How would you picture a space-based society that uses 100% renewable energy?

This was a topic of conversation I had with a friend the other day and I ended up really upset because we couldn't seem to find common ground, so I guess I'm bringing it here in the hopes of a more civil discussion.<br><br>So often when I see people talking about renewable energy, it's about wind power, solar power and nuclear power. I don't think hydro power can be used outside of earth (at least not on the same scale) and geothermal energy might be possible but I wouldn't know so I won't discuss it.<br><br>So, in a space society, what would be the best way to generate energy? I think nuclear power is the best choice but I'd love to hear some arguments against it.