Extended exergy

Sciubba (2003) proposed an approach called the extended exergy accounting (EEA), which calculates the real, resource-based value of a commodity product. The time span of EEA is the whole life of a plant. The EEA includes the exergetics flow sheets for non-energetic costs of labor and environmental remediation expenditures, and hence uses extended exergetic content. It also defines the criterion for an optimum process or operation (Sciubba, 2003). 

Including an ecovector to account for the exergoeconomic costs or environmental impact can extend the thermoeconomic approach. An ecovector is a set of environmental burdens of an operation, and can be associated with input flows it includes information about natural resources, the exergy of these resources, and monetary costs. The external environmental costs associated with the environmental burdens may also be added into the ecovector. Extended exergy accounting includes the exergetics flowcharts for nonenergetic costs of labor and environmental remediation expenditures. 

Generally, the criteria used in comparing the three electricity-generating systems are complex and difficult to evaluate and sometimes contradictory (e.g. safety sometimes means more expensive). More complex sustainability criteria such as extended exergy accounting or life cycle analysis [13] should be applied for more exact comparisons for all considered systems. 

One year before Ayres publications [7,8], Cornelissen [9] completed his PhD dissertation in which he had combined life cycle analysis with exergy analysis. He called this extension of LCA exergetic life cycle analysis. He explained that ELCA should be part of every LCA because the loss via dissipation of exergy is one of the most important parameters to properly assess a process and measure the depletion of natural resources. Cornelissen even went one step further and extended ELCA to what he called zero-emission ELCA. In this extension of ELCA, the exergy required for the abatement of emissions, that is, the removal and reuse of environmentally friendly storage of emissions, is accounted for. Cornelissen illustrated his ideas with examples of... 

Next, Cornelissen extended the LCA study to include the effect of depletion of natural resources making use of ELCA, the exergetic life cycle assessment. In this analysis a full mass and energy balance was made, that is, a first law analysis. Exergy values for all mass and energy streams were included in accordance with the Tables 6.1, 6.2, 6.3, 7.1, 7.2, 7.3 and 7.4 in Chapters 6 and 7. This analysis clearly showed where work was available in inputs and outputs and where it was lost. He could show that the cup scored less favorable than the mug in terms of depletion of natural resources (817 MJ vs. 442 MJ). 

The term exergy will be used here and it will be extended to include all the maximum obtainable work associated with different forms of energy (thermal, electrical, etc.). For other related terms that are used in the literature, see Kenney (p.22). For the case of a closed system, see Problem 5.57. 

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