Article - Danfoss SEM-SAFE high-pressure water mist systems effectively suppress fires in EVs

Article - Danfoss SEM-SAFE high-pressure water mist systems effectively suppress fires in EVsHowever, fires in EVs still pose a challenge to fire safety engineers. They tend to spread faster than ICE vehicle fires, and they are hard to suppress using conventional sprinkler systems: the lithium-ion batteries are typically located underneath the EVs, and the sprinkler systems found in many buildings designed and built for ICE vehicles are incapable of handling this type of shielded fire because the water from the sprinklers simply cannot reach it. Tested to be an effective solution However, other fire suppression methods have proved themselves effective against fires in EVs: in 2023, Danfoss Fire Safety and Siemens conducted a joint test in cooperation with the Danish Institute of Fire and Security Technology (DBI). The results show that a solution combining fast and effective smoke detectors with high-pressure water mist systems provides effective fire detection and suppression performance. In the test, a simulated garage space was constructed from steel shipping containers. An EV was placed in the centre of the space with an ICE vehicle on either side. Point-type Siemens smoke detectors and Danfoss SEM-SAFE® high- pressure water mist nozzles were installed, along with cameras and temperature sensors to assess the fire detection and suppression performance of the test set-up. A fire was then started in the EV battery. How a fire in an EV starts and spreads EVs have built-in fire safety mechanisms designed to prevent battery fires, but if those mechanisms fail, a damaged, faulty, or ageing battery can cause a fire, typically because the battery separator is damaged. The resulting short circuit causes the battery to warm up, and at around 70 °C, the battery electrolyte starts to evaporate and eventually escapes from the battery cell in an event known as off-gassing. If the process is not stopped, the temperature continues to increase until the battery separator fails, which leads to a catastrophic temperature increase (called thermal runaway) and the explosive combustion of the electrolyte gases if there is an ignition source. The resulting explosive combustion of the electrolyte vapour, with intense heat and highly toxic smoke, can lead to multi-vehicle fires that damage or destroy vehicles and building structures – and pose a major safety hazard to building occupants. Promising test results In a high-pressure water mist system such as the one tested by Danfoss Fire Safety and Siemens, the detection system activates the nozzles in the affected area. Water is pushed through the nozzles at high pressure, creating an extremely fine mist that covers the area. The mist has good fire suppression properties because it simultaneously lowers the temperature and removes oxygen from the air near the fire. In the test, two ICE vehicles were placed close to the EV, and a fire was then started in the EV battery. The test set-up closely resembles real parking garage conditions. ® Danfoss Fire Safety A/S · Phone: +45 7488 7800 · firesafety@danfoss.com · www.semsafe.danfoss.comPage 1Page 3