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9 August 2019

APS in hot water in Arizona as Fluence battery goes up in flames

Arizona’s state utility APS has been reprimanded by Democratic Commissioner Sandra Kennedy, who said that a fire in a battery storage installation run by Fluence, the AES-Siemens joint venture, highlights the “unacceptable risks” posed by lithium-ion batteries. This might just be bad PR, but if the complaint lights another fire under politicians, battery storage could take a real hammering in the US.

Kennedy is not following the usual channels, publishing her comments in a letter independently of the other four members of the Arizona Corporation Commission (ACC) that has oversight here. Her letter is part of the ACC’s investigation into the fire at APS’ McMicken substation, which housed a 2 MW (2 MWh) battery provided by Fluence.

The fire, which broke out on April 19th, injured four emergency workers who were sent to get it under control. In the latest update from APS, the utility says that it is still not known how the reports of smoke led to the catastrophic failure after the site door was opened around three hours after the alarm was raised.

The firefighters were examining the batteries when an explosion occurred, and were treated for chemical burns and chemical inhalation damage. Batteries tend to burn fiercely rather than explode, and so there has been confusion over the cause of the blast. It could have been due to gas that leaked from the battery, but there are other factors that could be the cause, rather than the batteries themselves.

However, as these batteries burn in a very different fashion than most materials that firefighters typically encounter, they are not (collectively) not yet well equipped to fight them. You may recall problems with firefighters trying to put out burning Tesla vehicles at the scenes of automotive crashes, and struggling without the correct compounds to extinguish these lithium fires. This is one of the drivers behind Kennedy’s complaint.

Forensic analysis is underway, after the 378 battery modules were removed. All but one were discharged at site, with one due to be discharged elsewhere next week. APS hasn’t said why this is the case, but it seems reasonable to conclude that this one module could be the culprit. Components from one of the racks in the facility have been sent off for examination, and will be x-rayed and carefully separated to discern what happened. APS says that these results should be available in September.

This isn’t APS’ first battery fire. An incident in 2012 at its Eldon substation prompted concerns, and now Kennedy is using the second incident to argue that utilities should be looking for alternatives to lithium-ion – which is problematic, as it is the affordability of lithium-ion that is driving the adoption of batteries in these energy storage applications. APS has committed to deploying 850 MW of energy storage and 100 MW of solar by 2025, but if it is forced to looked for alternative to lithium-ion in the wake of this fire, it is going to run into problems.

A ban or restriction on new installations would be extremely detrimental to the industry, as it would hamper efforts to adopt more renewable sources of energy – both centralized grid-scale projects, as well as DERs like rooftop solar. The batteries are key to accommodating the variable outputs from these renewables, which when paired with a battery, can be treated as fairly conventional generation assets – but ones that are often (and soon completely) cheaper than fossil fuels, with far less of a carbon footprint.

“As large-scale investments are made, it would be prudent and advisable to invest in utility scale energy storage systems that are sustainable, less risky, and do not utilize chemistries that have a potential to release hydrogen fluoride in the event of a fire or explosion,” Kennedy wrote in her letter.

She posits liquid metal chemistries as alternatives, including zinc air, magnesium, and nickel-iron, which she argues use “cheap, abundant raw materials, very safe operational characteristics and an ability to go through many charge-discharge cycles without degradation.”

Kennedy rounds out her complaint by saying that “there are other utility scale battery technologies that are available that are far more sustainable and do not have these risks. There are also other lithium ion batteries that utilize chemistries that do not carry the same risks as those involved in the Eldon Substation and McMicken incidents.”

In response, COO of Fluence, John Zahurancik, told Utility Dive that “There are 9,000 MW of energy storage in operation around the world, using these lithium-ion cells in safe, controlled, pre-engineered environments. All electricity generation, distribution, and transmission technologies bring a measure of risk that requires careful operation and appropriate layers of safety. Lithium-ion based energy storage has been proven safe through years of operation, and utilities around the world have made it a critical part our energy mix.”