Experimentally and numerically investigation of the effect of CuO:Cr2O3 nanoparticles in a carbon ash coating on flat plate collectors, enhancing the absorption of solar energy collection

The present work, a new nanocomposite film of carbon ash (C) doped nanoparticles (CuO and Cr₂O₃) at various concentrations was synthesized by a spin coating method. Tested across 238–900 nm wavelengths. These films aim to make a nanocomposite film as a coating over the flat plate collector to absorb the solar energy. The optical properties and Urbach energy were computed, and the analysis of scanning electron microscope/energy dispersive spectroscopy of carbon ash was used to illustrate the elemental compositions. The energy gap decreased from 3.95/1.4 eV, while Urbach energy increased from 12.35/34.48 eV as the disorder increased in the band gap. The atomic force microscope illustrated that the roughness increased from 2.73/9.33 nm, while the root mean square increased from 3.48/11.4 nm. The high dielectric constant increased from 1.893/3.330, the carrier concentration per effective mass values decreased from 8.193 × 10⁶¹/0.0511 × 10⁶¹ (kg. m³)⁻¹. The effective single oscillator energy values increased from 5.22/11.89 eV, the dispersion energy increased from 8.63/18.97 eV, the oscillator strength increased from 3.473 × 10¹³/14.68 × 10¹³, and the oscillator wavelength, decreased from 237.61/104.23 nm. The static refractive index decreased from 1.712/1.511, and the frequency dielectric constant decreased from 2.961/2.280. Linear susceptibility decreased from 0.156/0.127 esu, and non-linear susceptibility increased from 0.1012 × 10⁻¹⁴ to 4.421 × 10⁻¹⁴ esu. The computational fluid dynamics tools in ANSYS FLUENT were used to design a flat plate collector with a thin film nanocoating to predict heat loss efficiency and fluid temperature, and to increase the absorption efficiency of solar radiation to 67 %. These films coat flat plate collectors, concentrating thermal systems, optoelectronic devices, and dissipating heat from electronic systems.