Avaliação dos Modelos Termodinâmicos e Abordagem da Alocação de Co2 em Termoeconomia

Abstract

Thermoeconomics combines economics and thermodynamics to provide information not available inconventional energy and economic analysis. A group of specialists interested in the discipline (C. Frangopoulos, G. Tsatsaronis, A. Valero and M. von Spakovsky) decided in 1990 to compare their methodologies in solvinga predefined problem (the CGAM problem), in which the letters stand for the first names of these experts. Over the years some comparison studies have been made, but the methodologiesalsosuffered many alterations, mainly with regard to rational treatment of waste and dissipative equipment. For thermoeconomics modeling one of the key points is the thermodynamic model that should be adopted, because different thermodynamic models can be used in representing the thermal system depending on the accuracy required.Different models lead to different results in thermoeconomics. At this point, three questions arise: How different can the resultsbe? Are these simplifications reasonable? Is it worth using such a complex model? The way we define the productive structure is a key point in thermoeconomics. Generally, exergy and/or monetary costs of the external resources are distributed to the final products. However, environmental consideration can be incorporated to the models to calculate the environmental costs of the final products, such as specific CO2 emission of each final product. This work shows a triple goal. First, show that today thermoeconomic methodologies are well defined and achieved a certain degree of unification. The small differences are due to different levelsof accuracy applied.Exergy can be optionally disaggregated in some of them. Second, compare four thermodynamic models in a gas turbine cogeneration system: air-standard model, cold air-standard model, CGAM model and complete combustion with excess air in order to emphasize how these hypothesisinfluence the thermoeconomics results, at least, adapt the thermoeconomic models to allocate de overall CO2 emission,or any other pollutant, to the final products (heat and power) of a cogeneration system.