I got into playing around with the power generation aspect of peltier junctions for awhile in college. While they product a temperature differential under applied current they also are capable of producing a current if there is an applied temperature differential.
Generator test setup.
Test setup number 2. We're still working on creating a environmentally friendly heat source at this point, but right now a candle in the brushed aluminum cylinder there works great.
Currently looking at alcohol, and wood stove pellets as possibilities.