Wind and solar also don't work well for powering spacecraft, space stations, or anywhere else in the solar system further away from the sun than Earth. The surface of Mars or Ceres, for example.
Nuclear actually doesn't work well for spacecraft either, because there's no convenient way to get rid of all that excess heat. It might work well on Mars or Ceres, but solar isn't all that bad; you'd just need more panels for an equivalent amount of energy as you'd need on Earth.
For nuclear propulsion you just use the propellant to cool the reactor. You are still going to want to have a bunch of propellant with a fission or fusion reactor and, like a chemical engine, you can use it as a coolant when it enters the engine.
RTG's are pretty damn good for spacecraft. But they are dangerous to launch. The nice thing about fusion is that a RUD doesn't matter from a nuclear perspective.
I'm talking about spacecraft for humans. Going fast is much more important for humans than robots and nuclear is the only way to go. (BTW RTG's are also nuclear, just really low power and don't allow for adjustable output)
