Author(s): Jesse Roman. Published on January 1, 2020.

Beyond EVs

Stranded energy is a concern across all energy storage technologies

STRANDED ENERGY AND problems like thermal runaway are not exclusive to batteries in electric vehicles (EVs). Both can occur in any battery, including stationary energy storage systems (ESS), which are being installed around the world in residential and office buildings, utility-owned industrial parks, and even private homes.

The devices are in demand because they can store energy created from renewable sources like wind and solar for use later. Battery energy storage is also becoming increasingly critical for utilities because stored energy reduces the need to build additional power plants to meet growing energy demands. The recently released NFPA 855, Standard for the Installation of Stationary Energy Storage Systems, includes detailed installation guidelines that take into account the needs of emergency agencies during incidents involving these systems.

The potential dangers posed by these large battery systems were revealed last April when firefighters were called to a utility-owned lithium-ion ESS in Surprise, Arizona, after heat and smoke were detected inside the battery. Out of caution, firefighters opted to monitor the situation for hours from outside of the battery container when, without warning, the battery exploded. Eight firefighters were injured, including four with severe burns and one with life-threatening injuries. The cause of the thermal runaway, and subsequent explosion, are still under investigation. In the last six months, NFPA instructors have traveled to Surprise, Phoenix, and 10 other locations across the country to lead training events intended to help responders understand how to handle ESS incidents effectively. NFPA also has online ESS training for first responders.

Although battery failures that lead to thermal runaway grab headlines, battery manufacturers and researchers are quick to point out that they are exceedingly rare. Reports have estimated the failure rate for lithium-ion batteries to be between 1 in 10 million on the high end, and 1 in 40 million on the low end, depending on the quality of the manufacturing. Bigger battery systems, however, like utility-owned energy storage systems in containerized units, may have 100,000 battery cells or more within the installation, making the failure rate per container much higher than it seems—as many as 1 in 100 containers on average could experience a failure in one of its battery cells.

As with EV, when ESS experience a fire or thermal runaway, response options are limited. Currently, there are no good ways for responders to determine how much energy remains in a damaged battery, and no effective means to drain energy from a battery to reduce the threat. In addition, the environmental impact of fighting fires in batteries is also not well understood. According to the Fire Protection Research Foundation, firefighters may need in excess of 3,000 gallons of water and more than an hour of constant spray to prevent the threat of reignition.

That creates concerns over the runoff created by these incidents, according to Cory Wilson, a chief at the Fremont (California) Fire Department. “Where does all that runoff water go? How bad is it for the environment? How do you collect that? Do you worry about collecting it?” Wilson said. “These are all issues that I think we're going to have to start working through as you see more and more of these vehicles on the road.” —J.R.