Thermoeconomic Optimization of a Sensible-Heat Thermal-Energy-Storage System: A Complete Storage Cycle

Abstract

An analytical model for the second-law-based thermoeconomic analysis and optimization of a sensible-heat-storage system is derived and discussed, in which the storage element is both heated and cooled by flowing streams of gases. In this analysis, monetary values are attached to the irreversible losses caused by the finite temperature difference heat transfer and pressure drop in the storage system. Important dimensionless parameters are identified and the results are presented in terms of the optimum dimensionless charging time θS,opt as a function of a dimensionless temperature difference τ, as well as the optimum number of heat transfer units NTUS,opt, as a function of the dimensionless unit cost per unit heat conductance γUA and τ of the storage systems. The systems analyzed are optimized by introducing a new performance criterion described as the cost rate number, Γ*. Several example problems are also presented and the results are compared with that obtained from Krane’s analysis to illustrate the usefulness of the present approach. The influence of important unit cost parameters on NTUS,opt and θS,opt, are also studied in somewhat more detail.