After R-134a, What?

For the refrigerant industry, these are days of change. The breakthrough chemical around which modern air conditioning was built, R-12, is unavailable, illegal, or both just about everywhere. Its replacement, R-134a, is about to disappear too after a much shorter run than the half-century that R-12 dominated. With global warming a much more serious environmental issue that originally thought even ten years ago, it was probably inevitable, but this time the changeover might require radically different technologies than A/C of the past, with implications for OEM’s and the service community.

OEM’s are actively researching alternatives, as are industry groups like the SAE.

According to Stefan Glober, Delphi Thermal & Interior director of engineering, Europe & South America, “Although automotive air conditioning accounts for less than five percent of total vehicle global warming potential and the current refrigerant, R134a, contributes less than 0.4 percent of total global warming gas emissions in Europe, worldwide concern over the impact of HFCs such as R134a caused us to search for alternative refrigerants.”

Delphi has researched several alternatives, and believes that two stand out as good future refrigerants.

R-152a is chemically and thermodynamically similar to R-134a. Although an HFC refrigerant like R-134a, R152a has a global warming potential rating (GWP 120) that is 94 percent lower than the current R134a (GWP 1300). Its improved cooling efficiency also has energy saving advantages.

CO2 (Which is called R-744 in the refrigeration trade) is also a promising candidate. It has a global warming potential rating of just 1.0 and is naturally occurring in the atmosphere. It has a comparable life cycle climate performance to R152a and provides an acceptable level of cooling performance. CO2 also operates more efficiently in the heat pump mode compared to HFCs. In terms of potential cost, a switch to CO2 likely presents higher development, manufacturing and service investment than would R152a, which can be used in adapted current-style systems.

Another Tier 1 OEM supplier, Visteon, has researched CO2. According to their data, CO2 systems improve air conditioning performance by reducing pull-down times, while higher system efficiencies can increase cooling performance or improve fuel economy. The firm believes that they can address the cost and packaging challenges through smaller and/or integrated components. Compressors and heat exchangers like condensers and evaporators for example, are similar in size to current units. Perhaps the biggest change should CO2 become widely adopted is regulatory. With an essentially non-greenhouse gas in the system, will you still need special training or permits to service the system? In theory, systems could be safely vented to the atmosphere, eliminating recovery and disposal issues. What about do-it-yourself? Will special equipment be needed to service CO2 systems? Will the gas be reasonably priced, readily available and safe to handle?

Chemically and thermodynamically, CO2 looks good, but mechanically, the major questions are about engineering. Some early research suggested that system pressures would be so high that A/C cooling would be by sealed units that are trunk-mounted and electrically driven, feeding cooling fluid through a secondary loop into the passenger compartment. Other recent research suggests that CO2 can be engineered into systems similar to current technology at reasonable pressures.

Conspicuous by its absence in OE-related research is hydrocarbon refrigerants. Normally a blend of isobutane and propane, HC refrigerants are used in home refrigeration in Europe extensively, and are a popular drop-in replacement for existing mobile A/C gases. OEM’s and Tier 1 suppliers have rejected hydrocarbons as possible OE technologies, primarily over flammability issues. Hydrocarbon proponents present data that suggests that fire risk is minimal under realistic conditions, but as a factory-fill, HC’s are unlikely to be an alternative in the near future. R-152a is a leading candidate. It is, however, flammable and OEM’s looking at are considering installing relief valves that would rapidly dump system pressure into a wheel well or under the vehicle in case of an accident. This technology may in turn remove some of the OEM’s risk aversion to hydrocarbon refrigerants as well. R-152a components and service procedures would otherwise be similar to R-134a. Will shops be able to service future A/C with existing training and equipment? The answer appears to be ‘yes’, at least for best practices shops that already use modern identifier/recovery equipment and keep their people current by training. SSGM

Check out SSGM next month for our annual air conditioning report for more on alternate gases and drop-in replacements.