Assessment of phase change materials for thermal energy storage in battery systems for heavy-duty vehicle applications

• N-octadecane was identified as a promising PCM for battery thermal management. • Slower melting at the bottom of the TES due to reduced heat transfer under Al fins. • Higher HTF flow rate slightly improves thermal power ratio (∼5%) with minimal timing impact. • PCM integration raised gravimetric specific power to 0.056 kW kg −1 , 3.5 times the baseline. • Volumetric specific power increased 6-fold (68 kW m −3 ) over the baseline. Thermal management plays a crucial role in ensuring performance, safety, and durability in heavy-duty vehicles (HDVs), particularly under demanding operating conditions. This study investigates the use of phase change materials (PCMs) for passive thermal control, focusing on the thermal characterization and performance evaluation of commercial PCMs for battery thermal management systems (BTMS). Differential scanning calorimetry (DSC) identified n-octadecane as the most promising candidate, with a melting range of 25–32 °C, a latent heat of fusion of 222.2 J g −1 , and good thermal stability. Experimental tests in a dedicated thermal energy storage (TES) system examined the charging and discharging behaviour of n-octadecane under varying heat transfer fluid (HTF) flow rates. The heat transfer was conduction-dominated in the solid state and convection-enhanced in the liquid state. Increasing the heat transfer fluid (HTF) flow rate had limited influence on charging/discharging time but improved thermal power ratio of the TES to 56 at 3 L min −1 , representing a 3.5-fold improvement over the baseline configuration without PCM. Experimental results highlighted that incorporating PCM into the TES system increased the gravimetric specific power to 0.056 kW kg −1 – 3.5 times higher than the baseline configuration without PCM (0.016 kW kg −1 ). Additionally, the volumetric specific power reached approximately 68 kW m −3 , a sixfold enhancement compared to the baseline. These findings support the design of modular PCM-integrated TES systems as scalable solutions for HDV battery pack cooling or cabin thermal management.