posted on 2020-08-20, 13:06authored byM. Shiva Prasad, B. Sobha, Koppoju Suresh, Shanmugasundaram Sakthivel
Spectrally selective
absorber coatings (SSACs) have attracted tremendous
research attention owing to their high efficiency of conversion of
solar energy into heat with minimal emittance. In this regard, we
have developed a new spinel material (Cu(Mn0.748Ni0.252)2O4) as SSAC by the dip-coating
technique. The dual-functional layer (SiO2) is deposited
on a spinel absorber to serve as an antireflective and thermal barrier
layer for the improvement of solar absorptance and thermal stability.
The developed tandem absorber exhibits an excellent solar absorptance
(α) of 0.95, low spectral emittance (ε) of 0.14, and good
thermal stability up to 500 °C for 250 h. Additionally, the tandem
absorber has exhibited outstanding wide-angle solar absorptance with
a net enhancement of 5–74% over an angle of incidence ranging
from 10 to 80°. The developed coatings were widely characterized
by grazing incidence X-ray diffraction, thermogravimetric techniques,
high-resolution transmission electron microscopy, and Universal Measurement
Accessory to determine the properties. Our findings indicate that
the development of spinel-based tandem SSAC by the wet chemical method
may reduce the cost of solar thermal systems, and the wide-angle absorption
with high thermal stability may open the possibilities of high photothermal
conversion efficiencies.