Utility-scale Flow Batteries will make renewable electricity 'dispatchable'
The Vanadium Flow Battery can absorb and release huge amounts of electricity instantly & repeatedy. It's ideal for smoothing out the flow from wind turbines and solar cells
Energy storage: the limiting issue for renewables, until...
The rare earth metal vanadium is on track to provide a breakthrough energy storage solution for the major challenge faced by renewable energy. The intermittent nature of wind and solar power can make these distributed sources difficult for utilities to manage within the electrical grid. Vanadium flow batteries can accommodate renewable energy by storing massive amounts of electricity and releasing it into the grid as needed when demand increases.
Vanadium is most commonly used as an alloying metal for strengthening steel, but it has an energy storage history dating back to the 1970s, and has undergone extensive R & D since then. Vanadium flow batteries (VFBs) use a reversible chemical reaction that allows recharging without replacing the active chemicals. The batteries can also be recharged to 100% of their capacity, as opposed to around 70% for lithium and roughly 35% for lead-based batteries. Increasing the size of the containment vessels that hold the vanadium in a dilute sulphuric acid solution can achieve grid-scale storage. A flow battery installation for mass power storage would look basically like any bulk liquids storage facility.
The need for energy storage
According to the U.S. Energy Information Administration, net electricity generation from all forms of renewable energies in America increased by over 15% in the four years to 2009. Solar and wind made disproportionate market gains—47% for solar net electricity generation gain, and 297% for Wind. Early market gains are continuing to expand. But more wind and solar-generated electricity also means less compatibility with the existing grid, which was designed to generate electricity as needed and to consume it instantly. This is why the Institute of Electrical and Electronics Engineers has recommended:
"If intermittent sources of electric power, such wind and solar, are to reach their full potential to contribute to the nation's power requirements, technologies for large scale energy storage must be developed and deployed."
The vanadium redox flow battery
The promising solution on the horizon is the vanadium redox flow battery. This unusual battery was invented more than 20 years ago by Maria Skyllas-Kazacos, a professor of electrochemistry in Australia. The VFB has a marvellous advantage over lithium-ion and most other types of batteries. It can absorb and release huge amounts of electricity at the drop of a hat and do so over and over, making it ideal for smoothing out the flow from wind turbines and solar cells. Skyllas-Kazacos’s invention, in short, could be the thing that fulfils the promise of renewable energy.
Skyllas-Kazacos chose vanadium, a soft, bright white and relatively abundant metal named for Vanadis, the Scandinavian goddess of beauty and youth. Vanadium has four oxidation states, known as V(+2), V(+3), V(+4), and V(+5); in each state the element carries a different amount of electric charge. Often oxidation states are hard to tell apart, but in this case nature was kind: V(+2) is purple, V(+3) green, V(+4) blue, and V(+5) yellow.
Simply having different oxidation states is not enough to make an element work for a liquid battery. The element has to be soluble, too. Skyllas-Kazacos started off with a highly soluble form, V(+4), then oxidized it up to produce a supersaturated solution of V(+5). From then on it became clear that the battery would actually work.
A traditional battery, such as the familiar AA dry cell, holds electrolytes in its own sealed container. But the vanadium battery is a flow system—that is, liquid electrolytes are pumped from external tanks into the stack, where the electricity-generating redox reaction takes place. Want to store more power? Use bigger tanks. The bigger the tanks, the more energy-rich electrolytes they can store.
The way to make renewables more reliable is to store the excess electricity generated during times of plenty (when there are high winds, for instance, or strong sun) and release it later to match the actual demand. Specifically, what is needed is a battery that can store enough energy to pull an entire power station through a rough patch, can be charged and discharged over and over, and can release large amounts of electricity at a moment’s notice. The VFB seems to have the edge in terms of scalability and economy.
Types of Storage Needed
Multiple energy storage market segments exist – load leveling, peak shaving, uninterruptable power supply for hospitals and nuclear reactors, remote/off-grid power systems, and more – each with its own set of requirements. The common requirements for mass energy storage batteries include: the ability to scale large enough to pull a given power supply through a rough patch, the ability to be charged and discharged repeatedly over a very long period, and the ability to release large amounts of electricity rapidly.
Unlike lithium-ion batteries, VFBs meet all these requirements. By combining VFBs with renewables such as wind and solar, the goal is to convert an intermittent energy supply into what the industry refers to as dispatchable electricity that can be regulated from moment to moment, allowing the grid to balance the amount of energy being put into the wires with the demand arising from consumers.
Energy Storage R&D
In mid-2010, the U.S. Department of Energy's Office of Electricity stated its goal of increasing energy storage capacity 10-fold to improve grid reliability and facilitate the adoption of such variable and renewable generation resources as wind and solar. In total, the government set aside $185 million to invest in deploying and demonstrating the effectiveness of utility-scale grid storage systems. Dwarfing that investment is the $600 billion in spending on energy storage solutions expected over the next decade, reaching $200+ billion in 2020 alone, according to a 2009 report by consultants Piper Jaffray.