IT’S LONG BEEN KNOWN that wind and solar energy have great potential for low-emissions electricity. But their variability and intermittency make them difficult to integrate into existing power systems. Currently, when the energy generated is not used immediately, it is discarded, or ‘spilled’ – leading to large losses because there is no adequate storage. Large-scale batteries, meeting the energy and power requirements of the grid – installed near the source of electricity generation or close to the end users – could help turn clean and abundant, yet intermittent, energy sources into reliable, steady forms of baseload power for cities and industry and avoid wastage.
Among storage technology innovations that are currently at small scale or in pilot plants, Equinox participants identified electrochemical batteries as a key technology. Electrochemical batteries can be sited anywhere, are modular and their rapid response times may be used concurrently with other advanced energy management applications. Their low environmental impact means they can be placed near residential areas. Within this group of innovations, participants judged ‘flow batteries’ as among the most advanced, with vanadium redox flow batteries showing particular promise.
Vanadium redox flow batteries are a type of rechargeable, large-scale battery that uses vanadium ions in different oxidation states to store chemical potential energy. Over the past 25 years, a design based on vanadium and using sulphuric acid electrolytes – developed at the University of New South Wales, in Sydney, by Maria Skyllas-Kazacos – has been under investigation with testing and evaluations at several institutions in Australia, Europe, Japan and North America.
Several features make the vanadium redox battery particularly exciting. It can offer almost unlimited capacity simply by using larger and larger storage tanks and be left completely discharged for long periods, with no ill effects. It can be recharged by simply replacing the electrolytes if no power source is available and, if the electrolytes are accidentally mixed, the battery suffers no permanent damage.
There are, however, barriers to full commercialisation. These specifically include: achieving a higher electric current density; increasing stack module sizes; and the development of inexpensive, chemically stable ion exchange membranes not subject to fouling by impurities in the electrolyte medium. The scale-up, capital and cycle-life costs and optimisation also need to be improved.
The pathway to implement this technology highlights the need to dramatically expand existing research and grid-scale battery demonstration projects already under way. The reliability and scope of renewable energy combined with storage should be a priority focus. Large-scale demonstration projects are needed to establish the economic viability of storage technologies, requiring partnerships between existing utilities and technology developers to help with commercialisation and wider implementation. Appropriate policy interventions are needed to encourage storage from renewable energy sources and discourage spillage.
This is part of a series on a blueprint to address the world’s looming energy crisis.