Assessment of Energy Recovery Potential in Urban Underground Utility Tunnels: A Case Study

• Published in: Buildings (Basel) 2024-10, Vol.14 (10), p.3113
• Main Authors: Wei, Tong, Fan, Mingyue, Xu, Zijun, Li, Weijun, Gu, Zhaolin, Luo, Xilian
• Format: Article
• Language: English
• Subjects: Air temperature; Analysis; Architecture and energy conservation; building energy efficiency; Case studies; CFD; China; Computational fluid dynamics; Cooling; Design factors; Emissions; Energy conservation; Energy consumption; Energy recovery; Enthalpy; Field tests; Fluid dynamics; Geothermal energy; Geothermal power; Heat exchange; heat exchange efficiency; Heat recovery systems; Heat transfer; Humidity; Hydrodynamics; Industrial plant emissions; Money; Roads & highways; Sensors; shallow geothermal energy; Summer; Temperature; Temperature gradients; Tunnels; underground tunnel ventilation; Underground utilities; Ventilation
• ISSN: 2075-5309; 2075-5309
• DOI: 10.3390/buildings14103113

Underground spaces contain abundant geothermal energy, which can be recovered for building ventilation, reducing energy consumption. However, current research lacks a comprehensive quantitative assessment of its energy recovery. This research evaluates the energy recovery potential of the Xingfu Forest Belt Urban Underground Utility Tunnels. Field experiments revealed a 7 °C temperature difference in winter and a 2.5 °C reduction during the summer-to-autumn transition. A computational fluid dynamics (CFD) model was developed to assess the impact of design and operational factors such as air exchange rates on outlet temperatures and heat exchange efficiency. The results indicate that at an air change rate of 0.5 h−1, the tunnel outlet temperature dropped by 10.5 °C. A 200 m tunnel transferred 8.7 × 1010 J of heat over 30 days, and a 6 m × 6 m cross-sectional area achieved 1.1 × 1011 J of total heat transfer. Increasing the air exchange rate and cross-sectional area reduces the inlet–outlet temperature difference while enhancing heat transfer capacity. However, the optimal buried depth should not exceed 8 m due to cost and safety considerations. This study demonstrates the potential of shallow geothermal energy as an eco-friendly and efficient solution for enhancing building ventilation systems.