Methods to Characterize the Thermal Stratification in Thermal Energy Storages

Abstract

A primary objective in creating a stratified thermal storage is to maintain the thermodynamic quality of energy, so thermally stratified energy can be extracted at temperatures required for target activities. The separation of the thermal energy in heat stores to layers with different temperatures, i.e., the thermal stratification is a key factor in achieving this objective. This paper introduces different methods that have been proposed to characterize the thermal stratification in heat stores. Specifically, this paper focuses on the methods that can be used to determine the ability of heat stores to promote and maintain stratification during the process of charging, storing and discharging. In addition, based on methods using thermal stratification indices, the degrees of stratification of stored energy in Lyckebo rock cavern in Sweden were compared and the applicability of the methods was investigated.

Temperature stratification using an air-cooled heat pump system with a mixing valve

“…Thermal stratification in thermal storage tanks has been evaluated by various methods, including graphical methods, the thermal stratification index, the energy approach based on the laws of thermodynamics, the exergy approach, the thermocline gradient method, and combinations of methods. 22–27…”

“…Thermal stratification in thermal storage tanks has been evaluated by various methods, including graphical methods, the thermal stratification index, the energy approach based on the laws of thermodynamics, the exergy approach, the thermocline gradient method, and combinations of methods. [22][23][24][25][26][27] In this study, the degree of stratification was quantified by the stratification coefficient ST and stratification index R TS , given by equations ( 2) and (3), respectively. Both measures are obtained by the meansquare deviation method.…”

The effect of manifold in liquid storage tank applied to solar combisystem

“…The degree of stratification can be expressed in various ways. In this study, the manifold's stratification performance is quantified using following equations for the stratification coefficient, ST , and stratification ratio, TS R , originally proposed by Wu and Bannerrot based on mean square deviation method [15].…”

The Effect of Variable Flow Rate Control and Variable Position Control on Seasonal Solar Thermal Energy Storage Tank

“…성층화가 잘 유지되면 축열조의 가용에너지의 증가로 이어지며, 성층화 유지 정도를 표현하는 방법은 다양 하게 제시되었는데, (5) 본 연구에서는 Wu and Bannerot의 평균제곱편차법(mean square deviation method)…”