reductions in vehicle body weight by 2015 make it possible to meet the 6 percent grade climb
requirement with a zinc-air cell of reasonable size.OTA’s analysis shows that the (mechanically recharged) zinc-air fuel ceil can provide a 200-
mile range and reasonable performance--but not the capability for a sustained 60 mph, 6 percent
hill climb--for a car (subcompact) price increment of less than $10,000 in 2005 (see table 4-16).
This, of course assumes that a zinc reprocessing infrastructure is developed. The zinc-air system’s
inability to sustain the 6 percent grade climb specified for EVs, however, implies that a direct
comparison with a battery-powered EV would be unfair. The zinc-air fuel cell becomes even more
cost effective with incremental prices in the range of $8,700 to $11,900 for cars and $13,000 to
$19,000 for trucks by 2015, while providing a 200-mile range and being able to sustain a 6
percent grade climb.The zinc-air fuel cell or battery is “recharged” by mechanically replacing the electrolyte and zinc
anodes, so that a zinc refueling infrastructure must be developed; no estimate of the refueling
infrastructure costs and zinc reprocessing facility requirements are included here. The vehicle
energy consumption estimates shown in table 4-16, however, take into account the electric energy
efficiency of the zinc-processing facility.Use of zinc-air fuel cell vehicles may be limited from a practical standpoint to commercial,
centrally fueled fleets. It is not clear that the cells can be “topped off, ” which makes their range
limitations onerous for private users. Moreover, the air handling systems that scrub intake air free
of carbon dioxide may require frequent maintenance, which is impractical for such users.In evaluating PEM fuel cell vehicles, we have assumed that the fuel cell can be packaged to fit
into a car without interfering with passenger or trunk space. Such an assumption is necessary
since current fuel cells, even those powered by hydrogen, are quite large in volume.OTA does not expect that a PEM fuel cell for light-duty vehicles can be commercialized
by 2005. The vehicle evaluated for 2015 uses a fuel cell sized to provide the continuous power
requirement of 30 kW/ton, while ultracapacitors or batteries are used to provide peak power
requirements of 50 kW/ton. Fuel cells attain maximum efficiency at about 40 to 50 percent of
maximum power, so that the most efficient operating strategy is to operate much as an engine-
powered hybrid that operates near its optimum bsfc point, unless high continuous power is
required. Two vehicles are examined, one using a semi-bipolar lead acid battery for peak power
and cold-start energy storage, and the second using an ultracapacitor; in both cases, body
materials, aerodynamics, and rolling resistance correspond to the 2015 (m) scenario for vehicle
technology.Table 4-16 shows the results for a mid-size car, for the two cases. The ultracapacitor is sized to
provide about one minute of peak-power availability and is, therefore, energy storage limited.
Nevertheless, the two scenarios provide nearly equivalent results in all areas except one--the
battery offers superior range as an EV or in cold-start conditions. Costs are highly dependent on
the fuel cell/reformer cost. At $650 per kW for the combination, the incremental RPE for the fuel
cell vehicle over a 2015(m) conventional mid-size vehicle is close to $40,000. Even at $65/kW,
the incremental price is $4,500 to $5,000. Fuel economy has increased to the low 80 mpg range in
gasoline equivalent terms. This is in line with the fact that a methanol-PEM cell is not substantially