The Exergy Cost Theory Revisited

Abstract

This paper reviews the fundamentals of the Exergy Cost Theory, an energy cost accounting methodology to evaluate the physical costs of products of energy systems and their associated waste. Besides, a mathematical and computationally approach is presented, which will allow the practitioner to carry out studies on production systems regardless of their structural complexity. The exergy cost theory was proposed in 1986 by Valero et al. in their “General theory of exergy savings”. It has been recognized as a powerful tool in the analysis of energy systems and has been applied to the evaluation of energy saving alternatives, local optimisation, thermoeconomic diagnosis, or industrial symbiosis. The waste cost formation process is presented from a thermodynamic perspective rather than the economist’s approach. It is proposed to consider waste as external irreversibilities occurring in plant processes. A new concept, called irreversibility carrier, is introduced, which will allow the identification of the origin, transfer, partial recovery, and disposal of waste.

Thermoeconomic Diagnosis of the Sequential Combustion Gas Turbine ABB/Alstom GT24

“…The exergoeconomic cost of a residue disposed into the environment by a dissipative component is conformed by its formation cost, which is the cost of the exergy flow serving as a resource to the dissipative component (Π f r ) (formed in the productive components system), cost of additional exergy resources used for its elimination (Π a r ), and the maintenance and operation non-exergy costs (Z r ) [3,20], which can be expressed as follows:…”

“…This increase in residue generation was 51.30%, while the increase in the flow of irreversibility of the system components was 48.70% (1.97 MW). By decomposing the additional resource consumption using the fuel impact formula given by Equation ( 23) [20], we could identify that the compressor and the low-pressure turbine presented the highest increases in unit exergy costs, owing to the presence of the anomaly, which was captured using the following equation: [ t * p κ (Δ⟨KP⟩ + Δ⟨KP⟩)]P(x0).…”

“…It is well known that the more advanced a production process is, the higher the cost of irreversibilities and, therefore, the greater its impact on fuel consumption. The degradation of one component forces the others to adapt their performance to the new operating By decomposing the additional resource consumption using the fuel impact formula given by Equation ( 23) [20], we could identify that the compressor and the low-pressure turbine presented the highest increases in unit exergy costs, owing to the presence of the anomaly, which was captured using the following equation: [ t κ * p (∆ KP + ∆ KP )]P(x 0 ). The cost of the malfunction in the compressor represented 49.52%, while that of the LPT represented 47.68%, of the total impact on the fuel (4.05 MW).…”

“…Valero et al [13,20] developed thermoeconomic methodologies that include the formation processes of both the functional product and the residue in the accounting of the costs of internal flows in a system, along with the costs of the product and residue, and applied the distributed exergy criterion to attribute the cost of the residue to the productive components. This contribution has been used to study the production and formation costs of residues from energy systems, with respect to combined cycles [14,18], heating and cooling systems [8], and aviation [19], among others.…”

On the Allocation of Residues Cost using Conventional and Comprehensive Thermoeconomic Diagrams

“…Finally, in 2021 Torres and Valero [68] revisited the ECT aiming to improve the analyses of the physical costs of products and their associated waste in energy systems.…”