Abstract <p>Solar stills are simple and environmentally friendly devices for small-scale freshwater production, but their productivity and energy efficiency are often limited. This study aims to evaluate the combined influence of internal reflectors and aluminum oxide (Al₂O₃) nanofluid on the energy, exergy and economic performance of a single-slope solar still. A transient numerical model is developed for a conventional single-slope solar still and three modified configurations: with Al₂O₃ nanofluid, with internal reflectors, and with both modifications. The model solves the coupled energy balance equations for the basin liner, saline water and glass cover, and incorporates standard correlations for convective, evaporative and radiative heat transfer. Nanofluid properties are evaluated for an Al₂O₃. Exergy transfer and exergy destruction are calculated for each component. Simulations are carried out for a typical day in March under Dhahran climatic conditions, and the model is validated against published experimental data. The combined configuration with internal reflectors and Al₂O₃ nanofluid achieves the highest daily water productivity (4.258 L/m² day) and daily energy efficiency (52.3%), compared with 2.758 L/m² day and 33.9% for the conventional still. The basin liner is identified as the dominant site of exergy destruction. A preliminary economic assessment indicates shorter payback time for the enhanced configurations. Internal reflectors provide the largest performance gains by increasing incident solar energy, while Al₂O₃ nanofluid offers additional improvement by enhancing internal heat transfer. Their combination yields the best overall energy, exergy and economic performance, and highlights the importance of integrated optical and thermal enhancements in solar still design.</p>