Development of a Multi-Objective optimization framework for Earth-to-Air heat Exchanger Systems: Enhancing thermal performance and economic viability in Moroccan climates

In this study, a multi-objective optimization framework is developed to provide a comprehensive approach to designing efficient and cost-effective Earth-to-Air Heat Exchanger systems (EAHE). By integrating sensitivity analysis, design of experiments, genetic algorithms, and multi-criteria decision-making, the framework addresses the complexities of balancing thermal performance and economic viability. Through an experimentally validated model of the exchanger, the study conducts sensitivity analyses to identify key design parameters and uses a fine-tuned genetic algorithm for optimization. The optimization focuses on minimizing the life cycle cost (LCC) and maximizing the cooling potential across three distinct Moroccan climates. Furthermore, multi-criteria decision-making methods were employed to determine an optimal solution from the multi-objective optimization results. Results indicate that the optimal exchanger configurations vary with location, highlighting the importance of site-specific design. For instance, the optimal design selected for Marrakech and Oujda is a pipe of 160 mm of diameter with 49 m of length and buried at 3 m, while for Errachidia it is a 160 mm pipe with 47 m of length and buried at 4 m since the location has a higher gradient of ground temperature. The EAHE gave a cooling potential of 1447 kWh/year, 1172 kWh/year and 1739 kWh/year with a LCC of 4122$, 4091$ and 4073$ over 50 years for Marrakech, Oujda and Errachidia, respectively. The normalized life cycle cost (NLCC) is the lowest for Errachidia (0.234$/kWh), followed by Marrakech (0.285$/kWh) then Oujda (0.349$/kWh).