Development of iron redox flow technology for storage systems

VoltStorage is developing a future-facing generation of energy storage solutions based on the iron redox flow technology.

Cost-effective and ecological: Iron Redox Flow Technology for energy storage systems

VoltStorage GmbH is developing a future-facing generation of energy storage solutions.

Munich, March 15th, 2021. The name of VoltStorage is synonymous with a groundbreaking high-tech solution on the electric storage battery market. The greentech company based in Munich, Germany, is the first in the world to produce environmentally friendly and resource-aware energy storage units for private households by using the vanadium redox flow (VRF) technology. VoltStorage’s solution is a highly sought-after and eco-friendly alternative to conventional lithium-ion (Li-Ion) energy storage products.  Now, the innovation-driven tech company is focusing its research and development activities on a future-facing energy storage concept based on the iron redox flow (IRF) technology. These new energy storage units are both eco-friendly and extremely low-cost and can operate at high temperatures such as temperatures in (sub-)tropical regions.

“IRF is a key technology for the energy storage industry because the materials used to produce the battery units are environmentally friendly, very low-cost and globally available,” explains VoltStorage CEO Jakob Bitner. “One of our company’s foremost goals is therefore to develop a market-ready energy storage system based on IRF technology. In the process, we are drawing on our extensive bank of in-depth experience in the field of redox flow technology. The first project milestone – a working small-cell system with total efficiency of over 75 percent – has already been reached and we are confident that we are on course for success.”  Once the test phase is completed, the next step will be to tackle the development of a full-scale battery system and to construct a prototype for this new energy storage generation.

How iron redox flow technology works

The heart of an IRF energy storage system is the redox flow battery unit. This is made up of two battery half-cells separated by a membrane, through which electrolyte liquid is pumped in independent cycles. This electrolyte is enriched with iron chloride. When the battery is charged or discharged, ions and electrons are transferred between the two half-cells, storing, or releasing energy in the electrolyte. In an uncharged state, both cells have identical oxidation states; charging leads to reducing the electrolyte in one half-cell and oxidizing electrolyte in the other. In the negatively charged half-cell, the iron in the electrolyte is deposited on the electrode. The battery capacity is dependent on the iron deposition: an increasing amount of iron deposition leads to a higher capacity.

Safe, eco-friendly and ultra-low-cost

The main part of the electrolyte is water which makes it 100% non-flammable, even in extreme conditions or faults. Iron is fully recyclable and is available in large quantities all over the world, making it a particularly low-cost material. The target is to achieve LCOS (levelized cost of storage) of 0,05 EUR/ kWh, making IRF storage systems the cheapest on the market. With these low overall costs, IRF technology is an environmentally friendly alternative that can be used as large-size scalable commercial and industrial energy storage systems. Unlike storage systems built around VRF or lithium-ion batteries, IRF storage units can be operated at high temperatures and are suitable in (sub-)tropical areas. VoltStorage’s research project opens up perspectives in regard to a reliable and affordable energy supply based on renewable resources for emerging and developing countries.

Research project until 2022

Landshut University of Applied Sciences is the research partner of this project, which receives funding from the German Federal Ministry of Economics and Technology. In the first phase of the project, the research team aims to develop a storage system with 8 kWh capacity that is compatible with solar and wind power sources. The next step will be a large-scale storage unit with a  capacity of 50 kWh for industrial and commercial applications. The research project is scheduled for completion by the end of February 2022.


About VoltStorage

VoltStorage develops energy storage systems based on an eco-friendly redox flow technology. These storages are designed to store excess energy generated during daytime hours from renewable sources like solar and wind power and make this energy available around the clock. Established in Munich in 2016, the greentech company devises sustainable energy storage solutions with the vision of providing energy generated from 100 percent renewable sources 24/7, thus creating a cleaner, fairer world for the generations to follow. In 2020, this vision was acknowledged at the international Start-up Energy Transition Awards (SET), where VoltStorage was chosen as one of the “Top 3 Start-Ups” in the „Renewable Energies & Materials“ category. The storage systems from VoltStorage  are developed and manufactured in Germany and can thus guarantee high standards and “Made in Germany” quality. VoltStorage energy storage units use the resource-saving redox flow technology, which reduces CO2 emissions by up to 37 percent compared to similar lithium-based systems. VoltStorage systems are thus among the most climate-friendly energy storage solutions currently available anywhere on the market. VoltStorage energy storage units are available from certified specialist retailers in Germany, Austria and Switzerland.

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