Fuel cell gas turbine hybrids a key part of a clean future

Transcription

1 Fuel cell gas turbine hybrids a key part of a clean future The Rolls-Royce development programme for pressurised hybrid fuel cell systems Robert Cunningham Fuel Cells Group 2001 Rolls-Royce plc The information in this document is the property of Rolls-Royce plc and may not be copied or communicated to a third party, or used for any purpose other than that for which it is supplied without the express written consent of Rolls-Royce plc. Whilst this information is given in good faith based upon the latest information available to Rolls-Royce plc, no warranty or representation is given concerning such information, which must not be taken as establishing any contractual or other commitment binding upon Rolls-Royce plc or any of its subsidiary or associated companies.

2 Team GD Agnew 1, CN Berns 1, SA Ali 2, RR Moritz 2, P Butler 1, E Dean 1 C Burrows 1, RD Collins 1, RH Cunningham 1, N Hart 1, MJ Oakley 1, M Pashley 1, N Lapeña-Rey 1, R Scholes 1, O Tarnowski 1, D Wastie 1, R Woodburn 1, G Wright 1 Rolls-Royce Strategic Research Centre, Derby, UK Rolls-Royce, Indianapolis, USA H2net RAL Sep01 2

3 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 H2net RAL Sep01 3

4 High temperature fuel cell hybrids Air side of fuel cell enclosed in gas turbine Fuel cell at pressure but separate flow Air in Exhaust Alternator Recuperator (Heat exchanger) allows air in to be heated by air out Heat from fuel cell provides compression for free High efficiency (60-70%) Recuperator (HX) OUT SOFC Power Electronics Supports capital cost difference from conventional plant (GTs etc) IN Simple pressurised SOFC/GT hybrid showing air side flows only H2net RAL Sep01 4

5 Two ways to reduce $/kw Reduce $ Improve system integration Purpose-designed and integrated components can be spec d to suit fuel cell Early fuel cell demonstrators have used process industry plant General purpose components are over-spec d for specific fuel cell application Reduce stack size and weight Reduces overall system size, weight and cost Increase kw Increase stack efficiency Increase stack power Increasing cell current density requires greater flows Increased current also incurs greater I 2 R losses and reduces efficiency Increase system power and efficiency Pressurised hybrid has higher power and efficiency than raw stack H2net RAL Sep01 5

6 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 management simple Hard to poison high temp stack System simplified no need to backup fuel processing components Thrives on CO Happy with CO 2, NH 3 Simple fuel processing - Internal reforming benefits No need for water gas shift reactors or selective oxidiser Close integration of fuel processing cuts cost Internal reforming provides significant portion of stack cooling Affordable fuel flexibility Can accommodate wide range of CO / H 2 mixtures H2net RAL Sep01 6

7 Pressurised and atmospheric compared Identical stack in pressurised and atmospheric configurations Near term SOFC stack Underlying stack efficiency 50% System efficiency exceeds stack efficiency for pressurised case $/kw better by 680/1050 = 0.65 at pressure if $ cost identical Atmospheric recuperator must be exotic material Pressurised recuperator can be stainless steel Efficiency Net AC LHV Net power kw Recuperator hot inlet temp C Atm 44% Press d 67% H2net RAL Sep01 7

8 Turbomachinery cheaper than heat exchanger Incoming flows can be heated by Heat exchanger Compression in turbomachinery Fuel cell exhaust can be brought down in temperature by Heat exchanger Expansion in turbine Heat exchange is low velocity process (m/s) Large amounts of metal per unit massflow Turbomachinery uses high velocities (300+m/s) Very small amounts of metal per unit massflow Lower cost than heat exchange especially for high temperatures Materials used in turbines are unaffordable in heat exchanger quantities Turbocharging of fuel cell provides blower function Work for compressor comes from fuel cell waste heat H2net RAL Sep01 8

9 Progress towards the vision H2net RAL Sep01 9

10 System and turbogenerator development EU IM-SOFC-GT project Integrated modelling Concept definition Started Feb 2001 Specialised turbomachinery concept development being pursued at Indianapolis Oil-free turbogenerator concepts Interim results from US DOE funded hybrid turbine development reported in ASME Turbo 2001 Magnetic radial bearing High speed Direct drive alternator Aeroderivative radial compressor Magnetic Thrust bearing Two-stage axial turbine Novel oil-free turbogenerator concept from DOE hybrid turbine programme S.A. Ali and R.R Moritz, A Turbogenerator for Fuel Cell/Gas Turbine Hybrid Power Plant H2net RAL Sep01 10

11 Integrated Planar SOFC (IP-SOFC) RR established IP-SOFC stack programme 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 Single IP-SOFC cell H2net RAL Sep01 11

12 1 kw class stack operated in August 2000 H2net RAL Sep01 12

13 1 kw stack on test at Derby (August 2000) 828W output achieved on 97% hydrogen Total power from individual elements operated individually 960W H2net RAL Sep01 13

14 European Union MF-SOFC project Stack development to 20kW Atmospheric demonstration Largest SOFC stack development programme in EU Framework 5 9M gross funding to 2003 DG Research Gilles Lequeux 5 th Framework Programme Energy, environment and sustainable development Partners: Risø Gaz de France Imperial College ACL UK DTI support Only short selection of interim results presented here focussing on Rolls-Royce contribution H2net RAL Sep01 14

15 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 system cost 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) H2net RAL Sep01 15

16 Improved mass transfer Effect of Flowrate 40% H 2 60% N2 3% H 2 O Effect of Flowrate 40% H 2 60% CO2 3% H 2 O 8 7 Module Voltage /V N l /min 3 N l /min 4 N l /min 5 N l /min Module Voltage /V N l /min 3 N l /min 4 N l /min 5 N l /min Module Current /A Module Current /A No mass transfer tail-off seen Down to limiting 0.5V With dilute H2 and low flows Results shown for short 14 cell modules with 7 cells in series at 900 C (June 01) Analysis indicates 75% utilisation achieved in corresponding anode recirculation scheme down to current under 300mA/cm 2 H2net RAL Sep01 16

17 Successful operation on methane DTI internal reforming project Reformer based on flat tube in flow-series with short MF- SOFC module Module run on methane mixture corresponding to operation with re-circulating anode stream 14 cell short module with internal reforming unit (behind) H2net RAL Sep01 17

18 Conclusions 1 Pressurised fuel cell hybrid costs benefit directly and indirectly 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 benefits of mature fuel cell technology Can fully exploit increases in power density (kw/litre) to reduce overall system cost H2net RAL Sep01 18

19 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 H2net RAL Sep01 19