In case of nuclear winter, I don’t think renewable energy is going to be the main concern.
However, it is possible to put solar panels on satellites that transmit the energy down to the surface. It’s costly and dangerous, but a benefit over surface solar is that the satellites can point at the sun for longer time during days and send the energy to places that are not in the sun, thereby producing solar power 24/7. It’s wildly impractical and expensive, but in case of nuclear winter it may be a realistic solution.