Scientists at PSI have created a dynamic database for vanadium, an important raw material. This metal has enormous potential for the energy transition. Vanadium redox flow batteries (VRFB) can store electricity for longer than the widely used lithium-ion technology. This makes them particularly suitable for storing surplus wind and solar power in large facilities and feeding it back into the grid at a later time. They can therefore serve as energy buffers, stabilising the power grid and ensuring electricity supply even during a dunkelflaute, a period when neither the wind nor the sun are producing enough electricity. The lack of such storage facilities is considered one of the biggest challenges for the energy transition because the supply of wind and solar power is less steady than that of electricity from coal or gas-fired power stations.
Benjamin Rogers, a PhD student at PSI and ETH Zurich, spent over two years collecting data from all the players in the vanadium industry worldwide – from mine operators to the processing industry – to compile the database. He conducted this work within the team of Sarbajit Banerjee, Head of the Laboratory for Battery Research at the PSI Center for Energy and Environmental Sciences and Professor of Chemistry at ETH Zurich. The database includes information on suspected and confirmed ore deposits from which vanadium could be extracted economically, as well as planned and achieved mining volumes, demand, processing methods and quantities, prices and other relevant key figures. All this data has been incorporated into a kind of "living global map" for vanadium, which is constantly updated to reflect current developments and is available to all industry players – companies, governments and scientists. "It's a matter of creating a reliable basis for making investment and policy decisions," says Rogers, "something that has been lacking until now." As a result of this, the comparatively small vanadium market is still highly volatile: prices fluctuate a great deal, which is why many companies are reluctant to invest in mining it. Consequently, the supply of the metal is not reliably assured.
Market dominance and price volatility
Although there are sufficient vanadium deposits worldwide, the metal was long considered too rare and too expensive to be a comprehensive solution for storing surplus green electricity. Prices have since fallen – but so much so that planned new mines in Australia are on the brink of economic collapse. The main reason for these pronounced fluctuations is market concentration: over 60 percent of the 150,000 tonnes produced annually worldwide comes from China, with the rest being mined almost exclusively in Russia, South Africa and Brazil. Countries such as Australia, Canada, the USA and Kazakhstan also have large reserves, but these have hardly been tapped.
Until now, vanadium has mainly been used to strengthen structural steel alloys. A change in Chinese law following the severe earthquake in 2008 made the addition of vanadium mandatory, causing demand – and prices – to rise sharply. However, the end of the Chinese construction boom led to a drop in prices, which jeopardised mining projects already underway in Australia.
Reliable data on raw materials
"The aim of our project is to avoid such price extremes, thereby allowing vanadium production to become more reliable and sustainable," says Sarbajit Banerjee. A chemist by training, he has been studying this metal for years as a material for cathodes in batteries, catalysts and computer technology. His research group has already given rise to two start-ups in the sector. One is designing vanadium cathodes, the other developing processes for extracting lithium from water using vanadium. "In this respect, we've been well-connected in the scene for quite a time, and everyone recognised the need for a project like ours," Banerjee reports.
The main partner in the development of the database is Vanitec, an association comprising many industry players specialising in vanadium.
To guarantee the reliability of the data, the researchers have it independently verified – as far as possible. "The most difficult part was not obtaining the data," says Rogers, "but harmonising it." The incoming data is based on a wide variety of counting methods and must be standardised to ensure good comparability.
Innovative financing models are needed
Reliable parameters allow large and small companies, investors and policymakers to plan for the long term. This is important not least because it often takes ten or even fifteen years from the discovery of a deposit to the actual extraction and sale of the metal. "Many large mining companies that can afford to bridge this period without investors won't even enter the vanadium market until it reaches a volume of at least 500,000 tonnes per year," says Banerjee.
This is why his team suggests that, in addition to data, innovative financing models are needed. One idea is long-term purchase guarantees. India, which needs a lot of vanadium, could for example promise Australia that it will buy a certain amount per year as soon as the mines there start producing it.
Another option is known as resource leasing which is already common practice for some other metals. The vanadium-mining country "leases out" its vanadium for a set period of time, so to speak. This allows countries that produce natural resources to retain ownership of them, while reducing the buyer's capital investment and risk and ensuring that demand remains stable.
Vanadium in flux: How batteries store energy
Vanadium redox flow batteries store their energy in aqueous vanadium electrolyte solutions – conductive liquids that allow electricity to flow inside the battery. These solutions circulate in large tanks and are fed by a system of pumps into a cell in which the actual energy conversion takes place.
In contrast to lithium-ion batteries, they offer a flexible combination of performance and storage capacity. Their performance depends on the size of the cells, whereas their capacity depends solely on the size of the tanks, which can be expanded at a later date.
One key advantage is that the vanadium can be recovered almost loss-free after use, since it is only present in dissolved form in the electrolyte and over 99 percent of it can be filtered out again. In lithium-ion batteries, the power electrodes and the electrolyte are inseparably connected, which puts a structural limit on their capacity. Also, it takes a lot of effort to extract the lithium from the various components.
Further advantages: Vanadium redox flow batteries are very durable – they achieve up to 20,000 charging cycles without any significant loss of performance and offer a service life of 15 to 20 years or more. Disadvantages include higher costs, taking up more space and lower storage efficiency (energy losses of up to 20 percent). "However, these are more than offset by the advantages, especially in larger storage systems," says Banerjee, "given that losses in efficiency are less of a concern with green electricity than with coal-fired power, for example."
The biggest advantage, however, is that vanadium redox flow batteries are incombustible because of the high water content of the electrolyte. They are significantly safer to operate than large energy storage systems that rely on lithium-ion technology, which is highly flammable by comparison.
The world's largest battery storage facility soon to be completed in Switzerland
Vanadium redox flow batteries are primarily used as large-scale stationary storage systems to stabilise the power grid, particularly in wind and solar parks or for industrial consumers. However, they are also suitable for use in larger residential complexes and for supplying power to data centres, which require more and more electricity – not least due to the rapid expansion of artificial intelligence. The world's largest vanadium redox flow battery plant is currently being built right next door to an AI data centre in Laufenburg, Switzerland. With 960 tanks and 250 million litres of liquid electrolyte, the plant is expected to provide a storage capacity of 1.6 gigawatt hours.
Banerjee and Rogers hope that this example will set a precedent in Europe and that vanadium redox flow batteries will be used more widely to advance the energy transition. "We are at an important junction," says Banerjee. "If we succeed in extracting vanadium efficiently and economically and producing batteries like these in large numbers, this could contribute significantly to a stable, sustainable energy supply." With the new dynamic database, PSI researchers are helping other markets to access the necessary information and utilise the potential of this technology more quickly.
Text: Jan Berndorff
About PSI
The Paul Scherrer Institute PSI develops, builds and operates large, complex research facilities and makes them available to the national and international research community. The institute's own key research priorities are in the fields of future technologies, energy and climate, health innovation and fundamentals of nature. PSI is committed to the training of future generations. Therefore about one quarter of our staff are post-docs, post-graduates or apprentices. Altogether PSI employs 2300 people, thus being the largest research institute in Switzerland. The annual budget amounts to approximately CHF 450 million. PSI is part of the ETH Domain, with the other members being the two Swiss Federal Institutes of Technology, ETH Zurich and EPFL Lausanne, as well as Eawag (Swiss Federal Institute of Aquatic Science and Technology), Empa (Swiss Federal Laboratories for Materials Science and Technology) and WSL (Swiss Federal Institute for Forest, Snow and Landscape Research).
