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MOTORINDIA
l
January 2012
Bus air-conditioning: Climate-friendly
refrigerants the right choice ?
As of January 1, 2011, vehicle
manufacturers must undertake to use
refrigerants with a global warming
potential (GWP) of less than 150 in
accordance with EC No. 842/2006
in the air-conditioning units in ve-
hicles approved as new types. This
also applies for all registered pas-
senger cars and light commercial
vehicles (less than 1.3 t). The bus
industry is also mentioned in this
Directive. A date for the prohibition
of R-134a has not yet been defined
but is expected any moment.
A further legal issue related to the
use of refrigerant is defined in the
Chemicals & Climate Protection Act
which states that only specialised
personnel with a personal certificate
may carry out work on systems with
fluorinated refrigerants. The com-
pany also needs to be certified.
As of 1989, the refrigerant R12
(CFC chlorofluorocarbon), which
contains chlorine and elements that
damage the ozone layer, was re-
placed in the air-conditioning units
with the chemical FC-refrigerant
R134a (tetrafluoroethane - a hydro-
carbon that contains fluorine) that is
used today. Whilst this substance is
much more environmentally-friend-
ly than normal CFC, it still has a
GWP with a factor of 1430 and was
declared to be an interim solution at
the time.
These synthetic refrigerants start
to become a problem when they
escape into the environment in the
event of accidents or during main-
tenance. Also, the vehicle air-condi-
tioning systems are not hermetically
special article
closed systems. The refrigerant es-
capes permanently during the life
cycle of the vehicle. The average
leak rate for R134a in new buses is
13.3 per cent refrigerant per year in
coaches and 13.7 per cent in urban
buses.
According to information pub-
lished by the “Deutschen Umwelth-
ilfe e.V.”, buses in Germany emit-
ted almost 100 tonnes of refrigerant
R134a in 2008. The quantity of re-
frigerant released from buses cor-
responds to 140,000 tonnes of CO2
equivalents a year. This equates to
the annual CO2 emission of 90,000
economic small passenger cars driv-
en normally.
T
here is growing awareness of the problematic effect that synthetic sub-
stances have on the earth’s atmosphere. The European Union has recog-
nised this and, for environmental reasons, has laid down strict regulations
for refrigerants used in air-conditioning units in powered vehicles in its Mobile-Air-
Conditioning Directive (MAC).
In 1993 only five per cent of all
new city buses had air-condition-
ing units. By 2008 this had risen
to 64 per cent. In 2011 all new
coaches in Germany were fitted
with air-conditioning systems.