Performance evaluation of evacuated tube solar collector using Al₂O₃/water nanofluid: Experiment, modelling, life cycle and cost analysis in the UAE context

This study investigates the performance improvement of an evacuated tube solar collector (ETSC) using Al₂O₃/water nanofluids, focusing on energy, exergy, and economic aspects. The thermophysical properties of Al₂O₃/water nanofluids, including density, specific heat capacity, and thermal conductivity, were experimentally determined, with stability validated through zeta potential analysis. Two volume fractions (0.05% and 0.3%) were tested at flow rates of 1, 2, and 3 LPM under varying solar irradiance. The nanofluids significantly improved thermal performance, with the highest thermal and exergy efficiencies of 68% and 30.76%, respectively, achieved using 0.05% Al₂O₃/water nanofluid at 3 LPM. A comparison is also conducted between the proposed system and previously published literature using TiO₂/H₂O nanofluid. Results suggest that Al₂O₃/H₂O nanofluids demonstrated 5.32% greater thermal efficiency as well as weight and cost reduction of about 85.5% and 69.15%, respectively at a lower volume fraction over TiO₂/H₂O nanofluid. A life cycle analysis, including energy requirement, CO₂ emissions, and 20-year investment, is conducted to assess the system's environmental and economic feasibility. Life cycle analysis revealed a significant reduction in CO₂ emissions and total costs for the solar-powered system. Furthermore, predictive modeling using CatBoost and AdaBoost achieved high accuracy, with CatBoost emerging as the superior model for generalization and prognostic efficiency. This work underscores the potential of Al₂O₃/water nanofluids for sustainable and cost-effective solar thermal applications.