A consequence of the second law of thermodynamics is that any thermodynamic process will lead to the production of waste heat. However, if we can capture this waste heat, we can use it for other purposes.
Researchers at Ulsan National Institute of Science and Technology (UNIST) have developed a method utilizing paintable materials to recycle waste heat from industrial processes into a source of electricity. The research team, led by professor Jae Sung Son, created a new type of high-performance thermoelectric (TE) material that possesses liquid properties and can be painted directly on the surface of almost any heat source. This process could increase the energy efficiency in industrial applications and act as a new source for renewable electric power.
The process relies on the thermoelectric effect, which is the direct conversion of a temperature difference into an electric voltage, and vice-versa. The thermoelectric effect is typically used in small cooling systems such as automotive cooling systems and waste heat recovery systems. The typical thermoelectric modules currently in use are in the shape of rectangular parallelepipeds.
The power output of these generators depends on their material properties, as well as the configuration of the generators with the heat sources. Since a large number of heat sources are irregular and have curved surfaces, there is considerable heat loss due to the mismatch of these planar devices being in contact with irregular surfaces (see illustration).
With the end goal of overcoming these drawbacks, the research team developed the shape-engineerable thermoelectric painting technique, where the TE material is directly brushed onto the surface of the heat source. This material is composed of Bi2Te3-based inorganic paints using the molecular Sb2Te3 chalcogenidometalate as a sintering aid.
The team tested the TE paints on a variety of surfaces, and demonstrated that it is an efficient method of heat collection, with very high power output densities of 4 mW/cm2. This is the best value so far among painted TE generators.
The team believes that this technology overcomes the drawbacks of existing TE generators, and will also reduce the costs of manufacturing these TE systems. Further developments in this technology can help in the development of more sustainable and energy efficient systems, as well as the availability of auxiliary electric power for a variety of purposes.
For more information about this research, visit the original article by the UNIST team in Nature Communications here. For a short explanation on Thermoelectric (TE) devices, view a video here.