I've got a small emergency light battery and small solar panel and all I'd need is a charge controller to make it a totally self contained system. As far as the stuff in the plenum Back Again, it's just some scrap metal roofing painted black to pick up a little extra heat from that area. Just bent a 90 degree flange to mount it inside of each section of the plenum. Real simple.
If you look close you'll see that 2 tubes go into each section of plenum and the air makes one continuous loop throughout the entire system making it a run of about 35+feet not counting the plenum areas.
The only change I'd make next time, would be the single pane instead of multi pane glazing.
The unit is inside TRX so no issue with heated air going back outside and the thermal switch only activates the fan when it reach's 125 degrees inside the collector, and shuts it off at 85 degrees.
Now if we'd only get some sun,,we've only had 3-4 sunny days in the last month, so it's really hard to tell just what it will do at this point. But it did keep the house at 68 with the furnace off when it was 35-40 degrees outside,, that's promising. Every little bit helps.