Assessment of Modelling Approaches for Partial Phase Charges of PCMs

Abstract

Energy storage is going to play an important role in the transition to carbon-neutral energy production. Heat is the form of energy that is relatively easy to store, even over long periods of time. Despite their relatively slow take off as a thermal energy storage medium, the phase change materials (PCMs) can play an important role in the future of thermal energy storage (TES). Some PCMs exhibit behaviours that are difficult to model accurately (such as supercooling or phase change hysteresis). Computer modelling of the PCM behaviour is further complicated by the fact that the PCMs sometimes do not undergo complete phase transitions in real-life operation of TES. Three approaches to modelling of partial phase changes of a PCM, obtained from the literature, were assessed on a simple test case. The test case was a wall with a PCM layer, which was designed as transient with the adiabatic boundary condition on one side of the wall and the sine wave heat flux on the other side. The phase change hysteresis shift of 5 °C was investigated. The results obtained with the partial phase change modelling approaches varied on average by 2.8 °C and 1.84 °C for the ‘curve switch’ model and the ‘curve scale’ model (when compared to the single curve model). The increase in thermal conductivity (from 0.2 to 0.3 W m-1 K-1) led to 34.4 % reduction in size of the phase change interruption point interval.