The invention relates to a thermoelectrical arrangement with improved efficiency for the purpose of converting heat into electrical energy and for the purpose of reversible electrical pumping of heat.
As is known, thermocouple elements as electrical generators for converting heat only reach efficiencies of a few percent. In addition, thermocouple elements have until today only been competitive as electrical heat pumps in very specific applications. This is chiefly because combining thermal and electrical properties of material, which limits the maximum efficiency possible of thermocouple elements, is still too bad in all the thermocouples available today. Even with the best thermoelectrical materials, which we know today (say doped Si.sub.70 Ge.sub.30 crystals for generators or Bi.sub.2 Te.sub.3 for heat pumps), the so-called "efficiency" (the quotient of the square of the thermoelectrical force divided by the ratio of thermal and electrical conductivity) only reaches the numerical value 1 when multiplied by the average operating temperature. This is the main reason for the fact that, at best, 10 to 20% of the Carnot efficiency may be reached with thermocouple elements. A very substantial increase in the efficiency would be necessary for the thermoelectrical effects to be used in large-scale technology.
A substantial increase in the thermoelectrical efficiency would scarcely be achieved by an improvement of known thermoelectrical materials given the present state of the art. Greater success is promised by exploiting and cultivating new physical effects in thermoelectrical arrangements.
New physical effects, either by means of an increase in the electrical conductivity or an increase in the thermoelectrical force or a reduction in the heat conductivity of thermoelectrical materials, could contribute to an increase in efficiency. An increase in the electrical conductivity is possible for example in very thin semiconductor and insulating layers by means of the tunnel effect relating to wave mechanics. An increase in the thermoelectrical force may take place as a result of electrons being "pulled along" by phonons in temperature gradients under special conditions (phone-drag effect), and a reduction in the thermal conductivity takes place with inelastic scattering of electrons at the lattice.