Abstract
Plug-in hybrid-electric vehicles (PHEVs) have emerged as a promising alternative to reduce fleet petroleum consumption. However, quantifying PHEVs’ expected benefit is more challenging than with other vehicle technologies because they receive energy from two distinct sources and exhibit widely varying per-mile consumption based on the drive cycle and distance driven. This paper reviews various PHEV fuel economy characterization techniques, including the procedure formalized in the SAE J1711 Recommended Practice (issued in 1999). SAE J1711 accurately captures several critical reporting practices, including: using standardized drive cycles; considering charge depleting and charge sustaining operation; and using driving-statistic-derived utility-factor weighting to properly combine the vehicle’s operating modes. The authors’ proposed modifications to J1711 include: separately reporting fuel and electricity use; specifically measuring the vehicle’s charge depleting performance; and applying a once-daily charging assumption. As the U.S. Environmental Protection Agency (EPA) begins implementing changes to window-sticker fuel economy test procedures, and the original issuance of SAE J1711 expires, the authors hope to stimulate discussion and contribute to adoption of consensus reporting metrics. In order for the resulting metrics to be useful, stakeholders must be able to translate the numbers into sound predictions of relative vehicle energy cost, petroleum use, and potential carbon dioxide (CO2) production.
Highlights
A Plug-in hybrid-electric vehicles (PHEVs) is a hybrid-electric vehicle (HEV) with the ability to recharge its electrochemical energy storage system with electricity from an off-board source
As the figure shows for the PHEV5 vehicle, the energy storage system (ESS) SOC drops quickly during the first half of the initial Urban Dynamometer Driving Schedule (UDDS) cycle, and continues to drop at a somewhat slower rate once it begins operating in a blended mode
By holding the Full-Charge Test (FCT) to the fixed length of four-cycles, the existing J1711 approach averages together roughly 50% CD operation and 50% CS operation to obtain the “CD rating” for the PHEV5, and it does not credit the PHEV30 for its continued CD operation beyond the end of the fourth cycle
Summary
A PHEV is a hybrid-electric vehicle (HEV) with the ability to recharge its electrochemical energy storage system with electricity from an off-board source (such as the electric utility grid). The vehicle can drive in a charge-depleting mode that reduces the system’s state-of-charge (SOC), thereby using electricity to displace petroleum fuel that would otherwise be consumed. PHEVs typically have batteries that are larger than those in HEVs so as to increase the potential for petroleum displacement. Plug-in hybrid-electric vehicles have recently emerged as a promising alternative to displace a significant fraction of vehicle petroleum consumption with electricity. PHEVs are very marketable in that they combine the beneficial attributes of HEVs and pure battery electric vehicles (BEVs) while simultaneously alleviating the disadvantages of each. PHEVs have the potential to come to market, penetrate the fleet, and achieve meaningful petroleum displacement relatively quickly. Few competing technologies offer this potential combined rate and timing of reduction in fleet petroleum consumption [1]
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