Latent heat storage module comprising phase change material within metallic sphere

A metallic spherical thermal energy storage module 7 is filled with a phase change material 1 for use in heat transfer applications. The module 7 may comprise two identical semi-spherical metal halves 9, 10 sealed together by crimping the perimeters 11 of the two halves 9, 10. There may be provided an internal separation sheet 8 for sealing one half of the module 9, 10 following the filling of that half 9, 10 with phase change material prior to the crimping operation. A plurality 20 of modules 7 may be used in apparatus comprising chilled and/or heat rejection circuits (15, 18, figure 4), central heating circuits (figure 6), heat recovery circuits with/without combined heat and power units and solar heating systems (figure 8). The apparatus may include at least one heat exchanger. The apparatus may comprise refrigerant gases.