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How to Build a Solar Absorber Plate

Solar absorber plates are dark-colored metal plates that absorb sunlight and conduct heat, decreasing the amount of copper tubing needed in solar collectors (See References 1). Solar collectors for water and heating systems need an absorber plate to convert as much sunlight into heat as possible. This is accomplished with smart material choices and careful construction.

Choose a Material
- Copper and aluminum are the best metals for building a solar absorber plate. Copper is the most efficient conductor and does not corrode as easily as aluminum. However, copper is expensive in large sheets. Aluminum conducts heat well and is lightweight. Many home-built solar absorber plates use sheets of aluminum flashing that can be found at local hardware stores (See References 2). Aluminum sheets that are 0.018 inches thick, or 25-gauge sheets, hold their form well. Thinner sheets can be used if they are bonded well to the collector piping.
Paint It Black
- Regardless of which material is used, color it black to maximize the amount of solar radiation it absorbs. Flat black paint will absorb around 96 percent of the solar radiation (See References 3). Thoroughly clean the metal to remove residual oil from the manufacturing process, and etch the entire surface with sandpaper or emery paper so the paint will better adhere. Cover the top side of the absorber with a primer, and then use a flat or velvet black aerosol paint as the top coat.
Bend the Metal Sheet
- Collector piping can be tied directly to a flat absorber plate. However, bending the absorber plate to form channels for the collector piping will place three sides of the piping in contact with the absorber instead of only one. Build a bending jig to help with the process. Leaving 1/2-inch spaces between them, screw 1-inch-thick boards onto a wooden base, and then pound the absorber plate metal into the grooves (See References 4).
Insulate the Absorber Plate
- The back side of the absorber that was not painted should be insulated to prevent heat from escaping away from the solar collector piping. The insulating material must withstand temperatures between 200 and 300 degrees Fahrenheit and be resistant to water damage. After the desired number of absorber panels have been aligned and you have attached the piping, line the back side of the absorber plate with around 4 inches of glass wool or other appropriate insulating material (See References 3).

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