Transportation's Role in Reducing U.S. Greenhouse Gas Emissions ...

Transportations Role in Reducing U.S. Greenhouse Gas Emissions: Volume 2
offset to some degree by an increase in the demand for professional MAC service. This
type of legislation is meeting resistance in California because it may disproportionately
target low-income citizens as these individuals make up a significant percentage of the
DIY market. In addition, there would be an overall loss of utility as some people would
choose to go without air conditioning. A refill deposit program would have fewer
barriers to implementation, although it would likely be somewhat less effective. In this
case, refrigerant suppliers would need to expand their delivery logistics to include the
reclamation of used containers from retail outlets that receive their products.
Environmental fees on DIY small cans would have primarily legislative barriers to
implementation (CARB, 2008c). California has chosen a refill can deposit program in
which cans must be self sealing, and an $11 deposit is added to the purchase price of the
can and refunded when the container is returned intact. According to CARB, this strategy
has the most favorable cost/benefit ratio and avoids the issue of unfairly targeting lowerincome
motorists. In addition, strategies that target servicing and EOL emissions also can
impact reductions substantially in the near term, unlike those measures involving MAC
system modifications which require time for new vehicles to penetrate the fleet.
The feasibility of alternative refrigerants is based on their safety, efficiency, and cost
characteristics. While HFC-1234yf has a low GWP and its associated system is efficient, it
does have a high material cost and is flammable. HFC-152a also is flammable, and it is
more toxic than HFC-1234yf and HFC-134a. Currently, many States prohibit toxic or
flammable refrigerants. However, renewed interest in these refrigerants is prompting a
review of these requirements. The automotive community is working on designs to
minimize the risks of toxicity and flammability, and the literature suggests a consensus
that these problems can be overcome. R-744, or CO2, can be toxic to passengers in the case
of a sudden system depressurization, and requires significant and expensive changes to
the designs of MAC systems. This is because these systems will not use gas-to-liquid
phase change as is typically the case in conventional refrigeration cycles. Because of this,
R-744 systems are not as effective in warm climates and they are not as efficient, resulting
in higher fuel consumption for cooling (Andersen, 2008). Finally, as discussed above, the
CO2 emissions associated with MAC-related engine loads are comparable to, or even more
significant than, the actual refrigerant impacts. As such, evaluations of alternative
refrigerant options must include a careful evaluation of differential engine load impacts
before settling on a preferred strategy.
The move to an alternative refrigerant could take place in a manner similar to the change
from R-12 to HFC-134a that occurred in the early 1990s. It is estimated that the conversion
to HFC-134a cost automotive manufacturers and the service industry $8.5 billion, while
the next change to a new refrigerant could cost over $40 billion. It is important that this
conversion is performed at least at the national-level, and possibly at the internationallevel
in order to keep costs to industry reasonable. According to the literature, the choice
of refrigerant does not appear to be driven by cost. Each refrigerant’s advantages and
disadvantages are significant enough to outweigh cost differences among them. The EU
set a date for HFC-134a phase out before there was agreement on which refrigerant would
be the best alternative. While the EU assumes that a new refrigerant will have any
remaining technical issues resolved by this time, determining the preferred refrigerant in
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