Mobile Air Conditioning

Almost 100% of new passenger cars sold in the EU use HFO-1234yf as refrigerant

Mobile air conditioning is part of the vehicle control system that provides cooling, demisting, humidity control, as well as heating, defrosting and air-filtering. Directive 2006/40/EC on mobile air conditioning (MAC) required all new passenger cars (and light goods vehicles) from 1 January 2017 to be filled with a refrigerant with a global warming potential (GWP) no higher than 150. It should be noted that the Directive does not prescribe any specific refrigerant/system to fulfil this obligation but following extensive evaluation for performance and safety HFO-1234yf was selected by almost all vehicle manufacturers as the refrigerant to replace HFC-134a. Almost 100% of new passenger cars sold in the EU use HFO-1234yf as refrigerant.[1]

[1] From 2017, some German car manufacturers have introduced trans-critical CO2 systems for some premium models. R-744 has been demonstrated to be similar in efficiency as best in class HFC-134a systems for some experimental fleet vehicles, except when the vehicle is idling and also under high temperature conditions (above 35°C) see October 2014 TEAP XXV/5 Task Force Report.

Why was HFO-1234yf selected to replace HFC-134a?

The decision to select HFO-1234yf was based on assessments of its environmental effects, objective comparisons of its technical performance and an evaluation of its safety in use as it is a mildly flammable A2L refrigerant.

Ultra-low GWP

It has an extremely low GWP (<1, IPCC AR5 value), less than the GWP of CO2. The GWP listed in Annex II of the F-Gas Regulation 517/2014 is .4 (IPCC Fourth Assessment Report). The AR5 GWP value is more recent.  In comparison, HFC-134a has a GWP of 1430 (IPCC AR4 value referenced in the F-Gas Regulation, revised to 1300, the AR5 value)., and a very short atmospheric lifetime (10.5 days, AR5 value).

Environmental Safety

The environmental effects of HFO-1234yf have been thoroughly investigated. It breaks down in the atmosphere to form TFA, which is removed by dry deposition or rained out as it is very water soluble. It is well established that TFA is a ubiquitous natural component in rivers, lakes, and other surface water bodies. Amounts deposited in flowing surface water will ultimately accumulate in the oceans and salt lakes where water is lost only by evaporation.

The 2018 Environmental Effects Assessment Report[1] stated that “Estimates of production of TFA in China, the USA, and Europe, from the degradation of R-1234yf from its application in automobile air conditioners, and assuming no dilution, would be several orders of magnitude less than the chronic “no observable effect concentration” (NOEC) of 10,000,000 ng L–1 for TFA-Na salt from an  aquatic microcosms study.”  and “Overall, there is no new evidence that contradicts the conclusion of our previous Assessments that exposure to current and projected concentrations of salts of TFA in surface waters present a minimal risk to the health of humans and the environment. A recent review of this topic reached a similar conclusion.”[2]

Because of their high solubility in water and their very small octanol-water partition coefficient, the salts of TFA do not bioconcentrate in aquatic organisms, and do not biomagnify in the food chain. Thus they present negligible risk to organisms higher on the food chain, including humans.[3]

Further information about TFA and its emissions is on our website see LEARN ABOUT TFA For a while range of information about Trifluoroacetic acid/acetate as a breakdown product of some HFCs and some HFOs  at  https://www.fluorocarbons.org/wp-content/uploads/2020/10/EFCTC-Learn-About-TFA-2019F-1.pdf 

[1] Environmental Effects and Interactions of Stratospheric Ozone Depletion, UV Radiation, and Climate Change 2018 Assessment Report UN Environment Programme Section 5.1 Trifluoroacetic acid from replacements of ODS and refrigerants with large GWPs page 314

[2] The recent review is the Norwegian Environment Agency, 2017, Study on Environmental and Health Effects of HFO Refrigerants, Norwegian Environment Agency Report No. No. M-917|2017, Oslo, Norway, p. 349

[3] Ecological Issues on the feasibility of managing HFCs: Focus on TFA Inter-sessional informal meeting, 12-13 June 2015, UNEP Ozone Secretariat

Comparable energy consumption and reduced refrigerant emissions as CO2e

HFO-1234yf maintains comparable energy consumption to the HFC-134a systems it replaced, but considerably reduces the global warming impact of refrigerant emissions due to its ultra-low GWP.

A cooperative study by US EPA, Mobile Air Conditioning Society (MACS), and Japan Automobile Manufacturers Association (JAMA), for the Life Cycle Climate Performance (LCCP) found that for air-conditioning, HFO-1234yf, with a GWP <1, was the best performing option in all four selected climate regions: Frankfurt, Tokyo, Athens and Phoenix.

With the very low GWP of HFO 1234yf, the overall carbon footprint of vehicle air-conditioning is dominated by the energy efficiency of the system[1],[2] The relative LCCP for CO2 systems was improved under lower ambient temperature conditions but did not provide comparable energy efficient cooling in hotter climates where air conditioning demand is most stringent. The 2018 report commissioned by AFCE[3] also states that studies such as (Papasavva, 2014) have shown that, in a global context, R-1234yf is a better alternative than CO2, when considering all direct and indirect emissions during the life cycle (LCCP) of the vehicle and the refrigerant, even if CO2 showed slightly better performance in cold or temperate climate. The AFCE report also noted that one of the issues for the potential use of CO2 systems is reliability due to the high pressure and the increased risk of leakage at the rotating compressor drive shaft.

The automotive industry is a global industry, and overall global environmental performance in a range of climates is an important factor when selecting mobile air-conditioning systems. The LCCP (Life Cycle Climate Performance) is used as an objective comparison for refrigerants for a range of climatic conditions and drive cycles.[4]

New systems have better energy efficiency due to improved heat exchanger and compressor performance. Improvements to the thermal management of the passenger compartment can reduce the thermal load resulting in reduced MAC energy consumption. Engine compartment air-flow to remove heat from the condenser is are also important factor for energy consumption, particularly when a vehicle is at very low speed.

[1] TEAP Task Force Decision XX/8 Report May 2009 Assessment of Alternatives to HCFCs and HFCs and an Update of the TEAP 2005 Supplement Report Data page 46

[2] SAE International Industry Evaluation of low global warming potential refrigerant HFO-1234yf, Phase 3 Final Report completed October 2009 , which reports the Life Cycle Impact of HFO-1234yf in mobile air-conditioning systems and compares it to trans-critical CO2 systems

[3] Etat des lieux sur l’efficacite energetique des fluides et systemes a faible PRP disponibles. Etude commanditée par l’AFCE et réalisée par le Cemafroid, le CITEPA et EReIE. (Energy Efficient State of the Art of Available Low-GWP Refrigerants and Systems) Final Report September 2018 http://www.afce.asso.fr/wp-content/uploads/2018/10/Final-rapport-energy-efficiency-GWP-2018.pdf

[4] A well-established LCCP comparison tool is the GREEN-MAC-LCCP Model™, and guidance is available in a standard SAE J2766 Life Cycle Analysis to Estimate the CO2 – Equivalent Emissions from MAC Operation.

Similar technical properties

HFO-1234yf has very similar thermophysical properties to HFC-134a allowing the use of systems similar to the replaced HFC-134a systems. Some system changes compared to HFC-134a can be introduced, to optimize the energy efficiency of HFO-1234yf systems, with an internal heat exchanger (IHX) being an option to improve energy efficiency.

Safety in Use and Combustion Products

All fluorocarbon refrigerants have the potential to form dangerous combustion products and this has been known for over 50 years since the use of CFCs and HFCs, with technical advice and safety guidance provided. The advantage of fluorinated refrigerants is that they are typically much more difficult to ignite and have lower or non-flammability.

EU Joint Research Centre in-depth analysis for safety
In respect of R-1234yf, the EU Joint Research Centre was asked, in 2013, to provide an in-depth analysis[1] of the report elaborated by KBA (Kraftfahrt Bundesamt, German authority responsible for market surveillance and product safety for road vehicles), in order to ascertain whether the results stemming from the tests are well founded and supported by a rigorous and scientific methodology. In particular, the JRC was to clarify if, in the view of the aforementioned report, there is a reason to believe that refrigerant R1234yf may not operate in the vehicles with the appropriate level of safety, in the sense of the General Product Safety Directive (Directive 2001/95/EC) and the Framework Directive 2007/46/EC. The KBA performed a series of tests at three different levels, considering levels 1 and 2 for their assessment of possible risks within the scope of the statutory tasks as product safety authority, and level 3 tests as general risk appraisal. The level 1 and level 2 testing showed no ignition of refrigerant R1234yf and no release of hydrogen fluoride (HF) despite the very high temperatures in the engine compartment. Consequently, the results as such with the vehicles tested under the conditions as described for level 1 and level 2 testing provided no evidence of a serious risk. The refrigerant release tests under level 3 were not taken into account by the KBA as relevant input.  The KBA states also that “… (only) the levels 1 and 2 were considered relevant for a risk assessment with respect to the product safety regulations, as only these can be associated with the necessary concrete probability of occurrence.” This approach taken by the KBA is supported by the JRC because it reflects JRC’s understanding of Article 2(b) of the General Product Safety Directive 2001/95/EC in which is stated “…‘safe product’ shall mean any product which, under normal or reasonably foreseeable conditions of use (…) does not present any risk or only the minimum risks compatible with the product’s use…”. Therefore, drawing of conclusions from level 3 tests, further than the ones already drawn from level 1 and level 2 tests regarding the safe operation of the refrigerant R-1234yf in MAC systems, is not appropriate, considering the definition of “safe product” in the General Product Safety Directive 2001/95/EC.

In addition, the SAE International MAC Refrigerant Blend Cooperative Research Program consortium (MRB CRP) has thoroughly investigated the safe use of HFO-1234yf for car air-conditioning. Another Cooperative Research Program by the SAE confirmed previous conclusions that HFO-1234yf could be used safely for automotive air conditioning.

[1] The JRC technical and scientific support to the research on safety aspects of the use of refrigerant R1234yf on MAC systems issued in 2014. The complete report can be accessed with by searching for Ref. Ares(2014)573175 – 04/03/2014

Electric Passenger Cars

Hybrid electric cars typically use an electric compressor instead of a compressor driven from the engine. Plug-in hybrids and all electric vehicles also need temperature control for the batteries, in particular, cooling during the battery charging phase. For these systems, the MAC system can be configured to also provide cooling to the battery, which may be via a chiller loop or by a direct expansion evaporator.  For all electric vehicles, there is no combustion engine waste heat to provide heating which instead can be provided by a combined air-conditioner/heat-pump. The balance of cooling and heating requirements will depend on the climatic conditions and can have a significant impact on the vehicle range.

In cold winter conditions direct resistive heating by electric heaters to heat passenger compartment and drive battery can reduce the cruising range of a fully charged electric vehicle by up to half. HFO-1234yf based integrated thermal systems have been developed that can increase the winter cooling range by up to 20 percent.

Heavy duty trucks and buses

Heavy-duty trucks use MAC systems that are similar to those used for light duty vehicles, but with larger refrigerant charge. The choice of refrigerant (for trucks and buses) is not regulated by the Directive 2006/40/EC on mobile air conditioning (MAC), but some measures in the F-Gas Regulation 517/2014 will apply. Typically, at present heavy-duty trucks use HFC-134a.  Where air-conditioning is required while the truck is parked, an auxillary air-conditioning system may be installed.

Buses and Coaches have larger air-conditioning systems with refrigerant charge that may be ≥ 5kg depending on the size of the bus. Conventional engine driven vehicles use belt driven compressors and typically use HFC-134a or R-407C. At least one bus air-conditioner manufacturer in the EU has approved the use of non-flammable R-513A and R-450A as lower GWP alternatives to R-134a in its bus air conditioning systems.  With the lower GWP alternative refrigerants, the system delivers a virtually identical performance and have the same safety classification as R-134a (Class A1).

All electric buses require electrically driven systems, and depending on climatic conditions, some systems offer AC and heat pump functions to avoid the use of direct electrical heating. Typically, self-contained hermetic roof units containing non-flammable HFC-134a or R-407C are currently used.  Battery cooling may also be required to ensure optimum performance, and this may be provided by a direct refrigerant circuit or by a secondary glycol loop.