Investigation on stable TiN plasmonic nanofluids for applications in direct absorption solar collectors

Abstract TiN nanoparticles based plasmonic nanofluids exhibit promising results in performance improvement of direct absorption solar collectors, but the main issue for practical application is their poor stability. In this work, ethylene glycol (EG) based TiN nanofluids with polyacrylic acid (PAA) stabilizing ligand were prepared. The optical properties of the TiN‐PAA/EG nanofluids with concentration ranging from 10 to 100 mg/L were characterized. The solar weighted absorption fraction of 99.55% is achieved at the optical depth of 1 cm when the concentration of the TiN‐PAA/EG nanofluids is 100 mg/L. In addition, the experimental results of the long‐term stability indicated that the TiN‐PAA/EG nanofluid retained excellent dispersion stability after ambient storage of 250 days. Then, the stability of TiN‐PAA/EG nanofluids upon prolonged heating cycle and accelerated ultraviolet (UV) irradiation was investigated. The results showed that TiN‐PAA/EG nanofluid with concentration of 75 mg/L presents superior thermal stability after prolonged heating cycles at 120°C and excellent photostability after 30 days of UV irradiation. Finally, the photo‐thermal conversion performance for TiN‐PAA/EG nanofluids was studied. The stagnation temperature of the 100 mg/L TiN‐PAA/EG nanofluids after light irradiation of 2 h reaches up to 80.12°C. The specific absorption rate of the prepared TiN‐PAA nanofluids is demonstrated higher than that of reported TiN nanofluids.