Evaluating emissions and sensitivity of economic gains for series plug-in hybrid electric vehicle powertrains for transit bus applications

Abstract

From the design space explored for series architecture plug-in hybrid electric vehicle transit buses by the authors, one powertrain and control design is selected to provide maximum benefit to investment ratio. Sensitivity analysis is performed for this powertrain configuration. Vehicle parameters (including vehicle mass, coefficient of drag, coefficient of rolling resistance), usage parameters (drivecycle, annual vehicle miles traveled, number of recharges in a day, recharge current, and battery temperature), and economic parameters (fuel price, motor price, and battery price) are varied to understand their effect on the number of required battery replacements, net present value, payback period, and fuel consumption reduction. It is shown that battery temperature has the most significant impact, particularly on the number of battery replacements and net present value and, as such, must be well controlled in practice. It is shown that to maintain the battery at 20°C, for ambient temperatures between −5°C and 45°C, 0.8–1.8% excess fuel is required across all drivecycles for the considered plug-in hybrid electric vehicle transit bus powertrain configuration. In addition, the well-to-wheel emissions of criteria pollutants resulting from the usage of this plug-in hybrid electric vehicle transit bus in Indiana and California are calculated and compared with the conventional transit bus, using the GREET (Greenhouse Gases, Regulated Emissions and Energy Use in Transportation) Model. With a single over night charge, the plug-in hybrid electric vehicle transit bus operating in either Indiana or California produces 50% less CO2 and other greenhouse gases as compared to a conventional transit bus.

A Review on Environmental Efficiency Evaluation of New Energy Vehicles Using Life Cycle Analysis

“…Charging at night emits more CO 2 than charging during the day [99]. Charging during off-peak hours can reduce CO 2 , PM2.5, NO x and SO 2 emissions by 12%, 15%, 13% and 12%, respectively, during the operation phase [127], and different temperatures [128] can also affect each charge preference.…”

“…In general, 40% of maintenance costs are spent on parts procurement, and the rest are concentrated on manual labor [135]. Maintenance parts, except tires, power systems, coolants, brake fluids and windshields [136], as well as batteries are the focus of maintenance and the parts replacement of NEVs [128,134].…”

“…It is difficult to predict battery degradation [154], but it is one solution to simplify battery aging into battery replacement [154]. However, battery replacement does not simply represent battery aging because battery aging is a linear exponential [128], or even an exponential process [24,126], while battery replacement is a 0-1 process. Yang, for the first time, considered both battery aging and battery replacement in terms of the LCA environmental efficiency evaluation of NEVs and pointed out that when battery aging is ignored, the CO 2 emissions per kilometer of NEVs will be underestimated by 29% [134].…”