Because of the commitments in the Kyoto Protocol, hydrofluorocarbons (HFC) and perfluorocarbons (PFC) must be phased out and suitable replacements must be found. This applies also to the airconditioning systems (A/C) in passenger cars. In almost all A/C the refrigerant nowadays used is 1,1,1,2- tetrafluoroethane (R134a). In combination with the high fleet number of air-conditioned cars, and the fact that the percentage of passenger cars equipped with A/C is at 95 %, this sector is of great interest regarding potential impact reduction for ozone depleting substances (ODS), greenhouse gases, and energy consumption. In the present work, the main focus is on comparison of three assessment methods, used to evaluate the environmental impact of refrigerants used in A/C by means of partial order. The application examined in this LCA study is an A/C system as functional unit of a standard European passenger car. The technical outlay of the system is based upon the principle of liquid evaporation and vapour compression. They currently most commonly used refrigerant in A/C in passenger cars is R134a, the HFC R152a, the hydrocarbons (HC) R290 and R600a, and carbon dioxide (R744) are possible replacements. The environmental impact of dichloromethane (R30) was assessed for comparison. The hydrofluoroethers (HFE) E125, E134, E7000, E7100, and E7200 are included as well as they are of interest because of their thermodynamic properties. The A/C system is operated with respect to average German climate conditions within a 10 years lifetime of the passenger car. In general, the scope of the LCA comprises input and output of production, operation (including servicing/refilling), and disposal phase. The main focus is on energy consumption during the operation phase of the A/C system, assuming that the additional fuel consumption due to the operation of the A/C system represents the amount of energy necessary to compress the refrigerant under defined cycle conditions. Three different assessment methods were applied to the results of the life cycle inventory in order to find the least harmful refrigerant to the environment. The results of three different assessment methods, i.e. the Dutch Handbook method (CML02), Total Equivalent Wanning Impact (TEWI), and Eco-Indicator 99 (EI99) are compared by means of partial order and the software WHASSE. In A/C systems in passenger cars, the polyfluorinated dimethylethers E134 and E125 do not seem to be suitable replacements for R134a. The perfluoroalkyl-alkyl-ethers E7000, E7100, E7200, and the HC R600a and R290 have smaller environmental impact than R134a with all three assessment methods. Using the more holistic assessment methods CML02 and EI99, R744 is also ranked lower than R134a. The Spearman correlation analysis shows that there is a discrepancy of the rankings resulting from different assessment methods. Therefore, one must choose carefully the method for assessing the environmental impact of one substance.
Ranking of refrigerants by different assessment methods
Klassifizierung der Kühlmittel durch verschiedene Bewertungsmethoden
2008
9 Seiten, 3 Bilder, 3 Tabellen, 17 Quellen
Aufsatz (Konferenz)
Englisch
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