Numerical and Analytical Study of a Novel Hybrid Earth to Air Heat Exchanger with Integrated Thermo-Electric Coolers for Arid Climates

Sustainable cooling solutions in hot, arid climates are essential to reduce high
energy consumption. Earth to Air Heat Exchanger (EAHE) offers a promising passive
cooling strategy, however, its standalone performance is often insufficient to meet
thermal comfort requirements. This thesis proposes and investigates a novel hybrid
cooling system that integrates the EAHE with a Thermoelectric Cooler (TEC) to
enhance cooling capacity, aiming to use the pre-cooled air from the EAHE to improve
the TEC’s efficiency.
To investigate this system, a comprehensive, transient numerical model was
developed in FORTRAN. The model is based on a Finite Volume Method (FVM) for
spatial discretization, an implicit Backward scheme for temporal discretization, and a
Newton-Raphson method to solve the resulting coupled, non-linear equations. The
model’s computational efficiency was optimized through a non-uniform mesh, and its
credibility was established through grid and time-step independence studies and
validation of the EAHE component against published experimental data.
Initial analysis of the EAHE-TEC Case Base (CB) demonstrates a significant,
short-term boost in cooling performance. However, this analysis also revealed a critical
performance flaw under continuous operation, which was that the rejected heat by the
TEC led to rapid thermal saturation of the surrounding soil, “Heat Trap”. This saturation
quickly diminished the system’s cooling power, eventually causing it to perform worse
than a standalone EAHE. By building on this finding, the system was enhanced by
modifying its configuration and operational schedule, which led to substantial cooling
capacity, though for a shorter duration.
This thesis therefore provides a numerical tool for modelling, with its EAHE
component validated, and an enhanced operational strategy for operating the hybrid
EAHE-TEC system to improve cooling performance during peak thermal loads in arid
climates, such as Saudi Arabia.