The principle phenomenon that underpins thermoelectric energy generation is known as the Seebeck effect: the conversion of a temperature differential into electricity at the junction of two materials. The conversion process is reversible, i.e. when a thermoelectric generator is connected to a power supply it acts as a cooler/heater according to the underlying physical principle, the Peltier effect. The Peltier effect stipulates that electrical power input into a junction of two different materials leads to the creation of a temperature difference. For that reason, thermoelectric coolers are also known as Peltier coolers or Peltier modules (see figure 1).
Figure 1. Representation of the Peltier (left) and the Seebeck (right) effect. Source: University of Suffolk
Markets For Thermoelectric Generators
Wireless sensors powered by thermoelectric generators in environments where temperature differentials exist would lead to avoiding issues with battery lifetime and reliability and lead to an increase in wireless sensor network implementations. It would also lead to the ability to move away from wired sensors, which are still the solution of choice when increased reliability of measurement over prolonged periods of time is necessary. Some applications have low enough power demands to operate with small temperature differentials, as small as a few degrees in some cases. Some other segments on the other hand are characterized by extreme temperature differentials but at the same time, have very stringent safety requirements which could lead to long development times -e.g. condition monitoring of turbine blades while in-service. These varying kinds of considerations pertaining to different segments demonstrate the versatility that needs to be demonstrated by the technology developers in order to capture available opportunities in different verticals.
Waste heat recovery systems in vehicles
A large number of car companies, including Volkswagen, VOLVO, FORD and BMW in collaboration with NASA have been developing thermoelectric waste heat recovery systems in-house, each achieving different types of performance but all of them expecting to lead to improvements of 3-5%