A store (1) for thermal energy, the store comprising: a housing (5) defining an internal chamber having an inlet and an outlet; and a plurality of receptacles (7) provided within the internal chamber and spaced from one another so that heat transfer fluid can flow over and around the receptacles (7) as the fluid moves from the inlet to the outlet; wherein each said receptacle (7) defines an internal cavity (9) for the storage of phase change material (PCM) so that thermal energy can transfer between the stored PCM material and the heat transfer fluid as the fluid passes over and between the receptacles.