Assessing the potential of binary and ternary supercooled sugar alcohol-based PCMs as a thermal battery

Supercooled sugar-alcohol phase change materials (PCMs) can store heat with low thermal losses and release it on demand when crystallisation is triggered. This study evaluates binary and ternary sugar-alcohol PCMs consisting of erythritol (Er), xylitol (Xy), and mannitol (Man) as controllable supercooled “thermal batteries”. T-history experiments have been conducted to characterise melting behaviour, supercooling stability, and triggered cold crystallisation. Performance comparisons have been conducted using cumulative cold crystallisation enthalpy over a consistent temperature window (from the trigger temperature of 60 °C until the sample returned to 60 °C), together with the peak cold crystallisation temperature. The non-eutectic Er–Xy (75/25 wt%) demonstrated higher cumulative cold crystallisation enthalpy than the eutectic composition, with distinct differences in both peak temperature and cumulative enthalpy. The ternary Er–Xy–Man (70/20/10 wt%) produced the highest cumulative cold crystallisation enthalpy albeit at a lower peak temperature. A lumped 1D cylindrical MATLAB model was developed to simulate the thermal response of the selected supercooled PCMs in a cylindrical container and validated against experiments (RMSE 5.6–8.2 °C; MAPE 6.6–12.3%). Scale-up simulations indicate that a six-tube configuration (60 mm diameter, 1.75 m height per tube) can store approximately 5 kW h th , forming a SuperThermalBattery unit. A MATLAB–TRNSYS co-simulation with evacuated tube solar collectors suggests that solar-driven charging is feasible in hot climates such as Malaysia, while annual performance in the UK is constrained by available solar input. These results indicate that supercooled sugar-alcohol PCMs can function as short-term, solar-charged thermal batteries and motivate further evaluation at larger scale and under a wider range of operating conditions.