On CO2 Systems SAALFELDEN, AUSTRIA (Feb. 17, 2006) - The 2006 Mobile Air Conditioners Summit (MAC-Summit), co-hosted by the California Air Resources Board (CARB) and the European Commission (EU) focused on seeking a global approach to resolving mobile air conditioning (A/C) environmental concerns, especially CO2, in the face of recent European legislation, as well as more pending elsewhere, that bans the use of R-134a, a hydrofluorocarbon-based refrigerant. DATEEVENT1930Research on halogenated hydrocarbon auto A/C systems began.1939Packard is the first production vehicle to have an A/C system.1957Cadillac Eldorado Brougham is the first vehicle to have standard A/C.1970Environmental threat of halogenated hydrocarbon refrigerants identified.1987Montreal Protocol: Phase-out of hydrogenated hydrocarbon refrigerants.1990Transition to R-134a (hydrofluorocarbons) refrigerant begins.1994Transition to R-134a completed.1997Kyoto Protocol: Objective to reduce environmental impact of hydro fluorocarbons set.1998Lorentsen study detemines CO2 to be best "natural" refrigerant.1998Phoenix Alternate Refrigerant Symposium compares R134a to other alternatives.2001SAE Alternate Refrigerant Cooperative Research Program begins.2003Brussels Conference: legislation begins to be considered.2004California Air Resources Board proposes a 30% reduction of greenhouse gases by 2011 and a further 10% reduction by 2014.2005European Union bans R-134a by 2011. (Source: Delphi Corp.) Europe is the world's largest automobile market. Recently, the European Union's Parliament banned the use of R-134a (known as HFC-134a in Europe) effective Jan.1, 2011, because it is more than 1,000 times more damaging to the environment than CO2. A phasing out program in the interim is in effect. Finding the right mix of effective technology and refrigerant in time and at an affordable cost is the quest faced by automakers, suppliers, engineers and regulators who attended the summit.
Alternatives to R-134a, which harms the environment, have been discussed, studied and analyzed for the past decade, most notably by the Society of Automotive Engineers (SAE). Under test bench conditions, various technologies - such as an enhanced R-134a system, R152a (more environmentally efficient than R-134a, but highly flammable), CO2, secondary loops, heat exchangers and others - have been compared to baseline R-134a performance. These comparisons measured cooling, environmental impact, fuel consumption, safety and cost. In addition, studies of alternate "natural" refrigerants - including air, ammonia, hydrocarbons and CO2 - have been conducted.
According to Delphi Corp., CO2 (also known as R744) systems have shown the ability to compete in performance and efficiency. Strengths include having the lowest impact on the environment and a median safety risk compared to other systems. But the lower impact comes at a price. Both "changeover" from R-134a and manufacturing costs for CO2 systems are more expensive than some other solutions. The consideration of regulators and legislators, however, appears to weight environmental impact above raw costs.
In 2005, the European Union became the first jurisdiction to impose a ban on R-134a, with the United States, Japan and other countries also showing concern about the leakage and effect of the hydrofluorocarbon refrigerants - much of it arising from the Kyoto Protocol in 1997. A pending proposal by CARB outlines a similar approach to a phase-out of R-134a in California; it favors use of refrigerants with a lower global warming rating for motor vehicle applications. In addition, California will provide more governance of the servicing and end-of-life of mobile air conditioners, by implementing minimum qualifications and certification of servicing personnel and setting of high standards for mobile A/C service equipment.
Delphi's CO2 gas cooler.
(Photo: Delphi Corp.)
These proposals and others are aimed at reducing California 's carbon footprint. California 's plans give further impetus and relevance to the global introduction of alternative refrigerants. CARB has said it recognizes the European Commission's leadership and, therefore, intends to work cooperatively to ensure advancement and regulatory consistency.
Summit attendees acknowledged that finding a common viable global solution was in everyone's interest. Representatives agreed to work towards harmonizing the analysis of lifecycle emission impacts of refrigerants, safety standards for CO2 systems at the lowest cost, and the methods for quantifying both direct and indirect mobile A/C emissions. Furthermore, regulators committed themselves to identify unintended barriers to introduce alternative refrigerants by the end of 2006 and make every effort to remove them by end of 2008.
During the course of the conference, five companies - Behr, Obrist, Valeo and Visteon - displayed vehicles that incorporated CO2 A/C systems. Other companies, including Delphi, have demonstrated CO2 solutions at earlier summits. Automakers present at the summit said they were not considering R152a anymore, opting instead for CO2.
(Photo: Delphi Corp.) As well, some automakers have demonstrated their commitment to a natural cooling system, with reports of their fleets of CO2-based A/C-equipped vehicles being road-tested in Europe today. While some experts and regulators suggested 100,000 CO2 A/C system cars would be sold in the EU by 2008 and 2 million by 2011, most automakers said that timetable was unrealistically high. Regulators responded that the phaseout time for R-134a was much longer than in any other environmental regulation in the past.
Delphi, a presenter at former summits, notes in a separate press statement that the use of CO2 as a refrigerant is not new. Before the development of halogenated hydrocarbons in the 1930s, it was commonly used, notably in marine applications. But despite the resurgence of CO2 now that the environment has become more important than the lowest cost, it does require the addressing of some concerns.
Delphi noted that in an analysis of pressure-enthalapy diagrams for CO2 verses R-134a, CO2 has a substantially different "trans-critical nature" and operates at much higher pressures. In the first case, more stringent system controls would be needed. In the latter case, the design of system components would need to be modified.
(Photo: Delphi Corp.) Delphi found that using an external heat exchanger, the cooled refrigerant leaving the evaporator could be used to cool the gas leaving the gas cooler, resulting in a significant amount of added cooling gained from a relatively smaller increase in compressor work. Relative to R-134a cooling systems, the design changes to handle CO2 included more expensive face seals, heat exchangers that could handle higher pressure capacity, and evaporators that had a much sturdier construction - incorporating micro-channel tubing and thicker-walled manifolding. To resolve the increased capacity and head pressure concerns, Delphi employed an electronically controlled expansion valve and an externally controlled compressor.
Dr. Stefan Glober, director of engineering for Delphi Thermal and Interior in Europe said, "Looking at alternative refrigerants alone is not enough. We are also looking at how we engineer our air conditioning systems to better accommodate a change in refrigerant, providing complete system support to our customers." He also noted that the latest version of the company's CO2 compressor in road trials with one major European automaker was "deemed very competitive in terms of performance, stability and controllability."
(Photo: Delphi Corp.) Just prior to the Summit two global chemical companies, Honeywell and DuPont, announced that they had developed new refrigerants that were "potentially" low in their global warning impacts and that also could be used in mobile A/C applications, as their chemical properties are likely to be close to R-134a. Both claim that their new refrigerants have lower global warming impacts than current refrigerants and that the new refrigerants don't require the radical design changes and implementation costs associated with CO2 systems. These completely new refrigerants are still in the test phase. While regulators and industry at the MAC-Summit welcomed these announcements - as it increases competition by creating potential downward price pressure on CO2 and other alternatives - but noted that being approved, let alone being developed to market readiness in time, is no certainty. Like sand passing through an hourglass, 2011 is fast approaching. More urgently, automakers know the decision-making timeframe to be ready with production vehicles by 2011 is now.(Sources: 2006 MAC-Summit; Delphi Corp.; Air Conditioning, Heating, and Refrigeration News)
