Their lightweight wood-fired CampStove not only burns as hot as a propane one but also converts waste heat into electricity to charge any USB-powered gadget. SET THE FIRE

Campers pack a small handful of sticks into the bottom of the stove’s dual-walled steel combustion chamber and light the fire. One batch of kindling can boil a liter of water in five minutes.

FEED THE FIRE

A one-inch blower fan pushes fresh air into an angled vent near the bottom of the stove and circulates it counterclockwise through a half-inch gap between the combustion-chamber walls. The inner wall is perforated with 34 holes near the top and 11 more near the bottom. As air heats up, it expands and enters the combustion chamber to feed the fire.

GATHER ENERGY

A custom thermoelectric generator (TEG) converts heat into voltage. On one side of the TEG, a 1.5-inch copper-and-aluminum heat probe extends into the fire. On the other side, the fan cools a set of heat-sink vanes. As electrons move between the hot and cold sides of the TEG, they are directed into a set of wires.