HFC-134a replaced CFC-12 in virtually all vehicle air conditioners produced after 1993/94. Motor vehicle air conditioning uses HFC-134a refrigerant in an integrated system of components that provide cooling, heating, defrosting, demisting, air filtering, and humidity control. It is technically and economically feasible to significantly reduce emissions of HFC-134a refrigerants: by recovery and recycling of refrigerant during servicing and vehicle disposal; by using high quality components with low leakage rates, hoses with lower permeation rates, and improved connections; and by minimizing refrigerant charge. Efficiency improvements and smaller, lighter units can further reduce energy-related CO2 emissions. New systems using alternative refrigerants carbon dioxide or hydrocarbons are being developed as described below (see Section A3.2.1.3).
Globally, 65%75% of air-conditioned vehicles in service in 2000 have HFC-134a air conditioners and it is predicted that between 2000 and 2010, 70%80% of all new vehicles will have HFC-134a air conditioners. This projection assumes a continuation of current trends of mobile air conditioning installed in vehicles in normally cool climates where air conditioning may not be necessary. When air conditioning systems were redesigned to use HFC-134a, vehicle manufacturers used a smaller refrigerant charge and reduced leakage rates. Typical direct HFC emissions over a 10-year period in the USA are 1.4 kg if recycling is undertaken during service and disposal and 3.2 kg without recycling (Baker, 2000). Estimates for HFC-134a air conditioner emissions are included in Table A3.3.
Table A3.3: Estimated global HFC-134a
emissions for vehicle air conditioning Source: Baker (1999). |
||||
Year |
Vehicles w/134a A/C
|
Recycle at service/disposal
|
HFC-134a use
|
HFC-134a emissions
|
(million)
|
(%)
|
(kt)
|
(kt)
|
|
2000 |
214-247
|
60
|
64-74
|
31-35
|
2010 |
464-530
|
60
|
58-79
|
37-54
|
Vehicle manufacturers and their suppliers are working to increase the energy efficiency and reduce the emissions of HFC-134a systems. Typical CO2 exhaust emissions resulting from air-conditioner operation are in the range of 2% to 10% of total vehicle CO2 emissions (SAE, 2000). Comparison of reduced emissions HFC-134 systems and CO2 systems have been published (Petitjean et al., 2000; March, 1998). HFC-134a systems can be redesigned for higher energy efficiency and smaller refrigerant charge within 24 years, and manufacturers of replacement parts could supply high-quality components within 24 years (SAE, 2000). SAE (2000) estimates that improved HFC-134a systems can be introduced faster and at lower incremental cost than carbon dioxide, hydrocarbon, and HFC-152a systems.
Lowering the demand for cooling and humidity control can reduce indirect emissions from fuel consumption and could allow smaller air conditioning systems having reduced refrigerant charges. This is accomplished by increasing thermal insulation and decreasing thermal mass in the passenger compartment, by sealing the vehicle body against unwanted air infiltration, by minimizing heat transfer through window glass, and by controlling the compressor to minimize over-cooling and subsequent re-heating of air.
Considerable activity is underway to develop alternatives to HFC-134a air conditioning systems for vehicles. Prominent efforts are the European Refrigeration and Automotive Climate Systems under Environmental Aspects (RACE) Project (Gentner, 1998), and the Society of Automotive Engineers/US EPA/Mobile Air Conditioning Society Worldwide Mobile Air Conditioning Climate Protection Partnership (SAE, 1999, 2000).
Two categories of alternative refrigerant candidates have emerged for new systems: 1) transcritical carbon dioxide systems and 2) hydrocarbon or HFC-152a systems.
Highly efficient air conditioning and heating systems are particularly important to the commercial success of electric, hybrid, fuel cell, and other low-emission vehicles to help overcome the limited power of such vehicles.
Recovery and Recycle
It is estimated that recycling rates can be increased from 60% to 90% within
one to two years in developed countries (SAE, 2000). Recovery and recycling
of HFCs can reduce emissions by more than 10 kt annually (Baker, 1999). About
50% of the global fleet of HFC-134a air conditioned vehicles are in the USA
where recycling is mandatory, and 25% are in Japan, where voluntary programme
achieve a substantial recycling rate. The remainder are in Europe where recycling
ranges from zero in some countries to near 100% participation in others, and
in developing countries, where a wide range of recovery practices is found.
A UNDP survey of 1300 Brazilian garages found one-quarter of garages recycling
HFC-134a (UNDP, 1999).
The current market value of HFC-134a recovered during service or disposal in the USA more than pays for the cost of labour, equipment, and maintenance for shops servicing more than 6 vehicle air-conditioning systems per week. By 2002 to 2003 it is technically feasible to reduce system charge and leakage rates significantly. Recovery of 0.33 kg of HFC-134a will cost US$0.70 in large shops and US$1.50 in small shops. For large shops, recovery costs for improved, low-charge vehicles are estimated at less than US$3.50/tCeq. Even for small shops, the cost-effectiveness per tonne of carbon equivalent can then be calculated in the range of US$1.18-12.81/tCeq depending upon the size of the charge (EPA, 1998).
Reduced Charge and Improved Containment
By 2002 to 2003, it is technically feasible to reduce system charge and leakage
rates worldwide. It is estimated that the vehicle charge in the US can be reduced
from 0.9kg to 0.8kg and that annual vehicle leakage could be reduced from 0.07
kg/yr to 0.04kg/yr (UNEP, 1998a; Baker, 1998; Sand et al., 1997; Wertenbach
and Caesar, 1998). In Europe, refrigerant charges average about 0.7 kg per vehicle
(Clodic, 1999). For the USA it is estimated (Baker, 2000) that emissions can
be reduced from 8% to 5% per year for a 10-year reduction of 1.2 kg/vehicle
without recovery and recycling or 1.0kg with recovery and recycling. Two studies
(Harnisch and Hendriks, 2000; March, 1998) estimate that, in Europe, the cost
per vehicle to reduce leakage rates from 10% to 4%-5%/yr is only US$11-US$13.
Alternative Systems
Three authors have published estimates of the cost of emission reductions achieved
through alternative vehicle air conditioning using carbon dioxide as the refrigerant
(March, 1998; Baker, 1999, 2000; Harnisch and Hendriks, 2000). These studies
reported widely diverging results on the specific abatement costs of HFC emissions
for the use of transcritical CO2 systems (from US$90 to >US$1000/tCeq).
Differences in cost estimates can be traced back to a number of factors among
which two are most important: (1) the use of producer-costs versus consumer
costs and (2) differing assumptions about the existing degree of recovery of
HFC-134a during servicing and at the end of life. Of lesser importance were
differing assumptions on the average fluid charge of an HFC air conditioning
system, annual leakage rates, relative differential costs, and applied discount
rates. Once the results are normalized to common assumptions on the major factors,
the abatement costs differ by only a factor of two or less (see Table
A3.4).
As reported in Table A3.4, costs of avoiding HFC emissions
through alternative air conditioning systems vary between US$20 and US$2100/tCeq
depending on the emission characteristics of the reference HFC system (and on
whether consumer or producer prices are used). Consequently in countries where
systems already exist to ensure HFC recycling during servicing and at the end
of life, alternative air conditioning systems will need to exhibit significantly
reduced indirect emissions in order to be cost-effective in abating greenhouse
gas emissions.
Table A3.4: Abatement costs a of avoiding HFC emissions by using alternative systems (based on CO2 or secondary hydrocarbons) relative to different baseline HFC emission scenarios | ||||||||
Alternative system compared against current HFC-134a
systems
|
Alternative system compared against improved HFC-134a
systems with reduced leakage rate
|
|||||||
With recycling, 1.4 kg 10-year emission baselineb
(US$/tCeq) |
Without recycling, 3.2 kg 10-year emission baseline
(US$/tCeq) |
With recycling, 0.4 kg 10-year emission baselineb
(US$/tCeq) |
Without recycling, 2.0 kg 10-year emission baseline
(US$/tCeq) |
|||||
Producer cost
|
Consumer cost
|
Producer cost
|
Consumer cost
|
Producer cost
|
Consumer cost
|
Producer cost
|
Consumer cost
|
|
102-173
|
306-519
|
21-53
|
63-159
|
460-711
|
1380-2133
|
59-109
|
177-327
|
|
a Assuming:( i) equivalent
energy efficiency for conventional and alternative systems, (ii) an increase
of producer cost by US$60-90 per vehicle relative to current HFC-systems,
(iii) a discount rate of 4% per year, and (iv) a factor of 3 between consumer
cost and producer cost (Crain, 1999). b Incremental costs for the improved HFC system and for establishing and enforcing a recovery system are not included but assumed to be small compared to additional costs of alternative systems. |
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