[mdorazio]

Parent post is probably referring more to energy resources. Gas and diesel degrade fairly quickly and unless you live in the middle east, aren't just flowing out of the ground anymore. Solar + BEVs might be an option, but only if the apocalypse scenario didn't involve an EMP, otherwise you better know your way around diesel engines and making biodiesel + live close to a hydroelectric plant.

[nostrademons]

Hydro, wind, and solar-thermal power is 100% renewable and can be made with 19th-century technology once you've worked out how to build a dynamo. There are some geographic restrictions but one of those power sources should be available in most regions. Plus most of the population has died off in a post-apocalyptic world, so your generators don't need to be nearly as big.

[bombcar]

Almost all power is generated by heating water into steam, which can still be done by burning almost anything. It won't be very efficient, but you can do it - so traveling to the nearest coal mine/plant may be an effective energy source.

[hef19898]

The most easiest thing, so, would be a Sterling engine then. Something I have to read up again, I'd love to build one with my kids. After all, it was the machinery we did hand-drawn technical 2D drawings for back at university before we moved to CAD.