**9. Cost analysis of automotive TEG**

Though the TEG for automotive exhaust application envisaged improving the overall fuel efficiency, the final task of implementation on commercial scale mainly depends on the cost–benefit it offers over the lifespan of a vehicle. At present, both technological and cost factors of AETEG are not in favor for such commercial realization. The major cost components in the AETEG come from modules, heat exchangers for hot and cold side, power conditioning unit with control systems, and so on. Various cost analysis studies carried out in passenger automobiles under different operating conditions suggest that the cost of the existing TE modules alone must be reduced up to 40% by using low-cost materials with higher zT [44]. In an analysis carried out in conventional vehicles operated in Korea, Bang et al. reported that the application of TEG in mid-size sedan and the medium-duty truck can save 0.15 and 1.04 kL fuel, respectively, at a driving speed of 80 km/h. Such fuel savings show that the economically acceptable costs of the TEG system for these two vehicles are 744 \$/kW (mid-size sedan) and 2905 \$/kW (medium duty truck) [45]. A comprehensive cost analysis of the real application scenario of automotive TEG using skutterudites module by Hendricks et al. suggests that the heat exchangers cost most often dominate the overall AETEG cost, and it is necessary to bring down from the current 10\$/W to l \$/W or lesser [46]. They observed that the minimum system cost is coinciding with the maximum power point which is governed by factors such as exhaust temperature, ΔT between the hot and cold side of the module, zT of the materials, thermal conductance between the hot and cold sides, heat exchanger cost factor and the parasitic losses. The rolling resistance arising due to the weight of the TEG alone would attract the penalty of a significant fraction of the power produced. In a 1.5 L engine family car tested under new European drive cycle incorporating an AETEG showed a power loss of 12 W/kg [47]. The additional load for the coolant pump for circulating the coolant to the cold side heat exchanger would further add up to the power loss. Employing low-density materials in both the heat exchanger/s and TE modules would considerably reduce the AETEG cost by decreasing its weight and parasitic losses associated with it.
