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A TECHNICAL PAPER PRESENTATION ON

Submitted to

Submitted by

Mr A
...
Chopra
(H
...
D
...
E
...
)

Roshan Kumar
EEE/07/350
7970710422
7th sem

ABSTRACT:
The electricity requirements of the world including India are
increasing at alarming rate and the power demand has been running
ahead of supply
...
Also
generation of electrical power by coal based steam power plants or
nuclear power plants causes’ pollution
...
MAGNETO HYDRO DYNAMIC (MHD) power generation is a new
unique method of power generation
...
The
fluid may be gas at elevated
temperature or liquid metal like
sodium or potassium
...

The negative charge tend to move in one direction, and the positive
charges in the opposite direction
...
In conventional steam power plants, the heat released by the fuel is
converted into rotational mechanical energy by means of a thermo cycle
and the mechanical energy is then used to drive the electric generator
...
Also, the
rotating machine has its associated losses and maintenance problems
...
The conventional electrical machines are basically electro mechanical
converters while an MHD generator is heat engine operating on a turbine
cycle and transforming the internal energy of gas directly into electrical
energy
...

If the gas is heated to high temperature it
gets converted into plasma and plasma is
conductor of electricity
...


HOW A MHD GENERATOR WORKS???
In a MHD generator, electrically conducting gas at a very high
temperature is passed at high velocity through a strong magnetic field at
right angles to the direction of flow, there by generating electrical energy
...
The current so obtained is direct
current which can be converted into ac by an inverter
...
On heating of a gas, the

outer electrons escape out from its atoms or molecules
...

However to achieve thermal ionization of products of combustion of fossil
fuels or inert gases extremely high temperatures are necessary
...
To have a
reasonable value of electrical conductivity of gases at temperatures around
2,000 to 3,000 K by reasonable ionization, the gases are seeded with
additives of easily ionizing materials (Alkali metals) such as Cesium or
Potassium
...


ANALYSIS:
An induced emf depends on the velocity of plasma and
magnetic field strength
...
B
This is the well known Hall effect observed in solids and liquids, and
also in gases under suitable conditions
...


The load factor K is a measure of the emf E due to the flow of current
through the circuit and is given by
K=

Closed Circuit Voltage
Open Circuit Voltage

The recommended value of K=1/2 so the power output P per unit
volume is given by
P

 V 2 B2
4

ELECTRODE CONFIGURATION OF MHD GENERATOR:
There are three possible arrangements of providing electrodes
for MHD generators
...
Segmented electrode configuration:

The electrode segments are separated by insulator
segments so there will be no current flowing in the
direction
...


2
...
In this case the hall
angle is minimized and thus the losses are reduced
...
Hall generator:
In this case the electrodes wrap up the channel
all the way in segment
...
Due to this reason there

cannot be any potential difference across the channel
...
The gases coming out at high temperature
(20000C) after seeding is passed through MHD at a velocity of 700 to
800m/sec
...
The gas leaving the MHD still contains large amount of
heat and seed material
...
The heat of the hot gases
coming out from MHD is used for steam generation before it is exhausted
into atmosphere
...
The power from the generator coupled to steam turbine and
power from MHD after converting from dc to ac is fed to the grid
...
It is estimated that the
thermal efficiency of MHD steam plant of 500MW capacity would be
around 50% and efficiencies upto 60% are expected in future
...
Any
type of fossil fuel can be used in MHD generator but a direct coal fired MHD
generator has following advantages:
1
...

2
...

3
...
It results in a
25% increase in the performance of the generator
...

The largest generator to date working on open cycle without steam
cycle is the American AVCO company machine of 40MW gross
capacity
...
The working of the system is exactly similar to
Open cycle MHD except the working fluid is continuously circulated in the
cycle instead of exhausting to the atmosphere
...
The noble gases with their low electron affinity are most
suitable
...

 The closed cycle MHD retains the seeding element, gives pollution
free operation and saves exhaust heat
...
Such a generator could be linked with thermal flux source such as
breeder reactor
...
The
liquid potassium coming out of the Breeder reactor at high temperature is
passed through a nozzle to increase its velocity before passing to MHD

generator
...
The following
are the advantages of Liquid metal system:

 The use of Nuclear energy as high temperature is not the
requirement of this system as in the case of a plasma converter
...

The size of the system including that of magnets is
comparatively smaller
...

Limitations:
 The metallic vapours are poor electrical conductors
...
This is because the liquids are practically in compressible
...

2
...

4
...

6
...

8
...

10
...

12
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14
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operational efficiency is high upto 50%
...

As there is no limitation to the size of the duct, so high capacity
generators are possible
...

Conceptually these generators are very simpler
...

The more efficient heat utilization reduces the amount of heat
discharged to environment and thus the cooling water requirements
are reduced
...

The overall costs of MHD power generation are estimated to be
lower (20%) than those of conventional power plants
...

The generator has high efficiency, construction is not limited by the
working temperature of the gas inside the duct but is controlled by
the nature of thermal source upstream of the generator
...

The closed cycle system produces power, free of pollution
...

It can be started and put on the line within few seconds
...

It can be used most economically as peak load plant
...
The fuel used is natural
gas
...

A 5-15 MW thermal input pilot plant is being set up in India at
Tiruchirapalli
...









Besides the use of MHD system for commercial electrical power
generation it has got other special uses
...
S
...

In India also considerable studies have been carried out in this field
under the National Council of Science and Technology (NCST)
...

MHD conversion has also been considered for ship propulsion,
airborne applications, hypersonic wind tunnel experiments and for
many other defence applications
...
Sufficient high temperature for thermal ionization can be sustained by
refractory materials
...

2
...

3
...

4
...
Although
the overall thermal efficiency is 60% against 40% for conventional
thermal plant, additional investment in the magnet, generator, duct,

compressors, scrubbers, seed recovery plant and DC to AC converters
may increase the plant cost and it may be much higher than
conventional plant
...
Most of the problems are related to material problems caused by high
temperature and highly corrosive and abrasive environment
...
Extensive research is going on in different countries
through out the world to find out the new resources to replace the
conventional fossil one
...
The magneto hydro dynamic power generation is
one of the examples of a new unique method of generation of electricity
...
Man being optimistic
should not leave the hopes on the success of this MHD generator as the
technology took the man to moon which was a dream long time back, the
same technology will help the human being to survive from the present
crisis of power shortage

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