1. Viktória B. Kovács| Fuel cells| © 2015 BMEGEENAG51 | D218 | 2015-16-1 | 1 FUEL CELLS Viktória Barbara KOVÁCS

2. Viktória B. Kovács| Fuel cells| © 2015 BMEGEENAG51 | D218 | 2015-16-1 | 2 INTRODUCTION Fuel cell is a device which use hydrogen or hydrogen rich fuel and oxygen to produce electricity through electrochemical process. Byproducts: water and heat Present use: vehicles, energy supply of buildings, PC.

3. Viktória B. Kovács| Fuel cells| © 2015 BMEGEENAG51 | D218 | 2015-16-1 | 3 WHY FUEL CELLS? Decrease pollution Decrease fossil energy source dependence Slowing down global warming Prevent energy crisis

4. Viktória B. Kovács| Fuel cells| © 2015 BMEGEENAG51 | D218 | 2015-16-1 | 4 FUEL CELLS Advantages High and size independent efficiency (40..70%). The heat (byproduct) can be used in cogeneration. Low specific mass: 1 kg/kW. No moving parts → long lifetime, silent, reliable. Very low GHG emission. No toxic /harmful pollutants for health or for the environment In case of pure hydrogen operation only water and heat emission. Disadvantages New technology → averseness in the beginning. High costs in the beginning of market introduction → high risk Missing or undeveloped hydrogen infrastructure.

5. Viktória B. Kovács| Fuel cells| © 2015 BMEGEENAG51 | D218 | 2015-16-1 | 5 PRINCIPLE OF OPERATION The fuel cell produces electric power from hydrogen and oxygen through electrochemical process. An ordinary fuel cell consists of two fine and porous electrode (anode and cathode) and the electrolyte between the electrodes. The hydrogen or hydrogen rich fuel dissociates to e- and p+ on the anode by the help of the catalyst. The oxygen with the electrons and protons (or other ions) form water (or something else) on the cathode. The electrons are not allowed to penetrate through the membrane, they are forced to the cathode through the current circuit. The drift of the electrons produces electrical direct current. anode cathode

6. Viktória B. Kovács| Fuel cells| © 2015 BMEGEENAG51 | D218 | 2015-16-1 | 6 PRINCIPLE OF OPERATION oxygen protons electrons membrane DC e e water heat H 2 2H + + 2e - 1/2O 2 + 2e - 1/2O 2 2 - ~1,23 Volt e e e e anodecathode

7. Viktória B. Kovács| Fuel cells| © 2015 BMEGEENAG51 | D218 | 2015-16-1 | 7 FUEL CELL SYSTEM 1. Fuel reforming unit (cleaner) 2. Energy conversation unit (fuel cell) 3. Transformer (DC/AC converter) 4. Heat recovery (in case of high temperature) 3. INVERTER H 2 -rich gas fuel 4. Heat recovery fuel reforming 2. Fuel CELL 1. thermal reformer oxygen (air) ACAC DC water cogeneration heat

8. Viktória B. Kovács| Fuel cells| © 2015 BMEGEENAG51 | D218 | 2015-16-1 | 8 1. FUEL REFORMING UNIT Fuel reforming and cleaning. If the fuel is hydrogen only cleaning is needed. Liquid fuel (methanol, ethanol, gasoline...) are changed by thermal reforming to gaseous hydrocarbons.

9. Viktória B. Kovács| Fuel cells| © 2015 BMEGEENAG51 | D218 | 2015-16-1 | 9 2. ENERGY CONVERSATION UNIT (FUEL CELL) Chemical energy → electrical power. DC is produced through chemical reaction.

10. Viktória B. Kovács| Fuel cells| © 2015 BMEGEENAG51 | D218 | 2015-16-1 | 10 3. TRANSFORMER AND REGULATOR Keep regulated and constant electrical connection between the fuel cell and network (consumer). Transform DC to AC. Regulates the current intensity, potential, frequency, and other parameters according to the demands.

11. Viktória B. Kovács| Fuel cells| © 2015 BMEGEENAG51 | D218 | 2015-16-1 | 11 4. HEAT RECOVERY UNIT Not always added, because heat is not the main product. In case of high temperature: – steam production for combined power generation – direct use in steam turbine. The overall efficiency is higher with heat recovery.

12. Viktória B. Kovács| Fuel cells| © 2015 BMEGEENAG51 | D218 | 2015-16-1 | 12 CLASSIFICATION OF FUEL CELLS By Fuel Direct: hydrogen to anode Indirect: Hydrogen rich fuel reformatted to anode Regenerative: products are decomposed and reused By Electrolyte polymer electrolyte membrane (PEMFC) ~80 °C phosphoric acid (PAFC) ~200 °C alkaline (AFC) 80..100 °C molten carbonate (MCFC) ~650 °C solid oxide (SOFC) – tubular (TSOFC) 800 °C – intermediate temperature (ITSOFC) 1000 °C

13. Viktória B. Kovács| Fuel cells| © 2015 BMEGEENAG51 | D218 | 2015-16-1 | 13 POLYMER ELECTROLYTE MEMBRANE- PEMFC Other name: SPEFC (Solid Polymer Electrolyte Fuel Cells) Electrolyte: proton exchange membrane Low temperature (85..105 °C) Nafion® membrane (DuPont development) which is bed in poli-tetra-fluorethilen (PTFE, Teflon) based composition Anode: H 2 → 2H + + 2e - Cathode: 1/2O 2 + 2H + + 2e - → H 2 O High power density (Power/mass) Fast stand-up Mainly in vehicles disadvantage: low CO tolerance (Pt poison)

14. Viktória B. Kovács| Fuel cells| © 2015 BMEGEENAG51 | D218 | 2015-16-1 | 14 POLYMER ELECTROLYTE MEMBRANE - PEMFC Fuel cell stack explained.mp4: https://www.youtube.com/watch?v=w5E_MAZdO-k anode cathode

15. Viktória B. Kovács| Fuel cells| © 2015 BMEGEENAG51 | D218 | 2015-16-1 | 15 PHOSPHORIC ACID ELECTROLYTE - PAFC 100% concentration of H 3 PO 4 in SiC matrix with Pt catalyst Anode: H 2 → 2H + + 2e - Cathode: 1/2O 2 + 2H + + 2e - → H 2 O High temperature is needed, because H 3 PO 4 is bad conductor CO<3..5 vol% or Pt is poisoned

16. Viktória B. Kovács| Fuel cells| © 2015 BMEGEENAG51 | D218 | 2015-16-1 | 16 ALKALINE ELECTROLYTE - AFC high concentration KOH (35..85 m%) in asbestos matrix Anode: H 2 + 2OH- → 2H 2 O + e- Cathode: 1/2O 2 + H 2 O + 2e- → 2OH- CO 2 is poison: CO 2 + KOH → K 2 CO 3 because the electrolyte changes High efficiency (~60%) Disadvantage: expensive

17. Viktória B. Kovács| Fuel cells| © 2015 BMEGEENAG51 | D218 | 2015-16-1 | 17 MOLTEN CARBONATE ELECTROLYTE - MCFC Mixture of alkali carbonates LiAlO2 in ceramic matrix, High temperature (600..800 °C) Anode: H 2 + CO 3 2- → H 2 O + CO 2 + 2e - CO + CO 3 2- → 2CO 2 + 2e - Cathode: 1/2O 2 + CO 2 + 2e- → CO 3 2- Ni (anode) and NiO (cathode) High efficiency (70..80% !!!!!) fuel: H2, CO, NG, propane and even diesel oil

18. Viktória B. Kovács| Fuel cells| © 2015 BMEGEENAG51 | D218 | 2015-16-1 | 18 SOLID OXIDE ELECTROLYTE - SOFC solid ceramic: ZrO2 stabilized by Y 2 O 3 Anode: H 2 + O 2 - → H 2 O + 2e - CO + O 2 - → CO 2 + 2e - CH 4 + 4O 2 - → 2H 2 O + CO 2 + 8e - Cathode: 1/2O 2 + 2e- → O 2 - Co-ZrO 2 or Ni-ZrO 2 (anode) and LaMnO 3 mixed with Strontium (cathode) two types: – tubular (1 m tube bundles) – laminated plates high power: (electricity supply) SOFC Brennstoffzelle.mp4: https://www.youtube.com/watch?v=Itz2hJPP9l4

19. Viktória B. Kovács| Fuel cells| © 2015 BMEGEENAG51 | D218 | 2015-16-1 | 19 COMPARISON - REACTION I. Type of fuel cell NameElectrolyte t operation (°C) Fuel Oxidizer Anode and cathode reaction alkalineAFC 30% KOH, Liquid or gel 60-90 - pure H 2 - O 2 A: H 2 +2OH -  2H 2 O +2e - C: 1/2O 2 +H 2 O+2e -  2OH - solid polymer SPFC, PEMFC Proton exchange membrane 70-90 - pure H2 - O2, air A: H 2  2H + +2e - C: 1/2O 2 +2H + +2e -  2H 2 O direct methanol DMFC Proton exchange membrane 60-120 - methanol - O2, air A: CH 3 OH + H 2 O  CO 2+ +6H + +6e - C: 3/2O 2 +6H + +6e -  3H 2 O phosphoric acid PAFC undiluted phosphoric acid ~220 - pure H2 - O2, air A: H 2  2H + +2e - C: 1/2O 2 +2H + +2e -  2H 2 O molten carbonate MCFC lithium- carbonate, potassium- carbonate ~650 - H 2, NG, biogas, coal-gas - air, O2 A: H 2 +CO 3 2-  H 2 O +CO 2 +2e - C: 1/2O 2 +CO 2 +2e -  CO 3 2- Solid oxideSOFC yttrium-Zircon cheramic oxid ~1000 - H 2, NG, biogas, coal-gas - air, O2 A: H 2 +O 2-  H 2 O +2e - C: 1/2O 2 +2e -  O 2-

20. Viktória B. Kovács| Fuel cells| © 2015 BMEGEENAG51 | D218 | 2015-16-1 | 20 COMPARISON - REACTION II. Not used fuel fuel O 2 / air not used O 2 / air SOFC MCFC PAFC DMFC PEMFC AFC H 2 /CO H2H2 CH 3 OH H2H2 H2H2 O2O2 O2O2 O2O2 O2O2 O2O2 O2O2 H+H+ H+H+ H+H+ OH - CO 3 2- O 2- solid oxide molten carbonate phosphoric acid direct methanol polymer electrolyte alkaline high temperature low temperatire >800°C 650°C 200°C 60 – 120°C < 90°C < 80°C

21. Viktória B. Kovács| Fuel cells| © 2015 BMEGEENAG51 | D218 | 2015-16-1 | 21 COMPARISON - ENERGY Type of fuel cell Operation temp., °C Pressure, kPa Current density, A/cm 2 Potential, V alkaline701 (101)0,20,20,80,8 Phosphoric acid1901 (101)0,3240,62 Phosphoric acid2058 (808)0,2160,73 molten carbonate6501 (101)0,160,78 solid oxide10001 (101)0,20,20,66

22. Viktória B. Kovács| Fuel cells| © 2015 BMEGEENAG51 | D218 | 2015-16-1 | 22 USE, POWER, EFFICIENCY Type of fuel cellUsePower Efficiency actual (theoretical) AFC (alkaline) vehicles Space program Military purposes Energy storage low power 5..150 kW 62% (70%) PEMFC (polymer electrolyte) low power 5..250 kW 50% (68%) DMFC (direct methanol) low power 5 kW 26% (30%) PAFC (phosphoric acid) Combined cycle power plant Low - medium power 50 kW..11 MW 60% (65%) MCFC (molten carbonate) Combined cycle power plant And traffic (railway, ship, …) low power 100 kW..2 MW 62% (65%) SOFC (solid oxide) low power 100..250 kW 62% (65%) GC: η e => kW – 40%, >MW 45-46% IC: η e => 50% CCGT: η e => 40% ST + 20% GT

23. Viktória B. Kovács| Fuel cells| © 2015 BMEGEENAG51 | D218 | 2015-16-1 | 23 EFFICIENCY OF A FUEL CELL H 2 52,5 kW (100%) Net Power 25,1 kW (47,8%) System loss 4,5 kW (8,6%) H 2 loss 0,5 kW (1%) Gross power 29,6 kW (56,4%) Heat loss 22,4 kW (42,6%) 25 kW PEMFC efficiencies in case of DC production

24. Viktória B. Kovács| Fuel cells| © 2015 BMEGEENAG51 | D218 | 2015-16-1 | 24 USE AND POWER RANGES MethanolAlkalineMolten carbonate Phosphoric acid Solid oxide Polymer electrolyte / Proton exchange Portable devices, high energy density Mobile, home use zero emission Industrial use, higher efficiency silent, environmental friendly operation

25. Viktória B. Kovács| Fuel cells| © 2015 BMEGEENAG51 | D218 | 2015-16-1 | 25 USE Energy storage Road transport Small scale power plants Analytics

26. Viktória B. Kovács| Fuel cells| © 2015 BMEGEENAG51 | D218 | 2015-16-1 | 26 PEMFC IN VEHICLES

27. Viktória B. Kovács| Fuel cells| © 2015 BMEGEENAG51 | D218 | 2015-16-1 | 27 QUESTIONS What is the working principle of fuel cells (PEMFC)? What are the advantages and disadvantages of fuel cells? Describe fuel cell system for power generation! What type of fuel cells do you know? Describe one of them in detail: type of electrolyte, fuel, operating temperature, efficiency!

28. Viktória B. Kovács| Fuel cells| © 2015 BMEGEENAG51 | D218 | 2015-16-1 | 28 THANK YOU FOR YOUR ATTENTION! Viktória Barbara KOVÁCS Build. D room 207B 06 1 463 2592 kovacs@energia.bme.hu