The Obstacle Course on the Path to Repurposing Used Electric Vehicle Batteries (EVB). Part VII: Fire Safety for a Second Life BESS in LA County
This is the seventh blog post of our series where we discuss how to design for fire safety in an energy storage system. In this blog, we’ll cover
How to follow complex fire code for a novel technology
ReJoule’s approach
Presenting to the Authority Having Jurisdiction (AHJs)
Introduction
Two hundred and twenty four modules, or more than 9,000 lbs of electric vehicle batteries are scheduled to enter their second life at the American Museum of Ceramic Arts (AMOCA) in Pomona, California. Thanks to this California Energy Commission grant funded project, we are able to turn potential hazardous waste into energy storage for communities that need it most. The 275 kWh system will provide 24 hours of reserve power for AMOCA that will serve as a community disaster relief and cooling center in case of emergency.
Figure 1. AMOCA’s 2LB BESS
How do you follow complex fire code on something novel?
In order to build a structure in the public sphere it must be code compliant. Entities such as Underwriters Listed (UL), California Fire and Building Code (CFC & CBC), as well as the National Fire Protection Agency (NFPA) all have standards and regulations, from devices to entire structures, that keep the public safe. All of these codes are taken into consideration by the Authority Having Jurisdiction (AHJ) who dictates what is allowed to be built within its jurisdiction. This role is usually assumed by the local building and fire department.
In our case, a second life battery system had never been proposed to the Los Angeles AHJ, nor did existing code have specific guidelines on second life battery systems. ReJoule sought help from Matt Paiss, a Technical Advisor of battery materials and systems from the Pacific Northwest National Laboratory (PNNL) and a prior Fire Captain with 28 years of experience in emergency response. With Matt’s help, our team proactively addressed the potential dangers of a BESS within our design.
Current battery energy storage systems (BESS) use fire suppression methods such as overhead sprinklers and various chemicals in the form of foam, gasses, liquids, and powders. Due to the nature of a battery fire, these suppression methods are typically ineffective at preventing or stopping a thermal runaway event once it has initiated; in some sense a battery fire must burn itself out. This is why we decided to take a different approach.
ReJoule’s approach: addressing the lower flammability limit
Less commonly known dangers of a lithium ion battery are the flammable gasses it produces under thermal runaway and their potential for a deflagration event. The potential explosion caused by these gasses can easily blow the doors off a shipping container and is an extreme risk, even to firefighters trained in explosion control.
An example from the UL Firefighters Safety Research Institute report: “Four Firefighters Injured In Lithium-Ion Battery Energy Storage System Explosion - Arizona” shows the importance of deflagration prevention within BESS design.
In order to mitigate the deflagration risk our engineers chose to use PNNL’s IntelliVent™ methodology of early detection and keeping flammable gas concentrations below the lower flammability limit (LFL). The LFL is the lower end of a concentration range where a flammable mixture can be ignited at a certain temperature and pressure.
Every gas that is emitted during a thermal runaway has its own corresponding flammability limit and in AMOCA’s case, hydrogen gas was of main concern. LFL values thus became a crucial design constraint which were evaluated through a computational fluid dynamic (CFD) analysis.
How does deflagration prevention in a BESS work?
AMOCA’s BESS utilizes hydrogen, heat and smoke detectors placed throughout the system in order to detect a thermal runaway event as soon as possible. When these sensors are triggered, four doors along the short side of the system are immediately opened along with visual and auditory alarms along with sending a notification to the local Pomona fire station.
Figure 2. BESS Internal Layout
This system allows for smoke and flammable hydrogen gas to escape the container and maintain gaseous concentrations below the lower flammability limit. Additionally, with the doors of the system open, firefighters are able to evaluate potential hazards from a safe distance and use additional fire containment methods as needed.
Figure 3. Thermal Runaway Simulation
(left) IntelliVent™ system doors are open with gasses leaving the BESS. (right) IntelliVent™ doors remain closed and gasses exceed the LFL.
Let’s compare what would happen if thermal runaway occurs and the container's doors do not open. In Figure 3, the left image shows what happens when container doors open and the right image when doors remain closed. On the right side of Figure 3 we can see an enclosure environment saturated at 0.16 mol/mol which is well over the LFL and presents a high risk of explosion. This is also visualized by the dotted matrix that turns black when over the LFL(Magenta Arrows) and is red when under the LFL(Green Arrows). In order to reduce the volumes of gas exceeding the LFL we must open the doors of the system. On the left side of Figure 3 we can see doors are open and the container environment is primarily red, under the LFL, with a black volume venting from the top of the container doors.
When the doors of the container are opened upon gas detection, hydrogen gas concentration remains 4 times lower and reaches a steady state value of zero percent hydrogen shortly after thermal runaway venting has occurred.This process of ventilation and keeping gaseous concentrations below the LFL reduces the risk for explosion and potential danger to our firefighters in the case of an emergency.
Presenting to an AHJ
After months and months of assembling engineering drawings, CFD analysis, and reports it was time to submit our first planset for review. To no surprise, the LA County Fire Department had a substantial list of questions pertaining to the BESS along with a unique request that was not mentioned in the code. The fire department requested a “Battery-Specific Annunciator Panel” that would display crucial data from inside the BESS at a remote location. Information such as gas type, detection, enclosure temperature and battery faults all can be seen from this panel, allowing the fire department to avoid risk during an emergency.
Figure 4. ReJoule Annunciator Panel
With the addition of a couple drawings and labels, our planset moved through the fire department and then passed through the building department. At this point in time our team is eager to break ground in Pomona as we reach the final steps of validating our Second Life BESS!
Want to read more?
If you’d like to learn more about our BESS building and permitting experience you may want to check out our soon to be released IEEE paper “Challenges in Deploying a Second-Life Battery System: Engineering, Fire Safety, UL Certifications, and NFPA Requirements.” In this paper we give a detailed background of second life systems along with all of the intricate details of battery grading and some of ReJoules aims to enable the second life battery industry. This paper will be presented at IEEE EESAT 2024 by ReJouligan Eduardo Fonseca. If you read this in time, you can register here. Eduardo will be presenting Tuesday January 30th at 2pm under Technical Session 5: Energy Storage Technologies II and Safety.
Contact us at info@rejouleenergy.com if you want to leverage our technology to test your batteries in or out of the vehicle. What are your thoughts? Did we leave anything out? Please comment and share so we can all engage in conversation and learn from each other.
If this project and/or our work piques your interest, please check out our open positions here.
Cheers,
The ReJouligans
Legal notice:
This document was prepared as a result of work sponsored by the California Energy Commission. It does not necessarily represent the views of the Energy Commission, its employees, or the State of California. Neither the Commission, the State of California, nor the Commission’s employees, contractors, or subcontractors makes any warranty, express or implied, or assumes any legal liability for the information in this document; nor does any party represent that the use of this information will not infringe upon privately owned rights. This document has not been approved or disapproved by the Commission, nor has the Commission passed upon the accuracy of the information in this document.©2021 ReJoule Incorporated. All Rights Reserved.
