Figure of merit
• In recent years due to energy issues has brought in major interest to
the research of advanced technology perticularly in I.C engines.
• The growing rate of population indicates that the energy demand is
likely to increase substantial thermal energy available from exhaust
gas in modern automotive engines.
• Two-third of the energy from combustion in vehicle is lost as waste
• The 40 % lost energy is in the form of exhaust gas.
The pioneer in thermoelectrics was a German scientist Thomas Johann Seebeck
Thermoelectricity refers to a class of phenomena in which a temperature
difference creates an electric potential or an electric potential creates a
Thermoelectric power generator is a device that converts the heat energy
into electrical energy based on the principles of Seebeck effect.
Later, In 1834, French scientist, Peltier and in 1851, Thomson (later Lord
Kelvin) described the thermal effects on conductors.
S= dV / dT;
In 1821, Thomas
Seebeck found that
an electric current
continuously in a
closed circuit made
up of two dissimilar
metals, if the
junctions of the
maintained at two
S is the Seebeck
units of Volts per
S is positive when
the direction of
electric current is
same as the
When the junctions of two different metals are maintained
at different temperature, the emf is produced in the circuit
This is known as Seebeck effect.
The conductor 1 is maintained
at T+∆T temperature
The conductor 2 is maintained
at temperature T
Since the junctions are
maintained at different
temperature, the emf ‘U’
flows across the circuit.
The example for
• A high electrical conductivity is necessary to
minimize Joule heating and low thermal
conductivity helps to retain heat at the
junctions and maintain a large temperature
gradient. These three properties were later
put together and it is called figure-of-merit (Z).
• Figure of merit Z= α2 / k R
Figure of merit
• Environmental friendly
• Recycles wasted heat energy
• Scalability ,meaning that the device can be applied to
any size heat source from a water heater to a
• Reliable source of energy
• Lowers production cost
• Silent in operation
• They are simple , compact and safe
• They are not position dependent
Low energy conversion efficiency rate
Slow technology progression
Requires Relatively constant heat source
Lack of customer/industry education
about thermoelectric generators
The TEG is used to convert the waste heat
emitted from jet engine, IC engine, furnace,
heat water conveyor tubes.
For low power remote application. ( where
bulkier heat engines would not be possible)
On gas pipelines for CATHODIC protection
for example: global thermoelectric(CALGARA ,
CANADA) TELGEN (Russia)
Thermoelectric material have both
high electrical conductivity and low
The output voltage increases with
increase in temperature difference
Longitudinal model indicates
performance improvement of TEG
• Dipak Patil,Dr.R.R.Arakerimath,“A review of thermoelectric generator for waste
heat recovery from engine exhaust”,Int. Journal of research in aeronautical &
mechanical engineering,Vol.1Issue.8,Dec 2013.
• Saniya Leblanc,“Thermoelectric Generators: linking material properties and
systems engineering for waste heat recovery applications”,sustainable materials
and technologies 1-2(2014) 26-35.
• S.L.Nadaf,P.B.Gangavati,“A Review on waste heat recovery and utilization from
diesel engines”,Nadaf et al. Int. journal of advanced engineering technology E-
• Prathamesh Ramade,Prathamesh Patil,Manoj Shelar,Sameer Chaudhary, Prof.
Shivaji Yadav,Prof.Santosh Trimbake,“Automobile Exhaust thermo-electric
generator design& performance analysis”,Int. journal of Emerging technology
and advanced engineering,Vol.4,Issue5,may 2014.
• A.Jacks delightus Peter,Balaji.D,D.Gaurishankar,“waste heat energy harvesting
using thermoelectric generator”,IOSR Journal of engineering(IOSRJEN) vol-3