Battery Electric Vehicles

As shown in Chapter 4, both homogeneous and heterogeneous energy storage are very important for the future development of HEV/EV. One of the most important storage devices for HEV/EV is the battery. The prospect for widespread introduction of full-performance all-electric vehicles depends on significant advancements of the battery technologies, and the commercial viability of these vehicles depends on a battery cost breakthrough. Advances in electric motors, power electronics, and batteries for automotive applications, which have resulted from the development and production of hybrid vehicles, have renewed interest in the development of battery electric vehicles. However, the cost, low energy density, and required charging time of batteries will continue to constrain the introduction of BEVs. The high-low speed torque performance of electric motors gives the BEV a potential acceleration advantage over conventional internal combustion engine- powered vehicles, and this can be an attractive feature for some customers [2,14, 23]. Battery-operated hybrid car with single motor and two motors are illustrated in Figures 3.2a and 3.2b, respectively [2].

A review of zero-emission vehicle technology commissioned by the California Air Resources Board (CARB) concluded that commercialization (tens of thousands of vehicles) of full-performance battery electric vehicles would not occur before 2015 and that mass production (hundreds of thousands of vehicles) would not occur before 2030 [26, 27]. These projections were based on the continued development of lithium-ion (Li-ion) battery technology leading to reduced cost, higher energy densities, and reduced charging times, all of which allow greater range. They pointed to a possible role for a limited range, city electric vehicle (CEV), which could meet the requirements of a majority of household trips. However, recent BEV introductions suggest that progress in the technology and acceptance of Li-ion batteries may be more rapid than the CARB study concluded [2, 14, 23].

Early commercial application of Li-ion battery technology to vehicles includes the Tesla Roadster, a high-performance sports car. This vehicle, of which about 1,000 have been sold, has a fuel consumption of 0.74 gal/100 miles (energy equivalent basis, EPA combined city/highway). The manufacturer claims a range of 244 miles (also EPA combined city/highway) and a useful battery life of more than 100,000 miles. The base price of $128,000 indicates the continuing problem of battery cost when used in near full-performance vehicles. Tesla announced that it will produce and sell, at about half the price of the Roadster, a five-passenger BEV, the Tesla S, with a range of 160, 230, or 300 miles, depending on optional battery size. Nissan has also announced production of its Leaf EV, a five-passenger car with a range of 100 miles. This vehicle has a Li-ion battery with a total storage capacity of 24 kWh.

FIGURE 3.2 (a) Battery-operated hybrid car with single motor [2]. (b) Battery-operated

hybrid car with two motors [2]

Within the horizon of this study, the most likely future for large numbers of battery electric vehicles in the United States is in the limited-range, small-vehicle market. Range extended electric vehicles (hybrids and PHEVs) are more likely to satisfy the electricity-fueled full-performance—market, from both cost and technological considerations, over the next 15 years [2, 14, 23, 26, 27].

Continuously Outboard Recharged Electric Vehicle (COREV)

Some battery electric vehicles (BEVs) can be recharged while the user drives. Such a vehicle establishes contact with an electrified rail, plate, or overhead wires on the highway via an attached conducting wheel or other similar mechanisms. The BEV's batteries are recharged by this process—on the highway—and can then be used normally on other roads until the battery is discharged. For example, some of the battery-electric locomotives used for maintenance trains on the London Underground are capable of this mode of operation.

Developing a BEV infrastructure would provide the advantage of virtually unrestricted highway range. Since many destinations are within 100 km of a major highway, the BEV technology could reduce the need for expensive battery systems. Unfortunately, private use of the existing electrical system is almost universally prohibited. Besides, the technology for such electrical infrastructure is largely outdated and, outside some cities, not widely distributed. Updating the required electrical and infrastructure costs could perhaps be funded by toll revenue or by dedicated transportation taxes.