Selective solar absorber coatings of carbon dispersed in SiO2, ZnO and NiO matrices on aluminium substrates have been
fabricated by a sol-gel technique. Spectrophotometry was used to measure the near-normal reflectance of the composite
coatings. Calculations of absorbed and emitted power, power retention, solar absorptance and thermal emittance were
performed from the reflectance curves. The root-mean-square (rms) deviations of the reflectance curves from the ideal
case were computed to determine the sample with the best performance characteristics. The thermal emittances of the
samples were 30% for the SiO2, 15% for the ZnO and 10% for the NiO matrix materials. The solar absorptances were
90%, 89% and 93% for SiO2, ZnO and NiO samples, respectively. Based on the results, NiO matrix samples had the
best solar selective behaviour, followed by ZnO and last were the SiO2 based samples.