[bennelson]

I've thought about a few of these same things for my house.

I like the solar shed idea. Also rocket-stoves work great, and are very simple technology.

Another thing you might want to consider is a gasifier. It's more complicated than a rocket stove, but burn REALLY CLEAN, create no waste but charcoal, (which has its own uses) and is real easy to connect to a boiler or other hot water system.

If you use solar hot water panels AND a gasifier - you could design a hybrid system where either/both heat water (antifreeze) that heats your garage.

The solar panels should keep your garage at a temperature level much nicer than the out of doors, and the gasifier could be run while you are working out there.

I know some folks doing pretty cool things with gasifiers. I can introduce you to them if you are interested.