Nanofluids stability in flat-plate solar collectors: A review

• Published in: Solar energy materials and solar cells 2024-07, Vol.271, p.112832, Article 112832
• Main Authors: García-Rincón, M.A., Flores-Prieto, J.J.
• Format: Article
• Language: English
• Subjects: Flat plate solar collectors; Nanofluids; Nanofluids advances; Nanoparticle dispersion advances in flat-plate solar collectors; Nanoparticle stability; Nanoparticles; Review; Solar heating
• ISSN: 0927-0248; 1879-3398
• DOI: 10.1016/j.solmat.2024.112832

The nanofluids enhance the thermal performance of FPSC concerning conventional working fluids, improving their thermophysical properties to transfer heat. Nanofluid stability affects the long-term of FPSC's performance, and it plays a leading role in the certainty of successful projects. Most of the literature attends to the FPSC's performance over short periods versus expectations of 20–30 years. This review focusses on the thermal efficiency stability of solar water-nanofluid heaters by identifying the most common parameters and methods, as well as the nanoparticle characteristics effects, surfactant usage and fouling on the nanofluid lifetime in FPSC. Nanofluids improve thermal efficiency by 5–35% concerning conventional working fluids, reaching up to 0.85. Z-potential is an indicator to establish particle dispersion degree, which means, at the same time, the nanofluid usage time. The stability was improved by surfactant, preparation method, or nanoparticle content (0.2–0.3% volume base). Nanofluid fouling is common and significantly affects the thermal conductivity (≥11%). The widespread application of nanofluids waits for better nanoparticle dispersion over major’ usage time, and stability improves at higher temperatures (>90°C). When nanoparticle instability increases as working time goes by, its viscosity, friction forces and pressure drop also increase, so the pumping power requirement rises. In FPSC, the stability reports reach up to 2.5% of the heater's lifetime. However, stability reports reach up to 2.5% of the heater's lifetime. They must be increased by considering the most common parameters like Z-potential, preparation methods, nanoparticle characteristics, surfactant usage, and fouling to improve the certainty of successful nanofluids FPSC projects. •Nanofluids stability provides certainty for solar water heating successful projects.•Stability of efficiency drift review of nanofluids in SWH over typical lifetime.•Nanofluids improve efficiency by 5–35% to preparation and running time.•Nanofluids stability studies in SWH reach up 2.5% of its lifetime until today.•Z-potential drift over the lifetime of SWH can represent its nanofluid stability.