Solar air over water

[gadget]

I've been studying solar heating for a few years and have collected a dozen or so sliding doors to build a very large DIY array on the south side of my garage.

I have been trying to come up with a design that is reliable, cheap to build and durable. Something that can handle freezing and high temps. I never really came up with anything that could do all this.

Then one day it occurred to me, the problem is trying to warm the water inside the panel. I thought, why not warm air then use it through a heat exchanger(car radiator) to heat the water?

I would build metal screen style solar boxes and pipe that air into my garage so it can be ran through the radiator(s). The air could also be diverted for directly heating with air.

I found one company online that sells a hybrid setup that does exactly this but that is all I have found. Had anyone seen any other info on this? I would think it has been done DIY before.

Looking forward to any thoughts.

-Gadget