Control concept for the electrical integration of thermoelectric generators into a vehicle power supply

Abstract

The optimization of combustion engines is a major aim in the research and develop- ment of automotive. Through the enacted laws of many governments, the focus is to reduce the hazardous emissions. The most potential energy of fossil fuel is disappearing as heat. This wasted thermal power has a high potential to increase the efficiency of a combustion engine and also to reduce the CO2 emissions. The unused exhaust gas waste heat can be converted into electric power by using a thermoelectric generator (TEG). The linking of TEG and the vehicle power supply may be realized with a DC-DC converter. The temperature of the exhaust gas waste heat affects the electric characteristic of a TEG. This paper presents a digital control concept for a DC-DC converter to charge a bat- tery and supply the electric load. Width variations of electric parameters of the TEG are influencing the dynamic and stability of the controllers. The parameters of the controllers are selected by robust criteria to ensure stability and an efficient linking of the electric power from TEG to the vehicle power supply. To track the maximum power point (MPP) of the TEG, a hill climbing (HC) algorithm is implemented. Experimental results show the verification of the controlling. such as axial penetration, spray cone angle, fluid velocities as well as droplet diameter distribution at different locations. Their comparative dependencies on exhaust flow characteristics, mass flow and temperature, are of particular interest. These dependencies are items of an extensive study on the Empa test flow rig. The flow rig is modular, geometrically similar to real world exhaust aftertreatment systems, and capable of variable temperatures and gas compositions. Shadow imaging is employed to examine the spray macro-properties. Planar laser sheet Mie-scattering supplies cross-sections of the spray structure and double images for particle image ve- locimetry (PIV) processing for velocity fields. Phase Doppler Anemometry (PDA) is used for droplet sizing and droplet velocity measurements.