There are two priorities I keep in mind, when thinking about collapse-time technologies.
- Maintenance complexity, especially in long-run context.
- Shortening the supply chain.
When it comes to electric power generation and various types of generators, I am very reluctant to accept generators based on rare-earth magnets. First, they are "bloody metals" indeed, mined and refined with extreme hurt to the planet and people. Second, their delivery chain is long and quite centralised which makes them possibly unavailable in case of disruption of the logistic system. While we wait for the US-sponsored program to develop alternative materials, still we can explore two avenues of research:
- magnets recycling
- generator constructions that does not need such magnets.
The recycling topic deserves separate consideration, in respect to a hypothesis of the "scavengers civilisation" as the next stage of human history. Meanwhile, we can have a closer look at constructions, using much more sustainable ceramic (aka ferrite) magnets, or no magnets at all.
If we can develop a "DIY" technology to make ceramic magnets, we can combine it with designs from 19th and early 20th Century and create alter-futurist line of more collapse-friendly electricity generators.
If we were starting from scratch, iron is about as common as it gets, geologically, not to mention how much "leftover" iron and steel there would be, post collapse. Barium/strontium for sintering ferromagnets is trickier, but ores like witherite and baryte aren't uncommon, though they are quite location specific, globally speaking. Not that you don't actually need full blown permanent magnets, just ferromagnetic material.
However, the easier (though less efficient) option would be to use dynamos with field coils instead of ferromagnets. That way the only resource you need is wire.
Ya, while more efficient, using permanent magnets was relatively rare for motors and generators until recently, and is very rare when it comes to large scale generators. Not only is it extremely expensive, but permanent magnet generators have trouble dealing with damping reactive power and high frequency grid oscillations.
You do see them more frequently in smaller generators, like wind turbines or micro hydro, as well as DC motors, but for things like dams and thermal sources not so much.
Most large three phase motors, the kind you need for agriculture and industry, also tend to use field windings, though permanent magnet ones arn’t nearly as rare.
If rare earths became a lot more difficult to source it would be inconvenient for some industries, especially for wind and solar expansion, but by and large I doubt most people would notice.