The results from Chapter 5 demonstrate that the combination of large-scale adoption of
electric-drive vehicles and a low-carbon electricity supply are a promising strategy to
help California achieve its aggressive GHG reduction goals in the light-duty
transportation sector, even with likely growth in population and travel demand. On a unit
emissions basis, both PHEV/BEV and FCV scenarios show significant GHG emissions
reductions compared to conventional gasoline ICEVs – 35 to 42 percent of baseline
ICEV emissions. The results are partly attributable to the increased energy efficiency of
the vehicle technologies, and partly due to the lower carbon of the fuel, driven by large
increases in renewable electricity. One key finding is that the mix of renewable energy
resources does not greatly influence the results. In the scenarios considered, the
renewable energy supply portfolios that rely more heavily on resources from neighboring
states are more wind-intensive, whereas the instate resources portfolio is dominated by
solar power. Despite the daily and seasonal difference in the availability of wind and
solar power, on an annual basis, all three renewable portfolios yield fairly similar
emissions results for the range of vehicle technology and fuel production profiles
considered. Perhaps the most significant consideration in terms of the renewable
electricity supply is that the instate resources portfolio is not large enough to meet the
renewable energy requirements for large fleet penetrations of FCVs and perhaps PHEVs
or BEVs if California were to pursue a more aggressive RPS target higher than 33
percent. Clearly, the decision to pursue a large fleet of electric-drive vehicles in
California may have policy impacts with regards to how much of California’s renewable
energy can come from within California. Moreover, if neighboring states decide to pursue
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either more aggressive renewable energy goals, or pursue large fleets of EVs, California’s
access to a large low carbon fuel supply may be limited.
While the unit GHG emissions results attributable to PHEVs, BEVs and FCVs are
attractive, perhaps a more important metric are total emissions from light-duty vehicles,
which reflect the impacts of population growth and increases in VMT that California will
likely face over the next few decades. The scenario results demonstrate that the AB 32
goal of reducing total GHG emissions 80 percent below 1990 levels may be attainable in
the light-duty transportation sector if the right measures are put in place. My results show
that a light-duty vehicle fleet comprised entirely of EVs combined with a 50 percent
renewable electricity supply and a 32 percent reduction in VMT can yield total emissions
that are as much as 70 percent below 1990 levels. While this does not quite reach the AB
32 goal it serves as a good indication of the magnitude of changes that might need to take
place in the transportation sector to achieve this result. It also illustrates some of the
policy choices and technologies that might be needed for this result to be achievable. The
best emissions results involve PHEV and BEV charging using the minimize fossil supply
and the offpeak and constant hydrogen fuel production profiles. All three of these fuel
production profiles involve purposely producing electricity or hydrogen during hours
when there is an abundance of renewable electricity available. Without targeted policy
intervention and smart grid technology, there is no guarantee that vehicles will be
charged or hydrogen fuel will be produced at the most optimal times from an emissions
perspective.
The emissions benefits of grid energy storage in relation to fueling EVs are somewhat
inconclusive and require further study. I model grid-energy storage in a relative simplistic
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way, and focus on using storage to produce an electricity supply that follows non-vehicle
demand. This approach is beneficial in terms of investigating how to reduce emissions
from the electricity grid as a whole, by optimizing the use of more efficient fossil
generation resources, however a different approach is needed to better understand
interactions with electricity demand from vehicles. A future analysis might involve
shaping the electricity supply to reflect the timing of electricity demand from EVs as well
as non-vehicle demand.
Another area that requires further study is hydrogen production. In my analysis, I focus
on distributed onsite hydrogen production at a fueling station, using the electricity grid,
but this is not the only option being considered for renewable hydrogen in California.
Since hydrogen can be produced and stored in one location and transported to a fueling
station for later use, an alternative option is to produce renewable hydrogen via
electrolysis directly at a wind power plant. There are two potential advantages to this
approach that are worth investigating:
1. Hydrogen can be produced whenever wind power is available, which often occurs
during the night when electricity demand is low. In theory, this would increase the
utilization of a wind power plant, making the investment more attractive and
potentially lowering the cost of fuel production.
2. Unlike grid-electrolysis-based hydrogen production, all of the electricity used to
produce and store hydrogen will be from a renewable resource with no GHG
emissions, although there are some GHG emissions associated with delivering the
hydrogen to a fueling station, if transported via truck rather than pipeline.
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Another hydrogen production pathway that has already been investigated by others is
biogasification of biomass waste, In a recent study, Parker et Al. investigate the benefits
of using California’s biomass resource to produce hydrogen fuel, with fuel cost estimates
in the range of $3.50 to $5.50 per kg H2 and a 90 percent reduction in WTW GHG
emissions, compared to conventional ICEVs [74]. An interesting study might involve
comparing emissions, fuel costs and resource availability for all three hydrogen
production pathways for the fuel demand scenarios explored in this thesis.
In terms of fuel production costs, the results shown in this thesis are encouraging. Both
electricity and hydrogen show production cost estimates in the range of $0.04/mile to
$0.08/mile that are cost-competitive with gasoline, especially for PHEVs and BEVs. In
part, this is due to the fuel economy assumptions used for EVs, but it is also attributable
to the fact that electricity is a less expensive energy resource than oil. Additional work
remains in the area of cost analysis too. A more extensive cost analysis should include the
cost of vehicle technologies to enable a complete lifecycle comparison of PHEVs, BEVs
and FCVs as well as gasoline ICEVs and conventional gasoline HEVs. This would
provide a more complete picture of the cost considerations to transition to a large EV
fleet in California.
While further analysis is needed, this thesis does provide some key insights into the
emissions and cost impacts of fueling electric-drive vehicles with low carbon electricity
and hydrogen, which will likely play an increasingly important strategic role in helping to
meet California’s ambitious environmental goals in the transportation sector.