INTRODUCTION
Unlike
normal batteries fuel cells supply electricity as long as it supplied with
fuel. Inside the fuel cell electricity generate by chemical reaction. Fuel cell
consist of three major parts anode, cathode electrolyte and catalyst make reactions
faster. Electrolyte act as iron exchanging medium .Different types of fuel
cells are designed using different types of electrolytes.
APPERATUS
·
PEM fuel.
·
Two Multimeters.
·
Rheostat.
·
Electrolyzes to provide Hydrogen.
PROCEDURE
·
Container is filled with distill water
up to indicated mark.
·
Use battery and solar panel parallel to
generate power which requires generating H2.
·
After sufficient amount of H2
production connects electrolyzer to the one end of the fuel cell while other
end of the fuel cell closed.
·
Measure the voltage and currents varying
the resistance of the external circuit.
CALCULATION
Resistance (Ω)
|
Voltage (V)
|
Current (mA)
|
Power (W)
|
Open
circuit
|
4.21
|
0
|
0.00
|
330
|
3.84
|
10
|
0.04
|
100
|
3.56
|
30
|
0.11
|
50
|
3.3
|
70
|
0.23
|
31
|
3.17
|
100
|
0.32
|
1.1
|
1.08
|
150
|
0.16
|
0.55
|
0.18
|
180
|
0.03
|
0
|
0.1
|
180
|
0.02
|
Current
at maximum power = 100mA
Voltage
at maximum power =1.2V
Resistance
at maximum power =12Ω
Discussion
1. Types of fuel cells and their difference, use and
performances
1.1Alkaline
Fuel Cell
Alkaline fuel cell is most historical fuel
cell which is developed. In these types of fuel cells KOH is used as the electrolyte.
Inside the cell OH- irons travelsfrom cathode to anode and react with hydrogen
gas hence produce water and release electrons near the anode. Electrons migrate
through an external circuit to cathode and reacts with oxygen and produce OH-
irons.
1.1.1Performance
·
Efficiency around 60-70% which is
considered as high efficiency.
·
Typically used to generate power
10-100kW.
·
Operating at 65-220C temperature.
1.1.2 Advantages
·
High performance due to fast cathode
reaction.
·
Wide range of electro catalysts can be
used.
·
Low cost components.
·
Produce water as a byproduct.
1.1.3 Disadvantages
·
React with CO2 so fuel and
air must be CO2 free.
·
Using expensive catalyst like platinum.
1.1.4 Applications
·
Used for military and space
applications. Mainly due to material durability issues commercially this
technology to be used.
1.2
Polymer Electrolyte Membrane (PEM) Fuel Cells.
In PEM fuel cells used solid polymer as an
electrolyte, porous carbon electrodes and platinum catalyst. Unlikealkaline
fuel cells oxygen is directly taken from atmosphere but pure hydrogen is required.
Catalyst platinum is highly sensitive to CO so hydrogen which is derived from hydrocarbon
or alcohol must be filtered.H2 divided into protons and electrons at
anode. Then electrons travel to cathode through the external circuit while H+
irons travels through the electrolyte. H+ irons and electrons react with the
oxygen and produce water.
1.2.1Performance
·
Efficiency around 60-35%.
·
Generate power up to 1–100kW.
·
Operating at very low temperature which
is 50-100C.
1.2.2
Advantages
·
Solid electrolyte reduces corrosion&
electrolytemanagement problems.
·
Quick startup.
·
Low operating temperature.
·
Produce water as a byproduct.
·
Low power to weight ratio.
1.2.3 Disadvantages
·
React with CO so fuel must be CO free.
·
Using expensive catalyst like platinum.
1.2.4 Applications
·
Special electric vehicle batteries.
·
Portable and backup power
·
Transportation.
1.3Phosphoric
Acid Fuel Cells.
Anode and cathode reactions are similar to
the PEM fuel cells but electrolyte is different.Liquid phosphoric acid as an
electrolyte is used. This type of fuel cells is used for stationery power
genera ration. As a fuel cellit has very low efficient but by cogeneration
electricity and heat it can reach 85% efficiency.
1.3.1Performance
·
Efficiency around 40%.
·
Generate power up to 100–400kW.
·
Operating at 150-200C temperature.
1.3.2Advantages
·
Very high efficiency as cogenerating
heat and electricity.
·
Can withstand fuel impurities.
1.3.3 Disadvantages
·
Platinum catalyst
·
Long start up time
·
Low current and power.
1.3.4 Applications
·
Special electric vehicle batteries.
1.4
Molten Carbonate Fuel Cells.
These
types of fuel cells used in coal-based power plants for their electricity
requirement. Molten carbonate fuel cells contain molten carbonate salt mixture
and use ceramic lithium aluminum oxide as a catalyst. Because of the high
operating temperatures non-precious metals can be used.
Anode reaction: CO32-
+ H2 => H2O + CO2 + 2e-
Cathode Reaction: CO2+ 1/2O2 + 2e- =>
CO32-
Molten
carbonate melts in high temperatures generating carbonate irons. Because of
high operating temperature startup time is very low.
1.4.1Performance
·
Efficiency around 45-50%.
·
Generate power up to 300kW–3MW.
·
Operating at 600-700C temperature.
1.4.2Advantages
·
Very high efficiency as cogenerating
heat and electricity.
·
Can use variety of catalyst.
·
Fuel flexibility.
1.4.3 Disadvantages
·
High temperature can reduce lifespan of
the battery.
·
Long start up time
·
Low current and power.
1.4.4 Applications
·
Distributed generation.
·
Electric utility.
1.5Solid
Oxide Fuel Cell.
These
types of fuel cells have solid electrolyte which is made of non-porous ceramic
compound. no need for plate type cell constructionBecause of the solid
electrolyte. Fuel operating temperature is very high so need to have expensive
metals which reduce cost of the fuel cell. By cogenerating electricity and heat
high efficiency can be achieved. It has very slow start up time mainly due totime taken to reach high temperatures. Because
of the temperature and weight can’t use for portable operations.
Anode Reaction: 2 H2
+ 2 O2- => 2 H2O + 4 e-
Cathode Reaction: O2
+ 4 e- => 2 O2-
1.4.1Performance
·
Efficiency around 60%.
·
Generate power up to 1–3MW.
·
Operating at 600-1000C temperature.
1.4.2Advantages
·
Very high efficiency as cogenerating
heat and electricity.
·
Can use variety of catalyst.
·
Fuel flexibility.
·
Solid electrolyte.
1.4.3 Disadvantages
·
High temperature can reduce lifespan of
the battery.
·
Long start up time
·
Low current and power.
·
Can’t use for portable applications.
1.4.4 Applications
·
Distributed generation.
·
Electric utility.
·
Auxiliary power.
2.Shortcomings
of existing fuel cell technology.
Main
problem is most of the fuel cell use H2 as fuel which is not naturally
existing gas which need to be generated. If there is an fuel cell which take CO2
as fuel then its become very effective. Another is space requirement for H2
storage and H2 is very flammable gas so extra precautions need to be
taken which reduce portability of the fuel cell. Most of the fuel s is
operating at high temperatures which restrict the applications.
H2
is considered as renewable energy mainly because it can be generated by water.
For generating H2 electricity is required and natural source like
solar power can be used to generate the electricity. Storing H2 is
much effective than storing electricity but more risky than other fuels. .Fuel
cell is the one that convert H2 into electricity. Hydrogen fuel
cells in vehicles proved to be more efficient than Ic combustion engine.
Toyota
Highlander FCHV-adv hydrogen fuel cell vehicle achieved an incredible average
fuel economy of 68.3 miles per kilogram of hydrogen In the other hand Toyota
Highlander Hybrid that is powered by gasoline gets an EPA-estimated 26 miles per gallon.
Weight of a 1L liquid hydrogen = 0.070752Kg.
Weight of a 30L liquid hydrogen =
2.12Kg.
So
weight of liquid hydrogen is much lower than gasoline .so energy that can be
carrying by gasoline is much higher than gasoline. But carrying hydrogen is
much risky and special costly storages are required. Hydrogen fuel cells like
PEM operates at very low temperature while internal combustion engine has high
temperatures which resulting thermal energy lost But IC engine convert chemical
energy directly to motion while fuel cells convert chemical energy into electric
energy and it need to be converted in to kinetic energy.