Sri Ramakrishna College of Arts & Science, Coimbatore, Department of Physics

1. MAGNETO HYDRA
DYNAMIC POWER
GENERATION

2. INTRODUCTION
• The production of electrical power utilizing conducting fluid through an intense
magnetic field.
• Fluid may be gas or liquid metal.
• A Direct Energy Conversion system.
• Classified based on the nature of processing of the working fluid.
• Plays an important role in power industry.
• Magneto Hydrodynamic (MHD) system is a non- conventional source of energy which
is based upon Faraday’s Law of Electromagnetic Induction, which states that energy is
generated due to the movement of an electric conductor inside a magnetic field.

3. MAGNETOHYDRODYNAMIC
ESSENTIALS
• Magnetic Field.
• Perpendicular Current.
• Magnetic Fluid
•Magnetic metals
. •Plasmas
•Salt water
• The idea of MHD is that magnetic fields can induce currents in a
moving conductive fluid, which create forces on the fluid. The set of
equations which describe MHD are a combination of the Navier-
Stokes equations dynamics of and Maxwell’s equations of
electromagnetism.

4. PRINCIPLE OF OPERATION
• The operation is based on the
simple principles of Lorentz
Force Law.
• F = q(v×B)
• V=Velocity of the particle
(vectors).
• Q=charge of the particle
(scalar).
• B=magnetic field (vector).

5. • Lorentz Force on the charged particle (vector).
• F = q(v×B)
Where,
v = velocity of the particle (vector)
q = charge of the particle (scalar)
B = magnetic field (vector)

6. PRINCIPEL OF MHD POWER
GENERATION
• Faraday’s law of electromagnetic induction: When an electric conductor moves across a magnetic field, an
emf is induced in it. Which produces an electric current.
• In accordance with Faradays law of induction, an electric field established that acts in a direction perpendicular to both the
gas flow and the magnetic field.

7. • Concept given by Michael Faraday in 1832 for the first time.
• MHD System widely used in advanced countries.
• Under construction in INDIA.

8. STRUCTURAL DIFFERENCES BETWEEN
TURBO GENERATOR AND MHD
GENERATOR

9. TYPES OF MHD GENERATORS
1. Open Cycle MHD Generators.
2. Closed Cycle MHD Generator.
a)Seeded inert gas systems .
b) Liquid metal systems.
• An adequate value of electrical conductivity-10 to 50 Siemens per metro-can be achieved if
an additive, typically about 1 percent by mass, is injected into the hot gas.
• This additive is a readily ionizable alkali material. Such as cesium. Potassium carbonate, or
sodium. And is referred to as the “seed.”

10. OPEN CYCLE SYSTEM
1. Working fluid is discharged to atmosphere.

11. HYBRID MHD STEAM PART
OPENCYCLE (binary cycle)

12. • The hot gas is first passed through the MHD generator (a process known as
topping) and then on to the turbo generator of a conventional steam plant
(the bottoming phase).
• An MHD power plant employing such an arrangement is known as an open-
cycle, or once-through, system.
• Use of a seed material with coal offers environmental benefits.
• In the duct the formation of potassium sulfate in the combustion of high-
sulfur coals, thereby reducing sulfur dioxide emissions to the atmosphere.
• The need to recover seed material also ensures that a high level of particulate
removal is built into an MHD coal-fired plant
• .By careful design of the boiler and the combustion controls, low levels of
nitrogen oxide emissions can be achieved.

13. THANK YOU

14. MAGNETO HYDRA DYNAMIC POWER
GENERATION

15. CLOSED CYCLE MHD
SYSTEM

16. Seeded Inert Gas MHD Generator
● In this type of closed system, the electrical conductivity is maintained in
the working fluid by ionization of the seed material. The heat from the
combustion chamber is used to convert working fluid,into ionized gas
(argon or helium), which can be seeded with cesium and circulated in
closed loop. This system has three distinct but interlocking loops.
● External heating loop: entails gasification of the fossil fuel.The released
gases are burnt in the combustion chamber and channeled into the first
heat exchanger where they are converted into carrier gas (argon or
helium).
● Centre loop: comprises the hot plasma (argon or helium gases) seeded
with cesium, passed through the MHD generator and second heat
exchanger, recycle into the first heat exchanger.
● Steam loop:which is used for further recovery of the heat of the working
fluid. Hot fluid from the MHD is channeled into the heat exchanger and
converted into steam, which is utilized for driving a turbine for generating
electricity and for driving a turbine runs the plasma compressor

17. LIQUID METAL MHD SYSTEM
● Liquid potassium is heated in the nuclear reactor is
passed through the nozzles.
● Small amount of vapour formed during the nozzle
passage is separated in the separator and it is
pumped back into the reactor.
● High velocity liquid metal is passed through the MHD
duct to produce D. C. power.
● Comparatively lower temperature liquid potassium is
then passed through a heat exchanger (steam
generator) before pumped to the reactor. It transfers
heat to feed water which is converted into steam.

18. MHD DESIGN PROBLEMS AND
DEVELOPMENT
● Short life of equipments
● Low efficiency
● The combustor, MHD-generator channel, electrodes, and preheater are
exposed to corrosive combustion gases at very high temperatures
● Materials must be developed to permit an adequate operating life for the
components.
● The ash residue from burning coal is carried over with the combustion gases
and it causes erosion of exposed surfaces.
● However, deposition of the slag in such surfaces may provide some
protection.

19. MHD DESIGN PROBLEMS AND
DEVELOPMENTS
● Another problem is seperation of the seed material (as potassium
sulfate) from the fly ash reconversion into its original form.
● The difficulties associated with slag and seed recovery can be
eliminated by using a fuel gas derived from coal rather than coal.
● An ash free low heat value gas, made from coal at a moderate cost
and treated for sulfur removal would make a suitable fuel for an
MHD conversion combustion
● A more advanced concept is to use hydrogen gas made from coal
and water ,when it is burned in compressed oxygen the product
would be high temperature steam

20. ADVANTAGES
(1)The conversion efficiency of an MHD system can be around 60 per cent as
compared to less than 40 per cent for the most efficient steam plants. Still
higher thermal efficiencies (60-65%) are expected in future, with the
improvements in experience and technology.
(2) Large amount of power is generated.
(3) It has no moving parts, so more reliable.
(4) The closed cycle system produces power free of pollution.
(5) It has ability to reach the full power level as soon as started.

21. ADVANTAGES
(6) The size of the plant (m/kW) in considerably smaller than onventional
fossil fuel plants.
(7) Although the costs can not be predicted very accurately, yet
has been reported that capital costs of MHD plants will be competitive with
those of conventional steam plants.
(8) It has been estimated that the overall operational, costs in MHD plant
would be about 20% less than in conventional steam plants

22. ADVANTAGES
(9) Direct conversion of heat into electricity permits to
eliminate boiler and the turbine (compared with a steam
power plant). This sasination reduces losses of energy fed
consumption would offer additional economic and special
benefits
(10) These systems permit better fuel utilization. The
reduced sad would also lead to conservation of energy
resources.
(11) It is possible to utilize MHD for peak power generations
and ergency service (upto 100 hours per year). It has been
estimated the MHD equipment for such duties is simpler, has
the capability of parating in large units and has the ability to

24. PRINCIPLES OF THERMOELECTRIC POWER GENERATOR
• Discovered by German scientist seebeck
• When a loop of two dissimilar materials were kept at different temperatures they
developed an emf.
• Example: ceramic type material made of semiconductors which are doped( Mn,
Fe, Co, Ni treated with O, S, Se, Te .)

25. • TEG is a device which converts heat energy into electrical energy.
• Works based on seebeck effect.
• Magnitude of the current depends on temperature difference of the junction.
• The Thermo Emf, V =α𝑠1−2 ∆T
(or) T2- temperature of hot junction
T1- cold junction
V = 𝑇1
𝑇2
𝛼 𝑠1−2 dT
Where α𝑠1−2 is the seebeck coefficient(depends on temperature in most cases)

26. • Seebeck coefficient is the temperature coefficient of thermo emf or the rate if change of
thermo-emf with temperature. Depends upon the material.
• Seebeck effect arise because of concentration of the charge carriers in a conductor
depends upon the temperature.
• Presence of a temperature gradient in a material causes a carrier concentration gradient
and an electric field is created(from low to high). Choosing two dissimilar materials allows
us to add up potential difference so that a current flows through the circuit.

27. • The Thermodynamic conversion of heat to work involves 4 distinct processes
1) Peltier Effect(Reversible)
2)Thomson Effect(Reversible)
3)Joule Effect(Irreversible)
4)Fourier Effect(Irreversible)
• Joule Effect
Joule Effect refers to the irreversible conversion of electrical energy into heat when a
current I flows through a resistance R, an amount of heat equal to 𝐼2
𝑅 is generated per
unit time. This heat is called joulean heat
𝑄𝑗 = 𝐼2𝑅

28. • Peltier Effect
When a current flows across an isothermal junction of two dissimilar materials, there
is either an evolution or absorption of heat at the junction. This effect is called the peltier
effect. If heat is evolved when current flows in one direction, the same amount of heat is
absorbed at the junction if the current flow is reversed. So the process is reversible.
𝛼𝑝1−2 =
𝑞𝑝
𝐼
𝛼𝑝1−2 - Peltier Coefficient
q – heat evolved or absorbed
I – Peltier heat per unit time
• Thomson Effect
When an electric current flows through a material having a temperature gradient, there
is an evolution of heat and this phenomenon is called the Thomson effect. Reversing the
direction of current flow reverses direction of heat transfer without change in magnitude.

29. 𝜎 =
ⅆ𝑞𝑡
ⅆ𝑥
ⅆ𝑇
ⅆ𝑥
𝜎 – Thomson Coefficient
ⅆ𝑞𝑡
ⅆ𝑥
- heat interchange per unit time per unit length
ⅆ𝑇
ⅆ𝑥
- temperature gradient

30. THERMOELECTRIC POWER GENERATOR
• Thermocouple materials A & B
• Direct current will flow when there is a temperature difference.
• The voltage and power output can be increased by increasing the temperature
difference between hot and cold ends, Connecting several thermocouple in series.

31. 𝑃 =
𝛼𝑆𝐴𝐵𝛥𝑇
𝑅 + 𝑅𝐿
2
⋅ 𝑅𝐿
Power fed into the external load
Where, 𝛼𝑆𝐴𝐵𝛥𝑇 – emf , R – total resistance, RL- external load resistance
𝛼𝑆𝐴𝐵𝛥𝑇
𝑅+𝑅𝐿
- current

32. • An index used in rating thermoelectric converters is called the figure of merit,
Z,
𝑧 =
𝛼𝑠𝐴−𝛼𝑠𝐵
𝜌𝐴𝐾𝐴
− 𝜌𝐵𝑘𝐵
2
• Ideal Efficiency of the thermoelectric converter
𝜂 =
𝑇𝐻 − 𝑇𝐶
𝑇𝐻
𝑚 − 1
𝑚+𝑇𝐶
𝑇𝐻

33. THERMOELECTRIC MATERIALS
• Examples: Lead telluride(Pb Te), Bismuth telluride(Bi2 Te3), Bismuth sulfide(Bi2 S3), Antimony
telluride(Sb2 Te3), Tin telluride(Sn Te), Indium arsenide, Germanium telluride(Ge Te)
• Materials with higher α𝑠 values are great Thermocouples.
• Selection of Materials
1. The Thermal conductivity of the material should be as low as possible. (low debye temp.
and heavy molecules weekly bounded)
2. The mobility of current carriers(holes or electrons) should be high.
3. One side should consist purely of holes and the other purely of electron type
semiconductors.( material with low ionization energy)
4. The thermoelements should have variable impurity content.
5. Stability to chemical influences(oxidation), good mechanical strength and elasticity.