Geothermal Energy for Efficient Cooling of Intake Air in Harsh Environments: A Combined Experimental-Modelling Approach

In this work we present a novel approach to enhance energy efficiency in cooling intake air for air conditioning (AC) systems in harsh environments using geothermal energy. We developed a 3D finite element model to simulate the heat transfer between underground soils/gravels and cooling pipes, which effectively precools intake air before it enters the AC system. To validate the model, we installed sensors at various depths ranging from 1 meter below ground to 10 meters. These sensors enabled us to accurately measure the underground temperature profiles. Based on the measured temperature data, we constructed a geothermal model that captures the behavior of the underground thermal environment. The model was built using COMSOL Multiphysics software, version 5.3, and utilized the Heat Transfer Module and the Time Dependent solver. A physics-controlled mesh was employed with an average element quality of 0.78. The model was tested with data of August-2022, a month characterized by extreme temperatures exceeding 50°C in the ambient air. Remarkably, the underground temperature at a depth of 10 meters remained almost constant about 30°C throughout the year. These findings illustrate the significant potential of the underground temperature for precooling applications. By introducing water into the cooling pipes, we could efficiently exchange cooled water with the intake air of the AC system. This approach maintained a stable intake air temperature of 30°C for up to 4 days using the same circulated water. However, to avoid the cumulative effects of cooling and prevent a reverse temperature increase, the circulating water had to be replaced every 5 days. Alternatively, the model revealed that by introducing air into the cooling pipes and directly utilizing it as intake air, we could shave the ambient air temperature up to 10°C but only for a single day which can save up to 50% of AC energy consumption. Consequently, to prevent the reverse temperature increase and cumulative heat, the air needed to be replaced daily. Introducing water as a coolant instead of air was significantly more effective due to its relatively higher sensible heat. The outcomes of our study demonstrate the feasibility and effectiveness of utilizing geothermal energy as an energy-efficient solution for cooling intake air in AC systems operating in harsh environments. The findings provide valuable insights for optimizing the design and operation of geothermal cooling systems, offering significant potential for energy savings and environmental sustainability.