The document discusses direct energy conversion principles, focusing on thermoelectric generators and related effects such as the Seebeck, Peltier, and Thomson effects. It explains how temperature differences can create electric potential and vice versa, as well as the construction and functioning of thermoelectric devices. Basic thermocouple configurations and laws are also briefly described, emphasizing their role in thermoelectric applications.

1. Unit-2 Direct Energy Conversion Principles and Types
Thermo Electric Generators
• Seeback effect
• Peltier effect
• Thomson effect
• Thermoelectric convertors
• Brief description of the construction of thermoelectric generator

2. 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 an electric potential creates a temperature
difference.
• 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

3. Thermo electric Generator
• 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 an electric potential creates a temperature
difference.
• 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

4. Seebeck Effect

5. Concept of Contact Potential

6. 6
Seebeck Effect Application : Thermocouples

7. 7
Basic Thermocouple Junction Types

8. 8
Thermocouple configuration

9. Thermocouple Types

10. 10
Thermocouple Laws

11. 11

12. 12

13. 13

14. 14

15. 15

16. Thermo Electric Generator
(Simple Arrangement)

17. Thermocouple connected in series to
increase voltage

18. General Schematic of Thermoelectric Converter

19. Peltier Effect
• When an electric current flows across an isothermal junction of two
dissimilar materials, there is evolution or absorption of heat at the
junction
• Its a reversible effect
• If heat is evolved when the current flows in on direction, the same amount of
heat is absorbed at the junction if the current is also reversed

20. Peltier Effect
• α1-2 : Peltier coefficient
• Defined as: Heat evolved or absorbed at the junction per unit curret flow,
per unit time

21. Thomson Effect
• When an electric current flows through a material having a temperature gradient,
there is evolution or absorption of heat
• Its a reversible process
• Reversing the direction of current flow reverses the direction of heat transfer without change
is magnitude

22. Thomson Effect
• When an electric current flows through a material having a temperature gradient,
there is evolution or absorption of heat
• Its a reversible process
• Reversing the direction of current flow reverses the direction of heat transfer without change
is magnitude

23. Thomson Effect
• σ : Thomson coefficient
• Defined as: Heat evolved or absorbed at the junction per unit time time
per unit current and per unit temperature gradient
dx
d
dx
d
T
qT


gradient
e
temperatur
dx
d
condcutor
of
length
unit
per
unit time
per
e
interchang
heat
where
T



dx
d
dx
dT
I
dx
d
qT
qT 

24. Summary
dx
dT
I
dx
dqT 


25. General Schematic of Thermoelectric Converter