Analysis of stratified thermal storage systems: An overview

The presence of stratification is well known to improve the performance of stratified thermal energy storage systems (STESS). The major energy and exergy methods for modeling and assessing the performance of STESS are reviewed in this presentation. Current analytical and numerical methods for modeling STESS are surveyed, with their strengths and weaknesses. An extensive survey of performance assessment methods based on energy, entropy and exergy analyses is also presented. This survey highlights entropy generation ratios, which are based on second law considerations, as effective in quantifying the improvements in STESS performances that result from the presence of stratification unlike energy-based measures. The entropy generation number, N (s) is suggested as an effective tool for future performance studies on STESS.