Maybe use an RTG - just for maximum extremeness? https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator https://en.wikipedia.org/wiki/Radioisotope

Maybe use an RTG - just for maximum extremeness? https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_ge... Edit: You could just cut out the generator bit and have a nuclear iron.