Explosion at APS energy storage unit injures firefighters, casts doubt on energy storage

Friday night, April 19, an explosion at a grid-scale energy storage unit near Phoenix injured four firefighters who were investigating a report of smoke rising from the facility. The APS McMicken Energy Storage facility is operated by Fluence, a company formed by Siemens after they bought out AES Corp, the original supplier of the battery system. This energy storage facility is serving the growing amount of solar energy resources being installed in that area of Phoenix.

Electric vehicle charging station guide

Grid-scale energy storage systems like this are the key to wide-scale adoption of wind or solar energy systems. Both those energy sources are super clean renewable energy, but because they’re intermittent energy storage systems are required to soak up energy for release to the grid later.

According to local news reports, eight firefighters from Peoria, AZ and Surprise, AZ, were called to the substation at 6 PM because of a passer-by report that smoke was coming from the site. The firefighters were evaluating the grid energy storage unit (2 megatWatt-hour battery pack) for hazardous chemical levels. They entered the facility, which is described as being the size of a mobile home, and an explosion occurred.

Four of the firefighters were sent to area hospitals, one in serious condition.

J1772 extension cords Tesla J1772 adapters Open the door to the Tesla Destination Charger network using these Tesla-J1772 adapters


The location is identified from this Arizona DOT tweet:

By coincidence the ESA Energy Storage Annual Conference had a scheduled tour of an identical nearby facility, APS’s Festival Ranch Battery Energy Storage System, on April 16. This was billed as a side event available for attendees, presumably so that APS could show off how advanced their electrical grid is?

The blurb described the Festival Ranch system as:

In February this year, APS announced one of the most ambitious storage initiatives in the country. By 2025, APS will add an estimated 850 megawatts of battery storage and at least 100 megawatts of new solar generation, for a total of 950 megawatts of new clean-energy technology. The Festival Ranch project features 2-megawatt (MW)/2 megawatt-hour (MWh) Advancion grid-scale batteries that support powering specific West Valley neighborhoods in the Phoenix suburbs.

The Festival Ranch project is part of a larger test array with McMicken, an identical array built about 12 miles due east of Festival Ranch. The projects were installed at different points on the feeders to see if location adds value to power quality and reliability for customers. The Festival Ranch battery is installed at mid-circuit, while the McMicken unit is contained at the head of the feeder in an existing substation.

The two systems were built during 2016 and became operational in 2017. In August 2017 a solar eclipse served as a test of the value of energy storage systems. Would the APS grid crash because it is so heavily dependent on solar energy that disappeared for the time of the eclipse? Nope. The energy storage systems kept the local grid humming.

That is the purpose of grid-scale energy storage systems. These are large battery packs that hold electricity, soaking up any excess electricity production from solar panels during the day, and releasing electricity when needed either to keep the lights on in the evening or to smooth out power fluctuations throughout the day. To implement 24×7 electricity off of a combination of solar and wind requires much more energy storage than pilot projects like this.

That’s the positive intended benefit of grid-scale energy storage systems. But having had a fire in one of these systems – will Regulators and other Powers-That-Be get spooked and slow down or stop deployment of these systems?

As said earlier, systems like this are critical to widespread adoption of solar energy systems.

Going by the news reports it seems APS is looking to implement distributed energy management system containing a mix of solar and energy storage resources. A subsidy program is in place for private rooftop solar systems:

Electric vehicle charging station guide

Participating customers are receiving $7,200 – $30 a month over the next 20 years – to install a collective 10 MW of photovoltaic rooftop solar panels so the company can study the use of smart inverters and energy storage. APS wants to learn how to improve reliability for customers in areas where a high penetration of solar has created instability in the system. The information APS is gaining from this study will help craft what the future of renewable energy integration looks like for utilities across the country.

But what happens if the Powers-That-Be are spooked because of a battery fire? Don’t laugh — this has happened before. I believe the story is told in the book Bottled Lightning that a very early lithium-based battery system was widely deployed as a battery backup system on AT&T telephone system wiring. Because the telephone system must have its own reliable power, it has battery systems to keep power running even if the grid goes down. This early lithium-based battery system was unfortunately unstable, and a bunch of the installed batteries blew up causing much damage.

Today’s battery systems are of course far more reliable. And as we’re taught to say about the Tesla electric car battery fires — there are far more gasoline car fires per year, on a per-capita basis, than electric car fires. But you have to wonder, why are the only electric cars catching fire made by Tesla? That’s a story for another day, though.

A couple years ago a hydrogen fuel-cell bus refueling system in Emeryville CA blew up with what sounded like a spectacular fire. While the Regulators in charge of Hydrogen Fuel Cell rollout were understandably alarmed, they studied the situation, the companies involved developed technological fixes, and the development of fuel cell buses is proceeding.

Maybe that’s what will happen for grid scale energy storage systems, investigation followed by a technical fix. But, a different local news report leads with the title “Solar storage facilities present unique hazard for firefighters“. A title like that seems geared to cast aspersions upon the value of grid scale energy storage. The article itself draws analogies from electric car battery fires, saying that Phoenix Fire Department personnel showed the ABC15 team video of an electric car battery “sparking and exploding” after a crash. The article went on to describe some of the alarmism, such as the risk of a battery fire reigniting itself after it appears to be “out”.

What I’m curious about it – the articles make it clear Fluence and/or APS has remote monitoring of the battery systems. Why did it take a passer-by to notice the smoke and report it to the fire department? W