On substances that deplete the ozone layer

Water heating heat pumps

Most heat pumps commercialised today make use of non-ODS refrigerants. Refrigerants used are R-410A, HFC-134a, R-407C, HC-290, HC-600a, R-717 and R-744. The majority of new equipment uses R-410A. In some Article 5 countries, HCFC-22 is being used due to its favourable thermodynamic properties and high efficiency. There are no technical barriers in replacing HCFC-22 by a non-ODS. The technical and process changes related to pressure, lubrication and contamination control are well known. Replacements are commercially available, technically proven and energy efficient. All replacements have a similar or lower environmental impact. R-410A has a slightly higher GWP but the required charge is less than HCFC-22. The issue of high ambient temperature conditions is of minor or no importance for water heating heat pumps. The main parameters to select the alternatives and the main issue to switch over from HFCF-22 are efficiency, cost effectiveness, economic impact, safe use and easiness of use. Replacements such as HFC-32 and other low-GWP HFC blends are under way to become commercially available.

HFC-134a, R-744 and HFC blends R-407C, R-417A and R-410A are commercially available solutions that have the highest grade of safety and easiness to use. R-410A is most cost effective for small and medium size systems, while for large systems HFC-134a is most efficient. R-407C and R-417A are the easiest alternatives for HCFC-22 from a design point of view, but cannot compete with the other HFC-solutions.

Chillers

The required global phase-out of HCFCs and the need to manage the lifetime operation of HCFC-based equipment, coupled with concerns to reduce global warming, continue to drive the transition from ozone depleting substance (ODS) refrigerants. The refrigerants that were used in the transition generally were HFCs with global warming potentials (GWPs) that are sufficiently high to cause environmental concerns, so a second transition has begun. Major efforts have been launched to propose and test new, lower GWP refrigerants to replace higher GWP refrigerants. A number of candidates have been proposed and are in the early stages of testing as possible replacements for higher-GWP HFCs.

The new candidates generally are unsaturated HFCs or blends which may contain HFCs, HCs, and/or unsaturated HFCs. A number of the new candidates have an A2L safety rating which is associated with flammability. They have a low flame velocity, distinguishing them from more flammable chemicals such as propane (HC-290). It is too early to tell which lower-GWP refrigerants will be successful as replacements for the higher GWP HFCs now in use. The parameters to be sorted out require balancing energy efficiency, flammability (including application standards and regulations), GWP values, cost, worldwide availability, retrofit considerations, and level of system design complexity that is required to use the new candidates successfully.

Vehicle air conditioning

At the end of 2014 it looks likely that more than one refrigerant will be used in the coming years for car and light truck air conditioning: HFC-134a will remain largely adopted worldwide, HFC-1234yf will continue its growth in new models at least in the near future, other new low GWP synthetic refrigerants or refrigerant blends (e.g. R-445A) may be implemented and R-744 is expected to be implemented by 2017. All options have GWPs below the EU threshold and can achieve fuel efficiencies comparable to modern HFC-134a systems. Currently it cannot be forecast whether or not all these refrigerants will see parallel use in the market for a long period of time. It is also unclear whether the bus and train sector will follow these trends.

The global warming impact is almost identical for the above mentioned refrigerant options when considered on a global basis and in comparison to the CO₂ tailpipe emissions. Adoption of any of the refrigerant choices would therefore be of similar environmental benefit. The decision of which refrigerant to choose will have to be made based on other considerations. Here, especially safety, cost, and system reliability are important concerns, but also other aspects have to be taken into account, like regulatory approval, heat pump capability, suitability for hybrid electric vehicles, servicing, and risk of illegal use of high-GWP refrigerants in systems designed for low-GWP refrigerants. In the year 2012, HFC-1234yf seemed to be the worldwide accepted alternative to HFC-134a. However, based on new findings regarding the on-the-road flammability of HFC-1234yf (classified as A2L) most German OEMs abandoned this option and decided to further develop and eventually use R-744 in their future air conditioning systems. Further, one Japanese OEM decided to not use HFC-1234yf on the European market. Similar to the 2012 acceptance of HFC-1234yf, these decisions are subject to change as the OEMs continue their pursuit of alternative refrigerants to meet regulatory requirements and other concerns mentioned above.

Owing to safety concerns hydrocarbons and their blends are not considered as viable refrigerant options by OEMs. Although HFC-1234yf is also flammable, it has a lower heat of combustion, burning velocity and minimum ignition energy compared to hydrocarbons, and has been the subject of several safety assessments by OEMs and other research bodies. Today, some OEMs use HFC-1234yf as refrigerant in some of their car models.

OEMs and suppliers do also work on future not-in-kind refrigeration concepts. However, the development status of such refrigeration technologies, like sorption, thermoelectric or magneto caloric systems, are still far away from serial production and presently show very poor price competitiveness and poor system performance and efficiency. These concepts are briefly discussed in Annex C of this report.

The increasingly rapid evolution of hybrid electric vehicles and electric vehicles with reversible air conditioning and heat pump cycles, which use semi hermetic electrically driven compressors introduces new challenges for any new alternative refrigerant.