| Title | Long-term Operation Management of a Hybrid Ground Source Heat Pump System Combined with a Cooling Tower by Using an Autonomic Optimum Control System in Cooling-dominant Region |
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| Authors | Takao KATSURA, Yasushi NAKAMURA, Yoshitaka SAKATA, Katsunori NAGANO |
| Year | 2020 |
| Conference | World Geothermal Congress |
| Keywords | Hybrid ground source heat pump system, long-term operation management, autonomic optimum control system |
| Abstract | Ground source heat pump (GSHP) systems have advantages at the point view of thermal energy efficiency compared to the conventional heat source systems such as air source heat pump systems. However, there is possibility of long-term ground temperature rise or decrease due to excess heat injection or injection particularly in the case of large scale GSHP systems. Therefore, it is important to establish the optimum operation method of the hybrid GSHP (HGSHP) system combined the cooling tower, solar collector, etc. In this paper, the authors demonstrate the long-term operation management of a HGSHP system combined with a cooling tower by using an autonomic optimum control system in cooling-dominant region. The autonomic optimum control system consists of the programable logic controller (PLC), monitoring equipment, and software in server. The monitoring data such as the temperature and the flow rate obtained by the PLC and monitoring equipment is transmitted to software. The software simulates the HGSHP system operation by using the monitoring data and predicts the temperature variation of heat carrier fluid. Then, the temperature of heat carrier fluid in which the cooling tower is operated is determined and transmitted to the PLC. The PLC control the cooling tower basis on the temperature. The analysis of first year’s operation of the HGSHP system indicated that the heat injection rate during cooling season was approximately three times compared to the heat extraction rate during heating season. The apparent effective thermal conductivity was estimated as 3.7 W/(m‧K) and it is expected that this high value was caused by the groundwater flow. In addition, the simulation result of HGSHP operation predicted that the maximum temperature of heat carrier fluid would be lower than 30 oC in the 5th year’s operation even in the case where the cooling tower was not operated during cooling season. From this result, the cooling tower was not operated from 2nd year’s operation. Also, it was confirmed that the temperature of heat carrier fluid was lower than 30 oC. |