Study Of Control Strategies For Hybrid Ground Source Heat Pump System In Hot Summer And Cool Winter Area

GSHP (Ground Source Heat Pump) system, which utilize shallow geothermal energy resources to provide air conditioning, heating and hot water supply to building, is one of the most significant technology of renewable energy construction. District of hot summer and cold winter has a long cooling period, stable performance of units can be achieved while using hybrid ground source heat pump (HGSHP) system with cooling tower to reduce heat rejection to soil. However, hybrid ground source heat pump system has a higher initial investment, how to take reasonable control scheme of cooling tower to reduce system energy consumption and keep soil heat balance is a key issue currently facing.In this paper, research was carried on the operation performance and soil heat transfer characteristics of the HGSHP system for the district of hot summer and cold winter by the transient system simulation program (TRNSYS). Hybrid ground source heat pump system designation and modeling were accomplished after soil thermal parameters were obtained from on-site thermal response test experiment. Three cooling tower start-stop control schemes were proposed, different parameters were set up for each scheme in order to get the optimal sub program and the applicability of each scheme in Changsha was compared. The same research was carried out in Shanghai and Wuhan where also have a hot summer and cold winter climate using the same building and cooling tower control scheme, the optimal scheme was obtained through comparison. Finally, characteristic and adaptability of the three control schemes were summarized based on analysis of regional differences.Control signal of the hybrid system control scheme including outlet pipe water temperature, temperature difference between outlet pipe water and ambient as well as the running time. In order to ensure the normal operation of the hybrid system, the refinement of setting parameters is needed, and combination of each control scheme should be considered. In addition, specific indicator to evaluate soil thermal balance is presented in this paper as one of the selection criteria of the optimal control scheme. The results show that, outlet pipe water temperature control scheme can significantly reduce soil heat accumulation, but the energy consumption is relatively higher. Temperature difference control scheme react sensitively and have low energy consumption, but the results varying between different regions. Running time control scheme dependent less on the control signal settings and the system is more stable while use it. Soil thermal balance can achieve use each control scheme. Running time control scheme is more applicable in Changsha and Wuhan, Shanghai is even more suitable to take temperature control.