A big thank you for all of the help and answered questions that I have received this past year. Just reading the different posts have been a ginormus (huge) benefit for me. Please keep the OT posts going as well. The ones that don't interest me I don't read, so far I have read them all. The work on my 24 fordor is moving ahead sloooowly, but still moving forward (no heat in garage).
Solar collector, a couple of old steam radiators, some pipe, a circulating pump and a sunny day and by noon you will be cracking the doors open to regulate the temp. Just set it up so that when you turn the circulating pump off all the water drains to a tank inside your garage.
Draining the water to a tank in the garage wouldn't do me much good. It's 11 degrees out there right now!
The reason to drain the water to the garage tank is so that it radiates its heat into the garage at night, instead of sitting in the solar collector sending its heat to the outdoors.