In Thermodynamics and the design, analysis, and improvement of energy systems (ed. A.B. Duncan et al)
AES Vol. 36 pp. 241-250, 1996 - ASME Book G01022 (I.S.B.N.: 0-7918-1527-7)
LOCAL OPTIMIZATION OF ENERGY SYSTEMS
Miguel Angel Lozano, Antonio Valero and Luis Serra
Department of Mechanical Engineering – University of Zaragoza
María de Luna 3 – 50015 Zaragoza (Spain)
Many thermal systems are very complex due to the number of components and/or its strong
interdependence. This complexity makes difficult the optimization of the system design and
operation. The Exergy Cost Theory is based on concepts such as resources, structure, efficiency
and purpose (belonging to any theory of production) and on the Second Law .
This paper will show how is it possible to obtain from the theory of exergetic cost the
marginal costs (Lagrange multipliers) of local resources being consumpted by a component. This
paper also shows the advantage of the proposed Theory of Perturbations when describing the
complexity of structural interactions in a straightforward way. This theory allows to formulate
simple procedures for local optimization of components in a plant.
Finally strategies for optimization of complex systems are shown. They are based in the
sequential optimization from component to component. This clear and efficient method comes
form the fact that we have now an operative application of the thermoeconomic isolation principle.
The idea that every physical cost is due to some degradation links economics with
thermodynamics. In the field of thermoeconomic analysis of energy systems the methodologies
developed up to now (Gaggioli and El-Sayed, 1987) can be classified in two large groups,
depending on whether their main objective is (i) the optimization of the design which has been
mainly developed by Evans and followers (1983), or (ii) the allocation of costs to internal flows
The theory of exergetic cost (Valero et al., 1986) lies within the context of cost allocation.