Geothermal–Passive Hybrid Cooling via Courtyard-Integrated EAHE: A CFD-Based Framework for Low-Energy Residential Construction in Hot, Arid Areas

Due to severe cooling requirements and a lack of passive-geothermal system integration in residential design, achieving low-energy buildings in hot, dry climates continues to be a significant issue. Although Earth-Air Heat Exchangers (EAHEs) have shown encouraging cooling potential, there hasn't been enough research done on how to incorporate them into climate-responsive building typologies, especially courtyard housing. By incorporating an under-courtyard EAHE system into a low-energy residential building in Baghdad, Iraq, this study suggests a novel geothermal–passive hybrid cooling framework. The method improves passive cooling efficacy by combining courtyard-induced microclimatic management with subsurface thermal stability. Using ANSYS Fluent, a high-resolution Computational Fluid Dynamics (CFD) model was created to assess system performance under harsh summer circumstances (ambient temperature up to 47 °C). Important design factors were methodically optimised, such as pipe length, airflow velocity, diameter, and burial depth. The suggested system may lower the incoming air temperature to 23–28 °C, according to the results, with a maximum cooling potential that surpasses 21 °C during peak conditions. The ideal setup shows a balanced performance between thermal efficiency and pressure losses (3 m burial depth, 0.20 m pipe diameter, 60 m pipe length, and airflow velocity of 1–5 m/s). A transferable design framework for incorporating EAHE systems into courtyard-based residential architecture is presented in the study, emphasising its potential to drastically lower cooling energy use and facilitate the construction of low-energy homes in hot, dry areas. The results help close the gap between climate-responsive architecture design and geothermal technical solutions.