THERMAL PERFORMANCE ANALYSIS OF A SOLAR-ASSISTED HELICAL STEEL PILE THERMO-ACTIVE FOUNDATION WITH A DOUBLE U-LOOP HEAT EXCHANGER IN A COLD CLIMATE

With the growing need to increase the share of renewable energy in the energy mix and limit the emission of greenhouse gases, ground source heat pumps (GSHPs) are emerging as an alternative option for space heating. They are the most efficient technology for space heating and cooling available today. However, with the high upfront costs, mainly due to the drilling and installation of ground heat exchangers (GHEs), some homeowners have decided against the use of these systems despite the low operating costs. To offset some of the drilling cost, a new option is to install the heat exchanger within the steel structural piles used in the new construction of homes, thus creating a “thermo-active foundation” for the building. The pile can also be used as an in-ground helical steel GHE in the case of existing buildings. With this relatively new area of research, only a limited number of configurations of the heat exchanger have been explored. This work explores the potential of a double u-loop GHE configuration coupled with a solar thermal collector to further enhance efficiency and long-term performance in a cold climate. The solution was implemented using a finite volume-based computational fluid dynamics tool considering realistic building loads, soil thermal properties, and climatic data for Minnesota’s cold climate. The developed model was thoroughly validated with other experimental work using actual temperature and weather data, ensuring its accuracy. Additionally, the influence of several parameters on the heat pump’s coefficient of performance was investigated. Results show that coupling the foundation heat exchanger with solar thermal increases the annual COP from 3.60 to 3.90 and 4.15 for the base case, 2 m² solar 1 case, and 3.8 m² solar 2 case respectively.