Thermo-electrical engineering

Abstract

The engineer's interest in thermo-electric phenomena has in the past been mainly confined to devices, based on the Seebeck effect, for the measurement of temperature and r.f. power and radiation by means of thermocouples or thermopiles constructed from metals. Even with the best combination of metals available the use of the Seebeck effect for generation is barely feasible, and the use of the Peltier effect for refrigeration is quite impracticable.The success of germanium and silicon in the production of transistors and junction rectifiers has encouraged the study of the mechanism of electrical and thermal transport in semiconductors. Thus, it has been possible to select potentially efficient thermo-electric alloys and compounds from the vast range of semiconductors available.In the case of bismuth telluride a high figure-of-merit material has been obtained which makes refrigeration of small volumes a practical proposition. A generator efficiency approaching 5% is possible with bismuth telluride in the case where the ideal efficiency would not exceed 25% with temperature limits of 300–400° K.Many people1 elsewhere have recorded the search for thermo-electric materials and the optimization of their thermo-electric properties. The object here is to explain simply the basic principles of generators and cooling units in a quantitative manner. The salient features which emerge indicate the potentialities of bismuth telluride for the generation of power and heat pumping, in particular refrigeration of small volumes and local cooling.The paper is based on work carried out by the author on the engineering applications of bismuth telluride.