Reducing Automobile CO2 Emissions with an Exhaust Heat Recovery System Utilising Thermoelectric Generators and Heat Pipes

Exhaust 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 reduce the fuel consumption of the car and consequently reduce CO₂ emissions. 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 these components creates a few design constraints. For example, both the TEGs and heat pipes have operating temperature limitations. In this paper, a naphthalene heat pipe preheat exchanger is proposed to deal with this problem. Exhaust conditions measured from a representative spark ignition engine were used in a numerical simulation to predict the performance of the exhaust heat recovery system. If 8 modules are used and the engine is producing 8kW of mechanical power, the system is predicted to produce 53.75W of electrical power. The calculated reduction of CO₂ emissions is 1.125% under these conditions. If fewer modules are used, less power is produced but the cost per watt decreases.