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If the load resistor at the bottom is replaced with a voltmeter, the circuit then functions as a temperature-sensing thermocouple. The Seebeck effect is the electromotive force (emf) that develops across two points of an electrically conducting material when there is a temperature difference between them. The emf is called the Seebeck emf (or ...
Therefore, the measured Seebeck coefficient is a contribution from the Seebeck coefficient of the material of interest and the material of the measurement electrodes. This arrangement of two materials is usually called a thermocouple. The measured Seebeck coefficient is then a contribution from both and can be written as:
The thermocouple's behaviour is captured by a characteristic function (), which needs only to be consulted at two arguments: = (). In terms of the Seebeck coefficients, the characteristic function is defined by
Thermoelectric generators function like heat engines, but are less bulky and have no moving parts. However, TEGs are typically more expensive and less efficient. [ 2 ] When the same principle is used in reverse to create a heat gradient from an electric current, it is called a thermoelectric (or Peltier) cooler .
Diagram of an RTG used on the Cassini probe. A radioisotope thermoelectric generator (RTG, RITEG), sometimes referred to as a radioisotope power system (RPS), is a type of nuclear battery that uses an array of thermocouples to convert the heat released by the decay of a suitable radioactive material into electricity by the Seebeck effect.
The efficiency of a thermoelectric device for electricity generation is given by , defined as =.. The maximum efficiency of a thermoelectric device is typically described in terms of its device figure of merit where the maximum device efficiency is approximately given by [7] = + ¯ + ¯ +, where is the fixed temperature at the hot junction, is the fixed temperature at the surface being cooled ...