Tesla Megapack Catches Fire: Should Lithium-ion be Avoided for Grid Energy?

After a year of being installed, a Tesla Megapack caught fire in California, which firefighters were able to contain but not put out. What challenges does lithium-ion present, what happened at the Megapack site, and does this indicate that lithium-ion is unsuitable for grid storage?

Another Tesla Megapack is up in flames!

A Tesla Megapack responsible for stabilising grid energy recently caught fire in California during the early hours of 20th September. The site, owned by PG&E, stated that the damage by the fire was contained and that customers experienced no power outages thanks to the ability for the system to be disconnected. The company also reported no injuries to any on-site personnel but warned local residents to keep away from the site due to the risk of environmental contamination.

Firefighters, who responded to the fire at 1:30 AM, stated that due to the nature of lithium-ion batteries, the Tesla battery fire was contained instead of being extinguished, and a number of firefighters waited overnight to ensure that the battery system didn’t reignite. The facility was constructed last year in April and has a total capacity of 182.5MWh which is enough to provide power to 10,000 homes for one hour (assuming each house uses 20kWh power continuously). Assuming that homes typically use around 20% of their maximum power input at any one time, such a battery system can provide constant power for 50,000 homes for an hour. 

The site is also home to a second energy storage solution provided by Vistra, which was said to be unaffected by the incident. However, it has reported numerous overheating incidents in the past, raising concerns about whether lithium-ion battery storage solutions are viable for grid energy.

What challenges does lithium-ion present?

Despite attempts by engineers to integrate lithium-ion energy sources into energy grids, numerous challenges are faced that raise questions about the efficacy of their use. 

By far, the biggest challenge faced with lithium-ion integration is the susceptibility to damage and the catastrophic response to a failure. If a lithium-ion battery is charged too quickly, small crystals can grow between the electrodes that, if shorted, can see massive currents. These currents quickly overheat the battery and cause a chemical breakdown of the internal components, including the electrodes and electrolytes. Unfortunately for lithium-ion batteries, this degradation almost always produces massive amounts of hydrogen and more heat, creating a major fire risk.

This brings us to the second challenge; the inability to extinguish lithium fires. Should a lithium-ion battery catch fire, very little can be done to stop it. As firefighters have discovered with EVs, the amount of water needed to put out such a fire is significantly higher compared to traditional contestable materials (approximately 2600 gallons or a swimming pool’s worth of water was needed in one test fire). Worse, a fire that is extinguished can reignite itself again, causing further fires. Firefighters often let lithium fires burn themselves out while simultaneously preventing its spread. 

Finally, lithium-ion suffers from a limited number of charge/discharge cycles (typically 2000). Despite this figure being similar to that of lead-acid batteries, their significantly greater cost can make such battery installations very expensive to install and operate. Furthermore, recycling lithium batteries is an extremely difficult process and, often, not economical.

Does this fire indicate that lithium-ion should be avoided for grid energy?

While lithium-ion may be practical for passenger cars and mobile devices, the recent fire at the California site further provides evidence against lithium-ion use in grid energy storage. In fact, this is not the first time a Tesla Megapack caught fire; last year saw an Australian site also catch fire which presented numerous challenges for putting it out. 

While there have only been two fires at such sites, there are not that many Tesla Megapack sites around the world (this figure is hard to determine, but their site seems to suggest that three such large-scale sites currently exist, while numerous smaller units may also exist). As such, the failure rate for these sites would be significantly higher compared to other storage mediums (such as molten salt or pumped hydro). Despite their site suggesting that the Megapack facilities are safe by design (with emphasis on battery energy storage fire safety), the fact that two of these sites have managed to catch fire puts this claim into serious doubt. 

Instead of trying to construct large centralised facilities, it makes more sense for grid operators to take advantage of EV owners and utilise parked EVs as energy storage devices. EV owners could be given energy credits for contributing to grid stability, and intelligent charging systems could identify the cheapest times to charge vehicles. During peak demand, EVs could dump power into the grid, which helps to plug the energy gap when renewables cannot meet demand. Furthermore, a decentralised storage system uses batteries in vehicles that are already doing nothing when parked, and the decentralised storage solution is virtually immune to fires as a single EV failing doesn’t damage other connected batteries.

Overall, the idea of large energy storage solutions using lithium-ion appears to be more of a gimmick as opposed to a serious solution. Having a large amount of combustible materials stored in a confined space seems to be the equivalent of ammunition dumps and would even be a tempting target by terrorists and rouge nations looking to do serious harm.