Solar air heater

I've always wanted to build a solar air heater using mostly recycled parts. So many products have packaging that could easily live a second life after it's initial use, and my goal is to build a scalable solar heater harvesting components from beer cans and plastic pop bottles. This would give two advantages...
1) with the scalable nature of the project people could build a simple unit or expand if they find the time/energy required is worth the input.
2) using as much recycled components would reduce costs and recycle materials ending their intended one time use.

The first version will use printed pieces that will connect the individual harvesting tubes. 3D printing these parts really helps with the inventive process, allowing me make slight adjustments to size and design, once I have the component locked down I eventually see this pieces being made from harvested wooden shipping pallet planks.