Comparison of LCA with METEOR results

In the previous chapter, results of LCA literature were compared with those of the present LCA study considering mobile A/C application. A main aim of this work was to check if results derived from mathematical models using refrigerant intrinsic properties are similar compared to those of LCA considering different technical applications. For comparison with LCA results the average ranks of METEOR calculation were used (Table 30). According to METEOR results, R143a has the greatest impact on the environment, followed by R22, R32, R125, R410A, and R744. The smallest impact has E7200 and then R717, R30, R600a, and R152a. R1270, R290, R134a, and R407C have medium environmental impacts.

In the present study, some agreements between the LCA study on mobile A/C systems and METEOR results could be found. E7200 has a smaller environmental impact than R30 and R134a. R600a is ranked lower than R744 and R134a. R290 has a lesser impact than R744, and R134a has a greater impact than R152a. Those compliances are due for all three assessment methods. For EI99 and AV (CML02), some additional agreements with METEOR results are found: R30 is ranked lower than R134a, and R600a is ranked lower than R152a.

Beside those compliances, some differences occur. In METEOR, R134a is ranked lower than R290 and R744. This is not the case for the rankings of the present LCA study. Furthermore, R30 is not ranked higher than R744, R152a, R600a, and R290. In METEOR, R600a does not have a greater environmental impact than R290. The dominance of R152a over R290 could not be confirmed by METEOR results.

Table 30: Averaged ranks derived from METEOR calculation

Yanagitani & Kawahara (2000) assessed the environmental impact of R22 and R410A in A/C systems with the performance of 4 kW. R410A showed in all studied impact categories a lower environmental impact than R22. This matches the results from METEOR.

For the application of some refrigerants in residential A/C systems and heat pumps, Arthur D. Little, Inc. (2002) reported a ranking that gives greatest environmental impact to R22, followed by R407C and R410A, while R290 and R744 are the two least problematic refrigerants. The METEOR calculation compiles with the dominance of R22 over the four mentioned refrigerants, but otherwise shows a ranking of R407C that is lower than the other four refrigerants. Under METEOR, R410A is ranked higher than R290 and R744, and R744 is ranked higher than R290.

Similar results occur when regarding commercial A/C systems (Little 2002). R22 is ranked highest of the therein studied refrigerants. But the second highest rank of R407C does not match METEOR results which place this refrigerant at the lowest rank. Furthermore, the dominance of R134a over R290 and R744 in Little’s report differs with the results of METEOR which places R134a below those two refrigerants.

Another technical application is supermarkt refrigeration in the low and medium temperature range. Bovea et al. (2007) used EI99 for assessing the environmental impact of refrigerants in a standard Euopean supermarket (2 000 m²) with a cooling duty of 130 kW over a period of 15 years. Considering a medium temperature cooling system with direct expansion, Bovea et al. (2007) identified R744 as the refrigerant with the greatest impact followed by R134a. R22 and R410A are the two refrigerants with the lowest impact. METEOR results confirm the dominance of R744 over R134a, but rank R22 and R410A higher than R744 and R134a. In a secondary loop system under medium temperature range, Bovea et al. (2007) ranks R134a highest, followed by R717, R410A, and R22. Again, METEOR does not give the same results.

Alone, that R717 is ranked lower than R134a is a common result. Bovea et al. (2007) were further considering low temperature systems. While METEOR ranks R744 higher than R407C, Bovea et al. (2007) came to the contrary result.

Zogg (1999) compared the environmental impact of natural refrigerants in heat pumps with those of refrigerant presently used. He showed that for heat pumps under comparable performance the natural refrigerants (R290, R744) have lower impact in the categories “Climate change”, “Stratospheric ozone depletion”, and “Terrestrial ecotoxicity” than conventionally used ones (R22, R134a, R407C). Considering the

Refrigerant Average

impact categories “Non-renewable energy”, “Acidification”, “Summer smog”, “Aquatic ecotoxicity”, and “Radioactivity”, the studied refrigerants do not show great differences.

METEOR ranks R744 and R290 higher than R134a and R407C but lower than R22.

Thus, results from Zogg (1999) are not confirmed.

The research center for refrigeration technique and heat pumps (FKW) did a study on the replacement of R22 in existing refrigeration and A/C systems (FKW 2000). They calculated the annual TEWI for seven refrigerant including R22, R134a, R290, R407C, R410A, R717, and R1270. The systems investigated in the FKW study comprise supermarket cooling facilities in the low and medium temperature range, A/C in buildings, transport cooling in the low temperature range, and air/water heat pumps.

Comparing the results of METEOR with those of FKW (2000), FKW always gave greatest environmental impact to R410A which is ranked below R22 in METEOR. In the FKW study, R717 has the smallest environmental impact in the applications supermarket refrigeration system (medium temperature), A/C system for buildings, and air/water heat pump matching the results from METEOR where it has the lowest rank of the refrigerants included in the FKW study. FKW assign in all mentioned applications a high rank to R407C which is ranked low in METEOR. Only in air/water heat pumps, R290 is assessed a greater environmental impact than R134a which is in accordance with METEOR results. However, R1270 is ranked lower than R134a in all applications except air/water heat pumps. This is in contrast to the METEOR ranking.

Frischknecht (1999a, 1999b) assessed and compared the application of natural and synthetic refrigerants finding out that the natural refrigerants (R290, R717, R744) have a smaller impact to the categories “Stratospheric ozone depletion”, “Climate change”, and

“Terrestrial ecotoxicology” than the halogenated refrigerants included in his study. R290 has a slightly greater contribution to the category “Photo-oxidant formation” than synthetic refigerants (R134a, R407C, R410A, R22). In the category “Acidification”, R717 shows similar contributions compared with the HFCs (R134a, R407C, R410A).

Those results are not mirrored in METEOR where R744 and R290 show greater environmental impact than R134a and R407C, and where R22 is ranked highest and R717 lowest.

Overall, METEOR does not agree with the results from LCA. This phenomenon is not alone due to the fact that even different LCA studies show contradicting results depending on the different applications and conditions.