Presentation Information
[O02-04]Long-Term Energy-Saving Performance Assessment of Ground Source Heat Pump Systems Under Climate Change Scenarios★Invited Papers
*Yutaro Shimada1, Akira Tomigashi1 (1.National Institute of Advanced Industrial Science and Technology)
Keywords:
Ground Source Heat Pump,Climate Change Scenario,Energy Conservation
Ground source heat pumps (GSHPs) are a renewable heating and cooling technology that utilizes shallow subsurface (typically to depths of around 100 m) as a heat source/sink for space conditioning. Because the shallow subsurface exhibits relatively stable temperatures—cooler than ambient air in summer and warmer in winter—GSHPs can reduce electricity consumption compared with conventional air source heat pumps (ASHPs). Owing to this characteristic, GSHPs are expected to retain high energy-saving potential even under climate change.
Although previous studies have assessed future GSHP performance under climate scenarios, three issues remain in evaluating the advantage of GSHPs over ASHPs:
(1) Long-term continuous simulations over the system lifetime (50 years) have not been sufficiently conducted, making it difficult to account for performance changes caused by heat accumulation in the ground.
(2) Few studies have compared GSHP and ASHP performance under equivalent conditions; thus, the future energy-saving performance of GSHPs relative to ASHPs under altered weather conditions remains unclear.
(3) Most evaluations assume that GSHPs cover the entire building HVAC load, which can deviate from practical system design and operation.
To address these issues, this study focuses on a hybrid system combining GSHP and ASHP. We conducted continuous simulations over 50 years incorporating climate scenarios, and evaluated the energy-saving performance relative to an ASHP system.
The assessment consists of three steps:
(I) Future weather data were generated by downscaling global climate simulation outputs. Based on Shared Socioeconomic Pathways (SSPs), scenarios corresponding to approximately 1.8°C, 2.7°C, and 4.4°C warming were adopted.
(II) Using the future weather data as boundary conditions, HVAC loads for a three-dimensional building model were calculated with EnergyPlus.
(III) Using the calculated HVAC loads as boundary conditions, electricity consumption was estimated with plant models for GSHP and ASHP developed in a physics-based modeling environment (Modelica), and the energy-saving performance of GSHP was evaluated.
The results show that, if attention is paid to the ratio of annual cumulative cooling load to heating load, GSHPs can maintain an annual energy-saving rate comparable to the present level over the 50-year period relative to ASHPs. The sustained overall energy savings can be attributed to opposing trends in cooling and heating energy-saving rates: in all scenarios, these rates varied with changes in ground temperature, but their transitions exhibited counteracting tendencies.
These findings indicate that GSHPs may be able to preserve current energy-saving benefits for both heating and cooling even under climate change scenarios. However, because GSHP energy savings are strongly influenced by ground temperature changes induced by system operation, careful consideration of the balance between cooling and heating loads is essential.
Future work will optimize operational strategies for GSHP–ASHP systems under climate change scenarios and use the outcomes to quantify the environmental value of GSHP systems.
Although previous studies have assessed future GSHP performance under climate scenarios, three issues remain in evaluating the advantage of GSHPs over ASHPs:
(1) Long-term continuous simulations over the system lifetime (50 years) have not been sufficiently conducted, making it difficult to account for performance changes caused by heat accumulation in the ground.
(2) Few studies have compared GSHP and ASHP performance under equivalent conditions; thus, the future energy-saving performance of GSHPs relative to ASHPs under altered weather conditions remains unclear.
(3) Most evaluations assume that GSHPs cover the entire building HVAC load, which can deviate from practical system design and operation.
To address these issues, this study focuses on a hybrid system combining GSHP and ASHP. We conducted continuous simulations over 50 years incorporating climate scenarios, and evaluated the energy-saving performance relative to an ASHP system.
The assessment consists of three steps:
(I) Future weather data were generated by downscaling global climate simulation outputs. Based on Shared Socioeconomic Pathways (SSPs), scenarios corresponding to approximately 1.8°C, 2.7°C, and 4.4°C warming were adopted.
(II) Using the future weather data as boundary conditions, HVAC loads for a three-dimensional building model were calculated with EnergyPlus.
(III) Using the calculated HVAC loads as boundary conditions, electricity consumption was estimated with plant models for GSHP and ASHP developed in a physics-based modeling environment (Modelica), and the energy-saving performance of GSHP was evaluated.
The results show that, if attention is paid to the ratio of annual cumulative cooling load to heating load, GSHPs can maintain an annual energy-saving rate comparable to the present level over the 50-year period relative to ASHPs. The sustained overall energy savings can be attributed to opposing trends in cooling and heating energy-saving rates: in all scenarios, these rates varied with changes in ground temperature, but their transitions exhibited counteracting tendencies.
These findings indicate that GSHPs may be able to preserve current energy-saving benefits for both heating and cooling even under climate change scenarios. However, because GSHP energy savings are strongly influenced by ground temperature changes induced by system operation, careful consideration of the balance between cooling and heating loads is essential.
Future work will optimize operational strategies for GSHP–ASHP systems under climate change scenarios and use the outcomes to quantify the environmental value of GSHP systems.