[Daox]

I would highly recommend using solar hot air panels. They're inexpensive to make, operate automatically and require no fuel. They're what I want to use when I eventually insulate my garage (used for working on cars, rarely storing as well haha). If you need a more on demand type heat I'd recommend a wood stove since you do wood working and could burn scraps as well as brush from the yard (or if you've got woods around the house that is all fuel).