Optimum bleeding rate of open loop ground source heat pump systems determined by hydrogeological modeling in Korea

Abstract:

This study aims to evaluate the influence of open loop ground source heat pump systems operation on hydrological conditions of aquifer. Test bed is located in Chuncheon, Korea. The step drawdown test was conducted in five stages for 300 minutes. The variation of groundwater levels by open loop ground source heat pump systems operation was estimated using Visual MODFLOW. Transmissivity ranged from 2.02×10^-4 to 9.36×10^-4, and storage coefficient ranged from 0.00067 to 0.021. The amount of optimum bleeding was calculated to be 240 m³/day. When bleeding will be 50, 90, 240 and 450 m³/day for 5 years, groundwater levels may decrease 1.84, 3.31, 8.89 and 17.0 m, respectively. If the amount of bleeding is 50 m³/day, the influence of bleeding will not reach the boundary regions of the Soyang River after 5 years. Regarding the open loop ground source heat pump system installed at the test bed, the amount of optimum bleeding in accordance with the stand are proposed by the government is 90 m³/day, which is 20% of the 450 m³/day circulation quantity of the system. However, if continuous bleeding of more than 90 m³/day occurs, then the radius of influence is expected to reach the boundary regions of the Soyang River after 5 years. These results indicate that amount of optimum bleeding differ in each open loop ground soured heat pump system. Therefore, the debate for the amount of optimum bleeding in open loop ground source heat pump systems is demanded. This work is supported by the Energy Efficiency and Resources of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea government Ministry of Knowledge Economy (No.20123040110010).