Thermal energy store

The thermal energy store 1 comprises a vessel 2 having at least one fluid flow path 3 extending therethrough, wherein the at least one fluid flow path defines at least one cartridge aperture 5 to receive a thermal energy storage cartridge containing a heat storage material. The heat storage material may be a phase change material (PCM). The vessel may include a removable closure to prohibit access to the at least one cartridge aperture. The at least one fluid flow path may comprise a first 3a and second 3b fluid flow path that define a series of tines forming platforms 4 onto which the cartridges are located, the flow paths being used to charge and discharge the PCM contained within the cartridges. The cartridges may comprise plate shaped sealed containers having grooves that are complimentary to the tines. The thermal energy store may be used as part of an electricity generation system that generates electrical power from energy received via the thermal store.