harvesting energy

[DJ Delorie]

> Due to our battery-management system, it is impossible to charge an
> XO laptop in less than about 110 minutes.

Are humans better at shorter bursts of higher power?  Perhaps a
human-powered charging system would benefit from some intermediary
storage, either electrical or mechanical - supercaps, water tanks,
gravity, springs.  Wind a mechanical spring, let it unwind for the
next N minutes while you take a break, repeat.