Already a method used in myriad applications, coil coating is now being used to apply coatings that help capture the power of the sun. The paint application method is being used to apply selective absorber coatings to aluminum strip for thermal energy applications at solar power plants. The process provides the precise layers of coatings needed for high performing solar absorber coatings.
According to Cleveland-based National
Coil Coating Association, the coil coating process is well suited for specialty
coatings used for solar energy because of the optimal surface preparation,
coating adhesion and continuous control that are inherent to this process.
By using the coil coating process, thin
coatings can be applied uniformly to metal strip, so a highly selective coating
and several functional coats can be applied in precise, thin layers. The
functional coats often include functional particles such as nanoparticles,
metal particles, metallic oxide particles and pigments. Each coat has a job.
For example, one layer may absorb short-wave solar radiation while also being
transparent for long-wave radiant heat. The result is conduction of short-wave
solar radiation converted into long-wave radiant heat, so the absorber plate is
heated up as needed. Outside coats can be reflective for radiant heat so the
absorbent coat emits little radiant heat to the outside. Additional coating
layers provide humidity and temperature resistance to protect against
corrosion. Other layers provide adhesion promoter properties that improve the
endurance of the coating in the intense sun.
With the coil coating process, the
coating thickness can be adjusted precisely by means of the gravure on the
roller coaters and relative speed of line coil coating line. After coating, it
is also possible to apply embossing to the painted metal in order to increase
the absorbent surface without tears developing in the coating.
Coil coating is a continuous, highly
automated process for coating metal before fabrication. In one continuous
process, a coil of metal up to 72" wide moving up to 700 ft/min, is
unwound, cleaned on both the top and bottom, chemically treated, primed, oven
cured, top coated, oven cured again, rewound and prepared for shipment.