September 2001
Emission of Refrigerant R-134a from Mobile Air-Conditioning Systems
Report on the Umweltbundesamt (German Federal Environmental Agency)
FKZ 360 09 006
Author: Dr. Winfried Schwarz
The specific approach of this study is the ex post evaluating data records of refrigerant losses of passenger cars actually driven on roads. Overall R-134a emissions are broken down into three types: Normal (bit by bit release through seals), irregular (abrupt, in case of accidents, stone hits etc), disposal emissions (End-of-life sucking out not occurring).
Based on 1000 A/C units opened and recorded by 9 garages in 2000 (three different German car makes), the rate of normal loss is assessed at 6.3 % per year (25% tolerance band) over the first seven years of ex work A/C systems' use phase. Normal loss is considered any refrigerant deficiency of about 40 % compared to the first fill. The losses below 40 % as recorded by the garages are taken as an unintentional sample survey of the normal emissions. The basic assumption is that a 40 % refrigerant loss still allows the A/C system to work just properly.
Irregular losses are all the losses over 40 %. They are mostly caused by external events like accidents, stone hits and suchlike. Therefore the most defective single circuit component to replace is by far the condenser. The rate of irregular emissions amounts to almost 2 % per year (347 kg from all the 21,300 once a year inspected cars equipped with an R-134a ex-work A/C system).
Future disposal emissions are estimated at 2 %. This is why the assumed 25 % one-off disposal emissions are split into 12-13 usage years of the A/C system.
Thus, the overall emissions range around 10 %/yr. This rate is equivalent to a loss of roughly 88 grams per year and car (average first fill of 0.850 kg).
Keywords: car air-conditioning; mobile air-conditioning; passenger car AC systems; MAC systems; R-134a; refrigerant emissions; emission rate; refrigerant loss; R 134a.
