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Hydrogen-Bromine Flow Batteries

In the realm of energy storage, innovation is the key to achieving a sustainable future. A technology that has been gaining attention for its potential to revolutionize large-scale energy storage is flow battery technologies. Flow batteries are a type of rechargeable battery in which the electrolyte flows through one or more electrochemical cells from one or more tanks. During charging, the electrolyte flows through the cell and the chemical energy is converted into electrical energy. During discharging, the electrolyte flows through the cell in the opposite direction and the electrical energy is converted back into chemical energy.

There are a number of different types of flow batteries, but the most common type is the vanadium redox flow battery. Vanadium redox flow batteries use vanadium in different oxidation states as the active materials. Other types of flow batteries include zinc-bromine flow batteries and iron-chromium flow batteries.

Hydrogen bromine redux batteries (HBRB) or just hydrogen bromine batteries (HBRB) are a type of rechargeable flow battery that uses hydrogen and bromine as the active materials. THBr batteries work by splitting hydrogen bromide (HBr) into hydrogen ions and bromide ions during the charging phase. The hydrogen ions cross a membrane and absorb electrons, becoming hydrogen gas. The bromide ions remain in the electrolyte solution. During the discharging phase, the hydrogen gas is recombined with the bromide ions to form HBr again, releasing energy.

How They Work

HBFB work through a reversible electrochemical reaction involving hydrogen bromide (HBr) as the electrolyte. During the charging cycle, power flows into the system, resulting in the generation of hydrogen gas (H2) and the accumulation of HBr3 in the electrolyte. This hydrogen gas is stored separately, poised for use in subsequent discharge cycles. When discharging is required, the stored hydrogen gas is reunited with the HBr3, returning the system to its initial state with a fully replenished HBr tank. Remarkably, the electrolyte undergoes no degradation throughout this process, and the system operates in a self-contained manner, emitting no harmful byproducts.

Advantages of HBFBs
Cost Efficiency

Perhaps the most notable advantage of HBFBs is their cost-effectiveness when compared to lithium-ion. Bromine, a key component, is abundant and relatively inexpensive, with a global annual production exceeding 400,000 tons. As bromine is found in seawater, its supply is not restricted to geographical availability and cannot be dominated by a limited group of suppliers unlike Lithium, Cobalt and Vanadium.

Use of Inexpensive Membranes

HBFBs employ cost-effective membranes, contributing to their affordability. These membranes play a pivotal role in separating the two materials involved in the electrochemical reactions, enhancing the overall efficiency of the system.

High Power Density

HBFBs boast high power density relative to other flow battery technologies. This characteristic makes them particularly suitable for applications that demand rapid energy output, such as grid balancing and providing power to critical loads during outages.

Long Cycle Life

HBFBs are designed for longevity. They can handle daily discharge cycles for extended durations, ranging from 6 to 12 hours per day, and can potentially operate for 10 to 20 years without significant degradation.

Grid Balancing

The rapid energy output capability of HBr batteries makes them suitable for grid balancing, helping to stabilize electricity grids and meet fluctuating demand.


HBFBs are non-flammable and non-explosive, while lithium-ion batteries can be flammable and explosive if they are damaged or operated under extreme conditions.

Renewable Energy Integration

These batteries are well-suited for integrating renewable energy sources like solar and wind power into the grid. They serve as efficient buffers, mitigating the variability of these energy sources and ensuring a consistent power supply.

The first scaled up version of a hydrogen–bromine battery, a 50KW/100KWh system, was deployed in Rotem Industrial Park in Israel in April 2013.
The first scaled up version of a hydrogen–bromine battery, a 50KW/100KWh system, was deployed in Rotem Industrial Park in Israel in April 2013.

Disadvantages and Challenges
Low Energy Density

HBFBs, while cost-effective, exhibit lower energy density compared to lithium-ion batteries. This limitation restricts their suitability for applications requiring high energy storage capacity in compact spaces.

Complex Balance of Plant

The design of HBFBs involves complex components, including pumps and tanks for the electrolyte. This complexity can increase manufacturing, installation, and maintenance costs.

Unsuitable for Transportation

Due to their low energy density and complex balance of plant, HBFBs are not suitable for transportation applications in electric vehicles for instance, where high power and energy density are essential.


Concentrated solutions of HBr are highly corrosive, necessitating the use of chemically stable sealing solutions to ensure long-term operation.


HBr batteries can be recycled, while lithium-ion batteries are more difficult to recycle.


Like all flow batteries and due to their low energy densities, HBFBs are way more larger and bulkier than lithium-ion batteries. They often come in common containers. For this reason, they are typically used for largescale and heavy-duty grid energy storage or attached to power plants/electrical grids and are not suitable for non-stationary purposes like consumer electronics and electric vehicles.

Like other flow battery technologies, HBFBs are deployed in common containers. Source: Elestor
Like other flow battery technologies, HBFBs are deployed in common containers. Source: Elestor


The technology was first developed and used by NASA engineers. The first scaled up version of a hydrogen–bromine battery, a 50KW/100KWh system, was deployed in Rotem Industrial Park in Israel in April 2013. The battery was developed by EnStorage Inc., and it was the first grid-connected hydrogen-bromine flow battery in the world. Elestor is a Dutch company that has built on the technology emerging as a hydrogen-bromine battery specialist. It is developing and commercializing HBFBs for large-scale energy storage. The company was founded in 2014, and its technology is based on a number of patented innovations, including a new type of membrane and a new type of catalyst.

Elestor has made significant progress in the development and commercialization of its HBr flow batteries. In 2019, Elestor announced a partnership with Vopak, a global leader in tank storage, to develop and deploy large-scale HBr flow battery systems. In 2022, it announced that it had secured funding to bring its HBFBs closer to commercial production. In January 2023, Elestor received the Offshore Wind Innovators Award 2022 for its batteries.

Elestor is also working on a number of other projects to advance the development and commercialization of its HBr flow batteries. For example, in May 2021, it announced that its participation in a European Union-funded project to install HBr flow batteries on the Hinnøya island cluster in Norway. Elestor offers containerized versions of its HBr batteries with a power output of up to 200 kW and a storage capacity of 2,000 kWh. These modular solutions can be tailored to meet specific power and capacity requirements, providing flexibility to customers. With over 10,000 cycles of stable operation demonstrated during testing, Elestor's HBr batteries have exhibited impressive longevity. The stack modules can be replaced after this extensive cycle life, allowing the system to enjoy a full second life.

Elestor's work on HBr flow batteries has the potential to revolutionize the way that energy is stored and distributed. HBr flow batteries are well-suited for a variety of applications, including grid-scale energy storage, microgrids, and backup power. As Elestor continues to develop and commercialize its HBr flow batteries, the company is poised to play a major role in the transition to a clean energy future.

Elestor Media Photos Showing their New CEO standing just outside their hydrogen bromine battery
Elestor Is Working Hard to Scale Hydrogen Bromine Batteries. Source: Media Photos

What the Future Holds

The HBFB technology offers a promising path toward affordable and scalable energy storage. Its use of abundant and cost-effective materials, along with its potential for long cycle life, positions it as a valuable tool for transitioning to a renewable energy future. As researchers and innovators continue to refine this technology, we can expect to see even greater strides in the field of large-scale energy storage.

In a world hungry for sustainable energy solutions, hydrogen bromine batteries emerge as a noteworthy contender. With their unique combination of affordability, efficiency, and versatility, they may well play a pivotal role in the global energy landscape of tomorrow.

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