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Xian Jiaotong University

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State Key Laboratory of Multiphase Flow1/13

Energy Conservation and

Environmental Protection

Fuel cells

Qincheng Bi

[email protected]

State Key Laboratory of Multiphase Flow in Power Engineering

Xi'an Jiaotong University

Xi'an 710049 China

2014.11.26


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Fuel Cells, Introduction

A fuel cell is basically a battery in which

the reactants are continually supplied to

the electrodes, and the products are

continually removed.Much more efficient (2-3 times) than heatengines at generating electricity

Most common type of fuel cells based onhydrogen (there are others)

What is a fuel cell and how does it work?

Scheme of direct energy conversion in an electrochemical cell

as compared to !conventional"thermal conversion
mailto:[email protected]:[email protected]

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Fuel Cells, History

invented in 1838.

first commercial use in NASA space

programs

used for primary and backup power

for commercial, industrial and reside

ntial buildings and in remote or inacc

essible areas.

To power fuel-cell vehicles, includingforklifts, automobiles, buses, boats,

motorcycles and submarines.


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Fuel Cells, History

Efficiency versus power for different fuel cell types c

ompared to other energy conversion technologies

Fuel cell technology

offers clean, ef#cient,

reliable power

generation to almost

any device requiring

electrical power. Fuel

cells are used in a wide

range of portable,stationary and transport

applications, from

battery chargers to

home heating and

power to cars. Arguably,

fuel cells represent the

most versatile energy

solution ever invented.

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Fuel Cells, Types

Design features in a fuel cell: The electrolyte substance. The electrolyte

substance usually defines thetype of fuel

cell.

The fuel that is used. The most commonfuel is hydrogen.

The anode catalyst breaks down the fuelinto electrons and ions. The anode

catalyst is usually made up of very fine

platinum powder.

The cathode catalyst turns the ions intothe waste chemicals like water or carbon

dioxide. The cathode catalyst is often

made up of nickel but it can also be a

nanomaterial-based catalyst.


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Fuel Cells, TypesFuel cells come in many varieties; however, they all work in the same

general manner. The main types of fuel cells are:

1. Proton exchange membrane fuel cells (PEMFCs)In the archetypical hydrogen$oxide proton exchange membrane fuel cell design,

a proton-conducting polymer membrane (the electrolyte) separates the anode and c

athodesides. This was called a "solid polymer electrolyte fuel cell" (SPEFC) in the e

arly 1970s, before the proton exchange mechanism was well-understood

2. Phosphoricacid fuel cell (PAFC)In these cells phosphoric acid is used as a non-conductive electrolyte to pass

positive hydrogen ions from the anode to the cathode. These cells commonly work

in temperatures of 150 to 200 degrees Celsius. This high temperature will cause

heat and energy loss if the heat is not removed and used properly. This heat can be

used to produce steam for air conditioning systems or any other thermal energy

consuming system.

3. Solid oxide fuel cells (SOFCs)SOFCs use a solid material as the electrolyte. Because SOFCs are made entire

ly of solid materials, they are not limited to the flat plane configuration of other typesof fuel cells and are often designed as rolled tubes. They require highoperating tem

peratures (800$1000.C) and can be run on a variety of fuels including natural gas.

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Fuel Cells, TypesFuel cells come in many varieties; however, they all work in the same

general manner. The main types of fuel cells are:

4. Hydrogen-OxygenFuel Cell (Bacon Cell)The Hydrogen-Oxygen Fuel Cell was designed by Bacon in the year 1959. It w

as used as a primary source of electrical energy in the Apollo space program. The

overall reaction involves the combination of hydrogen gas and oxygen gas to form

water. The cell runs continuously until the reactant's supply is exhausted. This type

of cell operates efficiently in the temperature range 343 K to 413 K and provides a p

otential of about 0.9 V.

5. Molten carbonate fuel cells (MCFCs)MCFCs require a high operating temperature, 650.C (1,200.F), similar

to SOFCs. Like SOFCs, MCFCs are capable of converting fossil fuel to a hydrogen-rich gas in the anode, eliminating the need to produce hydrogen externally. The refo

rming process creates CO2 emissions. MCFC-compatible fuels include natural gas,biogas and gas produced from coal.


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Fuel Cell Families

They are arranged according to the nature of electrolyte, acidic

or alkaline, and to their temperature of operation.

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Fuel Cell Types and Their Electrochemistry

AFC Alkaline fuel cell.

EC Electrocatalysis.

FC Fuel cell.

GDE Gas diffusion electrode.

GDL Gas diffusion layer.

HOR Hydrogen oxidation reaction.

HT-PEFC High temperature polymer electrolyte fuel cell.

MCFC Molten carbonate fuel cell.

ORR Oxygen reduction reaction.

PAFC Phosphoric acid fuel cell.

PEFC Polymer electrolyte fuel cell.

SOFC Solid oxide fuel cell.


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Comparison of Fuel Cell Technologies

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Fuel Cell, Applications

Automobiles

Buses

Forklifts

Motorcycles and bicycles

Airplanes

Boats

Submarines

Portable power systems

Main

Applications


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Fuel Cell, Applications

Providingpower for base stations or cell sites

Distributed generation

Emergency power systems

Uninterrupted power supply (UPS)

Base load power plants

Solar Hydrogen Fuel Cell Water Heating Hybrid vehicles

Notebook computers

Smartphones, laptops and tablets.

Small heating appliances

Food preservation,

Breathalyzers,

Carbon monoxide detector

Other applications

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What is a fuel cell?

Battery Combustionengine

Chemical

energy

Electrical

energyChemical

energy

Mechanica

l energy

Fuel cell

Chemical

energy

Electrical

energy

Limited energy

capacity

Output depends on input Output depends on input

more like


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Advantages and disadvantages

u High efficiency

Far more efficient than combustion

engines

Not limited by the Carnot efficiency

u Zero emission

no undesirable products such as

NOx and SOx

u No noise

No moving parts

u Scalable

from 1-W range (cell phone) to

megawatt range (power plant)

u Quick recharge

u High cost

Pt catalyst

u Unsatisfactory power density

u Fuel availabil ity and storage

H2: not widely available, low

volumetric energy density, not

easy to store

Gasoline, methanol: difficult to

use directly, require reforming

u Durability

u Susceptibility to environmental

poisons

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Improvement are required if fuel cells are to compete in portable

and automotive application.

Power density:

How much power it can produce per unit volume (volumetric power

density) or per unit mass (gravimetric power density) ?


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How does a fuel cell work?

Proton exchange membrane fuel cell

(PEMFC)

2 2 2H H e

+

+

Anode

reduction reaction

Cathode

oxidation reaction

2 2

12 2

2O H e H O

+

+ +

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Where does each process takes place?

u Reactant deliver flow field, gasdiffusion layer

u Electrochemical reaction catalyst layer

u Ionic conduction andelectro conduction

through electrolyte

and external circuit, gasdiffusion layer

u Product removal gas diffusion layer

and flow field


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Major fuel cell types and description

According to different electrolyte used:

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A good fuel cell or not?

Combined fuel cell i-V and power density

curves

How do you evaluate fuel cell performance?


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We want

Higher voltage at a certain current density

or

Higher current density at a certain voltage

better

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Schematic of fuel cell i-V

curve

Fuel cell performance

Real output voltage of fuel

cellThermodynamically

predicted fuel cell output

voltage, which is

determined by Gibbs free

energy difference between

product and reactant.

Activation losses due to

reaction kinetics.

Ohmic losses from ionic

and electronic conduction.

Concentration losses due to

mass transport.thermo act ohmic conc

V E =

1.23thermo

E V=

thermoE

act

ohmic

conc

V

for OHOH 2222

1+


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Stacks

u Connect single cells in series to achieve higher voltage output

u Connect single cells in parallel to achieve higher current output

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Fuel Cell systems could operate

on a variety of fuel types,

providevalue for military, industria

l, and consumer users in a wide

range of

portable power applications.

Toshiba methanol fuel cells Nectar

Minipak

Upp

Upp

Application-portable


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i5

SportWagen

HyMotion

A7

Fuel Cell

Vehicle(FCV) is a type

of vehicle which uses

a fuel cell to power its

on-board electric

motor. Fuel cells in

vehicles createelectricity to power

an electric motor,

generally

using oxygen from the

air and hydrogen. A fuel

cell vehicle that is

fueled with hydrogen

emits only water and

heat, but no tailpipe

pollutants, therefore it

Application- vehicle

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Application- power station

POSCO, Korea, 360 megawatt fuel

cell power station - Present largest

fuel cell power station in the world.Berlin ,250 kilowatt fuel cell power

station, PEMFC


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THE END

Thanks!

08 fuel cell

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