Thermal buckling investigation of molten salt storage tanks used in thermal energy storage systems

Molten salt thermal energy storage is a promising solution for renewable energy transition; however, safe and efficient containment of molten salts remains challenging due to their operation at high temperatures. Despite several studies conducted on the thermal and thermal-mechanical behaviour, the thermal buckling of molten salt storage tanks remains a critical issue that has not been thoroughly investigated. This study presents a numerical investigation of the thermal buckling behaviour of a commercial-scale molten salt steel tank during operation and pre-commissioning. Both global and local welding-induced imperfections in the tank floor are considered for the analysis. The effects of foundation stiffness, fabrication plate arrangement, and imperfection on the buckling response of the tank floor are evaluated. Two types of foundation models — namely, an idealized Winkler and a tensionless foundation — are investigated to assess buckling during pre-commissioning. The critical buckling temperature and post-buckling deformation shapes are analysed. The investigation indicates that buckling during operation is unlikely, provided that a minimum molten salt inventory is maintained and the tank is allowed to expand uniformly. However, during pre-commissioning, the tank floor is susceptible to buckling on weak foundations when modelled as an idealized Winkler model. For a more realistic tensionless foundation, buckling of the tank floor is observed even for relatively stiff foundations, with stiffness up to 30 MPa/m. The floor shows buckling at 75 °C on a medium-stiff soil. This buckling initiates adjacent to the edge where sharp plate corners and small plate segments are joined together.