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Surface Finishing Tutorial

#194 Solar Collector Absorber Paints

Category : Special paints
October24, 2014

After the first oil crisis, the use of solar collectors that utilized solar heat spread rapidly.
Solar collectors utilize solar heat by absorbing it and using it to heat water. However, when the water temperature rises, inevitably a large amount of heat is released, lowering efficiency.

To prevent this, it is necessary to effectively absorb the short-wavelength light with high energy density from across the solar spectrum and convert it to heat to reduce long-wave infrared emissions.

Conventionally, black oxide treatment has been applied to the solar collector materials because black oxide efficiently absorbs solar heat; however, there is considerable heat loss from such collector materials owing to radiation.
This makes heat reflection necessary.
In other words, coatings with properties of a high absorption rate in the solar wavelength range (0.3 to 2.5μm) and low emissivity in the infrared wavelength range (3.0μm or above) are required.

To this end, solar collector absorber paints are applied.
The solar collector absorber paints are fine particles with semiconducting properties, such as copper oxide, manganese dioxide, cobalt oxide, chrome oxide, ferric oxide, lead sulfide and nickel sulfide, mixed into a binder such as near-transparent acrylic, silicone, or urethane.

Heat loss from the heat collector materials can be prevented by applying these paints to a surface of silver, aluminum, nickel, iron, stainless steel, or other metal with a high infrared emission rate, or to plastic materials deposited with any of these metals.

[Fig.1] Example of a solar collector

MISUMI USA eCatalog