FUEL CELL TECHNOLOGYPaul Nikstad

INTRODUCTION

Fuel cells have been in production since the 1960’s

Fuel cells powered NASA’s Apollo Space Craft

Only emission is water and electricity

Slowly gaining popularity with auto manufactures for alternate fuel vehicles.

Apollo Space Craft

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

Each type of fuel cell has it’s 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 cellBasic Fuel Cell Diagram

POLYMER-ELECTROLYTE MEMBRANE FUEL CELL

(PEM)

Drawn significant attention in scientific community

Quick start up time

Simplicity

Flexible

Most popular automobile fuel cell type

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

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.

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

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

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.

SOLID OXIDE FUEL CELLS

Popular fuel cell in today’s market.

Certain features make it popular for stationary power supplies.

Primary advantages are fuel flexibility, high efficiency, and long

term stability.

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

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

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%

DISADVANTAGES

High operating temperature

Requires long start up times

Dictates material selection process

All materials in cell must withstand high temperatures

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.

This is a bank of Bloom Energy Servers

Fuel cell manufactured by Ceramic Fuel Cells Limited

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 toady’s fuel cell market

Alkaline fuel cell used in

NASA’s Space Shuttles

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

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.

DISADVANTAGES

Requires a source of pure oxygen on cathode side

Major disadvantage

Alternative to this is supplying air that has been “scrubbed” of CO2

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.