The Role of Fuel Cells in a Sustainable Energy Economy

Transcription

1 The Role of Fuel Cells in a Sustainable Energy Economy Energy Futures Sustainable Development in Energy, February 16 th 2005 Nigel Brandon Shell Chair in Sustainable Development in Energy, Faculty of Engineering Page no./ref Imperial College London

2 Introduction Introduction to Fuel Cells. Fuel Cells for high efficiency. SOFC-GT Hybrids. Micro-CHP. Renewable Fuels. Biofuels. Hydrogen. Summary.

3 Fuel Cell Applications Personal Transport Ford Focus Fuel Cell Hybrid Daimler-Chrysler Fuel Cell Vehicle General Motors Autonomy Yamaha Fuel Cell Scooter

4 Fuel Cell Applications Public Transport Mercedes-Benz Citaro Fuel Cell Bus

5 Fuel Cell Applications - Portable Casio fuel cell powered notebook Hitachi methanol fuel cell PDA concept Ballard 1 kw Fuel Cell Generator

6 Fuel Cell Applications - Stationary 4.5kW Vaillant PEMFC unit for residential applications 200kW UTC PC25 PAFC unit powering a NY Police Department station in Central Park 220 kw Siemens-Westinghouse SOFC-GT hybrid, Univ. California, US.

7 Fuel Cell Types e - H 2 H 2 H 2 O CO 2 CO Load H 3 O + H 3 O + Anode CO 3 2- O 2- Electrolyte Cathode e - O 2 H 2 O O 2 PEMFC C PAFC 200 C Phosphoric Acid Polymer Electrolyte Membrane MCFC 650 C Molten Carbonate SOFC C Solid Cxide

8 Introduction to Fuel Cells LOAD Membrane Electrode Assembly (MEA)/ Positive - Electrolyte - Negative (PEN) Fluid-Flow Plate (FFP) Flow Channel SOFC Anode Cathode PEMFC 20µ m Electrolyte H 2 H2 O 2 O 2 Membrane Anode Cathode 2H 2 2O 2-2HO + 2 4e - Anode ca. 1000µ m 15µ m Cathode 50µ m O + 2 4e - H 2 H 2 H 2 O 2 O2 O 2 2H 2 4H + 4e - Catalyst 10µ m 50µ m O 2 + 4e - 2HO 2 GDL 200µ m 2- Anode: 2H 2 + 2O - Cathode: O 2 + 4e H2O + 4e Anode: 2H 2 4H + 4e 2O 2- Cathode:4H + + O + 4e - 2 2HO 2 Page no./ref Solid Oxide Fuel Cell Imperial College London Proton Exchange Membrane Fuel Cell

9 Fuel Processing Liquid Fuel Evaporation Natural Gas Bio-fuel Increasing processing complexity (decreasing efficiency) C C Sulphur Removal Conversion to: H 2 and CO Shift Reaction CO selective Oxidation <40% H 2 CO 2, H 2 O etc. SOFC (Thermally integrated reformer) MCFC (Thermally integrated reformer) PAFC (CO<5%) PEMFC (CO<10ppm) C 650 C 200 C 80 C

10 Why is efficiency important? Reduce the impact of current fuel usage. Extend the lifetime of current fuel reserves. Learning applies to renewable fuel stocks.

11 Distributed Energy Generation Conventional Fuel Energy 100% Power station 62% losses Transmission 3% losses Delivered 35% Micro-CHP Fuel Fuel Cell Electrical Heat 35% 55% Energy 100% Fuel Cell 10% losses Delivered 90%

12 Industrial Co-Generation: SOFC-GT Hybrids Multi-MWe SOFC-GT Hybrid concepts % LHV electrical efficiency. Could enable CO 2 capture. Rolls-Royce, GE, Siemens Westinghouse, Korea Aerospace. B. Fredriksson Möller, J. Arriagada, M. Assadi and I. Potts, J Power Sources, 131 (2004) pp

13 Micro-CHP: Sub 10 kwe residential scale 90% efficient in CHP mode (35% electrical, 55% thermal). UK domestic energy requirement around 1-3 kwe with a thermal/electrical load of 4:1 to around 2:1 operating on NG. Developing world requirement kwe operating on LPG. 1.3M boilers replaced per annum in UK, market value around 900M p.a. SOFC best technical fit to achieve good efficiency on hydrocarbon fuels, but requires a robust and low cost fuel cell technology. Sulzer Hexis, CFCL, Plug Power, Versa Power, Ceres Power, Kyocera, Fuel Cell Energy, Vaillant, Baxi,...

14 Metal supported SOFCs operating at <600C Many SOFC developers are targeting an operating temperature of C. This allows metallic interconnects, but still requires a ceramic support giving issues with sealing, stability to oxidation and reduction, etc. Improved mechanical and thermal properties through the use of metal supports. Ease of manufacture of metal components reduces cost and improves quality. Enables use of compliant gasket sealing and metal-metal welding, avoiding use of glass ceramics. Improved durability. System temperatures <600C greatly reduce cost of balance of plant.

15 Materials Selection for third Generation (3G) SOFCs Ce 0.9 Gd 0.1 O 2-x electrolyte. 70 wt % La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ, 30 wt% Ce 0.8 Gd 0.2 O 2-x cathode, µm thick. Ti-Nb stabilised 17% Cr ferritic stainless steel (European designation: ) foil support, around 200 µm thick. 70 wt% NiO, 30 wt% Ce 0.9 Gd 0.1 O 2-x anode, µm thick stainless steel interconnect.

16 Metal supported SOFCs operating at <600C Metal supported SOFC produced by Ceres Power Dense CGO electrolyte Ni-CGO cermet anode LSCF-CGO composite cathode Ferritic stainless steel substrate Holes in active area of substrate

17 CO 2 savings from SOFC Micro-CHP compared to grid electricity Carbon dioxide emmissions per household (kg CO 2 pa) Ca SOFC SOFC Micro-CHP Electrical Generation Capacity (kwe) (kwe) From A D Hawkes, G Tiravanti, M A Leach, Imperial College London: assumes grid-average emissions rate of 0.43kg CO 2 /kwh and carbon emissions from burning natural gas to be 0.189kg CO 2 /kwh

18 Renewable Fuels Gasification of wood (typically 20% CO, 15% H 2, 5% CH 4, 15% CO 2, and 45% N 2 ). Anaerobic Digestion of waste (around 50% CH 4 and 50% CO 2 ). Bio-alcohols - reformed to syngas (H 2, CO, H 2 O, CO 2 ). Hydrogen generated by electrolysis using wind or PV generated electricity. Challenges remain those of tolerance to impurities, fuel cost and, for hydrogen in some applications, fuel storage.

19 Fuel Cell Research at Imperial College London Around 50 staff and research students are active in fuel cell research at Imperial College London. Two new Research Council programmes are: Supergen Fuel Cells. A 4 year 2.2M collaborative programme led by Imperial College, involving Rolls-Royce, Johnson- Matthey, Ceres Power, DSTL, and the Univ. s of Newcastle, Dundee, Nottingham, and St. Andrews. Fuel Cell Topic under the Future Sources of Energy theme of the UK Energy Research Centre.

20 Summary Fuel Cells are an enabling technology for the hydrogen economy. Fuel Cells also offer exciting opportunities to allow us to use existing fuel reserves significantly more efficiently, reducing CO 2 and other emissions. Learning from developments using conventional fuels is relevant to renewable fuel cells, whether these be based on bio-alcohols or renewable hydrogen. But challenges remain in demonstrating durable, cost effective technological solutions in the fuel cell sector