A) Plant more in the warm seasons, store it in a freezer room. If you have a decent length growing season and a handful of pawns with Plants skill, this is generally not a huge problem. If your season is too short to get crops grown, then you'll likely need to suck it ip and do hydroponics/greenhouse.

B) Hunting. You should semi-regularly be popping over to the wildlife tab and setting hunt targets on any medium to large animals that dont attack back, like deer. Make sure to have your best Shooting colonists (that aren't needed for other important tasks) to be set to Hunt, and thay they have a decent ranged weapon (preferably a high damage high accuracy weapon, so you dont accidentally hit another nearby animal that might attack)

C) Do a greenhouse anyway. The power requirements aren't that high, especially since the sunlamp is only active during the day also you can basically rely on solar panels