Heat pump systems are often considered as one of the major contributors to environmental problems due to the usage of chlorofluoro, hydrochlorofluoro, and hydrofluoro carbon-based refrigerants. Earlier versions of refrigerants used to have high ODP as well as GWP. However, next generation refrigerants that are environmentally benign with excellent thermophysical properties are still under development stage. This study reviews the historical development of refrigerants, their environmental impacts and observes the viewpoint for present options in terms of Montreal Protocol, Kyoto Protocol, and EU F-gas regulation. The discussion extends to the actions of international agreements on the phase-out of hydrochlorofluorocarbons for developed and developing countries. This study also highlights the approach of large heat pump industries in Asia region regarding the use of various refrigerants. The direct CO2 emission per year from air-conditioning and refrigeration sectors due to the system leakage is assessed. It also examines the major contributors of CO2 emission in every year among the various sectors for providing per kilowatt cooling effect. Finally, the ideal cycle performance is compared to various refrigerants and stated the current best option.
Keywords: CO2 emission, environmental assessment, heat pump system, refrigerant