Flow batteries offer significant advantages over lithium-ion batteries. They have a much longer lifespan, can be fully discharged and recharged many thousand of times without damage, and have no danger of explosion or fire due to overheating. They also tend to be heavy and bulky, which makes them unsuitable for use in automotive applications.
Known to the scientific community as redox (reduction oxidation) batteries, they involve two tanks of liquid — one positively charged and one negatively charged — separated by a membrane which allows electrons to pass between the two tanks but not molecules. In the right setting, they can store prodigious amounts of electricity safely and inexpensively.
German utility company EWE says it is planning to build the world’s largest battery based on flow technology in a pair of salt caves currently used to store natural gas. Taken together, the caves have a volume of 3.5 million cubic feet — enough to store up to 700 megawatt-hours of electricity with an output capacity of 12o megawatts, according to Digital Trends.
To put that into perspective, a battery with that much capacity could meet the electrical energy needs of the city of Berlin for an hour or 75,000 homes for a day. “We need to carry out some more tests and clarify several issues before we can use the storage principle indicated by the University of Jena in underground caverns. However, I expect that we will have an operating cavern battery by about the end of 2023,” says Ralf Riekenberg, head of the project, which has been named brine4power.
Grid-scale battery storage is less about operating homes or cities for hours or days and more about balancing out the flow of renewable energy during the course of a typical day. Sometimes the sun shines; sometimes it doesn’t. Sometimes the wind blows; sometimes it doesn’t. Grid storage makes it possible for utilities to better plan for the needs of their customers at all times.
Traditionally, there is baseload power — often from coal or nuclear facilities. Baseload power doesn’t vary much during a typical day. But there are times when more power is needed. That’s when so-called peaker plants — typically powered by natural gas — get switched on.
Firing up a peaker plant costs money and they do not come online instantaneously. A battery, on the other hand, can react in seconds and costs nothing to activate. Once built, it also has no ongoing fuel costs. That makes battery storage attractive to utilities that are focused on maximizing net revenues.
Grid storage also protects against blackouts when some of those “baseload” power plants mentioned above unexpectedly goes down.
When the new brine4power venture is completed in 2023, it is not guaranteed to be a commercial success, of course. Earlier this year, Aquion Power, which specialized in flow battery technology and was supported financially by Bill Gates, filed for bankruptcy. NanoFlowcell is an electric car car startup that touts flow battery technology but it has yet to begin selling cars, despite some very appealing concept designs.
Energy storage is a hot topic around the world. Elon Musk has just inked a deal to install the world’s largest lithium-ion battery storage facility in South Australia. Pumped hydro storage is still a popular choice in areas where the terrain makes it feasible. There is even a plan to build a train that carries freight cars filled with concrete blocks up a mountain in Nevada during the day and generates electricity as it slides back down the mountain at night.
Will the EWE plan be commercially viable? “We’ll see,” said the Zen master.
Image by Colintheone