Control Strategy Study Of Hybrid Ground-source Heat Pump System

Ground source heat pump (GSHP) system is becoming more and more popular dueto its high efficiency and environmental friendliness. For the buildings which the coolingload is much larger than the heating load, the ground temperature would increase due tothe heat which the system rejects. The ground source heat pump should be operated withsupplemental heat rejecter, such as cooling tower, this kind of system is called hybridground source heat pump (HGSHP) systems. Appropriate control strategies of hybridground source heat pump systems would not only keep ground heat balance well but alsosave the operation cost. This paper presents five control strategies for a hybridground-source heat pump system in Zhengzhou and the operation and energyconsumption of the system were dynamically simulated.Physical models of cooling tower, chilling unit, water pump, manifold and groundheat exchanger were built and analysed in detail. A design method based on TRNSYS ofground heat exchanger. The thermal performance of different boreholes were dynamicsimulated, the borehole number was determined and the HGSHP system starts in summerfor avoiding low water temperature in ground heat exchanger appear in winter. Asimulation platform is built for the HGSHP system, and five control strategies weresimulated respectively, for this system, results show that under wet-bulbtemperature-based control strategy with reasonable temperature set-point, the ground heatbalance could be kept wellA control strategy called “Heat balance measure&wet-bulb temperature” was alsosimulated under changing annual load.On this strategy, A function between heat balancerate and wet-bulb temperature set-point was built based on different annual load. This function was designed to determine the wet-bulb temperature set-point of the system nextyear. The result shows that use the function only could not keep heat balance. In actualoperation, the changing annual load should be considerd.