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

Automated summary

Thermal energy storage is an important strategy for energy saving and utilization. Latent heat storage using phase change materials has great potential for efficient heat storage and thermal management. A high energy-storage-density and power-density latent heat storage unit is developed through the compression-induced assembly of expanded graphite based stearic acid composites and macro encapsulation method using polyethylene shells. The resulting heat storage unit shows excellent performance in terms of phase change enthalpy, thermal conductivity, form-stability, and power-density. A proof-of-concept prototype of the packed-bed latent-heat-storage system demonstrates its feasibility in fast heat charging/discharging operations.