Flow Batteries Europe Written evidence (LES0019)



Some technologies are particularly suitable for large-scale deployment because the power rating is separable from the energy storage capacity, such as flow batteries. Flow batteries offer unique advantages in terms of tailored designs encompassing various combinations of energy and power. Additionally, the technology exhibits significantly extended cycle lifespans in comparison to Li-ion or Pb-A batteries, is safe, can be produced using abundantly available materials, and presents notable benefits in material reclamation and recycling. Flow batteries are potentially a cost-effective energy storage solution with a discharge power over a longer period of time (4-24h). The technology readiness levels (TRLs) of flow battery technology span from 4 to 9, varying based on the particular chemistry employed.


The Asia-Pacific region dominates global flow battery usage. China, Japan, South Korea, Canada, and the USA all have large-scale flow battery factories and are well-placed to ramp up production to meet future market needs. However, between 2014 and 2021, the United Kingdom was among the leading countries in terms of investment in flow battery technology in Europe and is home to considerable expertise in flow battery technology. The UK has the potential to lead in flow batteries research and industrial capacity within Europe.


In this submission, we have presented the most impactful flow battery projects from across the world and some examples of successful policy endeavors.



Flow Batteries Europe (FBE) represents flow battery stakeholders with a united voice to shape a long-term strategy for the flow battery sector. We aim to provide help to shape the legal framework for flow batteries at the EU level, contribute to the EU decision-making process as well as help to define R&D priorities. Flow Batteries Europe is working to create and reinforce networks between key stakeholders in the flow battery industry.




3. Which technologies can scale up to play a major role in storage?


Although numerous energy storage technologies show promise for future network operation, some are much better suited for large-scale implementation.


Large-scale technologies should have:


Some technologies are particularly suitable for large-scale deployment because the power rating is separable from the energy storage capacity, such as flow batteries. Flow batteries offer versatility by separating power capability from energy storage capacity. They can be easily retrofitted with more electrolyte storage, increasing energy capacity without impeding the power rating of the system. Tanks can be relatively low cost – similar to bulk storage tanks that are generally widely available for liquid storage, such as used in the fuels and chemicals industry. Large tanks benefit from economy of scale, with a low incremental cost of additional storage for each additional kWh.


Flow battery systems are modular and power modules can be mass-produced with cost-effective manufacturing techniques. Materials used, including polymers and carbon for electrodes, are ethically sourced and easily recyclable. The manufacturing cost per kW of a flow battery is much lower than for other battery types, such as lithium-ion, both in terms of absolute cost and also in terms of energy used per kW or kWh of battery. In a recent paper, S. D. Kurland estimated that 55-65kWh of energy was required to manufacture a kWh of a lithium-ion battery cell.[1] Because of the configuration of a flow battery, with the electrolytes stored in tanks outside the cells, the energy cost for production of the battery per kWh of storage is much lower and would depend significantly on the choice of electrolyte.


A calculation by researchers from the Korean Institute of Science and Technology describes the energy cost to produce 1kWh of vanadium electrolyte to be approximately 1kWh.[2] The energy cost for the production of the stacks is low, involving relatively simple manufacturing processes such as injection moulding for plastic components and casting and machine of steel endplates. Although the batteries will have membranes, which may require energy-intensive actions, the stack cost is related solely to the power of the system and not the energy content.[3] Flow batteries exhibit significantly extended cycle lifespans, with certain models exceeding 20,000 cycles and 20 years, with limited degradation and drop in performance.[4]


Several authorities, for example South Korea, have increased support for non-lithium-ion battery storage to reduce fire risk.[5]



Flow batteries are most suited for longer-duration storage – in excess of 4 hours. Some types of flow batteries (e.g., zinc-bromine batteries) are appropriate for typical discharge durations of say 2 – 4 hours.  Currently, many flow battery manufacturers are packaging flow battery systems to meet the current market need for 4 – 8 hours.  However, flow battery technologies, such as those based on the all-vanadium technology, iron chrome, or organic systems would be perfectly suitable for application in the 8 – 24 hour or longer range.



The technology readiness levels (TRLs) of the flow battery technology span from 4 to 9, varying based on the particular chemistry employed. Vanadium flow batteries and zinc-bromine flow batteries are the most developed technology that is available on the market and reaching TRL 8-9.[6] Recently, other chemistries have been commercialised too (reaching TRL8-9). Iron-chrome, which was successfully deployed in a demonstration project in California in 2014,[7] has seen a renaissance with at least two new separate companies developing commercial projects. The all-iron system is also being deployed by a US company, in association with local partners in Australia.[8],[9]


Organic flow batteries, currently at TRL 4-5,[10] offer sustainability with readily available materials. Emerging chemistries are very promising, using non-corrosive substances like iron sulfates, lignin, or bio-polymers. This reduces environmental impact and enables safe large-scale deployment. Organic redox compounds are abundant, and their characteristics, such as solubility, conductivity, and electrochemical reversibility, can be fine-tuned by introducing specific functional groups.


5. How well developed is the UK industry across different storage technologies, such as hydrogen or redox flow batteries? How does the UK compare to global competitors in these industries?


The UK is home to considerable expertise in flow battery technology, which operates in conjunction with European and international partners. The UK has a number of flow battery companies, including Invinity, Stor-Tera, and RFC Power.  It is also home to several important suppliers of materials and components, for example Oxkem. However, this is a small number compared to the range of companies in Europe, the Far East and the USA. At the academic level, many universities have a strong flow battery research base, and there is much cross-border activity. The UK flow batteries researchers’ community is gathered in the UK RFB Network, which is organising annual meetings.[11] In Europe, there's FLORES, a network of Flow Battery Research Initiatives funded by the EU, uniting researchers from 89 organisations.[12]


The Asia-Pacific region dominates global flow battery usage, primarily driven by China, which leads in both consumption and technology due to abundant vanadium resources. However, with greater support from the UK Government, the UK has the potential to lead in research and industrial capacity within Europe. Particularly taking into account ongoing impressive flow battery projects in the UK (Invinity delivered a 5 MWh vanadium flow battery in Oxford; and has other projects with Scottish Water. Between 2014 and 2021, the UK was among the leading countries in terms of investment in flow battery technology, as indicated in Figure 1. This facilitated the development of a robust flow battery community in the UK and promoted research advancements. However, the UK is lacking in manufacturing capacity, China, Japan, South Korea, Canada, and the USA all have large scale flow battery factories and are well placed to ramp up production to meet future market needs.


Figure 1. EU support to the projects developing flow batteries in 2014-2021

Source: JRC based on CORDIS data from Batteries for energy storage in the European Union: status report on technology development, trends, value chains and markets: 2022.


6. Beyond the cost of deploying long-duration energy storage, what major barriers exist to its successful scale up?


Our members’ concerns, beyond the cost of deployment and the lack of financial incentives, centre on the following challenges:


Comparison of Returns: The primary barrier is the comparison of returns between short-and long-duration storage. High return on investment projects tend to attract capital expenditure, which can discourage investment in long-duration storage.


Impact on Technical and Commercial Performance: The growing number of energy storage assets affects both the technical and financial aspects of the power system. As more batteries are added, the individual value of each new storage system diminishes, affecting financial forecasts. This pertains to the financial projections made by energy sector stakeholders like investors, utilities, and policymakers. The reduced value of each new storage system due to its proliferation can make it harder to gauge the return on investment for new projects, as their value gets diluted in a saturated market.


Flattening of Price Curve: Large-scale storage assets seeking to capture surplus energy at low cost can drive up market prices when purchasing energy and drive prices down when releasing it. While this is good for consumers and the overall system, it can dis-incentivise investors due to reduced value in intemporal arbitrage.


Future Problems with Momentary Reserve: As traditional power plants phase out, a challenge arises with ultra-short frequency regulation. This regulation relies on the inertia of traditional generators, which renewable sources lack due to their use of power electronics. Unlike traditional generators, renewables like solar panels and wind turbines convert DC to AC using power electronics (inverters). While they can adjust frequency, they may struggle with rapid power changes.


Skilled workforce: There are insufficient training schemes in place to ensure the UK has the workforce to deliver the energy storage the grid will need.


Own asset class for energy storage: Energy storage, especially flow batteries, offers a spectrum of grid services, encompassing both slow functions like peak shaving, power balancing, and investment deferral, and fast services like sag compensation, power smoothing, and grid stabilisation. To accurately assess their value and revenue potential, energy storage should have a distinct asset class, separate from consumption and generation. This classification would enable regulators and market participants to develop tailored rules and tariffs that account for the distinctive features of energy storage systems.


7. What steps should the Government take now to ensure this storage can come online later in the current decade?


To address the needs of high TRL flow battery technology, the Government should set the incentives for investors and help to determine the attractiveness of entrepreneurship and the openness of markets. We commend the Longer Duration Energy Storage Programme by DESNZ which is supporting flow battery demonstations. Carefully targeted support for LODES technology types gives confidence to investors to jump the first financial hurdles in deploying a new technology type. Various types of finance should be applied (including grants, concessional loans and equity financing) to bridge gaps and help entrepreneurs to scale up.


Lower TRL flow battery technology could develop faster if the Government prioritise relevant research topics and fund or co-fund projects to test pre-commercial technologies. More funding of flow battery pilots and demonstration projects is needed. This would raise public expectations and confidence in the technology.



Numerous governments have conducted comprehensive assessments of long-duration energy storage deployment, offering valuable insights.[13] Our attention is directed towards the following noteworthy recommendations and illustrative examples:

  1. The key change required is that all power projects, including renewables, must be capable of autonomously balancing and scheduling power. This means no renewable project can proceed unless it's connected to storage representing e.g., 20% of its capacity, plus 5 to 8 hours of storage for dispatchability. Policies in Germany (NRW) and 23 Chinese provinces since May 2023 promote such pairings, with subsidies and a shift toward state-owned enterprises accessing low-interest project financing. State-owned enterprises can accept higher project risks and lower economic returns. [14]
  2. When implementing a long-duration energy storage solution, it is imperative to give careful consideration to safety parameters to ensure the protection of both people and assets. China has banned the use of ternary batteries (retired EV batteries) in large-scale energy storage applications. This move comes in response to notable safety concerns, prompted by a series of incidents involving explosions and fires within China. Tragically, these incidents resulted in the loss of three lives and inflicted injuries on at least 19 others.[15]
  3. The Government should offer a variety of energy storage structured incentives to promote the deployment of energy storage systems. State incentives can function as "transitional funding" until energy storage becomes more cost-competitive within established markets. Finally, the Government should regularly review and update its incentive programs to reflect changing market conditions and the availability of federal tax credits for energy storage. Incentives programmes were successfully implemented in different US states, and included such instruments as rebates, performance payments, grants, storage as efficiency, state tax credits, and others.[16]


Below we compiled a selection of the most impactful flow battery projects from across the world. These initiatives, implemented in critical infrastructure settings, not only demonstrate the technology's maturity but also underscore its recognized advantages.


Project in the UE: In October 2021, CellCube (Austrian-based global flow battery producer) delivered a vanadium flow battery of 200kW rated AC power and 400 kWh capacity to the microgrid project. The objective was to meet the rising demand for decentralized flexibility, enabling the integration of additional renewable energy sources such as solar rooftops while simultaneously satisfying the local peak demand driven by EV chargers.


Project in the US: In November 2022 the US Army base, Fort Carson began the construction of the flow battery system which will provide a 1MW/10MWh long-duration energy storage. This pilot project will empower Fort Carson to diminish its reliance on grid electricity during peak hours, thereby reducing electricity expenses and relieving pressure on the grid. Furthermore, in the event of grid failures, the flow battery will provide essential must-run and backup power to the fort for up to 10 hours. The electrolyte chemistry for this project wasn’t revealed, although it is known that this is not a vanadium or zinc-bromide flow battery. The flow battery project at Fort Carson is planned to conclude construction by late 2023.[17] Should the new system prove successful, this pilot project will facilitate the implementation of more long-duration flow battery storage systems.[18]


Project in China: In November 2022, after 6 years of planning, construction, and commissioning, the world’s biggest vanadium flow battery of 100MW/400MWh in capacity, was successfully put into operation in Dalian city, northeast China.[19] The goal is to increase the efficiency of using renewable energy and maintain grid stability. It is providing peak-shaving on the Dalian peninsula. The new system intends to meet the electricity needs of 200,000 residents daily.[20] In the upcoming phases, there are plans to double the system's capacity.


Projects in Australia: The Queensland government is evaluating different flow battery technologies and is investing at least $24 million. In June 2023 was announced that Redflow will supply 4 MWh of zinc-bromine flow batteries to Energy Queensland, while Energy Storage Industries – Asia Pacific (ESI) will provide 5 MWh of iron flow batteries. Furthermore, the Australian Vecco Group will collaborate with Sumitomo Electric, a Japanese manufacturer, will provide a 250 kW/750 kWh vanadium flow battery to Energy Queensland. These projects are part of Energy Queensland's effort to diversify its battery program away from lithium batteries, to support the state's transition to 80% renewable energy by 2035.[21] Additionally, the European battery energy storage systems supplier CellCube, is in preparation of a vanadium flow battery manufacturing and assembly facility in Australia. This facility is projected to have a capacity of up to 1 GW/8 GWh per annum.[22]


Project in Japan: In April 2022, the HEPCO Network in Abira-cho, Hokkaido, initiated the operation of a grid storage system consisting of approximately 40 flow battery facilities. This impressive system has a total capacity of 51 MWh (17 MW for 3 hours) and ranks among the world's largest redox flow battery installations. To address the challenges of output variations in renewable energy generation, many renewable energy companies had previously installed on-site storage batteries. However, the HEPCO Network installed these large storage batteries on the grid side, which offers economic advantages by reducing the need for individual power providers to install their own batteries. This approach also reduces the operational load for power providers, as they don't need to manage output variations.[23]


11 September 2023


[1] Kurland, S. D. (2019). Energy use for GWh-scale lithium-ion battery production. Environmental Research Communications, 2(1), 012001.

[2] Heo, J., Han, J. Y., Kim, S., Yuk, S., Choi, C., Kim, R., ... & Kim, H. T. (2019). Catalytic production of impurity-free V3. 5+ electrolyte for vanadium redox flow batteries. Nature communications, 10(1), 4412.

[3] Price, A. (2020, April 21). A technology ahead of its time: The emerging world of flow batteries. Bestmag, (68). https://doi.org/https://www.bestmag.co.uk/technology-ahead-its-time-emerging-world-flow-batteries/

[4] Woolery, M. (2021, May 8). Solving the Technical and Economic Challenges to Reprocessing VRFB Electrolyte. US Vanadium. https://usvanadium.com/solving-the-technical-and-economic-challenges-to-reprocessing-vrfb-electrolyte/

[5] Huh, Jeehyang, South Korean energy storage market opportunities, Proceedings of the IFBF 2023

[6] European Commission, Joint Research Centre, Bielewski, M., Pfrang, A., Bobba, S. (2022). Clean Energy Technology Observatory, Batteries for energy storage in the European Union: status report on technology development, trends, value chains and markets: 2022, Publications Office of the European Union. https://data.europa.eu/doi/10.2760/808352

[7] Harrington, K. (2014, July 22). World's Largest Iron-Chromium Flow Battery Starts Up in California. https://www.aiche.org/chenected/2014/07/worlds-largest-iron-chromium-flow-battery-starts-california

[8] Colthorpe, A. (2021, February 15). All-iron’ flow battery maker ESS Inc launches ‘configurable’ megawatt-scale product. Energy Storage News. https://shorturl.at/aMVW8

[9] Waterworth, D. (2022, October 27). Iron Flow Batteries To Be Built In Queensland. Clean Technica. https://shorturl.at/bmGSW

[10] European Commission, Joint Research Centre, Bielewski, M., Pfrang, A., Bobba, S. (2022). Clean Energy Technology Observatory, Batteries for energy storage in the European Union: status report on technology development, trends, value chains and markets: 2022, Publications Office of the European Union. https://data.europa.eu/doi/10.2760/808352

[11] UK Redox Flow Battery Network. UK RFB Network - Symposium - Jul 2022 (google.com)

[12] Mebattery. https://mebattery-project.eu/news/mebattery-project-in-flores-the-european-network-of-flow-battery-research-initiatives

[13] Sandia National Laboratories (SNL), Clean Energy States Alliance (CESA), (2023). McNamara, W., Passell, H., & Olinsky-Paul, T. States Energy Storage Policy. Best Practices for Decarbonization. https://www.cesa.org/wp-content/uploads/State-Energy-Storage-Policy-Best-Practices-for-Decarbonization.pdf

[14] Bian, L. (2023). China’s role in scaling up energy storage investments. Energy Storage and Saving, 2(2), 415-420.

[15] Crompton, P. (2021, June 21). China on verge of banning large-scale ESSs using second-life lithium-ion batteries. Bestmag. https://www.bestmag.co.uk/china-verge-banning-large-scale-esss-using-second-life-lithium-ion-batteries/

[16] Sandia National Laboratories (SNL), Clean Energy States Alliance (CESA), (2023). McNamara, W., Passell, H., & Olinsky-Paul, T. States Energy Storage Policy. Best Practices for Decarbonization. https://www.cesa.org/wp-content/uploads/State-Energy-Storage-Policy-Best-Practices-for-Decarbonization.pdf

[17] Newcomb, T. (2023, January 3). The Army Has a New Flow Battery. It Could Change Military Power. Popular Mechanics. https://www.popularmechanics.com/technology/infrastructure/a42387838/flow-battery-army-testing/

[18] Colthorpe, A. (2022, November 9). US Army breaks ground on Lockheed Martin flow battery pilot. Energy Storage. https://www.energy-storage.news/us-army-breaks-ground-on-lockheed-martin-flow-battery-pilot/

[19] Santos, B. (2022, September 29). China connects world’s largest redox flow battery system to grid. Pz Magazine. https://www.pv-magazine.com/2022/09/29/china-connects-worlds-largest-redox-flow-battery-system-to-grid/

[20] Phiddian, E. (2022, September 30). World’s biggest flow battery opens in China. Cosmos Magazine. https://cosmosmagazine.com/technology/flow-battery-china/

[21] Carroll, D. (2023, August 2). State taps local companies to test out flow battery technology. Pv Magazine. https://www.pv-magazine-australia.com/2023/08/02/state-taps-local-companies-to-test-out-flow-battery-technology/

[22] Carroll, D. (2022, November 24). CellCube eyes Australia for 8 GWh flow-battery manufacturing facility. Pv Magazine. https://www.pv-magazine-australia.com/2022/11/24/cellcube-eyes-australia-for-8-gwh-flow-battery-manufacturing-facility/

[23] Sumitomo Electric (n.d.). Hayakita Substation, Hokkaido Electric Power Network. The meaning in introducing grid storage batteries. https://sumitomoelectric.com/id/project/v19/04