Safety Demands for Automotive Hydrogen Storage Systems

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Safety Demands for Automotive Hydrogen Storage
Systems
Helfried Rybin Risk Management E-Mail
helfried.rybin_at_magnasteyr.com
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Content

• Introduction
• Demands for design and reliability
• Methods to minimize risks of design failures
• Validation
• Summary and outlook

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Safety demands for automotive hydrogen storage
systems

• Future hydrogen powered vehicles operated by not
  specially trained people
• Fuel storage systems for vehicles require a
  fail-safe design strategy
• Materials and accessories used shall be
  compatible with hydrogen

Source BMW Group / Munich, Germany
Source BMW Group / Munich, Germany
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Fail-safe design strategy for liquid hydrogen
fuel tanks

• Design
• Redundant systems for safety, i.e. if one system
  fails, another system has to secure the hydrogen
  fuel tank
• This philosophy is reflected by the following
  regulation and standards
• Draft UN ECE Regulation revision 14 and
  14 add. 1
• keeping the probability of critical failures at
  an acceptable level
• risk of hydrogen powered vehicles may not exceed
  the risk of conventional vehicles
• Draft ISO 13985 Liquid Hydrogen Land vehicle
  fuel tanks

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Fail-safe design strategy for liquid hydrogen
fuel tanks

• Reliability
• System reliability is statistically proven over
  the complete life cycle
• Criteria for this reliability are reflected in
• IEC 61508 Functional safety of
  electrical/electronic/programmable
  electronic safety-related systems
• about functional safety of safety-related
  systems
• looks at the whole safety life cycle
• classification into safety integrity levels

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Fail-safe design strategy for liquid hydrogen
fuel tanks
Safety life cycle
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Methods to minimize risks of failures in an early
design phase

• Failure mode and effect analysis (FMEA) ?
• ? is an instrument for avoiding risks and for
  reducing cost for development and manufacturing
  of products
• ? researches the design for possible failures
  due to initiate activities to avoid or reduce
  the risk of this failure
• ? is a method which promotes the
  interdisciplinary team work at an early stage
• ? delivers a documented expertise

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Methods to minimize risks of failures in an early
design phase

• Lifetime estimation by finite element analysis
  simulations
• pressure due to vaporizing hydrogen
• expansion of materials during thermal cycling
• external loads due to mechanical vibrations
• fatigue oriented analysis of stress-time
  histories
• includes both physical tests and simulations
• illustrative animations of the deformation
  behaviour and the resulting stresses
• damage distribution of the cutting plane

Rain flow Analysis
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Safety demands for automotive hydrogen storage
systems
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Functional tests
Non-destructive functional testing on a liquid
hydrogen test bench

• The basic test program includes
• verification of valves and sensors at their
  operating temperatures
• leak rate measurement
• verification of the time for refuelling
• validation of the liquid level indication
• quality of the thermal insulation

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Destructive tests

• Testing of the MLI for flammability
• Reason of this test
• Loss of vacuum causes an condensation of oxygen
  ? atmosphere with liquid oxygen in the vacuum
  space
• Risk of an explosion ? The MLI must not be
  flammable to avoid a fire accident
• Impact test
• mixture of liquid nitrogen and liquid oxygen
  with minimum 50 liquid oxygen
• The impact energy of 79 J/cm² must not cause
  an ignition of the MLI
• 20 samples are required

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Destructive tests
Crash and skid test
Dynamic vibration test
Source BMW Group / Munich, Germany

• In order to examine the
• connection between body and liquid hydrogen
  fuel tank
• the suspension of the inner tank at high
  external loads

• Statistic values for estimating the lifetime
  behaviour
• Inner tank
• at ambient temperature
• at cryogenic temperature (filled with liquid
  hydrogen)

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Destructive tests
Vacuum loss test
Bonfire test
Source Energie Technologie GmbH / Munich,
Germany
Source BAM / Berlin, Germany

• Proves the design of the pressure relief devices
  in case of a degraded thermal insulation.
• Following points are observed
• tank pressure and temperatures
• hydrogen blow-off behaviour
• hydrogen blow-off time

The average temperature in the space 10 mm below
the fuel tank shall be at least 863 K Thermal
autonomy of the liquid hydrogen fuel tank shall
be at least5 minutes Verification of the design
of the pressure relief devices
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Safety demands for automotive hydrogen storage
systems

• Summary
• Fuel storage systems for vehicles require a
  fail-safe design strategy
• Methods to minimize risks of design failures in
  an early design phase
• FMEA
• Lifetime estimation by use of finite element
  analysis
• Non-destructive and destructive tests for
  verification of the fuel system
• Outlook
• to inspire public confidence in this new
  technology
• decrease costs by the standardization of legal
  requirements for hydrogen internationally

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Safety demands for automotive hydrogen storage
systems
Thank you for your attention
Helfried Rybin Risk Management E-Mail
helfried.rybin_at_magnasteyr.com