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Live-fire tests aim to demonstrate physical containment technology. By Michael Puttré . While lithium-ion battery fires are nearly impossible to completely prevent, containing thermal runaway events is crucial. Viridi, a supplier of battery energy storage systems (BESS), recently conducted a live-fire demonstration to show how properly designed cell modules can prevent flame spread. The real problem isnt thermal runaway, Jon Williams, CEO of Viridi, told pv magazine . Its the spread of the fire from one cell to another. Thats where catastrophe happens. During the live demonstration at Viridis Battery Safety Event, held on May 15 at its 43-acre technology center in Buffalo, New York, in collaboration with Soteria Battery Innovation Group, technicians initiated a thermal runaway event in a standard battery pack, causing cell-to-cell spread. Testing of a second pack equipped with Viridis thermal insulation and anti-spread barriers confined the fire to the activated cell without affecting the others. When you turn on a 50-kWh pack and see the energy, the smoke, and the gas coming out, you have a lot of respect for that technology, Williams said. The good news is that its very energy-dense. On the other hand, its very energy-dense. While there are many strategies to reduce the risk of thermal events, from battery chemistry selection to operating environment management, the fact is that when you have a large installed base in the field, something is going to happen. Williams said that JR Linna, Viridis head of research and development, explained to him that theres a one-in-a-million probability of cell failure, regardless of who makes them. Because, at some point, a short circuit can occur that generates enough heat to cause a catastrophic cell failure, regardless of how many sensors are installed in it. Eventually, Williams explained, an event will overwhelm all safety measures. He wondered how it could be stopped, but Linna replied that it really cant be stopped. For this reason, Williams explained that his companys approach is to start with effective chemistry and then design the most durable containment package. Viridi originated in 2018 manufacturing battery packs for the construction industry, where, according to Williams, equipment is routinely handled roughly. The company produces a battery container made of quarter-inch grade 50 steel as a first line of defense against thermal events. The goal was to eliminate physical damage from the equation. “In the compact construction market, equipment suffers considerable damage,” he said. “They lift objects from buildings, load them onto the back of trucks, unload them, they fall into ditches, and end up in ponds. Compact construction equipment is really just sophisticated hammers; they get beaten to death.” In addition to reducing the risk of physical damage to the BESS unit that could lead to a fire, the containment system is designed to prevent the spread of a fire in one cell from affecting adjacent cells. As previously calculated, at some point a battery will short-circuit or fail in such a way that a thermal event occurs. Since it is not always possible to predict where the failure will occur, each cell pack must be as resilient as possible. Williams explained that Viridis BESS modules are designed to contain all three aspects of a thermal runaway event: the tremendous heat (more than 700 degrees Celsius); the explosion of particles; and a shock wave. Fluid-based heat sinks produce channeled steam that prevents adjacent cells from exceeding 170 degrees Celsius, Williams said. Spacers between cells dissipate the concussive force upward, preventing it from compressing the sidewalls of adjacent cells. Fire safety for lithium-ion batteries is a growing concern for a growing number of stakeholders, beyond manufacturers and users, and increasingly including people living near vehicle batteries and BESS installations. As a result, first responders, regulators, and code and standards organizations struggle to implement appropriate standards and techniques. Earlier this month, BESS supplier Sungrow announced that its PowerTitan 2.0 liquid cooling system had received approval from the New York City Fire Department, paving the way for the deployment of its lithium-ion system in the city. Last year, Sungrow conducted its own fire test to demonstrate the PowerTitans thermal management capabilities. In that test, conducted at a test center in China and streamed live to interested parties, explosion relief panels located above the unit where the fire originated automatically vented the fire upward to prevent it from spreading to adjacent battery units. The test proceeded without intervention from personnel or fire suppression systems until the fire was self-extinguishing. According to Mandy Zhang, Sungrows global battery storage product manager, the increasing installation of lithium-ion batteries in many industries is creating a high profile for any fire. This creates a perception of increased fire risk. “We believe that the industry’s focus on fire risk is primarily due to a lack of understanding of fire risk in energy storage systems,” Zhang told pv magazine . “Statistical data shows that the actual fire risk is relatively low. Reports from organizations such as the National Fire Protection Association and the U.S. Consumer Product Safety Commission support this assertion.” Zhang believes that current fire safety certifications and standards in certain regions are lagging behind the growing installed base of lithium-ion batteries. He stated that battery manufacturers must collaborate with relevant standards bodies to stay up-to-date on battery storage and management systems. John Zahurancik, president of the Americas for battery manufacturer Fluence Energy, agrees that expertise must flow seamlessly among suppliers, contractors, operators, and first responders to prevent thermal events from making headlines and skewing public perceptions about lithium-ion battery safety. “When things don’t go well, we should talk about it with the idea that not everyone should have to learn this lesson on their own,” Zahurancik told pv magazine . “We’re part of the American Clean Energy Association (AEA), and one of its main goals is to gather this information and disseminate the best approach to safety.” The industry is responding with more intensive testing and evaluation methods for BESS systems. In March, UL Solutions introduced its new UL 9540A methodology for determining a battery technologys susceptibility to thermal runaway. However, Viridis Williams said the BESS industry and its regulators are still learning how to manage thermal events and how to manage BESSs in general. All the tests currently being conducted are observational, he said. So you can exceed the 9540 level and still have an explosion later due to something unforeseen. We need a dialogue about this. We havent even begun to explore the surface storage we need in this country, so theres still a long way to go. |
