Abstract
Exploring the spectrally selective absorbers with high optical performance and excellent thermal stability is crucial to improve the conversion efficiency of solar energy to electricity in concentrated solar power (CSP) systems. However, there are limited reports on the selective solar absorbers utilized at 900oC or above. Herein, we developed a selective absorption coating based on the ultra-high temperature ceramic ZrC and the quasi-optical microcavity (QOM) optical structure, and experimentally achieved the absorber via depositing an all-ceramic multilayer films on a stainless steel substrate by magnetron sputtering. The prepared multi-layer selective absorber demonstrates an excellent high solar absorptance of ∼0.964 due to the multi absorptance mechanisms in the QOM, and a relatively low thermal emittance of ∼0.16 (82°C). Moreover, the coating can survive at 900oC in vacuum for 100 h with a superior spectral selectivity of 0.96/0.143 (82°C) upon annealing, resulting from the introduction of ultra-high temperature ceramic ZrC in the QOM structure. Under the conditions of a stable operating temperature of 900°C and a concentration ratio of 1,000 suns, the calculated ideal conversion efficiency using this absorber can reach around 68%, exceeding most solar selective absorbers in previous reports.
Highlights
Over the past decades, to alleviate the increasingly severe fossil energy crisis, the capture and utilization of abundant solar energy have evolved into a hot research topic (Wu et al, 2021; Jiasheng 1996; Weinstein, Loomis, and Chen 2015)
Multiple absorption mechanisms in the quasi-optical microcavity (QOM) structure contribute to the low reflectance in the solar spectrum region, while the bottom ZrC leads to high infrared reflectance, which jointly determines the excellent selective absorption of the prepared CAA coating
The reflectance minimum at 0.62 μm is attributed to the destructive interference of the interfaces (Qiu et al, 2020)
Summary
To alleviate the increasingly severe fossil energy crisis, the capture and utilization of abundant solar energy have evolved into a hot research topic (Wu et al, 2021; Jiasheng 1996; Weinstein, Loomis, and Chen 2015). Compared with commercialized photovoltaic technologies, concentrated solar power (CSP) systems can overcome the problem of intermittent sunlight, but the high cost still hinders the large deployment (Yushchenko et al, 2018). The solar selective absorption coatings (SSACs), the core component of the CSP system, can substantially improve the solar to power conversion efficiency and enable the reduction of the levelized cost of energy (LCOE) of CSP systems (Kan et al, 2021) when the reliable operating temperature can reach or even exceed 750°C Materials ZrC target Al2O3 target SiO2 target Size Purity.
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