Energy Use: Exergy and Eco-Exergy

Authored by: Sven Erik Jørgensen

Encyclopedia of Environmental Management

Print publication date:  December  2012
Online publication date:  December  2012

Print ISBN: 9781439829271
eBook ISBN: 9781351235860
Adobe ISBN:


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Thermodynamic indicators are generally applicable as very holistic indicators for ecosystems, meaning that they are able to capture the system properties of ecosystems. The theoretical basis, definitions, and applicability of exergy and specific exergy both in technological and ecological context are presented. The technological exergy is a useful concept to express the efficiency of work energy use, while the eco-exergy is a very useful ecological indicator. The theoretical basis for eco-exergy leads to the following expression for calculation of the eco-exergy density for an ecosystem, Ex = ∑ i = n i = 0 β i c i which is easy to apply. The concentrations, ci , are known from measurements (observations) or from ecosystem models, while the β values for various classes of organisms are listed in a table. The β values are based on calculations of the information that the organisms embody in the genomes and used to determine the amino acid sequence in the life process–controlling enzymes. Two concrete examples of the use of eco-exergy and specific eco-exergy as ecological indicators are presented to illustrate the applicability of these holistic indicators, with particular emphasis on what they can reveal about ecosystem health.

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