Vanadium Electrolyte for Grid Scale Renewable Energy Storage

Coupled with reliable storage, renewable energy is one of the obvious ways to reduce the effect of greenhouse gasses on climate change. The world’s energy storage revolution is revving up. In a report by IHS Markit, the global energy storage market is expected to double to 2.9 GWh installed capacity by the end of 2016. Looking past this year, IHS believes grid-connected energy storage capacity will surge to 21 GWh globally by 2025.

Ironstone is poised to become one of the world's major supplier of vanadium pentoxide, a critical component of grid-scale energy storage vanadium redox batteries, with a compliant resource of 2.45 billion pounds of vanadium pentoxide (557 million tonnes indicated at 0.21% V2O5) as reported by SRK Consulting (Canada) in July 2012.

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Energy storage will change the way the power grid operates. The ability to store renewable energy has long been a holy grail for clean energy, and large-scale battery storage is gaining momentum. Costs are coming down, technology has improved, the share of renewable power has increased, private and venture-capital funding has grown, and policy support is emerging, among other indicators. The energy-storage business has the potential to be a $150 billion market within a few years according to Goldman Sachs.

It turns out that renewable energy’s greatest storage 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.

Vanadium's four positive valence states (+2 through +5) that make it such an excellent energy storage media, acting as a supercharger to batteries. 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.

A VFB is an assembly of power cells incorporating two vanadium based electrolytes (liquids that conduct electricity) separated by a membrane. In the VFB, one tank has the positively charged vanadium ions in two valence states (V4+/V5+) floating in its electrolyte. The other tank holds an electrolyte of vanadium ions in two other 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 VFB, electricity is sent to the vanadium battery stack. This causes a 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.

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. Simply increasing the size of the tanks permits more power to be stored.

Unlike other competing flow battery systems, 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 environmentally-friendly energy storage system. 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.

There have been considerable developments in the advancement of vanadium flow battery technology for grid storage applications. These advancements are expected to both reduce the size and cost of the VFB, and in turn, accelerate their implementation on a commercial level. An example of the efforts to commercialize VFBs is the work in Germany to produce a 20 MWh capacity VFB installation that would utilize approximately 33 tonnes of battery-grade vanadium pentoxide and would provide enough energy to supply power to roughly 2000 households for an entire day. The vanadium electrolyte and the membrane are the two most expensive components in a VFB. Together they represent approximately 50% of the cost of the battery. The advancements in the development of the VFBs by leading research institutes across the globe are expected to both reduce the size and cost of the VFB, and in turn, accelerate their implementation on a commercial level.

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