2024 Volume 80 Issue 27 Article ID: 24-27047
This study conducted a nation-scale evaluation of changes in CO2 emissions from a ground-source heat pump system when the effective thermal conductivity increases due to groundwater flow, resulting in apparent thermal conductivity. The evaluation was performed for different office buildings (with floor areas of 300 m² and 2000 m²) and various Darcy flow velocities (50, 100, 250, and 500 m/year). The regionally averaged changes in CO2 emissions increased with higher flow velocities, but remained within a range of a few to ten times. The changes in the same assumptions of Darcy velocity were larger and more variable in warmer regions compared to colder regions. For larger buildings, the changes in emissions were smaller in warmer regions and larger in colder regions compared to the proportional increase in building size due to the product characteristics of the heat pumps. These results indicate that considering apparent thermal conductivity improves the accuracy of CO2 emissions estimates, while site-specific estimates based on thermal loads and groundwater flows become crucial.
