Investigation of the thermal response of an energy raft foundation in Taipei

This study investigates the thermal response of an energy raft foundation in Taipei. The energy raft foundation was installed to provide heating and cooling to a 13-story and 3-level basement residential building. The geothermal pipe comprised 40 loops connected in series and had a total heat exchange length of 6720 m. A three-dimensional numerical model was established and validated against field measurements. The thermal response of the energy raft foundation, including soil and geothermal pipe temperature distributions, was investigated. A series of parametric studies was conducted to evaluate the effects of the geothermal pipe spacing and pattern on the heat exchange efficiency. The results from numerical simulations indicated that the pipe outlet fluid temperature varied during the daily operation cycle. The maximum and minimum temperature differences between the inlet and outlet fluid temperatures were 7 and 4 °C, occurring at the beginning and the end of daily operations, respectively. The horizontal range of influence of the geothermal pipe on the soil temperature was small at approximately 1.6 times the width of the pipe loop, suggesting that the geothermal pipe would have little effect on the soil temperature in an adjacent building’s foundation. The pipe spacing and pattern strongly influenced the heat exchange efficiency. For the snake and swirl patterns with separate high- and low-temperature pipes, the pipe outlet fluid temperature was lowest for a pipe spacing of S = 0.1 m. For the meander and loop patterns, the influence of adjacent pipes resulted in a higher outlet fluid temperature at S = 0.1 m than at S = 1.0 m. On the basis of this study’s findings, the optimal pipe configuration is discussed.