Newsletter Edition 12/2021

In our second edition we briefly review the first half of the project and present our activities concerning the higher scales, such as a microCT scan of a graphite felt, our approach to numerical stack & system simulations and, finally, the total cost analysis for two lab-scale systems based on different electrolytes.

Read the full version here

New Paper about Electrochemical Interface Dynamics

July 2022

© Jia Yu

SONAR partner CNRS presents a 3D kinetic Monte Carlo model to study the electrode-anolyte interface of a methyl viologen-based organic redox flow battery. This model captures various electrode processes, such as ionic displacement and degradation of active materials.


Upcoming: FLORES workshop on digital twins for flow batteries

September 12 2022, online

Virtual event  -- free of charge -- register now 

A roadmap toward redox flow battery passport

The European Battery Directive foresees monitoring of batteries on their global warming potential and utilization of critical raw materials. FLORES, a network of 13 EU-funded projects, invites speakers to show best practice examples from Lithium-Ion battery applications and other areas to define a roadmap for redox flow batteries towards a battery passport.

Sustainability of Flow Batteries

FLORES: Joint review about LCA

Suggested product system and functional unit definition for LCA of Flow Batteries.

A transition from fossil to renewable energy requires the development of sustainable electric energy storage systems capable to accommodate an increasing amount of energy, at larger power and for a longer time. Flow batteries are seen as one promising technology to face this challenge and should not shy away from competition when it comes to sustainability goals. Based on a review of 20 relevant life cycle assessment studies, this paper explored relevant methodological choices regarding the phases: goal and scope definition, inventory analysis, impact assessment and interpretation.

Find the full article here:


Joint workshop of the two EU projects COMPBAT and SONAR

June 27-29, Brussels / Belgium

On June 27, 2022, the two EU projects COMPBAT and SONAR will organize a joint workshop within the International Flow Battery Forum in Brussels / Belgium. The workshop will take place on Monday and thus one day before the actual program of the IFBF in the same premises. The topic of the workshop is modeling and simulation for novel active materials for redox flow batteries, as well as the EU-wide international cooperation in research and development. Speakers from both projects will be invited to present and discuss the status of different aspects of the developments. SONAR will present the state of the art of a high-throughput screening process on a working demonstrator and discuss it with the participants from industry and academia. Furthermore, a panel discussion on EU-wide collaboration will take place and a poster session in the evening will conclude the day.

Registration and further informationen:

Participation in the 241st meeting of the Electrochemical Society

May 2022 Vancouver / Canada

Daniel, Piotr and Jens from the SONAR project attended this year's 241st Electrochemical Society Spring Meeting in Vancouver, Canada. In total, they gave two keynote talks, three additional talks and chaired two sessions in redox flow batteries and computational electrochemistry.


Participation of SONAR at the 31st ISE topical meeting of the International Society of Electrochemistry

May 2022, Aachen / Germany

At this meeting, two SONAR members, Astrid and Jens, participated in the conference. The topic of the event, which lasted several days, was modeling and simulation of different electrochemical energy storage and conversion systems. Astrid presented results on high-throughput screening in the project. Jens gave an overview of the status of developments in the whole project.

Tent City of Science & Science Night

May 2022, Bonn / Germany

© Michael Krapp, Fraunhofer SCAI

Jan and Astrid presented SONAR, the basics of Redox Flow Batteries and the search for materials to the general public. With a jigsaw and some candidate molecules we  confronted the audience with the task of finding the best combination to compose a full cell. Our booth received a lot of interest and we had a lot of fun.

Smart Energy Expo, Sydney/Australia

May 2022

SMART Energy is one of the largest renewable energy events in Australia.
Among other things, a technology demonstrator for the High-Throughout screening process, which is being developed in the international SONAR project, was represented. The software for the search for new active materials for aqueous organic redox flow batteries could be tested on a laptop. In addition, materials of cells, electrodes and a small demonstration redox flow battery were shown. The booth was supervised especially with the support of UNSW students from UNSW Challeng program NextGEN.

Animation of RFB half-cell compartment during discharge operation

March 2022

© Amadeus Wolf, KIT, Germany

CFD simulations based on the Finite Volume Method for an electrolyte passing through a section of carbon felt: watch the behaviour of several (normalized) quantities 

  1. Velocity profile (arrows) of flow coming from the bottom to the top,
  2. Quasi steady-state TEMPO+ concentration profile within the electrolyte and during normalized time (constant inlet concentration assumed),
  3. Butler-Volmer current at the surface of the fiber domain, and
  4. Electrolyte potential distribution and ionic current (arrows).

New Paper about a physics-based 0D-U-I-SoC Cell Performance Model

March 2022

WP4 and co-workers present a physics-based dimensionality reduced model for the performance prediction of aqueous organic redox flow batteries. The model allows for fast evaluations of the cell voltage and power density, which are expressed explicitly in terms of the electric current density and state of charge. The model takes into consideration important phenomena, such as the activation and concentration overpotentials in the electrodes as well as the non-negligible electro-osmotic drag of water through the membrane. A sensitivity analysis of the model indicates the influence of various model parameters at different current densities on the predicted cell voltage. In this work we found the formal potentials and ohmic cell resistance to be the most critical parameters for performance prediction. Experimental parameterization and validation on cycling and polarization experiments revealed good agreement with the experiments within a predicted range of validity due to the different simplifying assumptions.

SONAR attended the autumn school of the Nordic Flow Battery Network

November 2021

Prof. Dr. Piotr de Silva at the autumn school in Turku, Finland.

At the end of November 2021, the autumn school of the "Nordic Flow Battery Network" took place in Turku, Finland. It was hosted by the University of Turku under the leadership of the EU-funded COMPBAT project. Similar to SONAR, COMPBAT is concerned with the development of a high-throughput screening process to search for new organic active materials for redox flow batteries.

Over the three-day event, a variety of speakers reported on different topics in the research and development of redox flow batteries. PhD students were given the opportunity to present posters on their work, give talks or exchange information. The last day of the autumn school was entirely organised by the PhD students in Turku. The speakers were from a mixture of academic and commercial backgrounds, so that application-related content was also presented beside basic research.

Among the invited speakers were Prof. Dr. Piotr de Silva from the Technical University of Denmark and Prof. Dr. Jens Noack from Fraunhofer ICT, who are both involved in SONAR. Piotr gave a talk on DFT calculations (DFT - density functional theory) in general and specifically in relation to flow batteries. Jens gave a short overview of the development of flow batteries over the last 15 years at Fraunhofer ICT.

SONAR will present a first functional demonstrator for the simulation-based screening of organic active materials for novel redox flow batteries.

March 2023

Screenshot of interface for entering compounds and search criteria

This year SONAR will share a booth with the German-Australian Alliance for Electrochemical Storage for Renewable Energy (CENELEST) at Smart Energy 2022 in Sydney, Australia. For the first time, a functional demonstrator will be presented for the high-throughput screening method to be developed in SONAR. The demonstrator allows the calculation of parameters such as redox potentials and cell voltages on the basis of optimised scale models. The user can enter structural formulae of organic chemical compounds and obtain the results within a few seconds. The high-throughput screening will later be able to select, from hundreds of thousands of organic compounds, those with the highest potential for application as active materials for novel redox flow batteries, and also calculate their properties.
The Smart Energy Council Conference and Exhibition is the largest meeting place for renewable energy topics in Australia, and will take place this year on 4-5 May at the ICC in Sydney, Australia.

SONAR successfully completes phase I of the project

November 2021

Flow battery test cell at the Fraunhofer ICT for simulation results validation

After a project duration of 18 months, the SONAR project was evaluated by INEA, the project executive agency of the European Commission (EC), as planned. Within the framework of a report and a special review meeting, the EC project officers and an external reviewer were presented with the results of the project so far. The main focus was on the status of the development of the high-throughput screening method to search for new organic active materials, as well as the sub-aspects based on atomistic, Kinetic Monte Carlo (meso-scale) and continuum modelling and simulation. SONAR successfully passed the peer review and secured funding for the next phase, which will also focus on the stack, system, costs and behavior in the network.

ZHAW publishes open source 0D cell model and program to calculate flow battery characteristics

November 11, 2021

Screenshot of GUI for interactive manipulation

As part of the EU-Australian SONAR project, the University of Applied Sciences Zurich, Switzerland, has published an open-source program for calculating the characteristics of organic redox flow batteries. The program is based on the popular mathematical application "Mathematica" and allows the evaluation of polarization curves as predicted by the 0D-U-I-SoC model for user-specified model parameters. Especially for small and medium current densities, which are not in the range of mass transport limitations, the results of the software are very accurate and can be adapted to the specific battery chemistry by adjusting the input parameters. This allows statements to be made about the expected voltages and currents, as well as capacities and energy densities at different states of charge for an almost infinite number of battery chemistries.
In the SONAR project, ZHAW is responsible for the development of optimized cell models for automated high-throughput screening of organic active materials for future, novel redox-flow batteries to store renewable energy.
The open source simulation software and a user discussion forum are available on GitHub.

Flow battery systems and their future in stationary energy storage – Policy brief

November 2, 2021

On 9th July 2021, at the Summer Symposium of the International Flow Battery Forum, the FLORES Network of Flow-Battery Research Initiatives held a workshop to identify research
needs, barriers, potential markets and impacts of flow batteries. The outcomes, including resulting policy recommendations, are provided here.

Work on system modelling and cost analysis started in SONAR

September 2021

Current distribution of the 2D single cell of VRFB under different constant flow rates, left) flowrate = 30 mL/min right) flow rate = 5 mL/min

The University of New South Wales and Fraunhofer ICT started their work on stack and system modeling and cost analysis for organic flow batteries, with one new PhD student at each of the two institutions. The system modeling will be carried out using a multiphysics approach, where first the hydraulic, electrochemical and thermal properties of a single cell, then a stack and finally a whole flow battery system are modeled and simulated. The results will lead to a better understanding of systems and thus to cheaper and more reliable systems, and also form the basis for the cost analysis.

In the cost analysis of flow battery systems, Fraunhofer ICT is concerned with linking technical parameters with costs using mathematical functions. The objective is to map a cost structure for the investment costs of flow batteries in order to determine cost proportions and for sensitivity analyses. Based on the calculated costs, batteries can be compared on the basis of investment costs (CAPEX). A much more substantiated comparison is possible based on levelized cost of storage (LCOS), where lifetime costs are calculated in relation to energy throughput. In the future, it will be possible to calculate the LCOS of a large number of new organic flow battery chemistries automatically, in order to be able to develop low-cost candidates for new, safe and environmentally friendly organic flow batteries for the storage of renewable energy.

New Paper about predicting pH-dependent Redox Potentials

June 29, 2021

In the Special Issue Computational Design and Modelling of Organic Materials for Energy Applications of Molecules Rocco Fornari and Piotr de Silva present a computational protocol combining DFT and Cheminformatics for pH-Dependent Redox Potentials:

Animation of RFB discharge simulation with constant inlet concentration

June, 2021

© Amadeus Wolf, KIT, Germany

The image shows a pore scale 2D slice that is coloured according to the [4-OH-TEMPO]+ concentration in mol/m³.  Wholes represent cylindrical electrode fibres and arrows represent the steady-state velocity profile in m/s with Reynolds-Number of 0.0005. Note the depletion of [4-OH-TEMPO]+  at the electrode-electrolyte interface over time: The concentration profile evolves according to the velocity field and reaches a steady state after several milliseconds.

New paper on a graph convolutional network for rapid prescreening of organic compounds

May 31, 2021

A paper on machine learning for predicting formal potentials appears in a Special Collection on Artificial Intelligence in Electrochemical Energy Storage in Batteries & Supercaps by Laura Berg et al:

Interview of Maria Skyllas-Kazacos by QEM’s managing director Gavin Loyden

May 27, 2021

Find the full interview here.

Flow Batteries Europe: Long-Term Strategy for Flow Battery Technology

April 28, 2021

In order to create more awareness for RFB technology, and to combine the interests of industry and research in the field, the association “Flow Batteries Europe” was founded on 28.04.2021. Flow Batteries Europe will try to increase knowledge about redox flow batteries through dissemination and policy briefing.

The German/Australian Alliance for Electrochemical Technologies for Renewable Energy Storage (CENELEST) is a founding member of Flow Batteries Europe. CENELEST member and FlowCamp coordinator Dr. Peter Fischer (Fraunhofer ICT) was elected to the Executive Board and will represent Fraunhofer ICT (Germany) and the University of New South Wales (Australia) in Flow Batteries Europe.

For more information about the association, please contact Peter Fischer or visit the website.