Hydrogen Cell

8/4/2019 Hydrogen Cell

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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



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.



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





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



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?



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



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



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



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,



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



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



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



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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