There are several options how to make harvested energy work for interstellar travel
1. Just beam it with a huge laser to the spacecraft (google for several proposed projects already in development and plans for launch)
2. Store it onboard the spacecraft and then use, with multiple options and different levels of today's technology feasibility like creating a small spinning black hole or creation of exotic matter for warp drive
1. Just beam it with a huge laser to the spacecraft (google for several proposed projects already in development and plans for launch) 2. Store it onboard the spacecraft and then use, with multiple options and different levels of today's technology feasibility like creating a small spinning black hole or creation of exotic matter for warp drive