|Vanadium and Batteries|
Clean, renewable energy technologies such as electric cars, and wind and solar power generation continue to grow across global markets. However, the existing grid was never designed to handle the intermittent power supplies inherent with these clean energy sources. An efficient way to store the surplus of energy while making large amounts available at a moment’s notice has been a crippling hurdle. Renewable energy’s greatest challenge is Vanadium’s greatest opportunity. The solution lies in the unique properties of vanadium that make it the battery supercharger. Vanadium is now making cars go farther faster and delivers the solution to mass clean energy storage systems.
Vanadium in Car Batteries
In mobile battery applications, namely car batteries for use in electric and hybrid vehicles, vanadium is being added to various lithium-based battery technologies to produce a car battery that can store more energy (which translates into a greater distance travelled on a single charge), provide more power (which translates into more torque) and can be recharged faster.
At present, the lithium-Vanadium-phosphate combination is regarded by some as the best chemistry due to the advantage it has over all other existing lithium-based chemistries, (particularly lithium-cobalt batteries, the standard type of chemistry you have in your laptop) because of its ability to produce the highest energy density and voltage. This means they can store more energy than similar chemistries such as Manganese Oxide and are very good at producing power and producing it safely (Figures 1 and 2). Coupled with the fact that lithium-Vanadium-phosphate is cheaper than alternatives such as lithium-cobalt, many researchers and analysts consider this chemistry to be a very real contender for the next generation of automotive batteries. Research and development sources say the amount of Vanadium used relative to lithium in these batteries is a 1:1 ratio.
The Latest Breakthrough
One of the most compelling break-throughs illustrating how Vanadium, when combined with lithium, creates “supercharged” batteries is the recent news by Germany’s DBM Energy. In partnership with German utility Lekker Energie, DBM Energy equipped an Audi A2 electric vehicle with its new lithium-Vanadium metal polymer battery and set a long distance record of 603 kilometres (375 miles) travelled on a single charge. The battery’s basic electro-chemistry consists of a metallic lithium anode and a Vanadium oxide cathode. DBM Energy claims the battery has 97% efficiency and can be charged at virtually any electrical socket. Plugged into a 240-volt direct-current source, the battery can be fully charged within 6 minutes.
There are now several companies that have announced that they are developing and in some cases, soon producing lithium-Vanadium-phosphate batteries:
Vanadium in Storage Batteries
Vanadium is poised to play a pivotal role in the commercialization of renewable energy. Renewable energy’s biggest challenge has been the absence of efficient mass storage. To include a high percentage of renewable energy (which is intermittent at best) into the power grid, you need reliable storage. Right now, any unused renewable energy that is not used immediately is lost.
With the recent nuclear incidents in Japan and the on-going conflicts in Libya and the Middle East, countries are already re-examining their power generation options and seeking out alternatives to nuclear energy and ways to reduce their dependency on fossil fuels. Coupled with reliable storage, renewable energy is one of the obvious choices – it is free, it is abundant, and it is carbon neutral.
It turns out that renewable energy’s greatest challenge is Vanadium’s greatest opportunity. A Vanadium-based battery called the Vanadium Flow Battery (VFB) is regarded as one of the leading energy storage systems. VFBs store energy and can be adapted to meet specific energy storage and power demands.
Advantages of the VFB
The VFB is chemically and structurally different from any other battery. It has a lifespan of tens of thousands of cycles, does not self-discharge while idle or generate high amounts of heat when charging, can charge and discharge simultaneously, and can release huge amounts of electricity instantly – over and over again.
The VFB is the only battery technology today capable of powering everything from a single home (kilowatt hour capacity) right up to the storage demands of a power grid (megawatt hour capacity) to help smooth out the unpredictable flow of energy generated by wind turbines and solar panels.
How a VFB Works
A Vanadium Flow Battery is an assembly of power cells: 2 vanadium based electrolytes (liquids that conduct electricity) separated by a proton exchange membrane such as graphite. In solution, Vanadium's 4 positive valence states (+2 through +5) make it an excellent electrolyte for use in energy storage media. In the Vanadium Flow Battery, one tank has the positively charged Vanadium ions in two valence states (V4+/V5+) floating in its electrolyte. The other tank holds an electrolyte full of different Vanadium ions in two valence states (V2+/V3+). It is the electron differential between the two cells that generates electric power. When energy is needed, pumps move the ion-saturated electrolyte from both tanks into the stack, where a chemical reaction causes the ions to change their charge, creating electricity. It is the Vanadium pentoxide (V2O5) resulting from this process that effectively stores the energy.
To charge the battery, electricity is sent to the Vanadium battery's stack. This causes another reaction that restores the original charge of Vanadium ions. The electrical energy is converted into chemical energy stored in the Vanadium ions. The electrolytes with their respective ions are pumped back into to their tanks, where they wait until electricity is needed and the cycle is started again.
Unlike other competing flow battery systems (such as zinc-bromide), a very high number of charges and discharges can occur in a VFB system without any significant decrease in capacity. The VFB has an 87 percent energy efficiency and its energy-holding electrolyte operates at room temperature and never wears out, making the VFB a Green energy storage system.
VFBs are unique in their ability to meet specific energy storage and power demands of almost any size. Because the electrolyte that stores the energy in a VFB is housed in external tanks, it allows power and energy density to be scaled up independently of each other. In other words, want to store more power? Just increase the size of the tanks. As a result, a VFB can meet a wide range of power requirements from kilowatt-hour capacity to megawatt-hour capacity, making the upper limit of the energy-to-power ratio of a VFB virtually unlimited.
This makes the VFB a very adaptable energy storage system, with kilowatt capacities ideal for residential and commercial applications and megawatt capacities for the power grid and stand-alone storage systems for solar/wind farm installations.
Another unique attribute of a VFB is the fact that the electrolyte is stored externally from the battery’s electrode or cellblock, which prevents the self-discharging that occurs in other battery systems.
Key Advancements in the VFB to Reduce Size and Cost
Researchers at the U.S. Department of Energy’s Pacific Northwest National Laboratory have increased the VFBs energy storage capacity by 70 percent and expanded the temperature range in which they operate to between 23 and 122 degrees Fahrenheit (-5 to 50 Celsius) from between 50 and 104 degrees Fahrenheit (10 to 40 degrees Celsius). This noteworthy advancement means that smaller tanks can be used to generate the same amount of power as larger tanks filled with the old electrolyte and greatly reduce the need for costly cooling and heating systems. Researchers believe this advancement could significantly reduce the size and cost of the VFB.