hydrogen cell
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Done by:
N.SANTHOSHA LAKSHMI P.UJWALA
4th B.Tech E.E.E. 4th B.Tech E.E.E.Email: [email protected] [email protected]
Contact no: 9494938762
AVR & SVR COLLEGE OF ENGINEERING AND
A FUTURE ENERGY SOURCE
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TECHNOLOGY
AYYALUR METTA, NANDYAL, KURNOOL (Dist), ANDHRA PRADESH.
A B S T R A C TWorld is witnessing a worsening
global warming situation as power generation
is continuously being increased throughout
the world using fossil fuels. Higher energy
generation through fossil fuel imparts
environmental degradation and is now a
matter of concern globally. The world
population is also expected to double by the
middle of the 21st
century and as a
consequence economic development will also
grow. As a result global demand for energy is
expected to increase substantially by 2050
(by about two to three times).
There is an energy technology that
can eliminate both air pollution and foreign
oil imports a device that is quiet, compact,
flexible, highly efficient and exceptionally
clean. It’s called the Fuel cell. This
nonpolluting power source is unique in its
potential applications: it can provide energy
for sources as large as a utility power station
and as small as a smoke detector. It is
perhaps the most important anti-pollution
technology in our history.
“Whereas the 19th Century was the century
of the steam engine and the 20th Century
was the century of the internal combustion
engine, it is likely that the 21st Century will
be the century of the fuel cell.”
What are fuel cells? How do they
work? Why are they so important? What are
the next steps for development of this crucial
technology? This paper presents a brief
description about fuel cells.
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CONTENTS
1 . INTRODUCTION OF FUEL CE LL
2 . PARTS OF FUEL CELL
3 . FUEL CELL OPE RATION
4 . TYPES OF FUEL CELLS
5 . FUEL FOR FUEL CELL
a) HYDR OGEN P RODUCTION
b) HYDROGEN S TORAGE
6 . APPLICATIONS OF FUEL CELL
7 . BENEFITS AND OBSTACLES TO THE SUCCESS OF F UEL CEL LS
8 . CONCLUSION
9 . R E F E R EN CE
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1 . I N T R O D U C T I O N O F F
U E LC E L L
What Is A Fuel Cell?
“Fuel cell is an electrochemical
device that continuously converts the
chemical energy of externally supplied fuel
and oxidant directly to electrical energy”.
The easiest way to understand fuel
cells is to think of them as a cousin to the
ordinary battery. Both produce electricity
through electrochemical reactions. The
difference lies in a fuel cell's ability to
constantly produce electricity as long as it
has a source of fuel where a battery needs to
be recharged. Consequently, since a fuel cell
does not store energy internally, a fuel cell
will not "run down" like a battery. Fuel cells
directly convert the fuel into electricity where
a battery has to replenish its electricity from
an external source.
History of fuel cell
Sir William Grove (1811-96), a
British lawyer and amateur scientist
developed the first fuel cell in 1839. The
principle was discovered by an accident
during electrolysis
experiment. When Sir William disconnected
the battery from the electrolyzer and
connected the two electrodes together,
he observed a current flowing in the
opposite direction, consuming the gases of
hydrogen and oxygen. He called this device a
“Gas Battery”. His gas battery consisted of
platinum electrodes placed in test tubes of
hydrogen and oxygen, immersed in a bath of
dilute sulphuric acid. It generated voltages of
about one volt.
There are many types of fuels for fuel cell:
hydrogen, natural gas, methanol, petrol. In
all cases, hydrogen is involved in the
electrochemical reaction inside the fuel
cell to generate electricity.
GAS BATTERY
Why is hydrogen used as a fuel?
■ Hydrogen has the highest energy
content per-unit-weight of any known fuel—
52,000 Btu/lb
(120.7 kJ/g).
■ Hydrogen burns cleanly. When
hydrogen is burned with oxygen, the only
by-products are heat and water. When it is
burned with air, which is about 68 percent
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nitrogen, some oxides of nitrogen are formed.
Fuel cells operate on hydrogen or a variety of
gaseous and liquid hydrocarbons. Electrolysis
is used to produce hydrogen from water in
areas where electricity is both abundant and
available at a low cost. Fuel processing
systems for reformation are used for
hydrocarbon fuels, such as natural gas,
methanol, ethanol, coal or gasoline.
Hydrogen is produced by reforming
hydrocarbon fuels at either a central fuel
station dispensing hydrogen through
distributed generation systems (off-board), or
at a fuel cell location (on-board). While the
use of fossil fuels to produce hydrogen does
not promise zero emissions, reformation
coupled with fuel cell technology can exploit
existing fuel infrastructure, and will offer
significant environmental improvements over
traditional internal combustion engine
systems. This is seen as an important step
towards a hydrogen-driven economy. No
greenhouse gas emissions exist with
electrolysis using renewable sources of
electricity, such as hydro, wind power,
photovoltaics, geothermal or nuclear power.
2 . P a r t s o f a F u e l C e l l :
Anode: The anode, the negative side
of the fuel cell, has several jobs. It conducts
the electrons that are freed from the hydrogen
molecules so that they can be used in an
external circuit. Channels etched into the
anode disperse the hydrogen gas equally over
the surface of the catalyst.
Cathode: The cathode, the positive
side of the fuel cell, also contains channels
that distribute the oxygen to the surface of the
catalyst. It conducts the electrons back from
the external circuit to the catalyst, where they
can recombine with the hydrogen ions and
oxygen to form water.
Polymer electrolyte membrane: The
polymer electrolyte membrane (PEM)—a
specially treated material that looks
something like ordinary kitchen plastic
wrap—conducts only positively charged ions
and blocks the electrons. The PEM is the key
to the fuel cell technology; it must permit
only the necessary ions to pass between the
anode and cathode. Other substances passingthrough the electrolyte would disrupt the
chemical reaction.
Catalyst
It accelerates the reactions at the electrodes?
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3 . F u e l c e l l o p e r a t i o n
The fuel cell is an electrochemical
devise, which converts chemical energy of
the fuel to electricity by combininggaseous hydrogen
with air in the absence of combustion. The
basic principles of operation of the fuel cell
is similar to that of the electrolyser in that
the fuel cell is constructed with two
electrodes with a conducted electrolyte
between them. The heart of the cell is the
proton conducting solid PEM. It is
surrounded by two layers, diffusion and a
reaction layer. Under constant supply of
hydrogen and oxygen the hydrogen diffuses
through the anode and the diffusion layer up
to the platinum catalyst, the reaction layer.
The reason for the diffusion current is the
tendency of hydrogen oxygen reaction.
Two main electrochemical reactions occur inthe fuel cell. One at the anode (anodic
reaction)
and one at the cathode.
At the anode, the reaction releases
hydrogen ions and electrons whose transport
is crucial to energy production.
H2→2H
+
+ 2e
-
The hydrogen ion on its way to the
cathode passes through the polymer
membrane while the only possible way for
the electrons is though an outer circuit. The
hydrogen ions together with the electrons of
the outer electric circuit and the oxygen
which has diffused through the porous
cathode
reacts to water.
2H+
+ ½ O2 + 2e-→H2O
This process occurs in all types of fuel cells.
4 . T y p e s o f F u e l C e l l s :
Fuel cells are classified primarily by
the kind of electrolyte they employ. This
determines the kind of chemical reactions that
take place in the cell, the kind of catalysts
required, the temperature range in which the
cell operates, the fuel required, and other
factors.
Ø Polymer Electrolyte
Membrane (PEM) Fuel Cells
Ø Direct Methanol Fuel Cells
Ø Solid Oxide Fuel Cells
Ø Alkaline Fuel Cells
Ø Phosphoric Acid Fuel Cells Ø
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Molten Carbonate Fuel Cells
Ø Regenerative Fuel Cells
Ø Comparison of Fuel CellTechnologies
In above only three technologies are most
useful those are explained by below table
PEMFC SOFC DMFC
ElectrolyteIonexchange
rane
ceramic Polymer
membrane
Operating
rature80
oc 1,000
oc 60-130
oc
Efficiency 40-60% 50-65% 40%
Typical
electricalUp to
250KW
>200K
W
<10KW
Possible
Application
s
Vehicles
Small
stationary
Power
stations
Portable
applications
Reactions At
anode: At
cathode:
2H2→4H+
+ 4e-
4H+
+O2+
4e-→H2O
2H2+2o2-
→ +
H2O+4e-
O2 + 4e-
2-
CH3OH+
H2O→6H++
6e-
6H+
+ 6e-
1½ H2O
5 . F U E L F O R F U E L C E L L
Since most fuel cells are powered by
hydrogen, one major issue is in which way
hydrogen will be generated.
5a) Hydrogen production:
Ideally this would be done by non-
polluting and renewable methods, such as
solar, wind or hydro power tidal, etc.
In principal, electrolysis is the
reverse reaction of a fuel cell; electricity is
added to split water into its constituent
elements resulting in the production of
hydrogen and oxygen.
There are two types of production of
hydrogen those are alkaline, PEM
electrolysis.
Alkaline electrolysis:
In this electricity is used to split water
into oxygen and hydrogen. the electrolyte
contains hydrogen and oxygen atoms and
when current is applied these are split into
ions due to the current the ions will
attracted to each electrode at anode
oxygen is form and at cathode hydrogen is
obtained.
This electricity can be produced byrenewable energy
sources
PEM electrolysis:
In PEM electrolysis the electrolyte is asolid polymer
exchange membrane. It is reversal process to
the PEM fuel cell in
this on the anode side of the membrane water
is split into hydrogen and
oxygen. Hydrogen is then split into
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hydrogen ion that migrates
through membrane and electron that follows
the applied current on
the cathode side hydrogen ion and
electrons reacts and create
hydrogen
At anode:
At cathode:
5b) Hydrogen storage:
Hydrogen can be stored in the following
ways:
• Compressed gas storage(pressure storage)
•
Liquidstorage
• Metal
halide storage
•
Methanol storage
Hydrogen is difficult to store compared togasoline. Gasoline is a liquid while hydrogen
is a gas
.Hydrogen at normal pressure has a volume3100 times higher than gasoline.
Different hydrogen storage methods are usedto reduce the storage volume.
Pressure storage:
Pressure storage of hydrogen reduces
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the storage volume .The higher pressure the
lower the volume. However increasing the
pressure costs energy.
Today hydrogen can be stored under pressure
up to 700 bars. The
normal pressure for hydrogen storage is 200
bars. At 200 bars, hydrogen
has a volume 13 times greater than gasoline,
and at 700 bar 6, 4 times
greater.
Liquid storage:
Hydrogen stored in liquid form
reduces the storage volume. Cooling
hydrogen to -253degrees makes it liquid.
Cooling however costs energy and hydrogen
in liquid form will diffuse out of the tank over
time. Hydrogen in liquid form has a volume
3, 6 times higher has gasoline
Metal hydride storage:
Hydrogen can also be stored in metal
powder; the so called metal hydrides. When
cooling is applied hydrogen atoms will move
inside metal structures. To release hydrogen
again heat must be applied.
Metal hydride storage is very safe due
to a very low pressure and that very little
hydrogen is in free form inside the tank.
Metal hydride holds a potential for
storing hydrogen at very low volumes.
Methanol storage:
90% of the atoms in the universe are
hydrogen, and many materials therefore
contain hydrogen. Methanol also contains
hydrogen. Methanol is liquid and very similar
gasoline. Hydrogen
stored in methanol has a volume 1, 8 timeshigher than gasoline
6 . A p p l i c a t i o n s :
6.1) Transportation
Fuel cell technology promises to meet
t
h e
most stringent emissions legislation.
However, if fuel cells are to replace theinternal combustion engine,
the technology must not only
meet tightening legislation,
but also be able to reach
operating temperature rapidly,
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provide competitive fuel economy and give a
responsive performance. Proton exchange
membrane fuel cells (PEMFC) are best
placed to meet these requirements. With a
low operating temperature (80°C), PEMFC
can reach operating temperature quickly.
Able to respond rapidly to varying loads,
this type is twice as efficient as internal
combustion engines. PEMFC also have the
highest power density from the current fuel
cell range, a crucial factor when space
maximization is such an important
consideration in vehicle designs.
Furthermore, the solid polymer electrolyte
helps to minimize potential corrosion and
safety management problems. In order to
avoid catalyst poisoning at this low
operating temperature PEMFC need
uncontaminated hydrogen fuel. Most major
vehicle manufacturers regard the PEMFC as
the successor to the internal combustion
engine. Successful tests of buses have already
taken place in several cities and more are
scheduled to follow, notably in Europe, where
nine cities will trial three fuel cell buses from
2003.
6.2) Large Stationary
The most advanced fuel cells are
presently large stationary units providing
electricity and heat. Their attractiveness
includes their efficiency and low emissions.
They are also of use in areas not served by
a national power grid or where the national
grid is unreliable and backup power is
required. With operating temperatures as
low as 80°C, fuel
cells can be installed in private households
and light commercial operations as well as
meeting all the energy requirements of large
industrial operations. So far fuel cell
manufacturers have focused on non-
residential applications. UTC Fuel Cells, for
instance, has installed over 250 phosphoric
acid fuel cells (PAFC) at a range of sites,
including schools, office blocks and banking
facilities. In the future, high temperature fuel
cells, such as molten carbonate (MCFC) and
solid oxide (SOFC), may be adapted for
larger industrial applications. With
operating temperatures between 600-
1100°C these high temperature cells can
tolerate a contaminated source of hydrogen
and hence can use unreformed natural gas,
diesel or gasoline. Furthermore, the heat
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generated can be used to produce electricity
by driving steam turbines.
6.3) Small Stationary
There is also significant potential for
small stationary units (which we have defined
as anything with a power output below
10kW). In this field the heat and power
requirements of private households or small
businesses could be met by low temperature
proton exchange membrane (PEM) or SOFC.
Units could power individual houses or
groups of homes and could be designed to
m
ee
t
al
l
of
th
e
energy requirements of the inhabitants, or
only the base load, with peak demands
covered in another way.
House hold usage of fuel cell:
The renewable energy is not a stable
energy source. Power is only produced when
sun is shining and wind is blowing (i.e. when
presence of alternative energy sources) there
fore the excess of energy can be stored in the
form hydrogen through electrolysis. And
when the electricity is needed (usually
night periods) the stored hydrogen can be
transformed into electrical energy through
fuel cell. The side figure shows the usage of
fuel cell
6.4) Portable
Fuel cells promise to be an important
source of power for mobile electronic
devices, offering key advantage
over
conventio nal
batteries,
increased operating
times, reduced
weight and ease of recharging. At present
most research has focused on a variation of
the low temperature proton exchangemembrane (PEM) fuel cell, the direct
methanol fuel cell (DMFC). As the name
implies these fuel cells run on a methanol-
water mix fed directly into the unit without
prior reforming. Using methanol, DMFCs
offer a great advantage over solid batteries in
that recharging will just involve refilling with
the liquid fuel.
6.5) Military
Military applications are expected to
be a
significan
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t niche market for fuel cell technology. Their
efficiency, versatility, extended running time
and quiet operation make fuel cells extremely
well suited for the power needs of military
services. In various forms, fuel cells could
provide power for the majority of military
equipment from portable handheld devices
used in the field to land and sea
transportation.
7 . BENEFITS AND OBSTACLES TO THE
SUCCESS OF FUEL CELLS
7 . 1 ) B e n e f i t s
• Fuel cells are efficient. Fuel cell systemefficiency is independent of the rated power
above
100 kW, unlike oil, gas or coal burning
power plants, where the efficiency is constant
only at the megawatt power level. Even at the
40% of the rated load, a fuel cell has almost
the same efficiency as that of the full load.
• Fuel cells are clean. If hydrogen is
the fuel, there are no pollutant emissions from
a fuel cell itself, only the production of pure
water. In contrast to an internal combustion
engine, a fuel cell produces no emissions of
sulphur dioxide, which can lead to acid rain,
nor nitrogen oxides which produce smog nor
dust particulates.
• Fuel cells are quiet. A fuel cell
itself has no moving parts, although a fuel
cell system may have pumps and fans. As a
result, electrical power is produced relatively
silently. Many hotels and resorts in quiet
locations, for example, could replace diesel
engine generators with fuel cells for both
main power supply or for backup power in
the event of power outages.
• Fuel cells are modular. That is, fuel
cells of varying sizes can be stacked together
tomeet a required power demand. As
mentioned earlier, fuel cell systems can
provide power over a large range, from a few
watts to megawatts.
• Fuel cells are environmentally
safe. They produce no hazardous waste
products, and their only by-product is water
(or water and carbon dioxide in the case of
methanol cells). Fuel cells are also able to
respond fast to load changes, because the
electricity is generated by a chemicalreaction.
7.2) Obstacles
At present there are many
uncertainties to the success of fuel cells and
the development of a hydrogen economy:
• Fuel cells must obtain mass-
market acceptance to succeed. This
acceptance depends largely on price,
reliability, longevity of fuel cells and the
accessibility and cost of fuel. Compared to
the price of present day alternatives e.g.
diesel-engine generators and batteries, fuel
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cells are comparatively expensive. In order
to be competitive, fuel cells need to be
mass produced less expensive materials
developed.
• An infrastructure for the mass-market
availability of hydrogen, or methanol fuel
initially, must also develop. At present there
is no infrastructure in place for either of these
fuels. As it is we must rely on the activities
of the oil and gas companies to introduce
them. Unless motorists are able to obtain
fuel conveniently and affordably, a massmarket for motive applications will not
develop.
• At present platinum is a key
component to fuel cells. Platinum is a scarce
natural resource; the largest supplies to the
world platinum markets are from South
Africa, Russia and Canada. Shortages of
platinum are not anticipated, however
changes in Government policies could affect
the
supply.
· Fuelling fuel cells is still a major
problem since the production, transportation,
distribution and storage of hydrogen is
difficult.
· Fuel cells are in general slightly
bigger than comparable batteries or engines.
However, the size of the units is decreasing.
8 . C O N C L U S I O N
As our demand for electrical power grows, it
becomes increasingly urgent to find new
ways of meeting it both responsibly and
safely. In the past, the limiting factors of
renewable energy have been the storage and
transport of that energy. With the use of fuel
cells and hydrogen technology, electrical
power from renewable energy sources can be
delivered where and when required, cleanly,
efficiently and sustainably.
In the hydrogen economy. India will
enjoy a secure, clean, and prosperous energy
sector that will continue for generations to
come. Indian consumers will have access to
hydrogen energy to the same extent that they
have access to gasoline, natural gas, and
electricity today. It will be produced cleanly,
with near-zero net carbon emissions, and it
will be transported and used safely. It will
be the
‘fuel of choice’ for Indian businesses andconsumers.
India as a developed nation
Abdul kalam’s vision 2020 is not so
far .2020 is the year to see India as a
developed nation. For that we require surplusof energy and it is possible by using
hydrogen energy in form of fuel cells since it
is very abundant than any other fossil fuel.
9 . R e f e r e n c e s :
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h t tp :// www .u t c po wer .c o m/ f s / c o m /b i n /f s_ c om
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h t tp :// www .efcf .c o m/ r e p o r t s / E04.pdf
h t tp :// g lt r s.g rc .n a s a . g ov / r e po r t s / 2006 / TM -
2006 - 2 1 4054.pdf