Absorber Plate Construction 

Solar Collectors use absorber plates to increase collector efficiency. Absorber plates do this by increasing the surface area exposed to sunlight. More than 700 linear feet of copper tubing would be required to cover the same surface area that could be covered with 60 linear feet bonded to a well-constructed absorber plate. Individual aluminum heat fins, normally used with radiant floor heating systems, may also be used to assemble the absorber plates used in a serpentine collector. A 4x8 collector would require sixteen 6"x20" heat fins. An absorber plate may also be constructed from two 10' x 20" sheets of aluminum flashing commonly available from construction suppliers such as Home Depot. 

Copper absorber plates may be soldered directly to Copper flow tubes, but a 4'x8' sheet of copper is expensive and the soldering process is tedious. Serpentine collectors that use either Copper or PEX bonded to Aluminum are cost effective.
PEX tubes may be installed under aluminum absorber plates and staples may be used to hold the PEX against the aluminum. An alternative to this method involves the installation of a copper flow tube  on top of the aluminum. The on-top installation is made possible by the ridged nature of copper held down with side and central supports.

This method of serpentine collector fabrication was specifically designed  for 3/8" copper. If you have a preference for PEX check out GARY'S  PEX Collector or learn about Modified Trickle Down Solar Collectors that do not use metallic flow tubes  or metallic absorber plates.  







With a little luck a finished serpentine collectors may look something like this. A 50' roll of 20 " wide .0086 gauge flashing is enough to make the absorber plates for two 4x8 collectors with a 10' piece of aluminum left over.  Click on the left illustration for more information on this serpentine collector.



   
Let's now focus on the fabrication of the 20" x 94" absorber plate.



Tools and Materials     

   1. Aluminum flashing  .0086" x 20" x 50'  for two 4x8 collectors
    2. A pounding jig made from 1x6 boards and 1 1/4" drywall screws.
   
3. A heavy mason's hammer.
    4. Tin snips.
    5. Six 7/16" steel rods about 24" long.

















Fasten the top layer of boards to the base platform with 1¼-inch drywall screws. The most important consideration in the construction of this jig is the spacing between the boards. The ½ inch spaces should be centered 6 inches apart, and the pounding jig should look something like this when you’re done. 
Side supports act as guides that hold the aluminum straight while pounding. Since the aluminum is 20" wide. I recommend boards 20.2" This will allow a little wiggle room between the guides. Of course the 20.2" boards are perpendicular to the 48" boards and the 20.2 boards should be parallel to each other with 1/2" slots between them. Use 7/16" rods to help space the slots. After 15 bends are made in the aluminum  the distance between the first bend and the last bend will be about 90" for a 4x8 collector.

  

Without the guides pounding grooves into the aluminum is tedious.  

See what I mean?  The jig with side supports is easier to work with and the finished absorber plate also looks better.

 

 

POUNDING OUT ABSORBER PLATES

 

STEP ONE Lay in a 20 inch wide sheet of aluminum. This one is 50 inches long. long but you’ll be using one that’s 10'long. Just slide the 10' long sheet of aluminum through the jig after the first 10 slots are pounded into the jig. 






 

STEP TWO: Place the 7/16 inch steel rods in the slots.

 












 

STEP THREE:  After the first rod is pounded into position it’s held in place with a piece of plywood that you’ll kneel on so that the next rod may be pounded without disturbing the first. This process may be repeated until all the groves are placed in the aluminum, To pound grooves in sheets longer than a jig simply shift the sheet down and place the last groove from the last slot into the first slot. 















 

   

Congratulations on hammering out your first absorber plate. May this be the first of many… All you have to do now is pound out 7 more and you’ll have enough collectors for a  96 sq ft array. Keep on trucking. Connecting with the sun is not always an easy alternative but it is our only alternative if we are to live in harmony with our planet and the forces of nature. If closed loop serpentine collectors seem a little to messy for your taste you could always explore the possibilities of MTD solar heating or other green energy alternatives.                  

 

              



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