Go, Change the World
Report
Course Title: RENEWABLE ENERGY SOURCES
AND STORAGE
Course Code: 18G7H07
on
“HYDROGEN FUEL CELL”
Submitted by
NAME
ADITHYA PISSAY S
DHANYA H U
S KANDHA KUMARAN
VAIBHAV B A
USN
1RV18EC005
1RV18EI018
1RV18EI048
1RV18EI060
Under the Guidance of
Name of the Guide:
Dr. Anitha G.S
Associate Professor
Department of EEE
2020-21
Go, Change the World
CERTIFICATE
Certified that the Internship work titled “HYDROGEN FUEL CELLS” carried
out by ADITHYA PISSSAY S bearing USN: 1RV18EI005, DHANYA H.U.
bearing USN: 1RV18EI018, S KANDHA KUMARAN bearing
USN:1RV18EI048, VAIBHAV B.A. bearing USN: 1RV18EI060, a bonafide
student, submitted in partial fulfillment for the award of 7 th semester B.E in
Electronics and Instrumentation Engineering of RV College of Engineering ®,
Bengaluru, affiliated to Visvesvaraya Technological University, Belagavi,
during the year 2020-21. It is certified that all corrections/suggestions indicated
for internal assessment have been incorporated in the report deposited in the
departmental library. The Internship report has been approved as it satisfies the
academic requirement in respect of internship work prescribed for the said
degree.
MAXIMUM
MARKS
OBTAINED
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20
Hydrogen Fuel Cell
Introduction
A fuel cell is an electrochemical reactor which converts chemical energy into
electrical energy. Fuel cells are different from most batteries in requiring a continuous
source of fuel and oxygen (usually from air) to sustain the chemical reaction, whereas
in a battery the chemical energy usually comes from metals and their ions or oxides
that are commonly already present in the battery, except in flow batteries. Fuel cells
can produce electricity continuously for as long as fuel and oxygen are supplied.
The generated voltage for a single solid oxide fuel cell is in the range of 0.7 to 13 V
(depending on fuel and electrical current). The maximum current depends on intrinsic
parameters and the area of the MEA (membrane electrolyte assembly) and is given by
the maximum current density.
Hydrogen fuel cells are a clean, emissions-free alternative to traditional combustion
processes, and use hydrogen to generate energy via electrochemical reactions. These
cells are made even more environmentally friendly when the hydrogen is produced via
sustainable means.
Fuel cells that use pure hydrogen fuel are completely carbon-free, with their only
byproducts being electricity, heat, and water. Some types of fuel cell systems are
capable of using hydrocarbon fuels like natural gas, biogas, methanol, and others.
Because fuel cells generate electricity through chemistry rather than combustion, they
can achieve much higher efficiencies than traditional energy production methods such
as steam turbines and internal combustion engines. To push the efficiency even
higher, a fuel cell can be coupled with a combined heat and power system that uses
the cell’s waste heat for heating or cooling applications.
Fuel cells are also scalable. This means that individual fuel cells can be joined with
one another to form stacks. In turn, these stacks can be combined into larger systems.
Fuel cell systems vary greatly in size and power, from combustion engine
replacements for electric vehicles to large-scale, multi-megawatt installations
providing electricity directly to the utility grid.
Fuel cells offer a variety of applications, from transportation to emergency back-up
power, and can power systems as large as a power plant or as small as a laptop.
RENEWABLE ENERGY SOURCES AND STORAGE
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Hydrogen Fuel Cell
Working of Hydrogen Fuel cells
Hydrogen fuel cells generate electricity using a chemical reaction. Each fuel cell has
two electrodes; a negative anode and a positive cathode. The reaction to produce the
electricity happens at these electrodes, with an electrolyte carrying electrically
charged particles between them and a catalyst to speed up the reactions.
The process by which a fuel cell works can be summarised as follows:
• Hydrogen atoms enter at the anode, while oxygen is fed to the cathode
• The hydrogen atoms are separated into protons and electrons at the anode
• Reaction at the anode:
2H2 → 4H+ + 4e−
This is an example of an oxidation reaction.
• The now positively charged protons pass through the membrane (or electrolyte)
to the cathode, with the negatively charged electrons take a different route as
they are forced through a circuit to generate electricity.
• The hydrogen ions (protons) that are produced from the hydrogen at the anode
travel through the electrolyte in the fuel cell to the cathode. Oxygen supplied to
the cathode reacts with these hydrogen ions and electrons arriving via the
external circuit to produce water and heat, both of which are removed from the
fuel cell.
• Reaction at the cathode:
O2 + 4H+ + 4e− → 2H2O
This is an example of a reduction reaction.
Figure 1: Working of Hydrogen Fuel Cell
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Hydrogen Fuel Cell
Chemistry behind of the process
In electrochemistry, the Eocell value (energy) of a fuel cell is equal to the Eo of the
cathode half-reaction minus the Eo of the anode half-reaction. For a hydrogen fuel cell,
the two half reactions are shown above. So, to calculate the energy of one fuel cell, we
need to subtract the anode energy from the cathode energy.
For a HFC, the
Eocell
= 0.68V – 0.00V which equals 0.68V
Single fuel cells do not generate a large amount of electricity, so they are arranged
into stacks to create enough power for their intended purpose, whether that is
powering a small digital device or a power plant.
Fuel cells work like batteries but, unlike batteries, they will not run down or need
recharging and can continue to produce electricity while the fuel source (in this case,
hydrogen) is supplied.
Being comprised of an anode, cathode and an electrolyte membrane, there are no
moving parts in a fuel cell, making them silent in operation and highly reliable.
Types of hydrogen fuel cell
Fuel cells are generally characterized by the type of electrolyte material. These cells
are mainly consisted of: Alkaline Fuel Cell (AFC), Molten Carbonate Fuel Cell
(MCFC), Phosphoric Acid Fuel Cell (PAFC), Proton Exchange Membrane Fuel Cell
(PEMFC), Solid Oxide Fuel Cell (SOFC), and Biofuel Cell. The below figure
compares and illustrates the prominent features of these cells.
Figure 2: Comparison of Hydrogen Fuel Cells
RENEWABLE ENERGY SOURCES AND STORAGE
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Hydrogen Fuel Cell
Working of some of the different types of fuel cells are given below:
1. Alkaline fuel
Alkaline fuel cell (AFC) AFCs are the first and the only type of cells to have reached
successful routine applications mainly in space explorations such as space shuttle
mission in the United States. AFCs use liquid electrolyte solution of potassium
hydroxide (KOH) due to its high alkaline hydroxide conductibility. The AFCs
generate electricity from hydrogen in which hydroxyl ion (OH− ) from potassium
hydroxide migrates from the cathode to the anode. At the anode, hydrogen gas reacts
with the OH− ions to produce water and release electrons. The overall reactions are
given as below:
Anode 2H2 + 4OH− → 4H2O + 4e−
Cathode O2 + 2H2O + 4e− → 4OH−
Overall cell reaction: 2H2 + O2 → 2H2O + electrical energy + heat
Figure 3: Alkaline Fuel Cell
2. Molten carbonate fuel cell (MCFC)
MCFCs are high-temperature fuel cells that use an electrolyte composed of a molten
carbonate salt mixture (salt of sodium or magnesium carbonate) suspended in a
porous, chemically inert ceramic lithium aluminum oxide (LiAlO2) matrix. In MCFCs
the electrolytes are heated to 650°C, and the salts melt and conduct carbonate ions
(CO3 2-) from the cathode to the anode. At the anode, hydrogen oxidation reaction
combines with carbonate ions producing water and carbon dioxide and releasing
electrons to the external circuit. At the cathode, oxygen is reduced to
RENEWABLE ENERGY SOURCES AND STORAGE
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Hydrogen Fuel Cell
carbonate ions by combining with carbon dioxide and electrons from the external
circuit, therefore, electrochemical reactions are as below:
Anode H2 + CO3 2− → H2O + CO2 + 2e−
Cathode ½O2 + CO2 + 2e− → CO3 2−
Overall cell reaction: H2 + ½ O2 → H2O + electrical energy + heat
Figure 4: Molten Carbonate fuel cell
3. Solid oxide fuel cell (SOFC)
Solid oxide fuel cells (SOFCs) are best suited for large-scale stationary power
generators that are able to provide electricity for factories and towns. SOFCs mainly
use a hard ceramic compound of metal, such as calcium oxide or zirconium oxide as
the electrolyte. Hydrogen and carbon monoxide can be used as the reactive fuels in
SOFCs. SOFCs are expected to be around 50%–60% efficient at converting fuel to
electricity. In applications designed to capture and utilize the system’s waste heat (cogeneration), overall fuel use efficiencies could be up to 80–85%.
Solid oxide fuel cells operate at very high temperatures of 1000°C. The oxygen is
supplied, usually from air at the cathode. At these high temperatures, oxygen ions
(with a negative charge) migrate through the crystal lattice. When a fuel gas
containing hydrogen passes over the anode, a flow of negatively charged oxygen ions
move across the electrolyte to oxidize the fuel. When hydrogen is used as the fuel the
reactions are:
Anode H2 + O2− → H2O + 2e−
RENEWABLE ENERGY SOURCES AND STORAGE
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Hydrogen Fuel Cell
H2 + ½O2 → H2 O + electrical energy + heat
And when carbon monoxide is the fuel the reactions are:
Anode CO + O2− → CO2 + 2e−
Cathode ½ O2 + 2e− → O2−
Overall CO + ½ O2 → CO2
Figure 5: Solid Oxide fuel cell
Advantages of Hydrogen Fuel Cell
•
•
•
•
•
•
High efficiency
Modular
Quiet
Non-Polluting; Doesn’t produces oxides of Nitrogen
Distributed
Combined heat and power
• Load flexible
Problem of Hydrogen fuel Cell
• Lack of hydrogen infrastructure
• Need for refueling stations
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Hydrogen Fuel Cell
• Lack of consumer distribution system
• Cost of hydrogen fuel cells
• 2009 Department of Energy estimated $61/kw
• Honda FCX Clarity costs about half a million dollars to make
Application
•
Power sources for vehicles such as cars, trucks, buses and even boats and
submarines
•
Power sources for spacecraft, remote weather stations and military technology
•
Batteries for electronics such as laptops and smart phones
•
Sources for uninterruptable power supplies
Figure 6: Application of different fuel cells
Case Study
•
The fuel cell is associated to auxiliaries in order to work like a battery. It is
then considered as a fuel cell system.
•
In mobile applications, the fuel cell is not reversible. It is not possible to send
electricity and produce hydrogen at 700 bar to fill the tank.
•
The fuel cell system is finally included in a fuel cell powertrain.
•
A fuel cell powertrain is similar to a hybrid powertrain, including a small
battery in parallel.
RENEWABLE ENERGY SOURCES AND STORAGE
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Hydrogen Fuel Cell
The fuel cell needs air and hydrogen to produce electricity. These are supplied
with a compressor and a pump. There is a delay of 1 to 2 seconds when higher
current is requested. This delay is not visible for the user as the battery
compensates immediately.
•
The battery is also used to recover energy during braking.
•
The DC current produced by the fuel cell must be transformed by power
electronics in order to be used. An inverter is often considered to transform DC
current into 3 phase AC current. In vehicular applications, the load will be an
electric motor. In this machine, the rotor is moving due to a force induced by
the rotating magnetic field (RMF) generated by the stator coils.
High voltage Battery
or FC
•
Figure 7: Diagram of a DC/AC reversible converter
Figure 8: 3 coils supplied with AC current are generating a rotating magnetic field
RENEWABLE ENERGY SOURCES AND STORAGE
Page 8
Hydrogen Fuel Cell
•
The fuel cell is associated to auxiliaries in order to work like a battery. It is
then considered as a fuel cell system.
•
In mobile applications, the fuel cell is not reversible. It is not possible to send
electricity and produce hydrogen at 700 bar to fill the tank.
•
The fuel cell system is finally included in a fuel cell powertrain.
•
A fuel cell powertrain is similar to a hybrid powertrain, including a small
battery in parallel.
•
The fuel cell needs air and hydrogen to produce electricity. These are supplied
with a compressor and a pump. There is a delay of 1 to 2 seconds when higher
current is requested. This delay is not visible for the user as the battery
compensates immediately.
•
The battery is also used to recover energy during braking.
Figure 9: A complete fuel cell powertrain of a vehicle
The fuel cell and the auxiliaries deliver electricity to the inverter that powers an
electric motor. A high voltage battery connected in parallel serves as an energy buffer.
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Hydrogen Fuel Cell
Efficiency
•
A fuel cell is like every machine, not perfect. Despite the fact that there are no
parts in motion, the materials are real and induce losses. They currently
measure a global efficiency of 60%
•
As a result, we observe a voltage drop when a current is produced. This is
represented by the polarization curve.
•
A fuel cell needs auxiliaries to work properly, these are:
A) Intake air management: filter, compressor, air cooling, humidifier, pressure and
flow management valves. It is completed by the exhaust of the fuel cell where only
water is produced.
B) Hydrogen management: tank valves, pressure regulator, injector(s), hydrogen
pump and a purge valve
C) A cooling circuit is mandatory to dissipate the heat produced by the fuel cell,
large radiators are generally necessary as 40% of the total power is heat.
Activation polarisation
Cell voltage (V)
Total losses
Ohmic polarisation
Concentration polarisation
Theoretical voltage
Current density (A/cm2)
Figure 10: Efficiency Curve
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Hydrogen Fuel Cell
REFERENCES
• https://www.twi-global.com/technical-knowledge/faqs/what-is-a-hydrogenfuel-cell#HowDoesAHydrogenFuelCellWork
• https://slideplayer.com/slide/17455853/
• https://www.yumpu.com/en/document/view/4576643/architecture-of-planarsofc-stacks-with-parallel-connected-ensem
• https://en.wikipedia.org/wiki/Fuel_cell#:~:text=The%20electrolyte%20substan
ce%2C%20which%20usually,most%20common%20fuel%20is%20hydrogen
RENEWABLE ENERGY SOURCES AND STORAGE
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