Long-term performance of heat exchanger piles

Heat exchanger piles utilize the constant temperature and the thermal storage capacity of the ground for heating and cooling of buildings. Sustainable use of the ground as a renewable energy source depends on the seasonal energy load balance. One of the critical factors for the sustainable operation of heat exchanger piles is that a constant temperature of the ground is maintained over seasons. The entire soil mass can be gradually heated up or cooled down if the energy demand is unbalanced. This paper presents the findings on the long-term performance of heat exchanger piles and their efficiency for areas where the demand is nonsymmetrical. Analyses have been performed to investigate the long-term performance of several pile arrangements ranging from single pile to numerous pile groups with a selection of 2 x 2, 3 x 3, 4 x 4 and 5 x 5 rectangular grids. The thermo-mechanical behavior of the single pile was also investigated. The analyses simulated 30 years of pile operation and resulted in significant findings for long-term performance of heat exchanger piles under different climatic conditions.