For all their many virtues, wind and solar power have one major flaw: at some point, even in the windiest, sunniest parts of the planet, the wind stops blowing and the energy-giving rays of the sun disappear over the horizon. So as the world works to decarbonize its energy supply by reducing its reliance on coal, natural gas and petroleum and increasing its use of these variable renewable sources of electricity for the grid, one technology, in particular, is experiencing a renaissance: the stationary battery.
In a nutshell, stationary batteries are devices that use chemical interactions between materials to store electricity at a set location for later use. These batteries make it possible to store the electricity generated when sun and wind are at their peak so it can be made available to the grid when electricity demand is at its peak — such as when people get home from work and turn on their lights, air-conditioning or heating, television, and kitchen appliances.
The class of battery most modern electronics users and electric vehicle owners are familiar with is the lithium-ion, or Li-ion, battery. Li-ion batteries also predominate in the stationary battery market, mainly because they’ve been around longer and have had more time to mature as a technology, according to Jessica Trancik, associate professor of energy studies at the Massachusetts Institute of Technology (MIT) and the Institute for Data, Systems, and Society
But just because Li-ion batteries are commonly used in consumer electronics and EVs, that doesn’t necessarily mean they’re the best option for storing electricity in a renewable energy-dependent grid. Today’s lithium-ion batteries have their risks, costs, and limitations. And while they might be first out of the blocks on the battery market, they will soon face stiff competition from a variety of alternatives and amendments that aim to match or beat their efficiency, with greater safety and sustainability. As the incentives increase for the development of more large-scale electricity storage and the business case for better battery storage technology becomes evident, there’s plenty of innovation happening.
Flow Batteries
Among the frontrunners for large-scale stationary storage of wind and solar power are flow batteries, which consist of two tanks of liquids that feed into electrochemical cells. The main difference between flow and conventional batteries is that flow batteries store the electricity in the liquid rather than in the electrodes. They’re far more stable than Li-ion, they have longer lifespans, and the liquids are less flammable. Not only that, but a flow battery can be scaled up by simply building bigger tanks for the liquids.
One type of flow battery, known as the vanadium flow battery, is already available commercially. A grid-scale 50-megawatt vanadium flow battery is planned for energy storage in the South Australian town of Port Augusta, and China is building the world’s largest vanadium flow battery, expected to come online in 2020. There are two main downsides: the liquids can be costly, so there’s a greater up-front cost for the batteries, and flow batteries aren’t quite as efficient as Li-ion batteries.
Plenty of Innovation
There are plenty of other developments happening in this space, making it an exciting time for battery research and development, Trancik says.
For example, researchers at RMIT University in Melbourne are developing a proton battery that works by turning water into oxygen and hydrogen, then using the hydrogen to power a fuel cell. Several other research teams around the world are exploring completely lithium-free ion batteries using materials such as graphite and potassium for the electrodes and aluminum salt liquids to carry the charged ions. Researchers in China are looking at improving the existing technology of nickel-zinc batteries, which are cost-effective, safe, non-toxic and environment-friendly but don’t last as long as Li-ion. There is even work going on related to saltwater-based batteries, with one design already being used for residential solar storage.
“Now we see a lot more incentive, we see falling costs for lithium-ion batteries, we see the stationary energy storage market benefiting from the growth of electric vehicles,” Trancik says. “It’s definitely still early days, particularly for stationary energy storage, but it’s a really important area and I think people are starting to realize that.”