MAGNETO HYDRO DYNAMIC (MHD) POWER PLANTS
MHD power generatio n is a new
system of electric power generation which is said to be of high efficiency and
low pollution. In advanced countries MHD generator are widely used but in
developing countries li ke India it is still under construction. This con
struction work is in progress at Tiruchirapalli in Tamilnadu under joint
efforts of BARC (Bhab ha Atomic Research Centre), BHEL, Associated Cement
Corporation and Russian technologist s.
As its name implies,
magneto-hydro-dynamic (MHD) is concern ed with the flow of conducting fluid in
presence of magnetic and electric field. This fluid may be gas at elevated
temperature or liquid metal li ke sodium or potassium.
A MHD generator is a device for
converting heat energy of fuel directly into electric energy without a
conventiona l electric generator. The basic difference be tween conventional
generator and MHD generator is in the nature of conductor.
Principle
of MHD Power Ge neration
When an electric con ductor moves
across a magnetic field; an e mf is induced in it, which produced an electric
current. This is the principle of the conventi onal generator also, where the
conductors consists of copper strips.
In MHD
generator the solid conductors are replaced by a gaseo us conductor; i.e.an
ionized gas. If such gas is passed at high velocity through a powerful mag
netic field, a current is generated and can extract b y placing electrodes in a
suitable position in t he stream.
LAYOUT OF MHD POWER PLANT
A MHD conversion is known as
direct energy conversion because it produces electricity directly from heat
source without the necessity of the additi onal stage of steam generation as in
a steam po wer plant. An ionized gas is employed as a conducting field.
Ionization is produced either by thermal means i.e. by an elevated temperature or
by seeding with substance like cesium or potassium vapour which ionize at
relatively low temperature.
The atom of seed element split
off electrons. The presence of negatively charge electrons make the carrier gas
an electrical conductor.
Advantages
1. Large
amount of power is g enerated.
2. No moving
parts, so more reliable.
3. Closed
cycle system produ ces power, free of pollution.
4. Ability
to reach its full pow er as soon as started.
5. Size of
the plant is consider ably small.
6. Low
overall operation cost.
7. Better
utilization of fuel.
Disadvantages
1. Needs
very large magnets (high expensive).
2. Very high
friction and heat transfer losses.
3. It
suffers from the reverse flow of electrons through the conducting fluid s
around the ends
of the
magnetic field.
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