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THERMOELECTRIC GENERATOR

TARKESHWAR GUPTA(100106357)

TARUN RAJ SINGH(100106357)

UTTKARSH ABHISHU(100106357)

VIPUL KHANDELWAL(100106357)


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AJENDA Introduction

Seebeck effect, Peltier effect and Thomson effect

Thermoelectric effect

Thermoelectric materials

Principle, construction and working of Thermoelectricgenerator


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INTRODUCTION The pioneer in Thermoelectrics was a German scientist

Thomas Johann Seebeck (1770-1831). Thermoelectricity refers to a class of phenomena in which a

temperature difference creates an electric potential or anelectric potential creates a temperature difference.

Thermoelectric power generator is a device that converts theheat energy into electrical energy based on the principles ofSeebeck effect.

Later, In 1834, French scientist, Peltier and in 1851, Thomson (later Lord Kelvin) described the thermal effects on conductors.


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SEEBECK EFFECT When the junctions of two different metals are

maintained at different temperature, the emf isproduced in the circuit. This is known as Seebeck

effect.The conductor 1 is maintained at T+ T temperature

The conductor 2 is maintained attemperature T .

Since the junctions are maintained atdifferent temperature, the emf

U

flowsacross the circuit.


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PELTIER EFFECTWhenever current passes through the circuit of two dissimilarconductors, depending on the current direction, either heat isabsorbed or released at the junction of the two conductors. This isknown as Peltier effect.

released

absorbed


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THOMSON EFFECTHeat is absorbed or produced when current flows in material witha certain temperature gradient. The heat is proportional to boththe electric current and the temperature gradient. This is knownas Thomson effect.

Thermoelectric effect

The thermoelectric effect, is the direct conversion of heatdifferentials to electric voltage and vice versa. .


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THERMOELECTRIC M TERI LS

The good thermoelectric materials should possess

1. Large Seebeck coefficients2. High electrical conductivity3. Low thermal conductivity

The example for thermoelectric materials

BismuthTelluride (Bi 2Te 3), Lead Telluride (PbTe), SiliconGermanium (SiGe), Bismuth-Antimony (Bi-Sb)


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PRINCIPLE THERMOELECTRIC

POWER GENER TOR

Thermoelectric power generator based on the principle ofSeebeck effect that when the junctions of two different metals aremaintained at different temperature, the emf is produced in thecircuit Heat input

Hot junction

Cold junction

P-type N-type

Heat ejectionPower output


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In order to select materials and design a thermoelectricgenerator, one needs to start with a general understanding ofthe thermoelectric effects.

In a thermoelectric material there are free carriers which carryboth charge and heat.

Perhaps the simplest example is a gas of charged particles. If a gas is placed in a box within a temperature gradient, where

one side is cold and the other is hot, the gas molecules at thehot end will move faster than those at the cold end.

The faster hot molecules will diffuse further than the coldmolecules and so there will be a net build up of molecules

(higher density) at the cold end. The density gradient will cause the molecules to diffuse

back to the hot end.


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CONSTRUCTION Thermoelectric power generation (TEG) devices typically use

special semiconductor materials, which are optimized for theSeebeck effect.

The simplest thermoelectric power generator consists of athermocouple, acomprising a p-type and n-type materialconnected electrically in series and thermally in parallel.

Heat is applied into one side of the couple and rejected fromthe opposite side.

An electrical current is produced, proportional to thetemperature gradient between the hot and cold junctions


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Heat source (fuel) P and N type semiconductor stack (TE module) Heat sink (cold side) Electrical load (output voltage)

Therefore, for any TEPG, there are four basic component required

such as


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The figure shows the construction of thermoelectric powergenerator.

There is a burner in which the propane fuel is used as heatingsource in one side.

The exhaust is used to transmit a burnt fuel.

On the other side, a cold junction is kept.

The thermoelectric module (TE) (consist of number of P-type

and N-type semiconductor pellets connected in series orparallel depending on the served load)) is kept in between thehot and cold junction.

The electrical out (load) is taken from the TE module.


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WORKING When the two sides of semiconductor are maintained with

different temperature, the emf is flows across the output circuit.

N-type

V

Cold side Hot side

Heat flow

Electron flow


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As the heat moves from hot side to cold side, thecharge carrier moves in the semiconductor materials andhence the potential deference is created.

The electrons are the charge carriers in the case of N- type semiconductor and Hole are in P-type

semiconductors.

In a stack, number of P-type and N-type semiconductorsis connected.

A single PN connection can produce a Seebeck voltageof 40 mV.

The heat source such as natural gas or propane areused for remote power generation


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DV NT GES Easy maintenance: They works electrically without any

moving parts so they are virtually maintenance free.

Environment friendly: Thermoelectric generators produce

no pollution. Therefore they are eco friendly generators.

Compact and less weight: The overall thermoelectriccooling system is much smaller and lighter than acomparable mechanical system.

High Reliability: Thermoelectric modules exhibit veryhigh reliability due to their solid-state construction

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