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Ground source heat pump systems offer efficient and sustainable heating and cooling solutions; however, traditional vertical boreholes involve high capital costs associated with drilling, hindering widespread adoption. Recent research introduces a novel approach by integrating geothermal heat exchangers into steel helical piles within building foundations, known as "Geo-Piles." These devices, extending typically 50 ft to 100 ft into the ground, serve a dual purpose (structural and thermal) and show promise as cost-effective alternatives. Further advancements explore the use of plastic as a casing material, for thermal-only systems, enhancing affordability and enabling standalone system deployment without relying on extensive new construction projects. This paper investigates plastic geo-exchange pipes (PGEPs), designed similarly to Geo-Piles, aiming to reduce costs by implementing a horizontal installation method at depths comparable to other forms of linear utility infrastructure. Numerical modeling was employed to assess the system's performance at three depths—15 ft, 18 ft, and 21 ft and was then compared to a vertical configuration. The results indicate that with every additional 3 feet of depth in the horizontal configuration, there is an enhancement in capacity of 0.5 tons for every 200 feet of PGEP. Moreover, the 18-ft configuration exhibits exceptional thermal performance while simultaneously reducing installation space and potentially meeting permit requirements, showcasing its potential as an economical and efficient solution in the realm of ground source heat pump systems.
Ghalayini et al. (Tue,) studied this question.