Comparative performance analysis of low-enthalpy geothermal energy in arid and semi-arid climates

This study utilizes a model to investigate the thermal performance and determine the optimal design parameters for the low-enthalpy geothermal energy system earth-air heat exchanger in two climatically distinct regions: the arid, high-extreme environment of the Upper Egypt region and the milder conditions of the Egyptian Mediterranean region. First, a parametric analysis was conducted, focusing on the influence of pipe length, installation depth, air velocity, and pipe diameter, using Typical Meteorological Year data. The analysis identifies an optimal design configuration, recommending a pipe length of 40-50 m, an air velocity of 2 m/s, and a practical installation depth of 3-5 m to maximize heat exchange efficiency without incurring unnecessary costs. Using optimal design conditions, performance comparison reveals that earth-air heat exchanger effectiveness is directly proportional to the magnitude of the ambient-to-soil temperature difference. At peak hours, the temperature drop in the Aswan arid region was found to be 45% higher than in the Alexandria semi-arid region, highlighting the system's enhanced effectiveness in arid environments. Furthermore, the earth-air heat exchanger demonstrates year-round potential by providing effective heating during winter months when the soil is warmer than the ambient air at both regions. It is demonstrated that the low-enthalpy geothermal system hold a higher energy-saving potential in arid regions with extreme temperature conditions.