From drain to gain

Mobile phone today is not solely a communication medium, but rather become smarter in handling multi-tasking activities than just talk to your friends. Not only time scheduler, notes and push mail but now people getting more advance in making their computer applications go to mobile. As the need to connected always has been greatly become important (to link to facebook, myspace…), WIFI is among the best options they have to fulfilled such need.

However, the biggest problem is on cell phone battery life. Even a simple changes to the software running on Wi-Fi access points could significantly extend or even double cell phone battery life. That’s the finding of a study that investigated why using Wi-Fi on a cell phone, and on some other portable devices, sucks up power so quickly. It found that a protocol designed to reduce Wi-Fi power drain often doesn’t work effectively.

Recently, Nokia says it’s developing technology that could draw enough power from ambient radio waves to keep a cell-phone handset topped up


Ambient electromagnetic radiation–emitted from Wi-Fi transmitters, cell-phone antennas, TV masts, and other sources–could be converted into enough electrical current to keep a battery topped up, says Markku Rouvala, a researcher from the Nokia Research Centre, in Cambridge, U.K. Rouvala 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.

To increase the amount of power that can be harvested and the range at which it works, Nokia is focusing on harvesting many different frequencies. “It needs a wideband receiver,” says Rouvala, to capture signals from between 500 megahertz and 10 gigahertz–a range that encompasses many different radio communication signals. Historically, energy-harvesting technologies have only been found in niche markets, powering wireless sensors and RFID tags in particular. If Nokia’s claims stand up, then it could push energy harvesting into mainstream consumer devices.

Wow….this would be a great achievement if the ‘power through wireless’ can be done. But what happen when the guy is using his VOIP service while charging his mobile ‘on air’. Will it drain his brain? will the electromagnetic conversion endanger human brain?