Tucs, Andrejs (2018) Renewable energy supply and storage: liquid metal battery stability. PhD thesis, University of Greenwich.

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Abstract

Liquid metal batteries (LMBs) offer a new opportunity for large-scale electrical energy storage. The three liquid layer self-segregated structure of the battery provides a number of advantages in comparison to classical batteries: fast kinetics, long lifetime, large current densities, easy recycling. Liquid metal batteries bear a close similarity to aluminium electrolysis cells.

In this work the mathematical model for three density-stratified electrically conducting liquid layers is developed starting with the full 3D formulation, afterwards introducing the shallow layer approximation in order to account for specific MHD effects during periods of battery charge/discharge.

The linear stability model for the interface wave analysis is developed and applied to study the multiple mode interaction. It is found that for the selection of liquid materials most suitable for practical implementation, the interface between the lower (heavy) metal and the electrolyte is significantly more stable than the interface between the electrolyte and the top (lighter) metal. The simplified 2-layer approximation is sufficient in the most of the considered cases for stability prediction of the batteries.

An analytical stability criterion including the dissipation rate is derived for different interaction cases accounting for the cell aspect ratio, the liquid layer electrical conductivities and thicknesses. The criterion is equally applicable to the aluminium electrolysis cells.

A fully coupled 3-layer numerical model based on the spectral function representation has been developed. It is well suited for analysis of the following situations: interaction of the background melt flow and the interface deformations, for the spatially complex, time-dependent distribution of the base electric current and the magnetic field. It was found that for the case when the density difference at the upper interface is much smaller than the density difference at the lower interface, only the upper interface is significantly deformed in the course of the perturbation growth. The instability onset matches very well with the linear stability model results both for the 2-layer and 3-layer models. This behaviour is similar to the aluminium electrolysis cells. In the case where the density differences at the two interfaces are comparable, both interfaces are significantly deformed, and the behaviour of the system is very different from that of a Hall-Heroult cell. The interfacial waves at the top and bottom interfaces can be coupled either symmetrically or antisymmetrically depending on the initial conditions. The presence of the second deformable interface has a stabilizing effect.

The study covers two LMB design cases for a possible practical implementation: the single collector cell, and the multiple collector cell. The numerical model demonstrates that it is possible to design a stable to dynamic perturbations operating cell if using an optimized bus bar configuration.

Item Type:	Thesis (PhD)
Uncontrolled Keywords:	Renewable energy; liquid metal batteries; energy storage; numerical modelling;
Subjects:	Q Science > QA Mathematics T Technology > TJ Mechanical engineering and machinery
Faculty / School / Research Centre / Research Group:	Faculty of Engineering & Science > Centre for Numerical Modelling & Process Analysis (CNMPA) > Computational Science & Engineering Group (CSEG) Faculty of Engineering & Science > School of Computing & Mathematical Sciences (CMS) Faculty of Engineering & Science
Last Modified:	04 Mar 2022 13:06
URI:	http://gala.gre.ac.uk/id/eprint/23654

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