Second-law-based thermoeconomic analysis and optimization of thermal-energy-storage systems.

Abstract

A closed-form model for the second-law-based thermoeconomic analysis and optimization of thermal-energy-storage systems is derived and discussed. The analytical procedure is generalized since it is applicable to all types of thermal-energy-storage systems that do not have chemical reactions. The derived procedure is applied on three types of energy-storage systems, namely: Sensibly Joulean-heated, sensible-heat, and latent-heat, thermal-energy-storage systems. In the analysis, a complete second-law derivation is given for each one of the three systems to obtain the entropy generated (or irreversible losses) in each of the storage and removal processes. Monetary values are attached to the irreversible losses caused by the finite temperature difference heat transfer and pressure drop in the storage system. The systems analyzed are optimized using a new performance criterion described as the Cost Rate Number. This number relates the cost rate of all the irreversible losses to the cost rate that is supplied to the system. The cost rate number is minimized with respect to number of transfer units, in addition to other important variables of the systems. The effect of unit cost parameters on the performance of all three types of storage systems are discussed in detail.