Erythritol as Phase Change Materials for High Temperature Latent Energy Storages

Latent Heat Thermal Energy Storage (LHTES) systems exploit the high latent heat of fusion of Phase Change Materials (PCMs), allowing them to store significantly more energy per unit volume compared to traditional sensible heat storage methods like water tanks and to transfer heat at an almost constant temperature. Among the advantages of LHTESs is their ability to work at different thermal levels, ensuring great versatility and promoting the efficiency of the systems they are part of. On the other hand, it is well known that they generally suffer from low thermal conductivity. This work was born to investigate how to enhance the thermal conductivity of a PCM that can work at high temperatures but is also eco-friendly and sustainable. Indeed, it is not taken for granted that all materials have the same response to the same enhancing techniques and working conditions. The results serve to promote the knowledge of such materials to potentially apply to the European project LIFE ITS4ZEB that aims to address these limitations and unlock the full potential of LHTESs in residential buildings. Erythritol, a natural polyol with a melting point of 118–120 C, was analyzed. The research aims to evaluate the contribution of three different three-dimensional geometries (with periodicities of 10, 20, and 40 mm), fabricated via additive manufacturing with AlSi10Mg 0403 aluminum alloy on the charging and discharging performance of a reference latent heat storage system. All samples contain an identical quantity of aluminum and PCM (60 g), ensuring that geometry remains the sole variable, so as to study the sensitivity of this material to the enhancement geometry. The samples were experimentally tested by analyzing the temperature field during the charging (i.e., heating and melting) process, obtained by electrical heating ( where six heat fluxes corresponding to 30, 40, 50, 60, and 70 W were applied) and the discharging (i.e., solidification and cooling) process, where the heat was only rejected by natural convection with ambient still air. Comparing the results obtained using the three 3D periodic structures and an identical sample filled only with the same amount of PCM (no 3D structure inside), it can be concluded that when structures are used, there is a reduction in charging and discharging time, and a lower heater temperature is reached compared to the case where structures are not used. Then, by comparing the three structures it was observed that unlike other materials, no significant difference was detected in the total charging and discharging time as a function of the different geometries used and that only at high powers, there is a decrease in the temperature of the heater when using the structure with a 10 mm periodicity compared to the 40 mm one. It can be concluded that erythritol is a material that behaves differently from others studied in the past. This opens up the need for further studies to understand the reasons for these results and the mechanisms that can be exploited to obtain an optimization of an LHTES based on erythritol.