Trade-Offs and Opportunities to Improve Hybrid Vehicle Performance, Cost and Fuel Economy through Better Component Technology and Sizing 2023-01-0477

Hybrid electric vehicles (HEVs) have seen tremendous improvements in performance, fuel economy and cost over the last two decades. As battery and motor prices decrease, HEVs are likely to be even more attractive to consumers. This study considers how HEVs can improve and whether advancements in engines and other components will play a large role in the HEV segment. Past studies have relied on a rule-based component sizing approach for hybrids to meet certain performance criteria. By going beyond this approach, we can explore the design space by varying engine power and electric drivetrain power. This can provide more insights into the fuel-saving potential of HEVs, and the trade-offs required on performance or cost characteristics to achieve those savings.

In this study, we examine the fuel-saving potential of three main hybrid powertrain architectures (parallel, series, and power-split) with varying degrees of hybridization (DOH) and using various engine technologies. With a simple set of assumptions, we show that further optimization of HEVs is possible. Our study reveals that parallel HEVs could achieve up to 20% fuel savings over start-stop systems, without incurring any additional expense for the end user. Sensitivity of total cost of ownership (TCO) to miles driven by users is also examined. We see that higher DOH may not be economically attractive for everyone, but taxis or other vehicles that run longer distances can adopt higher DOH with economic benefits. Finally, we quantify the possible fuel savings with a relaxed performance requirement.