Although Hybrid Electric Vehicles (HEVs) represent one of the key technologies to reduce CO 2 emissions, their effective potential in real world driving conditions strongly depends on the performance of their Energy Management System (EMS) and on its capability to maximize the efficiency of the powertrain in real life as well as during Type Approval (TA) tests. Attempting to close the gap between TA and real world CO 2 emissions, the European Commission has decided to introduce from September 2017 the Worldwide Harmonized Light duty Test Procedure (WLTP), replacing the previous procedure based on the New European Driving Cycle (NEDC). The aim of this work is the analysis of the impact of different driving cycles and operating conditions on CO 2 emissions and on energy management strategies of a Euro-6 HEV through the limited number of information available from the chassis dyno tests. The vehicle was tested considering different initial battery State of Charge (SOC), ranging from 40% to 65%, and engine coolant temperatures, from −7 • C to 70 • C. The change of test conditions from NEDC to WLTP was shown to lead to a significant reduction of the electric drive and to about a 30% increase of CO 2 emissions. However, since the specific energy demand of WLTP is about 50% higher than that of NEDC, these results demonstrate that the EMS strategies of the tested vehicle can achieve, in test conditions closer to real life, even higher efficiency levels than those that are currently evaluated on the NEDC, and prove the effectiveness of HEV technology to reduce CO 2 emissions.
Plug-in
hybrid electrical vehicles (PHEVs) are generally considered
to be a cleaner alternative to conventional passenger cars. However,
there is still very limited information available regarding criteria
pollutant emissions from these vehicles. This paper shows, for the
first time, the emissions of criteria pollutants, unregulated pollutants,
and CO
2
and also electric range from two very different
PHEVs, one Euro 6 parallel plug-in hybrid and one range-extended battery
electric vehicle (BEVx), applying the new world harmonized light-duty
test procedure at ambient temperatures equal to 23 and −7 °C.
The impact of using a cabin air heating system on vehicle electric
range and emissions at cold temperature has also been studied. Cold
ambient temperatures and, to a larger extent, the use of heating systems
have been shown to lead to a pronounced negative impact on emissions
and shorter electric ranges. Results also show that modern PHEVs can
emit similar, or even higher, levels of pollutants (e.g., particle
number) as Euro 6 conventional gasoline and diesel vehicles.
Multi-type fast charging stations are being deployed over Europe as electric vehicle adoption becomes more popular. The growth of an electrical charging infrastructure in different countries poses different challenges related to its installation. One of these challenges is related to weather conditions that are extremely heterogeneous due to different latitudes, in which fast charging stations are located and whose impact on the charging performance is often neglected or unknown. The present study focused on the evaluation of the electric vehicle (EV) charging process with fast charging devices (up to 50 kW) at ambient (25 • C) and at extreme temperatures (−25 • C, −15 • C, +40 • C). A sample of seven fast chargers and two electric vehicles (CCS (combined charging system) and CHAdeMO (CHArge de Move)) available on the commercial market was considered in the study. Three phase voltages and currents at the wall socket, where the charger was connected, as well as voltage and current at the plug connection between the charger and vehicle have been recorded. According to SAE (Society of Automotive Engineers) J2894/1, the power conversion efficiency during the charging process has been calculated as the ratio between the instantaneous DC power delivered to the vehicle and the instantaneous AC power supplied from the grid in order to test the performance of the charger. The inverse of the efficiency of the charging process, i.e., a kind of energy return ratio (ERR), has been calculated as the ratio between the AC energy supplied by the grid to the electric vehicle supply equipment (EVSE) and the energy delivered to the vehicle's battery. The evaluation has shown a varied scenario, confirming the efficiency values declared by the manufacturers at ambient temperature and reporting lower energy efficiencies at extreme temperatures, due to lower requested and, thus, delivered power levels. The lowest and highest power conversion efficiencies of 39% and 93% were observed at −25 • C and ambient temperature (+25 • C), respectively.
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