Data, exergy, and energy analyses of a vertical-bore, ground-source heat pump for domestic water heating under simulated occupancy conditions

• Exergy and energy analysis of a vertical-bore ground source heat pump for water heating over a 12-month period is presented.
• The ground provided 68%–76% of the energy to produce domestic hot water.
• Performance metrics are presented.
• Sources of systemic inefficiency are identified and prioritized using exergy analysis.
• Performance metrics suggests the value of using the ground as a renewable energy resource to mitigate climate change.

Evidence is provided to support the view that 68%–76% of the energy required to produce domestic hot water may be extracted from the ground which serves as a renewable energy resource. The case refers to a 345 m2 research house located in Oak Ridge, Tennessee, 36.01°N 84.26°W in a mixed-humid climate with HDD of 2218 °C-days (3993 °F-days) and CDD of 723 °C-days (1301 °F-days). The house is operated under simulated occupancy conditions in which the hot water use protocol is based on the Building America Research Benchmark Definition which captures the water consumption lifestyles of the average family in the United States. The 5.3 kW (1.5-ton) water-to-water ground source heat pump (WW-GSHP) shared the same vertical bore with a separate 7.56 KW water-to-air ground source heat pump for space conditioning the same house. Energy and exergy analysis of data collected continuously over a twelve month period provide performance metrics and sources of inherent systemic inefficiencies. Data and analyses are vital to better understand how WW-GSHPs may be further improved to enable the ground to be used as a practical renewable energy resource.