6-8 September 2016, Stavanger, Norway - Arena · PDF file6-8 September 2016, Stavanger, Norway ... –Restricted forcible entry with tools ... These fires were worse than a conventional

Understanding electric vehicle fires

Fire Protection and Safety in Tunnels

6-8 September 2016, Stavanger, Norway

Francesco Colella, PhD

Energy storage All technology is driven by stored energy

• Common forms of energy storage: – Potential energy (height)

– Thermal energy (combustion)

– Electrochemical (batteries)

Any system storing energy has a risk (hazard) associated with sudden and unanticipated release of the stored energy

Stored water (hydraulic): Flooding, erosion

Energy storage hazards

Energy storage hazards

Thermal runaway

• Fires

– All sizes and shapes of Li-ion cells and batteries

• Explosions

– Predominantly in larger cells and batteries

• Human exposure to failure debris

Energy storage hazards & electric vehicles

• Characterization of electric vehicle fires requires understanding battery fire dynamics:

– Difficult to extrapolate between different families because there is not a “standard” cell

– Electrolyte is flammable

Electric vehicles fires

Small format cells 0–10 Wh (0–3 Ah)

Large format cells ~100 Wh (~30 Ah)

EV battery module (10–20 cells)

~2000 Wh (~600 Ah)

Hybrid vehicle pack ~500 Wh (~135 Ah)

Plug-in EV pack (multiple modules)

~20,000 Wh (~5500 Ah)

High performance EV pack (multiple modules)

~85,000 Wh (20000 Ah)

Large Transport & Grid Storage Packs

>100 kWh

Not to scale

Hybrid vehicle pack = ~100 x cell phone cells

EV battery module = >200 x cell phone cells

Energy storage hazards – Li-Ion batteries

What is the fuel?

What is the heat release rate?

Suppression strategies?

Understanding electric vehicles fires

Small Scale

Battery Testing

Small Scale

Battery Testing

• Cause thermal runaway failures in small format cells

• Collect and analyze gases released

• Cell tested: – 2.1 Ah (7.7 Wh) li-ion pouch cell

– Negative: Graphite

– Positive: LiCoO2

– State of charge during tests: Charged to 50%, 100%.

– Cells were unconstrained during the tests

Electric vehicles fires – vented gases

Goal: Measure the composition and quantity of gas released during a thermal event in a Li-ion cell

Cell Test Chamber

Gas

Collection

Canister


• Total volume of gas released:

– 0.8 L at 50% SOC, 0.1 L/Wh (litres per Watt-hour) at STP

– 2.5 L at 100% SOC, 0.32 L/Wh

Fuel source

Amount of fuel involved


Gas50% SOC

(%vol)100% SOC

(%vol)150% SOC

(%vol)

Roth et al.*(%vol)

Test 1/Test 2

Carbon Dioxide 32 30 20.9 61.4/75.8

Carbon Monoxide 3.61 22.9 24.5 15.1/6.4

Hydrogen 30 27.7 29.7 5.1/5.9

Total Hydrocarbons 34 19.3 24 7.4/1.9

• Battery vent gases are more energetic than pure hydrocarbons

• Flammability range of vent gases is wider than pure hydrocarbons


Electric vehicles fires – HRR

INCOMING

SUPPLY

fuelm

Conical Heater

LOAD CELLCONTROL VOLUME

HOOD

EXHAUST

GASES

LASER

EXTINCTION

PITOT

TUBE

SAMPLE

PUMP

THERMOCOUPLE

FILTERING AND

CONDENSING

O2

CO/CO2

ANALYZER

am

em

EXHAUST FAN

SOOT VOLUME

FRACTIONFLOW RATE

MASS LOSS

PARAMAGNETIC

ANALYSER

INFRARED

TECHNOLOGY

Traditional calorimetry techniques (i.e. O2

consumption and CO2) need to be modified

to account for:

• Complex chemistry

• Self generated oxygen from active material

decomposition

Kapton Tape, 0.24%

Label, 0.47% Outer Packaging, 4.30%

Separator, 6.40%

Al Cathode (LiCoO2 coated), 42.40%

Cathode Tab, 0.87%

Cu Anode (Graphite coated), 34.90%

Anode Tab, 0.93% Electrolyte, 9.49%

Pouch cell composition:

– Large amount of inorganic material

Electric vehicles Fires – HRR

Material Net Heat of Combustion (kJ/g)

Douglas Fir 19.6

PMMA (clear plastic) 25

50% SOC li-ion cell 28.1

Acetone 30.8

Gasoline 44.1

Electric vehicles fires – HRR

Small Scale

Battery Testing

HRR testing

EV Battery Pack

HRR testing - EV battery pack

• Free burn.

• 400kW propane for ignition.

• HRR measured using O2 consumption

• Instrumented with TCs and heat flux gauges

• Max HRR 700 kW

• The thermal runaway occurred in stages.

• Visible flaming ceased after 1.5 h.

• 3 hours after extinction, external temperature were as high as 150˚C.

• HF not detected.

HRR testing - EV battery pack

Small Scale

Battery Testing

Full Scale Suppression

Testing

• 400kW propane for ignition.

• Instrumented with TCs, heat flux gauges, and voltage measurements.

• Suppression efforts – Water flow 125 gpm

– 4 Firefighters

– 2 on hose line, 2 support

– Restricted forcible entry with tools

Full scale suppression testing

Top View

3 suppression tests (1 w/ interior components)

Full scale suppression testing – Battery “A”

1 minute

Battery Only Battery w/ interiors


2 minutes



4 minutes



8 minutes (burners off)



9 minutes (suppression starts)



12 minutes



25 minutes



Test Suppression Time (min)

Total Water Flow (gal)

Comments

A1 2.2 275 Battery Only

A2 3.5 442 Battery Only

A3 9.8 1060 Battery + Interior

Components

– No projectiles

– Popping heard/Arcing observed

– Off-gassing preceded re-ignition events

– No significant current measured at nozzle

– Re-ignition 22 hours after test


Top View

3 suppression tests (1 w/ interior components)

Full scale suppression testing – Battery “B”

Test Suppression Time (min)

Total Water Flow (gal)

Comments

B1 14.03 1754 Battery Only

B2 21.37 2639 Battery Only

B3 9.32 1165 Battery + Interior

Components

– No projectiles

– Popping heard/Arcing observed

– Off-gassing preceded re-ignition events

– No significant current measured at nozzle

Full scale suppression testing – Battery “B”

Unable to extinguish the fire - concentrated efforts on cooling the metal

There was “tremendous heat”

Floorboard makes fire harder to extinguish

These fires were worse than a conventional vehicle fire,

harder to extinguish

EV fire behaves differently from traditional fire

Firefighter response: key quotes

Conclusions (1)

The complete evaluation of EV fire hazards requires a multi-step analysis involving small and large scale testing.

• Vent gas composition and flammability.

• Battery and battery module HRR.

• Effectiveness of suppression agents and suppression time.

Conclusions (2)

Full scale suppression tests:

• Water alone suppressed the EV fires.

• Water requirements depend on battery pack sizes and layout.

• Water flows increased over traditional ICE.

• First responders should be prepared for extended periods of suppression operations and monitoring during overhaul operations due to potential battery re-ignition.

Any questions? Francesco Colella Ph.D.

Email: [email protected]

Documents

6-8 September 2016, Stavanger, Norway - Arena · PDF file6-8 September 2016, Stavanger, Norway ... –Restricted forcible entry with tools ... These fires were worse than a conventional