Thermoelectric waste heat recovery as a renewable energy source

TLDR: A thermoelectric converter is a solid-state heat engine in which the electron gas serves as the working fluid and converts a flow of heat into electricity as discussed by the authors, it has no moving components, is silent, totally scalable and extremely reliable.

Abstract: A thermoelectric converter is a solid-state heat engine in which the electron gas serves as the working fluid and converts a flow of heat into electricity. It has no moving components, is silent, totally scalable and extremely reliable. In the early 1960’s a requirement for autonomous long‐ life sources of electrical power arose from the exploration of space, advances in medical physics, deployment of marine and terrestrial surveillance systems and the exploitation of the earth’s resources in increasingly hostile and inaccessible locations. Thermoelectric devices employing radioactive isotopes as a heat source (Radioisotope Powered Thermoelectric Generators, referred to as RTGs) provided the required electrical power. Total reliability of this technology has been demonstrated in applications such as the Voyager space crafts with Voyager 1 passing into the Heliosheath some 8.3 billion miles from Earth on May 24th 2006. However, employing radioisotopes as sources of heat has remained restricted to specialised applications where the thermoelectric generator’s desirable properties listed above outweighed its relatively low conversion efficiency (typically 5%). The fivefold increase in the price of crude oil in 1974, accompanied by an increased awareness of environmental problems associated with global warming, resulted in an upsurge of scientific activity to identify and develop environmentally friendly sources of electrical power. Thermoelectric generation in applications, which employ waste heat as a heat source, is a totally green technology and when heat input is free, as with waste heat, the system’s generating power density is of greater importance than its conversion efficiency in determining the system’s economic viability. Over the past ten years or so effort has focused on developing thermoelectric generating systems which can recover waste heat from the human body, computer chips, automobile engines, and industrial utilities. In this paper the basic concepts of thermoelectric generation are outlined. An overview is presented of recent advances in the development of high performance thermoelectric materials, novel devices and applications, both macro and micro/nano. Finally, the potential of thermoelectric recovery of waste heat as a renewable energy source is assessed.