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Electric fields offer an easy means to manipulate liquid metal droplets. Now, directed droplet transfer between immersed electrodes is achieved in an alkaline electrolyte without electrical short-circuit.

We propose a self-consistent explanation of Rieger-type periodicities, the Schwabe cycle, and the Suess-de Vries cycle of the solar dynamo in terms of resonances of various wave phenomena with gravitational forces exerted by the orbiting planets. Starting on the high-frequency side, we show that the two-planet spring tides of Venus, Earth, and Jupiter are able to excite magneto-Rossby waves, which can be linked with typical Rieger-type periods. We argue then that the 11.07-year beat period of those magneto-Rossby waves synchronizes an underlying conventional alpha-Omega dynamo by periodically changing either the field storage capacity in the tachocline or some portion of the alpha-effect therein. We also strengthen the argument that the Suess-de Vries cycle appears as an 193-year beat period between the 22.14-year Hale cycle and a spin-orbit coupling effect related with the 19.86-year rosette-like motion of the Sun around the barycenter.

The dataset contains python scripts to reproduce the Turner diagram (double diffusive convection), the image on voltage efficiency and the 1D temperature profile.

The dataset contains the risk assessment table as well as certain calculations.

Stationary electric energy storage systems can help balance temporal differences in electricity supply and demand. With the increasing use of volatile electricity sources, this task is becoming more important. Liquid metal and molten salt batteries are high-temperature storage devices and one option for stationary storage. They are based on the stable density stratification of a liquid alkali metal, a fused salt and a molten heavy metal. Mediated by the high operating temperature, which must be above the melting temperatures of the individual phases, interfacial reactions are rapid and transport processes are fast. High current and power densities can thus be reached. The completely liquid cell interior enables conceptually simple scalability at the cell level, which suggests favorable energy-related investment costs. Electrode and electrolyte layers possess thicknesses in the millimeter range and consist either of pure metals or a small number of components. Both properties will facilitate recycling considerably. The battery concept enables the use of abundant and cost effective active material combinations like Na-Zn. In contrast to most other battery systems, fluid mechanical processes, which are closely coupled to charge transport and transfer, are of relatively high importance. The talk will present selected physical phenomena in liquid metal batteries as well as discuss their possible role in a future energy system.

Die geplante Umstellung des Energiesystems auf fluktuierende Erzeuger zieht einen immensen Bedarf an Speichern nach sich, um Angebot und Nachfrage auszugleichen. Der Vortrag stellt verschiedene Arten von Flüssigmetallbatterien vor, die derzeit mit dem Ziel einer ökonomischen stationären Energiespeicherung entwickelt werden.

Energie ist auf vielfltige Weise mit dem Leben verknüpft. Im Laufe der Geschichte dominierten unterschiedliche Energieträger. Der Vortrag nimmt sie unter die Lupe und zeigt den Wandel ihrer Nutzung und die damit verbundenen Konsequenzen. Ein Schwerpunkt ist die im Horizon 2020 Projekt SOLSTICE entwickelte Speichertechnologie.

Im Zusammenspiel magnetischer und elektrischer Felder entstehen elektromagnetische Kräfte. Deren praktische Anwendung z.B. in Elektromotoren ist aus unserem Alltag nicht mehr wegzudenken. Elektromagnetische Kräfte sind aber auch in der Lage, leitfähige Flüssigkeiten, wie Elektrolyte und Metallschmelzen, kontaktlos zu beeinflussen. Die Vielfalt an Strömungskonfigurationen, die mit einfachen Permanentmagneten in einer Elektrolysezelle einstellbar sind, wird im Experiment demonstriert.

Within the Horizon 2020 project SOLSTICE, a molten salt battery has been developed. The battery employs sodium and zinc as anode and cathode respectively and operates at around 600 oC with a completely liquid interior. The primary advantage of this design is its low materials’ cost. However, multiple challenges must be overcome if it is to become commercially viable. These include corrosion of metallic components by the molten salt electrolyte, and self-discharge promoted by transport of cathode materials (Zn2+ ions) to the anode. Efforts to suppress the latter especially benefit from modelling, as the rate of self-discharge is primarily determined by mass transport processes in the electrolyte. Such models require experimental validation, thus, a small-scale experimental cell has been constructed for this purpose. It has been designed specifically for operation during analysis by radiographic methods (neutron beam and X-ray imaging). The distribution of the active materials can be observed at different stages of the charging-discharging cycle. This presentation will provide an overview of current modelling activities at HZDR related to the sodium-zinc battery, together with first (preliminary) experimental results and the most recent progress towards designing a “transparent” cell.

To bring the novel Na-Zn molten salt battery to market, many unresolved issues – such as self-discharge, migration of Na away from the current collector, and electrolyte “creeping” – must be resolved. Within the framework of the Horizon 2020 project SOLSTICE, a working battery prototype must be delivered. To support this objective, a small-scale experimental cell that can be used for fundamental research has been built. The cell has been designed to permit in situ radiographic imaging of its interior. The aim is to charge and discharge this cell in a neutron beamline and an X-ray source, to observe mass transfer of electroactive species and any flow that occurs during cycling. Of most interest are how these phenomena depend on the geometry and chemical composition of the different cell components, e.g. the positive and negative current collectors. With a completely liquid interior, all the cell’s components must retain their performance characteristics at its 600oC operating temperature. Besides thermal stress, the cell’s walls and current collectors must resist corrosion by liquid Zn, Na, and the molten salt electrolyte (as well as their vapors). Maintenance of this high internal temperature also requires sufficient thermal insulation, and – in an isolated test cell – an external heating system, and neither of these should interfere with the imaging techniques. Preliminary attempts to cycle the cell for an extended period of time (>4 weeks) have been successful. Pilot imaging tests using neutron and X-ray radiography have confirmed that the different layers (the electrodes and electrolyte) can be distinguished from one another, and spatial variations in the chemical composition of the electrolyte can be resolved. However, corrosion remains a limitation for long-term structural stability, so optimization of the cell’s components is ongoing. Long-term cycling data and X-ray/neutron images will be presented in this talk, and their implications for improvements to the

There is a close and multifaceted relation between fluid dynamics and the charge/discharge behavior of liquid metal batteries. The talk will give an overview of numerical and experimental work on transport phenomena in liquid metal batteries and discuss how they influence the cycling behavior of the cells.

The old question of whether the solar dynamo is synchronized by the tidal forces of the orbiting planets has recently received renewed interest, both from the viewpoint of historical data analysis and in terms of theoretical and numerical modeling. We aim to contribute to the solution of this longstanding puzzle by analyzing cosmogenic radionuclide data from the last millennium. We reconsider a recent time-series of ¹⁴C-inferred sunspot data and compare the resulting cycle minima and maxima with the corresponding conventional series down to 1610 A.D., enhanced by Schove's data before that time. We fnd that, despite recent claims to the contrary, the ¹⁴C-inferred sunspot data are well compatible with a synchronized solar dynamo, exhibiting a relatively phase stable period of 11.07 years, which points to a synchronizing role of the spring tides of the Venus-Earth-Jupiter system.

Batteries with liquid metal electrodes are attractive candidates for sustainable energy storage applications due to low manufacturing cost as well as high recyclability. For broad applications, these batteries should be developed for lower operating temperature, higher cell voltage, and membrane-free cell configuration. Here, we demonstrate a new type of membrane-free electrochemical energy storage system relying on liquid alkali metals and iodide. As a proof-of-concept study, membrane-free alkali metal-iodide (A-AI) batteries were constructed by a facile cell assembly introducing current collectors, LiI-LiCl-KI-CsI salt mixture, and an insulator without relying on solid-state mediums for separating electrolytes. For the initial assembly, no active electrode materials were required since they can be naturally formed during battery operation. Despite the unoptimized cell construction, the membrane-free A-AI batteries showed promising electrochemical performance such as voltage efficiency of ca. 40 % at 500 mA/cm2, maximum specific energy of 34.2 Wh/kg with an energy efficiency of 59 % for a charging/discharging period of 5.8 h and reliable stability for 250 cycles. Even without ion-selective membranes, we observed a relatively low self-discharge rate of 3.56 mA/cm2, which implies the possibility of an iodine-concentrated layer at the bottom of the cell. This was further supported by post-mortem analyses using neutron radiography. Additionally, X-ray photoemission spectroscopy was performed to identify the changes in the iodine concentration in the cell.

In this work a 1D finite volume based model using coupled meshes is introduced to capture potential and species distribution throughout the discharge process in a lithium–bismuth liquid metal battery while neglecting hydrodynamic effects, focusing on the electrochemical properties of the cell and the mass transport in electrolyte and cathode. Interface reactions in the electrical double layer are considered through the introduction of a discrete jump of the potential modelled as periodic boundary condition to resolve interfacial discontinuities in the cell potential. A balanced-force like approach is implemented to ensure consistent calculation at the interface level. It is found that mass transport and concentration gradients have a significant effect on the cell overpotentials and thus on cell performance and cell voltage. By quantifying overvoltages in the Li||Bi cell with a mixed cation electrolyte, it is possible to show that diffusion and migration current density could have counteractive effects on the cell voltage. Furthermore, the simulated limiting current density is observed to be much lower than experimentally measured, which can be attributed to convective effects in the electrolyte that need to be addressed in future simulations. The solver is based on the open source library OpenFOAM and thoroughly verified against the equivalent system COMSOL multiphysics and further validated with experimental results.

Die geplante Umstellung des Energiesystems auf fluktuierende Erzeuger zieht einen immensen Bedarf an Speichern nach sich, um Angebot und Nachfrage auszugleichen. Der Vortrag stellt verschiedene Arten von Flüssigmetallbatterien vor, die derzeit mit dem Ziel einer ökonomischen stationären Energiespeicherung entwickelt werden.

Yamdb (Yet Another Materials Database/YAMl materials DataBase) is a Python library providing thermophysical properties of liquid metals and molten salts in an easily accessible manner. Mathematical relations describing material properties - usually determined by experiment - are taken from the literature and implemented in Python. The coefficients of these equations are stored separately in YAML files.

Raw data from experiments with membrane-free alkali metal-iodide cells containing XPS results, phase-diagram calculations, neutron radiography images, electrochemical cycling data, and electron microscope images of the carbon felt used.

Solver and simulation data for validation test case

Goma (GO MAterials database) is a program enabling command line access to the  YAML files distributed with Yamdb. It implements the equations necessary to calculate the thermophysical properties from the coefficients stored in the YAML database. Yamdb (Yet another materials data base) and Goma address the need to provide thermophysical properties of liquid metals and molten salts in an easily accessible manner. Mathematical relations describing material properties - usually determined by experiment - are taken from the literature. Equations and their coefficients are stored separately. The former can be implemented in any programming language (Go in this case) and the latter are kept in YAML files together with additional information (source, temperature range, composition, accuracy if available, etc).

Since 2011, fluid dynamics research in liquid metal batteries has been pursued at HZDR, with multiple flow instabilities identified as critical for safe and efficient operation. This is still an ongoing process from which new research topics are constantly emerging. In the poster presentation, I will introduce two future research projects closely connected to liquid metal batteries: firstly, a new model experiment to study the metal pad roll instability, which is currently under preparation in the framework of a recently approved DFG project. Secondly, we are planning another project on the investigation of different solutal- and electrocapillary flow phenomena, hitherto widely disregarded in the context of liquid metal batteries.

The liquid metal battery (LMB) technology is highly promising for grid scale stationary energy storage. Those batteries consist of two liquid electrodes and a liquid or solid state electrolyte. Due to the possible usage of earth-abundant and inexpensive materials, LMBs are sustainable and eco-friendly. The LMBs in the present study contain a molten salt liquid electrolyte. Since the batteries are fully liquid, fluid flow needs to be considered additionally to electrochemistry and electromagnetic fields. For numerical investigations, coupling of the corresponding fundamental equations as well as the different regions in the battery is needed, which is highly challenging. Besides multiple fluid flow phenomena that are affecting the battery performance positively as well as negatively, species transport in the electrolyte and the cathode has an influence on the cell potential as well. In the presented talk, a quasi-one-dimensional method to calculate the ionic species distribution and the corresponding overpotentials in a LMB is presented. Since these phenomena are – to the best knowledge of the authors – rarely investigated, fluid flow is neglected for simplicity. The method is based on a simulation that solves current density and potential distribution in the whole battery. This requires modeling of the electrochemical double layer as well as multi-field coupling. Hereby, the finite volume method (FVM) is used and the simulations are performed using the open source tool OpenFOAM. Application cases are Li||Bi and Na||Zn cells (see Figure 1), having slightly differing working concepts. Li||Bi batteries are already investigated to a large extend and most material properties are readily available. Therefore, a validation study of the numerical solver is performed with these LMBs. On the other hand, Na||Zn batteries are even more sustainable and eco-friendly. The authors contribute, among others, to the development of the latter within the European Union’s Horizon 2020 pr

High-temperature batteries with molten metal electrodes have been explored for more than 50 years. Today, three such devices are commercially available: the sodium-sulphur battery, the ZEBRA (or Na-NiCl2) battery and the Ca-Sb liquid metal battery. In view of the need to integrate large amounts of renewable energy into the electric grid, several alternative stationary energy storage technologies are currently being explored. The main objective of this research is to reduce the storage price and improve the lifetime, sustainability and recyclability of these devices. Within the Horizon 2020 project SOLSTICE1, two different Na-Zn molten salt batteries are currently being developed. While the first cell operates with a solid ceramic electrolyte at 300°C, the second employs a fully liquid electrolyte working at 600°C. The talk will give an overview of the working principle, challenges and opportunities of the Na-Zn battery concept also highlighting the fluid dynamic aspects of battery operation. Some first experimental results, which have been obtained during the last year, will be presented.

The abstract submitted to the 241st ECS meeting deals with the principle of liquid metal batteries (LMB), their pros and cons and the occuring flow phenomena in general. A special focus is set on Li||Bi cells as well as on occuring overpotentials when operating the battery. A numerical approach that is used to investigate the cell using the tool OpenFOAM is presented. Further, a validation study is performed and an application case is studied. Attached, the full abstract can be found.

Liquid metal batteries (LMBs) are electrochemical energy storage devices featuring two liquid metal electrodes divided by a fused salt electrolyte. Convection in the electrolyte is typically assumed to be quite intense because it has the by far lowest electrical conductivity of all three layers and is therefore subject to strong Joule heating under typical current densities. Given the central role of the electrolyte for the LMB's performance characteristics and the consequences of typical assumptions (e.g., no mass transport limitations for charge transfer), it is worthwhile to investigate convection in this layer in detail. Doing this by means of numerical simulations performed using the free software library OpenFOAM is the purpose of the contribution at hand. Thermally driven convection in the electrolyte means first and foremost internally heated convection that is of importance for topics as diverse as mantle convection, nuclear reactor engineering, and astrophysics. For a relatively recent comprehensive review see Goluskin During charge, an additional source of momentum is provided to the electrolyte via viscous coupling at the positive electrode/electrolyte interface: solutal convection in the positive electrode. Viscous coupling drives motion in the vicinity of the lower electrolyte/electrode interface. The interplay of both drivers (internal heating and viscous coupling) leads to interesting dynamics. Already at quite low Rayleigh numbers Ra , regular motion exists in the electrolyte that modifies the temperature field there. Following Kulacki and Goldstein , the quoted Rayleigh number is based on the Joule heat release and the electrolyte layer's half height. The convective cooling parameter defined by Peckover and Hutchinson describes the ratio of the maximum temperature that would occur if heat transport were purely conductive, to the maximum value of the (height dependent) temperature profile in the fully developed flow averaged over time and in horizon

There is a wide range of flow phenomena to be expected in liquid metal battery systems. However, most of them have only been investigated numerically or in low-temperature model systems. To understand what actually takes place during operation and which flow phenomena prevail in a realistic liquid metal battery, an investigative study of a relatively new type of molten salt battery, Na||ZnCl2, is planned. This poster will present the objectives, challenges, and current status of a recently started x-ray and neutron imaging campaign of flow phenomena in high-temperature batteries at 600 oC.

Charge transfer and mass transport are directly linked with operating batteries. In liquid metal batteries (LMBs) additional flow phenomena heavily influence the cell performance. Those have widely been investigate numerically as well as experimentally. But, concentration gradients due to mass transport were mostly neglected in previous research – especially in the electrolyte. Implementing the prevalent equations into the finite volume solver OpenFOAM and investigating mass transfer overpotentials in the electrolyte independently revealed that they can have a significant influence on the cell performance. So, the interplay between flow phenomena and electrochemical transport should be subject of future investigations. Na||Zn batteries differ from the previously investigated “classical” LMBs, hence it is important to asses the possible flow phenomena and their area of occurrence.

For longer than one decade, liquid metal batteries (LMBs) are developed with the primary aim to provide economic stationary energy storage. Featuring two liquid metal electrodes separated by a molten salt electrolyte, LMBs operate at elevated temperature as simple concentration cells. Therefore, efficient mass transfer is a basic prerequisite for their economic operation. A thorough understanding of the relevant mechanisms cannot be achieved by studying single layers in isolation. With this motivation, the effects of solutal- and thermally-driven flow are studied, as well as the flow coupling between the three liquid layers of the cell. It is shown that solutal convection appears first and thermal convection much later. While the presence of solutal flow depends on the mode of operation (charge or discharge), the occurrence of thermal convection is dictated by the geometry (thickness of layers). The coupling of the flow phenomena between the layers is intriguing: while thermal convection is confined to its area of origin, i.e. the electrolyte, solutal convection is able to drive flow in the positive electrode and in the electrolyte.

Lithium-bismuth bimetallic cells are amongst the best explored liquid metal batteries. A simple and fast one-dimensional cell voltage model for such devices is presented. The equilibrium cell potential is obtained from a complex two-dimensional fit of data drawn from multiple studies of equilibrium cell potential and rendered congruent with the phase diagram. Likewise, several analytical and fit functions for the ohmic potential drop across the electrolyte are provided for different battery geometries. Mass transport overpotentials originating from the alloying of Li into Bi are modelled by solving a diffusion equation, either analytically or numerically, and accounting for the volume change of the positive electrode. The applicability and limitations of the model are finally illustrated in three distinct experimental settings.

Liquid metal batteries (LMBs) are introduced as future candidates for grid scale electricity storage. Their completely liquid cell interior entails a prominent role of fluid mechanics to understand and model their behaviour. We describe the equations used to compute electrochemical reactions, heat and mass transfer, electromagnetic fields, and fluid flow and explain the simplifications that can be made in the case of LMBs. The implementation of solution algorithms in OpenFOAM pertaining to domain coupling, multiphase simulations, mesh mapping, and operator discretisation are discussed in detail and accompanied by example code.

Outside the classical domains of magnetohydrodynamics, plasmas and liquid metals, the action of electromagnetic forces can be observed as well in electrolytes. The talk will start with examples on the control of flat plate boundary layers and separated flows and discuss their effectiveness and efficiency. Stationary as well as periodic Lorentz forces are thematized in this context and proof to be a versatile tool for research while high energy demand limits their applicability for naval applications. Switching the context to electrochemical processes, where an electrical current is inherently present, alleviates the question of energy demand and opens-up a large field of additional topics: Improved mass transfer can be used to increase the limiting current density and thereby the space-time yield of processes. Efficiency of water electrolyzers benefits from accelerated removal of bubbles from the electrodes. Magnetic gradient forces can assist in the build-up of nano-structured ferromagnetic layers using comparably cheap electrochemical technology.

There is a close and multifaceted relation between fluid dynamics and the charge/discharge behavior of liquid metal batteries. The talk will give an overview of experimental and - to a minor extend - numerical work on instabilities that might be relevant for the operational safety of large cells and on flows that are able influence mass transport overvoltages, like solutal and thermal convection.