Analysis of Power Density for Phase Change Material Thermal Energy Storage Modules Based on Grid Flexibility

This study investigates the performance of a phase change material (PCM) thermal energy storage (TES) module under variable power conditions, focusing on power density and grid flexibility. A prototype employing a form-stable metallic PCM within a 15 L thermal storage module was tested under different operational scenarios, including heating, thermal insulation, and heat extraction. The heating process raised the module's temperature from 28.82°C to 600°C over 5.01 hours, with a total heat input of 9.60 kWh, achieving a heating power density of 127.67 kW/m<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup>, while the material itself exhibited a power density of 225.29 kW/m<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup>. The thermal insulation test revealed dissipation power fluctuations of 570-580 W, indicating potential heat loss due to inadequate sealing. In the heat extraction phase, the system maintained an outlet temperature of 50°C and 70°C with an airflow velocity of 2.5-5 m/s. The module's power variation ranged from 200 W to 1400 W, corresponding to a power density of 13.3-93.3 kW/m<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup>, while the material itself exhibited a power density of 23.53-164 kW/m<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup>. These results highlight the feasibility of achieving outlet temperatures exceeding 150°C, making the system suitable for industrial applications beyond the operational range of heat pumps. The findings provide insights for optimizing material selection, insulation design, and thermal energy storage modules to enhance the efficiency of PCM-based TES systems under grid flexibility conditions.