2. INTRODUCTION Fuel cells have been in production since the
1960s Fuel cells powered NASAs Apollo Space Craft Only emission is
water and electricity Slowly gaining popularity with auto
manufactures for alternate fuel vehicles. Apollo Space Craft
3. FUNDAMENTALS OF FUEL CELL OPERATION A fuel cell converts the
energy in a fuel into electricity. This is done using a chemical
reaction Fuel is usually hydrogen Some cells can use simple
hydrocarbons like methanol and natural gas
4. Each type of fuel cell has its owe unique operation. All
fuel cells have three general components Three Basic Components
Electrolyte Cathode Anode Source of fuel is the anode Oxygen is
typically the cathode The type of electrolyte define the type of
fuel cell Basic Fuel Cell Diagram
5. POLYMER-ELECTROLYTE MEMBRANE FUEL CELL (PEM) Drawn
significant attention in scientific community Quick start up time
Simplicity Flexible Most popular automobile fuel cell type
6. Four Main Components in PEM Fuel Cells Bipolar plate Gas
diffusion layer Catalyst layer Electrolyte membrane Electrolyte
membrane is unique because it blocks the flow of gas. Only allows
positively charged ions to flow. In the picture, note the positive
ions flowing to the cathode. PEM Fuel Cell Diagram
7. ADVANTAGES Low Operating Temperature Low operating
temperature means quick start up times This is the single most
significant advantage of the PEM fuel cell. Makes this fuel cell
popular with auto manufacturers. Auto makers require a low start up
time to accommodate the needs of their customers.
8. DISADVANTAGES Intolerant to CO in Fuel Concentrations of
less than 1 PPM are enough to damage catalyst Hydrogen fuel is
rarely pure When hydrogen is refined, small quantities of CO remain
Platinum catalyst is expensive
9. CURRENT USAGE OF PEM FUEL CELLS PEM fuel cells are used in
the automotive alternate fuel industry Toyota Mirai ----- 400 mile
range Hyundai Tuscan ----- 265 mile range Honda FXC Clarity -----
230 mile range Vehicle range is limited by hydrogen storage
capacity
10. IMAGES OF PEM FUEL CELL STACKS This is a low cost fuel cell
stack for a hobbyist or academic use. This is the fuel cell stack
in the Toyota Mirai.
11. SOLID OXIDE FUEL CELLS Popular fuel cell in todays market.
Certain features make it popular for stationary power supplies.
Primary advantages are fuel flexibility, high efficiency, and long
term stability.
12. Four Main Components in Solid Oxide Fuel Cells Anode
Cathode Interconnect Electrolyte Electrolyte is a solid ceramic
compound, hence the name Solid oxide fuel cell Manufactures use a
variety of materials for anode, cathode and interconnect layer.
These layers must withstand high temperatures Tubular Solid Oxide
Fuel Cell Diagram
13. Solid Oxide Fuel Cell Operation Different than PEM fuel
cell Electrolyte must reach 500 - 1000 C Oxygen is reduced to ions
in the cathode These ions flow through the electrolyte to the anode
gas Electrons are released which flow through a load and back to
the cathode Solid Oxide Fuel Cell Diagram
14. ADVANTAGES Solid Oxide Fuel Cells do not Require Pure
Hydrogen Cell can reform light hydrocarbons like natural gas
internally Many stationary solid oxide fuel cells use natural gas
for fuel High efficiency. Up to 80%
15. DISADVANTAGES High operating temperature Requires long
start up times Dictates material selection process All materials in
cell must withstand high temperatures
16. CURRENT USAGE OF SOLID OXIDE FUEL CELLS Solid oxide fuel
cells are popular for stationary power production Bloom Energy
manufactures stationary power supplies with solid oxide fuel cells
Current Boom power supplies are 200kW. Can use light liquid, or gas
hydrocarbons as fuel Implemented as power sources for several
fortune 500 companies.
17. This is a bank of Bloom Energy Servers Fuel cell
manufactured by Ceramic Fuel Cells Limited
18. ALKALINE FUEL CELLS Alkaline fuel cells have been in
production since the 1960s. Implemented by NASA for their Apollo
Space Craft This was convenient because fuel cells produce
electricity and water. Used in Space Shuttle program as well Not
popular in toadys fuel cell market Alkaline fuel cell used in NASAs
Space Shuttles
19. ALKALINE FUEL CELL OPERATION Alkaline fuel cell operation
is similar to solid oxide operation Oxygen reduction occurs in
cathode and ions flow to the anode fuel gas Electrolyte is a
liquid, unlike the PEM and solid oxide fuel cell This electrolyte
is sensitive to CO2 Must have a supply of pure oxygen Alkaline Fuel
Cell Diagram
20. ADVANTAGES Generally less expensive than PEM fuel cells. No
precious metals in catalyst Higher power density than PEM fuel
cells Produces .85 volts per cell.
21. DISADVANTAGES Requires a source of pure oxygen on cathode
side Major disadvantage Alternative to this is supplying air that
has been scrubbed of CO2
22. CONCLUSION The PEM fuel cell, solid oxide fuel cell, and
alkaline fuel cell have been researched significantly in the
scientific community There are several other fuel cell types in
production The PEM fuel cell and solid oxide fuel cell have are
included in my presentation because they are currently the most
popular fuel cell. A basic understanding of the alkaline fuel cell
is important because one of the first fuel cells developed.