Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

Liquid metal batteries (LMBs) are discussed today as an economic grid-scale energy storage, as required for the deployment of fluctuating renewable energies. These batteries consist of three stably stratified liquid layers: two liquid metal electrodes are separated by a thin molten salt electrolyte, this way forming an electrochemical concentration cell. Their completely liquid interior, which is on the one hand very beneficial for the energy efficiency, also poses some major challenges on the other hand. Strong cell currents in combination with electromagnetic fields make liquid metal batteries highly susceptible to various kinds of magnetohydrodynamic instabilities. In particular, the so-called metal pad roll instability (MPRI), which can drive uncontrollable wave motions in both interfaces, was identified as a key limiting factor for the batteries' operational safety.
In this seminar talk, I will present the key results of my PhD thesis, where I was concerned with multilayer interfacial wave dynamics in cylindrical LMB models. In the fist part, I will show the results of a potential flow theory describing gravity–capillary waves in three-layer stratifications. The theory is used to classify different wave coupling states, which comprise different manifestations of the MPRI. Accompanying numerical simulations substantiate that coupling effects will be present in most future LMBs. In the second part, a multilayer sloshing experiment will be introduced, which allows to mechanically excite the same interfacial wave motions as induced by the MPRI. Different sets of experiments emphasize the crucial role of the contact line as well as of viscous damping, both having a strong impact on instability onsets of cylindrical LMBs. In the final part, I will present a new hybrid interfacial sloshing model, which accounts for viscous damping and can explain the experimentally observed resonance dynamics. As a further unexpected result, the sloshing theory predicts the formation of novel spiral wave patterns under the effect of strong damping in higher wave modes.