Performance comparison of a group of thermal conductivity enhancement methodology in phase change material for thermal storage application

Phase change materials (PCM) are able to store thermal energy when becoming liquids and to release it when freezing. Recently the use of PCM materials for thermal energy storage (TES) at high temperature for Concentrated Solar Power (CSP) technology has been widely studied. One of the main investigated problems is the improvement of their low thermal conductivity. This paper looks at the current state of research in the particular field of thermal conductivity enhancement (TCE) mechanisms of PCM to be used as TES. This work considers a numerical approach to evaluate the performance of a group of TCE solutions composed by particular configurations of two of the principal TCE systems found on the literature: finned pipes and conductive foams. The cases are compared against a single PCM case, used as reference. Three different grades of graphite foams have been studied, presenting a charge time 100 times lower than the reference case for the same capacity. For fins two materials are analyzed: carbon steel and aluminum. The charge times of fin cases are from 3 to 15 times faster, depending on the amount and type of material employed. The internal mechanisms are analyzed to understand the results and locate possible improvement.