Solar powered heater for greenhouse

[fwest]

I'm new to the site, and to solar power fundamentals. I'm interested in building a small greenhouse with as little impact on the environment as possible. I'd like to develop a solar system to maintain an even temperature. Unfortunately I live in Wisconsin. Any help in design issues would be greatly appreciated.

 

[FredGarvin]

What is your sunlight exposure like in the winter? I know of a lot of green houses that require no external heating during the winter months. The only temperature control is an adjustable window opening to control cooling flow.

 

[russ_watters]

How 'bout a solar powered fan connected to a thermostat?