hydrogen fuel cell technology
TRANSCRIPT
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