Fuel Cells vs Batteries
In the Automotive Sector
Dr. Jeffrey Wishart
Senior Project Engineer, Intertek Transportation Technologies
The following paper will provide an overview of pros and cons of both fuel cells
and batteries and their place in the automotive landscape.
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Fuel Cells vs Batteries
In the Automotive Sector
Contents
Introduction ..........................................................................................................................3
The Benefits of Fuel Cell Vehicles ......................................................................................3
The BEV Advantage ............................................................................................................9
Competing or Complementary Technologies? ........................................................... 11
Fuel Cell Vehicles for the Masses .................................................................................... 13
A Place for FCHEVs and BEVs .......................................................................................... 15
Intertek Fuel Cell and Battery Testing Activities ............................................................ 17
Contact Us ......................................................................................................................... 18
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Fuel Cells vs Batteries
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Introduction
If you follow the alternative fuel industry at all, you may have heard this little pearl
of “wisdom”: Fuel cells are a technology of the future…and always will be. On the
other hand, battery electric vehicle (BEV)
supporters claim that are BEVs represent the
automotive future and, by the way, can be bought
today.
Fuel Cells are the technology
of the future…
-Or-
The EV forums are full of comments that fuel cells
will never be a part of the transportation system,
and that any money spent on fuel cell
…Any money spent on fuel
cell development is good
money thrown after bad.
development is good money thrown after bad. To
be fair, fuel cells have seemed to be on the cusp of
Which one is right?
commercialization in vehicles several times in the
past, only to famously fail to take hold - the last time being in the mid-2000s.
The Benefits of Fuel Cell Vehicles
To be fair, fuel cells do have strengths that can’t be ignored. For one thing, unlike
conventional batteries, the reactants (the chemicals that are needed for the
electrochemical reaction that produces electricity) are external, meaning that as
long as the reactants continue to be fed to the fuel cell, electricity can be
produced. Moreover, refueling an empty reactant tank is also much faster than
recharging a battery.
There are several different types of fuel cells, including alkaline fuel cells (AFCs),
direct methanol fuel cells (DMFCs), phosphoric acid fuel cells (PAFCs), molten
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Fuel Cells vs Batteries
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carbonate fuel cells (MCFCs), and solid oxide fuel cells (SOFCs). However, proton
exchange membrane (also known as polymer electrolyte membrane, or PEM) fuel
cells are seen as the most viable for vehicular applications for the following
reasons (the other fuel cell types have some, but not all, of these characteristics):
1. The electrolyte is solid, and so leaking of corrosive fluids is not an issue
and the fuel cell can operate in any orientation.
2. The operating temperature is relatively low (80-100°C, 176-212°F),
meaning start-up times are short.
3. Relatively high power density (compared to other fuel cell types).
4. 99.999% H2 is required, but air can be used to supply the required O2.
The PEM fuel cell (PEMFC) uses hydrogen and oxygen gases as its reactants. The
oxygen gas is simply extracted from the surrounding air. Hydrogen gas serves as
the “fuel” of a PEMFC, and when compressed, it is much more energy dense than
even the most advanced batteries (in both a volumetric and gravimetric sense).
This means that for a given volume and mass, more energy is contained - well
beyond what batteries are expected to achieve for the foreseeable future. As
shown in Figure 2, gasoline is a very efficient energy carrier and a lot of energy is
concentrated in a low volume with low weight. Compressed hydrogen gas is
much less efficient; however, it’s still more than an order of magnitude better than
the specific energy and energy density of the Li-ion battery pack (or more
accurately, energy storage system (ESS) of a representative BEV, the 2013 Nissan
Leaf.
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Figure 1. Typical specific energy and energy density of gasoline, an H2 storage tank,
and a Li-ion ESS
Sources:
Gasoline: Based on Shell Plus 89 at 15 degrees C: 42,900 kJ/kg, 0.74616 kg/L from Shell Ecomarathon rules, 2014: http://s01.static-shell.com/content/dam/shellnew/local/corporate/ecomarathon/downloads/pdf/sem-global-official-rules-chapter-1-2014.pdf
Hydrogen Tank: Based on values from Table 6.21, page 220 of A. Godula-Jopek, W. Jehle, and J.
Wellnitz (2012). Hydrogen Storage Technologies, New Materials, Transport and Infrastructure,
John Wiley & Sons.
Li-ion ESS: Based on 2013 Nissan Leaf ESS, 24 kWh, 275 kg and 485 L, from "First Responder's
Guide" from Nissan website:
(https://owners.nissanusa.com/nowners/navigation/manualsGuide?model=Nissan+LEAF&year=20
11)
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Fuel Cells vs Batteries
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One of the main drawbacks of a BEV is that the limited energy capacity of
batteries means that the vehicle range is less than that of a conventional vehicle.
With the ability to carry more energy on-board the vehicle, the advantages of a
fuel cell vehicle (FCV) start to become apparent.
The FCV can achieve a much longer range with an
on-board hydrogen gas tank, making the FCV range
competitive with conventional and hybrid vehicles.
For example, the Hyundai Tucson Fuel Cell was
recently driven for 435 miles in a mix of city and
highway driving (at an average speed of 47 mph)
though three Scandinavian countries. This real-world
range approaches that of incumbent internal
The real-world range of
FCVs approach that of
incumbent internal
combustion engine (ICE)
vehicles, making a FCV
potentially more palatable to
the mass-market vehicle
consumer.
combustion engine (ICE) vehicles, making a FCV potentially more palatable to
the mass-market vehicle consumer. A comparison of sport utility vehicles (SUV)
with a spark ignition (SI), compression ignition (CI, or diesel), SI hybrid electric
vehicle (HEV), FCV, and BEV powertrains, respectively, is shown below in Figure 3.
While the range of the FCV is clearly less than that of the conventional vehicles or
even that of the HEV, it is more than twice that of the BEV.
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Fuel Cells vs Batteries
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* Estimate
Figure 2. EPA ranges of an SI vehicle, CI vehicle, SI HEV, FCV, and BEV
Source: Fueleconomy.gov
Powertrain Specifications: Tucson: 2.4 L, 4 cyl, Auto
GLK250: 2.1 L, 4 cyl, Auto, Turbo
Highlander: 3.5 L, 6 cyl, Auto
Fuel Cell: 100 kW Induction Motor, 24 kW ESS, 100 kW PEMFC
RAV4: 115 kW Induction Motor, 41.8 kWh ESS
Another drawback of a BEV is the time needed for recharging. Using the fastest EV
charging available, the Tesla Supercharger network (boasting a rate of 120 kW),
means that a Model S with the largest battery pack (an industry-leading 85 kWh)
would require at least 40 minutes for a full charge from full depletion. Meanwhile,
the FCV can be refueled in about the same time as a conventional vehicle -
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Fuel Cells vs Batteries
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approximately five minutes. As shown in Figure 4, the refueling times of an FCV are
comparable to the incumbent conventional vehicle, while BEV recharging is
significantly (and some might say unacceptably) longer. The time required to
recharge a BEV on a DC fast charger (DCFC) with a power rating of 60 kW (the
rate of most DCFCs outside of the Supercharger) is provided to the 80% state of
charge (SOC) mark. The reason is that since the charging rate of most BEVs slows
considerably at the 80% mark, and further, the vehicle often ends the charge
event at this mark and a second, top-off charge must be completed to obtain an
SOC of 100%.
Figure 3. Approximate time to refuel/recharge a conventional vehicle, an FCV, and a BEV
with a 24 kWh pack and 6.6 kW on-board charger (at an AC L2 rate and a DC fast
charging rate to 80% SOC)
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Fuel Cells vs Batteries
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The fuel cell and hydrogen community around the world has agreed upon a
refueling standard, SAE J2601. Unlike the BEV industry, where there is one AC
charging standard and two official DC fast charging standards plus Tesla’s
proprietary technology in the US - not to mention the different standards in China
and Europe - refueling will be the same everywhere. The “VHS vs. Betamax”
standards wars that are currently plaguing the BEV industry can be avoided
altogether for FCVs.
It must be said, however, that there are not currently many hydrogen refueling
stations around the country–the DOE counts only 10 publicly accessible stations,
but many more are in development: California, for example, plans to have 68
stations in operation by 2016.
The BEV Advantage
This is not to say that BEVs don’t have advantages over FCVs. The efficiency of a
BEV is unsurpassed, and it will always take more energy to get from point A to
point B in an FCV. The most efficient production BEV currently available is the 2014
Chevrolet Spark EV, shown below in Figure 5, which achieves an EPA rating of 260
Wh/mile City/310 Wh/mile Highway/280 Wh/mile Combined (equivalent to 128
MPGe City/109 MPGe Highway/119 MPGe Combined). The higher efficiency is
due to the electrochemical reaction in batteries being more efficient than the
reaction in a PEMFC but also because the PEMFC requires a balance of plant
(BOP) system that delivers the external reactants to the reaction sites. The
efficiency of the PEMFC is increased dramatically with higher reactant pressure,
and the air compressor consumes the most energy of the BOP components,
thereby reducing the efficiency the most. (The H2 is already compressed in the H2
tank.)
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Fuel Cells vs Batteries
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Figure 4. 2014 Chevrolet Spark EV, the most efficient production EV currently available
Source: http://www.engadget.com/2012/11/27/chevy-details-2014-spark-ev/
The BEV is also simpler technology that does not cost as much to build. In fact, for
a commuter or city car, and especially for a driver that never needs to drive very
far and can charge their EV in the garage at night, a BEV is very tough to beat.
As shown in Figure 6, the efficiency spectrum ranges from conventional vehicles to
EVs, with FCVs somewhere in the middle but more efficient than even hybrid
electric vehicles (HEVs). The efficiency is given as the “tank-to-wheel” (TTW)
efficiency, which ignores the efficiency of the fuel and/or electricity extraction,
refining, and delivery to the vehicle; including these losses would allow for a “wellto-wheel” (WTW) efficiency calculation.
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Fuel Cells vs Batteries
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Figure 5. Approximate TTW efficiencies of conventional vehicles (both SI and CI), an SI
HEV, an FCV, and a BEV
Source: Helmers and Marx Environmental Sciences Europe 2012, 24:14 (adaptation)
http://www.enveurope.com/content/24/1/14
Competing or Complementary Technologies?
It is apparent that with current technology, BEVs and FCVs are both imperfect
replacements for conventional vehicles in some ways, and expecting either to
become the dominant transportation propulsion technology is far from a sure bet:
BEVs have range and recharging limitations, while FCVs boast an efficiency that is
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Fuel Cells vs Batteries
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higher than ICE vehicles but do not offer a large enough gain to overcome the
higher purchase price and lack of hydrogen refueling infrastructure.
It should be noted that the FCVs that are being commercialized are really
hybridized designs that use a battery as well as a fuel cell. The reasons for this
hybridization are that without an ESS, the FCV cannot capture regenerative
braking energy—a distinct efficiency advantage of a vehicle with an electric
motor—and the slow responsiveness of the PEMFC would make vehicle transients
less dynamic than desired by vehicle consumers.
For FCVs to recapture regenerative braking energy, the PEMFC system would
have to also work in reverse as an electrolyzer to split water into H2 and O2. This
would require a source of water on board the vehicle that could be pumped
through the fuel cell. This water source would take up space and could become
depleted over long trips, and would also need to be replenished. Obtaining water
exiting the cathode of the fuel cell would add to system complexity, and
obtaining it from an off-board source requires extra plumbing. A method for
eliminating the produced O2 would also be required. More problematic would be
how to store the produced H2, which would be at a much lower pressure than the
H2 stored in the tank, and thus would have to be pressurized. This would require
some time in which hydrogen exiting the tank for propulsion would not be
possible. Regenerative braking performed by the fuel cell would therefore be less
efficient and make the vehicle less responsive than regenerative braking by
batteries.
The responsiveness of an FCV without an ESS is exacerbated by the lower transient
capability of the PEMFC, and an ESS as a buffer is highly advantageous: It is faster
to get current from the ESS than it is to (1) draw hydrogen from the tank and (2)
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Fuel Cells vs Batteries
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supply air to the fuel cell to (3) produce the equivalent electricity in a PEMFC to
power the electric motor that propels the vehicle.
As a result, the FCVs that are coming to market can actually be classified as fuel
cell hybrid electric vehicles, or FCHEVs. An on-board battery to support the PEMFC
provides the quick response required - and desired - by drivers. In fact, it is unlikely
that FCVs will be built without energy storage. Even better, they can be designed
as plug-ins that can drive on pure electricity for a portion of the range to tap into
that high battery efficiency. Thus, having a battery paired with a PEMFC in an
FCHEV makes the vehicle more responsive and more efficient. In this way, fuel
cells and batteries become complementary - and not competing – technologies.
Fuel Cell Vehicles for the Masses
The commercialization of FCHEVs is certainly not following a straight line path, and
has occurred in fits and starts up to this point. There are several reasons for this
delay:

Fuel cell performance has been lacking

The fuel cell system is too expensive

Hydrogen storage technology performance is insufficient

Hydrogen production pathways have not developed

Hydrogen refueling stations have not materialized
The technological performance issues are currently being addressed by the
industry as well as by a renewed interest in fuel cells and hydrogen research by
the US Department of Energy. Governments at various levels are also working on
the infrastructure issues. Refueling station projects are being funded in clusters to
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Fuel Cells vs Batteries
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promote FCHEV adoption in certain metropolitan areas (especially in California) in
advance of FCHEV deployment. Furthermore, there is support for cutting-edge
research into hydrogen production via algae and other biological pathways.
Interest in fuel cells never waned in Asia and Europe in the same way as in North
America circa 2008, shown by growing infrastructure in both areas. There were 17
public stations in Japan at the end of 2012, with plans to build 19 more in 2013 and
hit the 100-station mark by 2015. There are currently 15 public stations in Germany,
with plans for 400 by 2023.
A lot of work is being done to remove the roadblocks and the industry as a whole
has made considerable progress since the last failed attempt at
commercialization. The automotive companies, for their part, have been forming
partnerships to pool resources and reduce R&D costs. Some of these partnerships
include agreements between GM and Honda, Ford-Renault-Nissan-Daimler, as
well as Toyota and BMW.
Several companies, including Hyundai, Toyota, Nissan, and Kia targeted 2015 as
the year for FCHEV commercialization, with projected vehicle sticker prices of
around $50,000. Hyundai has already begun leasing its Tucson Fuel Cell vehicles
with an expected production run of 1,000 cars. Toyota is rumored to be beginning
sales or leases by the end of 2014. (The Honda FCX Clarity, shown below in Figure
6, has been available since 2008, but only as a lease vehicle for $600 a month,
and only in Southern California where there is access to public hydrogen stations.)
Other automakers such as Daimler, BMW, Ford, and GM aim to introduce FCHEVs
in the marketplace later in the decade.
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Fuel Cells vs Batteries
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Figure 6. Honda FCX Clarity, available for lease in California since 2008
Source: http://automobiles.honda.com/fcx-clarity/
A Place for FCHEVs and BEVs
FCHEVs and BEVs can and should co-exist, with each fulfilling its particular niche.
BEVs are ideal commuter cars and for use in many commercial applications with
repeatable routes, while FCHEVs are suitable for drivers that frequently need to
drive longer distances. FCHEVs are also good candidates for larger vehicles like
long-haul trucks and buses. AC Transit in the Bay Area has been using fuel cellpowered buses for 13 years, traveling over 750,000 miles. BC Transit in British
Columbia purchased the world’s largest fleet of fuel cell-powered buses (20) in
2009 for use at Whistler in time for the 2010 Winter Olympics, one of which is shown
below in Figure 7.
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Figure 7. Fuel cell bus, one of 20 purchased by BC Transit in advance of the 2010
Vancouver Winter Olympics
Source: http://smg.photobucket.com/user/billlmf/media/BC%20Transit%20H40LFR/1002_4.jpg.html
Unlike conventional, hybrid, and even plug-in hybrid electric vehicles currently on
the market, both BEVs and FCHEVs have zero emissions “at the tailpipe.” This
makes reducing and eventually eliminating both greenhouse gas and air
pollutants from the transportation system easier because it’s more cost-effective
to “green” centralized power plants and hydrogen production facilities than
individual fossil fuel-burning cars.
While BEVs are currently ascendant and FCHEVs have disappointed in the past,
many believe that FCHEVs are a technology whose time will come. Is that time the
present, with the introduction of the 2015 Hyundai Tucson Fuel Cell, shown below
in Figure 8, marking the beginning of the FCHEV era? It is still unclear. In the
meantime, it is important to continually increase R&D funding and focus on
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making any advanced technology vehicle introduced have the performance
and efficiency needed to get the public excited, as well as invest in the refueling
and recharging infrastructure required to meet the public’s driving needs.
Figure 8. Hyundai Tucson Fuel Cell, made available for lease in June, 2014
Source: https://www.hyundaiusa.com/tucsonfuelcell/
Intertek Fuel Cell and Battery Testing Activities
Intertek is technology agnostic when it comes to advanced vehicle powertrain
technologies, and the company’s laboratories are highly engaged in testing and
certification of both fuel cells and batteries of all types around the world.
Intertek’s testing services include testing and certification of both power sources
from micro fuel cell systems and battery cells with power in the mW range to large,
stationary systems at the MW scale to electrolyzers and battery management
systems. Intertek provides services to test against international and national
standards such as SAE, IEC, and ANSI/CSA standards. Intertek also performs
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Fuel Cells vs Batteries
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customized testing that measures electrical and safety performance, as well as
environmental and abuse testing. Intertek’s technical experts have many years of
experience of working with fuel cells and batteries and can provide advisory
services such as regulatory requirement analysis, technical due diligence, safety
analysis, modeling and simulations, technology road mapping, manufacturing
facility inspection and certification, and courses and training. For more
information, visit the automotive division website at
www.intertek.com/automotive.
Contact Us
If you would like to connect with an expert to answer your questions, or obtain a
quote for a new project, contact Intertek at 1-800-WORLDLAB or
icenter@intertek.com.
Intertek is the leading quality solutions provider to industries worldwide. From
auditing and inspection, to testing, training, advisory, quality assurance and
certification, Intertek adds value to customers’ products, processes and
assets. With a network of more than 1,000 laboratories and offices and over
35,000 people in more than 100 countries, Intertek supports companies’ success in
a global marketplace. Intertek helps its customers to meet end users’ expectations
for safety, sustainability, performance, integrity and desirability in virtually any
market worldwide.
This publication is copyrighted by Intertek and may not be reproduced or transmitted in any form in
whole or in part without the prior written permission of Intertek. While due care has been taken
during the preparation of this document, Intertek cannot be held responsible for the accuracy of the
information herein or for any consequence arising from it. Clients are encouraged to seek Intertek’s
current advice on their specific needs before acting upon any of the content.
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