I'm in the process of fixing all the mistakes and making changes to the panels that I didn't do when I started this project. I wanted to stay consistent otherwise if I kept changing them as I built the next panel it would have looked odd.
anyway, what I'm going to do is add copper water pipes so in the summertime I can switch from hot air heat to hot water. (preheat the water going to the water heater) Copper prices have come down but the pipe at menards is still very expensive.
I'm going to make one panel then switch it with one of the panels already up and continue until all the changes have been made.
My well water coming out of the well is 22 degrees F believe it or not, so I built a temporary solar water heater,
hooked it up to the water heater,
Stuck it in the sun, and two hours later the dang thing was working. In the picture above I would hold the pipes with my hands with the water running and my left hand would be ice cold and with my right hand it was too hot to hold on to. It was coming back in at 200F. But I learned I didn't have any volume of hot water in the pipes and I used 3/8 inch pipe which slowed down the water flow.
So my plan is to add 3/4 pipes inside these panels to hold a lot of volume of water, then I can switch from hot air heat in the winter to hot water in the summer.