Thermoelectricity and Materials

Introduction

Thermoelectricity is the spontaneous conversion of heat into electricity or electricity into heat. It occurs in two mechanisms – the Seebeck effect or the Peltier effect (Goldsmid 2). Both mechanisms happen at a junction of material with two dissimilar conductors. In the Peltier effect, one junction cools the material while the other increases heat. In the Seebeck effect, an emf is produced at the material’s junction and, consequently, an electric loop. Definition of both effects shares a keyword – material. Snyder and Toberer define thermoelectric materials as those that generate electricity from waste heat or are applicable as solid-state Peltier coolers (105). They are materials that show thermoelectric effect –phenomena where temperature difference in a material creates an electric potential (emf) or an electric potential generates heat. 

Thermoelectric Materials 

Some examples of thermoelectric materials include Bismuth telluride (Bi₂Te₃), Lead Telluride (PbTe), and Silicon-Germanium. These materials’ development has become successful through doping semiconductors and alloying of metals (Liu and Wang 2). Scientists have thus far worked hard and successfully to enhance thermoelectricity in materials, such that the dimensionless index ZT value has now exceeded unity (Zhu et al. 1605884). Liu and Wang further explain that thermoelectric materials’ efficiency is comparable with the temperature dependence from a basic combination of the “intrinsic thermoelectric property, the electrical resistivity, and the material’s thermal conductivity” (2).

The nature of its defects mostly influences the transport mechanisms of materials, and the performance of a particular transport mechanism is influenced by the concentration of carriers (Goupil et al. 1485). Thus, material scientists have become particularly interested in developing thermoelectric materials for specific applications. For instance, Bi₂Te₃ is used for refrigeration, while Silicon-Germanium is used in the manufacture of transistors.

Applications of Thermoelectricity

Solar cells have mostly utilized thermoelectricity, in that they harness heat and convert it into electricity used for domestic and commercial purposes. In space, thermoelectric generators have become a valuable option for energy generation due to resilience in harsh environments and reliability factors (Stockholm 10263). In automobiles, the heat generated by engines and microprocessors is harvested and converted into electricity, thus increasing the system’s efficiency. Besides energy generation, thermoelectricity is used in domestic and industrial cooling. For instance, Acubite has been used to make can coolers for care seats.

Advantages of Thermoelectric Materials

The advantages of thermoelectricity are revealed in the application of thermoelectric materials in generators or refrigerators.  Overall, thermoelectricity is a significant actor in the endeavors to solve the global energy crisis. The energy supply on a global scale is far from adequate; yet, the available technologies to produce domestic and industrial energy are either environmental pollutants or not affordable. Nevertheless, thermoelectric generators are reliable, environmentally friendly, highly scalable, cost-effective. Besides, they help recycle thermal energy and reduce the adverse impacts of entropy on the universe.

Like the thermoelectric generation, thermoelectric refrigeration is arguably the most sustainable cooling technology. For instance, a thermoelectric cooling module can cool or heat a system depending on the materials’ polarity. It does not have moving parts and is thus maintenance-free. Also, this makes it electrically quiet. It is also very environmentally friendly since, unlike conventional refrigerators, thermoelectric refrigerators do not use chemicals. Atta sums other advantages of thermoelectric refrigerators: they have “high reliability, low weight, small size, intrinsic safety for hazardous electrical environments, and accurate temperature control” (250).

Disadvantages of Thermoelectric Materials

There are several drawbacks that concern thermoelectricity. In application, thermoelectric generators have a low energy conversion. This means that efficiency might be affected as the scale of energy production increases. Also, it has thermoelectric generators that require a fairly constant heat source in practice. Concerning thermoelectric coolers, they are not cost-efficient for most domestic applications. Their coefficient of performance is also relatively low compared to conventional colling modules. For instance, a domestic thermoelectric refrigerator cools slowly compared to conventional refrigerators. The technology is growing slowly, and thus, there is limited industrial education and lagged adoption.

The Future of Thermoelectricity

Despite thermoelectricity technology lagging behind other technologies, studies reveal that it is potentially significant for future energy systems. Ghani et al. found that future automobile makers will utilize thermoelectric technologies to reduce waste of heat into the atmosphere to reduce environmental pollution and increase efficiency (89). The current trend is promising, efficient thermoelectric systems and broad domestic and commercial applications (Weidenkaff 8).

Conclusion

Thermoelectricity concerns conversion of heat into electricity and vice versa through the Seebeck and Peltier effects. This technology has become successful by doping semiconductors, alloying technologies, and advanced knowledge in material science. Thermoelectric modules have applications in energy niches, where they have proven efficiency and environmental friendliness, but they have limited domestic and commercial applications. In the future, they might have a wide range of applications.

Works Cited

Atta, Raghied M. “Thermoelectric Cooling”. Bringing Thermoelectricity Into Reality, 2018. Intech, doi:10.5772/intechopen.75791. Accessed 21 Nov 2020.

Ghani, Muhammad Usman et al. “Future Impact Of Thermoelectric Devices For Deriving Electricity By Waste Heat Recovery From IC Engine Exhaust”. NFC-IEFR Journal Of Engineering And Scientific Research, vol 4, no. 1, 2016, pp. 84-90. NFC Institute Of Engineering And Fertilizer Research, doi:10.24081/nijesr.2016.1.0016. Accessed 21 Nov 2020.

Goldsmid, Hiroshi Julian. Introduction To Thermoelectricity. Springer Science & Business Media, 2009.

Goupil, Christophe et al. “Thermodynamics Of Thermoelectric Phenomena And Applications”. Entropy, vol 13, no. 8, 2011, pp. 1481-1517. MDPI AG, doi:10.3390/e13081481. Accessed 21 Nov 2020.

Liu, Xiaowei, and Ziyu Wang. “Printable Thermoelectric Materials And Applications”. Frontiers In Materials, vol 6, 2019. Frontiers Media SA, doi:10.3389/fmats.2019.00088. Accessed 21 Nov 2020.

Snyder, G. Jeffrey, and Eric S. Toberer. “Complex Thermoelectric Materials”. Nature Materials, vol 7, no. 2, 2008, pp. 105-114. Springer Science And Business Media LLC, doi:10.1038/nmat2090. Accessed 21 Nov 2020.

Stockholm, John G. “Applications In Thermoelectricity”. Materials Today: Proceedings, vol 5, no. 4, 2018, pp. 10257-10276. Elsevier BV, doi:10.1016/j.matpr.2017.12.273. Accessed 21 Nov 2020.

Weidenkaff, Anke. “Thermoelectricity For Future Sustainable Energy Technologies”. EPJ Web Of Conferences, vol 148, 2017, p. 00010. EDP Sciences, doi:10.1051/epjconf/201714800010. Accessed 21 Nov 2020.

Zhu, Tiejun et al. “Compromise And Synergy In High-Efficiency Thermoelectric Materials”. Advanced Materials, vol 29, no. 14, 2017, p. 1605884. Wiley, doi:10.1002/adma.201605884. Accessed 21 Nov 2020.