An Irreversibility-Based Criterion to Determine the Cost Formation of Residues in a Three-Pressure-Level Combined Cycle

Abstract

In an energy system, it is important to identify the origin of residue formation in order to implement actions to reduce their formation or to eliminate them as well as to evaluate their impact on the production costs of the system. In the exergetic cost theory, although there are several criteria to allocate the cost formation of residues to the productive components, no unique indication on the best choice has been defined yet. In this paper, the production exergy costs are determined by allocating the residue cost formation to the irreversibilities of the productive components from which they originate. This criterion, based on the Gouy–Stodola theorem, is an extension of the criterion of entropy changes, and unlike this, it avoids the existence of a negative production cost. This criterion is applied to a combined cycle of three pressure levels, and the production exergy costs are compared with the criteria of entropy changes, distributed exergy, and entropy. The results of the proposed criterion are in agreement with the compared criteria.

The Exergy Cost Theory Revisited

“…The process model can help provide methods for the first approximation to the allocation of the waste cost, but in general, the construction of waste tables is usually external to calculating production costs. In this line, several researchers have proposed different waste cost allocation methods in recent years [35][36][37][38].…”

“…By construction, all their elements are non-negatives and satisfy Equation (34). To prove that they define the FP table, we need to check that Equations (38) to (40) also satisfies Equation (33). Indeed, applying Equation ( 25) leads to L a 0 + α F Fu n = u l , and one has…”

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

“…Lugo-Mendes et al [66] use a residue cost criterion based on irreversibilities that can be conceived as an extension of the criterion of entropy changes (Option 2 [1]) because, in addition to the entropy changes, it also includes the exergy flows associated to the heat transfer through the boundaries of the energy system, and it is supported on the Gouy-Stodola theorem. Nevertheless, it avoids the existence of a negative production cost that usually happens in Option 2 and the residues costs are in direct proportion to the irreversibility or exergy destruction of the productive components.…”

“…These production exergy costs are determined by allocating the residue cost formation to the irreversibilities of the productive components from which they originate. In [66] the authors apply the methodology in a Three-Pressure-Level Combined Cycle, and the results are compared with those obtained by Option 2 [1], Option 4 [41] and Option 5 [42]. Despite the proposed criterion reaching results in agreement with the compared criteria, it does not permit to calculate the costs of internal streams for assessing the impact of the additional fuel required to compensate component malfunctions.…”

“…The methodologies proposed by [1], [41], [42], [62], [66] as well as the one presented in this work are based on the that are def ined by dif ferent cri teria. Non etheless, the biggest contribution of this work is due to the kind of diagram used and the difference concerning the residue costs reinternalization with advantage in a future application of thermoeconomic diagnosis.…”