Energy-saving Analysis of a Hybrid Ground-coupled Heat Pump Project

Hybrid ground-coupled heat pump (HGCHP) uses a supplemental heat rejecter to dissipate extra thermal energy to guarantee underground soil heat balance. In this paper, a HGCHP project in Nanjing of China was chosen to analysis the energy-saving properties in terms of the control strategies, the building envelope and the terminal air-conditioning system. This HGCHP system utilized a cooling tower (CT) and the borehole heat exchanger (BHE) to dissipate the sum heat flow in cooling season. The software EnergyPlus was employed to simulate the project and design the heat flow of CT and BHE. Then two feasible control strategies for the BHE and CT were proposed in this paper. The energy-saving potential of the building envelope was analyzed in terms of the surface color of the wall/roof. With the same terminal system, it was found that in cooling season the heat flow of the insulated building with black wall/roof is 1.2 times more than that with white. With the same insulated building and same gray wall/roof, it was concluded that the heat pumps units for primary air fan-coil system shows an annual energy consumption increase of 4.47x10(7) [kJ] comparing to radiant floor system.