Thermovoltaics

from Wikipedia, the free encyclopedia

The Thermovoltaik is the working area of physics that deals with the direct conversion of heat energy into electrical energy is concerned.

If two different metals or semiconductors are contacted with one another, a thermoelectric potential difference usually arises depending on their position in the thermoelectric series of voltages . At the other end of the pairing, an electrical voltage can be measured if the contact point and the measuring point have different temperatures ( thermocouple ). This low thermal voltage (a few µV / K temperature difference) is associated with a relatively high current in the event of a load or short circuit , if / because the current path has a corresponding cross-section or electrical resistance. In this way, applications were found that go beyond mere temperature measurement.

While the electrical open circuit voltage (thermal force) is approximately proportional to the temperature difference, the electrical current in the event of a short circuit of a thermocouple is determined not only by the temperature difference but also by the conductor cross-section. Even with the most suitable pairings, the heat conduction along the temperature difference is only taken over to a small extent by the electric current. Therefore, with thermal generators, the usable electrical power increases approximately with the square of the heat flow or the heat output. Current and voltage, on the other hand, are roughly proportional to the heat flow.

Possible uses

  • Thermogenerator: it usually consists of an electrical series connection of suitable thermocouples, which lie in parallel in the heat flow. In this way, the generated voltage sum reaches practically usable values ​​in the volt range. The absolute temperature of the hot side is limited to about 120 ° C by the material.
  • Ignition safety device (safety element in gas burners): the current generated by the heat of the gas flame in a thermocouple keeps a solenoid valve open with a few millivolts but high current.
  • Temperature measurement: standardized thermocouples are available that are suitable for maximum temperatures of 450 to around 1800 ° C. Typical thermal voltages are 5… 40 µV / K temperature difference, precise information can be found from the manufacturers.
  • Heat flow measurement / thermopile / bolometer : Temperature differences generate a voltage on thermocouple arrangements that is a measure of the heat transfer or (in the case of infrared radiation absorption ) the radiation power or power flux density. Use in building physics and for beam power measurement.

See also

Individual evidence

  1. ↑ Thermovoltaics - new generation of thermoelectric generators. In: www.science-at-home.de. Retrieved August 15, 2016 .
  2. ↑ Thermovoltaics: conversion of heat into solar power. Retrieved August 15, 2016 .
  3. ↑ Thermovoltaics: conversion of heat into solar power. Retrieved August 15, 2016 .