In this Presentation I have discussed about FUEL CELL PROPERTY FOR ELECTRIC VEHICLE. Comparision of Various EV with respect to FCEV is discussed with the help of IEEE paper.What are the Fuel Cell properties required for Vehicle.

1. Shri Ramdeobaba College of Engineering & Management
(An Autonomous Institute under UGC Act)
Department of Electrical Engineering
Assignment 6 Seminar
FUEL CELL PROPERTY FOR ELECTRIC VEHICLE
Presented by
1) SHEIKH MOHAMMAD SAJID
Roll No. 07
2) SHUBHAM JIBHAKATE
Roll No. 08
PEPS Branch RCOEM
Guided by
DR. MOHAN RENGE
Professor
EE Dept. RCOEM

2. FUEL CELL ELECTRIC VEHICLE
FCEVs also go by the name Fuel Cell Vehicle (FCV). They got the name because the heart of
such vehicles is fuel cells that use chemical reactions to produce electricity. Hydrogen is the fuel
of choice for FCVs to carry out this reaction, so they are often called ‘hydrogen fuel cell
vehicles’. FCVs carry the hydrogen in special high pressure tanks, another ingredient for the
power generating process is oxygen, which it acquires from the air sucked in from the
environment. Electricity generated from the fuel cells goes to an electric motor which drives the
wheels. Excess energy is stored in storage systems like batteries or super capacitors.
Commercially available FCVs like the Toyota Mirai or Honda Clarity use batteries for this
purpose. FCVs only produce water as a byproduct of its power generating process which is
ejected out of the car through the tailpipes. The configuration of an FCV is shown in Figure.

3. BASIC DEFINATION
Electrical work is, in general, described by the relation:
W = EIΔt
where E is the cell voltage and
I is the current.
•In a fuel cell reaction, electrons are transferred from the anode to the cathode, generating a
current.
•The amount of electricity (IΔt) transferred when the reaction occurs is given by
NF,
where N = number of electrons transferred
F = Faraday’s constant = 96,493 coulombs.
•So the electrical work can be calculated as: W = NFE (Work done on the surrounding)
THERMODYAMICS 1ST LAW
It is usually formulated by stating that the change in the internal energy (∆H) of a closed
system is equal to the amount of heat supplied (Q) to the system, minus the amount of
work (W) performed by the system on its surroundings.
ΔH = Q - W
The First Law then becomes: ΔH = Q - NFE

4. 2ND LAW OF THERMODYNAMICS
Consider the fuel cell to be ideal for now, meaning that it is reversible and thus behaves
as a perfect electrochemical apparatus :
“ If no changes take place in the cell except during the passage of current, and all
changes which accompany the current can be reversed by reversing the current, the cell
may be called a perfect electrochemical apparatus.”
Heat transferred during a reversible process was expressed as:
Q = T ΔS
Where, T = absolute temperature,
ΔS = change in entropy
Combining the First and Second Law analysis, we get
ΔH = TΔS – NFE _________________________(2)
NFE = - (ΔH - TΔS ) _________________________(3)
Gibbs Free Energy is given by
G= H – TS Or ΔG = ΔH-(T ΔS-S ΔT)
ΔG = ΔH-T ΔS ___________________________(4)
As there is no change in temperature ΔT = 0
Eqn (2) becomes NFE = - Δ G)

5. PHYSICAL INTERPRETATION OF dG=dH- TdS
•dH represents the total energy of the system.
•TdS represents the “unavailable” energy (that which cannot be converted to useful
work).
•G represents the “free” energy or the energy available to do useful work.
FUEL CELL EFFICIENCY
Fuel cells use materials that are typically burnt to release their energy, the fuel cell
efficiency is described as the ratio of the electrical energy produced to the heat that is
produced by burning the fuel.
From the basic definition of efficiency:
η = W / Qin

6. •A very useful feature of fuel cells is that their efficiency can be very easily
found from their operating voltage.
•The reasoning behind this is as follows.
•If one mole of fuel is reacted in the cell, then two moles of electrons are
pushed round the external circuit.

7. PRACTICAL FUEL CELL VOLTAGES
In practice the actual cell voltage is less. Now of course this applies to ordinary
batteries too, as when current is drawn out of any electric cell the voltage falls, due to
internal resistances. However, with a fuel cell this effect is more marked than with
almost all types of conventional cell. Figure shows a typical voltage/current density
curve for a good PEM fuel cell. It can be seen that the voltage is always less, and is
often much less, than the 1.18V that would be obtained if all of the Gibbs energy were
converted into electrical energy.

8. THERE ARE THREE MAIN REASONS FOR THIS LOSS OF
VOLTAGE
1. The energy required to drive the reactions at the electrodes, usually called the
activation energy, causes a voltage drop. This is especially a problem at the air
cathode, and shows itself as a fairly constant voltage drop. This explains the initial
fall in voltage even at quite low currents.
2. The resistance of the electrolyte and the electrodes causes a voltage drop that more
or less follows Ohm’s law, and causes the steady fall in voltage over the range of
currents. This is usually called the Ohmic voltage loss.
3. At very high currents, the air gets depleted of oxygen, and the remnant nitrogen gets
in the way of supplying fresh oxygen. This result is a fall in voltage, as the
electrodes are short of reactant. This problem causes the more rapid fall in voltage at
higher currents, and is called mass transfer or concentration voltage loss.

9. CLASSIFICATION OF LOSSES IN FUEL CELL SYSTEM
Activation Losses: These losses are caused by the slowness of the reaction taking place
on the surface of the electrodes. A proportion of the voltage generated is lost in driving
the chemical reaction that transfers the electrons. This voltage drop is closely related to
the materials of electrodes and the catalysts. The Tafel equation is most commonly used
to describe this behavior, by which the voltage drop is expressed as
Where Ideal gas constant R=8.314
Faradays constant F=96487 coulombs
Excahange current density i0=10-6.12 A/cm2
Ohmic Losses: The voltage drop due to the resistance to the flow of electrons through
the material of the electrodes. This loss varies linearly with current density.
Where Re is the equivalent ohmic resistance per area
and i is the current density

10. Concentration Losses: Losses that result from the change in concentration of the
reactants at the surface of the electrodes as the fuel is used.
Fuel Crossover Losses: Losses that result from the waste of fuel passing through the
electrolyte and electron conduction through the electrolyte. This loss is typically small,
but can be more important in low temperature cells.
There are three distinct regions of a
fuel cell polarization curve:
• At low power densities, the cell
potential drops due to activation
polarization.
• At moderate current densities, the
cell potential decreases linearly with
current due to ohmic losses.
• At high current densities, the cell
potential drop departs from the
linear relationship with current
density due to concentration
polarization (mass transport losses).

11. THE EFFECT OF PRESSURE AND GAS CONCENTRATION
If the change of system pressure is the issue, then the Nernst equation takes the form:
Where ΔV is the voltage increase if the pressure changes from P1 to P2.
• Other causes of voltage change are a reduction in voltage caused by using air instead
of pure oxygen.
• The use of hydrogen fuel that is mixed with carbon dioxide, as is obtained from the
‘reforming’ of fuels such as petrol, methanol or methane, also causes a small reduction
in voltage.
•For high temperature fuel cells the Nernst equation predicts very well the voltage
changes.
•However, with lower temperature cells, such as are used in electric vehicles, the
changes are nearly always considerably greater than the Nernst equation predicts.

12. FUEL CELL SYSTEM
CHARACTERISTICS
In practice, fuel cells need auxiliaries
to support their operation. The
auxiliaries mainly include an air
circulating pump, a coolant
circulating pump, a ventilation fan, a
fuel supply pump, and electrical
control devices as shown in Fig. 1.
Among the auxiliaries, the air
circulating pump is the largest energy
consumer. The power consumed by
the air circulating pump (including its
drive motor) may take about 10% of
the total power output of the fuel cell
stack. The other auxiliaries consume
much less energy compared with the
air circulating pump.
Fig. 1. A hydrogen–air fuel cell system

13. In a fuel cell, the air pressure on the electrode surface, p, is usually higher than
the atmospheric pressure, p0. According to thermodynamics, the power needed
to compress air from low-pressure p0 to high-pressure p with a mass flow m .
air can be calculated by
where γ = the ratio of specific heats of air (1.4),
R = the gas constant of air (287.1 J/kg K), and
T = the temperature at the inlet of the compressor in K.
When calculating the power consumed by the air-circulating pump, the energy
losses in the air pump and motor drive must be taken into account. Thus, the
total power consumed is
where ηap is the efficiency of the air pump plus motor drive.

14. Fig. 2. shows an example of the operation characteristics of the hydrogen–air
fuel cell system, where λ=2, p/p0=3 and ηap=0.8, and the net current and net
power are the current and power that flow to the load (see Fig. 1.).
•This figure indicates that the optimal operation region of the fuel cell system is
in the middle region of the current range, say, 7 to 50% of the maximum current.
•A large current leads to low efficiency due to the large voltage drop in the fuel
cell stack and, on the other hand, a very small current leads to low efficiency
due to the increase in the percentage of the auxiliaries’ energy consumption.
Fig. 2. Cell voltage, system
efficiency, and net power
density varying with net
current density of a hydrogen–
air fuel cell

15. Main issues in the fuel cell There are many problems and challenges for fuel cells
to overcome before they become a commercial reality as a vehicle power source.
The main problems centre on the following issues.
•Cost: Fuel cells are currently far more expensive than IC engines, and even hybrid
IC/electric systems.
•Water management: It is not at all self-evident why water management should be such
an important and difficult issue with automotive fuel cells.
•Cooling: The thermal management of fuel cells is actually rather more difficult than
for IC engines.
•Hydrogen supply: Hydrogen is the preferred fuel for fuel cells, but hydrogen is very
difficult to store and transport. There is also the vital question of ‘where does the
hydrogen come from’ these issues are so difficult and important.
However, there is great hope that these problems can be overcome, and fuel cells
can be the basis of less environmentally damaging transport.

17. INTRODUCTION
Detailed computer simulations demonstrate that all electric vehicles will be required to
meet our energy security and climate change reduction goals1 . As shown in Figure 1,
hybrid electric vehicles (HEV’s) and plug-in hybrid electric vehicles (PHEV’s) both
reduce greenhouse gas (GHG) emissions, but neither of these vehicles that still use
internal combustion engines will be adequate to cut GHGs to 80% below 1990 levels,
the goal set by the climate change community, even if biofuels such as cellulosic
ethanol are used in place of gasoline to power the internal combustion engines

18. Similarly, Figure 2 shows that HEV’s and PHEV’s powered by biofuels could not
reduce oil consumption in the US to levels that would allow us to produce most of our
petroleum from American sources if needed in a crisis. To achieve oil “quasi-
independence” and to cut GHGs to 80% below 1990 levels, we will have to eliminate
the internal combustion engine from most light duty vehicles. We will have to
transition to all electric vehicles over the next few decades to meet our societal goals.

19. 1) SPECIFIC ENERGY
Figure 3 compares the specific energy (energy per unit weight) of current deep
discharge lead acid (PbA) batteries, nickel metal hydride (Nigh), Lithium Ion and
the US ABC (Advanced Battery Consortium) goal with the specific energy of a
PEM fuel cell plus compressed hydrogen storage tanks. Two hydrogen pressures
are shown: 5,000 psi and 10,000 psi with fiber wrapped composite tanks. The
10,000 psi tanks weigh more than the 5,000 psi tanks due to the requirement for
extra fiber wrap to provide the needed strength2 .

20. 2) VEHICLE WEIGHT
Compressed hydrogen and fuel cells can provide electricity to a vehicle traction motor
with weights that are between eight to 14 times less than current batteries, and four
times less than the US ABC goal. As a result, EVs must be much heavier than FCVs for
a given range, as shown in Figure 4. This chart is based on a 5passenger Ford AIV
(aluminum intensive vehicle) Sable with a FCEV test weight of 1280 kg, drag
coefficient of 0.33, frontal area of 2.127 m2 , and rolling resistance of 0.0092.

21. 3)ENERGY DENSITY
Some analysts are concerned about the volume required for compressed gas hydrogen
tanks. They do indeed take up more space than a gasoline tank, but compressed
hydrogen tanks take up much less space (including the fuel cell system) than batteries
for a given range. The basic energy density of the hydrogen fuel cell system in watt-
hours per liter is compared with that of batteries in Figure 5

22. 4)STORAGE VOLUME
The battery EV requires more stored energy per mile than the FCEV as a result of the
heavier batteries and resulting heavier components. The net effect on the volume
required for the energy supply on the car is shown in Figure 6, again as a function of
range. The space to store lead acid batteries would preclude a full five passenger
vehicle with a range of more than 150 miles, while the NiMH would be limited in
practice to less than 200 to 250 miles range.

23. 5)BATTERY PERFORMANCE ASSUMPTIONS
The previous charts assume somewhat optimistic battery parameters for both specific
energy and specific power. We placed star symbols on Figure 7 from Kromer and
Heywood4 of MIT to illustrate the energy and power ratings used in this model. In all
cases we have assumed higher specific energy and power levels than existing capability
for each battery technology. That is, the stars lie above the broad curves of existing
performance for each battery. We have assumed in particular that the Liion battery
technology achieves the BEV goal of 150 Wh/kg and 300 W/kg, well above current Li-
ion battery system achievements. Note that Liion batteries have demonstrated 150
Wh/kg, but only at very low power levels. Similarly Liion batteries with very thin
plates have achieved up to 800 W/kg specific power levels, but only at very low energy
levels that would be totally unsuitable for a BEV. These curves demonstrate that all
battery technologies involve a tradeoff between energy and power. For hybrid vehicles
power is the major driver, since the onboard fuel provides stored energy via the internal
combustion engine. An all electric vehicle requires much more energy storage, which
involves sacrificing specific power. In essence, high power requires thin battery
electrodes for fast response, while high energy storage requires thick plate

24. Figure 7. Specific Energy vs. Specific Power for battery technologies from Kromer and
Heywood (MIT), May 2007; star symbols indicate the battery parameters used in this
study that are all more optimistic than current battery performance

25. 6)GREEN HOUSE GASESOUS
For frame of reference, the gasoline ICE version of the AIV Sable produces about 480
g/mile of CO2equivalent emissions, so the hydrogen FCV would immediately cut GHG
emissions by more than 50% compared to regular cars. This GHG calculation includes
all “welltowheel” GHGs adjusted for a 100year atmospheric lifetime.

26. CONCLUSION
The fuel cell EV is superior to the advanced Liion battery full function EV on six major
counts; the fuel cell EV:
1. Weighs less
2. Takes up less space on the vehicle
3. Generates less greenhouse gases
4. Requires less welltowheels energy
5. Takes less time to refuel

27. THANK YOU.