Swanbarton Limited – Written evidence (LES0034)


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

Long duration energy storage provides an opportunity for the UK to reassess its strategy for energy security against benchmarks such as security of the supply chain for materials and components for energy storage, and the intrinsic security of the operation of the storage.


Although traditionally large scale network storage has been the preserve of pumped hydro, more recently, large scale battery energy storage has become widespread. Other technologies are also suitable, including liquid air and compressed air.


The key features of the most desirable types of large scale energy storage, particularly for use on the power system, are:



Technologies that have separable power ratings to energy storage content, such as flow batteries, liquid air or pumped hydro are well suited in this regard. Some battery types have been designed from the outset to be more suitable for long duration storage, such as sodium sulphur, even though with a single cell structure they do not have the ability to separate power from energy.


We have looked at opportunities for using flow batteries and other storage options in numerous applications. The challenges of scaling energy storage to meet the significant requirements for the nation suggest that it is important to maintain flexibility in design, allow for changes in configuration and needs change and to have the capability to phase investment and upgrade facilities as required. We have witnessed the growth in battery energy storage projects, and the desire for owners and operators to upgrade or refurbish these projects with increased energy storage capacity, that is converting plants from shorter to longer duration energy storage. This can be difficult and expensive with conventional battery cells. Adding additional hours storage to well designed flow battery systems can be relatively simple. Additionally, the extra energy storage capacity does not require a reassessment of the fire risk, and reduces the overall land take, increasing the energy density, and not necessarily the footprint of the project site.


Flow batteries can be configured with electrolyte storage tanks, independent to the power rating of the electrochemical cells, so the same technology can be used for 4 h, 12 h or 24 hours as required because of the versatility of 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.


We explored this concept, considering the use of large-scale tanks (such as those used for oil storage) in a feasibility study for the use of flow batteries in the maritime sector. This is also being considered in Singapore, where underused oil storage tanks might be used for large scale storage of charged vanadium electrolytes. The role of long duration storage as an enabler of electricification in the land based and marine based transport industry is important.


Other advantages of flow battery systems are their modularity. Power modules can be mass-produced with cost-effective manufacturing techniques, with lower energy requirements than many other battery types. 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. This means that the investment cost to manufacture flow batteries is lower than for other systems.



Flow batteries are well suited to longer duration storage, of durations well in excess of 4 hours, and the upper limit set by practical considerations such as the area available for the installation. Other battery types, such as sodium sulphur are economic and viable for duration of around 6 hours.


Flow batteries have low or non existent self discharge rates. We can envisage a flow battery placed in shutdown mode, and isolated, ready to be called upon after a period of rest of weeks or months.



Flow batteries are available on commercial terms now. A Japanese company has been selling installations for more than 20 years, demonstrating high reliability and good performance. Other manufacturers are also able to provide systems on commercial terms.


The most advanced flow batteries are based on the all vanadium system, and the zinc bromine system. Other technologies, such as iron chrome, and hydrogen bromide are also available. Newer technologies, such as those which use organic electrolytes are currently at the demonstration phase, but may be expected to advance rapidly.


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’s flow battery industry has reflected other economic and commercial cycles. We reported in a report for the DTI in 2004 on the “Status of energy storage systemsand included comments on flow batteries and other technologies. One flow battery company named in that report is still in existence (although with several changes in ownership) with a manufacturing base operation in the UK today, and has installed several flow battery projects in the UK and overseas. However there are few other companies with manufacturing in the UK. There are many competitors throughout the world, with companies across Europe, Japan, South Korea, China, South East Asia, the Middle East and the USA and Canada. A recent announcement of flow battery investment in Saudi Arabia demonstrates the perceived importance of the technology.


Our research base is strong. There are notable electrochemical research groups in many UK universities, and there is strong international collaboration within the flow battery research community.


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. The overall need for energy storage is immense, and more than one technology type will be needed. Some energy storage applications, for example, demand technical parameters of high energy density, high power density such as for electric vehicles, and for these it makes sense to allocate production of lithium – ion or similar technologies. But the resources for the materials to produce lithium -ion cells are restricted, with many strategic raw materials. The manufacturing facilities are complex, have lengthy construction timespans and are expensive in comparison to large scale flow battery manufacturing plants. Establishing flow battery manufacturing in the UK would provide additional economic benefit, create viable technology employment and give output to the high quality research currently underway in our research laboratories.


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


Although there is a general awareness of the role of long duration energy storage, there needs to be shift in the enthusiasm of investors to embrace new technology.


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


The Longer Duration Energy Storage Programme by DESNZ which is supporting flow battery demonstations has been successful in creating interest and promoting projects in long duration storage including flow batteries. The next stage is to provide market mechanisms to encourage the commercial development of longer duration storage. We note that it was the introduction of a commercial tender for enhanced frequency response in 2016 that opened up the market for battery energy storage in GB. Even though this was relatively small auction, it precipitated a major change in the approach of investors. We would suggest a similar auction, such as an auction open to long duration and long reserve storage. This storage could be used to provide a small strategic reserve (similar to black start).


Consideration should be given to encouragement of the establishment of large scale flow battery manufacturing, to at least a level of support given to parts of the EV industry.


8. Can the UK learn from other countries that have successful policies for supporting large-scale energy storage, or from pilot projects elsewhere?


The US Department of Energy has invested heavily in a range of storage research activities and is now making project investments under the Inflation Reduction Act. Its research into flow batteries is supporting a wide range of flow battery types, especially organic and non traditional chemistries.


11 September 2023