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Fuel cell gas turbine hybrids – akey part of a clean futureThe Rolls-Royce development programmefor pressurised hybrid fuel cell systemsRobert Cunningham – Fuel Cells Group
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Team
GD Agnew1, CN Berns1, SA Ali2, RR Moritz2, P Butler1, E Dean1
C Burrows1, RD Collins1, RH Cunningham1, N Hart1, MJ Oakley1,M Pashley1, N Lapeña-Rey1, R Scholes1, O Tarnowski1,D Wastie1, R Woodburn1 , G Wright1
� Rolls-Royce Strategic Research Centre, Derby, UK� Rolls-Royce, Indianapolis, USA
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Overview
The Rolls-Royce vision of pressurised hybrids� Pressurised hybrids� Reducing $/kW for SOFC in general� Benefits of pressurised operation at high temperature� Comparison of atmospheric and pressurised systems
Progress towards the vision� System and turbogenerator development� Stack module development� Internal reforming
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High temperature fuel cell hybrids� Air side of fuel cell enclosed in gas
turbine– Fuel cell at pressure but separate
flow� Recuperator (Heat exchanger)
allows air in to be heated by air out� Heat from fuel cell provides
compression for free� High efficiency (60-70%)
– Supports capital cost differencefrom conventional plant (GTs etc)
Simple pressurised SOFC/GT hybridshowing air side flows only
OUT
IN
PowerElectronicsSOFC
Recuperator(HX)
AlternatorAir in Exhaust
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Two ways to reduce $/kW
Reduce $� Improve system integration
– Purpose-designed andintegrated components can bespec’d to suit fuel cell
� Early fuel cell demonstratorshave used process industryplant
– General purpose componentsare over-spec’d for specific fuelcell application
� Reduce stack size and weight– Reduces overall system size,
weight and cost
Increase kW� Increase stack efficiency� Increase stack power
– Increasing cell current densityrequires greater flows
– Increased current also incursgreater I2R losses andreduces efficiency
� Increase system power andefficiency
– Pressurised hybrid has higherpower and efficiency than rawstack
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Cost reduction with SOFC systems in general� SOFC can use cheap electrode
materials– High temperature chemistry has
fast kinetics� Anode exhaust provides water
for reforming– No need for elaborate water
management/humidification� Easy to use heat output from
stack– 800+°C difference with ambient
makes thermal managementsimple
� Hard to poison high temp stack– System simplified – no need to
backup fuel processingcomponents
– Thrives on CO– Happy with CO2, NH3
� Simple fuel processing -Internal reforming benefits
– No need for water gas shiftreactors or selective oxidiser
– Close integration of fuelprocessing cuts cost
– Internal reforming providessignificant portion of stackcooling
� Affordable fuel flexibility– Can accommodate wide range
of CO / H2 mixtures
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Pressurised and atmospheric compared
� Identical stack in pressurisedand atmospheric configurations
– Near term SOFC stack– Underlying stack efficiency 50%– System efficiency exceeds
stack efficiency for pressurisedcase
� $/kW better by 680/1050 = 0.65at pressure if $ cost identical
– Atmospheric recuperator mustbe exotic material
– Pressurised recuperator can bestainless steel
576871Recuperator
hot inlettemp °C
1051684Net powerkW
67%44%EfficiencyNet AC LHV
Press’dAtm
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Turbomachinery cheaper than heat exchanger
� Incoming flows can beheated by
– Heat exchanger– Compression in
turbomachinery� Fuel cell exhaust can be
brought down in temperatureby
– Heat exchanger– Expansion in turbine
� Heat exchange is lowvelocity process (m/s)
– Large amounts of metal perunit massflow
� Turbomachinery uses highvelocities (300+m/s)
– Very small amounts of metalper unit massflow
– Lower cost than heatexchange especially for hightemperatures
– Materials used in turbinesare unaffordable in heatexchanger quantities
� Turbocharging of fuel cellprovides blower function
– Work for compressor comesfrom fuel cell waste heat
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Progress towards the vision
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System and turbogenerator development
� EU IM-SOFC-GT project– Integrated modelling– Concept definition– Started Feb 2001
� Specialised turbomachineryconcept development beingpursued at Indianapolis
– Oil-free turbogeneratorconcepts
– Interim results from USDOE funded hybrid turbinedevelopment reported inASME Turbo 2001†
Two-stageaxial turbineMagnetic
radialbearing
High speedDirect drivealternator
Aeroderivativeradial
compressor
MagneticThrust bearing
† S.A. Ali and R.R Moritz, A Turbogenerator for Fuel Cell/Gas Turbine Hybrid Power Plant
Novel oil-free turbogenerator conceptfrom DOE hybrid turbine programme
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� RR established IP-SOFC stackprogramme 9 years ago
– World leading stack concept– Strong on manufacturing cost
� Focus now on stacks and systems– Optimise for overall performance– Results are for stacks
– Not just cells� Leading EU programmes
– MF-SOFC– Stack development
– IM-SOFC-GT– Integrated modeling and concept
design of hybrids� Participating in EU programme
– CORE– Component Reliability
IP-SOFC stack modules
Integrated Planar SOFC (IP-SOFC)
SingleIP-SOFC
cell
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1 kW class stack operated in August 2000
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1 kW stack on test at Derby (August 2000)
� 828W output achieved on 97% hydrogen� Total power from individual elements operated individually 960W
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European Union MF-SOFC project
� Stack development to 20kW� Atmospheric demonstration� Largest SOFC stack
development programme in EUFramework 5
– €9M gross funding to 2003
� Partners:RisøGaz de FranceImperial CollegeACLUK DTI support
� DG Research– Gilles Lequeux
� 5th Framework Programme� Energy, environment and
sustainable development
� Only short selection ofinterim results presentedhere focussing onRolls-Royce contribution
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Revised stack design� Addresses issues raised in 1kW
stack� Uses novel Rolls-Royce concept for
a pressurised stack� Thin tubes
– x3 on kW/litre – improves systemcost significantly
– Improved heat and mass transfer� New manifolding design based on
bundles– Much improved compliance and
potential leakage– Improved flexibility on internal
reforming– x10 reduction in manifolding 40 cell modules (new design)
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Improved mass transfer
� No mass transfer tail-off seen– Down to limiting 0.5V– With dilute H2 and low flows
� Analysis indicates 75% utilisation achieved in correspondinganode recirculation scheme down to current under 300mA/cm2
Effect of Flowrate 40% H2 60% N2 3% H2O
0
1
2
3
4
5
6
7
8
0 1 2 3 4 5
Module Current /A
Mod
ule
Volta
ge /V
2 N l /min
3 N l /min
4 N l /min
5 N l /min
Effect of Flowrate 40% H2 60% CO2 3% H2O
0
1
2
3
4
5
6
7
0 1 2 3 4
Module Current /A
Mod
ule
Volta
ge /V
2 N l /min
3 N l /min
4 N l /min
5 N l /min
Results shown for short 14 cell modules with7 cells in series at 900°C (June ’01)
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Successful operation on methane
� DTI internal reformingproject
� Reformer based on flat tubein flow-series with short MF-SOFC module
� Module run on methanemixture corresponding tooperation with re-circulatinganode stream
14 cell short module with internalreforming unit (behind)
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Conclusions 1
� Pressurised fuel cell hybrid costs benefit directly andindirectly from pressurisation
� $/kW potential for hybrids exceeds that of atmospheric units– Cost of GT and pressure vessel paid for by other savings
� Pressurised hybrids have greater potential to exploit benefitsof mature fuel cell technology
– Can fully exploit increases in power density (kW/litre) to reduceoverall system cost
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Conclusions 2� World-class results from Rolls-Royce stack development
programme– 1kW stack operation– Operation of new Rolls-Royce stack design– 300W/litre at $300/kW (100MW pa)– At intended operating current:
– 75% fuel utilisation– Under 2%/1000hrs degradation
– Operation on methane mixture� Funding from the following sources is gratefully
acknowledged– European Union– US Department Of Energy– UK Department of Trade and Industry