Hybrid energy-temperature method (HETM): A low-cost apparatus and reliable method for estimating the thermal capacity of solid-liquid phase change material for heat storage system.

Estimating the total thermal capacity for phase change material (PCM) as heat storage material is extremely important to set the proper operational parameter of the latent storage tank (LST) unit. However, estimating the total thermal capacity for solid-liquid PCM is relatively complex due to temperature-dependent properties for each phase. Thus, predicting the state of charge (SoC) indicator for the LST unit is technically complex. The common approach is taken by estimating the heat of fusion during the melting process and monitoring the working fluid temperature, which makes the SoC estimation less accurate. The present project proposes a reliable method with an affordable apparatus to estimate the total thermal capacity simultaneously based on the temperature of low-temperature PCM. Moreover, sensible heating during phase transition is also estimated precisely based on the energy balance at a given temperature. The developed apparatus employs widely available components at an affordable cost which is possible for further customization. Validation and characterization are done comprehensibly by comparing the measurement from differential scanning calorimetry and previous studies. The results indicate a suitable estimation for estimating the solid-liquid heat capacity, including partial heat capacity and latent heat of fusion.