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Non-conventional Power Generation
Introduction:
The whole world is already familiar with the conventional power generating resources like hydal, thermal
and nuclear resources etc
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The non-conventional sources may be renewable or non-renewable
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In all the conventional
systems the potential or thermal energy is first converted into mechanical energy and then this
mechanical energy is converted into electrical energy
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e
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e
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This requires huge capital cost as well as maintenance cost
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Research is now focusing its efforts on conversion process that do not involve mechanical energy
conversion step
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These processes are known as direct conversion systems in which primary or secondary
energy is directly converted into electrical energy without passing through the stage of mechanical
energy
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The possibility of using new sources of energy seems
enhanced by the development of new direct energy converters
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Direct Energy Conversion Stages

MHD Power Generation:
The Magnetohydrodynamics (MHD) power generation is a direct energy conversion system which
converts the heat energy directly into electrical energy
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As the name implies MHD
generator is concerned with the flow of a conducting fluid in the presence of magnetic and electric fields
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A pressurized electrically
conducting fluid flows through a transverse magnetic field in a channel or duct
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Electrodes in MHD generator perform
the same function as brushes in a conventional dc generator
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Basic principle
According to the Faradays Law of Electro Magnetic Induction “An electric conductor moving through a
magnetic field experiences a retarding force as well as an induced electric field and current
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(𝟏𝟏)

The power generated per unit length by MHD generator is

Where u is the fluid velocity, B is the magnetic flux density,
the density of fluid
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Ionization is produced either by thermal means i
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by
an elevated temperature or by seeding with substance
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The injected material is termed seed material
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Only small amount of seed material is required and is
typically 1% of the total mass flow
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In MHD duct the K
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To accommodate the flow a due to a
reduction in velocity along the length of duct, the duct is made of diffuser
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The thermal energy of the hot fluid leaving the MHD
duct is further utilized in a heat power cycle
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1
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Closed Cycle MHD Power System
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Seeded Insert Gas System

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Liquid Metal System

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Open Cycle MHD Power System:
In an open cycle MHD power system air is used as fluid for the MHD duct
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The air is preheated so that high temperature is possible in combustion chamber
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The
temperature of preheated in between 2300 to 2700C either by directly burning pulverized coal in
combustor or in a separate heat exchanger
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The pressurized hot air from combustion chamber is passed through the nozzle and the seed material is
injected before the gas enters the MHD duct
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E and internal energy of the conducting gas
is converted in electricity
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This high temperature exhaust gas from the MHD duct is then used by in preheating of compressed air
which is to be heated in the combustion chamber
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Before leaving the exhaust gas into atmosphere, the
seed material is recovered in an electrostatic precipitator (ESP) which can be used again in MHD duct
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Closed Cycle MHD Power System:
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Seeded Insert Gas System

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Liquid Metal System

In closed cycle operation, noble gases and liquid metal are considered as fluid
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A high temperature
nuclear reactor probably helium cooled is also a feasible source for MHD and in the early stages of
development
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Difference between Open and Closed Cycle MHD Power Generation:

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Thermoelectric Power Generation:
The term thermoelectric is combination of two words thermo and electric and as its name indicates
thermal means heat energy and electric means electrical energy
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This is also a type of direct power conversion
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It converts heat energy directly into
electrical energy
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A thermoelectrical generator basically consists of heat source (hot junction), which is kept at high temperature and
a heat sink (cold junction), which is maintained at a temperature less than the heat source
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The power generated due to Seebeck power generation is single phase DC and given by I2R L or VI
where R L is the load resistance
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The
current will continue to flow as long as heat is supplied to the hot junction and removed from the cold
junction
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A typical thermoelectric
generator operating at hot and cold junction temperatures of 600C and 200C can develop 0
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This current produced by thermoelectric or Seebeck power generation is DC in nature and can be
converted into ac by using invertors and its voltage level can be further step up by using transformers
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e the
direction of energy flow can be reversed
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The voltage of this generator is given by V = α ΔT where α is Seebeck coefficient and ΔT is the
temperature difference between hot and cold junction
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Materials Suitable for Thermoelectric Power Generators:
The most commonly used material for this generator is lead telluride
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Other compounds used for making
thermoelectric power generators are bismuth telluride, bismuth sulphide, germanium telluride, zinc
antimonite, tin telluride and indium arsenide etc
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These generator
use heat produced when the vehicle is running
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These generators are used to supply power to remote stations like weather stations, relay
stations etc

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