Liquid Metal Batteries: coupling electrochemistry, heat and mass transfer with magnetohydrodynamics

Liquid metal batteries (LMBs) are discussed as cheap stationary energy storage. Built as a stable density stratification of two liquid metals separated by a molten salt, such cells offer extreme current densities at a potentially unlimited life time. Beyond that, it is especially the low price which makes LMBs an ideal candidate for balancing highly fluctuating renewable energy sources. The efficiency of LMBs is mainly determined by two aspects. Most importantly, the electrolyte layer must be as thin as possible as it has a high ohmic resistance. Still, it needs to be thick enough to prevent a short-circuit. Secondly, efficient mass transfer needs to be ensured. Optimising an LMB means therefore understanding the interplay of thermal and solutal convection, mass transfer, electrochemistry and electrodynamically driven flow with the current distribution in the cell. The talk will start with an introduction to built-up and operation of LMBs. The different physical effects will be discussed using simulations performed in OpenFOAM. Numerical details will be provided on coupling hydro- and electrodynamics, magnetic field calculation as well as the coupling of electrochemistry with current and potential distributions.