Progress in ground-source heat pumps using natural refrigerants

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Original languageEnglish
Pages (from-to)70-85
Journal / PublicationInternational Journal of Refrigeration
Online published25 May 2018
Publication statusPublished - Aug 2018
Externally publishedYes


Natural refrigerants are attractive candidates for replacing the high Global-Warming-Potential fluorinated refrigerants used in ground-source heat pumps (GSHPs). This paper presents a comprehensive survey on GSHPs using CO2, NH3, water, and hydrocarbons. We compared the refrigerants’ thermodynamic properties, analyzed their performance in brine-to-air and brine-to-water GSHPs, and discussed recent progress in their use in GSHPs. Studies of CO2 were the most common due to its favorable properties, covering advanced cycles, direct-expansion, secondary fluid, and hybrid GSHPs. Though with toxicity concerns, NH3 was the second most studied, including vapor-compression GSHPs for heating, absorption-type GSHPs to eliminate ground imbalance, and hybrid compression-absorption GSHPs to widen the operating temperature range. A few studies evaluated water as a refrigerant for absorption-type GSHPs, including applications for solar cooling, ground imbalance, and district heating. Propane was the only hydrocarbon considered for GSHPs, including analyses on refrigerant charge, performance analysis, and propane as a secondary fluid.

Research Area(s)

  • Ammonia, Carbon dioxide, Ground-source heat pump, Hydrocarbon, Natural refrigerant, Water