Quite some time ago I became obsessed with interstellar travel, and no matter how unrealistic it seems, I keep making progress on the subject. The latest improvement to my starship incorporates Aerogel as a nutrient growth medium for plants. This hydroponic growth medium has a density of just 75 kg / cu.meter and has resulted in a starship with 1/8th the mass of previous designs which used ordinary loam for space-based agriculture. The result is a faster ship, shorter on-orbit assembly time, less stringent propulsive requirements, and generally a more feasible starship.

The only drawback of a less massive ship is the need for speedier emergency measures during power failure, or other heat management failures. This is simply because temperature changes will occur more rapidly with less mass to retain heat.

I've also included a short set of links on renewable energy:

Starship Generations