Thermal Management Systems and Waste Heat Recycling by Thermoelectric Generators—An Overview

Abstract

With the fast evolution in greenhouse gas (GHG) emissions (e.g., CO2, N2O) caused by fossil fuel combustion and global warming, climate change has been identified as a critical threat to the sustainable development of human society, public health, and the environment. To reduce GHG emissions, besides minimizing waste heat production at the source, an integrated approach should be adopted for waste heat management, namely, waste heat collection and recycling. One solution to enable waste heat capture and conversion into useful energy forms (e.g., electricity) is employing solid-state energy converters, such as thermoelectric generators (TEGs). The simplicity of thermoelectric generators enables them to be applied in various industries, specifically those that generate heat as the primary waste product at a temperature of several hundred degrees. Nevertheless, thermoelectric generators can be used over a broad range of temperatures for various applications; for example, at low temperatures for human body heat harvesting, at mid-temperature for automobile exhaust recovery systems, and at high temperatures for cement industries, concentrated solar heat exchangers, or NASA exploration rovers. We present the trends in the development of thermoelectric devices used for thermal management and waste heat recovery. In addition, a brief account is presented on the scientific development of TE materials with the various approaches implemented to improve the conversion efficiency of thermoelectric compounds through manipulation of Figure of Merit, a unitless factor indicative of TE conversion efficiency. Finally, as a case study, work on waste heat recovery from rotary cement kiln reactors is evaluated and discussed.

Effects of codoping on tin selenide nanomaterials to enhance the thermoelectric performance above the ambient temperature range

“…17 Similarly, 53.4 and 54.9 eV represent 3d 5/2 and 3d 3/2 for Se. 2–31,33 Fig. 5(c) shows a high-resolution XPS spectrum for 2p Cu, indicating the presence of Cu + at binding energy 932 eV and Cu 2+ at 935 eV in SSCA-7-2.…”

“…To alleviate the global energy crisis, thermoelectric materials have gained research interest as more than 60% of the worldproduced energy is being lost in the form of heat energy. 1,2 Thermoelectric materials can directly convert heat energy into electrical energy and vice versa. These materials are used in thermoelectric generators (TEGs), which are free of moving parts without emitting any greenhouse gases, to produce clean and green energy.…”

Applications of Thermoelectric Generators To Improve Catalytic-Assisted Hydrogen Production Efficiency: Future Directions

“…Global warming as a consequence of burning fossil fuels has encouraged researchers to explore, design, and optimize alternative renewable energy technologies. − The establishment of sustainable energy sectors aims to decrease greenhouse gas (GHG) emissions and thus reduce global warming to well below 2 °C to align with the goals set out in the Kyoto Protocol and the Paris Agreement . In this approach, thermoelectric generators (TEGs) have shown promising capabilities in recovering the low-grade waste energy. − This technology is an effective method employed to take full advantage of using wasted thermal energy to improve the efficiency of clean energy sources, such as solar and geothermal. Furthermore, TEGs offer the benefit of simple and durable design with no moving parts and noise and are easy to operate with zero emissions. − In addition to the recent advances in the development of TE materials − as the main recipe for manufacturing better TEGs, several applications have been proposed and designed to commercialize TEGs with enhanced efficiencies for energy-intensive industrial operations (Figure ).…”

A facile route to fabricating a crack-free Mg0.99Cu0.01Ag0.97Sb0.99/graphene/PEDOT:PSS thermoelectric film on a flexible substrate

“…1 Thermoelectric (TE) materials, which are one of the prominent energy harvesting technologies, can directly convert the unutilized heat into electrical energy. 2–6 Recently, the potential application of TE materials in flexible device technology for harvesting waste heat has increased. 7–10 The conversion efficiency of the TE device is defined by the material's thermoelectric figure of merit, expressed as ZT = S 2 σT / κ total , where S , σ , κ total , and T stand for the Seebeck coefficient, the electrical conductivity, the total thermal conductivity, and the absolute temperature, respectively.…”