4. Implementation in thermoelectric devices
The conventional design for thermoelectric devices consists of a pair of thermo electric materials–one p-type and one n-type. As shown in Fig. 12a, the two materials are electrically connected at one end, which will be the positive voltage for one material and negative for the other, such that the voltage difference at the other end of the module is the sum of the two thermovoltages. The modules can be connected in series as shown in Fig. 12a to increase the voltage. An alternative design shown in Fig. 12b and referred to as a unileg module uses only one type of thermoelectric material (either p-type or n-type).174 The voltage generated by each module in the unileg design is smaller, but the metal conductor between the hot and cold ends of the module may occupy less space than the thermoelectric element. The size of the metal conductor must be kept small to minimize the amount of heat transferred between the hot and cold ends of the module. The unileg design requires only one type of thermoelectric material, which may reduce some design restrictions.