Incremental prices (relative to the advanced conventional vehicles) for the mid-size series
HEVs are as shown in table 4-15, for the different energy storage devices. The bipolar lead acid
battery is the cheapest solution, as both flywheel and ultracapacitor are relatively expensive for
energy storage, which becomes a limiting constraint in our analysis. By 2015, costs are very low
because large cost savings are realized from eliminating the advanced DISC engine and
continuously variable transmission (CVT).^69 The subcompact car price will increase by about 80
percent of the costs shown above, compact vans by 110 percent, and standard pickups by 140
percent.
Prices for parallel hybrids are only slightly lower than those for a series hybrid, but OTA did
not estimate them in as much detail. Costs are lowered for the Case 1 type hybrid owing to the
absence of a separate generator, and the use of a small flywheel energy storage system, but are
increased by the need for a larger engine and transmission. In Case 2, the engine size is similar to
that of the series hybrid, as is the battery size. The motor is smaller, and the vehicle does not need
a separate generator, but this is partially offset as a transmission is not eliminated. Hence, we
expect costs to be similar to that for a series hybrid, but they may be slightly lower depending on
the specific strategies chosen. The same scaling laws should apply for the different classes within
the range of accuracy of this analysis.FUEL CELL VEHICLESTwo types of fuel cells are considered in this section, the zinc air cell and the proton exchange
membrane (PEM) cell fueled with methanol. The zinc air cell is very much like a high specific
energy/low specific power battery, so that all of the equations derived for EVs (see appendix A)
are directly applicable. The PEM/methanol fuel cell is power limited, not energy limited, because a
regular gasoline tank size can carry enough methanol for a range of over 300 miles. Hence, PEM
ceils can be sized according to requirements for short-term peak power (that is, rapid
accelerations) or maximum continuous power (long hill climbs). In the latter case, the
PEM/methanol cell will require additional electric storage in the form of a flywheel, battery, or
ultracapacitor to provide an occasional power boost, and this combination is sometimes called a
fuel cell hybrid.The zinc-air fuel cell has a high specific energy of over 200 Wh/kg, but a low specific power of
less than 100 W/kg. The vehicle power requirements demand either a very large fuel cell, or a
smaller cell coupled with a peak power device such as an ultracapacitor or flywheel. As is true of
the hybrid vehicle, the issue of ultracapacitor sizing for repeatability of acceleration performance
is an important consideration. A second consideration is the 6 percent grade-climb requirement,
which defines the continuous power requirement of 30 kW/ton. Because the zinc air cell has such
a low specific power, the cell weight needed to provide even the continuous power requirement is
too high, and the cell too expensive, for commercial viability in 1995 and 2005. However, the(^69) The benefits of the DISC engine areessentially negated by the series hybrid configuration, since the engine operates close to its moat efficient
point at all times, and the DISC technology improves part load efficiency. Consequently, a less expensive engine will give the same efficiency. The
transmission is not needed in the hybrid configuration.