Abstract: A thermal storage facility stores thermal energy at elevated temperature. The facility includes an enclosure for retaining a thermal storage medium; primary heat transfer surfaces for transferring heat from a circulating heat transfer fluid; and secondary heat transfer surfaces for transferring heat from the thermal storage medium to steam pipes associated with a power generation facility. The thermal storage medium is a metallic phase change material, preferably having a melting temperature above 500° C., interposed between the primary heat transfer surfaces and the secondary heat transfer surfaces. Solar power installations can incorporate one or more of the thermal storage facilities.