MOTHER'S Fluorescent Tube Solar Collector

Here's a design for an 83% efficient solar collector that uses old fluorescent tubes.

| September/October 1978

Here's yet another simple, easy-to-build, inexpensive, "make it from scrap" solar collector from the talented folks at MOTHER EARTH NEWS' Research Labs. Tests indicate that the unit operates at efficiencies as high as 83% ... and you can put one of the collectors together for only about $52 (less than $2.00 per square foot).

Start this project by rounding up a healthy supply of burned-out 96"-long fluorescent tubes (available for free from offices, factories, stores, shopping centers, dumps, etc., all over the continent). You'll need 29 of the tubes altogether for your finished collector, but it's a good idea to pick up a few extras in the beginning just to allow for breakage.

Puncture the metal or plastic ends of the long lights to relieve the vacuum inside, then use the special cutting tool described in MOTHER'S Fluorescent Glass Tube Cutter to remove one end from each tube. Next, pour some sharp sandblasting sand into the cylinders and tip them back and forth repeatedly until all the coating has been removed from their insides. Then cut enough off the other end of each cylinder to leave you with pieces of clean, transparent glass tubing, each 85" long and open on both ends. Finally, paint all 29 of your glass cylinders flat black inside and out (use a cotton pad, pulled through each tube with stiff wire, to spread the paint deep inside).

To help with the remainder of the assembly process, we've prepared this Fluorescent Tube Solar Collector diagram.

Next rout a 1/8" X 3/8"-deep groove in the sides of the collector box, rabbet its corners, trim the paneling to fit, and fasten the whole box together with wood screws. Cut one of the remaining 1 X 6's into four pieces and screw them to the bottom of the frame as additional support for the collector's back. Then, using water glass as glue, attach aluminum foil (shiny side up) inside the bottom paneling.

Cut the two 1 X 6 tube holders down to a width of 5 1/8", then draw a line down the middle of both boards and—starting 9/16" in from one end—mark the 29 center points (1 9/16" on centers) for the mounting of the modified fluorescent tubes. Next, drill out all the tube mounting holes with a 1 1/2" hole saw and cut the two boards apart on their center lines. One half of each holder should then be securely fastened inside the collector box (5 1/8" in from each end). Finally, lay a bead of silicone sealant along the surface of the holes in the mounted half-holders, set each cut-and-painted glass tube in place, spread sealant on the holes in the other halves of the holders, and—while the top halves of the holders are held snugly down on the tubes—attach the scalloped pieces of wood to the sides of the box with wood screws.

Michael Cassidy
5/6/2012 8:15:47 PM

Mother Earth should probably remove this article. It was written before we knew the danger of improperly disposed of mercury! Anyone that does this project is not only illegally disposing of mercury, they are also exposing themselves to high levels of mercury and it does not go away, it just builds up in your body and can have serious health effects. There are many other ways to build a solar air heat collector than this very dangerous method. Please remove this article so no one mistakes it for a safe project.

7/11/2009 10:43:30 AM

Exactly what is this solar collector supposed to collect - water or hot air? What kind of working application is this for? You did not make this clear!

12/22/2007 11:36:18 AM

What about the mercury that these tubes contain? Are you just dumping it?

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