Last Friday, a Megapack at the world’s biggest energy storage construction site caught fire. It took firefighters three days to put the fire out. In a way, however, the incident, which took place in Australia, ignited another fire: a debate about the safety of lithium-ion batteries. Media coverage of energy storage rarely mentions any risks. The focus is invariably on bigger and better storage in anticipation of the future low-carbon energy systems that we are now trying to build. New technologies—including alternatives to lithium-ion batteries—are a frequent topic, and stats and forecasts about storage capacity are also a favorite.
Combustion risks, not so much.
Yet, like EV batteries, energy storage batteries like the Tesla Megapacks at the Victoria, Australia, site are prone to combustion under the right circumstances—because of the things they are made of.
An article in the Australian website EcoGeneration lists some of the flammable elements of a lithium-ion battery: the liquid electrolyte through which those famed lithium ions travel is flammable, for example. So is the graphite in the anode and the plastic in the insulation of the battery.
But how do fires start in batteries? In short, they start when optimum operating conditions are compromised, according to an associate professor from the Australian National University and Research Lead in Battery Materials in ANU’s Battery Storage and Grid Integration Program, who spoke to EcoGeneration.
Batteries are sensitive to overheating and overcharging, Alexey Glushenkov explained to EcoGeneration. Overheating initially happens in a single battery cell but can quickly spread to all the other cells in a battery pack. Battery manufacturers seek to minimize the chance of that happening. Unfortunately, recent battery incidents have proven that it is not always possible to completely eliminate the danger.
When a battery cell overheats, gases begin to build up inside it, swelling it and eventually opening it, allowing oxygen to come in and spark a fire.
But how does overheating happen? By overcharging, which can also cause unwanted chemical reactions in the battery cells—again threatening fire.
The most common cause for all of this is a short circuit. According to Glushenkov, it could be the result of a bad battery design or a manufacturing defect. Short circuits can also start at a molecular level when overcharging the battery cell results in the buildup of metallic lithium in the anode. These buildups grow into what are commonly known as dendrites.
“As the process happens again and again those structures, called dendrites, can penetrate the separator [between the two electrodes],” he says. “A short circuit will result and the battery discharges instantaneously, causing a lot of heat to be generated.”
The risk of a fire is certainly a problem, but perhaps a bigger one is that extinguishing that fire is not as easy as putting out a “normal” fire. This is because of all the chemicals that go into making a battery cell. Those chemicals create the gases that build up in batteries right before they explode.
“We don’t have a definitive answer of what is the best way to deal with an EV [electric vehicle] fire or energy storage fire,” Newcastle University professor Paul Christensen told the Financial Times, commenting on the Victorian Big Battery incident.
“They [lithium-ion batteries] are essential to the decarbonisation of this planet but their penetration into society has far outstripped our actual knowledge of the risks and hazards associated with them,” he added.
One might suggest that the risk is minimal; otherwise, we would be hearing about battery storage fires every day. But, in fact, there have been quite a few battery storage fires recently, according to Christensen: a total of 38, in fact, since 2018, including one at an Orsted battery storage site in the UK, and one in Arizona, at a battery storage facility operated by Arizona Public Services.
There are “many similar battery enclosures operating today that could experience the exact same kind of failure,” warned Matthew Paiss, a technical advisor on battery materials and systems at the pacific Northwestern National Laboratory, at the Energy Storage Summit USA earlier this year.
The way to reduce the risk is to ensure the rapid release of gasses built up in a battery cell, according to experts. Yet achieving this rapid release may be easier said than done. In the meantime, the risk will only grow, as the FT notes, because of the wider adoption of lithium-ion batteries, including in households.
“2020 was a record year for global energy storage,” said Wood Mackenzie’s head of energy storage, Dan Finn-Foley, earlier this year. “The market exceeded 15 GW/27 GWh in 2020, increasing 51% in GWh terms, and is expected to grow 27 times by 2030 by adding 70 GWh of storage capacity a year to surpass 729 GWh in 2030.”
This rate of growth will likely make the need to reduce the risk of fires more urgent. Whether it will be addressed with an appropriate urgency remains to be seen.
By Irina Slav for Oilprice.com
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