**10. Summary**

of terminal voltages, especially during charging, which should not be neglected. Later, Yu et al. proposed the MPPT technique based on the measurement of TEG power which is derived from its terminal voltage and current [41]. However, such maximization has not taken into account the power converter loss, which should not be a constant value. Subsequently, the same group has proposed a DC-DC Ćuk converter-based power regulation system with the MPPT technique which considers both the terminal voltage and current of the battery to maximize the TEG output power instead of using terminal voltage and current [42]. **Figure 7** shows the schematic of power conditioning scheme proposed based on battery voltage and current. The variation of

Fang et al. proposed a novel MPPT scheme which involves the aggregated dichotomy and gradient (ADG) method for rapid tracking the maximum power in an automotive TEG [43]. They carried out the steady state and transient tracking experiments under various load conditions of dynamometer and compared the ADG method with traditional methods like single gradient method (SGM), single dichotomy method (SDM) and perturbation and observation method (PAO). The results showed that the ADG had better tracking accuracy and speed

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

battery voltage and power converter loss is also taken into account in this system.

**Figure 7.** Schematic of power conditioning system based on battery voltage and current [40].

compared to the traditional methods.

178 Bringing Thermoelectricity into Reality

**9. Cost analysis of automotive TEG**

Hydrocarbon-based fuels will continue to be a primary source of energy for transportation for the next few decades. Improving the efficiency of the vehicles by even few percentages will have a tremendous effect on the fuel savings and controlling the emissions. Automotive TEG is one potential technology which can increase the vehicle fuel efficiency. Though the technique is known for several decades, significant progress has been made in materials, modules, and systems over the past 20 years only and as of today it is far from commercialization. The high cost and low efficiency of the currently available modules make the overall cost of the TEG much higher than \$1/W barrier apt for implementation this technology in vehicles. The high zT observed in several low-cost materials in recent years need to be translated into reliable high-power output modules. An innovative design which reduces the overall weight of the AETEG with improved efficiency is a key necessity to make this technology commercially successful.
