Or, if your climate gets to -30F, my position is that you just can't keep fragile breeds unless you are willing to build a house for them where you can completely control interior climate and have a mechanical ventilation system like commercial poultry houses. Otherwise, keep breeds like Chanteclers, Orloffs, Jaerhons, Jersey Giants etc.. Keeping silkies, seramas and big combed Mediterranean breeds in frigid temps will only cause problems that some may find too daunting to continue dealing with.
If one must keep those fragile breeds, it would be cheaper to move to a warm climate.
Solar voltaic systems work great for lighting, electrifying perimeter fencing and operating automatic doors. However, solar can't be used for heating. It just takes too much energy to generate heat. To create sufficient heat in sub-zero temperatures would be impossible for a solar system without at least tens of thousands of dollars of equipment.
There are solar thermal options but they require different equipment than solar voltaic systems. For solar thermal, they only heat a space when the sun is shining and I can't envision anyone creating a stone or concrete heat sink for a chicken coop so that the system would retain enough heat to be of any benefit by dawn in January.