In Situ Oxidizing Commercial Alloy to Achieve Selective Solar Absorption with High-Temperature Stability

A solar selective absorber (SSA) with high solar absorptance and low thermal emittance is significant for solar-thermal applications to improve their solar-thermal conversion efficiencies. Developing high-temperature stable and easily manufactured SSAs is critical in next-generation solar power systems. In this work, a simple and general method by in situ oxidizing a commercial alloy was proposed to prepare high-temperature stable SSAs, which can be used on various commercial alloy materials (such as stainless steel and W-Cu alloy) and complex geometry structures to adapt to different solar-thermal applications. Further analysis showed that the selective spectrum was achieved by the high absorptance of metal oxide in the solar band and the low emittance of alloy substrates in the mid-infrared band. Taking the stainless steel 304 as an example, the average solar absorptance (alpha(solar)) and thermal emittance (epsilon(IR)) can reach 0.848/0.171 after oxidizing at 900 degrees C for 2 h or 0.824/0.098 after oxidizing at 800 degrees C for 2 h. Meanwhile, the SSAs can operate stably for more than 144 h in air at 600 degrees C due to the high-temperature generation of Cr2O3. These results indicate that in situ oxidizing commercial alloys can be a simple, low-cost, and scalable manufacturing strategy to prepare high-temperature stable SSAs in various solar-thermal applications.