Integrated Energy and Thermal Management for Electrified Powertrains

Abstract

This study presents an integrated energy and thermal management system to identify the fuel-saving potential caused by cold-starting an electrified powertrain. In addition, it quantifies the benefit of adopting waste heat recovery (WHR) technologies on the ultimate fuel savings. A cold-start implies a low engine temperature, which increases the frictional power dissipation in the engine, leading to excess fuel usage. A dual-source WHR (DSWHR) system is employed to recuperate waste heat from exhaust gases. The energy harvested is stored in a battery and can be retrieved when needed. Moreover, the system recovers waste heat from an electric machine, including power electronics and a continuous variable transmission, to boost the heating performance of a heat pump for cabin heating. This results in a decrease in the load on the battery. The integrated energy and thermal management system aims at maximizing the fuel efficiency for a pre-defined drive cycle. Simulation results show that cold-start conditions affect the fuel-saving potential significantly, up to 7.1% on the New European Driving Cycle (NEDC), yet have a small impact on the optimal controller. The DSWHR system improves the fuel economy remarkably, up to 13.1% on the NEDC, from which the design of WHR technologies and dimensioning of powertrain components can be derived. As the optimal solution is obtained offline, a complete energy consumption minimization strategy framework, considering both energy and thermal aspects, is proposed to enable online implementation.