#Sure. It's called a Radioisotope Thermoelectric Generator (RTG)
Sure. It's called a Radioisotope Thermoelectric Generator (RTG)
They can be small, last a really freaking long time, and require no maintenance as it has no moving parts. One the size of a portable gas generator (we're still talking 100 pounds here, but load it into a truck? Absolutely) can output enough power for a small home. One or two could easily supply a tribe of nomads with enough power for a stove and some lights.
Downside, they're not terribly efficient (about 7%; yuck) and their power output drops over time (about 0.8% per year) as the radioactive material decays.
I can't find the story now, but there was a report of two fellows who found this device that seemed to generate free energy. Perpetual motion sort of deal. They had no idea what it was and used it to power their house for around a decade. Later turned out to have been a Russian RTG that fell off the back of a truck.
Besides powering Russian lighthouses, they're frequently used in space probes due to the long lifespan and minimal maintenance. Voyagers 1 and 2, Galileo, Ulysses, and New Horizons all have one. Voyager 1's operational capacity was 470W at launch and by 2001 it would have dropped to 315W.