Ground-source integrated heat pumps for high-performance residences across the United States

Heat pumps can increase energy efficiency, thereby helping achieve high-performance residences. However, air-source heat pumps (ASHPs) sometimes use inefficient auxiliary heating in cold climates, and ground-source heat pumps (GSHPs) sometimes suffer from ground thermal imbalance and extreme entering liquid temperatures (ELTs) that reduce capacity. High-efficiency integrated heat pumps (HPs) can overcome these challenges; however, their long-term performance has been far less investigated than that of conventional or single-function HP systems. This study addresses these gaps by evaluating a ground-source integrated heat pump (GSIHP) with variable-speed components that provides heating, cooling, and all the domestic hot water (DHW). For humidity control, the GSIHP has a dehumidification mode and is supplemented by a separate whole-house dehumidifier. We also compared a two-capacity ASHP with dedicated dehumidification, a two-capacity GSHP supplemented by the dehumidifier, and a variable-speed GSHP (GSHP-VS, identical to GSIHP but without DHW capability) with the dehumidifier; in all these cases, the DHW was provided by a standalone heat pump water heater (HPWH). TRNSYS was used to simulate the GSIHP and the compared options in a residence over a 10-year timeframe, in six representative U.S. climate zones. The model is based on a research test house that incorporates photovoltaics and advanced construction methods to achieve high performance. The GSIHP reduced the 10-year average HVAC plus DHW energy consumption across the climate zones by an average of 43 %, 41 %, and 18 %, respectively, compared to the ASHP, GSHP, and GSHP-VS. The GSIHP also reduced the peak electrical demand on average by 63 %, 59 %, and 23 % compared to these options. The GSIHP eliminated auxiliary heating in most regions and significantly reduced the PV size needed to achieve net-zero energy. The findings highlight the GSIHP’s potential as an energy-efficient HVAC solution that also reduces grid stress, making it an attractive option for high-performance residences across the U.S.