Transcript TEP(Thermoelectroic Power)

Thermoelectric Power (TEP)
Introduction
The thermoelectricity was discovered in 1821 by Thomas Seebeck
where a continuously flowing current was created when two wires
of different materials were joined together and heated at one end.
This is known as the Seebeck effect (Fig.1). The Seebeck effect has
two main applications i.e. temperature measurement and power
generation. Seebeck circuit also creates the refrigeration. This is
known as Peltier effect. When current passes from material A to
material B, the junction becomes either cooled or heated (Fig.2).
This forms the basis of the thermoelectric Power.
Fig.1
Principle
Thermoelectric modules can also be used as thermocouples for
measuring temperature or providing the temperature- sensing
element in a thermostat. When one end is heated a current will
flow continuously. Then the current ceases and voltage is
measured by a voltmeter (Fig.3). The voltage generated is a
function of the temperature difference and the materials of the
two wires used. Two wires used to measure temperature in this
manner form a thermocouple.We define the Seebeck coefficient as

V
S  lim
T   0
Fig.2
T
Where ΔV:differential voltage between the two ends of the sample
ΔT:temperature difference between the two ends
Fig.3
Instrument
Figure 4. shows the schematic diagram of our
instrument. The sample is on the sample space
inside the OXFORD Chamber. We accurately
measure ΔV and ΔT from two Nanovoltmeters,
pass the current to heater for transport of
thermal energy to the sample. In temperature
controller, we fix the needle value by ITC503
and cooling the sample by water refrigerating
compresser system which provides closed
circuit helium gas compression. We use
software (LABVIEW) to operate all the
Systems.The TEP of Pb is
Shown in Fig.5.
S measure  S Cu  S sample
S Cu
2.0
1.5
s(V/K)
1.0
0.5
S Measure
0.0
-0.5
Fig.4
-1.0
-1.5
0
20
40
60
80 100 120 140 160 180 200 220 240 260 280 300 320
T(K)
Fig.5