Energy-saving cost-effectiveness analysis of improving engine thermal efficiency and extending all-electric range methods for plug-in hybrid electric vehicles

Abstract

Improving the engine peak thermal efficiency (Method 1) and extending PHEV’ all-electric range (Method 2) are the main methods to improve the fuel economy of PHEVs after the technical configuration and energy management strategy are determined. In this paper, the technology evaluation model of the powertrain (TEMP) for PHEVs is built to study the two method’s influencing mechanisms on the fuel economy and the corresponding energy-saving cost-effectiveness. The results show that Method 1 can reduce the PHEV’s fuel consumption in charging-sustaining (CS) mode and reduce their comprehensive fuel consumption (CFC). The fuel consumption for PHEV-49%-50 (the peak engine thermal efficiency is 49%, and the all-electric range is 50 km) in CS mode could decrease by 23.5% compared to PHEV-37%-50, and the CFC could then decrease by 23.3%. While Method 2 increases the PHEV’s fuel consumption in CS mode. The mechanism of CFC reduction results from the diluting effect of the progressively stronger all-electric range on the fuel consumption of CS mode. The fuel consumption for PHEV-37%-90 in CS mode would increase by 2.0% compared to PHEV-37%-50, while the CFC could decrease by 49.6%. Under the Business-as-Usual scenario, the cost-effectiveness of the Method 1 is higher than the Method 2 when the DMC is lower than 19,120$, but then the opposite happens. The increase of battery energy density and the decrease of battery unit DMC will further enhance the cost-effectiveness advantage of Method 2. This study can guide automotive manufacturers to design the PHEVs’ energy-saving technologies and support the government in formulating and revising the policies and standards about PHEVs.