Carmakers learned years ago it's not easy to make a practical hydrogen fuel cell. Yet hydrogen fuel cells do work, and they're greener than batteries. So how about using a mini hydrogen fuel cell to recharge something small—like your mobile phone battery?

That's the idea behind SiGNa Chemistry's PowerTrekk, demo'd at the recent Consumer Electronics Show in Las Vegas. The device is filled with a powdery substance known as sodium silicide that produces hydrogen gas in the presence of water. It has the same recharge power as six AA batteries, minus the heavy metals and toxic chemicals.

The downside? PowerTrekk will cost about $200 when it debuts in the U.S. in May.

A cheaper option, also on display at CES, might be the nVolt by startup company nVolutions. Due out by the end of the year and expected to cost about $50, nVolt has a circular plate that attaches to the back of any mobile phone. Once attached, put your phone on a flat surface and spin it. nVolt uses kinetic energy generated by the rotations to do the re-charging. There's nothing greener than a little elbow grease.

—Larry Greenemeier

[The above text is a transcript of this podcast.]

