Integrating atmospheric water harvesters with solar chimneys and earth-to-air heat exchangers: a performance study in the climate of Basra, Iraq

ABSTRACT

Iraq's rapid demographic growth, coupled with climate change and its particular topography, has heightened the severity of water shortages over the past decade. Freshwater reserves are dwindling faster due to increased usage, ecological decline, and global warming. To address this, the present study evaluates an integrated setup incorporating a solar chimney (SC), an earth-to-air heat exchanger (EAHE), and an atmospheric water harvester (AWH) designed to simultaneously offer passive cooling and generate distilled water in hot environments. The proposed system absorbs moisture at night using the AWH and evaporates it into distilled water during the day using solar energy. Additionally, at night, the dried air from the AWH can be transferred to the EAHE-SC section to help control the humidity of the heating, ventilation, and air conditioning system. During the day, the AWH and EAHE-SC systems operate independently of each other and can be disconnected by an axial valve. By using OpenFOAM with a scalar moisture transport model, we assess the annual performance for Basra, Iraq, and show that the proposed approach can be applied to enclosed spaces to deliver two main outputs. The analysis confirms that buoyancy-driven flow, boosted by the EAHE's cooling, is optimal under warm conditions, whereas winter operation would require configuration adjustments. Overall, the integrated system offers a sustainable approach to enhancing indoor comfort and providing an additional water source in hot, arid regions. Results indicate effective passive cooling from May to August, keeping indoor temperatures between 18.3 and 21.4 °C – well below peak outdoor levels and typical tropical comfort ranges – driven by indoor air velocities of 0.18–0.21 m/s and a stable relative humidity of 39.5–42%, with a natural ventilation rate of 5–6 air changes per hour (ACH). The AWH subsystem yields distilled water, achieving a peak daily rate of 485 g/h in July and monthly totals exceeding 180 kg.