High-power-density packed-bed thermal energy storage using form-stable expanded graphite-based phase change composite

Thermal energy storage is highlighted as a crucial strategy for energy saving and utilization, in which domain, latent heat storage using phase change materials has gained great potential for efficient heat storage and thermal management applications. A strategy for developing high energy-storage-density and power-density latent heat storage units, through the compression-induced assembly of expanded graphite based stearic acid composites and the macro encapsulation method by using polyethylene shells, is demonstrated. The fabricated composite shows a satisfactory phase change enthalpy of 161.24 +/- 0.5 J g-1, and enhances thermal conductivity to 13.4 +/- 0.8 W m-1 K-1. The resulting heat storage unit also exhibits form-stable, leakage-proof, good homogeneity, and high-power-density behaviors. A 0.462 kWh proof-of-concept prototype of the packed-bed latent-heat-storage system by using 492 heat storage units has demonstrated its feasibility in fast heat charging/discharging operations. The outlet air temperature in the discharging process can maintain above 30 degrees C for over 1.74 h with a heat storage utilization efficiency of 90.3 +/- 6.1% and an effective discharging efficiency of 93.5 +/- 9.4%, under a volumetric flow rate of 30 m3 h-1 and heat storage temperature of 27-86 degrees C. The maximum and average power density, and effective energy density are obtained as 20.7 +/- 1.6 kW m- 3, 14.2 +/- 0.9 kW m- 3, 24.8 +/- 2.5 kWh