Energy in form of heat is transferred to the Thermal Battery using a heat transfer fluid (HTF). The HTF can in principle be any fluid with adequate heat transfer properties. In most cases this is either thermal oil or water/steam.
Heat from the HTF is transferred to the solid-state storage material HEATCRETE® via cast in “U-shaped” carbon steel heat exchanger tubes. There is no direct contact between the heat transfer fluid and HEATCRETE®; the heat transfer occurs through the heat exchanger steel tubes only. The thermal storage element design using U-tubes ensures that thermal stresses in the axial direction are minimized.
The thermal elements also include a steel casing which has three functions; being a permanent casting form, an external reinforcement reducing the risk of spalling or cracking, and HTF containment (in the very unlikely case of HTF leakage inside the element).
