Vanadium redox-flow batteries was introduced as an ambiguous project for research at the PNNL (Pacific Northwest National Laboratory), the United States Department of Energy lab in Washington State. The team of PNNL associated in the year 2007 when the oil prices across the globe were increasingly ascending. Moreover, certain economies including India as well as China were exhibiting the growth at double digit that was making environmentalists more anxious since these countries were consuming fossil fuels at accelerating rate. However, populace of the United States was getting

Vanadium redox-flow batteries was introduced as an ambiguous project for research at the PNNL (Pacific Northwest National Laboratory), the United States Department of Energy lab in Washington State. The team of PNNL associated in the year 2007 when the oil prices across the globe were increasingly ascending. Moreover, certain economies including India as well as China were exhibiting the growth at double digit that was making environmentalists more anxious since these countries were consuming fossil fuels at accelerating rate. However, populace of the United States was getting aware regarding the usage of renewable but intermittent sources of energy sources such as wind as well as solar.

In contradiction to that framework, it was decided by the team of researchers to investigate a better method for storing the renewable energy as a means of encouraging its adoption while refining grid consistency as well. Moreover, the group of researchers included top experts of power, materials as well as chemistry present in the lab, and also a proficient lawyer of property, who had a power engineering background. The power engineer who is also a lawyer in the team enabled them in focusing on technologies that might have the utmost impact on the society. They also started receiving the support of DOE’s Energy Storage Program in 2009 that enhanced their research & development budget annually to arrpox.US $10 million.

When the study was at its starting phase it wasn’t at all expected that the flow batteries could the way ahead in upcoming years. Certainly, investigation was started by studying all of the other battery technologies available in market, for instance sodium sulfur, redox flow, lithium ion, advanced lead acid and other new models.

Lithium-ion batteries

Further, as per a survey it was found that high-power lithium-ion batteries were used by a large number of people in the U.S. between 2015 & 2016. The technology has been gradually advancing because of the fierce work on batteries used in electric vehicles as well as mobile devices, like laptops, tablets & smartphones for several decades. For instance, Tesla’s Powerwall, is designed for storing energy in both residential & business complexes, however it basically utilizes a similar ­Li-ion cells as used in company’s electric cars.

Then for applications of grid-scale the study was pointing the major shortcomings of lithium ion that included:

• For making battery packages capable of stowing megawatt-hours needs several thousands or sometimes millions of Li-ion cells and each of that necessities to be managed separately and communally along with other cells. Then also Li-ion batteries are capable of supplying power only for short durations that ranges typically around 2 hours or less. Thus, it was concluded that in order to create a battery for longer-duration power supply, manufacturers might have to produce thicker electrodes and package them with even more dynamic materials that will probably result in price hike.
• Also, performance of a Li-ion battery lowers over a certain period of time, giving the typical lifespan of around 10 years or less. This might be suitable for a normal family car but then is less appropriate for use on power grid.
• Besides, ­Li-ion batteries have been known for safety related issues that includes a sudden explosion or catching spontaneous fire.

Sodium-sulfur batteries

Sodium-sulfur batteries were once considered most favorable for the utility-scale systems that operates at about 300 °C for liquefying the sulfur & sodium, forming the positive and negative electrodes respectively. Nevertheless, these batteries, also have issues of flammability. For instance, when a 2-MW system in the plant of Joso City, Japan, caught fire in the year 2011, then the producer of battery, NGK Insulators, recollected their products as well as halted production for some time.

Redox-flow batteries (RFBs)

On the other hand, redox-flow batteries (RFBs), provide certain features that are not found in any other battery. Theoretically, these can be effortlessly scaled up to ­megawatt-hours, withstand their enactment over longer periods and are the safest battery type if constructed around fire-resistant materials. Unlike, Li-ion as well as other batteries of solid state that store electricity or even charge in electrodes made up of lively solid materials, RFB functions more like a flexible fuel cell. In order to discharge, RFB takes the stored chemical energy in liquid electrolytes and then converts it into electrical current, retreating the procedure to charge.

Every single flow battery cell has got a negative & a positive side. Depending upon the fact that the battery is in charging or discharging mode, those side might either generate or absorb electrons flowing through an external circuit. These 2 sides are parted by a membrane which selectively permits the protons to traverse. In addition, while charging the battery a voltage applied all over the positive & negative sides’ starts causing vanadium ions in electrolyte that is flowing via battery’s stack of thin as well as plate like cells. This enables to each of it lose an electron on the positive side. This autonomous electrons cross outside the circuit to reach the negative side, stowing electrical energy. Throughout the discharging process, collected electrons on negative side flows back via external circuit and are absorbed on positive side, freeing stowed electrical energy.

The very first redox-flow batteries was developed at starting of the year 1970 by Lawrence Thaller & his associates at NASA, as a probable source of energy for the deep space missions. They utilized a solution of iron on positive side and a solution chromium on negative side. However, the usage of unlike components directed to cross-contamination, as iron & chromium ions inclined for diffusing all across the membrane splitting these 2 solutions.

Then the middle of the year 1980, Maria Skyllas-Kazacos and her associates at the University of New South Wales, in Sydney, revealed an enhanced RFB that was using same element—vanadium on both the sides of battery, thus avoiding the risk of contamination.

Vanadium is a rich silvery-gray metal that belongs the family of niobium & tantalum and is mainly mined in Russia, China, South Africa as well as Brazil. However the initial VRFBs were not capable of storing much energy and could only restore around 12-15 watt-hours/liter of electrolyte. To work any valuable task, the batteries need to be huge like A 1-MW/4-MWh structure that will probably occupy a space equal to 1 or 2 basketball courts.

The vanadium oxide have a tendency to precipitate out from electrolytes causing a steady loss in the battery’s capacity that is another major concern. Moreover, placing the vanadium in solution meant that batteries might function only inside a constricted temperature range, i.e. somewhere between 10-40 °C. Thus, adding equipment for thermal management as well as other electronics for controlling would further cut battery’s overall effectiveness while expanding its size & complexity.

However, the PNNL team believed that the technology had excessive potential. Thus, they determined to develop a fresh electrolyte chemistry, membranes & prototypes.

Lastly, in 2011, they were successful in developing a different vanadium-based electrolyte that depended upon reactions along with a chloride solution. Apparently this simple modification efficiently doubled the density of energy that was better than the existing VRFBs, since a large number of vanadium ions stayed stable in solution, besides maximum of them were accessible throughout the charging & discharging processes.

The subsequent battery had an impression that was 1/3 to 1/5 as big as its prototypes and could also function in an extensive ambient temperature range (from 0 to +50 °C) deprived of added thermal management. Furthermore, several other alterations made the battery even more consistent, simple to manage as well as further tolerant from the impurities of electrolyte.