Hydrogen Fuel Cell

By jignesh parmar

AIM:

To study the characteristics, properties and possibility of H2 as alternative fuel for automobiles.

OBJECTIVES:

To Describe properties of H2 in context of automobile fuel.

To Compare performance of H2 with petrol and diesel and other alternative fuels.

To List advantages & disadvantages of H2 as automobile fuel.

Why Hydrogen Fuel?

Considering increasing Energy demands and consequent high consumption of conventional fuels. (i.e., petroleum, natural gas and coal), are being depleted rapidly.

Also, their combustion products are causing global problems, such as the greenhouse effect, ozone layer

depletion, acid rains and pollution, which are posing great danger for our environment.

Available from renewable energy source. Energy stored in hydrogen would be available at any time and at any place on Earth.

MAIN PROPERTIESHydrogen is an odorless, colorless gas. With

molecular weight of 2.016, hydrogenIt is the lightest element. Its density is about

14 times less than air.Hydrogen is liquid at temperatures below

20.3 K (at atmospheric pressure). Hydrogen has the highest energy content per

unit mass of all fuels - higherheating value is 141.9 MJ/kg, almost three

times higher than gasoline

Performance Characterstis compared with other fuel

ADVANTAGESRenewable in nature.Clean fuel due to low emission of NOx and no

CO2Can be produced from variety of feed stocks.Requires low Ignition energy.Superior combustion characterstics.Adulteration free.High purity level available.

LIMITATIONSHigh flammability leads to an explosive

quality to the fuel-air mixture.Leak detection is difficult as it is odourless.On board storage is difficult due to low

energy volume density.(Huge storage space is required in compared

to other fuels)Pre ignition and backflash causes engine

design challenges.Expensive as production quantity is limited.Lack of distribution infrastructure.

HYDROGEN PRODUCTION AS A FUELCurrently Hydrogen is produced for industrial applications

from

Fossil Fuels (currently 90% of 42 mtons/yr) Coal - converted to mixture of hydrogen (50%), Natural Gas methane

1. by Direct cracking 2. Catalytic steam reforming; this is most efficient,

widely used, and cheapest method )Partial Oxidation of heavy oil

All of these methods release CO2

Water: Electrolysis (No CO2)

Other Methods (Solar energy) for Biomass gasification, Photocatalysis of biological system such as algae & bacteria.

Schematic Production methods

Possibility as practicable transport fuel At present on board storage of hydrogen is

the greatest challenge due to its very low density and hence very low energy volume ratio.

1. Liquefied in cryogenic containers.2. High pressure compressed gas.3. Absorbed in metals (in form of metal

hydride).4. Activated carbon storage.5. Glass micro spheresBut all techniques have their limitations of one

kind or the other which causes restricted application.

Hydrogen for fuel celled vehiclesA fuel cell is an electrochemical energy conversion

device which converts the chemical hydrogen and oxygen into water, and in the process it produces electricity.

2H2 + O2 → 2H2O (+285 kJ/mol)Fuel cell provides a DC (direct current) voltage that

can be used to power motors, lights or number of electrical appliances. The existing fuel cells are usually classified by their operating type and the type of electrolyte they use.

The main advantage of hydrogen fuel cell is that it does not consume the material it is composed of, like conventional batteries which are to be discarded after some time.

Fundamentals

Videal = 1.48 V per cell at STP

How do they work?•Fuel (H2) is first transported to the anode of the cell

•Fuel undergoes the anode reaction

•Anode reaction splits the fuel into H+ (a proton) and e-

•Protons pass through the electrolyte to the cathode

•Electrons can not pass through the electrolyte, and must travel through an external circuit which creates a usable electric current

•Protons and electrons reach the cathode, and undergo the cathode reaction

The main types of fuel cellsFuel Cell types Fuel Efficiency

(%) Operating temp. (oC)

PEM (Polymer exchange membrane fuel cell

H2 40-50 80

Direct Methanol (DMFC) Methanol, Ethanol

35 80

Solid Oxide (SOFC) H2, CO, CH4 45-55 700

Molten Carbonate (MCFC)

H2, CO, CH4 50-60 650

Phosphoric Acid (PAFC) H2 40-50 190

Alkaline (AFC) H2 50 50

*Green Power, Los Alamos National Lab, LA-UR-99-3231

* Honda Motor Company

Possible Commercial Scale Applications

Energy SectorMotor vehicles AviationSpace Expolaration

CONCLUSION: Careful analysis of continuing, large-scale use of

conventional fuels, will lead to the conclusion that Hydrogen is the ideal energy carrier of the future. Mainly, we refer to molecular Hydrogen, which is stable, non-polluting, abundant in nature, with high mass energy and can be used in practical applications but with future challenges with regard to

StorageCost of infrastructureEngine DesignDistributionPublic Safety