I was watching some youtube videos on diy-hydroponics for the fun of it, and I ran across this video about building a diy climate control system. I have had the very same idea but just have not constructed one yet. Although I wouldn't be using solar power. Not that I don't like the idea, but the solar cells (of descent size) usually cost a pretty penny, and usually only last a couple of years. I'm waiting for the new type of solar cells to come out. They come in a roll, and roll out like a roll of wall paper but are like vinyl sheeting and can adhere to just about any surface, even curved surfaces. They are expected to be less expensive and much more efficient.
YouTube - DIY Homemade Hydroponics - S01E10 Climate Control
I would be using regular household electricity to power mine at this point. Both to run heating and cooling. But I have a plan to use propane burners for heating. I would still need to build the on and off system for the propane burners to be switched on by electricity. Much the same way a gas water heater works. For cooling I have 3 or 4 ideas that can all be switched on and off with the same type of setup, but I am trying to stay away from air conditioning because it would cost a fortune to cool a greenhouse here in the desert.