A Cost Comparison of Fuel-Cell and Battery Electric Vehicles
Stephen Eaves*
, James Eaves
Eaves Devices, Charlestown, RI, Arizona State University-East, Mesa, AZ
Abstract
This paper compares the manufacturing and refueling costs of a Fuel-Cell Vehicle (FCV)
and a Battery Electric Vehicle (BEV) using an automobile model reflecting the largest
segment of light-duty vehicles. We use results from widely-cited government studies to
compare the manufacturing and refueling costs of a BEV and a FCV capable of delivering
135 horsepower and driving approximately 300 miles. Our results show that a BEV
performs far more favorably in terms of cost, energy efficiency, weight, and volume. The
differences are particularly dramatic when we assume that energy is derived from
renewable resources.
Keywords: Battery-Electric Vehicle; Fuel-Cell Vehicle; Well-to-Wheel; Energy Pathway
*
Corresponding author. Tel.: 401-315-0547; E-mail: stepheneaves@eavesdevices.com
1. Introduction
Both the federal and state
governments have enacted legislation
designed to promote the eventual
widespread adoption of zero-emissions
vehicles. For instance, California enacted
the Zero-Emissions-Vehicle (ZEV)
program mandating automakers to claim
ZEV credits for a small percentage of
total vehicle sales starting in 2003.
Further, the last version of the 2003
energy bill included over a billion dollars
in incentives for automakers to develop
technology related to Fuel-Cell Vehicles.
Currently, the Fuel-Cell Vehicle (FCV)
and the Battery Electric Vehicle (BEV)
are the only potential ZEV replacements
of the internal combustion engine,
however, no studies have directly
compared the two technologies in terms
of performance and cost when
considering the most recent advances in
battery and fuel-cell technology. Below,
we compare BEV and FCV technologies
based on a vehicle model that is capable
of delivering 100 kW of peak power, and
60 kWh total energy to the wheels.1
This
translates into a vehicle that is capable of
delivering 135 horsepower and driving
approximately 300 miles. The vehicle
characteristics are comparable to a small
to midsize car, such as a Honda Civic,
representing the largest segment of the
light-duty vehicle class [1].
We first compare the relative
efficiency of the vehiclesí well-to-wheel
pathways. This allows us to calculate the
amount of energy a power plant must
produce in order to deliver a unit of
energy to the wheels of a FCV and a
BEV. Next, we compute the volume,
weight, and refueling costs associated
with each vehicle. We make these
calculations first assuming that the
hydrogen for the FCVs and the electricity
2
for the BEVs are generated using nonfossil
fuel sources. After, we relax this
assumption to consider the case where
hydrogen is reformed from natural gas
and the electricity for BEVs is generated
using a mix of fossil fuel and non-fossil
fuel sources, such as wind and
hydroelectric, as is the norm today.
2. Analysis and Discussion
2.1. Energy Efficiency Comparison
assuming energy is derived from
renewable resources
A vehicleís well-to-wheel pathway is
the pathway between the original source
of energy (e.g. a wind farm) and the
wheels of the car. The pathwayís
components are the energy conversion,
distribution, and storage stages required
to transport and convert the energy that
eventually moves the automobile. Thus,
analyzing the efficiency of each vehicleís
well-to-wheel pathway allows us to
determine the total amount of energy
required to move each vehicle.
Fig. 1 and Fig. 2 illustrate the
pathways for BEVs and FCVs,
respectively. The first stage of both
pathways is the generation of electricity.
Since presumably we are concerned with
the long-run development of a
sustainable transportation infrastructure,
we first assume that the electricity is
generated by a non-fossil fuel resource
like hydroelectric, solar, wind,
geothermal, or a combination. All of
these sources are used to generate energy
in the form of electricity. The only
established method to convert electricity
to hydrogen is through a process known
as electrolysis, which electrically
separates water into its components of
hydrogen and oxygen.
For BEVs, the electricity is delivered
over power lines to a battery charger.
The battery charger then charges a
Lithium-ion battery that stores the energy
on-board the vehicle to power the
vehicleís drivetrain. In addition to one
storage and two distribution stages, the
BEV pathway consists of two conversion
stages (the conversion of, say, wind to
electricity in stage 1 and the conversion
of electricity to mechanical energy in
stage 2). The figure shows that the entire
pathway is 77% efficient; approximately
79 kWh of energy must be generated in
order to deliver the necessary 60 kWh of
electricity to the wheels of the car.
The FCVís well-to-wheel pathway,
illustrated in Fig. 2, is believed by experts
to be the most likely scenario, with some
exceptions that are addressed below [2].
In this case, the energy from the electric
plant is used for the electrolysis process
that separates hydrogen gas from water.
The hydrogen gas is then compressed
and distributed to fueling stations where
it can be pumped into and stored aboard
individual fuel-cell vehicles. The
onboard hydrogen gas is then combined
with oxygen from the atmosphere to
produce the electricity that powers the
vehicleís drivetrain.
3
Electrolysis
72% Effic.
H2 Storage Fuel Cell Sys. Elec. Drivetrain
89% Effic. 54% Effic.
H2 Gas
Pipeline*
86% Effic.
202 kWh
From Renewable
Source 60 kWh
to Wheels
Vehicle
* ìPipelineî includes losses from compression, expansion, storage and distribution
Fig. 2 ñ Well-to-Wheel Energy Pathway for Fuel Cell Vehicle
Li-ion Batteries
94 % Effic.
Elec. Drivetrain
89% Effic.
79 kWh
From Renewable
Source 60 kWh
to Wheels*
Battery
Charger
89% Effic.
Vehicle
*The BEV regeneration capability reduces the 60kWh requirement by 6kWh while achieving the same range
Power Lines
92% Effic.
Fig. 1 ñ Well-to-Wheel Energy Pathway for Battery Electric Vehicle
In addition to one distribution and one
storage stage, the FCV pathway consists
of four conversion stages (the conversion
of, say, wind to electricity in stage 1, the
conversion of electricity to hydrogen in
stage 2, the conversion of hydrogen back
to electricity in stage 3, and finally, the
conversion of electricity to mechanical
energy in stage 4). Due largely to the
fact that there are two additional
conversion stages relative to the BEV
and the fact that the onboard conversion
stage is only 54% efficient, the FCV
pathway is only approximately 30%
efficient.3
The result is that the pathway
requires the production of 202 kWh of
electricity at the plant, to deliver the
necessary 60 kWh to the vehicle, or 2.6
times the requirements of the BEV
pathway [3]. Obviously, this means that
there would need to be 2.6 times as many
wind farms or solar panels to power the
FCVs versus the BEVs.
Arguably, a more efficient FCV
pathway would be based on-board fossil
fuel reforming or liquid hydrogen
storage. However, attempts at these
alternative methods have proven
uncompetitive compared to a system
based on compressed hydrogen gas. As
a consequence, the pathway illustrated in
Fig. 2 is considered by the DOE and
industrial experts to be the most feasible
[2].
However, contrary to our present
assumption, the DOEís support for the
distribution pipeline of Fig. 2 is based on
the assumption of initially using fossil
fuels as the source of hydrogen. In the
case of renewable energy, it would be
more cost effective to transport the
electricity over power lines and perform
the electrolysis at local ìgas stationsî,
thus eliminating the need for the
expensive and less efficient hydrogen
pipeline [4]. Elimination of the
hydrogen pipeline stage significantly
increases the overall efficiency of the
pathway, however, 188 kWh is still
necessary to deliver 60 kWh to the
FCVís wheels, or 2.4 times the energy
required to power a BEV.
The results of the non-fossil fuel
analysis are impacted by the fact that we
do not consider the cost of constructing
and maintaining a hydrogen
infrastructure. A renewable hydrogen
infrastructure would consist of a network
of electrolysis plants, supported by an
intra-national pipeline, which, in turn,
would supply a myriad of hydrogen
refueling stations. The cost of hydrogen
production from electrolysis is already
well characterized from existing
installations, but accurately projecting
the downstream costs of a massive
transportation and distribution
infrastructure is much more difficult.
The practical implication of only
considering the production costs is that
our estimate of the FCVís refueling cost
is lower than it would be if we
considered infrastructure costs. For
instance, the cost of building the
hydrogen refueling stations alone is
estimated between $100 billion and $600
billion.[5] The U.S. Department of
Energy estimates the costs of the
hydrogen trunk pipelines and distribution
lines to be $1.4 million and $0.6 million
per mile, respectively[6]. A BEV
infrastructure would be largely based on
the current power grid, making its
construction vastly less costly.2
The inefficiency of the FCV pathway
combined with the high capital and
maintenance costs of the distribution
system results in significant differences in
the refueling cost between a FCV and
BEV, particularly if the source is
5
renewable. For example, Pedro and
Putsche [7] estimate that using wind
energy, hydrogen production costs alone
will amount to $20.76 per tank to drive
our FCV 300 miles compared to $4.28
ìper tankî (or per charge) for the BEV.4
2.2. Comparison of Weight, Volume
and Cost
Maintaining the same performance
assumptions, we next compare the
projected relative weight, volume, and
unit costs of each vehicles propulsion
system. The results are reported in Table
1 and Table 2. When interpreting the
tables it is important to note that the
limiting factor in FCV performance is the
amount of power that