Spinel Cu-Mn-Cr Oxide Nanoparticle-Pigmented Solar Selective Coatings Maintaining >94% Efficiency at 750 °C

High-temperature concentrating solar power (CSP) system is capable of harvesting and storing solar energy as heat toward cost-effective dispatchable solar electricity. Solar selective coating is a critical component to boost its efficiency by maximizing solar absorptance and minimizing thermal emittance losses. However, maintaining a high solar-thermal conversion efficiency >90% for long-term operation at >= 750 degrees C remains a significant challenge. Herein, we report spray-coated spinel Cu-Mn-Cr oxide nano-particle-pigmented solar selective coatings on Inconel tube sections maintaining >= 94% efficiency at 750 degrees C and >= 92.5% at 800 degrees C under 1000x solar concentration after 60 simulated day-night thermal cycles in air, each cycle comprising 12 h at 750 degrees C/800 degrees C and 12 h cooling to 25 degrees C. The solar spectral selectivity is intrinsic to the band-to-band and d-d transitions of nonstoichiometric spinel Cu-Mn-Cr oxide nanoparticles. This feature offers a large fabrication tolerance in nanoparticle volume fraction and coating thickness, facilitating low-cost and scalable spray-coated high-efficiency solar selective absorbers for high-temperature CSP systems.

Automated summary

In this study, a solar selective coating material consisting of spinel Cu-Mn-Cr oxide nanoparticles was reported. The coating demonstrated high solar-thermal conversion efficiency (>90%) at temperatures exceeding 750 degrees C. The material showed stability after 60 simulated thermal cycles and offers potential for low-cost and scalable high-efficiency solar selective absorbers for high-temperature concentrating solar power systems.