The Future of Refrigerants for Automotive Air Conditioning

by Barbara H. Minor, DuPont Engineering Fellow

Why is a new refrigerant solution necessary for automotive air conditioning, also known as mobile air conditioning (MAC), worldwide?

Current environmental regulations in Europe, as well as other industry factors, necessitate a new refrigerant solution for MAC systems with a lower global warming potential.

Specifically, the European Union (EU) F-Gas Regulation phases out HFC-134a in MAC systems for new production cars over a period of six years. Beginning January 1, 2011, HFC-134a will be phased out for air conditioning systems for new vehicle models. By January 1, 2017, it will be banned for all new vehicles. The regulations also require that the next generation MAC refrigerant has a global warming potential (GWP) of less than 150. In addition, MAC leak rate restrictions will go into effect in 2008, and there will be strict inspection and repair regulations for other refrigerants.

In the U.S., the California Air Resources Board (CARB) has proposed a regulation that would include the phaseout of HFC-134a from heavy equipment starting in 2010 and from cars starting in 2017. This would be in addition to voluntary steps that the industry has already taken to reduce greenhouse gas emissions, including MAC refrigerant emissions, from vehicles beginning in 2009.

Finally, the MAC industry broadly has indicated it wants a single global solution that can be easily manufactured around the world and one which provides a cost-effective transition for the entire automotive value chain.

What are the challenges in developing a new MAC refrigerant?

Many conditions must be met in order for the next generation MAC refrigerant to be accepted by the industry. These include: safety, environmental and performance requirements, ease-of-use, and affordability.

The new MAC refrigerant must meet specific safety standards, including acceptable toxicity and flammability. From an environmental perspective, it must have zero ozone depletion potential (ODP), low GWP and good Life Cycle Climate Performance (LCCP) - a calculation that evaluates greenhouse gas (GHG) emissions from direct and indirect sources. The new refrigerant also needs to meet specific performance criteria, such as thermal stability, materials compatibility, lubricant miscibility and cooling capacity in all climates and car models, as well as energy efficiency and compatibility with conventional MAC system technology. Finally, as requested by the MAC industry, the new refrigerant should follow the EU F-Gas directive, be easily manufactured and enable a cost-effective transition.

Why is DuPont committed to developing the next-generation solution for MAC systems?

With more than 75 years of proven leadership in refrigerants science and technology, DuPont is heavily invested in R&D to develop more sustainable solutions and to lead the industry toward cooling technologies that meet environmental regulations and performance requirements.

Through DuPont science, we see real potential to bring significantly more environmentally-sound solutions to the MAC market, within the time frame demanded by our global customers and industry regulations, such as the F-Gas Regulation, in Europe.

What is HFO-1234yf and why is it expected to become the preferred global alternative refrigerant candidate for the automotive aftermarket?

Shown here, Barbara Minor conducts a thermal stability test on a new refrigerant candidate.

What industry tests have been conducted on HFO-1234yf to date? What were the results?

Bench scale tests have been conducted on HFO-1234yf with cooling capacity and energy efficiency within five percent of R-134a without any adjustments to the system. Additional improvements can be achieved with optimization of TXV and suction line size. These results have been confirmed in vehicle tests with several automotive OEMs. Additional tests, including thermal stability, materials compatibility (plastics and elastomers) and lubricant miscibility, have also been completed. All test results indicate that HFO-1234yf can be used in conventional R-134a design systems with minimal to no modification.

Where in the development phase is HFO-1234yf?

DuPont and Honeywell are working to accelerate process technology developments to support a future commercialization plan to help the industry meet the F-Gas Regulation phaseout deadlines.

Multiple OEM/Tier-1 tests are currently in progress. These tests include vehicle performance testing and completion of regional flammability risk assessments in the United States, Europe and Japan to confirm the use of HFO-1234yf in direct expansion systems. Preliminary results confirm that HFO-1234yf has the potential to be used in a direct expansion system without a secondary loop. In addition, DuPont and Honeywell are continuing comprehensive assessments on toxicity and environmental impact of HFO-1234yf. Refer to the most up-to-date information on HFO-1234yf.

About the Author

Ms. Minor is an engineering fellow for Refrigerants in DuPont's Fluoroproducts division based in Wilmington, Delaware.

Ms. Minor has more than 18 years experience in the refrigerants industry. Ms. Minor began her career in Wilmington and gained experience in a variety of plant process, technical service, and product development assignments across multiple strategic business units at DuPont.

Ms. Minor holds over 80 U.S. patents for refrigerants, cleaning agents and aerosol propellants as well as several publications in the field. In 2002, Ms. Minor was named DuPont Scientist of the Month and was featured on the cover of Woman Engineer magazine. She is an active member of the Air Conditioning, Refrigeration and Technology Institute serving on the AHRI Steering Committee, and Research and Technology Committee. Barbara is also a member of ASHRAE and is currently Chair of TC 3.1 - Refrigerants and Secondary Coolants and past Chair of TG10.MOC - Immiscible Oil-Refrigerant Systems.