Analysis of a symbiotic thermoelectric system for power generation and liquid preheating

Thermoelectrics have long been recognized as a unique energy conversion technology due to their capability to convert heat directly into electricity having no moving parts. Despite this potential, except for specialised situations, thermoelectric devices have limited applications because of their low efficiency. Generally they exhibit low conversion efficiency because of the relatively small figure-of-merit (ZT) of currently available thermoelectric materials. Many efforts have been made over recent years on improving thermoelectric conversion efficiency by increasing ZT, with only marginal success. In this research an alternative solution was provided to overcome the main drawback of thermoelectric devices. The idea is to operate the thermoelectric generator in a combined heat and power generation mode. This configuration consists of a stacked assembly of several thermoelectric modules sandwiched between three rectangular cold and hot liquid passages appropriately connected to an ordinary liquid (e.g. water) heater. It is shown that the combined system can produce heat and electricity with nearly zero heat dissipation to the surroundings by re-using rejected heat from thermoelectric modules for inlet liquid preheating.