Investigation and Feasibility Analysis of Earth Tube Heat Exchangers (ETHE) for Sustainable Building Thermal Conditioning

With escalating global energy demands and rising ambient temperatures driven by climate change, active heating, ventilation, and air-conditioning (HVAC) systems constitute a massive fraction of primary electrical consumption and direct greenhouse gas emissions via high Global Warming Potential (GWP) chemical refrigerants (e.g., HFCs like R-32). This paper presents a comprehensive research study and engineering evaluation of Earth Tube Heat Exchangers (ETHE)—also known as Earth-Air Heat Exchangers (EAHE). ETHE systems exploit the substantial thermal inertia and passive geothermal storage capacity of the ground at depths of 2 to 4 meters, where soil temperatures remain quasi-steady across diurnal and seasonal cycles. This study systematically analyzes open-loop and closed-loop ETHE architectures, component selection (specifically PVC vs. metallic ducting and centrifugal air blowers), installation methodologies, key governing thermophysical parameters, and operational limitations. The findings establish that ETHE systems provide a highly viable, zero-refrigerant, and low-energy thermal pre-conditioning alternative capable of drastically lowering building carbon footprints across residential, institutional, and agricultural sectors.