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Auflistung nach Autor:in "Gerstmann, Silke"

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  • Konferenzbeitrag
    Hasse Diagram Technique – A Useful Tool for Life Cycle Assessment of Refrigerants
    (Environmental Informatics and Systems Research, 2007) Weckert, Monika; Restrepo, Guillermo; Gerstmann, Silke; Frank, Hartmut
    Destruction of the polar ozone layer and global climate change are proven consequences of various man-made volatile compounds of which substances used for air-conditioning systems or refrigeration units are important contributors. The Montreal and Kyoto Protocol regulate the phase-out of ozone-depleting substances and the reduction of greenhouse gas emissions. In the present work, the main focus is laid on emissions from air-conditioning (A/C) systems depending on the used refrigerants, and the comparison of life cycle assessment results by means of the Hasse Diagram Technique. Five refrigerants were ranked according to three parameters. Two Hasse Diagrams were drawn; one using the energy consumption during refrigerant production and compression of the refrigerants during operation of the A/C system, the other one additionally including the direct emissions during the total life cycle of the A/C system. According to this study, the refrigerants R152a and R290 have the smallest environmental impact. The two Hasse Diagrams clearly show that direct emissions of refrigerants are crucial within the life cycle of an A/C system. Due to its small GWP100, carbon dioxide (R744) has a better direct emission balance than hydrofluorocarbons and hydrocarbons. Next to energy and emissions values, other properties (e.g. toxicology, safety, energy efficiency…) are of importance when deciding which refrigerant can be recommended as substitute. But the more parameters are included, the more likely is it that incomparabilities in the Hasse Diagrams occur. Thus, when applying the Hasse Diagram Technique to LCA, not more than three parameters should be considered. Further studies are planned to examine the relative importance with respect to energy efficiency, environmental and human health of the various properties.
  • Konferenzbeitrag
    Ranking of Refrigerants by Different Assessment Methods
    (Environmental Informatics and Industrial Ecology, 2008) Weckert, Monika; Restrepo, Guillermo; Gerstmann, Silke; Frank, Hartmut
  • Konferenzbeitrag
    Refrigerants ranked by Partial Order Theory
    (Environmental Informatics and Systems Research, 2007) Restrepo, Guillermo; Weckert, Monika; Brüggemann, Rainer; Gerstmann, Silke; Frank, Hartmut
    Forty refrigerants used in the past, used presently, and some proposed substitutes, were studied in respect to their ozone depletion potential, global warming potential, and atmospheric life times. They were ranked using the Hasse diagram technique, a mathematical method which permits to draw diagrams representing order relations among chemicals. The refrigerants were divided into 13 chemical classes (subsets) of which the most prominent ones are the chlorofluorocarbons (CFC), hydrofluorocarbons, hydrochlorofluorocarbons and hydrofluoroethers. Order relations among these subsets were calculated applying dominance and separability degrees. The dominance degree is a measure indicating the extent to which descriptors of members of one subset are higher than those of members of other subsets; the separability degree is a measure for the incomparability or lack of order relations between elements of two subsets. By application of these measures to the 13 chemical subsets it was found that more than half of the order relations among them are complete dominances; this means a high degree of comparability among subsets permitting to find the ones most problematic in environmental terms. This is the case for the CFC and for some of the hydrofluoroethers.