New metrics for evaluating energy efficiency of solar electric vehicles based on self-consumption and self-sufficiency

Solar Electric Vehicles (SEVs), which generate electricity through onboard photovoltaic panels, are emerging as a sustainable transportation alternative. However, conventional energy efficiency metrics for internal combustion engine vehicles and battery electric vehicles are inadequate for capturing the unique energy flow characteristics of SEVs. This study proposes a new energy efficiency evaluation framework for SEVs using two metrics: Self-Consumption Rate (${\text{SCR}}_{\text{SEV}}$) and Self-Sufficiency Rate (${\text{SSR}}_{\text{SEV}}$). These metrics distinguish between self-generated energy and externally supplied energy, enabling a more accurate assessment of SEV energy utilization. Simulation analyses were conducted under various environmental conditions and vehicle specifications, considering solar power generation, battery charge-discharge behavior, and power consumption patterns. The results demonstrate that ${\text{SCR}}_{\text{SEV}}$ and ${\text{SSR}}_{\text{SEV}}$ effectively reflect the sensitivity of SEV performance to changes in weather conditions and operational scenarios. For example, ${\text{SCR}}_{\text{SEV}}$ and ${\text{SSR}}_{\text{SEV}}$ were 84 % and 74 % on clear days, while reaching 90 % and 46 % on cloudy days, highlighting the capability of the proposed metrics to capture energy variations in energy autonomy. The evaluation results based on the conventional SCR and SSR calculation methods were compared with those derived from the newly proposed framework. The proposed framework offers valuable insights for assessing energy independence and grid dependency in future solar-powered mobility systems and Vehicle-to-Everything (V2X) applications.