reflects those plants that will be dispatched during the night over and above the normal nighttime
baseload.
Second, EV per-mile electricity consumption is important in determining per-mile EV emissions
and net emissions reductions. Although existing EV technologies have relatively high per-mile
electricity consumption and fuel-cycle emissions, future, more efficient, EV technologies may well
lead to substantial reductions in EV electricity consumption and corresponding improvements in
the emissions “balance” between EVs and competing gasoline vehicles.^38
Third, the level of emission control in power plants is a key determinant of EV fuel-cycle
emissions. Eventually, old power plants with fewer controls will be retired, and new plants that
are subject to stringent emission requirements will come into service with low emissions. Thus,
future EVs will automatically have lower fuel-cycle emissions.
Finally, the estimates of gasoline vehicle (GV) emissions are critical. Most past studies of EV
emissions impacts used either emission standards or computer model-estimated emissions to
represent GV emissions. It is well known now that emission standards and most previous
estimates of on-road emissions are substantially lower than actual on-road emissions. Use of low
baseline GV emissions will cause underestimation of EV emission reductions. OTA used an
existing computer model--EPA’s Mobile5--to project gasoline emissions, and our estimated
gasoline vehicle emissions are likely to be somewhat low. Another problem with some past studies
was the use of gasoline vehicles for comparison that were relatively inefficient, and thus had
correspondingly high-fuel-cycle emissions. This analysis compares EVs with gasoline vehicles that
are identical to the EVs except for their powertrain and energy storage, that is, EVs with
aluminum bodies are compared with gasoline vehicles with aluminum bodies.
Using a fuel-cycle model developed for the project,^39 OTA evaluated and compared the fuel
cycle emissions of EVs and the corresponding advanced conventional vehicles sharing the same
efficiency characteristics (except powertrain). In calculating GV emissions, the federal Tier 2
standards are assumed to be implemented. For EVs a national electric generation mix is used,
assuming most recharge will occur at night and use surplus off-peak (baseload or intermediate)
power.^40 The use of the national mix here certainly underestimates EV emission benefits in areas
like California that have relatively clean power.
The 80 to 100-mile range 2005 MY EV technologies, using lead acid and Ni-MH battery
technology, almost eliminate emissions of HC and CO, and achieve 50 percent to 70 percent
reductions in emissions of very fine particulate, PM10.^41 These high PM10 emission reductions,
which are different from the results in many previous studies, are owing to the very high GV fuel
(^38) Batteryresearch is aiming to improve substantially the charge/recharge efficiency and specific energy (energy storage per unit of weight) of EV
batteries both of which will have a great impact on EV energy requirements and emissions (better energy storage will yield a lighter, more efficient
vehicle if range is unchanged). 39
M.Q. Wang, Argonne National Laboratory, "Fuel-Cycle Energy Requirements and Emissions of Advanced Automotive Technologies," draft
prepared for the Office of Technology (^40) Assumed generation mix: coal, 50 percent; natural gas, Assessment, July 5, 1995.30 percent; nuclear, 10 percent; oil, 5 percent; and hydropower, 5 percent. This mix
reflects theassumption that much nuclear and hydropower generation capability is already fully subscribed and will not be available for dispatch to
recharge EVs 41
PM10 refers to particulate matter below 10 microns in diameter, that is, fine particulates.