Long-term numerical assessment of shallow geothermal systems in arid regions along the Nile River

The sustainable operation of renewable energy systems ensures long-term reliability and competitiveness. While geothermal energy is promising, its performance in cooling-dominated hot climate remains underexplored. High cooling demand in such regions leads to intensive heat injection, making the system’s recovery of its initial thermal state critical for sustainability. This study presents a numerical simulation of a ground source heat pump (GSHP) established in Cairo, Egypt, for the first time, near the Nile River, coupled with three 40.00 m borehole heat exchangers (BHEs), modeled using the numerical software FEFLOW®. The model was calibrated with field measurements and thermal response tests; then, it was used to evaluate the system’s ten-year performance under different operating scenarios, including parallel and series flow and integration of domestic hot water (DHW) production. Results showed that series flow reduced maximum borehole outlet temperature by up to 5.69% compared to parallel flow and limited thermal plumes to shallower depths. Parallel flow caused gradual ground temperature rise and broader plume expansion, while DHW integration further improved thermal balance, reducing peak temperatures by ~3.24% and mitigating long-term heat accumulation. Observation borehole data confirmed that series flow promotes ground thermal recovery, whereas parallel flow leads to progressive imbalance (ground warming). Overall, findings demonstrate that shallow geothermal systems are technically viable in Cairo’s hot arid climate, where series flow combined with DHW recovery proved to enhance the longterm thermal sustainability. Agreement between numerical predictions and field data confirms model reliability, providing guidance for GSHP design and performance in hot arid regions.