You can scavenge car's alternators and use a water wheel or windmill to turn it. Alternators can work for a decade with minimum maintenance. Just have five or six stashed, just in case. They can supply 40A at 12V, or using a transformer to up the voltage, 4A at 120V.
Have you successfully run any modern hardware off of the irregular current coming out of something like that? You could charge batteries off of an alternator with a voltage regulator but I doubt any modern electronics are going to work well on current supplied by a jerry rigged water wheel and step up transformer. You’d be reliant on a lot of ICs to do it properly at a small scale.
Sure. If you have the input materials. If you're at the point of having to build an alternator by hand rather than just taking one off a car, I'd like to know where you're getting magnet wire, the machined shaft, the various rotor and stator parts, the end-bells, and the ball bearings.
Consider that you're not necessarily building from raw materials, you will be repurposing things you find around. Finding an alternator probably won't be a problem in the populated areas of USA but might be elsewhere - thankfully building it is still sufficiently simple.
