A thermal storage apparatus (20) is provided including a housing (30) and a plurality of elongated sealed containers (60) each containing phase charge materials and each preferably having corrugations (78) on their exterior surfaces. Advantageously, containers (60) may be stacked in an array in such a way as to allow for flow of a heat exchange fluid therebetween, the flow of the heat exchange fluid being regulated by the expansion and contraction of the containers (60).
