Fire tests show that Austria's tunnels are fit for electric cars
One of many findings of the experimental hearth assessments: If an e-vehicle burns within the tunnel, it turns into hotter, however not essentially extra harmful within the tunnel. Credit score: Lunghammer – TU Graz

The precise potential hazard within the occasion of an accident with an e-car continues to be comparatively unknown, however unsettling photos of e-vehicles on hearth are already widespread. We all know that the power storage methods of e-vehicles based mostly on lithium-ion know-how behave in a different way than standard automotive engines within the occasion of a hearth. However what precisely occurs when e-vehicles catch hearth in a tunnel? How scorching does it get and what gasses are produced? What risks are there for people who find themselves within the tunnel on the time of the accident? What dangers are emergency personnel uncovered to? What injury is there to the tunnel infrastructure? And what’s the best approach for hearth companies to extinguish a burning e-vehicle in a tunnel?

Within the FFG-funded venture “BRAFA—Fireplace Results of Automobiles with Different Drive Programs”, Graz College of Expertise (TU Graz), the College of Leoben, the Austrian Fireplace Brigade Affiliation and the consulting agency ILF Consulting Engineers Austria, supported by ASFINAG and the Federal Ministry for Local weather Safety, Surroundings, Vitality, Mobility, Innovation and Expertise, investigated the safety-relevant results of fires involving battery electrical automobiles (BEVs) in highway tunnels and evaluated strategies for preventing fires. The outcomes of the excellent experimental and numerical investigations present helpful insights, however above all one factor: reassurance. On the idea of those investigations, the potential dangers are to not be assessed as considerably extra crucial than within the case of fires in passenger automobiles with standard combustion engines. “Austrian tunnel methods are match sufficient for the challenges posed by burning e-vehicles,” concludes Peter Sturm, professor on the Institute of Inner Combustion Engines and Thermodynamics at TU Graz.

“Nonetheless, our outcomes point out a considerably elevated potential danger of e-vehicle fires in multistorey automotive parks (primarily indoor stacked automotive parks). And there’s additionally an pressing want for extra funding for additional investigations into tunnel fires involving battery-electric industrial automobiles, i.e. e-busses and e-trucks.”

Burning new automobiles in “Zentrum am Berg”

Whereas the earlier state of information was based mostly on tunnel hearth assessments with particular person battery cells and small battery packs, and the potential danger of whole burning automobiles was derived from this, the venture group gained new data from large-scale actual hearth assessments for the primary time.Within the new tunnel analysis centre “Zentrum am Berg” of the College of Leoben (director: Robert Galler, Professor of Subsurface Engineering), battery modules in addition to three electrically powered and two diesel-powered automobiles had been intentionally set on hearth. The automobiles—compact automobiles, SUVs and vans—had been partly new automobiles inbuilt 2020 and geared up with the newest lithium-ion battery know-how out there available on the market.

Researchers and the fireplace brigade initially discovered themselves in a battle of pursuits through the venture’s hearth assessments. The hearth brigade needed to extinguish the intentionally brought about fires as shortly as potential, whereas the researchers had been involved with accumulating knowledge through the hearth. As a compromise answer, extinguishing makes an attempt had been solely began after an unhindered hearth time of ten minutes. “That can be roughly the escape time and the time till the emergency companies arrive. We had been in a position to achieve helpful knowledge in these first ten minutes, after that it was the fireplace brigade’s flip,” says Peter Sturm.

Fire tests show that Austria's tunnels are fit for electric cars
In the middle of the venture, the fireplace brigade was in a position to take a look at totally different extinguishing strategies for burning e-vehicles in tunnels. Credit score: Lunghammer – TU Graz

Warmth launch and hearth fuel emissions

Greater than 30 temperature sensors had been used to measure the warmth launch fee, i.e. the fireplace load of a automobile. The hearth load of a standard automotive is round 5 megawatts (MW), or roughly equal to a burning stack of 25 wood pallets. The warmth launch fee of the burning e-vehicles within the tunnel, at 6 to 7 MW, was considerably greater than that of the diesel-powered comparability automobiles, however this doesn’t entail any new dangers or risks. As compared, the fireplace load of a standard truck is round 30 MW—and tunnel methods are additionally designed for this. “It does get a little bit bit hotter when e-vehicles burn, nevertheless it does not make it essentially extra harmful within the tunnel. The measured temperatures within the escape space are beneath the 60 diploma Celsius restrict for all hearth assessments. It isn’t a nice temperature, however escaping and firefighting are nonetheless potential,” sums up Peter Sturm.

The one exception is that if there’s a spontaneous response wherein all the battery is absolutely on hearth directly, a noticeably greater warmth launch of as much as 10 MW will be anticipated over a couple of minutes. “Nonetheless, we intentionally induced this spontaneous response so as to have the ability to examine this worst case state of affairs. In the true case, a so-called thermal runaway happens within the battery, wherein the overheating and the fireplace unfold from one cell to the following like a series response. That is why such battery fires additionally final a very long time,” stories Peter Sturm.

Emitted gasses and heavy metals had been additionally the main focus of the venture and had been collected and measured utilizing focused air extraction and suspended fleece blankets. Moreover, greater quantities of hydrogen fluoride and carbon monoxide had been detected within the fires of the e-vehicles. “Nonetheless, the thermally induced smoke stratification within the tunnel causes these extremely concentrated hearth gasses to gather predominantly in higher areas of the tunnel and thus exterior the world related to people. Because of this the escape routes are usually not affected,” explains Peter Sturm. However as an afterthought: “A big a part of the comparatively low danger in highway tunnels is because of the air flow methods. These don’t exist in multistorey automotive parks, for instance, or not less than to not a comparable extent. Because of this fires involving e-vehicles in garages are a unique matter when it comes to hazard and urgently should be investigated extra intently. In any case, our measurement outcomes point out a severe hazard.”

Danger evaluation and tunnel infrastructure

For the reason that “Turismo” danger mannequin at present utilized in Austria, like fashions in different international locations, fully excludes the fireplace of battery-electric automobiles, the security danger for folks within the tunnel was additionally calculated as a part of the venture. Bernhard Kohl from the venture associate chargeable for danger analyses decided that within the excessive case—i.e. when there are solely electrical automobiles within the tunnel—the general danger will increase by about 4 per cent, and the fireplace danger by about 12 per cent in comparison with 100 per cent combustion engines. Nonetheless, it should be taken into consideration right here that it’s tough to derive common conclusions on the idea of those few hearth assessments. For the construction and supplies of the tunnel construction, the drive sort of the burning automobile makes no related distinction. Concrete injury on account of spalling is to be anticipated in fires of business automobiles in each automobile classes; the injury sample is roughly the identical.

Fire tests show that Austria's tunnels are fit for electric cars
Mission supervisor Peter Sturm is chargeable for the world of Transport and Surroundings on the Institute of Inner Combustion Engines and Thermodynamics at TU Graz. Credit score: Lunghammer – TU Graz

Fireplace preventing and contaminated extinguishing water

As a part of the fireplace experiments, the Austrian Fireplace Brigade Affiliation examined numerous extinguishing strategies. Typical firefighting with water labored greatest. “Water is the extinguishing agent of selection due to its superb cooling impact. Nonetheless, expertise exhibits that with lithium-ion batteries, hearth extinguishing solely turns into profitable when the water can attain the within of the battery. Exterior cooling of an solely marginally broken battery is hardly efficient. Earlier operations have proven that the extinguishing time and the extinguishing agent requirement enhance and a number of other 1000 liters of extinguishing water could also be required. If vital, the emergency companies have to make use of the extinguishing water out there within the tunnels,” says Stefan Krausbar of the Austrian Fireplace Brigade Affiliation.

Flame-smothering extinguishing blankets don’t add any worth from the second the fireplace spreads to the battery. The explanation for that is the robust flames close to the bottom, which make it extraordinarily tough to cowl all the automobile tightly with the fireplace blanket and the oxygen self-sufficiency of the battery. The usage of extinguishing lances that inject water instantly into the battery housing, then again, has confirmed to be very efficient. Nonetheless, dealing with the lances is difficult and never with out hazard, so this methodology requires particular coaching for the emergency companies.

The extinguishing water used to combat the fireplace confirmed elevated heavy metallic contamination, particularly with nickel. “It due to this fact goes with out saying that the contaminated extinguishing water collected within the retention basin is costlier to get rid of,” says Günter Rattei from ASFINAG.

Additional hearth assessments with industrial automobiles urgently wanted

Regardless of the various classes realized, venture chief Peter Sturm emphasizes that additional analysis is greater than fascinating. “The venture finances of 250,000 euros left us little or no room for manoeuver.” The hearth results of battery-electric industrial automobiles—busses and vans—may thus solely be scaled up by way of numerical simulations based mostly on assumptions about hearth improvement, hearth length and pollutant launch. There may be at present no strong metrological verification for these assumptions. Complete hearth experiments in large-scale assessments would due to this fact considerably enhance the standard of the data. The identical applies to the concrete hazard of electrical automobile fires in multistorey automotive parks. “Regardless of all the enjoyment concerning the advance of different drive methods, such safety-relevant ‘homework’ should not be uncared for,” says Peter Sturm, interesting to laws and analysis funding.

How harmful are burning electrical automobiles?

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Fireplace assessments present that Austria’s tunnels are match for electrical automobiles (2021, October 7)
retrieved 10 October 2021

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