Environmental Engineering Reference
In-Depth Information
TABLE 8.3
2000 Model Year Electric Vehicle Characteristics
Manufacturer
GM
GM
Toyota
Chevrolet
Ford
Ford
Model
EV1
EV1
RAV4
S-10
Ranger-EV Ranger-EV
Size
Two-passenger Two-passenger Five-passenger
Pickup
Pickup
Pickup
Battery Type
Lead Acid
NiMH
NiMH
Lead Acid Lead Acid
NiMH
Maximum electric
power (kW)
102
102
50
85
67.2
67.2
Vehicle mass (t)
1.4
1.32
1.56
2.24
2.13
1.86
Frontal area (m
2
)
1.8
1.8
1.95
Battery mass (kg)
595
521
621
Battery energy
storage (kWh)
18.7
26.4
16
23
Vehicle range (km)
89-153
121-209
201
64-89
123
145
Charge time (h)
5.5-6
6-8
6-8
6-7
Urban/highway energy
efficiency (km/MJ)
1.72/1.60
1.32/1.49
1.18/1.02
1.12/0.99
Urban/highway equivalent
fuel efficiency (km/L)
a
16.3/15.1
12.5/14.1
11.2/9.7
10.6/9.4
Battery/vehicle mass
0.425
0.395
0.318
Power/mass (kW/t)
56.7
56.7
32.1
43.6
31.5
36.1
Battery energy/mass (Wh/kg)
31
51
26
Battery energy/maximum
power (h)
0.18
0.26
0.19
a
Assumes 30 % equivalent engine thermal efficiency, or 9.48 MJ/L.
depleted batteries can be recycled to recover battery materials.
18
Battery replacement will cost
several thousand dollars every 50,000 miles.
The battery mass of these vehicles constitutes about 40% of the vehicle mass, implying a
very large vehicle mass penalty to the vehicle energy efficiency. Indeed, if we convert the vehicle
electric energy efficiency of 1.0-1.7 km/MJ to an equivalent fuel efficiency of 10-16 km/L (see
Table 8.3), then these vehicles are only slightly more efficient than current vehicles of comparable
mass listed in Table 8.2. Despite the recovery of braking energy, the electric vehicles are unable to
achieve higher fuel efficiency than comparable conventional ones.
The power/mass ratios of these vehicles, which lie in the range of 30-55, are only half those
of conventional vehicles (Table 8.2), limiting their acceleration and grade climbing abilities.
The limited range and fuel efficiency of current battery-powered electric vehicles is tied to the
low energy storage densities of currently available batteries, about 25-50 Wh/kg (90-180 kJ/kg).
But other electrical storage systems being developed, such as electric capacitors and flywheels,
have no higher energy storage densities (see Table 4.1), and other types of high-density storage
18
In a lead-acid battery, the electrolyte sulfate ions are deposited on the surfaces of the electrodes during battery
discharge. This process is not entirely reversed upon recharge, gradually leading to the loss of electrode active
surface area and the energy storage capacity of the battery with each recharge cycle.
