2. INTRODUCTION
What is MHD?
MHD power generation is a new system of electric
power generation.
This technique is of high efficiency and low
pollution.
It is concerned with the flow of a conducting fluid
in presence of Magnetic & Electric field.
Fluid may be Gas or liquid metal like-sodium or
potassium.
3. What is MHD generator ?
It is a device for converting heat energy of a
fuel(Fossil) directly into electrical energy without a
conventional generator.
In system, MHD converter system is a heat engine.
Here heat is taken up at a higher temperature is partly
converted into useful (electrical)work & the remainder
is rejected at a low temperature.
It design outputs of the order of 1000 MW.
4. Principal of MHD Power Generation
The principle of MHD generation is simply that
discovered by Faraday :
”when an electric conductor moves across a magnetic
field, a voltage is induced in it which produces an electric
current”.
In MHD generator, the solid conductors are replaced by a
gaseous conductor; an ionized gas.
5. What is (MHD) energy conversion ?
The movement of a conducing fluid through a
magnetic field may also employed for electric energy
conversion when a fluid is used, this technique is
called MHD, energy conversion.
Conversion occur by flow of electrical conducing
fluid, usually a gas or a gas liquid combination,
through a stationary magnetic field.
6. Several factor Reducing the efficiency of
converter. They are:
i. Dissipation of energy in the internal resistance of the
ionized gas.
ii. A space charge barrier at the electrode surface.
iii. Heat transfer through the electrode the electrode & insulator
walls.
iv. Various losses associated fluid with fluid friction etc.
7. Classification of MHD Systems
The MHD systems can be classified broadly as follows:
Open cycle systems.
Closed cycle systems.
This may be further sub classified as:
Seeded inert gas systems &
Liquid metal system.
8. COMPARISON BETWEEN MHD SYSTEMS
Open Cycle system
The working fluid is used on the once through basis.
Working fluid is after generating electrical energy is
discharged to atmosphere through a stack.
The working fluid is Air. Also oil or gasified coal or hot
gases can be used as working fluid.
Higher working temperature & better thermal efficiency
is possible.
It provide power conversion at high temperature at 2500
K.
9. Closed cycle system
The working fluid is continuously re-circulated.
The discharged working fluid is reheated & returned to the
converter.
Helium & Argon is used as working fluid.
Thermal efficiency is less as compare .
It provide more useful power conversion at low temperature at
1900 K.
10. Advantage of MHD system
The conversion efficiency of an MHD system can be
around 50% as compare to less than 40% for most
efficient steam plant.
Large amount of power is generated.
It has no moving parts so more reliable.
It has ability to reach the full power level as soon as
started.
11. The closed cycle system produces power free of pollution.
The size of plant is considerably smaller than conventional
fossil fuel.
Overall Operational cost in MHD plant would be about 20%
less than in conventional power plant.
Direct conversion of heat into electricity permit eliminate of
turbine & boiler.
Permit better fuel utilization.
