The rate-dependent performance and optimization of stratified thermal energy storage devices

Thermal energy storage devices are critically important components in systems for which either the instantaneous energy demand exceeds the capacity of an associated energy conversion device or for which an instantaneous energy demand may not coincide with energy supply. Stratified thermal storage is widely used due to its simplicity and cost-effectiveness. In stratified thermal storage systems, the transfer of energy to and from the storage device is accomplished through displacement of the stored fluid volume. The efficiency of the displacement process therefore depends on the extent of the thermal mixing between the hot and cold fluid volumes present in the storage vessel at any particular instant --Introduction, page 1