I'm going into coop next year so my work term would start next January. Does that mean that when i pick courses for next year on solar, I only pick fall courses? If I don't get a coop placement, wouldn't it be too late by then to choose courses for the winter term?

I'm doing co-op in January too, and it let me sign up for fall courses only. I was also thinking about taking a night course in 2nd term, so it let me register in courses in 2nd term. You shouldn't be planning that you won't get a co-op placement! Just start early and you'll be fine!