16 Electric and Hybrid Vehicles TABLE 1.5 Model Year 2020 Fuel Cell Electric Vehicles Make and Model Vehicle Type Powertrain:
Electric Motor/Battery-Pack Fuel Economy (miles/gge) (City/Combined/Highway) Honda Clarity Sedan/Wagon 130 kW electric motor; 346 V Li-ion battery 68/68/67 Hyundai Nexo SUV 120 kW electric motor; 240 V Li-ion battery 59/57/54 Hyundai Nexo Blues SUV 120 kW electric motor; 240 V Li-ion battery 65/61/58 Toyota Mirai Sedan/Wagon 113 kW electric motor; 245 V NiMH battery 67/67/67 1.7 WELL-TO-WHEEL ANALYSIS The well-to-wheel (WTW) efficiency is the measure of the overall efficiency of a vehicle starting from the extraction of raw fuel to the wheels including the efficiencies of energy conversion, trans- port and delivery at each stage.
The fuel can be extracted from the earth or sea or derived from a renewable source; the transportation can be through the land or sea or electrically through the transmission lines; and the energy conversion can be through the heat engines, electric machines or electrochemical devices. The energy transport and conversion path can be divided into two seg- ments of well-to-tank (WTT) and tank-to-wheel (TTW). The fuels for transportation are produced from energy feedstock in the wells through different fuel production pathways. The fuel stored in a vehicle is processed to deliver propulsion power at the wheels.
The WTT segment comprises feedstock-related stages (recovery, processing, transportation and storage) and fuel-related stages (production, transportation, storage and distribution). The TTW segment comprises the energy con- version and delivery stages from the tank to the wheels of a vehicle. This WTW efficiency is conse- quently the product of the WTT and TTW efficiencies. Figure 1.7 represents the processes involved in evaluating the WTW efficiency. The WTW efficiency is an important factor for evaluating the overall impact, long-term feasibility and environmental effects of the alternative vehicles such as the EVs, HEVs, PHEVs and FCEVs.
The suitable energy paths can be identified and selected using WTW analysis to formulate energy strategies and energy policies. The WTW analysis also provides a level ground for comparing the alternative vehicles with the conventional ICEVs. The fundamen- tal laws of physics and chemistry with a common base for input parameters, numerical procedures, technology standards and user behavior must be used for these analyses [8]. FIGURE 1.7 Processes involved in WTW efficiency calculation.