As the use of energy storage systems (ESS) continues to expand, code officials, designers, installers, and members of the fire service are challenged by the lack of clear direction on fire protection and suppression in these installations. The National Fire Protection Association (NFPA) and its research affiliate, the Fire Protection Research Foundation, have proactively worked to ensure that ESS is deployed in as safe a manner as possible – and that the fire service knows how to respond.
The Fire Protection Research Foundation recently completed yet another ESS research project, supported by the Property Insurance Research Group (PIRG), NEC Solutions, and Retriev Technologies, to determine sprinkler protection guidance for grid-connected lithium-ion battery-based ESS for commercial occupancies. As part of the study, FM Global conducted small-scale and large-scale free burn tests and large-scale sprinkler-protected burn tests in order to develop sprinkler protection recommendations. The first-of-its-kind research-testing effort provides important insight into the capabilities of traditional sprinkler designs where popular alternative energy technologies are present.
The drivers for smarter/more efficient energy
The number of ESS installations is dramatically increasing due to businesses, municipalities and consumers looking to tap into renewable energy sources, greater efficiencies, and optimal cost savings. Supplementing renewable energy, load leveling, and peak shaving are just some of the noteworthy advantages of ESS. Audiences are interested in supplementing renewable energy and storing excess power generated by wind turbines or solar cells. Equally attractive is load leveling – a practice that enables utilities to tap into ESS reserves during peak electrical usage hours rather than maintain power production during high volume periods. Peak shaving permits ESS users to draw on reserve power during daytime hours, when the cost of power is higher, and recharge at night when rates are lower. Understandably, this kind of flexibility has made ESS an increasingly attractive option for a range of stakeholders.
A report by Wood Mackenzie Power & Renewable projects that global ESS deployment will expand thirteen times in size over the next 6 years (2018-2024) with the greatest growth occurring in the United States and China. This forecasted trend, coupled with government incentives and consumer interest, are just some of the reasons why it makes sense for responders and those that design, build and maintain facilities to become educated and proactive about ESS safety.
Fires are occurring at battery installations
So, what do we know about the associated risks of ESS?
After nearly two dozen fires at battery installations in South Korea last year alone, that country’s authorities conducted investigations. Reportedly, some manufacturers even requested that customers stop operating their systems until a well-informed decision could be made on root causes, fire patterns, and when to restart operation.
In April of this year, a fire at a battery facility in Arizona in the United States resulted in the hospitalization of eight firefighters who responded to the event. The firefighters reportedly suffered chemical burns and severe inhalation injuries when “an explosion” occurred as they attempted to check on the ESS units. While the cause remains under investigation, the incident has raised many questions about how energy storage systems can be safely designed and installed, and the importance of training firefighters so that they can effectively respond to fires where energy storage system units are present.
The challenges posed by the technology
Recent ESS innovations allow more energy to be stored in less space, therefore elevating the energy density and ultimately increasing the fire and life safety hazards associated with certain ESS. A surplus of stored energy is just one of the many potential hazards aligned with ESS and is a great example of how new technology can often outpace the fire protection codes and standards that we rely upon for guidance, and the emergency response tactics that we have in place. To ensure optimal safety, we need to learn all that we can about these new technologies and the best practices that we can employ to minimize harm.
ESS installations can be located in isolated enclosures in remote fields, in commercial buildings in high density settings, or in residential structures in urban and suburban spaces. Each of these environments present different planning and mitigation considerations for a host of stakeholders looking to develop complete and effective fire protection strategies including fire-rated separation, suppression, and notification systems, as well as emergency response protocol.
Although, the term ESS can be applied to many different systems, in this article we will focus on electrochemical, or battery ESS units and more specifically, lithium-ion-type battery ESS. One of the major concerns with lithium-ion battery ESS is that when something goes wrong with an application, it can discharge flammable and toxic gasses and generate a lot of heat. ESS batteries are typically encased in plastics, too, thus adding to the fire load. A lithium-ion battery fire can be caused by mechanical abuse (crushed, punctured, submerged), thermal abuse (overheating) or electrical abuse (short-circuit, overcharge, rapid discharge).
The NFPA will release its new ESS standard this summer
To help provide answers to different stakeholders interested in ESS technologies, NFPA has been developing the first comprehensive collection of criteria for the fire protection of ESS installations. The highly-anticipated NFPA 855, Standard for the Installation of Stationary Energy Storage Systems is being released this month (September). The document provides requirements based on the technology used in the ESS; the setting where the technology is being installed; the size and separation of ESS installations; and the fire suppression and control systems that are in place.
The Fire Protection Research Foundation has undertaken a number of research projects on battery technologies so that insights could inform the work being done to develop NFPA 855. Research projects delved into general battery hazard and use assessments; firefighter safety in response to incidents at ESS installations; fire mitigation solutions for photovoltaic systems; stranded energy within lithium-ion batteries; and most recently – sprinkler protection of lithium-ion battery energy storage systems.
Free-burn tests of Lithium-Ion ESS
The new report, Development of Sprinkler Protection Guidance for Lithium-Ion Based Energy Storage Systems, was finalized in June. The project built upon previous studies which showed that water and sprinkler systems are the most effective at suppressing lithium-ion battery fires. The study acknowledges that there are still a large number of unknowns and a lack of publicly available data to allow for the formulation of prescriptive design standards for the almost innumerable variables that can arise from installation to installation. The report, however, provides public test data that can serve as the building blocks for a more complete understanding of how to protect these installations and perhaps more importantly – the people who are sharing the building with ESS installations and/or the professionals responding to ESS emergency incidents.
Two types of batteries were involved in the testing, each containing a different chemistry. The two chemistries tested were lithium iron phosphate (LFP) and nickel manganese cobalt oxide (NMC). Both the battery chemistries were subjected to a series of tests including, small-scale, intermediate scale, and large-scale free burn tests and then large scale sprinklered tests. The small-scale free burn tests were used to confirm that the external heating source could produce thermal runaway reactions in the batteries and to provide baseline data on their burning characteristics. In other words – before the larger, more expensive units were tested researchers wanted to be able to predict how they would burn by looking at these batteries on a smaller scale. If the small-scale test showed that the battery was unable to ignite, there wouldn’t have been much of a need to continue the testing. The intermediate-scale free burn tests were conducted to determine the likelihood of a fire spreading to adjacent modules. Finally, large-scale free burn tests were undertaken so that that the overall fire hazard could be evaluated and the performance of sprinkler protection could be estimated.
Each of the free-burn tests demonstrated that the NMC equipment showed a much higher hazard than the LFP equipment in both fire intensity and thermal exposure to the surroundings. In the large-scale free burn test the NMC modules reached a peak heat release rate almost five times as high as the LFP modules. A difference in fire spread was also seen between the LFP and NMC modules, and are detailed in the full report.
Sprinkler testing in an ESS setting
Armed with the findings of the burn testing, researchers then conducted large-scale sprinklered tests that were intended to verify the capability of a traditional sprinkler protection design. While specific criteria for the protection of ESS is not available, the traditional sprinkler protection criteria for extra hazard protection identified in NFPA 13, Standard for Installation of Sprinkler Systems and in the long anticipated NFPA 855 is a density of 12 mm/min with system demand area of 230 m2. The sprinklers used were K81 L/min/bar1/2 quick-response, nominal 74°C temperature rated sprinklers. In order to use a worst-case scenario, sprinklers were installed at 3 m x 3 m spacing and 0.3 meters below the ceiling. There were 49 sprinklers in the design area, with four of those being supplied by water and the remaining 45 being used to indicate operation but were not set to discharge water. There was also a target rack installed to assess fire spread.
The new testing demonstrates the variability in different ESS battery chemistries. While some results can be taken from the research, any changes in battery chemistry, or even construction materials, battery-specific features, or rack design can either increase or decrease the fire hazard of either type of battery.
As a result of the fire tests, recommendations for optimal safety include attention to separation distances (as shown in Figure X); attention to the total room area that is housing the ESS unit, and that the availability of the water supply be 45 minutes times the number of adjacent racks.
Protecting our world and our first responders
Utilizing energy storage systems benefits the planet, our aging energy infrastructure, and pocketbooks. Given all these positive attributes, is it any surprise that this new technology is being embraced globally?
For more than 120 years, the NFPA has worked to ensure that authorities have the guidance needed to safeguard people and property. The new research report on ESS and sprinklers, and the soon-to-be-released ESS standard are two examples of how the NFPA is committed to reducing the risk of fire, electrical, and related hazards in the world. Earlier this year the Association released another valuable resource related to ESS – updated and enhanced NFPA Energy Storage and Solar Systems Safety Training (Fire Service Edition), which helps prepare responders to safely deal with emergency situations involving high voltage commercial and residential energy storage and photovoltaic systems. The self-paced program effectively uses engaging videos, animations (including 3D animations), simulations, and review exercises to address energy storage and solar system concepts including applications, types, and terminology; failure modes and hazards; pre-incident planning; and emergency response procedures.
NFPA’s guiding principle is It’s a Big World Let’s Protect it Together. This is not a slogan. It is a call to action for all of us – and in this particular instance it is a challenge to you to learn all that you can about ESS, the fire protection systems and strategies that can reduce harm and the response techniques that will keep buidlings, occupants, and our first responders safe.
For more information, go to www.nfpa.org/ess