FeEnCap – Development of an iron Slurry/Air Storage Battery
Encapsulated Iron Materials for Iron Slurry/Air Accumulators for Stationary Energy Storage
In recent years, the increasing use of renewable energy sources such as solar and wind energy has significantly increased the need for sustainable stationary energy storage systems. However, the full potential of renewable energies can only be exploited if surplus energy can be stored on a large scale and used when needed. In order to avoid additional environmental pollution and reduce dependence on resources, the development of batteries that use environmentally friendly, cost-effective and readily available electrode materials has been driven forward in recent years. For this reason, they offer a number of advantages for the stationary storage of large amounts of energy!
Development of an Iron Slurry/Air Storage Battery
Iron slurry/air storage has proven to be a promising alternative to conventional battery concepts, in which iron is used as an environmentally friendly, cost-effective and readily available battery mass in the slurry. The FeEnCap project is dedicated to the further development of iron slurry/air storage systems as stationary energy storage systems.
The iron slurry/air storage system is a new type of battery concept that was introduced as part of the BMBF joint project FeEnergy from 2018 to 2021. Instead of a conventional solid iron electrode, an iron-containing battery mass is conveyed through the battery cell in the form of a slurry during operation. This makes it possible to store additional energy in a reservoir outside the cell.
The slurry consists of active iron-based particles in an alkaline solution and additional additives to improve the electrical conductivity. A proof-of-concept was able to prove the principle function of the iron slurry/air accumulator! One of the biggest challenges now is to achieve satisfactory rechargeability. The reason for the inadequate rechargeability is the considerable contact resistance caused by the low conductivity of the discharged iron particles and the iron deposits on the current-conducting electrode.
FeEnCap Project Partners
As part of the joint FeEnCap project, the companies VARTA, IBU-tec (our parent company), inprotec and Walter Lemmen are now tackling the challenges of the iron slurry/air storage battery. We are receiving scientific support from the Institute of Energy and Climate Research (IEK-9) at Forschungszentrum Jülich and the VDEh-Betriebsforschungsinstitut. One of the promising approaches of the research project is the use of core/shell particles, which consist of an iron-based core and an electrically conductive shell. In this way, we aim to minimize the contact resistance between the particles and prevent the formation of residues on the discharge electrode. Furthermore, it is foreseeable that the search for alternative composite materials and the further development of the sludge cell should contribute to a significant increase in the performance of iron sludge storage systems. The significant improvement in the charging and discharging behavior of the sludge with the new material design is to be demonstrated in a small, advanced storage system.
Challenges and Problem Statement
Fe-slurry/air cell introduced as a novel battery concept in the FeEnergy research project
Proof of concept (A: 25 cm²): UCell= approx. 0.8 V, discharge up to 28 % of theoretical capacity
Rechargeability still insufficient
Problems are caused by the contact resistance of the discharged iron particles and iron deposits on the contact electrode
Development Process of our Iron Slurry/Air Reservoirs
The FeEnCap project is taking on the technical challenge of developing a marketable iron slurry/air storage battery: from raw materials to a ready-to-install product to help manufacture stable and safe iron slurry/air accumulators for stationary energy storage with high capacity in Germany.
Iron slurry/air storage system were introduced as innovative battery concepts as part of the BMBF joint project FeEnergy 2018. A proof-of-concept has demonstrated the basic operating principle of the iron slurry/air storage system. The FeEnCap project (funding code 03XP0188A-F) is now dedicated to the further development of this storage system.
Our scientists are involved in the development and production of encapsulated iron-copper-carbon materials for iron-slurry/air accumulators for stationary energy storage with high capacity in a combination of process steps in our in-house pulsation reactors and in the rotary kiln.
In the initial stages, a promising battery system was identified and the performance parameters defined, and a specific Fe-Cu-C raw material was selected. During the development of the Fe/Cu/C slurry, a regular exchange of results with the project partners enabled the further development and performance optimization of the cell components to be achieved.
