Exhaust energy conversion by thermoelectric generator: Two case studies

Abstract:Thermoelectric (TE) technology is regarded as alternative and environmentally friendly technology for harvesting and recovering heat which is directly converted into electrical energy using thermoelectric generators (TEG). Conversely, Peltier coolers and heaters are utilized to convert electrical energy into heat energy for cooling and heating purposes The main challenge lying behind the TE technology is the low efficiency of these devices mainly due to low figure of merit (ZT) of the materials used in making them as well as improper setting of the TE systems. The objective of this work is to carry out a comprehensive review of TE technology encompassing the materials, applications, modelling techniques and performance improvement. The paper has covered a wide range of topics related to TE technology subject area including the output power conditioning techniques. The review reveals some important critical aspects regarding TE device application and performance improvement. It is observed that the intensified research into TE technology has led to an outstanding increase in ZT, rendering the use TE devices in diversified application a reality. Not only does the TE material research and TE device geometrical adjustment contributed to TE device performance improvement, but also the use of advanced TE mathematical models which have facilitated appropriate segmentation TE modules using different materials and design of integrated TE devices. TE devices are observed to have booming applications in cooling, heating, electric power generation as well as hybrid applications. With the generation of electric energy using TEG, not only does the waste heat provide heat source but also other energy sources like solar, geothermal, biomass, infra-red radiation have gained increased utilization in TE based systems.However, the main challenge remains in striking the balance between the conflicting parameters; ZT and power factor, when designing and optimizing advanced TE materials.Hence more research is necessary to overcome this and other challenge so that the performance TE device can be improved further.

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“…Various parameters for the TEG in the vehicle are predicted, where the maximum possible exhaust power that can be extracted is defined as [63];…”

Section: Application Of Teg For Heat Recovery From the Vehiclementioning

confidence: 99%

A comprehensive review of thermoelectric technology: Materials, applications, modelling and performance improvement

Twaha

Zhu

Yan

et al. 2016

Renewable and Sustainable Energy Reviews

485

208

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“…As a general trend, as the rate of heat transfer increased, both the power output and the TEG efficiency increased. The TEG efficiencies measured are comparable with similar systems that make use of TEGs [2,19]. For the same 4 tests conducted in table 5, the pressure difference over the inlet and outlet of the exhaust duct was recorded.…”

Section: Experimental Testingmentioning

confidence: 60%

Experimental testing of a car exhaust heat recovery system utilising TEGs and heat pipes

Orr

Akbarzadeh

2016

VTE-J

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On the left is a schematic of the exhaust heat recovery system and on the right is the full system assembly.Orr, Bradley and Akbarzadeh, Aliakbar RMIT ABSTRACTExhaust heat recovery systems are used to make use of otherwise wasted heat from a car engine. The purpose of exhaust heat recovery systems is to potentially reduce the fuel consumption of the car and consequently reduce CO2 emissions and running costs. The unique system design described herein utilises thermoelectric generators (TEGs) and heat pipes with its key advantage being it is a passive solid state design. The use of heat pipes allows for more flexible designs as the TEG location is not limited to the exhaust pipe surface. Testing was undertaken on a car with a 3.0L V6 engine. The theoretical modeling was shown to be valid at relatively low exhaust temperatures but deviates at higher exhaust temperatures. It is believed that the heat pipes are operating beyond their capacity at higher temperatures so the model deviates. In all test conditions the power loss due to pressure drop in the exhaust duct was always lower than the electrical power output. Repeat tests were conducted and the results were found to be consistent. When testing the system at different orientations, the bottom heat mode was found to be the best option. After all testing, the maximum power output of the system was 38W from the 8 62mmX62mm TEGs used. The rate of heat transfer in this case was 1541W with the resultant TEG efficiency being 2.46%. The calculated potential reduction in CO2 emissions, fuel consumption and fuel costs was 1.57%.Paper Number Vol N, No N (YYYY) SAE-A Vehicle Technology Engineer -Journal (VTE-J)

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“…Stobart et al reports that 4.7% of fuel savings can be achieved [6]. Another study found that the energy recover barely offsets the additional cost of the system and is not enough to justify the cost [7]. In current state, the TEG cost is around $10/(W/K) and a significant amount of research and development is necessary to reach a viable value [8].…”

Section: Introductionmentioning

confidence: 99%

Exergy Analysis of Organic Rankine Cycle and Electric Turbo Compounding for Waste Heat Recovery

Muhammad

Mamat

Salim

2018

IJET

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With such tough legislation on current emission standards, car manufacturers are focusing on increasing the efficiency of their engines with the development of advance waste heat recover (WHR) technology. Organic Rankine Cycle (ORC) and Electric Turbo Compounding (ETC) system have a good potential to be used as exhaust energy recovery. This paper compares the exergy availability and losses between the ORC and the ETC. In this particular study, exhaust data from the Proton 1.6L CamPro CFE turbocharged engine was used. This particular engine already has a main turbocharger, making the added WHR as a secondary recovery system to further increase the engine efficiency. Both systems are coupled to a 1 kW electric generator for ease of comparisons. At first the available exer gy is calculated for both WHR technologies. Exergy losses from rotating the generator are analysed to finally determine the thermal effi ciency of the overall system. Exergy calculation is simplified to only account for chemical and physical exergy since kinetic and potential energy are negligible in comparison. Available exergy for ORC was significantly high which went up to 12.5 kW with the exergy losses recorded at 9.7 kW. The ETC achieved only 5 kW but had a small loss at 8x10-3 kW. Average thermal efficiency of the ORC systems was 10.7% compared to ETC which was 58.7%. It can be concluded that the complexity of the ORC system contributes to its downfall where multiple components increase its exergy losses compared to the simplistic design of an ETC.

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Exhaust energy conversion by thermoelectric generator: Two case studies

Cited by 212 publications

References 18 publications

A comprehensive review of thermoelectric technology: Materials, applications, modelling and performance improvement

A comprehensive review of thermoelectric technology: Materials, applications, modelling and performance improvement

Experimental testing of a car exhaust heat recovery system utilising TEGs and heat pipes

Exergy Analysis of Organic Rankine Cycle and Electric Turbo Compounding for Waste Heat Recovery

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