Geothermal cooling potential for cities: A case study in Cairo

Despite the limited number of experimental studies on geothermal cooling in hot climates, this work presents a series of performance evaluations of a ground source heat pump (GSHP) system designed for predominant cooling in Egypt's arid environment. The unbalanced thermal loads and continuous heat injection into the ground pose a challenge for the system sustainability. The GSHP was built at Cairo University - Faculty of Engineering within the GEB project, and it has been in monitored operation since Summer 2024. Equipped with adjustable valves, the system allows for flexible configuration of borehole heat exchangers (BHE) to optimize performance. Borehole inlet and outlet water temperatures were recorded at the top of each BHE under different flow arrangements, including parallel and series paths. The study experimentally assessed the efficiency impacts of single-U versus double-U BHEs, Series versus parallel flow, and examined the role of Domestic Hot Water (DHW) integration. All operating scenarios were tested across multiple flow rate levels. Results demonstrated higher geothermal cooling and heating applicability in hot climates, with improved performance observed under specific configurations. Specifically, series flow arrangements achieved up to a 4.47% reduction in borehole outlet temperature, while the integration of DHW led to a 7.16% decrease in borehole outlet temperature reducing the thermal stress on the aquifer in summer. Finally, the enhancement of heat dissipation and ground thermal recovery was further linked to the accurate estimation of local hydrological properties.