With our mega survey on electric cars, we brought to light an issue related to the risk of fire in underground car parks which we also spoke about at the first national conference on the safety of lithium batteries. A work that made us discover various experiences and solutions to counter the increased risk introduced by lithium batteries, which currently remains and should not be underestimated. This article is part of a special on the extinction of lithium batteries that we wanted to create to talk about this problem from another angle, telling you the different solutions currently on the market. Among the many and diverse solutions that companies specializing in fire protection systems are implementing, some have proven to be more effective and also suitable for confined and difficult to access spaces, such as garages, garages and workshops. We made contact with Fogtecthe German company, exclusively distributed in Italy by Pierre Srl, which developed the homonymous system tested and NFPA 750, EN 14972 and VdS 3188 certifiedlike, how fire protection for car parks and electric vehicle charging systems. Here’s how it works.

HIGH PRESSURE WATER MIST AGAINST LITHIUM BATTERY FIRES

The system Fogtec is based on the production of water misti.e. a cloud of water sprayed at high pressure as an extinguishing agent, and monitoring sensors and detection of the principles of fire to fight the flames in the bud and prevent the phenomena of Thermal runaway in lithium batteries. According to the company FogTecthe very fine water mist is proven to be very effective in fires and by comparison tests with other extinguishing agents at the IFAB – Independent Federal Institute for Applied Fire Safety Research in Germany, presents several benefits:

• the micro-droplets allow flame control and suppression acting on the three sides of the fire triangle (oxygen – fuel – heat);
• there drop size of water obtained by high pressure atomizing nozzles increases the useful water volume, thus reducing costs. With 1 liter of water, a corresponding volume of water vapor equal to 1650 liters is generated. Also for each liter of water you can generate one 200 m reaction surface² with the Fogtec system at high pressure producing droplets 0.01 mm in diameter, against 20 m² with traditional sprinkler that sprays drops of 1 mm in diameter;
• tests carried out in Germany at the independent laboratory IFAB and certified by TÜV SÜD and DEKRA show that the smaller the droplets, the better the effect on fire control. Also with water pressures between 60 and 200 bar the micro-droplets acquire a kinetic energy capable of defeating even the electrolytic gases that are released during the fire of a lithium battery, helping to make them fall to the ground;
• evaporation of water droplets reduces the amount of oxygen only at the source fire, without creating danger for people.

LITHIUM-ION BATTERY FIRE TEST WITH FOGTEC WATER MIST

Demonstrate the effectiveness of the systems water mist, Fogtec made some fire test at the IFAB test laboratory in Faßberg, Germany. The test results presented in the attached videos provided the necessary elements for the development of Fogtec’s fire protection solutions for underground car parks and garages certified by TÜV SÜD and DEKRA. The real-scale simulated fire scenarios are based on the assessments from the SUVEREN research project (Safety of underground urban structures through the use of new energy vectors). The research consortium with the Federal Institute for Materials Research and Testing (BAM) and the Society for the Study of Tunnels and Transport Systems (STUVA), has set itself the goal of study several aspects of fire riskincluding vehicles equipped with lithium batteries and charging stations.

During the tests, the extinguishing capacities of different solutions (Sprinklers; High and low pressure water mist; F-500; Foam; CO²; Nitrogen; Novec) were evaluated using different parameters. For each system, one was generated fire from cells and cell modules with a state of charge level of 100% and the capacity of:

• 307Wh total electrical capacity for cells lithium ion;
• 879Wh total electrical capacity for modules lithium ions.

Cells and battery modules were placed next to each other in individual tests to ensure direct heat transfer from lit cells to adjacent cells. Li-ion battery thermal runaway was triggered by using resistance heating elements always in the same position.

Several tests were carried out during the tests measures to verify the effectiveness of fire extinguishers in firefighting. For example through:

• release rate of heat (HRR);
• temperature air at different heights;
• wall temperature internal and external at different heights of the boxes in which the tests were carried out;
• a concentration of gas measured by Fourier Transform Infrared (FTIR) spectroscopy
• video camera and infrared camera;
• optical detectors, ionization detectors and heat conducting cables.

In IFAB test applications, the system based on Fogtec water mist it was operated for 30 minutes by a high pressure pump with nozzle outlet 100 bar. In the cell shutdown test, a single nozzle was placed on the ceiling of the box. During the stop test of the battery modules THE 14 nozzles were arranged on the 3 vertical walls of the box.

LITHIUM BATTERY SHUTDOWN TEST RESULTS: WATER MIST VS SPRINKLER

The high-pressure water jet has proven to be particularly suitable for fighting fires in vehicles equipped with lithium batteries. Compared to sprinklers, the small drops of water nebulized they showed a particularly high cooling capacity. After about 10 minutes, the temperature measured on the ceiling is output 218°C with water mist active, and with a downward curve. Whereas it is 580°C with sprinkler works and takes about 30 minutes to come down to the average temperature levels measured with Water Mist.

“THE return to calm drums this is the only way to reduce the spread of thermal runaway. High pressure water mist has proven to be the best cooling agent”explains the company. “Furthermore, 50% of all the energy in a battery fire is caused by the combustion of electrolytic gases. Reducing heat slows the spread of thermal runaway, as well as secondary fires”. It is certainly a solution Interesting, validated by regulated standards and certified by third partiesto reduce the risk of fire spreading not only in garages and charging stations, but also in so-called BESS systems (Battery energy storage system). With the spread of BESS systems, the company explains that an upsurge in fires like the one at Tesla in California is to be expected, mainly due to the lack of clear fire protection regulations for these gigantic banks. power supply.