By San Jose Mercury News
Article Launched: 04/20/2007

Apr. 20--Optical power beam: PowerBeam uses a powerful laser with a built-in safety system to transfer power by shining the laser on a solar cell attached to a laptop or other gadget. See more info at www.powerbeam.biz.

Induction: Start-ups such as Splashpower and WildCharge have been using a method dubbed "electromagnetic induction" to create pads that can charge batteries, even if they are only sitting on top of the pads and aren't plugged in by wires.

Electromagnetic resonance: Researchers at the Massachusetts Institute of Technology exploit resonance, which occurs when electromagnetic frequencies are applied to certain kinds of objects.

Radios: Powercast of Pennsylvania is using a radio technology to transfer power. More info at www.powercast.com.