Open access peer-reviewed chapter

# Automotive Waste Heat Recovery by Thermoelectric Generator Technology

Written By

Duraisamy Sivaprahasam, Subramaniam Harish, Raghavan Gopalan and Govindhan Sundararajan

Submitted: October 16th, 2017 Reviewed: February 14th, 2018 Published: July 11th, 2018

DOI: 10.5772/intechopen.75443

From the Edited Volume

## Bringing Thermoelectricity into Reality

Edited by Patricia Aranguren

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## Abstract

Automotive exhaust thermoelectric generators (AETEG) are gaining significant importance wherein a direct conversion of exhaust waste heat into electricity allows for a reduction in fuel consumption. Over the past two decades, extensive progress has been made in materials research, modules and thermoelectric generator (TEG) system. Many prototypes using BiTe, CoSb3 and half Heusler materials have been developed and tested for efficiency in different engines. The role of exhaust flow rate, temperature and heat exchanger type on the performance of AETEG is investigated deeply. This chapter reviews the progress made so far in the AETEG technology. Section 1 gives a brief introduction; section 2 gives a description of the technology and section 3, the construction details of a typical AETEG. The performance evaluation of AETEG is discussed in Section 4, application of TEG using engine coolant heat is discussed in Section 5 and TEGs for hybrid vehicles are described in Section 6. The parasitic losses due to AETEG and the conditioning of the power produced for practical applications using the maximum power point tracking technique are discussed in Sections 7 and 8, respectively. Finally, in Section 9, cost analysis and the challenges associated with the commercialization of AETEG is presented.

### Keywords

• thermoelectric generator
• exhaust waste heat
• power output
• efficiency
• parasitic losses

## 1. Introduction

Among the major contributors to the greenhouse gas emissions to the environment, automobiles make a substantial contribution to the extent of 16.4% [1]. According to the information reported in energy technology perspective 2015, the number of light duty vehicles in the roads is expected to go up from present 900 million to 2 billion by 2050 [2]. With the global power sector moving towards clean technologies using renewable energy, the current 38% utilization of the global oil production for automotive use can increase to a significant extent. Though the advancement of electric vehicle (EV) technology is making a steady progress on one side (expected to reach 56 million passenger cars on road from the present 2 million by 2030), still it is far from making any drastic reduction in the emissions level due to transportation sector unless a radical innovation is made in the battery technology. Policies such as better urban planning that can increase the use of collective transportation and innovative technologies that can reduce the individual’s vehicle need can make considerable contributions to the reduction of the CO2 emissions. However, this requires substantial investment, and hence it is difficult to implement worldwide particularly in low and middle income countries. Implementing innovative technologies for improving automobile engine efficiency or innovations in the field of hybrid/low emissions vehicles can improve the fuel efficiency and thereby emissions can be reduced to a greater extent. Several recent developments in the engine, transmission and few ancillary systems of the vehicles show promising results. Converting a part of heat energy produced in the engine, released to the atmosphere via exhaust gas as waste heat into electricity by a thermoelectric generator (TEG) is one technology gaining a lot of attention in the past one decade though it is well explored long time back itself due to its inherent simplicity. This chapter discusses the various salient features and the progress made so far in this technology.

## 2. Electricity from automotive exhaust waste heat

In an internal combustion (I.C) engine, only one-third of the total heat produced in the fuel combustion is utilized for the propulsion of the vehicle while the remaining two-third goes as waste heat mainly through the exhaust gas and the engine coolant. The exhaust gas, usually at a higher temperature compared to the engine coolant which absorbs heat from engine walls, is let out in the atmosphere and the engine coolant is recirculated after cooling in the radiator. In some of the engines, particularly in diesel fuelled ones, to get better efficiency, part of the exhaust gas is cooled and mixed with air in exhaust gas recirculation (EGR) system to reduce the NOx emissions. Turbo-charging is another technology utilizing the heat from the exhaust gas to improve the engine power. However, in all these technologies, only a small fraction of the exhaust gas or its energy is converted into useful work and remaining is let out to the atmosphere. Improving the engine performance by making use of this exhaust waste heat has been a subject of intense research in the field of energy recovery systems, exhibiting promising outcomes in the recent past.

Automotive exhaust thermoelectric generator (AETEG) technology involves converting the waste heat available in the exhaust gas into electricity that can be stored and utilized for various electrical inputs of a vehicle so that the fuel efficiency can be improved. The first such system was developed in 1963 by Neild [3] followed by Serksnis [4] in 1976. Later, Birkholz et al. in 1988 [5] and Bass et al. in 1990 [6] demonstrated AETEG using thermoelectric (TE) modules made of Fe-based and BiTe materials, respectively. Although the earliest AETEG was developed more than 50 years ago, a surge in research activities in this field has been occurring only in the past 15 years, which is evident from Figure 1 showing the number of publications on this subject over the past five decades. Such exponential increase in the research output in recent years is mainly due to some of the path-breaking outcomes in the thermoelectric materials’ properties which improved the TE figure of merit (zT) value which was ˂1 over a long period to more than 1. In recent years, zT ≥2 were also reported in few materials, which were achieved by engineering the microstructure of materials in different length scales [7, 8].

## References

1. 1. Aren F, Mezzan L, Doyon A, Suzuki H, Lee K, Becker T. The Automotive CO2 Emissions Challenge. 2020 Regulatory Scenario for Passenger Cars. Rome: Arthur D. Little; 2014). http://www.adlittle.com/downloads/tx_adlreports/ADL_AMG_2014_Automotive_CO2_Emissions_Challenge.pdf
2. 2. Energy Technology Perspectives 2015, International Energy Agency, France. http://www.iea.org/publications/freepublications/publication/ETP2015.pdf
3. 3. Neild AB Jr. Portable thermoelectric generators, Society of Automotive Engineers, New York, SAE-645 A; 1963
4. 4. Serksnis AW. Thermoelectric generator for automotive charging system. In: Proceedings of 11th Intersociety Conversion Engineering Conference, New York, USA. 1976. pp. 1614-1618
5. 5. Birkholz U, Grob E, Stohrer U, Voss K, Gruden DO, Wurster W. Conversion of waste exhaust heat in automobile using FeSi2 thermoelements. Proc. 7th International Conference on Thermoelectric Energy Conversion, Arlington, USA; 1988. 124-128
6. 6. Bass JC, Campana RJ, Elsner NB, Thermoelectric generator for diesel trucks. Proceedings of the 10th International Conference on Thermoelectrics. Cardiff, Wales: Babrow Press; 1991
7. 7. Biswas K, He JQ, Blum ID, Wu CI, Hogan TP, Seidman DN, Dravid VP, Kanatzidis MG. High performance bulk thermoelectrics with all scale hierarchical architectures. Nature. 2012;489:414-418
8. 8. Zhao LD, Lo SH, Zhang YS, Sun H, Tan GJ, Uher C, Wolverton C, Dravid VP, Kanatzidis MG. Ultra low thermal conductivity and high thermoelectric figure of merit in SnSe crystals. Nature. 2014;508:373-377
9. 9. Thacher EF, Helenbrook BT, Karri MA, Richter CJ. Testing of automobile exhaust thermoelectric generator in a light truck, Proc. IMechE. Part D: Journal of Automobile Engineering. 2007;22:95-107
10. 10. Merkisz J, Fuc P, Lijewski P, Ziolkowski A, Galant M, Siedlecki M. Analysis of an increase in the efficiency of a spark ignition engine through the application of an automotive thermoelectric generator. Journal of Electronic Materials. 2016;45:4028-4037
11. 11. Frobenius F, Gaiser G, Rusche U, Welleri B. Thermoelectric generators for the integration into automotive exhaust systems for passenger cars and commercial vehicles. Journal of Electronic Materials. 2016;45:1433-1440
12. 12. Bass JC, Elsner NB, Leavitt FA. Performance of the 1 kW Thermoelectric Generator for Diesel Engines. Proc. of the 13th International Conference on Thermoelectrics, Kansas City, USA. 1994
13. 13. Ikoma K, Munekiyo M, Furuya K, Kobayashi M, Izumi T, Shinohara K. Thermoelectric module and generator for gasoline engine vehicles. 17th International Conference on Thermoelectrics; 1998. p 464-467
14. 14. Haidar JG, Ghojel JI. Waste heat recovery from the exhaust of low power diesel engine using thermoelectric generators. Proc ICT2001. 20th International Conference on Thermoelectrics (Cat. No.01TH8589). IEEE; 2001. p 413-418
15. 15. Matsubara K. Development of high efficient thermoelectric stack for a waste exhaust recovery of vehicle. 21st Int. Conference on Thermoelectrics, Proc. ICT 02. IEEE; 2002. p. 418-423
16. 16. Wojciechowski KT, Schmidt M, Zybala R, Merkisz J, Fuc P, Lijewsk P. Comparison of waste heat recovery from the exhaust of a spark ignition and a diesel engine. Journal of Electronic Materials. 2010;39:2034-2038
17. 17. Kim S, Park S, Kim S, Rhi S. A thermoelectric generator using engine coolant for light-duty internal combustion engine-powered vehicles. Journal of Electronic Materials. 2011;40:812-816
18. 18. Kim S, Won B, Rhi S, Kim S, Yoo J, Jang J. Thermoelectric power generation system for future hybrid vehicles using hot exhaust gas. Journal of Electronic Materials. 2011;40:778-783
19. 19. Crane D, Lagrandeur J, Jovovic V, Ranalli M, Adldinger M, Poliquin E, Dean J, Kossakovski D, Mazar B, Maranville C. TEG on vehicle performance and model validation and what it means for further TEG development. Journal of Electronic Materials. 2013;42:1582-1591
20. 20. Zhang Y, Cleary M, Wang X, Kempf N, Schoensee L, Yang J, Joshi G, Meda L. High temperature and high power density nanostructured thermoelectric generator for automotive waste heat recovery. Energy Conversion and Management. 2015;105:946-950
21. 21. Wang X, Li B, Yan Y, Liu S, Li J. A study on heat transfer enhancement in the radial direction of gas flow for thermoelectric power generation. Applied Thermal Engineering. 2016;102:176-183
22. 22. Deng YD, Liu X, Chen S, Tong NQ. Thermal optimization of the heat exchanger in an automotive exhaust based thermoelectric generator. Journal of Electronic Materials. 2013;42:1635-1640
23. 23. Bai S, Lu H, Wu T, Yin X, Shi X, Chen L. Numerical and experimental analysis for exhaust heat exchangers in automobile thermoelectric generators. Case Studies in Thermal Engineering. 2014;4:99-112
24. 24. Wang T, Luan W, Wang W, Tu S. Waste heat recovery through plate heat exchanger based thermoelectric generator system. Applied Energy. 2014;136:860-865
25. 25. Kempf N, Zhang Y. Design and optimization of automotive thermoelectric generators for maximum fuel efficiency improvement. Energy Conversion and Management. 2016;121:224-231
26. 26. Meng J, Wang X, Chen W. Performance investigation and design optimization of a thermoelectric generator applied in automobile exhaust waste heat recovery. Energy Conversion and Management. 2016;120:71-80
27. 27. Su CQ, Xu M, Wang WS, Deng YD, Liu X, Tang ZB. Optimization of cooling unit design for automotive exhaust-based thermoelectric generators. Journal of Electronic Materials. 2014;44:1876-1883
28. 28. Deng YD, Liu X, Chen S, Xing HB, Su CQ. Research on the compatibility of the cooling unit in an automotive exhaust-based thermoelectric generator and engine cooling system. 2013;43:1815-1823
29. 29. Bjork R, Sarhadi A, Pryds N, Lindeburg N, Viereck P. A thermoelectric power generating heat exchanger: Part I—Experimental realization. Energy Conversion and Management. 2016;119:473-480
30. 30. Sarhadi A, Bjork R, Lindeburg N, Viereck P, Pryds N. A thermoelectric power generating heat exchanger: Part II—Numerical modelling and optimization. Energy Conversion and Management. 2016;119:481-487
31. 31. Karri MA, Thacher EF, Helenbrook BT. Exhaust energy conversion by thermoelectric generator: Two case studies. Energy Conversion and Management. 2011;52:1596-1611
32. 32. Favarel C, Bedecarrats JP, Kousksou T, Champier D. Experimental analysis with numerical comparison for different thermoelectric generators configurations. Energy Conversion Management. 2016;107:114-122
33. 33. An unpublished work from our group. Centre for automotive energy materials (CAEM), ARC-International. INDIA
34. 34. Ramade P, Patil P, Shelar M, Chaudhary S, Yadav S, Trimbake S. Automobile exhaust thermo-electric generator design &performance analysis. International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com. May 2014;4(5). ISSN 2250-2459, ISO 9001:2008 Certified Journal
35. 35. Takanose E, Tamakoshi H. The development of thermoelectric generator for passenger car. In: Proceedings of the 12th IEEE International Conference on Thermoelectrics, Yokohama, Japan. New York: IEEE; November 1993. pp. 467-470
36. 36. Liu X, Deng YD, Wang WS, Su CQ. Experimental investigation of exhaust thermoelectric system and application of vehicle. Journal of Electronic Materials. 2015;44:2203-2210
37. 37. Deng YD, Fan W, Ling K, Su CQ. A 42-V electrical and hybrid driving system based on a vehicular waste-heat thermoelectric generator. Journal of Electronic Materials. 2012;41:1698-1705
38. 38. Fang W, Quan S, Xie C, Tang X, Ran B, Jia Y. Energy optimization for a weak hybrid power system of an automobile exhaust thermoelectric generator. Journal of Electronic Materials. 2017;46:6617-6627
39. 39. Kim S, Won B, Rhi S, Kim S, Yoo J, Jang J. Thermoelectric power generation system for future hybrid vehicles using hot exhaust gas. Journal of Electronic Materials. 2011;40:778-783
40. 40. Eakburanawat J, Boonyaroonate I. Development of a thermoelectric battery charger with microcontroller based maximum power point tracking technique. Applied Energy. 2006;83:687-704
41. 41. Yu C, Chau KT, Chan CC. Thermoelectric waste heat energy recovery for hybrid electric vehicles. Paper No. 21. In: International Electric Vehicle Symposium and Exposition; 2007
42. 42. Yu C, Chau KT. Thermoelectric automotive waste heat energy recovery using maximum power point tracking. Energy Conversion and Management. 2009;50:1506-1512
43. 43. Fang W, Quan SH, Xie CJ, Tang XF, Wang LL. Maximum power point tracking with dichotomy and gradient method for automobile exhaust thermoelectric generators. Journal of Electronic Materials. 2016;45:1613-1624
44. 44. Kishita Y, Ohishi Y, Uwasu M, Kuroda M, Takeda H, Hara K. Evaluating the life cycle CO2 emissions and costs of thermoelectric generators for passenger automobiles: A scenario analysis. Journal of Cleaner Production. 2016;126:607-619
45. 45. Bang S, Kim B, Youn Y, Kim YK, Wee D. Economic and environmental analysis of thermoelectric waste heat recovery in conventional vehicles operated in Korea: A model study. Journal of Electronic Materials. 2016;45:1956-1965
46. 46. Hendricks TJ, Yee C, Leblanc S. Cost scaling of a real world exhaust waste heat recovery thermoelectric generator: A deeper dive. Journal of Electronic Materials. 2016;45:1751-1761
47. 47. Rowe DM, Smith J, Thomas G, Min G. Weight penalty incurred in thermoelectric recovery of automobile exhaust. Journal of Electronic Materials. 2011;40:784-788

Written By

Duraisamy Sivaprahasam, Subramaniam Harish, Raghavan Gopalan and Govindhan Sundararajan

Submitted: October 16th, 2017 Reviewed: February 14th, 2018 Published: July 11th, 2018