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Energy Storage

Vanadium Flow Battery Benefits For Our Future

An Interview with Professor Roberts

Dr. Ted Roberts is an internationally recognized expert and innovator in the field of electrochemical technology. He completed his BA (1987), MEng (1988), and PhD (1992) at Cambridge University. Prior to moving to Calgary in 2012, he was a professor at the University of Manchester in the UK, and he is a founder of a successful spin-out company, Arvia Technology Ltd. 

His work has been recognized through several international awards for innovation (the IChemE Water Innovation Award, the IET Innovation Award, and the ACES European Academic Enterprise Award). He is the holder of 22 granted patents, has a further 20 patent applications pending, and has published more than 100 papers in international journals. 

Professor Roberts, thank you for joining us!

Since you are an expert in the field of electrochemical storage technology, we wanted to ask you some questions to understand the technology and its prospects better. So, first, let’s start with

  1. What is electrochemical storage technology?

Electrochemical energy storage devices, commonly known as batteries, store electrical energy in chemicals. Electrochemical devices such as batteries allow the conversion of electrical energy into reactive chemicals, and vice versa. Thus, when a rechargeable battery is charged, electrical energy is converted into chemical energy stored in the battery, and when the battery is discharged, the chemical energy is converted back into electrical energy. 

  1. How does electrochemical storage technology relate to vanadium flow batteries?

Vanadium flow batteries are a type of battery (called a redox flow battery) that stores the chemical energy in liquids that are pumped through the battery when it is charged or discharged. As implied by the name, the chemical energy is stored in vanadium in a number of different forms, which are dissolved in acidified water. 

  1. How does an electrochemical cell produce energy?

Electrical energy requires electrons, and in the electrochemical cell, electrons are transferred from the chemical species to the batteries’ terminals (the electrodes). After a vanadium flow battery is charged, on one side of the battery, the vanadium species have an excess of electrons (at the negative electrode of the battery), and on the other side, the vanadium ions have a shortage of electrons. Thus, when the circuit is completed by connecting the battery’s terminals to each other via an electrical load (e.g., a light bulb, or an electric heater), electrons are pushed from the vanadium species at the negative electrode (which have an excess of electrons) through the circuit to the positive electrode, where they are pulled out by the vanadium species that have shortage of electrons.

  1. What are some factors that influence the performance of vanadium flow batteries and how can these factors be used as an advantage for our future?

A battery can be sized based on two factors: 1) the power that the battery can produce (kW) and 2) the capacity, or amount of energy stored (kWh or kJ). The capacity can also be characterized by the duration of the battery discharge (minutes/hours). The performance of the battery can be characterized by several factors, such as: 

  • The round-trip efficiency: the ratio of the energy recovered during battery discharge to the energy used during charging of the battery.
  • The cycle life: how many times can the battery be charged and discharged before it begins to lose its energy storage capacity.
  • The energy density (kWh/kg): the ratio of the amount of energy stored to the weight (or volume) of the battery.
  • The power density (kW/kg): the ratio of the amount of energy stored to the weight (or volume) of the battery.

An advantage of the vanadium flow battery is that unlike conventional batteries, which store the chemicals inside the battery, the capacity of the battery can be sized independently of the power, simply by having larger tanks for the vanadium where the energy is stored. Vanadium batteries have relatively low energy density, but very long cycle life, and they are also easily recyclable. These advantages make them well suited for applications involving stationary storage of electricity, such as storing solar energy during the day for use after dark. 

  1. How are vanadium flow batteries expected to transform the way energy is stored and generated around the world?

Vanadium batteries will enable more efficient use of electricity by enabling better matching of supply and demand. This will enhance the efficiency and utilization of renewable generation such as solar and wind, as well as conventional generation from fossil fuels and nuclear power. Vanadium flow batteries will likely be used in residential, commercial and industrial buildings, as well as integrated into electricity supply networks. 

  1. Can we talk about the difference between vanadium flow batteries and lithium? There is a lot of confusion between these two technologies. Lithium seems to be the best technology for applications in mobility. What do you see the space for vanadium flow batteries to be?

Lithium batteries are a mature technology — compared to other batteries, they have high energy density and are thus light weight and suitable for portable electronic and transport applications. Vanadium flow batteries have a lower energy density, so are better suited to stationary applications, where the battery does not need to be moved. Lithium batteries store the chemical energy inside the battery electrodes, so to increase the battery capacity, you essentially need more batteries. 

Typically, lithium batteries will discharge at their rated power within a few hours at most. In contrast, vanadium flow batteries can easily be designed with larger capacity (>5 hours) by increasing the size of the tanks used to store the vanadium solutions. Another issue with lithium batteries is their limited cycle life: over time, their performance deteriorates, especially if they are operated at high discharge rates, or deeply discharged. In contrast, vanadium redox flow batteries have a much longer cycle life, and they can be fully discharged without affecting their performance. They are also more easily recycled, and the vanadium solutions can easily be reused at the end of the battery life. Currently, vanadium flow batteries are more expensive than lithium batteries. However, in the long term, the cost of flow batteries can work out cheaper. Lithium batteries are also a more mature technology, and with time, vanadium batteries will become more competitive for stationary energy storage applications. 

  1. Can regional electrical grids integrate intermittent generation sources, such as wind and solar power, without energy storage?

There are other methods to manage intermittent generation on electricity grids without energy storage. One option is to have additional generating capacity, such as gas turbines, available to top up energy supply when demand is greater than supply, either during periods of high demand or when wind and solar generation rates are low. Another strategy is to use large networks, so that regions with excess supply (e.g, where the wind generation is high, or electricity demand is low) can support regions where demand is high or supply is low (e.g., when wind generation is insufficient due to low winds). 

Demand management can also be used — for example, offering domestic and industrial users lower prices at times when there is an excess of supply available. With increasing use of electric vehicles, managing demand for vehicle charging could also be used, and vehicle batteries could also be used as an energy storage resource on electricity networks. Depending on the circumstances, energy storage may be lower cost, offer higher efficiency, and reduce the overall environmental impact, when compared with having additional generation or building larger networks. In practice, it is likely that a combination of energy storage with other options will be used in most circumstances. 

  1. The University of Calgary purchased a vanadium flow battery from StorEn*. Which work will your group perform with the battery?

We plan to use this battery to support our research on vanadium flow battery technology and its integration for electricity supply. We will use the battery to test the scale up of new battery materials technologies that have shown promise at laboratory scale for enhancing vanadium flow battery performance. We are also studying vanadium extraction and purification, and evaluating the impacts of impurities on flow batteries, with the aim of reducing the cost of the vanadium solutions. With this battery, we will be able to demonstrate that lower cost processing routes can be used to produce vanadium solutions that work effectively in the battery. The battery will also be integrated with solar panels, to evaluate battery control technology and the use of lower cost electrical hardware to connect the battery with renewable generation

  1. Can you make any (unbiased) predictions for the future of vanadium flow batteries and their potential for technological advances? 

With the increasing implementation of renewable generation, there is a rapidly growing market for stationary energy storage. Based on the advantages discussed above, vanadium flow batteries are expected to play an increasing role in these applications during the coming decades. The cost of the technology is reducing, and this will be essential for the application of vanadium flow batteries. Reducing cost can be achieved by innovations in battery design and materials to enhance performance and reduce the size and cost of the battery. A secure supply chain for lower cost vanadium suitable for the flow battery technology is also needed.

  1. The battery the University of Calgary purchased from StorEn is the same size as their residential battery. StorEn managed to package this technology in a small scale for residential applications. Do you see any advantages to use vanadium in place of lithium in a residential setting

One concern with lithium batteries is the fire hazard they can present. Vanadium flow batteries are safer, as the energy is stored in water, and so there is no fire risk. In addition, the reliability and stable performance, including with deep discharge, is another advantage for residential applications. The design of small-size vanadium flow batteries with storage capacity of 5 hours or more will likely be attractive for residential applications, especially for integration of local solar generation.

  1. The vanadium electrolyte is reusable — what are the impacts on sustainability and the mining industry?

As mentioned above, vanadium electrolyte is reusable, and the other battery components can also be easily recycled by well-established routes. Vanadium flow batteries are more sustainable than other battery technologies, which are typically difficult to recycle, recycling processes are still under development. Although vanadium electrolyte is reusable, increasing implementation of vanadium flow battery technology will create additional demand for vanadium resources. Currently, vanadium is produced as a by-product of steel production, and the main application for vanadium is in steel alloys. The vanadium price is volatile due to fluctuations in supply and demand, unrelated to the availability and cost of vanadium production. As mentioned above, there is a need for a supply chain for vanadium flow batteries. There is an opportunity to develop a vanadium mining industry targeting production of vanadium for use in flow batteries. There are also wastes that contain significant amounts of vanadium, such as fly ash from combustion of heavy oils, that could easily be processed to produce vanadium for flow batteries. 

Thank you for your time! 

You can learn more about Professor Roberts here.

To learn more, visit

StorEnTech takes what vanadium batteries already promise – durability and sturdiness – and uses extensive R&D to focus on improving the electrical efficiency of the stack, the energy density of the electrolyte, and the module. Through these processes, the company creates efficient, powerful, environmentally friendly batteries.

*This article is supported by StorEn Technologies. 

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