Hydrogen Applications in the Aircraft Industry

TÜV Industrie Service GmbH TÜV SÜD Group

Competence. Certainty. Quality.

Hydrogen Applications in the Aircraft Industry

Gerhard Klein & Bernd Zapf(gerhard.klein/[email protected])

TÜV Industrie Service GmbH TÜV SÜD Group, Germany

Aircraft Fire and Cabin Safety Research Conference Lisbon, Portugal 15-18 November 2004



Contents

• Basic Properties of Hydrogen and its Application for Aircrafts

• Basic Aspects of Risk and Safety

• Automotive Industry

• Tolerable Risk Targets for Hydrogen in the Aircraft Sector

• Implementation of Risk Strategy



Main Engines APU RAT Battery Electrical, Hydraulic and Bleed Air Power

(kW) 1000 550 (ground) 25 3

Conventional Aircraft Power Architecture

Aircraft Power Sources

Air Conditioning

Ice and Rain Protection

Cabin Systems

Engine Starting

Landing gear

Flight Controls Max. Power

Consumption (kW) 500 250 100 300 50 150

Aircraft Main Power Consumers



Some properties of hydrogen and other fuels

g = gaseousl = liquid

Vapor density 0.55 3.2-4 7 1.56 about 1.5 1.4 0.09relative to air

Methane Gasoline Diesel fuel Propane Kerosene Methanol Hydrogen (g) (l) (l) (g) (l) (l) (g)

Flammability limit (Vol.%) 5-16 0.6-8 0.6-6.5 2-10 0.6-7.0 6-36.5 4-75

Ignition temperature (°C) 595 220-280 220 460 about 500 455 585

min. ignition energy (mJ) 0.3 0.24 ./. 0.26 about 0.16 0.14 0.02



Hydrogen – Current Applications



Hydrogen Technology for Aerospace

Combustion Engine

Fuel Cell as APU

Fuel Cell in space Apollo



Fuel cells for Aircrafts – Why?

More efficient power supply - due to FC technology

Low emissions- significant NOx reduction on ground and in flight

Low noise - excellent potential for significant on ground noise reduction

Fuel economy- up to 75% Fuel Reduction on ground- about 30% Fuel Reduction in flight

Heat production Water production



Fuel Cells as Auxiliary Power Systems

Performance evaluation shows two favorable fuel cell processes for aircraft applications:

• Proton Exchange Membrane Fuel Cell – PEMFC

• Solid Oxide Fuel Cell – SOFC

T 60°C – 80°C T 800°C – 1000°C

O2

2H2O

2H2

4e-

4e-

PEMFC SOFC



Main characteristics of Fuel Cells

Operating Temperature

Efficiency

Fuel

Fuel Processing

Carbon Monoxide

Sulfur

Power Density

Maturity Level

approx. 60 – 80°C

up to 40%

kerosene

no residual contamination

CO must be removed

sulfur must be removed

< 1kg/kW

pending on system concept

approx. 800 – 1000°C

up to 60%

kerosene

residual contamination tolerable

less susceptible to CO

less susceptible to sulfur

< 1kg/kW

improvement necessary

PEMFC SOFC



GH2 for Fuel Cell

GH2 LH2 Hydrocarbons

- pressurized tanks - Reformer

- GH2 filters

- conv. Fuel tanks

Veff 400 l/kg(H2)

Weff 24.2 kg/kg(H2)

Veff 15 l/kg(H2)

Weff 7.5 kg/kg(H2)

@ 30bar

Depending on process

Insulated tanks with:

- high mass

- high cost

- shelf life of LH2 marginal

Utilization of hydrogen onboard



The main advantages of reforming kerosene onboard the aircraft are:• high density fuel (4 times higher than LH2)

• easily storable• only one fuel type (kerosene) onboard

There are several reforming processes:

Kerosene

Water Steam

Hydrogen rich gas

Heat

Air

Kerosene

Heat

Temperature: 1300 °CPressure: 30 bar – 70 bar

Temperature: 700 °CPressure: 1 bar

Air

Kerosene

Hydrogen rich gas

Water Steam

Temperature: 700 °CPressure: 2,5 bar – 30 bar

1) Steam Reforming 2) Partial Oxidation

Hydrogen rich gas

3) Autothermal Reforming

Kerosene reforming process


Safety Concepts

Explicit rules for a new technology

Results fromResearch and Development

Experience from operation Quality Standards

Rules and Regulations Social Requirements

System Analysis

Risk Assessment

Safety / Optimization

Analysis

Requirements

Basis

Synthesis

Targets: ’ Acceptance on the part of public and authorities ’ Acceptable safety


Our Services for Hydrogen and Fuel Cell Applications

Safety consultancy

Expertise

Certification

Qualification, Tests

Training

Safety

Quality

Reliability

Economic efficiency



Safety in commercial aircrafts

Procedure:

- Identify hazards, perform a fault hazard analysis- Trace back the hazards to components & their failure modes- Assign a reliability target to each hazard- Design and manufacture component according to this reliability rates using single element integrity, fail-safe-design, ...

This procedure has proven to be very successful in the past because

- commercial aircraft designs don’t change considerably over time- commercial aircraft industry is very conservative in design approaches- commercial aircraft is tightly regulated



Strategies for the implementation of “new” technology or “old” technology in a new context

Requirements derived from

- experiences with similar technology in related areas of application- codes, technical rules

“State of the art” well defined

Requirements derived from

- system analysis (probabilities of failures and their consequences)

Main weak-points are identified Suitable counter-measures can be taken

What‘s the situation for hydrogen?

Safety aspects – Strategies and requirements



Rules - Codes and Standards

73/23/EEClow voltage directive

IEC 62282 fuel cell technologies

98/37/ECindustrial machinery directive

89/336/EECelectromagnetic compatibility

94/9/EC“ATEX directive“

97/23/ECpressure equipment directive

ANSI/CSA FC 1-2004stationary Fuel Cell Power Systems

ISO TC 197Hydrogen Technologies

IEC TC 105fuel cell technologies


Experiences of TÜV SÜD

Stationary H2 Applications

Solar Hydrogen Plant H2MUC MTU PAFC / SOFC / div. PEM / MCFC

Mobile H2 Applications

DaimlerChrysler / VW / BMW / MAN / Proton Motor / Opel / Ford

Portable H2 Applications (FC)Smart Fuel Cell, P21, EnKat, Fronius

1990 1995 2000 2005

Precommercial PhaseStandards

LPG, CNG mobile and stationary applications since 1975



1st conclusion

• ExperiencesExperiences with hydrogen in the automotive and other sectors are only partly of use for aircrafts with respect to

- technical boundary conditions and

- qualification of users

• StandardizationStandardization is on the way, but

- there is no obvious cooperation of the “big 2 players”

- the example of automotive industry shows that standardization takes some time



Tasks

Therefore, the following questions arise:

- How can we push forward the introduction of hydrogen, simultaneously demonstrating it is “safe”,

i. e. free from unacceptable risk?

- What is the residual risk for occupants or flight crew?

- Will it be accepted by the authorities (and the public)?

- How safe is safe enough? What is risk?



What is risk? – Risk Analysis

log (Consequence)

log

(F

req

uen

cy)

acceptable

not acceptable

Risk = Frequency x Consequence

Risk = const.

Risk = const.


21TÜV Industrie Service GmbH TÜV SÜD Group

Consequence

Critical event

External risk reduction facilities

Other technology safety-related systems

Circumstantial / procedural barriers(e.g. operating instructions, unplanned yetbeneficial circumstances)

limited defectsof barriers

• internal• external

Barriers(defenses to the potential escalation

of a critical event)

E/E/PE safety-related systems

Hazard State

Performance of Risk Analysis



IEC 61508: Safety requirements

For each hazard state we have to specify the necessary risk reduction in order to determine the safety integrity1 requirements for the safety-related systems involved:

(from IEC 61508, part 5)

1safety integrity: probability of a safety-related system satisfactorily performing the required safety functions under all stated conditions within a stated period of time.



AMC 25.1309 / AC 25.1309-1

• No single failure will result in a Catastrophic Failure Condition

• Each Catastrophic Failure Condition is extremely impossible

Dealing with hydrogen, we can have catastrophic failure conditions,e. g. leakage of hydrogen to the environment which is not detected by the sensors.

So we have to avoid corresponding single failures and have to show that these conditions are extremely impossible

What is the “necessary risk reduction” in aircraft industry?



AMC 25.1309 / AC 25.1309-1

Allowable Quantitative Probability:

Average Probability per Flight Hour on the Order of

< 10-9

Catastrophic



(1) Utilizing well proven methods for the design and construction of the system (“deterministic approach”) and

(2) Determining the Average Probability per Flight Hour of each Failure Condition using structured methods, such as Fault Tree Analysis, Markov Analysis, or Dependency Diagrams (“probabilistic approach”) ; and

(3) Demonstrating that the sum of the Average Probabilities per Flight Hour of all Catastrophic Failure Conditions caused by systems is of the order of 10-7 or less

AMC 25.1309 / AC 25.1309-1

If it is not technologically or economically practicable to meet the numerical criteria for a Catastrophic Failure Condition, the safety objective may be met by accomplishing all of the following:



(1) Utilising well proven methods for the design and construction of the system (“deterministic approach”) and



AMC 25.1309 / AC 25.1309-1



Proven methods

Failures and Hazards – Scenarios (Munich Airport)

• Accident involving a H2 Vehicle

• Separation of H2 supply lines during filling

MechanicalStresses

Outdoor installation

EnvironmentalStresses

• Deviations of process parameters

• H2 release from safety valves

• Leakage, loss of containment

TechnicalFailures

Explosion /Fire

Overfilling

HumanError


Consequences – Fire tests with Hydrogen and Gasoline Tank

Hydrogen (LH2)

Gasoline

Proven methods


Operating instructions

Alarm and danger avoidance plan

Short briefings

Regular trainings

Maintenance strategy

Proven methods

Human Factor


• Leak proof design of components, suitable materials

• Defined explosion zones and safety areas

• Dominant P&I system

• Emergency-off control-switch system

• Specific process parameters monitored

• non technical measures

• Gas + Fire alarm system

• Infrared camera

General safety equipment for the overall plant

Proven methods



(1) Utilising well proven methods for the design and construction of the system (“deterministic approach”) and



AMC 25.1309 / AC 25.1309-1




Gate1

no contact of valve relay

Q:0,116723

Event1

mechanical failure of valve relay

Q:0,1

Event2

short-circuit of cabling of valve relay

Q:0,0003

Event3

no switch off of valve relay by volt.-reg.

Q:0,006818

Event4

no switch off due to SW-failure

Q:0,01154

Gate2

no data transmission by MC2

Q:6,88409e-006

Event8

short-circuit cabling 2

Q:0,0003

Gate5

no data exchange MC1-MC2

Q:0,022947

Event9

Processor failure serial interface

Q:1,331e-007

Event10

no data transmission HW-failure MC1

Q:0,01154

Event11

no data transmission HW-failure MC2

Q:0,01154

Gate3

short-circuit cabling

Q:9e-008

Event5


Q:0,0003

Event6


Q:0,0003

Logical OR-Gate

Logical AND-Gate

Basic event(„= component + failure mode“)

Determining the Probability – Causal Analysis

Apportionment of quantitative requirements



IEC 61508: Safety Integrity Level (SIL) for E/E/PES

For E/E/PES we expect thatSIL 3 or 2 should be sufficient(see IEC 61508-1, 7.6.2.9).

Existing sensors, PLC, andfire protection systemsshould be able to fulfil theserequirements



System

Operating or

In service* hours

Major failures [h-1] Remarks

Hazard detection systems (sensors)

- Gas detectors - High temperature detectors

16,703,000 8,418,000

44 0

2,6 · 10-6 5,9 · 10-8

Bayes approach

Fire protection systems (final elements)

- Gas system - Foam system

364,000* 88,000*

2 0

5,5 · 10-6 5,7 · 10-6

Bayes approach

Further assumptions: (Logic system) = 10-7/h;

Test period: 1 year

Series connection

SIL 1 (maybe not sufficient)

“Playing with numbers”

LNG-data (Center for Chemical Process Safety)



2nd conclusion

• There seem to be no fundamental difficultiesno fundamental difficulties withthe introduction of hydrogen for aircrafts

• More detailed analysesMore detailed analyses of the - process technology to be used,- E/E/PES, - state of the art of components and systems- organizational measures

- Optimized strategies for maintenance and repair - Regular inspections- Training of personnel

are still necessary to guarantee the required level of safety

• Learning from existing solutionsLearning from existing solutions is encouraged



Hydrogen Technology – Ready for Take-off

with

TÜV Aerospace

[email protected]



The Fourth Triennial The Fourth Triennial International Aircraft Fire and Cabin Safety International Aircraft Fire and Cabin Safety Research ConferenceResearch Conference

The Fourth Triennial The Fourth Triennial International Aircraft Fire and Cabin Safety International Aircraft Fire and Cabin Safety Research ConferenceResearch Conference

Documents

Hydrogen Applications in the Aircraft Industry