Battery State-of-Charge-Driven Control of a Solar Mild-Hybrid Vehicle

Recovering solar energy during parking phases can significantly improve light-duty vehicles’ fuel economy (FE) and help in reducing greenhouse gas impact and harmful tailpipe emissions. Nevertheless, the contribution due to off-driving photovoltaic (PV) recharging shall be adequately accounted for when approaching the development and testing of energy-efficient and environment-friendly powertrain energy management. The aim of this work was thus to enhance the existing highly charge-depleting (HCD) control strategy of a 48V mild-hybrid electric vehicle (MHEV), implementing a state-of-charge-dependent soft charge-depleting (SCD) one.

The performance of the implemented control strategy was analyzed on two different vehicle configurations, obtained by integrating a solar kit with the aforementioned mild-hybrid powertrain. The modelling framework used to perform simulation-based analysis was suitably updated in such a way as to test both charge-depleting and quasi-charge-sustaining strategies. A scenario analysis was thus enabled, whose objective was to assess the FE and carbon dioxide (CO₂) reduction potential associated with the joint effect of solar hybridization and the proposed battery state-of-charge-driven control rules. The Federal Urban Driving Schedule (FUDS) was simulated for the four vehicle scenarios available (conventional, MHEV-HCD, MHEV-SCD, and solar mild hybrid). The results confirmed the high potential of solar-assisted mild-hybridization of original conventional vehicles, with significant benefits (i.e., about 30% improvement) achieved both in terms of FE and CO₂ emissions.