Pilot-scale packed bed thermal energy storage system using form-stable high-density polyethylene and polyester composite

Thermal energy storage is an important component in modern energy management. This paper presents the implementation of a pilot-scale thermal energy storage system applying a novel phase change composite material comprising high-density polyethylene and polyethylene terephthalate. The composite exhibits a thermal capacity of 273 kJ/kg for discharge between 130 °C and 120 °C, primarily due to the enthalpy of solidification of high-density polyethylene. A modular thermal energy storage system is designed using the composite in a packed bed with direct contact heat transfer between the phase change material and a glycerol heat transfer fluid. This design, tailored for medium-temperature processes requiring heat below 120 °C, offers efficient heat storage, enhancing capacity and heat transfer while reducing porosity, liquid volume, cost, and heat loss. System energy storage capacity and discharge power are characterized through bulk calorimetry. Experiments demonstrate system discharge rates exceeding 70 W/kg. The media shows high stability during thermal testing. Composite deformation and potential for long-term media segregation are quantified. Future investigations are suggested to further understand the effect of geometric and thermal parameters on charging and discharging behaviors. • Form-stable PET-HDPE composite provides latent heat thermal energy storage. • Durability of polymer composite characterized by accelerated cycling and low viscosity melt proxy testing. • Packed-bed thermal storage system implemented with direct-contact heat transfer. • System provides > 272 kJ/kg heat from 130 to 120 °C at rates > 70 W/kg.