Came across this today:
http://biolitestove.com/campstove/camp-o.../features/
It appears to be a small camp stove equipped with a thermopile.
A thermopile is a device that generates useful amounts of electricity from the effect of different metals in contact at different temperatures. Heat flowing from the hot stove to the cold outside generates electricity in the thermopile.
I wasn't aware that there were any small commercial units available.
2W is enough to be useful for charging a portable radio / GPS / Phone / torch.
Disadvantages:
- It's expensive
- The inclusion of a battery suggests a limited life (the thermopile itself should last for decades)
- The inclusion of a fan suggests an opportunity for failure
- Not fully waterproof
Still despite that I'm tempted