Transcript Power sources

ELECTRICAL
ENGINEERING SCIENCE
CHAPTER 1
POWER SOURCES
Content
• Classification of power sources.
• Electrochemical primary and secondary batteries and introduction to
fuel cells.
Classification of Power sources
There are two types of power sources
1) Voltage source
2) Current source
Symbols of Power Sources
Voltage Source
A device which can produce a continuous force to move the
electrons (or, continuous voltage) through the wire connected into the
two terminals of the device is called a Voltage Source.
There are two types of the Voltage Source which are:
• Direct Voltage Source
• Alternating Voltage Source
Direct Voltage Source

A device which produces a continuous direct voltage output is called a
Direct Voltage Source.

For example: Cells , Battery , DC Generator.

A direct voltage is the kind of voltage whose polarity remains the
same.

Direct Voltage causes the current to move only in one direction
continuously.
Alternating Voltage Source

A device which produces a alternating voltage output is called a
Alternating Voltage Source. For example: AC Generator , DC to AC
converter etc.

A alternating voltage is the kind of voltage whose polarity is reversed
periodically. Alternating Voltage causes the current to move in one
direction for a period and then in another direction for another period.
Ideal Voltage Source

An Ideal Voltage source is a kind of Voltage source whose
internal resistance is zero.

Such that the supplied voltage does not changes even if the
external load resistance changes.
Current Source

A current source is a device which provides the regular flow of
electrons or current on a circuit.

A current source is a type of voltage source which have enough
EMF and surplus electrons so as to produce the flow of electrons.
Direct Current Source

The current source made of a Direct Voltage Source is called
Direct Current Source.
Alternating Current Source

The current source made of a Alternating Voltage Source is
called Alternating Current Source.
Ideal Current Source

A current source which provides a constant current without any
relation with the voltage supplied to the load is called Ideal Current
Source.
Electro Chemical
Primary
and
Secondary
Batteries
Electrochemical Cell
An electrochemical cell is a device capable of either generating
electrical energy from chemical reactions or facilitating chemical
reactions through the introduction of electrical energy.
Difference between Cell & Battery
• The cell is the basic single electrochemical unit which converts
chemical energy to electrical energy.
• Battery refers to a stack (group) of Cells
CLASSIFICATION OF BATTERIES
There are four types of batteries.
1. Primary Batteries (or) Primary Cells
2. Secondary Batteries (or) Secondary Cells
3. Fuel Cells (or) Flow Batteries
4. Reserve cell
Primary Battery

Primary cells are those cells in which the chemical reaction occurs only once
and the cell becomes dead after sometime. These batteries are used as source of
dc power.

Eg : Dry cell (Leclanche Cell) and Mercury cell, lithium cell, Carbon-Zinc cell,
Silver-oxide cells.

Primary cells can be further classified as either wet or dry.
Secondary Battery
These are the cells that can be recharged by passing an electric
current through them and can be used again and again.
Ex: 1) Lead storage battery
2) Nickel-Cadmium battery
3) Lithium-ion cell battery
Comparison between Primary & Secondary cell
Primary battery or cell
Secondary battery or cell
Lower initial cost.
Higher initial cost.
Higher life-cycle cost (Rs/kWh).
Lower life-cycle cost (Rs/kWh) if charging in
convenient and inexpensive.
Disposable.
Regular maintenance required.
Disposable.
Periodic recharging required.
Replacement readily available.
Replacements while available, are not produced in
the same sheer numbers as primary batteries.
Comparison between Primary & Secondary cell
Primary battery or cell
Secondary battery or cell
Typically lighter and smaller; thus traditionally more
suited for portable applications.
Traditionally less suited for portable applications,
although recent advances in Lithium battery
technology have lead to the development of
smaller/lighter secondary batteries.
Longer service per charge and good charge retention.
Relative to primary battery systems, traditional
secondary batteries exhibit inferior charge retention.
Not ideally suited for heavy load/high discharge rate
performance.
Superior high discharge rate performance at heavy
loads
Comparison between Primary & Secondary cell
Primary battery or cell
Secondary battery or cell
Not ideally suited for load-leveling, emergency
backup, hybrid battery, and high cost military
applications.
Ideally suited for load-levelling , emergency backup,
hybrid battery and high cost military applications
Traditionally limited to specific applications.
The overall inherent versatility of secondary battery
systems allows its use and continuing research for a
large spectrum of applications.
INTRODUCTION TO FUEL CELLS
•
A fuel cell is like a battery which generates electricity from an electrochemical
reaction.
•
Fuel cell uses external supply of chemical energy and can run indefinitely, as long
as it is supplied with a source of hydrogen and a source of oxygen (usually air). It contains
two electrodes i.e. anode and cathode separated by solid or liquid electrolyte.
It needs two types of fuel :
1) hydrogen
2) oxygen(air)
Fuel Cell
Fuel Cell
Fuel Cell
Overall reaction: 2 H2(gas)+ O2 (gas)→2 H2O + energy
PARTS OF FUEL CELL
• Anode
• Cathode
• Electrolyte + catalyst
• Hydrogen gas
• Oxygen(air)
Fuel cells have many advantages over heat engines. These include:
1. high efficiency,
2. virtually silent operation and
3. if hydrogen is the fuel, there are no pollutant emissions.
Types
of
Fuel
Cell
•Polymer Electrolyte Membrane Fuel Cells (PEMFC)
•Direct Methanol Fuel Cells (DMFC)
•Alkaline Fuel Cells (AFC)
•Phosphoric Acid Fuel Cells (PAFC)
•Molten Carbonate Fuel Cells (MCFC)
•Solid Oxide Fuel Cells (SOFC)
•Regenerative Fuel Cells (RFC)
•Zinc Air Fuel Cells (ZAFCs)
•Microbial Fuel Cells (MFCs)