Vehicle drive systems

The lower heating value (LHV) of gasoline is assumed to be about 32 MJ/1, and that of diesel about 36 MJ/1. 

All fuel cells for use in vehicles are based on proton-exchange-membrane fuel cell (PEMFC) technology. The methanol fuel-processor fuel cell (FPFC) vehicle comprises an on-board fuel processor with downstream PEMFC. On-board methanol reforming was a development focus of industry for a number of years until around 2002. Direct-methanol fuel cells (DMFC) are no longer considered for the propulsion of commercial vehicles in the industry (see also Chapter 13). 

If the battery pack of hybrid vehicles can additionally be charged with electricity from the public electricity grid, the vehicle is called plug-in hybrid. Batteries of plug-in hybrids have to be larger than those of a conventional hybrid vehicle. For short distance trips, plug-in hybrid vehicles can be operated in the electricity-only mode. Plug-in hybrids are not explicitly considered here, but addressed in more detail in Section 7.9. 

---

Figure 7.9 shows a typical portfolio analysis of selected combinations of alternative fuel supply and vehicle drive systems for the period until 2010, based on the assumptions in Table 7.22. 

Electric drive systems have been tried as a means of achieving propulsion without harmful emissions. Currently, most battery-operated vehicles use... 

A current vehicle fuel system designed for evaporative emission control should address enhanced SHED, running loss, and ORVR emission level requirements (see Table 1). A typical vehicle fuel system is shown in Fig. 4. The primary functions of the system are to store the liquid and vapor phases of the fuel with acceptable loss levels, and to pump liquid fuel to the engine for vehicle operation. The operation of the various components in the fuel system, and how they work to minimize evaporative losses during both driving and refueling events, is described below. 

Individual drive motors on each of the vehicle s four wheels allows a fuel cell powered all wheel drive system. Three tanks hold Hy-wire s hydrogen fuel, compressed at 5,000 pounds per square inch. These were developed by Quantum Fuel Systems, the company that developed the industry s first 10,000-psi tanks, which could allow a fuel cell car to have a driving range of 230 miles. 

Figure 13.11. Overview of the differences between the drive system of a fuel-cell powered vehicle and a conventional vehicle (Wengel and Schirrmeister, 2000).

For the following analysis, the investment figures and the selected technologies from MARKAL are an important input. The structure of the investments necessary for a transition to a hydrogen economy is clearly dominated by the expenditures for hydrogen vehicles (see Fig. 18.3). If a hydrogen vehicle is imported, not just the hydrogen drive system will be imported, but very likely the whole vehicle. Therefore,... 

Fuel-cell vehicles contribute to reduced noise pollution, since the drive system is nearly noiseless. This is especially important in urban areas, where the share of noise coming from the drive system is dominant, compared to other noise sources from... 

Today, the power train costs of fuel-cell vehicles are still far from being competitive. They have the largest influence on the economic efficiency of hydrogen use in the transport sector and the greatest challenge is to drastically reduce fuel-cell costs from currently more than 2000/kW to less than 100/kW for passenger cars. On the other hand, fuel-cell drive systems offer totally new design opportunities for... 

Pt is, however, an expensive and limited resource. For a 60 kW fuel cell vehicle, the cost of Pt would be over 2,400 at current cost and loading of Pt. Even worse, replacing combustion engines in all existing vehicles by fuel cell drive systems at no penalty in power would exceed the known reserves of Pt. Catalyst layer design, therefore, strives to reduce the Pt loading markedly at no penalty in the fuel cell voltage. 

NFPA 57 recommends that LNG dispensers be protected from collisions with vehicles and that they incorporate an emergency shut-down system. The maximum delivery pressure of the dispenser shall not exceed the operating pressure of the LNG tanks on the vehicle being refueled, and the LNG delivery hoses must have a shut-off valve at the end and a breakaway valve in the event a vehicle drives off with the refueling hoses attached. Bleed and vent valve must be incorporated into the dispensing lines to allow them to be drained and depressurized prior to disconnection if necessary. 

Figure 2.44. Layout of methanol-to-hydrogen vehicle power system with fuel cell and electric motor. The power controller allows shift from direct drive to battery charging (from B. Sorensen, Renewable Energy, 2004, used with permission from Elsevier).

Vehicle power needs fluctuate over a wide range during normal driving. A hybrid system is effective in achieving maximum efficiency. Figure 4-6 shows system efficiency versus output power for hybrid electric drive systems. 

In general, there are two different architectures for BMSs namely, decentralized systems and centralized systems. These two architectures are illustrated for an electric vehicle (EV) application in Fig. 8.3 (decentralized) and Fig. 8.4 (centralized). In the decentralized system (Fig. 8.3), the individual BMS tasks are located in different devices. The charge control is part of the charger, the discharge control is part of the EV drive system, the battery state determination is carried out within a range meter, and so on. Some BMS tasks must be implemented in more than one device, especially in the case of safety management. Normally, there is little or no communication between the devices, so an optimized operation is not possible. Another disadvantage is that the battery-relevant control functions are located in different devices. Thus, each device must be adapted to the particular battery used. 

Accessory load Item electrical distribution system Provides en ne crank power (6kW for 20s) on demand j Vehicle drives away after 31 days stand... 

Automotive industry, vehicles road, water, air, rail Chassis, exhaust components, drive systems, frames/bodywork members Cross and side members, manifolds, roof rails, spoilers, gear shaft, roof frame profile, engine cradles, inner and outer panels... 

---