The Elestor solution
The choice of hydrogen and iron
Elestor is powered by a mission to build a storage system with the lowest possible storage costs per MWh. With this as our cornerstone criteria, and it is one that can only be met with inexpensive chemistries if we are to take full advantage of the typical flow battery features, our behind the scene R&D wizards have explored a variety of chemistry combinations.
In theory, there are many different chemistries that could be used to design a flow battery, but to date we have only come across two that could work in the real world. One relies on hydrogen and bromine as active materials, and this solution remains great on paper, but we have come to the conclusion that there is another, even better so-called redox coupling, namely hydrogen-iron, which is better suited to real-world applications and the present geopolitical environment.
Like bromine, iron is obviously abundantly available all over the world; indeed, arguably slightly more so than bromine, which is extracted from sea water and thus not abundant far from the sea. The importance of selecting a redox coupling made up of two materials that are not restricted by geographical availability has become even more important during the last couple of years. Given the ongoing geopolitical turbulence, it is more important than ever that we create a resilient and self-reliant energy storage solution that is independent from and cannot be dominated by a small group of suppliers, or indeed by a single or a small number of countries. Iron, hydrogen and bromine all have these qualities, unlike other materials such as lithium, cobalt and vanadium, which are presently more popular with makers of battery solutions in spite of their scarcity.
By going for abundant rather than scarce materials, we have by definition chosen very low-priced active materials. Not only presently, but for decades to come, indeed, even when large volumes will be required for high-volume production of hydrogen-iron flow batteries.
Another advantage of selecting a hydrogen and iron-sulphur redox couple, is that these enable a high power density [W/m2] as well as a high energy density [kWh/m3], both contributing to the reduction of storage costs per MWh.
Sure, this combination’s power and energy density is not quite as impressive as that of a hydrogen and bromine redox couple, but it still beats all other rival flow battery chemistries, while at the same time it comes with several other advantages.
The heart of all Elestor’s storage systems is the cell stack. This stack consists of a number of individual electrochemical cells, as shown above, connected in series.
Each membrane in this stack is in contact with the electrolyte circuit, an aqueous iron-based solution (FeSO4).
On the other side, each membrane is in contact with a hydrogen (H2) gas circuit. Both active materials circulate in a closed loop along their own respective side of the cell. The electrolyte (aqueous FeSO4 solution) and hydrogen (H2) circuits are separated by a proton-conductive membrane.
Enabling affordable green hydrogen for clean fuel production by applying Long-Duration Energy Storage
Author:
Dries Kleuskens (Business Developer)
Abstract
Green hydrogen production faces a critical design challenge: renewable electricity is intermittent, while clean-fuel processes such as ammonia, methanol and e-fuels require stable, high-utilization operation. With hourly RFNBO matching approaching, this mismatch will increasingly shape the economics of future clean-fuel hubs.
In this whitepaper, Elestor compares a traditional LFP + hydrogen storage configuration with an LDES-based hub design using Elestor’s hydrogen-iron flow battery upstream of the electrolyser. Based on 10 years of hourly solar and wind data for Ain Sokhna, Egypt, the modelled baseload case shows that a 36-hour Elestor flow battery can reduce LCOH by up to 20% by improving electrolyser utilization, reducing installed electrolyser capacity and avoiding separate downstream hydrogen storage.
Download the whitepaper to learn how long-duration energy storage can help make baseload green hydrogen supply more affordable, controllable and scalable.
Engineered for 25 Years: Commercial Durability Proven in Elestor’s Hydrogen–Iron Flow Battery Technology
Authors:
Kaan Colakhasanoglu (Stack Research Specialist)
Wiebrand Kout (CTO)
Abstract
Elestor’s hydrogen–iron flow battery architecture is put to the test and evaluated under continuous, commercially relevant operating conditions to assess durability, performance stability, and lifetime potential. The system combines a hydrogen gas circuit with an aqueous iron-based electrolyte, enabling independent scaling of power and energy while relying on abundant, low-cost active materials (±2.8€/kWh, enable reaching 15€/kWh CAPEX and 0.02€/kWh Levelized Cost of Storage at system level).
An extended continuous cycling campaign demonstrates stable operation at practical current density, temperature, and voltage windows representative of real-world deployment. Measured performance remains stable and fully recoverable through standard conditioning procedures. The absence of structural or electrochemical failure under sustained operation provides a robust empirical basis for extrapolating operational lifetimes of 20–25 years under standard use profiles.
This work positions hydrogen–iron flow battery technology as a durable, scalable, and economically viable solution for long-duration energy storage.
Energy Independence for Islands
Authors:
Willem de Vries (Charged Islands)
Mohamad Alameh (Charged Islands)
In cooperation with Floris van Dijk (Elestor)
Abstract
Due to recent declines in the cost of photovoltaic solar generators (PV) and battery energy storage systems (BESS), baseload renewable energy systems (BRES) can now outcompete a grey generation mode (diesel electricity generation) on a 24/7 basis. BRES now promise a 30% reduction in electricity generation costs compared to diesel generators for a wide set of geographies, often reducing generation costs by 100 EUR/MWh. This gap is expected to grow with the introduction of cheaper long duration energy storage (LDES) systems in the future, potentially reducing cost of electricity supply by 50% compared to diesel generation.
With economic arguments in favour of BRES, a movement towards deployment of such systems can be expected and is also encouraged and supported by the writers of this white paper.
Numerous islands will have to overcome various hurdles though trying to implement BRES. Examples of such hurdles are shortage of development & financing capabilities as well as the shortage of land and a lock-in of diesel generation assets.