Cascading of Peltier Couples for Thermoelectric Cooling

The cooling of a single thermoelectric junction is limited to a certain temperature difference by the inherent properties of the elements used. Altenkirch gave a theoretical treatment of the single couple and showed a way to overcome the limitation on cooling by using a number of thermocouples in thermal cascade. Such an arrangement was constructed by Turrettini and shown to work. A simplified form of Altenkirch's theory is presented and a form of cascade which is simpler and more efficient than that of Turettini is described and experimental results are given. A two-stage cascade of elements limited to 11°C cooling as a single couple reached 15°C cooling while rather heavily loaded by lack of adequate thermal insulation. A good agreement with theory is obtained for the behavior of this cascade. It is shown that such a cascade is in theory more efficient than a single couple under all circumstances.