough to keep it on standby mode indefinitely without doing any phone functions. However, for a meaningful charge, a power of 50 mW is needed.

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Nokia expects these phones to be out in three to five years time.

By the way, Palm Pre can be charged wirelessly via electromagnetic induction through its “Touchstone”. However, this still requires you to “dock” it to charge it.

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