Simple index for onsite operation management of ground source heat pump systems in cooling-dominant regions

Sayaka Kindaichi and Daisaku Nishina

Renewable Energy, 2018, vol. 127, issue C, 182-194

Abstract: In ground source heat pump (GSHP) systems, large imbalances between cooling and heating loads cause a rise or decline in ground temperature because of thermal interference between multiple ground heat exchangers (GHEs). To evaluate annual changes in ground temperature, we applied a variable temperature penalty, which was simply obtained using measured data without computer simulation. First, we examined measured data for 3 years after completion of a hybrid GSHP system that had 70 borehole-type GHEs, combined with an air source heat pump unit. In the hybrid system, the GSHP showed high efficiency (coefficient of performance > 5.0) throughout the year and had a variable contribution between years with regard to cooling/heating output and time of operation. The amount of heat rejected to the ground by cooling reached ∼4.8 times that of heat extracted from the ground by heating after 3 years of operation. This imbalance produced ground temperature increases of ∼3 °C in an internal borehole. The variable temperature penalty reproduced the measured temperature increase, suggesting that the index is appropriate for assessing long-term ground temperature changes in the operation phase. This simple index allows operational improvement onsite and will aid the sustainable operation of GSHP systems in cooling-dominant regions.

Keywords: Ground source heat pump systems; Cooling-dominant regions; Borehole-type ground heat exchangers; Operational management; Variable temperature penalty (search for similar items in EconPapers)
Date: 2018
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Citations: View citations in EconPapers (2)

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Persistent link: https://EconPapers.repec.org/RePEc:eee:renene:v:127:y:2018:i:c:p:182-194

DOI: 10.1016/j.renene.2018.04.065

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