Vanadium fuels growing demand for VRFBs

Vanadium, which is in high demand today for its ability to strengthen steel alloys – specifically for manufacturing high-strength, low alloy rebar used in earthquake-resistant construction around the globe, as well as automotive, aerospace and military applications – is gradually gaining ground in the renewable energy sector.

The hard, silvery-gray metal is the 22nd most abundant element in the Earth's crust, though it is rarely found naturally in its metallic form. Instead, vanadium can be found in more than 100 different minerals. Once extracted and dissolved in water, various forms of vanadium turn into bright, bold colors. Due to the colors of the various aqueous states, Vanadium was named after "Vanadis", the old Norse name for the Scandinavian goddess of beauty, Freyja.

But the element is not only beautiful but strong. Adding small percentages of it creates exceptionally light, tough, and more resilient steel alloys.

Manufacturers of automobiles and machinery recognized the toughness and fatigue resistance of vanadium alloys as far back as the early 1900s, incorporating the alloys in axles, crankshafts, gears, and other critical components. Vanadium has been used together with aluminum to give the required strength in titanium alloys used in jet engines and high-speed airframes.

Henry Ford first used it on an industrial scale, in the 1908 Model T car chassis, and today the vast majority of vanadium is used in structural steel, mainly to build bridges and buildings.

Recent invention

As the primary element in the vanadium redox flow battery, however, it is attracting a following in green technology.

Today, VRFBs are sparking considerable interest as reliable and clean devices for storing energy, especially from sustainable sources such as wind and solar power.

Also known as the vanadium flow battery or vanadium redox battery, a VRFB is a type of rechargeable flow battery that employs vanadium ions in different oxidation states to store chemical potential energy. The technology exploits the ability of vanadium to exist in solution in four different oxidation state and uses this property to make a battery that has just one electroactive element instead of two. For several reasons, including their relative bulkiness, most vanadium batteries are currently used for grid energy storage, such as renewable energy power generation and grid stabilization.

The possibility of creating a vanadium flow battery has been investigated without success since the 1930s by a number of scientists, including NASA researchers in the 1970s.

But Maria Skylass-Kazacos, a mother of three and chemical engineering and industrial engineering professor at the University of New South Wales in Australia, made a breakthrough with the technology in the 1980s with her design using sulfuric acid electrolytes. The innovation was quickly patented by the University of New South Wales in 1986.

Significant advantages

The main advantages of the vanadium redox battery are that it can offer almost unlimited energy capacity simply by using larger electrolyte storage tanks; it can be left completely discharged for long periods with no ill effects; if the electrolytes are accidentally mixed, the battery suffers no permanent damage; a single state of charge between the two electrolytes avoids capacity degradation due to a single cell in non-flow batteries; the electrolyte is aqueous, inherently safe and non-flammable; and a third generation version of the battery using a mixed acid solution operates over a wider temperature range, which allows for passive cooling.

VRFBs can be used at depth of discharge more than 90%, deeper than solid-state (lithium-based and sodium-based) batteries. In addition, VRFBs exhibit very long cycle lives: most producers specify cycle durability in excess of 15,000-20,000 charge-discharge cycles. These values are far beyond the cycle lives of solid-state batteries, which are usually on the order of 4,000-5,000 cycles. Thus, the levelized cost of energy – the system cost divided by the usable energy, the cycle life, and round-trip efficiency – of present VRFB systems is typically in the order of a few tens of US or euro cents, much lower than comparable costs of solid-state batteries and close to the targets of US5 cents and €5 cents, according to the U. S. Department of Energy and the European Commission Strategic Energy Technology Plan, respectively.

Demand on horizon

The emerging need for large-scale electricity storage makes vanadium redox-flow batteries a major potential future use of vanadium, according to the U.S. Geological Survey.

Due to their large-scale storage capacity, VRFBs could prompt increases in the use of wind, solar, and other renewable, intermittent power sources. Lithium-vanadium-phosphate batteries produce high voltages and high energy-to-weight ratios, which make them ideal for use in electric cars. Vanadium use in lithium batteries is also expected to increase.

The main disadvantages with vanadium redox technology are its relatively poor energy-to-volume ratio in comparison with standard storage batteries, and their relatively poor round-trip efficiency. Further, the aqueous electrolyte makes the battery heavy and therefore only useful for stationary applications. Another disadvantage is the relatively high toxicity of oxides of vanadium.

Yet numerous companies and organizations are involved in funding and developing vanadium redox batteries.

Vanadium is scheduled for evaluation in 2020 by the US government, which included the element in its recent critical minerals initiative.

The extremely large capacities possible from vanadium redox batteries make them well suited to use in large power storage applications such as helping to average out the production of highly variable generation sources such as wind or solar power, helping generators cope with large surges in demand or leveling out supply-demand in a transmission constrained region.

The limited self-discharge characteristics of vanadium redox batteries make them useful in applications where the batteries must be stored for long periods of time with little maintenance, while maintaining a ready state. This has led to their adoption in some military electronics, such as the sensor components of the U.S military's GATOR mine system. Their ability to fully cycle and stay at 0% state of charge makes them suitable for solar-plus-storage applications, where the battery must start each day empty and fill up depending upon the load and weather.

Lithium-ion batteries, by contrast, are typically damaged when they are allowed to discharge below 20% state of charge, so they typically only operate between about 20% and 100%, meaning they are only using 80% of their nameplate capacity.

The extremely rapid response times of VRFBs also make them well-suited to uninterruptible power supply-type applications, where they can be used to replace lead-acid batteries and even diesel generators. Also, the fast response time makes them well-suited for frequency regulation.

Economically neither the power supply nor frequency regulation applications of the battery are currently sustainable alone, but rather the battery is able to layer these applications with other uses to capitalize on various sources of revenue. Also, these capabilities make vanadium redox batteries an effective "all-in-one" solution for microgrids that depend on reliable operations, frequency regulation and have a need for load shifting (from either high renewable penetration, a highly variable load or desire to optimize generator efficiency through time-shifting dispatch).

Second generation vanadium redox batteries also could double the energy density and increase the temperature range in which the battery can operate. A vanadium-bromine and other vanadium-based systems also might reduce the cost of the technology by replacing the vanadium at the positive or negative electrolyte by cheaper alternatives such as cerium, researchers say.

A bright future for VRFBs?

While vanadium has long been used as an alloy material in steel manufacturing, the real potential the metal holds is in its energy storage capabilities in VRFBs, market observers say.

"VRFBs are well placed to operate alongside and in place of lithium-ion batteries, which have generally lower energy capacity and shorter discharge timeframes, but which can discharge faster," SP Angel's John Meyer told investors recently.

SP Angel forecasts that VRFB demand in Southern Africa, alone, could consume more than 5% of global vanadium production over the next few years, creating significant new demand in a market where supply is relatively consistent.

"If this trend is repeated in the U. S., China and Europe, then we can see new demand for vanadium easily outstripping supply in future years, with grid developers queuing to secure available vanadium electrolyte supply," added Meyer, who heads research for the London-based investment banker.

Vanadium is currently at the forefront of technology innovation, yet it is in short supply, observed Adriaan Bakker, president and CEO of VanadiumCorp Resource Inc., a Canada-based company focused on developing an integrated supply chain with its own vanadium mining projects in Quebec, proprietary vanadium extraction technique and VRFB technology.

"To address this (shortage), we recently co-developed a new chemical method that directly recovers vanadium sustainably from virtually any source. With a substantial resource base in Canada and technology to unlock global supply, I believe VanadiumCorp may hold the key to our low carbon future," Bakker said in a statement.

In 2020, VanadiumCorp is targeting commercial production of vanadium batteries, as well as a resource statement indicating that its resource base in Quebec is uniquely suited to meet the needs of the high-purity vanadium market.

VoltStorage Gmbh, a Munich, Germany-based startup, meanwhile, is working to take VRFB technology one step further to bring it to private households as a cost-effective solar energy storage solution. This was made possible by VoltStorage's production process, for which it has a patent is pending.