Issues to improve ground source heat pump units in Korea: Refrigerant application and hot water generation

There is a need for hot water generation in a more efficient and environmentally friendly way for heating, ventilating, and air conditioning systems, and the heat pump is a great candidate for that. In this paper, hot water temperatures generated by ground source heat pump (GSHP) systems in Korea are analysed. It is also important to minimize the use and emission of refrigerants with high global warming potential (GWP) and ozone depletion potential (ODP) to reduce their impact on the environment. In this regard, refrigerants that are used in GSHP units in Korea are investigated. The database is composed of 86 GSHP units certified in Korea according to governmental regulation. The GSHP units are divided into three types: water-to-water, water-to-air, and water-to-air multi heat pump units. The average hot water temperature generated by the certified GSHP units is 43.8 °C with the Korean standard test conditions (NR GT 101). Temperature difference 3.8 °C between inlet and outlet of condenser is less than 5 °C as presented by the European Standard (NF EN standard). In order to replace the boiler and the conventional air conditioning unit with a highly efficient GSHP system, there is the need to increase the hot water generation temperature. With the refrigerants, 53.8% of the 78 water-to-water GSHP units use the hydro chlorofluorocarbon (HCFC) refrigerant, R22, while the others use the hydrofluorocarbon (HFC) refrigerants, R410A, R407C, and R134a. All water-to-air and water-to-air multi heat pump units use R410A refrigerant. Because R22 is a HCFC and has high GWP and ODP, it is being replaced with HFC and natural refrigerants. However, HFC refrigerants also have high GWP. It is therefore recommended to encourage the responsible use or replacement of HFC refrigerants with natural and other alternative refrigerants in Korea.