Numerical Analysis of Seasonal Heat Storage Systems of Alternative Geothermal Energy Pile Foundations

Abstract

Geothermal energy pile foundations are sustainable, cost-effective alternative energy systems for heating and cooling needs of buildings. This paper presents the thermal modeling of two different configurations of energy pile foundations used for seasonal energy storage. Several two-dimensional (2D) transient analyses were carried out to find the optimum pile configuration and to obtain preliminary information about the heat exchange between the ground and the building. Two scenarios were modeled. In Scenario 1, a combination of long and short piles was simulated, while in Scenario 2 only long piles were considered. Long piles are structural piles and work as a heat exchanger throughout the year, while the nonstructural short piles operate only in the summer months to inject surplus solar energy into the ground. Simulation results show that in Scenario 1 the vertical temperature distribution was uneven, resulted in high temperatures at shallow depths (0–10 m) and near-freezing temperatures at greater depths. In contrast, Scenario 2 yielded a more uniform temperature distribution throughout the depth. More importantly, in Scenario 2, the temperature inside the storage system was maintained well above the freezing temperature.