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Difference between Large-scale fire testing and UL 9540A testing
The energy storage industry is growing at an unprecedented rate, with large installations setting new records year after year. Globally, China, North America and Europe are the major energy storage markets. In addition to this massive growth, energy storage technology continues to innovate. At the same time, there is an increasing focus on safety in the design, installation and operation of products.
The increased deployment of energy storage systems over the past few years has been accompanied by an increasing number of energy storage system fires, and these incidents have raised awareness of the dangers of thermal runaway. As energy storage technology moves closer to our homes and workplaces, the assessment of the potential for fire spread becomes even more urgent. the UL 9540A test standard will provide regulatory agencies and fire departments with the data they require to help the many compliant energy storage systems gain approval for installation.
Fire departments and building inspectors have expressed concerns about the safety of lithium-ion batteries and battery energy storage systems (BESS) permanently installed in mixed-use homes or high-rise buildings. As a result many installation codes require energy storage systems to undergo large-scale fire testing in accordance with UL 9540A to assess the risk of fire spread in the event of failure or thermal runaway of individual units of the energy storage UL 9540A BESS Thermal Runaway Fire Spread Test Methods will help to provide a clearer assessment of the characteristics of a BESS system when a thermal runaway event may occur throughout the life cycle of the system.
When conducting UL 9540A testing for an energy storage system, there are four levels of testing that can be done:
Cell — an individual battery cell
The cell is heated and triggered into thermal runaway in a fixed-capacity combustion bomb, and the gas chromatography is used to analyze the composition of the thermal runaway gas, and then to carry out the test on the explosion limit, explosion pressure, and combustion rate of the thermal runaway gas.
The purpose of this part of the test is to establish a repeatable method of forcing the battery into a thermal runaway state. These methods should be used for module, unit and installation level testing.
Module — a collection of battery cells connected together
The module level test triggers the thermal runaway of one or more battery cells in the module, and through a variety of sophisticated gas analyzing instruments, the gases released from the module after the thermal runaway are comprehensively analyzed to assess their propagation characteristics and possible fire risks within the module.
Unit — a collection of battery modules connected together and installed inside a rack and/or an enclosure
Depending on the different installations of the BESS Unit, test configurations are carried out to test mainly the rate of heat release, gas generation and composition, deflagration and splash hazards, surface temperatures of the target energy storage system and wall, heat fluxes of the target wall and energy storage system as well as of the exit device, and reignition, by triggering the thermal runaway of one or more of the battery cells in the module.
Installation — same setup as the unit test with additional fire suppression systems used
Test Method 1-“Effectiveness of sprinklers” is used to evaluate the effectiveness of sprinkler and explosion protection methods installed in accordance with regulatory requirements.
Test Method 2-“Effectiveness of fireprotection plan” is used to evaluate the effectiveness of other fire suppression systems and explosion protection methods (e.g., combined gaseous extinguishing agents, water mist systems).
Installation level testing is essential to simulate the fire risk of the energy storage system in the actual installation and operating environment, and is an important part of the design verification of the adequacy of the protective measures.
Large-scale fire testing
The principle of large-scale fire testing is to assess the safety of an energy storage system in terms of thermal runaway, fire spread and toxic gas release by simulating the behavior of an actual energy storage system or its components under extreme fire conditions.
The thermal runaway is triggered by heating a single or multiple cells in the PACK, and an ignition needle or lance flame is used to ignite the thermal runaway gas. Gas combustion inside the compartment triggers the spread of thermal runaway of the battery cells again, and the result of continuous flame combustion is observed.
The difference between them
Different purposes:
Large-scale fire testing: The main objective is to simulate possible large-scale fire scenarios and to assess the response of the battery storage system and its surroundings in a large fire situation. The focus is on the behavior of the system in a high-temperature environment and the impact of fire spread on the entire facility. Tests are typically conducted under actual large-scale fire scenarios and may include firewalls, fire suppression systems, and the rate of fire spread under different environmental conditions.
UL 9540A Testing: — Focuses on assessing the risk of thermal runaway propagation by testing the thermal runaway of battery cells, modules, racks, and even entire systems in battery storage systems. The main focus is on how to prevent the spread of thermal runaway to other battery cells or modules in the event of thermal runaway (e.g., spontaneous runaway due to overheating of the battery, internal short circuits, etc.). The purpose of this test is to assess not only the risk of fire, but also possible gas release, flame spread, and other factors that could lead to safety issues.
There are different levels of testing:
Large-scale fire testing: Typically simulates fires in large-scale scenarios, large in scale, involving many devices and conditions, with the goal of seeing how the entire system and its environment performs under extreme fire conditions.
UL 9540A testing: is a tiered test that incorporates progressively more extensive testing from individual battery cells to the entire battery system. Each level of testing is designed to look at the spread of thermal runaway.
While UL 9540A is a critical starting point for battery storage system testing and provides very useful information, it is still limited in scope since the parameters of the test setup may not create the conditions for a fire to ignite. Depending on the type of battery chemistry used, it may be necessary to deviate from the prescribed method in UL 9540A to create a fire in the test enclosure. A large-scale fire testing aims to fulfill those limitations of UL 9540A and provide additional data on what might happen if a system were to fail at a project site as well as ensure the safety features designed into the system function as intended. The definition of A large-scale fire testing per NFPA 855 is the testing of a representative energy storage system that induces a significant fire into the device under test and evaluates whether the fire will spread to adjacent energy storage system units, surrounding equipment, or through an adjacent fire-resistance-rated barrier.