This document provides an overview of magnetohydrodynamics (MHD) and MHD power generation. It discusses the history and development of MHD, how MHD generators work using ionized gas as a conductor in a magnetic field to generate electricity, types of MHD generators including open and closed cycle, advantages like no moving parts and higher efficiencies, and applications like power generation from heat sources. The document covers the basic principles, components, advantages, challenges, and future applications of MHD power generation.

2.  INTRODUCTION
 HISTORY
 INTRODUCTION
 PRINCIPLE
 CONSTRUCTION
 WORKING
 COMPONENTS
 TYPES
 ADVANTAGES
 DISADVANTAGES
 APPLICATIONS
 CONCLUSION

3.  Magneto hydro dynamics (MHD) (magneto fluid dynamics or hydro magnetics) is
the academic discipline which studies the dynamics of electrically conducting fluids.
Examples of such fluids include plasmas, liquid metals, and salt water.
 The word magneto hydro dynamics (MHD) is derived from magneto- meaning magnetic field,
and hydro- meaning liquid, and -dynamics meaning movement.
 This is a device that transforms thermal energy and kinetic energy into electricity.
 MHD power generation provides a way of generating electricity directly from a fast moving
stream of ionised gases at high temperatures without the need for any moving mechanical
parts - no turbines and no rotary generators
 In advanced countries MHD generators are widely used but in developing countries like
INDIA, it is still under construction, this construction work in in progress at TRICHI in
TAMIL NADU, under the joint efforts of BARC (Bhabha atomic research center), Associated
cement corporation (ACC) and Russian technologists.

4.  The field of MHD was initiated by Hannes Alfvén , for which he received the Nobel
Prize in Physics in 1970.
 Michael Faraday in 1832 carried out an experiment at the Waterloo Bridge in Great
Britain for measuring the current, from the flow of the river Thames in earth's
magnetic field.
 1920s and ’30s, Bela Karlovitz, a Hungarian-born engineer, first proposed a gaseous
MHD system
 In 1938 Bela Karlovitz and Hungarian engineer D. Halász set up an experimental
MHD facility at the Westinghouse Electric Corporation research laboratories and
by 1946 had shown that, through seeding the working gas, small amounts of electric
power could be extracted
 In 1959 the American engineer Richard J. Rosa operated the first truly successful
MHD generator, producing about 10 kilowatts of electric power.
 By 1963 the Avco Research Laboratory, under the direction of the American
physicist Arthur R. Kantrowitz, had constructed and operated a 33-megawatt MHD
generator

5.  MHD power generation process is governed by M.Faradays law of Electromagnetic
Induction. (i.e. when the conductor moves through a magnetic field, it generates an electric
field perpendicular to the magnetic field & direction of conductor). The flow of the conducting
plasma through a magnetic field at high velocity causes a voltage to be generated across the
electrodes, perpendicular to both the plasma flow and the magnetic field according to
Flemings Right Hand Rule .

6.  The Lorentz Force Law describes the effects of a charged particle moving in a constant
magnetic field. The simplest form of this law is given by the vector equation:
F = Q * ( v * B )
where
 F is the force acting on the particle.
 v is the velocity of the particle
 Q is the charge of the particle
 B is the magnetic field.

7.  MHD generator resembles the rocket engine surrounded by enormous magnet.
 It has no moving parts & the actual conductors are replaced by ionized gas (plasma)
 The magnets used can be electromagnets or superconducting magnets
 Superconducting magnets are used in the larger MHD generators to eliminate one of the large parasitic
losses.
 As shown in figure the electrodes are placed parallel & opposite to each other. It is made to operate at
very high temperature, without moving parts.
 Because of the high temperatures, the non- conducting walls of the channel must be constructed from an
exceedingly heat-resistant substance such as yttrium oxide or zirconium dioxide to retard oxidation.

8.  In conventional generator or alternator, the conductor consists of copper windings or strips while in an
MHD generator the hot ionized gas or conducting fluid replaces the solid conductor.
 A pressurized, electrically conducting fluid flows through a transverse magnetic channel walls field in a
channel or duct.
 Pair of electrodes are located on the at right angle to the magnetic field and connected through an external
circuit to deliver power to a load connected to it.
 Electrodes in the MHD generator perform the same function as brushes in a conventional DC generator.
The MHD generator develops DC power and the conversion to AC is done using an inverter.
 The MHD system constitutes a heat engine, involving an expansion of the gas from high to low pressure
in a manner similar to that employed in a conventional gas turbogenerator . In the turbogenerator, the gas
interacts with blade surfaces to drive the turbine and the attached electric generator.

9.  It is the generation of electric power utilizing the high temperature conducting plasma (stream of high
temp working fluid) moving through an intense magnetic field.
 It converts the heat energy of fuel (thermal energy) directly into electrical energy
 The fuel is burnt in the presence of compressed air in combustion chamber.
 During combustion seeding materials are added to increase the ionization & this ionized gas (plasma) is
made to expand through a nozzle into the generator.
 Magnetic field, a current is generated & it can be extracted by placing electrodes in a suitable stream. This
generated EMF is DC

10. Ionization of GAS:
 Various methods for ionizing the gas are available, all of which depend on imparting sufficient energy to
the gas.
 The ionization can be produced by thermal or nuclear means.
 Materials such as Potassium carbonate or Cesium are often added in small amounts, typically about 1%
of the total mass flow to increase the ionization and improve the conductivity, particularly combustion of
gas plasma.
 90% conductivity can be achieved with a fairly low degree of ionization of only about 1%.

11. WORKING FLUID:
 The Plasma:
 creating and managing the conducting gas plasma since the system depends on the plasma
having a high electrical conductivity.
 the fourth state of matter after the solid, liquid and gaseous states, in which the atoms or
molecules are stripped of their electrons leaving positively charged ions.
 Suitable working fluids are gases derived from combustion, noble gases, and alkali metal
vapours.
 The Gas Plasma:
 To achieve high conductivity, the gas must be ionised by detaching the electrons from the atoms
or molecules leaving the positively charged plasma.
 The plasma flows through the magnetic field at high speed, in some designs, more than the
speed of sound, the flow of the positively charged particles providing the moving electrical
conductor necessary for inducing a current in the external electrical circuit..
 Containment:
 Since the plasma temperature is typically over 1000 °C, the duct containing the plasma must be
constructed from non-conducting materials capable of withstanding these high temperatures
 The electrodes must of course be conducting as well as heat resistant

12.  Power Output:
 The output power is proportional to the cross sectional area and the flow rate of the ionised plasma
 Output of 30 MW-75 MW is known till date.
 An MHD generator produces a direct current output which needs an expensive high power
inverter to convert the output into alternating current for connection to the grid
 The power generated per unit length by MHD generator is approximately given by,
Where ,u is the fluid velocity, B is the magnetic flux density, σ is the electrical conductivity of
conducting fluid and P is the density of fluid.
 Efficiency:
 Typical efficiencies of MHD generators are around 20 to 30 percent mainly due to the heat lost
through the high temperature exhaust.
 Total plant efficiencies of 65% could be possible in combination with other energy plants.
 Like all heat engines, the thermal efficiency of an MHD converter is increased by supplying the
heat at the highest practical temperature and rejecting it at the lowest practical temperature.
 Experience:
 Demonstration plants with capacities of 50 MW or more have been built in several countries but
MHD generators are expensive
 Typical use could be in peak shaving applications but they are less efficient than combined-cycle
gas turbines which means there are very few installations and MHD is currently not considered
for mainstream commercial power generation.

13.  BASED ON CYCLE
 Open cycle MHD
 Closed cycle MHD
 Seeded inert gas system
 Liquid metal system

14. Temperature in OC MHD is about 2500oC
Working fluid-potassium seed combustion product.
DC Superconducting magnets of 4~6Tesla are used.
Here exhaust gases are left out to atmosphere & the capacity of these plants are
about 100MW.

16. •Working fluid-cesium seeded helium
•. Temperature of CC MHD plants is very less compared to OC MHD plants. It’s about 1400oC.
•DC Superconducting magnets of 4~6Tesla are used.
•Here exhaust gases are again recycled & the capacities of these plants are more than 200MW

20.  In MHD the thermal pollution of water is eliminated. (Clean Energy System) It contribute greatly to the
solution of serious air and thermal pollution faced by steam plants.
 Use of MHD plant operating in conjunction with a gas turbine power plant might not require to reject any
heat to cooling water.
 These are less complicated than the conventional generators, having simple technology.
 There are no moving parts in generator which reduces the energy loss.
 These plants have the potential to raise the conversion efficiency up to 55-60%. Since conductivity of
plasma is very high (can be treated as infinity).
 It is applicable with all kind of heat source like nuclear, thermal, thermonuclear plants etc.
 Extensive use of MHD can help in better fuel utilization.
 Direct conversion of heat into electricity permits to eliminate the turbine (compared with a gas
turbine power plant) or both the boiler and the turbine (compared with a steam power plant)
elimination reduces losses of energy.

21.  The construction of superconducting magnets for small MHD plants of more than 1kW electrical capacity
is only on the drawing board.
 Difficulties may arise from the exposure of metal surface to the intense heat of the generator and form the
corrosion of metals and electrodes.
 Construction of generator is uneconomical due to its high cost.
 Construction of Heat resistant and non conducting ducts of generator & large superconducting magnets is
difficult.
 MHD without superconducting magnets is less efficient when compared with combined gas cycle
turbine.

22.  Power generation in space craft.
 Hypersonic wind tunnel experiments.
 Defense application

23.  Improvement in corrosion science & superconducting magnets can make rapid
commercialization possible.
 Saving billions of dollars towards fuel prospects of much better fuel utilization.
 It can therefore be claimed that the development of MHD for electric utility power generation
is an objective of national significance.
 The practical efficiency of this type of power generation will not be less than 60%. Hence it
will be most significant in upcoming decade

24. REFERENCES
 Journel of Yoshihiro OKUNO Department of Energy
Sciences Tokyo Institute of Technology
 http://www.britannica.com/technology/magnetohydr
odynamic-power-generator
 https://en.wikipedia.org/wiki/Magnetohydrodynamic
_generator