Their efforts are being driven by pending legislation in Europe that may end up banning the use of HFCs in automotive air conditioning. These environmentally and politically driven efforts seek to curtail the use of HFCs in stationary equipment.
Research is showing that cost and energy efficiencies of CO2 systems are starting to fall in line with similar equipment using HFCs.
Steve Memory of Modine Manufacturing reported on proposals and pending legislation within the European Union that could start a phaseout of the use of HFC-134a in mobile air conditioning by 2010. While such legal action is yet to be finalized, Memory said, "It is going to happen. They are just wrangling over a few points."
The EU nations manufacture 17 million vehicles a year, Memory said, making it the largest car market in the world. He noted that because many European car manufacturers are in a five-year cycle to introduce cars to the market, design research on the use of 134a alternatives "has to start now."
Such research currently involves CO2 systems with variable-displacement compressors, gas coolers, accumulator tanks, and hot gas circuits to provide heating as well as air conditioning.
"CO2 is good for that because its high volumetric efficiencies can make packaging smaller and the efficiencies are very good in these systems," Memory said.
He noted that even in the early stages of CO2 research, "The cost versus 134a has little cost penalties, and they will come down." He added that CO2 is not regulated for recovery and recycling and it can be vented legally. Charging stations and leak detection devices are available for use with CO2 refrigerant.
U.S. Army Examines CO2John Manzione, an engineer with the U.S. Army, said the military currently uses 134a in mobile air conditioning applications and has no plans to change from that. However, other options are being looked at and experiments are now being conducted with CO2, he said.
The process began with computer modeling, then moved on to lab experiments, and has now reached the prototype stage, he continued. The next step would be full-scale system development and demonstration.
Manzione said CO2 systems would need to be "embedded into the industry" and available "off the shelf" before the Army would consider switching. But he did note that zero ozone depletion, a "zero net global warming potential," nonflammability, and nontoxicity are factors to consider.
Moreover, the Army often has to do equipment servicing "in the field and on the fly"; CO2's legal venting without recovery is worth considering.
Manufacturers Are InterestedTravis Horton of Tecumseh Products said his company is "committed to understanding and developing technology that will enable the use of CO2 in HVACR. CO2 will find a future."
He said Tecumseh is focusing on the issue of what lubricants work best with CO2 in various applications. The company is looking at CO2 in rotary and recip compressors and in single- and two-stage models. Other considerations involve seals and valve stress. Horton said decisions would be based on both technical feasibility and good business sense.
Jurgen Suss of Danfoss said the company is reviewing CO2 on the heating side of heat pumps and in reach-in refrigerators. He noted that Danfoss began the studies in 2001 by looking at redesigned HFC compressors.
The following year, it directed its efforts at a simplified drive system, followed by performance and safety studies. Now it is studying cost and reliability.
"There are energy savings for CO2 in certain configurations," he said. "Tests have been done in the lab and in the field, often with a CO2 unit next to an HFC unit.
"We still have a long way to go," he cautioned, especially to reach the stage where reliable units can be mass-produced at a cost that is competitive with HFC units.
Gaku Shimada of Sanyo said his company is looking at CO2 in two-stage rotary compressors. He said the company is coping with the refrigerant's high working pressures by using an internal intermediate pressure structure. "The advantage of two-stage is the inter-cooler," he said, "which can reduce the temperature of the final discharge."
He said the Japanese market has embraced CO2 heat pump/water coolers since 2002, when the government provided a subsidy to end users. The August Summer Olympics in Athens will have soft drink vending machines running on CO2.
He said that in addition to heat pump/water coolers and vending machines, Sanyo is looking at CO2 refrigerant in glass door merchandisers, ice cream cases, and other refrigeration applications.
Publication date: 08/23/2004