Evaluation of ground temperature changes by the operation of the geothermal heat pump system and climate change in korea

Abstract

To evaluate long-term temperature changes caused by the operation of a geothermal heat pump (GHP) system, temperatures near borehole heat exchangers (BHEs) of the GHP system in Korea were measured. The temperature measurements showed increasing rates of 0.135◦ C/year at a depth of 10 m and 0.118◦ C/year at a depth of 50 m for approximately 10 years. Simulations for the analysis of climate change effects on measured temperature fluctuations showed that a rate of temperature increase was 0.010◦ C/year at a depth of 50 m owing to changes in surface air temperatures (SATs). From two-dimensional heat transfer simulations, the discharged heat measuring 16.7 W/m in the cooling season and extracted heat measuring 12.4 W/m in the heating season could cause an annual mean temperature increase of 0.109◦ C over approximately 10 years. Additionally, results of simulations for future prediction of ground temperatures assuming that the GHP system retains its level of operation showed that in 2050, temperature at a depth of 50 m will increase by approximately 3.00◦ C from that in 2005. Thus, balancing the heat discharged into and extracted from the ground by considering climate change to minimize long-term changes in the ground temperature is necessary.