Energy Storage Systems: A State of the Union

By Jocelyn Sarrantonio, PE | Technical Director, MeyerFire
 
Think State of the Union, but today I’m going to talk about the State of ESS in Fire Protection. So without further ado, members of the community, today I have the privilege and honor of discussing battery energy storage systems. Please clap. [Applause Please]

Just kidding, but today I wanted to talk about where we are as a fire protection community with regards to the response to the widescale adoption of battery energy storage systems (BESS) practically everywhere.
 
THERMAL RUNAWAY
If you didn’t take my Introduction to ESS course (shameless plug for our recent course, Introduction to Energy Storage Systems), the primary risk that comes with BESS, particularly lithium-ion batteries, is their susceptibility to thermal runaway.

Thermal runaway is a process resulting from a battery failure, where cells inside a battery undergo a rapid temperature increase and vent flammable gases, creating an explosion risk.
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The risk is proportional to the quantity of batteries in an installation, so you can imagine if we’re not even allowed to have lithium-ion batteries in our checked bags on airplanes, then enormous utility installations pose a substantially higher risk. 

Thermal Runaway in Battery Cells
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The risk has been a part of our lives for years, so what are we learning about ESS?
 
#1 THE FIRE RISK CAN BE LONG-LASTING.
It can take large volumes of water to sufficiently extinguish and cool fires involving ESS, and due to the stranded energy in battery cells, re-ignition is a risk.

Even battery cells that are not plugged into anything can still undergo thermal runaway, if they are abused.

Emergency responders typically use thermal detectors to find any hot spots after a fire is extinguished, but it is critical to continue monitoring for longer than you’d think after a battery fire. Re-ignition can happen months after the fire! That’s long after the emergency responders have left, so there's a need to develop a protocol to monitor and prevent re-ignition.
 
#2 REGULATION OF E-SCOOTERS, E-BIKES & OTHER MICROMOBILITY DEVICES
In large cities where space is hard to come by and small lithium-ion batteries are everywhere, tighter regulation of micromobility devices is coming.

In New York City, for example, the market has been flooded with low-cost and unsafe products, partially due to the rise of food delivery apps.

The delivery workforce generally earns low wages, and there is no accountability from the app companies on the micromobility devices used. So the workforce is not motivated to purchase quality products, and the result is low-quality batteries being charged inside densely populated buildings.  
 
#3 SHIFTING PUBLIC PERCEPTION
Public perception may start to shift.

We’ve seen the videos of battery fires that include large plumes of smoke, and it’s hard not to imagine how local residents are faring.

Public pushback about BESS projects has increased following recent fire incidents, and the path forward likely includes educating the public to ease their concerns.

Even though the public directly benefits from lower electricity costs or stability of the utility grid, people are not willing to sacrifice safety and negatively impact their community. I’m not sure what that looks like, but it does seem like with any large project, developers have a responsibility to educate the people who are negatively impacted when there is an emergency situation.

If you want to build in someone’s backyard, you’ve got to convince them that what you’re doing is safe, and is a benefit to them.

Maybe that means highlighting training of your staff, the safety of the equipment you’re buying, or investing in local emergency responder equipment.

CONSUMER SAFETY
On the face of it, BESS safety is not just an area of concern for us as fire protection engineers, but as consumers as well.

Lithium-ion batteries are in our cellphones, laptops, electric vehicles, solar panels, and e-bikes. It’s important to note that when we talk about energy storage systems, the IFC and NFPA 855 have a threshold of 20 kWh where these requirements kick in.

For reference and speaking in rough orders of magnitude, a laptop battery might be 0.1 kWh, a phone might be 0.015 kWh, an electric scooter may be 1.5 kWh, EV’s may be up to 100 kWh, but a large Tesla Megapack that would be used in a utility grid installation is up to 4000 kWh, or 4 MWh. 

A relative comparison of different energy storage capacities.
​Important to note the logarithmic scale used for storage capacity (vertical axis)
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The risk of thermal runaway exists in all of these products, but the impact is greater as the capacities increase. 

As a consumer, if it is an option you should always buy products that have a mark from a nationally recognized testing laboratory (NRTL). What does that mean? Without getting too far into the weeds, there are several organizations, the most prominent one being UL, that test consumer electronics including TV’s, computers, and even Christmas tree lights.

When a product “bears the UL mark” it means it went through rigorous testing and complies with UL’s safety standards.

​That’s not saying there is no risk, but when we’re talking about a product which carries some inherent risk already, having a genuine product that complies with some standard of safety is even more important. 

The UL mark. Look for this on your electronics!
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It may be tempting to buy the cheapest version of a product, but using non-certified products, or even worse, fake products, can increase the potential risk for fire. This is because those products haven’t been tested to safety standards and they do not necessarily meet those higher quality and safety thresholds. 

You should also follow all manufacturers’ guidance when it comes to temperature control, clearances, ventilation, and where and how to charge devices.

We never want to charge these devices where they will block access to an exit.

Thinking about where people who drive e-scooters might live, it’s probably in a densely occupied apartment structure, and where they may charge their scooter, it’s probably by a door. Many apartments and condos only have one common path of travel, so if there’s a problem it may block the only exit and now a bad situation is worse. 

TRENDS IN INDUSTRY RESPONSE
Some of the trends the industry is seeing come in the form of alternate electrolyte recipes, methods of early detection, and more large-scale fire testing for extinguishing agents. 

First, if lithium-ion batteries are the problem, why don’t we just use different batteries? 

The reason this is even a challenge is that the industry quickly adopted lithium-ion batteries because they are lighter than their historical predecessor, lead-acid batteries. They also have a higher power density, so they can either take up a smaller footprint for the same capacity or get a higher capacity with the same footprint. 

It’s not a perfect analogy, but I think this is akin to the fire protection industry’s history halon as a fire extinguishing agent. 

Halon is a gaseous fire suppression agent that is quite effective, but then we learned how bad it was for the environment, so the industry shifted to other solutions. These other solutions may not be as effective as halon, but they sure outweigh halon’s major disadvantage. 

Similarly, the strategy here is to find other battery chemistries that may not be as inexpensive or energy-dense as lithium-ion, but that outweigh lithium-ion’s major disadvantage. 

Another strategy for the industry is smarter products, which can detect thermal runaway earlier, leaving more time for response. 

I’m keeping a discerning eye out for new products that include more sensitive gas detection, thermal imaging, or other sensors that will help us design more robust systems that mitigate explosion risk. 

Lastly is more large-scale fire test data for extinguishing agents. The code opens the door for alternative extinguishing agents, but I have yet to see good large-scale fire test data for these non-water based agents. There may be a reason for that, if they are ineffective, but so much of our design criteria is based on testing, so I’m looking forward to more data to help us validate design criteria. 

CODE DEVELOPMENT
As you probably are aware, the codes are doing their best to keep pace with the risks, in a reasonable timeline. 
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The IFC has been revised extensively since 2018 to integrate ESS requirements, and the latest 2024 Edition brings it largely in agreement with the 2023 version of NFPA 855. That standard is currently undergoing its normal revision cycle, with a new edition set to be published in 2026.

NFPA 855's next revision is expected in 2026.

It is expected that the 2026 Edition will include additional large-scale fire testing requirements beyond the current UL9540A testing and further development of the Hazard Mitigation Analysis (HMA) procedures.  

With each jurisdiction’s unique adoption of its building and fire codes, there is an opportunity for further amendment of these standards.

It is critical to verify if a jurisdiction has any amendments to the generic code language for ESS and to verify if there are any special permitting procedures for ESS. My next course, coming this quarter, will be a review of the major code requirements for ESS.
 
PROBLEMS THAT REMAIN
It seems that the world is not going to soon give up on the use of lithium-ion batteries in BESS installations, so the toughest challenge that remains is how to deal with the explosion risk.

The tools we have at our disposal, NFPA 68 & 69, were not developed with BESS in mind, but can be part of a layered approach to addressing the explosion risk.

Since we are a prescriptive code-driven industry (in North America at least), we look for guidance on how to design these systems or how to perform these evaluations from the codes & standards themselves. I’m really looking forward to any new guidance in these documents to help give us consensus on how to approach the risk.
 
BEST PRACTICES: SO WHAT DO I DO?
If you are a fire protection engineer (or anyone) involved in an ESS installation, the basic process is as follows:

• EDUCATE: Educate yourself on how you may see ESS in your work.
  
  
• PRODUCT DATA: Gather the data. You will need product data for the ESS and the associated UL9540A test report.
  
  This is the fundamental information you will need to design the system spacing, ventilation, and associated fire protection systems.
  
  
• DEFLAGRATION OR EXPLOSION CONTROL: Evaluate the need for deflagration or explosion control. 
  
  This can have major impact on a design, depending on where the ESS is intended to be installed. Identifying where pressure-relief vents or exhaust ductwork can be routed is key.
  
  
• ENGINEERED SYSTEM INTERFACES: What systems are available that can interface with the BESS?
  
  Understanding the battery monitoring system to determine if information can be used for emergency control functions.
  
  
• COUNSEL OWNERS ON THEIR RESPONSIBILITIES: Many jurisdictions are focusing on the commissioning plans, yes, but also decommissioning plans.
  
  What is the life cycle of these batteries, and how will they be disposed of safely once they have reached their useful life?
  
  Because of the unique hazard BESS can have with stranded energy, you can’t just stack old equipment in a storage room and deal with it later. IFC 2024 also has a new requirement for a fire safety and evacuation plan to be included with the BESS construction documents.
  
  As fire protection engineers, we need to do our best to make owners aware of their increased responsibilities.
  
  

WHAT’S NEXT?
There’s quite a bit to keep up with. Many of us in this space are watching the development unfold. Deployments will only increase as utility grids move toward lower reliance on fossil fuels. Monitoring changes in codes, battery chemistries, and expectations of the public, owners, and AHJs will be needed to build trust and achieve reasonably safe outcomes.  Staying current and educated is our challenge today. Rigorous testing and proactive stakeholder engagement will be important as we all move forward to safer energy storage systems.

So in conclusion, the State of our Union is strong!

​Thanks for reading, until next time, stay safe, and always check your local jurisdiction’s amendments!