Long-term operation analysis of a ground source heat pump with an air source heat pump as an auxiliary heat source in a warm region

With the urgent need to achieve carbon neutrality, there are growing expectations for ground source heat pump (GSHP) systems. This study analyzed the long-term operational performance of a GSHP in combi-nation with a modular-type ground source heat pump (ASHP) installed at a university in a warmer region of Japan. As results, in warmer regions, as the cooling load tends to be greater than the heating load and the electrical consumption heat from the GSHP is added to the rejection heat to the ground, the ground heat balance is more likely to be unbalanced than it would be in colder regions. Predominant rejection into the ground for extraction from the ground resulted in an increase in ground temperature and a decrease in the SCOP of the GSHP during cooling periods. However, a decrease in the cooling load in one season considerably reduced the ground temperature during cooling in the following season. Because the module-type ASHP was able to quickly control its thermal output, it unexpectedly reacted HVAC load fluctuations before the GSHP output control. This lowered the load factor of the GSHP and caused the ASHP to start and stop repeatedly at extremely low loads.(c) 2023 Published by Elsevier B.V.

Automated summary

This study analyzed the long-term operational performance of a modular-type ground source heat pump (ASHP) combined with a ground source heat pump (GSHP) system installed at a university in a warmer region of Japan. The results showed that in warmer regions, the imbalance of ground heat balance is more likely due to the cooling load being greater than the heating load and the addition of electrical consumption heat from the GSHP to the rejection heat to the ground. The increase in ground temperature and decrease in the seasonal performance coefficient (SCOP) of the GSHP during cooling periods are caused by the predominant rejection into the ground for extraction from the ground. However, a decrease in the cooling load in one season significantly reduces the ground temperature during cooling in the following season. The module-type ASHP can quickly control its thermal output and react to HVAC load fluctuations before GSHP output control, which lowers the load factor of the GSHP and causes the ASHP to start and stop repeatedly at extremely low loads.