www.cranfield.ac.uk

eTaxi Fuel Cell System -Feasibility for Low Cost Carriers

Dr Craig Lawson CEng, MRAeS, FHEA

Senior Lecturer in Airframe Systems Design

Centre for Aeronautics, Cranfield University

17th October 2016

2

Overview

• General Benefits of eTaxi

• Environmental Impact of Aircraft Taxi

• Green Taxi Commercial Options

• easyJet Proposed System Concept

• Cranfield Aircraft and System Level Studies

• The Hydrogen Economy

• Hydrogen Storage on Aircraft

• Status and Summary

eTaxi Fuel Cell System - Feasibility for Low Cost Carriers

3

General Benefits of eTaxi

• Reduced Operating Costs

• Reversing capability

• Up to 4% reduction in block fuel on short haul

• Ground positioning on time

• Faster turnaround

• Increased tyre life (Main gear)

• Increased wheel brake life

• Reduced Airfield Emissions

• CO2, NOx, etc circa 50%

• Eradication with fuel cell system

• Noise

• Improved Safety

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• In 2002 56% of NOx at LHR was due to Aircraft ground emissions

• Taxi time is increasing at many airports

Environmental Impact of Aircraft Taxi

• On average 6% of fuel is burnt on the

ground

• B737/A320

• Typically 200 kg on taxi

• Single engine taxi

• 5 M tonnes fleet per annum

• USA 2007 Study

• 150 M minutes taxi-out

• 6 M tons CO2 on taxi-out

Figure from Dzikus et al “Potential for Fuel Reduction through Electric Taxiing”, AIAA (2011)

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Green Taxi Commercial Options

• Wheel Tug - Retrofit Nose Gear Solution

• APU modification not required

• Traction: A320 <10% load on NLG

• Wet/Ice – Slope - Headwind

• Proprietary high torque motor drive

• 150 kg

Advantages Disadvantages

Simplicity of integration Traction: Skidding risk on wet

or icy surface

Lightweight New Chorus motor technology

Ground operation time-saving High torque needed

Maintainability Requires APU - consumes fuel

Images courtesy of WheelTug

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Green Taxi Commercial Options

• EGTS – Electric Green Taxi System

• SAFRAN-Honeywell

• Project cancelled July 2016

• oil price

• economic environment

• APU modification required

• 400 kg

Advantages Disadvantages

Mature Technologies Requires up-rated APU

generator - consumes fuel

Complex integration and

maintenance

Cooling efficiency of brakes

reduced

Images courtesy of EGTS

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Green Taxi Commercial Options

• TaxiBot - Ground Based Solution

• Vehicle docked with aircraft

• Pilot controls taxi

• The only globally environmentally

beneficial option for long range aircraft

Advantages Disadvantages

Mature Technologies Operation cost

No impact on aircraft systems Airport dependant

No impact on landing gear

fatigue life

Taxi-out only

Images courtesy of TaxiBot

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easyJet Proposed System Concept

• Idea generated from competition with

Cranfield Students

• Fuel Cell Green Taxi selected

• Rationale

• EGTS required a doubling of APU

generator capacity

• Short haul operations

• Relatively empty hold

• Potable water

Image courtesy of easyJet

• Feasibility Calculations Basis A320• 3 kg fuel burn per

100 kg system per hour• Single engine taxi 320kg /

hour• Typically 200 kg fuel burn at

gate and on Taxi

Figures for easyJet press release May 2016 https://www.theengineer.co.uk/plane-savings-on-the-deck-reducing-the-impact-of-taxiing/

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Cranfield Aircraft and System Level Studies A-16m

A-16m Key Metrics

Cruise Speed 0.65 M

Cruise Altitude 11,000 m

Range 5,000 nm

Length 50 m

Wingspan 42 m

Wing area 138.42 m2

MTOM 75,335 kg

OEM 44,187 kg

Power Plants2 x TP400-D6 engine

8 Blades (114kN)

• MSc AVD student Group Design Project• 44 postgraduates for 5 months• High staff involvement• Supported by Airbus• Starting point Airbus A30X-C2

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74%

16%

10% Electricmotors

MotorDrive

Others

95kg

A-16m Green Taxi System Design

• Design Parameters:• Weight on Nose Landing Gear: 12-16%• Acceleration rate: 0.25 m/s²

(ICAO prescribe 0.18 m/s²) • Total Rolling Resisting Force= 6 kN• Acceleration Force = 25 kN• Power @ 25 km/h = 140 kW• Max Torque per wheel = 4,744 Nm

• Component Selection:• Two Parker TK 205 Motors with Chorus

Torque Driver 4,950 Nm

• APU is a Fuel Cell System with Methanol / H2 Reformer or Alternate H2 feed

• 400 kW• 270 kW Ground Power

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Fue

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Flight Range Mission, km

A-16m Green Taxi System Aircraft Level Performance

• Extra Fuel Burn Carrying the NLG eTaxiSystem @95 kg

• Cranfield Calculation for A16m 10-40 kg

• easyJet Rule of Thumb (for A320) 8-32 kg

• Engines off Ground Fuel Burn Savings• 7% Thrust for 25 mins (no start-

stop) 100 kg• 200 kg (typical easyJet A320

figure)

• Trip Fuel Savings• Cranfield Calculation for A-16m

0.3% to 3%• EGTS forecast up to 4% for A320

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0 100 200 300 400

Fue

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Electric Taxi System weight, kg

1000nmrange

2000nmrange

3000nmrange

3500nmrange

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The Hydrogen Economy

• The Automotive Sector• All major manufacturers have live H2 Vehicle

Projects

• Production Vehicles• Honda FCX Clarity (2008-14)• Hyundai ix35 FCEV (2012)

• < 1,000 sales• Toyota Mirai (2015)

• 5,000 sales to date• £60,000

• HyFive EU Project• £31M Development of H2 Vehicles and

Infrastructure

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The Hydrogen Economy

• H2 Filling Stations• Sainsbury's Hendon (Air Products)• Hatton Cross (Air Products)• NPL Twickenham (ITM Power)• Rainham (ITM Power)

• Gatwick?• 1.5 hectares• Solar Array and 2 wind turbines• 500 kg H2 / day

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• Storage of Hydrogen

• Cryogenic

• Gaseous

• 700 bar storage – heavy tank – 4.7 MJ/L (Jet A-1 36 MJ/L)

• Pellets form Cella Energy

• 1000 L H2 / kg

• MJ/L ‘comparable’ to 700 bar

• Standards need to be developed

• SAE AIR 6464 H2 Fuel Cells on Aircraft

• How much H2 do we need to store for Taxi-out Taxi-in?

• H2 120 MJ/kg

• Jet A-1 45 MJ/kg

• Jet Engine Propulsive efficiency vs Fuel Cell System efficiency

• 20 kg typical taxi

Hydrogen Storage on Aircraft

Image courtesy of Cella Energy

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• The Next Steps

• Design of stand alone ground power PEM fuel cell system for LD3-45 container

• Partnership agreements and funding

• Certification and integration studies

• Demonstration

• Ground based lab

• Ground based truck

• Aircraft

• Current Status

• Technology is proven in lab and ground test

• Environmental benefits are reasonably well understood and quantified

• Emissions reduction benefit for short haul is established

eTaxi Fuel Cell System Feasibility