Providing baseload power to the energy grid requires it be “dispatchable”, or available on demand, a significant advantage to fossil-fuel power sources. Smart grid development can help smooth out the expansion of renewable energy, but power storage is the means by which most experts see renewable energy expanding its role as a baseload power provider.
There are several ways to store power for later use during peak demand. Hydroelectric plants can draw on reservoirs to generate electricity, then pump some of the water back uphill during off-peaks times. Another method gaining some recognition is using compressed air for energy storage.
But of all the ways to store energy, batteries are still the most widely accepted. As Jim Kelly, senior vice president of transmission and distribution of Southern California Edison puts it, “For most of us right now, the real key to effective storage is batteries”.
There are several different battery technologies working their way through development and early commercialization, but one technology showing some real promise in stabilizing energy distribution in renewable systems is the Vanadium Redox Flow battery.
Vanadium – to a Goddess
The element Vanadium was discovered in the early 19th century and is named after Vanadis, in Norse mythology the goddess of youth, love, and beauty.
The element came to the attention of Australian researcher Maria Skyllas-Kazacos who, after a stint in the late 70’s researching battery technology at Bell Laboratories, began a project at the University at New South Wales investigating ways to store solar energy.
Skyllas-Kazacos built on the initial research done by NASA with flow batteries. Where NASA may have given up too easily, Skyllas-Kazacos pursued the idea, overcoming the main problem NASA encountered, concerning solubility and energy density of the element, by testing a highly soluble form of Vanadium as a liquid electrolyte.
Skyllas-Kazacos designed a flow battery using liquid electrolytes pumped from external tanks into a cell stack. Each contains a different ionic form of Vanadium stored in a mild solution of sulfuric acid acting as the electrolyte. Ions are exchanged during the charge/discharge cycle through a hydrogen-ion permeable polymer membrane creating an electro-motive force.
Well suited for the application
The VRB exhibits traits particularly well-suited for renewable energy storage and distribution. Among the principal advantages are:
- Efficiency and instantaneous power. Unlike other battery types, the VRB is very efficient and able to deliver large amounts of energy on a dime (more formally termed as a 1:1 charge/discharge window).
- They don’t “wear out”. Anyone who has owned a laptop for more than a couple of years knows that the battery will eventually stop holding a charge. A typical lithium-ion battery will only give a few hundred charge/discharge cycles. A VRB will cycle tens of thousands of times. With a minimum cycle life of 13,000 charges, the lifespan of a VRB is at least 35 years.
- VRB technology is highly scalable. Need more juice? Use bigger electrolyte tanks.
- No contamination with cross mixing of electrolytes.
- Very low self discharge. Once charged, the VRB stays fully charged.
- The VRB does not rely on toxic materials (like lead-acid or lithium) and has a relatively low environmental footprint.
Like any technology, the VRB has drawbacks, chief among them are price and size. VRB technology currently costs about $500 per kilowatt-hour. Large-scale VRB systems require installation in warehouse-sized structures.
The road to commercialization
Nonetheless, VRB continues to show promise commercially. The University at New South Wales patented the Skyllas-Kazacos design in 1986, and after a slow start the VRB began to gain momentum when Osaka-based Sumitomo Electric Industries licensed the technology in 1997. In 2000 Sumitomo began selling vanadium batteries, including a 1.5 megawatt device providing backup power to a liquid crystal display factory. The unit reportedly paid for itself within six months by enabling the production line to continue operation during blackouts. Fifteen other VRB systems have since been installed throughout Japan by Sumitomo.
Due to its scalability, the VRB is an ideal solution for remote, off-grid applications. VRB Power Systems of Richmond, Canada purchased the rights to the first-generation VRB technology and is a global distributor of the system, focusing on smaller remote installations as well as storage for renewable power, telecom installations, and load leveling/peak shaving applications.
With the rights of the first-generation VRB sold off, in 2005 Skyllas-Kazacos founded, along with her husband and two sons, V-Fuel to develop second-generation VRB technology. V-Fuel’s efforts aim at reducing costs and developing smaller application devices, like a current 5–kilowatt prototype about the size of a filing cabinet drawer. With the electrolyte tanks the unit can fit in a closet and make up part of a home-based solar power system. Skyllas-Kazacos believes the best is yet to come with the VRB, and the time is ripe for its full potential to come to the fore.
Maria’s pioneering work, and that of her colleagues at the University of New South Wales, may just make the Goddess Vanadis, along with her namesake element, the Goddess of Renewable Energy as well as of love and beauty.