DIY Tube collectors
There are some unanswered questions here, and I've never tried doing this, but since I couldn't help noticing one could possibly make concentrating tube collectors for 1/10th of Navitron's prices, I thought I'd float this uncertain idea out here and see where it goes.
- Take some 1.5" fluorescent tubes, and cut off each end, leaving you with lots of glass tubes.
- Unsharpen the cut ends.
- Pull a rag thru each tube on the end of a wire to rub the phosphors off. They come off easily.
- Cut strips of silvered mylar, and string each strip of greased mylar out between 2 wires with circles of wood on the end, so you get a gutter-like shape. Apply a grease that wont melt at 100C.
- Thread a glass tube over each mylar strip, and press the mylar into place against the glass.
- Fab some end stops for the glass tubes. These wont be airtight, the tubes wont be vacuum insulated, just glazed. Flat discs of plastic would probably do.
- Mount tubes onto your wall or roof, horizontally, using pipe clips to hold the 10mm pipe inside, and bigger pipe clips to hold the glass tubes. Turn the tubes to face the sun. Mount them above each other, all horizontally. The 10mm microbore can be bent rather than jointed at each end. Insulate the metal tubing bends.
We now have a single glazed concentrating collector, with roughly
10mm:32mm concentration factor, or 3:1. Cost is 10mm pipe, pipe clips, a glass cutter, some pipe insulation and time.Concentration will be similar to commercial vac tubes, insulation as standard flat plate collectors, and price would be a small fraction of Navitrons, and probably cheaper than flat plates. This means for much less money you can have twice the panel area and a lot more output.
Your turn to tell me all the problems with this untried idea.
NT