Methods to determine stratification efficiency of thermal energy storage processes–Review and theoretical comparison

Michel Haller, Chynthia Cruickshank, Wolfgang Streicher, Stephen J. Harrison, Elsa Andersen, Simon Furbo

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

This paper reviews different methods that have been proposed to characterize thermal stratification in energy storages from a theoretical point of view. Specifically, this paper focuses on the methods that can be used to determine the ability of a storage to promote and maintain stratification during charging, storing and discharging, and represent this ability with a single numerical value in terms of a stratification efficiency for a given experiment or under given boundary conditions. Existing methods for calculating stratification efficiencies have been applied to hypothetical storage processes of charging, discharging and storing, and compared with the rate of entropy production caused by mixing calculated for the same experiments. The results depict that only one of the applied methods is in qualitative agreement with the rate of entropy production, however, none of the applied methods is in agreement with the rate of entropy production and also able to distinguish between the entropy production caused by mixing and the entropy changes due to heat losses.
Original languageEnglish
JournalSolar Energy
Volume83
Issue number10
Pages (from-to)1847-1860
ISSN0038-092X
DOIs
Publication statusPublished - 2009

Keywords

  • thermal energy storage
  • thermocline
  • solar heating systems
  • thermal stratification

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