Characteristics and Types of Fuels

Fuels
Fuel Cells
&
By
PRANALI PATIL

2
TOPICS TO BE COVERED
• FUEL
• COMBUSTION OF FUEL
• CLASSIFICATION OF FUEL
• CALORIFIC VALUE
• CHARACTERISTICS OF GOOD FUEL
• Bomb Calorimeter
• Boys Calorimeter
• Numerical Problems on Fuel

Fuel O2
Combustion
Products Heat
e.g.: Coke on combustion gives carbon dioxide
Coal → Coke + Coal gas
C (coke) + O2 → CO2
 Ordinary Combustion process of fuel is

FUELS
Fuel is a combustible substance which
during combustion gives large amount of
heat.
e.g.- Wood, charcoal, coal, kerosene,
petrol, diesel, producer gas, water gas,
natural gas, etc.,
Definition
Chemical fuel is a combustible carbonaceous material
which on proper burning in air gives large amount of
heat that can be used economically for domestic and
industrial purposes. OR

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CLASSIFICATION OF FUEL
FUEL
OCCURENCE
PHYSICAL
STATE
On the basis of Two ways

6
On the basis of Occurrence
FUEL
PRIMARY OR
NATURAL FUEL
SECONDARY OR
ARTIFICIAL FUEL
On the basis of occurrence

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CLASSIFICATION OF FUEL
Fuels are classified as
• Primary fuels – Fuels which occur naturally
such as coal, crude petroleum and natural
gas. Coal and crude petroleum, formed from
organic matter many millions of years ago,
are referred to as fossil fuels. e.g. coal,
crude petroleum, natural gas etc.
• Secondary fuels – Fuels which are derived
from naturally occurring ones by a chemical
treatment process.
• e.g. coke, gasoline, coal gas, producer
gas, water gas, kerosene, etc.

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On basis of Physical State
FUEL
SOLID LIQUID GAS
On basis of Physical State
Fuel Fuel Fuel
e.g. coal, coke e.g. Petrol, Kerosene e.g. Natural gas

Table-1. Classification of Fuels
Physical state Primary fuel Secondary fuel
Solid Wood, Peat, Charcoal, Coke
Coal, Lignite
Liquid Crude petroleum Petrol, Kerosene,
Diesel, Synthetic
petrol
Gas Natural gas Producer gas,
Water gas, Coal gas,
Biogas, LPG
9

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FUEL
Primary
Fuels
Solid
eg. Wood,peat
Liquid
eg. Crude
peteroleum
(crude oil)
Gas
Eg.Natural gas
Secondary
fuels
Solid
eg.Coke,
Charcoal
Liquid
Eg. Petrol,
Diesel, Kerosene
Gas
Eg.coal gas
,water gas, LPG,
Biogas
On basis of Physical State On basis of Physical State
On basis of Occurrence

Calorific value: It is defined as the total quantity of
heat liberated when a unit mass of a fuel is burnt
completely. Units of Calorific value:
System Solid/Liquid
Fuels
Gaseous
Fuels
CGS
MKS
cal/gm
kcal/kg
cal/cm3
kcal/m3
The quantity of heat can be measured in the following units:
(i) Calorie: It is defined as the amount of heat required to raise
the temperature of 1gm of water by 1oC
1 calorie = 4.184 Joules

Types of calorific Value :
1) Higher or Gross Calorific Value
(HCV Or GCV):
2) Lower or net calorific value:
(LCV OR NCV ):

Calorific Value: The total amount of heat produced by
complete combustion of a unit mass or unit volume
of the given fuel is known as calorific value of that fuel.
There are two types of calorific values:
•Higher or Gross calorific value: (HCV OR GCV):
The amount of heat produced by complete
combustion of a unit mass or unit volume of the given
fuel, in air or oxygen and allowing the products of
combustion to cool down to room temperature is
known as higher or gross calorific value.
•Lower or net calorific value: (LCV OR NCV ):
The amount of heat produced by complete combustion
of a unit mass or unit volume of the given fuel and
allowing the gaseous products to escape (evolve) is
known as net or lower calorific value.
How to remember definitions?

Why HCV is high?
As the products of combustion are
cooled down to room temperature, the
steam gets condensed into water and
latent heat is evolved. Thus in the
determination of gross calorific value,
the latent heat also gets included in
the measured heat. Therefore, gross
calorific value is also called the higher
calorific value.

Why LCV is low?
In LCV, the products of combustion are allowed to
escape.
The water vapour do not condense and escape
with hot combustion gases. Hence, lesser amount
than gross calorific value is available. It is also known
as lower calorific value (LCV).
LCV=HCV-Latent heat of water vapours formed
Since 1 part by weight of hydrogen gives nine parts
by weight of water i.e.
O
H
O
H
2
2
2
1
2



Calculation of NCV Or LCV :
If H = Percentage of hydrogen in fuel, then
Hydrogen in the fuel reacts with oxygen to give water
H2 + 1/2 O2 → H2O
2H = 1/2O2 = H2O
2parts = 16parts = 18parts
1parts = 8parts = 9parts
• Water formed by combustion of 1g of fuel = 18 x H
2 100
= 0.09H g
• Latent heat of water formed = 0.09H × 587 cal/g
• NCV = GCV – Latent heat of water formed
= GCV – 0.09H × 587 cal/g

Therefore,
LCV=HCV- [9 x Wt.of Hydrogen x Latent Heat of steam]
LCV = HCV- [9 x Wt. of H x 587]
LCV = HCV- [0.09 x % of H x 587]
Determination of Calorific value
1. Determination of calorific value of solid and non
volatile liquid fuels: It is determined by bomb
calorimeter.
2. Determination of calorific value of gaseous and
volatile liquid fuels: It is determined by Boy’s
calorimeter.

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CHARACTERISTICS OF GOOD FUEL
1. CALORIFIC VALUE:
A good fuel should have high calorific
value i.e. it should produce large
amount of heat on burning.
2.CHEAP: A good fuel should be cheap and
readily available.

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3. IGNITION TEMPERATURE:
Ignition temperature is the lowest
temperature at which fuel starts to burn
smoothly.
If ignition temp. is low, the fuel catches fire
easily. Low ignition temperature is dangerous
for storage and transportation of fuel.
If ignition temp. is high, it causes difficulty in
burning.
So, a good fuel should have moderate ignition
temperature.

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4. MOISTURE CONTENT:
A good fuel should have low moisture content
because it reduces the calorific value.
5. MODERATE RATE OF COMBUSTION:
The temperature of combustion of fuel
depends upon the rate of combustion .
If the rate of combustion is low ,then
required high temperature may not be
reached soon.
On the other hand ,too high combustion
rate causes high temperature very quickly.

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6. NON-COMBUSTIBLE MATTER CONTENT :
A good fuel should have low contents of non-
combustible material because it is left in
form of ash which decreases the calorific
value of fuel.A good fuel should have low ash
content because it reduces the calorific
value.
7.CONTROLLABLE COMBUSTION:
Combustion of fuel should be easy to start or stop
when required. Combustion of fuel should be
non-spontaneous otherwise it can cause fire hazards

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8. Product of Combustion : MINIMUM
SMOKE AND NON-POISONOUS GASES
On burning, Fuel should not give out
objectionable and poisonous gases. In
other words, gaseous products should
not pollute the atmosphere. Gases like
CO,SO2,H2S etc. are some of harmful
gases.

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9.EASY TRANSPORTATION AND STORAGE :
A good fuel should be easy to handle and
transport at low cost , requires less space, no
risk in storage
10.UNIFORM SIZE :
For solid fuels the size should be uniform so
that rate of combustion can be controlled .

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Characteristics/ Criteria/ Conditions /
Properties of a good fuel MIMP SU

Characteristics/ Criteria/ Conditions /
Properties of a good fuel MIMP SU
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Let us discuss few multiple choice
questions
Que1.Agood fuel possess:
a. High ignition temperature
b. Moderate ignition temperature
c. High calorific value
d. Both (b) and (c)
Ans. (d)

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Que2.An example of primary fuel is :
a.charcoal
b.Coke
c.natural gas
d.petrol
Ans. (C)

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Que3.The minimum temperature at which
substance ignites and burns without
further addition of heat from outside is
called:
a. ignition temperature
b.flash point
c.transition temperature
d.all the above
Ans. (a)

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Que4.In a good fuel percentage of carbon
is:
a. low
b.high
c.moderate
d.zero
Ans. (b)

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Que5.Combustion of fuel involves chemical
reaction between fuel and
a.Hydrogen
b.Nitrogen
c.Oxygen
d.Chlorine
Ans. (c)

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Que6. The reaction in which heat is
absorbed is called
a. Exothermic
b.Endothermic
c.Exegonic
d.none of these
Ans. (b)

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Que7.Fuel can be defined as a substance
which produces heat by
a. combustion
b.Reduction
c. None of these
d.All of above
Ans. (a)

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Que8.The combustion reaction
C+O2 → CO2
is
a. Exothermic
b.Endothermic
c.Autocatalytic
d.none of these
Ans. (a)

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Que9.A good fuel should have following
characteristics:
a.Moderate ignition temperature
b. High calorific value
c.Low moisture content
d. all of these
Ans. (d)

Types of Fuels:
Solid Fuel Liquid Fuel Gaseous Fuel
FUEL
Properties of Solid, Liquid & Gaseous Fuel:
Comparison of Solid, Liquid & Gaseous Fuel:
OR

Sr.
No.
Property Solid
Fuel
Liquid
Fuel
Gaseous
Fuel
1 Calorific Value Lowest Higher Highest
2 Relative cost Cheaper Costly More costly
than other two
3 Ignition Temp. /
Point
Higher Low Lowest
4 Efficiency Poor Good Best
5 Specific gravity Higher Medium Lowest
6 Space for storage Large 50% less than
solid fuel
Very high
space
7 Care in storage and
transport
Less care
required
Care is
necessary
Great care
required
8 Mode of supply Cannot be
piped
Can be piped Can be piped
9 Air required for
combustion
Large and
excess of air
Less excess of
air
Slightly excess
of air
10 Use in IC Engine Cannot be
used
Already in use Can be used

Principle
•A known mass of the fuel sample is burnt
completely in
excess of oxygen.
•The liberated heat is absorbed by water and
calorimeter.
•The heat lost by burning fuel is the heat
gained by water
and calorimeter.
•The calorific value of the fuel is calculated
from the
measured data.

Use: To determine the calorific value of solid and non-volatile liquid
fuel.
Principle: A known mass of a solid or non-volatile liquid fuel is burnt
completely and the total heat produced is absorbed by water &
calorimeter which is then measured accurately to calculate calorific
value.
Construction:
•consists of a strong stainless steel container known as bomb.
•The electrodes are attached to the ring at the bottom on which the crucible is
placed.
•closed with lid fitted with screws. The lid is provided with two stainless steel
electrodes and oxygen inlet valve
•The bomb is placed in a copper calorimeter filled with water.
•The copper calorimeter is provided with stirrer and Beckman’s thermometer.
•To prevent the loss of heat, the calorimeter is insulated by air and water jacket.

•About 1 gm of accurately weighed fuel (X) is placed in a crucible.
•The bomb is closed and oxygen is supplied through oxygen inlet valve at 25 atm
pressure.
•The bomb is then placed in copper calorimeter containing a known mass of water
say ‘W’
•The initial temperature of water (t1) is noted.
•The electrodes are adjusted in such a way that spark is produced by fuse wires, so
that fuel starts burning.
•The heat produced during combustion of fuel will be absorbed in water.
The temperature of water is then recorded at regular intervals until a constant
temperature is obtained. Then the final temperature of water (t2) is recorded
Working:

Corrections: To obtain the correct value of calorific value
•Fuse wire correction (FC): H. C. V. usually consists of heat liberated
from the fuse wires during ignition of the fuel. Therefore, it should be
subtracted from the H. C. V.
•Acid correction (AC): S and N in fuel on oxidation are converted
into H2SO4 and HNO3 respectively. These reactions are exothermic.
Therefore, this heat should also be subtracted from H. C. V.
•Cooling correction (CC): After complete combustion of fuel, water
form calorimeter is allowed to cool to room temperature and the rate
of cooling per minute is determined. It is added in H. C. V.
Thus, Gross or Higher Calorific Value is calculated by using the
corrected formula as given below:

Use: to determine the calorific value of gaseous fuel and volatile liquid fuel.
Principle: A known volume of the given fuel sample at known pressure is allowed
to burn at some definite rate. The heat produced is absorbed by the water circulated
at constant rate. Then from the volume of fuel burnt, quantity of water circulated
and rise in temperature, the calorific value of the given fuel is calculated.
Construction:
•Boy’s calorimeter consists of a burner connected to gas cylinder through pressure
meter.
•The burner is covered with combustion chamber.
•The combustion chamber is provided with copper tubing inside and outside.
•Water is passed through copper tubing at a constant rate.
•Water enters from the top of outer coil, moves to the bottom and then flows in
upward direction through inner coils. Finally, it is collected in a measuring cylinder.
•T1 and T2 are thermometer readings of incoming and outgoing water respectively.
•The whole assembly is covered with an insulated chamber to avoid the heat loss
due to radiation.
BOY’S CALORIMETER:

Working: Water is circulated at a constant rate through copper tubings and the fuel is burnt
at a constant rate. The heat produced during combustion of fuel is absorbed by the
circulating water. When constant (or steady) temperature is obtained, certain observations
are taken as below;
Calculations: Suppose,

By using this equation, we can determine calorific value of gaseous fuel.

What is a fuel cell?
Classification of Fuel cells
Importance of Fuel cells

Fuel cells are electrochemical
cells consisting of two electrodes and an
electrolyte which convert the chemical
energy of chemical reaction between fuel
and oxidant directly into electrical energy.
Fuel
cells

 Ordinary Combustion process of fuel is
Fuel Oxygen
Combustion
Products
Heat

 The process of fuel cell is
Fuel Oxygen
Oxidation
Products
Electricity

Chemical
Energy
Heat
Mechanical
Energy
Electrical
Energy

• Fuel cell consists of electrodes, electrolyte & catalyst to
facilitate the electrochemical redox reaction.
• The basic arrangement in a fuel cell can be represented as
follows:
Fuel Electrode Electrolyte Electrode Oxidant

Fuel cell consist of
Anode
•A layer of anodic catalyst.
Electrolyte
Cathode
•A layer of cathodic catalyst.

• Materials which have high electron conductivity &
zero proton conductivity in the form of porous
catalyst (porous catalyst or carbon).
Anode & Cathode
• Platinum
Catalyst
• High proton conductivity & zero electron
conductivity.
Electrolyte
Fuel cell consist of

 Fuel Cell System:
1. The fuel (direct H2 or reformed H2) undergoes oxidation at
anode and releases electrons.
2. These electrons flow through the external circuit to the
cathode.
3. At cathode, oxidant (O2 from air) gets reduced.
4. The electrons produce electricity while passing through the
external circuit. Electricity is generated continuously as long as
fuel and the oxidant are continuously and separately supplied
to the electrodes of the cell from reservoirs outside the
electrochemical cell.

 The Fuel cell can be represented as:
• 2H2 → 4H+ + 4e-
At
anode
• O2 + 4H+ + 4e- → 2H2O
At
Cathode
• 2H2 + O2 → 2H2O
Overall
Reaction
 Large number of these cells are stacked together in series to
make a battery called as fuel cell battery or fuel battery.

Fuel cells operation
• Example: PEMFC
• The hydrogen atom’s electron and proton are separated at the anode.
• Only the protons can go through the membrane (thus, the name proton
exchange membrane fuel cell).
Hydrogen
Oxygen
Water
2 2 2
H H e
 
 
Heat
2 2
1/ 2 2 2 1
O H e H O
 
  
Membrane
(Nafion)
Catalyst (Pt)
Anode (-)
Catalyst (Pt)
Cathode (+)
dc current
2 2 2
2 2 ( 1.23 )
r
O H H O E V
  

Hydrogen
Oxygen
Electrical power production by fuel cell
Rotating shaft connected to generator for electricity production

Phosphoric Acid
(PAFC)
Alkaline
(AFC)
Polymer
Electrolyte
Membrane
(PEMFC)
Direct Methanol
(DMFC)
Solid Oxide
(SOFC)
Molten Carbonate
(MCFC)
Types of Fuel
Cells
Polymer Electrolyte
Membrane
(PEMFC)
Direct Methanol
(DMFC)
Solid Oxide
(SOFC)
63

3. Types of fuel cells
There are diffrent types of fuel cells, differentiated by the type
of electrolyte separating the hydrogen from the oxygen.The
types of fuel cells are:
• Alkaline fuel cells (AFC)
• Direct methanol fuel cells (DMFC)
• Molten carbonate fuel cell (MCFC)
• Phosphoric acid fuel cells (PAFC)
• Polymer electrolyte membrane fuel cells (PEMFC)
• Solid oxide fuel cells (SOFC)

Types of Fuel Cells
Fuel Cell Operating Conditions
Alkaline FC (AFC) Operates at room temp. to 80 0C
Apollo fuel cell
Proton Exchange
Membrane FC (PEMFC)
Operates best at 60-90 0C
Hydrogen fuel
Originally developed by GE for space
Phosphoric Acid FC (PAFC) Operates best at ~200 0C
Hydrogen fuel
Stationary energy storage device
Molten Carbonate FC (MCFC) Operates best at 550 0C
Nickel catalysts, ceramic separator membrane
Solid Oxide FC (SOFC) Operates at 900 0C
Conducting ceramic oxide electrodes
Direct Methanol Fuel Cell
(DMFC)
Operates best at 60-90 0C
Methanol Fuel
For portable electronic devices

Classification of Fuel cells:
These are classified into three types as
follows.
1] Low temp fuel cells: Which operates at
the temp range about 75 0C and contains
water base electrolytes.
2] Moderate temp fuel cells: Which
operates at the temp range about 600 0C
and contains salt electrolyte.
3) High temp fuel cells: Which operates at
the temp range about 1000 0C and contains
ceramics as electrolyte.

• Comparison of the most common technologies
• All fuel cells occupy a lot of space. Much more than any of the other types of
microsources
PEMFC DMFC AFC PAFC MCFC SOFC
Fuel H2 CH3OH H2 H2
H2, CO, CH4,
hydrocarbons
H2, CO, CH4,
hydrocarbons
Electrolyte
Solid polymer
(usually Nafion)
Solid polymer
(usually Nafion)
Potasium
hydroxide
(KOH)
Phosporic
acid (H3PO4
solution)
Lithium and
potassium
carbonate
Solid oxide
(yttria,
zirconia)
Charge carried in
electrolyte
H+ H+ OH- H+ O2-
Operational
temperature (oC) 50 – 100 50 - 90 60 - 120 175 – 200 650 1000
Efficiency (%) 35 – 60 < 50 35 – 55 35 – 45 45 – 55 50 – 60
Unit Size (KW) 0.1 – 500 << 1 < 5 5 – 2000 800 – 2000 > 2.5
Installed Cost ($/kW) 4000 > 5000 < 1000* 3000 – 3500 800 – 2000 1300 - 2000
Fuel cell technologies
2-
3
CO
* Without purifier

• Every fuel cell has two electrodes, one positive and one
negative, called, respectively, the cathode and anode. The
reactions that produce electricity take place at the
electrodes
• In all types of fuel cell, hydrogen is used as fuel and can be
obtained from any source of hydrocarbon.
• The fuel cell transform hydrogen and oxygen into electric
power, emitting water as their only waste product.
What is fuel cell?
A Fuel cell is a electrochemical device that converts chemical energy
into electrical energy
1. Introduction

• Every fuel cell also has an electrolyte, which carries
electrically charged particles from one electrode to the other,
and a catalyst, which speeds the reactions at the electrodes.
• A single fuel cell generates a tiny amount of direct current
(DC) electricity.
• A converter is used to produce AC current
• In practice, many fuel cells are usually assembled into a stack.
Cell or stack, the principles are the same.
• In 1932, Francis Bacon developed the first successful FC. He
used hydrogen, oxygen, an alkaline electrolyte, and nickel
electrodes.

(+) (-)
Anode Cathode
Electrolyte
A fuel cell consists of two
electrodes namely an anode
and a cathode and sandwiched
around an electrolyte.
An electrolyte is a substance,
solid or liquid, capable of
conducting oving ions from one
electrode to other.
2. A fuel cell configuration

Galvanic cell (battery)
Hydrogen fuel cell
Open system
Anode and cathode are gases in
contact with a platinum catalyst.
Reactants are externally supplied,
no recharging required.
 Closed system
Anode and cathode are metals.
Reactants are internally consumed,
need periodic recharging.
Fuel Cell Vs. Battery
Basic operating principles of both are very similar, but there are several
intrinsic differences.

Principle:
The fuel is oxidized on
the anode and oxidant reduced
on the cathode. One species of
ions are transported from one
electrode to the other through
the electrolyte to combine
there with their counterparts,
while electrons travel through
the external circuit producing
the electrical current.
Electrons
(e-)
Fuel
Permeable
Anode
Electrolyte
Oxidant
Permeable
Cathode
Fuel Oxidant
Cations
(+ve)
Anions (-ve)
4. Principle, construction and working of H2-O2 fuel cell

Working
The Fuel gas (hydrogen rich) is passed towards the anode where the
following oxidation reaction occurs:
H2 (g) = 2H+ + 2e-
The liberated electrons from hydrogen in anode side do not migrate
through electrolyte.
Therefore, they passes through the external circuit where work is
performed, then finally goes into the cathode.
On the other hand, the positive hydrogen ions (H+) migrate across
the electrolyte towards the cathode.

At the cathode side the hydrogen atom reacts with oxygen gas
(from air) and electrons to form water as byproduct according to:
H2 + 1/2 O2 +2e - H2O + Heat
fuel + oxidant product + Heat
The overall cell reaction is

The liberated electrons from the hydrogen are responsible for the
production of electricity.
The water is produced by the combination of hydrogen, oxygen and
liberated electrons and is sent out from the cell.
The DC current produced by fuel cell is later converted into AC current
using an inverter for practical application.
The voltage developed in a single fuel cell various from 0.7 to 1.4 volt.
More power can be obtained by arranging the individual fuel cell as a
stack. In this case, each single cell is sandwiched with one another by
a interconnect.
Therefore, electricity power ranging from 1 kW to 200 kW can be
obtained for domestic as well as industrial application.

Advantages
 Physical Security
 Reliability
 Efficiency
 Environmental Benefits
 Battery Replacement/Alternative
 Military Applications

Advantages
• Zero Emissions Or No pollution: a fuel cell vehicle only emits
water vapour. Therefore, no air pollution occurs.
• High efficiency: Fuel cells convert chemical energy directly into
electricity without the combustion process. As a result, Fuel cells
can achieve high efficiencies in energy conversion.
• High power density: A high power density allows fuel cells to be
relatively compact source of electric power, beneficial in application
with space constraints.
5. Advantage, disadvantage and applications

• Quiet operation: Fuel cells can be used in residential or built-up
areas where the noise pollution can be avoided.
• No recharge: Fuel cell systems do not require recharging.
Disadvantages
• It is difficult to manufacture and stores a high pure hydrogen
• It is very expense as compared to battery

advantages
 Physical Security : Both central station power generation
and long distance, high voltage power grids can be terrorist
targets in an attempt to cripple our energy infrastructure.
 Reliability : Properly configured fuel cells would result in
less than one minute of down time in a six year
period. U.S. businesses lose $29 Billion a year from
computer failures due to power outages.
 Efficiency : Because no fuel is burned to make energy, fuel
cells are fundamentally more efficient than combustion
systems.

advantages
 Environmental Benefits : Fuels cells can reduce air pollution
today and offer the possibility of eliminating pollution in the
future.
 Battery Replacement/Alternative : Fuel Cell replacements
for batteries would offer much longer operating life in a
packaged of lighter or equal weight.
 Military Applications : Fuel Cell technology in the military
can help save lives because it reduces telltale heat and noise in
combat.

Limitations
Economic Problems :
 Manufacturing cost of fuel-cell power plants is very high.
 The most important components of all p.e.m.f.c. and d.m.f.c.’s is
very expensive, about 700 $/m2.
 Total cost of a 5-kW p.e.m.f.c power plant is be about 1200 $/kW.
 In comparison cost of an analogous I.C. engine is 500-1500 $/kW.

limitations
The Problem Of Lifetime :
 Satisfactory lifetime for smooth operation.
 3 years lifetime for small plants in portable devices.
 5 years for electric vehicles.
 10 years for large stationary multi-megawatt power plants.
 Samples of single p.e.m.f.c and stacks have been successfully
operated for several thousands of hours.
 But not enough data available for general use of these type of
fuel cells.

Applications
1. Portable applications
• They used in portable appliances and power tools
• They can be used in small personal vehicles
• They are used Consumer electronics like laptops, cell phones can
be operated
• They can be used in Backup power

2. Transportation applications
They can be used for transport application in the following areas,
• Industrial transportation
• Public transportation
• Commercial transportation (truck, tractors)
• Marine and Military transportation

3. Power distribution application
• Fuel cells can be used for the distribution of power in
various fields such as,
• Homes and small businesses
• Commercial and industrial sites
• Remote, off-grid locations (telecom towers, weather stations)

Applications
Transportation
Stationary Power Stations
Telecommunications
Micro Power

 Transportation : All major automakers are working to
commercialize a fuel cell car.Automakers and experts speculate
that a fuel cell vehicle will be commercialized by 2010.
• Stationary Power Stations : Over 2,500 fuel cell systems have
been installed all over the world in hospitals, nursing homes,
hotels, office buildings, schools and utility power plants.
• Telecommunications : Due to computers, the Internet and
sophisticated communication networks there is a need for an
incredibly reliable power source. Fuel Cells have been proven to
be 99.999% reliable
Applications

Applications
Micro Power :
• Consumer electronics could gain drastically longer
battery power with Fuel Cell technology.
• Cell phones can be powered for 30 days without
recharging.
• Laptops can be powered for 20 hours without
recharging.

Uses of hydrogen fuel cells
There are many different uses of fuel cells being utilized right now. Some of these
uses are…
•Power sources for vehicles such as cars, trucks, buses and even boats and submarines
•Power sources for spacecraft, remote weather stations and military technology
•Batteries for electronics such as laptops and smart phones
•Sources for uninterruptable power supplies.

Fuel Cells and Energy
• A fuel cell is an electrochemical device that
converts energy produced from a chemical
reaction into electrical energy
i.e. Chemical Energy  Electrical Energy
– This chemical reaction is not a combustion
process

How does the Fuel Cell operate?
similar in converting chemical energy to electrical
energy but different in that
H2 in
A battery’s reactants
are self-contained
A fuel cell’s reactants
are supplied externally
H2 out
Air in
Air out
- +
-
+
Fuel Cell Vs Battery

What is a Fuel Cell?
Fuel cell is a device that converts chemical energy into
electrical energy, water, and heat through electrochemical reactions.
Fuel and air react when they come
into contact through a porous
membrane (electrolyte) which separates
them.
This reaction results in a transfer of
electrons and ions across the electrolyte
from the anode to the cathode.
 If an external load is attached to this
arrangement, a complete circuit is formed
and a voltage is generated from the flow
of electrical current.
The voltage generated by a single cell is typically rather small (< 1 volt), so many
cells are connected in series to create a useful voltage.

Similarities Between Fuel Cells and
Batteries
• A fuel cell is very similar to a battery in that a
battery also converts chemical energy to
electrical energy
• The electricity produced is DC
• Both use an electrolyte to conduct ions

Fuel Cells and Batteries Differences
• A battery is an energy storage device that has a fixed
amount of chemical energy
• A fuel cell will keep producing electricity as long as
fuel is supplied
• Fuel cell reactions do not degrade over time

1. Hydrogen
2. Electron flow
3. Load
4. Oxygen
5. Cathode
6. Electrolyte
7. Anode
8. Water
9. Hydroxyl ions
Hydrogen- Oxygen Fuel Cell

Construction & Working of a fuel cell
 Has two electrodes, anode and
cathode
 An electrolyte, which carries
electrically charged particles
from one electrode to the other
 A catalyst, which speeds the
reactions at the electrodes.
 Overall reaction is split into two
partial reactions : oxidation and
reduction

 Process begins when Hydrogen molecules enter anode
 Catalyst coating separates hydrogen’s negatively charged electrons
from the positively charged protons
 Electrolyte allows protons to pass through to cathode, but not
electrons
 Instead electrons are directed through an external circuit which
creates electrical current
 Oxygen molecules pass through cathode
 Oxygen and protons combine with electrons after they have
passed through the external circuit
 Oxygen and protons combine with electrons to produce water and
heat
Construction & Working of a fuel cell

1] Alkaline fuel cell (AFC)
 Operate on compressed
hydrogen and oxygen.
 Generally use solution of
potassium hydroxide (chemically
KOH) in water as their
electrolyte.
 Efficiency is about 70 percent
 Operating temperature is 150
to 200o C, (about 300 to 400o F)
 Cell output ranges from 300
W to 5 kW.

2] Direct-methanol fuel cell (DMFC)
Operating temperatures
are in the range
50-120 °C,
 Power outputs between
25 watts and 5 kilowatts
 Reactions :
Anode (oxidation) : CH3OH + 60H-  5H2O + 6e- + CO2
Cathode (reduction) : 3/2 O2 + 3H2O + 6e-  6OH-
Overall : CH3OH + 3/2 O2  CO2 + 2H2O

3] Phosphoric acid fuel cell (PAFC)
 Electrolyte is phosphoric acid
 Efficiency is 40 to 80 percent
 Operating temperature –
150 to 200oC (300 to 400o F)
 Output - up to 200 kW
 PAFCs tolerate a carbon
monoxide concentration of
about 1.5 percent

4] Molten-carbonate fuel cell (MCFC)
 Use high-temperature
compounds of salt (like sodium or
magnesium) carbonates
(chemically CO3) as the electrolyte
 Efficiency ranges from 60 to
80 percent
 Operating temperature is about
650o C (1,200 o F)
 Output upto 2 megawatts (MW)
 Reactions :
Overall reaction : CO + ½O2  CO2
Oxidation reaction : CO + CO3
2-  2CO2 + 2e-
Reduction reaction : ½O2 + CO2 + 2e-  CO3
2-

5] Solid-oxide fuel cell (SOFC)
 Use a hard, ceramic compound
of metal (like calcium or
zirconium) oxides (chemically, O2)
as electrolyte
 Efficiency is about 60 percent
 Operating temperatures are
about 1,000o C (about 1,800 o F)
 Cells output is up to 100 kW
 Reactions :
Reduction reaction : ½O2 + 2H+ + 2e-  H2O
Oxidation reaction : H2  2H+ + 2e-
Overall reaction : H2 + ½O2  H2O

6] Proton-exchange-membrane fuel cell (PEMFC)
 Work with a polymer electrolyte in
the form of a thin, permeable sheet
 Efficiency is about 40 to 50 percent
 Operating temperature is about 80o C
(about 175o F)
 Cell outputs generally range from 50 to
250 kW.
 Reactions :
Anode (oxidation): H2  2H+ + 2e-
Cathode (reduction): ½ O2 2H+ +2e- 
H2O
Overall : H2 + ½ O2  H2O

(ii) Kilo Calorie: 1 k cal = 1000 cal
(iii) British thermal unit: (B. T. U.) It is defined as the
amount of heat required to raise the temperature of 1
pound of water through 1oF.
1 B.T.U. = 252 Cal = 0.252 k cal
(IV) Centigrade heat unit (C.H.U): It is defined as
the amount of heat required to raise the temperature
of 1 pound of water through 1oC.
1k cal = 3.968 B.T.U.
= 2.2 C.H.U.

Characteristics and Types of Fuels

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