**2.3. The potential integration of TEG system with mufflers or catalytic converters**

Since the economics of thermoelectric power generation depends on the nature of the heat source, there is an increasing awareness of deep integration among undergoing research projects. Moving thermoelectric power assembly closer to the ICE will certainly enhance the TEG performance. Inevitably, stricter requirements of TEG have to match working condition both muffler and thermoelectric power generators when such integration happens. One apparent advantage of such integration is the cost reduction of manufacturing.

Mufflers are used for noise reduction emitted by the exhaust of an internal combustion engine. It usually consists of several perforated tubes inside the shell. The structure of muffler is similar to the common shell and tube heat exchanger. In that case, it inspire a natural thinking of integrating two separated components into one functional device. Therefore, the integration can be achieved by redesign the muffler structure with added TEG modules on the inner surface of the shell. Double layered shell may accommodate coolant loop to cool the TEG modules. Nonetheless, both noise reduction and TEG assembly performance have to be re-evaluated under such circumstances.

At present, most of the TEGs installed in the exhaust pipe system are located after the catalyst converter. The simple reason is that the exhaust emission treatment is prior to energy recovery process. However, the high temperature will decrease roughly by 100 K through the catalyst converter. If TEG developer would like to harness higher-grade heat from exhaust, the integration with catalyst converter is sensible but difficult. Inside catalyst converter, there are two functional components including reduction and oxidation process. Both components are coated perforated structures with 600 mesh number or higher. Therefore, fundamental changes in combined structure are needed and effects of harmful gas on the TEG modules need investigation in future work.
