A Hybrid Earth–Air Heat Exchanger with a Subsurface Water Tank: Experimental Validation in a Hot–Arid Climate

Safieddine Ounis (), Okba Boucherit, Abdelhafid Moummi, Tallal Abdel Karim Bouzir, Djihed Berkouk (), Fabrizio Leonforte, Claudio Del Pero and Mohammed M. Gomaa
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Safieddine Ounis: Department of Architecture, University Mohamed Khider of Biskra, BP 145 RP, Biskra 07000, Algeria
Okba Boucherit: Department of Mechanics, University Mohamed Khider of Biskra, BP 145 RP, Biskra 07000, Algeria
Abdelhafid Moummi: LARGHYDE Laboratory, Faculty of Architecture, Urbanism, Civil Engineering and Hydraulics, University Mohamed Khider of Biskra, BP 145 RP, Biskra 07000, Algeria
Tallal Abdel Karim Bouzir: Department of Architecture, University Mohamed Khider of Biskra, BP 145 RP, Biskra 07000, Algeria
Djihed Berkouk: Department of Architecture, University Mohamed Khider of Biskra, BP 145 RP, Biskra 07000, Algeria
Fabrizio Leonforte: Department of Architecture, Built Environment and Construction Engineering, Politecnico di Milano, 20133 Milano, Italy
Claudio Del Pero: Department of Architecture, Built Environment and Construction Engineering, Politecnico di Milano, 20133 Milano, Italy
Mohammed M. Gomaa: Department of Architecture, Dar Al-Hekma University, Jeddah 22246, Saudi Arabia

Sustainability, 2025, vol. 17, issue 22, 1-20

Abstract: Earth–Air Heat Exchangers (EAHEs) exploit stable subsurface temperatures to pre-condition supply air. To address limitations of conventional systems in hot–arid climates, this study investigates the performance of a hybrid EAHE prototype combining a serpentine subsurface pipe with a buried water tank. Installed in a residential building in Lichana, Biskra (Algeria), the system was designed to enhance land compactness, thermal stability, and soil–water heat harvesting. Experimental monitoring was conducted across 13 intervals strategically spanning seasonal transitions and extremes and was complemented by calibrated numerical simulations. From over 30,000 data points, outlet trajectories, thermal efficiency, Coefficient of Performance (COP), and energy savings were assessed against a straight-pipe baseline. Results showed that the hybrid EAHE delivered smoother outlet profiles under moderate gradients while the baseline achieved larger instantaneous ΔT. Thermal efficiencies exceeded 90% during high-gradient episodes and averaged above 70% annually. COP values scaled with the inlet–soil gradient, ranging from 1.5 to 4.0. Cumulative recovered energy reached 80.6 kWh (3.92 kWh/day), while the heat pump electricity referred to a temperature-dependent ASHP totaled 34.59 kWh (1.40 kWh/day). Accounting for the EAHE fan yields a net saving of 25.46 kWh across the campaign, only one interval (5) was net-negative, underscoring the value of bypass/fan shut-off under weak gradients. Overall, the hybrid EAHE emerges as a footprint-efficient option for arid housing, provided operation is dynamically controlled. Future work will focus on controlling logic and soil–moisture interactions to maximize net performance.

Keywords: Earth–Air Heat Exchanger (EAHE); hybrid cooling systems; hot-arid climate adaptation; underground water tank; thermal performance; energy savings (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2025
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