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PhD Thesis Defense: Can Xu
10:00am - 12:00pm EST
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"Spinel-structure transition metal oxide nanoparticle (NP) pigmented solar selective coating with high thermal efficiency and high-temperature thermal stability in air"
Concentrating solar power (CSP) system is a green technology capable of storing the energy absorbed from sunlight and later converting it into other forms. As an indispensable component, solar selective coating targets at maximizing the solar absorptance and minimizing the thermal emittance loss. In order to reduce the levelized cost of energy (LCOE) of Generation 3 CSP systems towards 50% power efficiency, solar selective coatings are required to possess long-term thermal stability at high temperatures ≥ 750 ºC in air. However, there are still limited numbers of published works investigating long-time high-temperature air-stable solar selective coatings. Current commercial coatings are unable to maintain ηtherm>90% at operating temperatures >650ºC as well. Consequently, it remains to be a significant challenge for solar selective coatings to be fabricated by cost-effective methods and to maintain a high solar-thermal conversion efficiency > 90% for long-term operation at ≥750ºC.
Herein, we started from simple commercial oxide nanoparticles to our own synthesized spinel-structure three-transition-metal-incorporated oxide nanoparticles to form cermet solar selective coatings with higher optical-to-thermal efficiency. Facile co-precipitation method and hot spray coating methods are utilized. Cu-Mn-Fe, Ni-Mn-Fe and Cu-Mn-Cr oxide system were investigated and Cu-Mn-Cr oxide system shows the optimal photothermal performance.
To the best of our knowledge, we achieved a record-high thermal efficiency up to 94.2%, with a solar absorbance of 97.9% and a thermal emittance of 59.4% a temperature of 750ºC and solar concentration ratio of 1000. After 60 simulated day (12h)-night (12h) thermal cycles (a total annealing time of 720h) at 750ºC and 800ºC, the coatings showed superior stability with a thermal efficiency up to 94.0% and 93.2%, without change observed from the surface morphology or crystal structure. This study offers a promising approach to the high-efficiency, high-temperature stable and cost-effective solar selective coatings with feasibility of scaling up for the next generation CSP systems.
- Jifeng Liu, PhD (Chair)
- Weiyang Li, PhD
- Mark Laser, PhD
- Tianshu Li, PhD
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