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.
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.
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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