DETROIT-It's long been considered a culprit in the ongoing debate about global warming.
But now carbon dioxide (CO2) is being touted as a possible remedy for the ozone-depleting flaws of current auto air conditioning systems.
A decade ago, auto makers and suppliers redesigned air conditioning systems to switch from chlorofluorocarbon-laded R12 refrigerant, which damaged the ozone layer, to the more environmentally friendly R134a refrigerant.
But while the new refrigerant did not do as much damage as R12-commonly known by the trade name Freon-it, too, could damage the atmosphere if released. This forced auto suppliers to redesign A/C sytems with new hoses and couplings to reduce leakage.
Now suppliers are promoting CO2 as a refrigerant that drastically lowers greenhouse gas emissions, improves system performance and could boost fuel economy. So how can such a substance closely associated with global warming and the greenhouse gas effect deliver such benefits?
Compressing the naturally occurring gas into a refrigerant to replace today's R134a will not put additional CO2 back into the atmosphere, backers of the new technology claim. But suppliers still have to prove CO2's cooling power and affordability to customers.
Denso Corp. and Behr GmbH & Co. are leading the way in bringing CO2-based systems to market, while others such as Visteon Corp. and Delphi Automotive Systems Corp. are developing their own systems. Denso even has an agreement to put the new technology into production for an experimental Toyota vehicle coming in 2003.
Some suppliers are betting big on the new refrigerant.
``I think it's a very good chance for Denso to expand the business,'' said Koichi Fukaya, managing director of Denso's thermal systems group.
Luxury vehicles for Europe and and Japan likely would be the first large-scale users of the technology, Mr. Fukaya said. But no volume contracts have been won.
A Behr executive predicts a CO2 system could be in volume production vehicles as early as the 2005 model year. The German supplier is working on development programs with possible customers, said Josef Kern, senior vice president of engineering for the Behr America Inc. unit. Fleet tests are planned in 2003 and 2004.
``So far, the decision to introduce CO2 is still open,'' Mr. Kern said. ``If there will be a replacement, it's the only one which makes sense.''
Supporters say that CO2 has virtually no global warming impact-unlike R134a-and that total emissions are cut in half. Maximum cooling performance is 15 percent better than that of R134a, and compressor shaft power needs are 15 percent lower on average, according to Mr. Kern. That translates to faster cool-down in many climates and possible fuel efficiency gains.
The CO2 system also allows for heat pump operation, leading to faster warm-up, according to Visteon officials. That could be a key selling point in the diesel-loving European market, since diesels often require a heat boost.
But not everyone is convinced.
``I don't feel the market is ready to accept it (CO2) now, primarily because of infrastructure issues,'' said Stefan Glober, director of engineering in Europe for Delphi's Harrison Thermal Systems unit.
Because a CO2 system must run at seven to eight times the pressure of the conventional system, all components must be re-engineered. More robust seals and other parts are needed, but the overall system cannot be heavier than today's system, Mr. Glober said.
That makes cost an issue. A CO2 system could cost 15 percent more than conventional technology, Mr. Kern said, though this should decline with volume production to a price equivalent to current technology.
Even if the new refrigerant is accepted, a 2006 or 2007 time frame is more likely for introduction, Mr. Glober said.
Stricter rules on greenhouse gas emissions could trigger acceptance of CO2, said Bob Vallance of Visteon's product marketing group.
Delphi has been working for a few years to bring a CO2 system to market and has two key customers in Europe doing development projects and joint testing.