20-08-2021 | | By Robin Mitchell
Recently, a Tesla Megapack station that stores energy for renewable systems recently caught fire that was impossible to put out. What energy storage methods are being explored, what happened at the battery site, and why is this evidence of the unsuitability of lithium-ion energy storage?
The ongoing climate situation is seeing governments around the world turn towards renewable sources of energy. While solar, wind, and tidal can all produce vast quantities of power, they can only do so when those energy sources are around. For example, the sun doesn’t always shine, the wind isn’t always there, and tides come and go.
During peak energy availability, renewable energy sources can find themselves producing more power than what is needed. When renewable energy production is at its lowest, energy demands are often at their highest. Thus, energy generated during peak times needs to be stored to help meet energy demands during peak usage.
One technology explored technology is lithium-ion batteries due to their high energy density and ability to quickly deliver enormous amounts of power. Another energy technology explored is stored hydrogen; water can be electrolysed to produce oxygen, and hydrogen is kept separately. When these are recombined in a fuel cell, the resulting electricity can provide power to the grid.
More unusual forms of energy storage include stacking heavy concrete blocks; lifting blocks requires energy during peak production, and lowering the blocks produces power that feeds the electrical grid during peak demand.
Recently, a Tesla Megapack in Victoria, Australia, caught fire, disabling one of the world’s largest grid storage systems. The site is rated for 450MWh, which can power approximately 150,00 homes for one hour. While no one was injured due to the fire, investigations are still underway to determine the cause and nature of the fire itself. What is known is that the fire started during a test cycle of the facility, which could suggest that the fire was a result of new hardware or software being trialled. While the fire itself did not cause injury, a cloud of toxic smoke was produced, whose effects on local residents is unclear at this time.
Fire crews could not put out the fire and instead had to rely on containing the fire until it burned itself out. This was done by ensuring that neighbouring battery containers were kept cool with water and carefully monitoring the fire. Furthermore, the emergency crew expressed their concern with the facility’s design as battery units were placed very close to each other and accessibility to the fire was challenging.
Lithium-ion batteries are excellent for mobile devices as their high-energy density allows them to be made small. Furthermore, lithium-ion batteries can also discharge large amounts of current very quickly, meaning that they are good at providing large instantaneous amounts of power.
However, their ability to deliver high current, store large amounts of energy and the materials they are constructed from also presents a significant challenge; they are volatile. A shorted lithium-ion battery results in a substantial current flow. The high energy density of such batteries ensures that this current flow can be sustained for a long time.
The high current results in the battery and external circuit during a short circuit, causing the short circuit to heat up dramatically. The internal heating of the battery combined with the rapid discharge causes hydrogen to be produced. From there, either the battery swells and increases in pressure or the hydrogen gas escapes. Due to the high temperature of the battery and/or circuit, this hydrogen can be ignited, creating a stream of flaming hydrogen that can cause further fires.
Thus, the most significant danger of a lithium-ion battery is that they are almost impossible to put out once they are ignited. In the Tesla Megapack fire, firefighters had to leave the fire to burn as their efforts could not stop the fire. This example of a battery fire may be the critical evidence to show how battery technologies are not suitable for energy storage.
Batteries are great for providing instantaneous power when needed, but the use of lithium-ion presents significant risks that need to be solved. No matter how many safety systems are put in place, a fire started by a lithium-ion battery is far too challenging to manage. Such technology may only be suitable for small scale systems such as smartphones and EVs.