Solar energy is large in total quantity reaching a wide area, but it is thin energy having a small energy density. For its use, there is a need for collection of light or collection of heat. Ideal light selective absorption films excel with increasing absorptance (α) in the solar wavelength region (0.3 - 2.5μm) and decreasing emissivity (ε) in the infrared wavelength region (3.0 - 20μm).
In consideration of thermal stability, black nickel plating and black chromium-based plating have excellent light selective absorption.
|Type of plating
|Black chromium plating
||- Absorptance (α): 0.90～0.96
- Emissivity (ε): 0.11～0.16
|Various uses of solar heat/air-conditioning, hot-water supply equipment
|Black nickel plating
||- Absorptance (α): 0.91～0.94
- Emissivity (ε): 0.07～ 0.11
(From “Kino Zairyo Nyumon,” Motofumi Honma, et al., Agne)
Black chromium plated solar collector
(From “Denki Mekki Gaido” edited by Federation
of Electro Plating Industry Association, Japan)
Emissivity of solar light absorption plate of black plated plating film
(From “Hyomen Shori Kogaku” edited by the Surface Finishing Society of Japan, Nikkan Kogyo Shimbun Ltd.)