The document provides an overview of solar cells and fuel cells, detailing their construction, function, and applications. Solar cells convert light energy into electrical energy using semiconductors like silicon, while fuel cells generate electricity through electrochemical reactions involving hydrogen and oxygen. Both technologies are presented as sustainable energy solutions with various applications, including rural electrification and powering vehicles.

1. FUEL CELL AND SOLAR CELL
NAME : SHRINIVAS KALE
CLASS : T.E. (A)
DATE : 08/04/2019
PROGRESSIVE EDUCATION SOCIETY’S
MODERN COLLEDGE OF ENGINEERING

2. SOLAR CELL

3. INTRODUCTION :
A SOLAR CELL is a solid state electrical device that converts energy of
light directly into electricity by Photoelectric Effect.
A SOLAR CELL is also known as Photovoltaic Cell or Photoelectric Cell.

4. CONSTRUCTION :
Photovoltaic cells are made of special materials called semiconductors such as
silicon.
An atom of silicon has 14 electrons, arranged in three different shells.
The outer shell has 4 electrons.
Therefore a silicon atom will always look for ways to fill up its last shell, and to
do this, it will share electrons with four nearby atoms.
Now we use phosphorus(with 5 electrons in its outer shell).
Therefore when it combines with silicon, one electron remains free.

5. When energy is added to pure silicon it can cause a few electrons to break free
of their bonds and leave their atoms.
These are called free carriers, which move randomly around the crystalline
lattice looking for holes to fall into and carrying an electrical current.
But our impure silicon with phosphorous atoms takes a lot less energy to knock
loose one of our "extra“ electrons because they aren't tied up in a bond with
any neighbouring atoms.
As a result, we have a lot more free carriers than we would have in pure silicon
to become N-type silicon.

6. The other part of a solar cell is doped with the element boron(with 3 electrons
in its outer shell)to become P-type silicon.
Now, when this two type of silicon interact, an electric field forms at the
junction which prevents more electrons to move to P-side.
When photon hits solar cell, its energy breaks apart electron-hole pairs. Each
photon with enough energy will normally free exactly one electron, resulting in
a free hole as well. If this happens close enough to the electric field, this causes
disruption of electrical neutrality, and if we provide an external current path,
electrons will flow through the P side to unite with holes that the electric field
sent there, doing work for us along the way.

7. The electron flow provides the current, and the cell's electric field causes a
voltage.
Now to protect the solar cell, we use antireflective coating to reduce the losses
and then a glass plate to protect the cell from elements.

8. APPLICATION :
Rural electrification: The provision of electricity to rural areas derives important
social and economic benefits to remote communities throughout the world like
power supply to remote houses, electrification of the health care facilities,
irrigation and water supply and treatment.
Ocean navigation aids: Many lighthouses are now powered by solar cells.
Telecommunication systems: radio transceivers on mountain tops are often
solar powered.
Photovoltaic solar generators have been and will remain the best choice for
providing electrical power to satellites in an orbit around the Earth.

9. CONCLUSION :
Argument that sun provides power only during the day is countered by the fact
that 70% of energy demand is during daytime hours. At night, traditional
methods can be used to generate the electricity.
Goal is to decrease our dependence on fossil fuels.
Solar cell light absorbing materials can be stacked to take advantage of different
light absorption and charge separation mechanisms.

10. FUEL CELL

11. INTRODUCTION :
 Fuel cells are electrochemical cells consisting of two electrodes and an
electrolyte which convert the chemical energy of chemical reaction
between fuel and oxidant directly into electrical energy.

12. CONSTRUCTION :
 The purpose of a fuel cell is to produce an electrical current that can be
directed outside the cell to do work, such as powering an electric motor or
illuminating a light bulb or a city.
 Because of the way electricity behaves, this current returns to the fuel cell,
completing an electrical circuit. The chemical reactions that produce this
current are the key to how a fuel cell works.
 There are several kinds of fuel cells, and each operates a bit differently. But in
general terms, hydrogen atoms enter a fuel cell at the anode where a
chemical reaction strips them of their electrons.
 The hydrogen atoms are now "ionized," and carry a positive electrical charge.
The negatively charged electrons provide the current through wires to do
work. If alternating current (AC) is needed, the DC output of the fuel cell must
be routed through a conversion device called an inverter.

13.  Oxygen enters the fuel cell at the cathode and, in
some cell types (like the one illustrated above), it
there combines with electrons returning from the
electrical circuit and hydrogen ions that have
traveled through the electrolyte from the anode.
 In other cell types the oxygen picks up electrons
and then travels through the electrolyte to the
anode, where it combines with hydrogen ions.
 The electrolyte plays a key role. It must permit only
the appropriate ions to pass between the anode
and cathode. If free electrons or other substances
could travel through the electrolyte, they would
disrupt the chemical reaction.

14.  Whether they combine at anode or cathode, together hydrogen and oxygen
form water, which drains from the cell. As long as a fuel cell is supplied with
hydrogen and oxygen, it will generate electricity.
 Even better, since fuel cells create electricity chemically, rather than by
combustion, they are not subject to the thermodynamic laws that limit a
conventional power plant (see "Carnot Limit" in the glossary). Therefore, fuel
cells are more efficient in extracting energy from a fuel. Waste heat from some
cells can also be harnessed, boosting system efficiency still further.

15. TYPES OF FUEL CELLS :
FUEL CELL OPERATING CONDITIONS
Alkaline FC (AFC) Operates at room temp. to 80 0C, Apollo fuel cell
Proton Exchange
Membrane FC (PEMFC)
Operates best at 60-90 0C, Hydrogen fuel, Originally developed by GE for
space
Phosphoric Acid FC (PAFC) Operates best at ~200 0C, Hydrogen fuel, Stationary energy storage
device
Molten Carbonate FC
(MCFC)
Operates best at 550 0C, Nickel catalysts, ceramic separator membrane,
Hydrocarbon fuels reformed in situ
Solid Oxide FC (SOFC) Operates at 900 0C, Conducting ceramic oxide electrodes, Hydrocarbon
fuels reformed in situ
Direct Methanol Fuel Cell
(DMFC)
Operates best at 60-90 0C, Methanol Fuel, For portable electronic devices

16. COMMERCIALLY IMPORTANT FUEL CELLS :
Phosphoric Acid Fuel Cell
Polymer Electrode to Membrane Fuel Cell

17. Characteristic features PEMFC PAFC
Primary fuel H2 H2
Electrodes Graphite Carbon
Electrolyte Polymer membrane(Per fluoro
sulphonic acid)
Phosphoric acid soaked in
silicon matrix
Catalyst Pt Pt
Operating temperature 50 – 1000C (typically 800C) 150 – 2000C
Major applications Stationary and automotive
power
Stationary power
Advantages o Solid electrolyte reduce
corrosion & electrolyte
o management problems
o Operates at low temperature
o Quick start up
o Higher temperature
o combines heat power
o Increases tolerance to fuel
o impurities
Disadvantages o Expensive catalyst
o Sensitive to fuel impurities
o Expensive catalyst
o Long start time
o Low current & power

18. ADVANTAGES :
High efficiency of energy conversion (approaching 70%) from chemical
energy to electrical energy.
Low noise pollution & low thermal pollution.
Fuel cell power can reduce expensive transmission lines & minimize
transmission loses for a disturbed system.
Hydrogen-Oxygen fuel cells produce drinking water of potable quality.
Designing is modular, therefore the parts are exchangeable.
Low maintenance cost.

19. APPLICATIONS :
The first commercial use of fuel cell was in NASA space program to generate
power for satellites and space capsules.
Fuels are used for primary and backup power for commercial, industrial and
residential buildings in remote and inaccessible area.
They are used to power fuel cell vehicles including automobiles, aero planes,
boats and submarines.

20. THANK YOU