Fig. 1

Statistics of papers related to heat storage technology (source: China National Knowledge Infrastructure)"

Fig. 2

Packed-bed latent thermal energy storage structure[10]"

Table 1

Optimal design of storage tank geometry"

Fig. 3

Scheme of the pilot-scale thermal storage configuration and experimental setup, truncated cone shape is immersed in the ground with thermocouples at different vertical positions inside the packed bed[38] (unit: mm)"

Fig. 4

Schematic illustrations of the composite phase change materials based packed bed thermal energy storage system (a) 3D view; (b) cross-section view; (c) and (d) geometrical dimensions[37] (unit: mm)"

Fig. 5

CAD design of shell of high temperature packed bed heat accumulator, including main measuring unit, inner conduit[41]"

Fig. 6

Implantation of the thermocouples in the gravel (left, red) and in the oil (left, blue). Cross-section of the storage tank illustrating the temperature measurement planes (middle). Each plane contains rock and oil TC following implantation presented on the left. Storage tank before insulation (right)[46]"

Fig. 7

Scheme of a discharge process in a dual-media storage showing the temperature distribution in axial direction in the tank (x) and intra-particle radial direction (y), red: high temperature, blue: low temperature[53]"

Table 2

Selection of heat transfer fluids in different literatures"

Fig. 8

Different geometry type of capsules (a) cuboid[37]; (b) sphere[62]; (c) cylinder[61]"

Fig. 9

Phase change material capsule with hollow channel and common phase change material capsule (a) Appearance view; (b) Sectional view[58]"

Fig. 10

The evolution of capsule from sphere to oval[75]"

Table 3

Optimal design of geometric shape of heat storage unit"

Fig. 11

Schematic illustration of the PBTES system (a); the computational domains of the PBTES system (b); and the PCM capsule (c)[28]"

Fig. 12

Temperature distribution and liquid fraction distribution at 450 min at different mass flow rates under unstable-state inlet temperature conditions[31]"

Fig. 13

The photograph of experimental the solar air heater with latent storage collector[93]"

Fig. 14

Experimental set-up of the solar air heater with latent storage energy on two beds[94]"