Spectrally selective solar absorber stable up to 900 °C for 120 h under ambient conditions

Abstract

Concentrated solar power (CSP) technology, which converts sunlight into heat and then electricity, is an attractive alternative to photovoltaics because of its high capacity for thermalenergy storage, which can be converted, to electricity after sunset. As the efficiency of this technology is limited by the Carnot efficiency, higher absorber temperatures are desirable. At high temperatures conversion efficiency is limited by heat loss from solar absorbers via radiation in infrared wavelengths. Hence, it is desirable to develop selective solar absorbers, which can absorb solar radiation while reflecting infrared radiation. It is also important to develop high temperature selective solar absorbers, which can work in ambient conditions to reduce cost as compared to those that work under vacuum. Here, we report a selective solar absorber made of black chrome/ITO/SiO2, deposited on stainless steel, which showed stable performance at 900°C under ambient conditions for 120 hours. The proposed selective solar absorber exhibits an absorptance of 0.9 in the solar spectrum with an infrared emittance of 0.4 beyond wavelengths of 6 µm.

Solution‐Processed All‐Ceramic Plasmonic Metamaterials for Efficient Solar–Thermal Conversion over 100–727 °C

“…[7,8] Despite the significant progress in demonstrating high-temperature SSAs based on different structures, [18] including cermets, [19][20][21] photonic crystals, [22][23][24] multilayered thin films, [25][26][27] and metamaterials, [28][29][30][31] many of them show inferior low-temperature performance compared with commercial SSAs due to insufficient selectivity. More importantly, similar to most low-temperature SSAs, these high-temperature SSAs are manufactured by sophisticated techniques like high-vacuum deposition, [19][20][21]25,27] and lithographic processes, [22][23][24]28,29,31] leading to high costs in large-scale productions. On the other hand, solution-based bottom-up approaches have driven revolutionary advances in the fabrication of large-area optoelectronic devices, [32][33][34] because of their advantages of low cost, high throughput, sufficient flexibility, and ease of use.…”

“…For instance, to improve the system efficiency and compete with fossil fuel‐fired plants, next‐generation CSP plants are expected to boost the operation temperature to above 650 °C. [ 7,8 ] Despite the significant progress in demonstrating high‐temperature SSAs based on different structures, [ 18 ] including cermets, [ 19–21 ] photonic crystals, [ 22–24 ] multilayered thin films, [ 25–27 ] and metamaterials, [ 28–31 ] many of them show inferior low‐temperature performance compared with commercial SSAs due to insufficient selectivity. More importantly, similar to most low‐temperature SSAs, these high‐temperature SSAs are manufactured by sophisticated techniques like high‐vacuum deposition, [ 19–21,25,27 ] and lithographic processes, [ 22–24,28,29,31 ] leading to high costs in large‐scale productions.…”

“…As given in Figure 4b,c, its calculated solar–thermal energy conversion efficiency η solar–th under 1‐sun illumination at 100 °C reaches 93%, which is slightly higher than commercial SSAs [ 15,16 ] and many previously reported SSAs fabricated by different methods. [ 14,19,20,22–29,31,35,36,45 ] When it is installed on high‐temperature parabolic trough collectors operating at 727 °C with a solar concentration ratio of 200, the SSA offers a theoretical η solar–th as high as 89% due to the competitive spectral selectivity ( ≈ 4.3, Figure 4d), exceeding that of the Pyromark‐2500 (71%), a widely used high‐temperature solar–thermal paint. [ 46 ] The performance is comparable to or even surpasses those of commercial and high‐temperature SSAs (Figure 4e and Table S1, Supporting Information).…”

High-Temperature Solar Thermal Energy Conversion Enhanced by Spectrally-Selective Metafilm Absorber under Concentrated Solar Irradiation

“…One of the most common coatings in high-temperature CSP systems is Pyromark 2500 [6], which loses a significant amount of heat through emission in the IR range due to the lack of high spectral selectivity in spite of high solar absorption and thermal stability at elevated temperatures [7]. Artificial composites or micro/nanostructured metamaterials have been recently developed as selective solar thermal absorbers [8][9][10][11][12][13][14] such as subwavelength gratings [15][16][17][18][19][20], nanocomposites [21] or nanoparticles [22], cermet [23][24][25], photonic crystals [26][27], and multilayers [28][29][30][31]. We recently reported the design and fabrication of an ultrathin multilayer selective solar absorber [30], namely metafilm absorber, which is thermally stable in air up to 600C, while thermal cycle testing revealed its long-term thermal stability at 400C in ambient conditions.…”

Microstructure and Thermal Stability of Cu/TixSiyN/AlSiN Solar Selective Absorbing Coating

“…The preparation of high-temperature coating is mostly made by magnetron sputtering, mainly using metal particles as the absorption units in metal-dielectric cermet coatings, such as Cu/TiNxOy/TiO2/Si3N4/SiO2 [15], Pt/AlxOy [16], AlyTi1−y(OxN1−x) [17], AlCrSiN/AlCrSiON/AlCrO [18], etc., which have excellent optical characteristics and thermal stability [19]. However, the use of oxygen to prepare oxide or nitrogen oxide coatings can cause the oil in the vacuum pump to oxidize [17,20], reducing its pumping speed and service life, and even affecting product quality and production efficiency [21]. To improve this issue, under current equipment conditions, we use nitrides of transition metals as an oxygen-free coating.…”