Section B8
Paper 30
Disclaimer—This paper partially fulfills a writing requirement for first year (freshman) engineering students at the University
of Pittsburgh Swanson School of Engineering. This paper is a student, not a professional, paper. This paper is based on publicly
available information and may not provide complete analyses of all relevant data. If this paper is used for any purpose other
than these authors’ partial fulfillment of a writing requirement for first year (freshman) engineering students at the University
of Pittsburgh Swanson School of Engineering, the user does so at his or her own risk.
THE COMMERCIAL AND ENVIRONMENTAL VIABILITY OF PROTON
EXCHANGE MEMBRANE FUEL CELL-BASED ENGINES IN BUS TRANSIT
Justin Komp, [email protected], Mena Lora 3:00 PM, Sooraj Sharma, [email protected], Mahboobin 10:00 AM
Abstract--Modern climate concerns over the state of earth's
ozone layer and rising global temperatures are almost
universally attributed to man-made processes. The use of
commercial automobiles is viewed as a major contributor to
climate change due to the various types of pollutants
produced by the combustion engine. In an effort to develop a
more eco-friendly means of transportation, transportation
officials are pushing for the widespread adoption of bus
transportation. Developing alternate clean fuel sources to
further reduce vehicular environmental impact is stressed as
well. Of the many existing alternatives to diesel fuel, Proton
Exchange Membrane Fuel Cells (PEMFC’s) are viewed as a
strong contender.
A specific variant of the hydrogen fuel cell, which
generates electricity through hydrogen-based chemical
reactions, the PEMFC is equipped with platinum electrodes
and a polymer-based electrolyte that gives it a high tolerance
for heat and pressure. This translates to PEMFC’s being
considered above other hydrogen fuel cell variants for use in
buses, and adequate research exists to prove so through the
use of simulation.
Another issue concerns the commercial viability of fuel
cell buses in general and the difficulties faced by transit
agencies in implementing them into mass transit, as a result
of both standards established by conventional buses not yet
reached by fuel cell ones, and a lack of infrastructure
necessary to support fleets of these vehicles.
Key Words—bus, engine, FCEB, HT-PEMFC, PEM, transit.
PUBLIC TRANSIT: IT’S BETTER, BUT
NEEDS IMPROVEMENT
As the effects of global warming on the environment
became more and more apparent in the past half-century,
views towards adopting more eco-friendly practices to at least
stagger the damage caused by man-made processes were
absorbed into the zeitgeist of the 21st century. An emphasis on
such processes ubiquitous to one’s daily life began to
crystallize, with one of these being the polluted emissions of
conventional automobiles. The preferred means of
transportation in only a few developed
University of Pittsburgh, Swanson School of Engineering 1
Submission Date 03.31.2017
countries, like the United States, the automobile serves a role
that can be easily replaced by a more utilitarian, cheaper, and
most importantly, cleaner means of transport: transit buses.
But if the ultimate goal of this effort is to achieve
minimal to zero emission levels from civilian transportation
vehicles, simply replacing automobiles with buses is not
enough. Although the latter are fewer in number, they burn a
considerably more “dirty” fuel, the effects of which may be
just as worse as that of automobiles. In addition, great care
must be taken to ensure that existing technologies and the
steps taken to implement them are sustainable. Therefore, the
adoption of an alternate, clean source of power to replace the
engines in current transit buses, specifically PEMFC’s, is in
short order.
WHY NOT FUEL CELL CARS?
Automobiles: Pollution En Masse
Quite possibly the largest drawback to owning a
passenger vehicle is the stress placed on the environment
through their continued use. According to the U.S.
government’s Environmental Protection Agency webpage on
common sources of greenhouse gases, the common passenger
automobile emits roughly nine thousand grams of carbon
dioxide (CO2) per gallon of gasoline burned, in addition to
releasing other harmful gases such as methane, nitrous oxide,
and various chlorofluorocarbons (CFC’s). Statistically, the
average passenger vehicle has a fuel economy of 22 miles per
gallon and travels up to eleven thousand miles over the course
of a year. This means that the over two hundred and fifty-three
million cars and trucks in the United States each produce at
least 4.7 metric tons of CO2 per year, which accounts for 26%
of yearly greenhouse gas emissions [1].
Buses: Scarce, Nicer, yet Dirtier
One of the most attractive qualities of bus transportation
is the fact that it offers a source of mobility for non-drivers,
specifically minors, the elderly, and individuals either
physically, mentally, or financially unable to own a passenger
vehicle. This trait is further exemplified by the significantly
safer nature of bus transit, which tends to be rigorously
Justin Komp
Sooraj Sharma
scheduled, operates only in specific lanes of the road, and by
nature of its size, is less susceptible to damage in a vehicular
collision [2].
But it’s the fact that the nature of buses reduces pollutant
emissions that makes them a smarter alternative to
automobiles. This measured reduction in emissions can be
attributed to one defining characteristic of buses: there are less
of them on the road. Fewer vehicles reduce traffic congestion,
eliminating emissions from oft-stationary vehicles (especially
in urban environments), and this results in proportionally
smaller emission levels of CO2 and CFC’s in comparison to
automobiles [2].
However, size isn’t everything. In fact, when it comes to
buses, it’s their relative physical size that is as much of a
drawback as their reduced number on the roads with regards
to air pollution. Nearly all buses in the world are powered by
diesel fuel, which produces not only a larger amount of CO2
per gallon burned but contains a multitude of harmful
carcinogens and particulates that have been shown to cause
various adverse health effects in humans. According to the
Respiratory Health Association’s Chicago branch, data shows
that over 20,000 asthma attacks, 680 heart attacks, and over
570 premature deaths in the state of Illinois can be attributed
to diesel exhaust every year [3].
Although government regulation has required transit
buses produced after 2007 to be fitted with tailpipe filters that
limit particulate emissions, the effect is about as useful as
putting a filter on a cigarette: diminishing the potential harm
but not removing it entirely. This is where alternate sources
of fuel for buses, in this case, hydrogen fuel cells, comes in to
play [3].
A simple diagram of a hydrogen fuel cell. Note the
parallel it shares with the structure of a battery.
Initially, the hydrogen gas molecules are stored in the
anode, where a catalyst ionizes them to form positively
charged protons and negatively charged electrons,
H2(g)
→
2H+ + 2e- (6)
, whilst the cathode contains oxygen gas (O2) molecules.
Because of the nature of the chemical reaction that
occurs between hydrogen and oxygen to form water vapor,
the hydrogen protons are drawn through the electrolyte to the
other side of the cell. However, the chemical composition of
the electrolyte prevents the electrons from doing this as well.
Instead, they travel through a circuit external to the cell, thus
generating an electrical current, and end up on the cathode
side with the hydrogen ions and oxygen gas:
2H+(g) + 2e- + 1/2O2(g) (6)
At the cathode, hydrogen gas reacts with oxygen gas to
form water vapor and excess gases, which are expelled from
the cell:
2H+(g) + 2e- + 1/2O2(g) → H2O(g) + excess H2(g) (7)
The overall chemical reaction has a real-world parallel,
electrolysis,
H2O(g)
+
→ 2H (g)
+ 1/2O2(g) (7)
, in which an electric current is run through a sample of liquid
water or water vapor to separate it into its constituent gases.
In essence, the reaction that occurs in a fuel cell can be called
“reverse electrolysis”. The implication for such a reaction
means that the cell can be reset to its initial state by charging
it after exhausting its fuel source. The conclusion that can be
drawn from this points to fuel cells as being a truly
“renewable” power source [8].
There are many types of fuel cells, the names and
properties of which are dependent on the type of electrolyte
they use. These various electrolytes affect properties such as
the maximum operating temperature, the cost of production,
the amount of current generated, and the efficiency of each
cell. Existing variants include the Proton Exchange
Membrane, Direct Methanol, Phosphoric Acid, Alkaline,
Molten Carbonate, and Solid Oxide fuel cells. The Proton
Exchange Membrane (PEM) fuel cell utilizes platinum coated
electrodes and an electrolytic membrane that is constructed of
water-basic acidic polymers [9].
The defining characteristic of a PEM is its electrolyte,
which is a specific type of polymer called an ionomer. The
chemical structure of an ionomer, unlike a polymer, contains
charged ends that can easily facilitate the transfer of ions and
other charged particles. As the commercial need for ionomers
FUEL CELLS AND THEIR VARIANTS
A good analogy for understanding what a fuel cell is and
how it works is to use a voltaic cell (a basic battery), for
reference. Both are constructed out of an anode, or the
negatively charged plate, a cathode, or the positively charged
plate, and the electrolyte, the medium between the two ends
that conducts the chemical reaction that generates electricity.
In addition, a fuel cell contains two or more fuel sources,
which are almost always hydrogen and oxygen gas, and a
circuit through which free electrons can flow [4].
FIGURE 1 [5]
2
Justin Komp
Sooraj Sharma
is low due to their limited scope of use, only a few existing
variants are viable in the proton membrane market. Chief
amongst these is Nafion, developed in the 1960s by Walther
Grot of American chemical conglomerate DuPont.
Characterized as “the first ionomer”, this Teflon-based
ionomer’s chemical properties allow it to be an excellent
proton conductor and terrible electron conductor. That is, it
perfectly fits the definition of an effective PEM electrolyte
[10].
In an investigative study into the properties of proton
exchange membranes used in PEM fuel cells conducted by
researchers M.A. Hickner and B.S. Pivovar, the two
characterized the relative usefulness of PEM’s by their
conductivity, permeability, mechanical properties, and
chemical stability. A set of trials that measured these
properties were conducted between Nafion and several other
ionomer compounds, such as poly-arylene-ether sulfone
(BPSH) and poly-arylene-ether sulfone (PATS), which
resulted in Nafion coming out on top, and the researchers
ultimately attributing this to the relatively simple chemical
composition of it in comparison to its competitors. In
addition, BPSH and PATS displayed an inability to maintain
optimal performance capacity and were shown to have
considerably less permeability for the transport of hydrogen
ions [11].
It’s these properties of Nafion that gift PEM fuel cells
with the ability to operate under high temperatures with little
resistance to heat change, as well as have low “cold” startup
times and an impurity tolerance that, at best, can resist
decently high amounts of impurities like Carbon Monoxide.
Essentially, these are “ideal cells” for replacing diesel engines
in buses [11].
FIGURE 3 [12]
The structure of a cell stack. Larger MEA’s are
more common.
In considering a PEM-based engine for a transit bus, five
major elements of its design must be considered: power
conservation, fuel volume, temperature regulation, startup
times, and pollutant tolerance. Should a hypothetical testing
bed with the PEM cell stack succeed in all of the categories,
“promising” quickly becomes “viable”.
Modeling the Engine: Fuel and Power
Quite possibly the most important of these elements is
the amount of fuel needed and thus power conservation for
the PEM engine, as this places a constraint on the amount of
time the bus can operate before it must be refueled or retired
for the day. A scholarly article presented by three researchers
from the University of Perugia sought to develop a dynamic
low-temperature PEM (LT-PEMFC) engine model suitable
for a bus with a capacity to operate for twelve hours per day.
Keeping in mind the fact that the current generated by a PEM
cell engine would not be nearly enough to power a 12+ footlong, 18 ton diesel bus, a separate battery system was
proposed to the cell stack, resulting in a hypothetical hybrid
engine [13].
Developed in a Matlab/Simulink development
environment, a dynamic model of a fuel cell stack wired in
parallel with a battery source was created. The cell system’s
chief properties were its number of constituent cells (88), the
initial voltage while not under load (.6V) and its hydrogenoxygen flow ratio (1.168). As for the battery, its SOC, or state
of charge, was measured. Holding these parameters constant,
a diagram of a basic transmission system was created, which
involved connecting the battery source and the cell stack to a
DC power converter, which in turn was connected to a motor
controller, a motor, and finally a gearbox attached to the front
axle of the virtual bus [13].
PEMFC’s: DEVELOPING AN IDEAL BUS
ENGINE
Although PEMFC’s are viewed as the most promising
fuel cell variant for vehicular applications, a single cell only
makes up a fraction of the cell stacks used in powering the
vehicle it’s placed in. A cell stack is comprised of alternating
fuel cells sandwiched between bipolar plates in an
arrangement known as a membrane electrode assembly
(MEA). The MEA is capped off by two end plates that feed
into the MEA hydrogen and oxygen gas for the desired
reactions to occur [12].
3
Justin Komp
Sooraj Sharma
light and service vehicles showed that this particular type of
cell, if adequately cooled, could maintain a suitable power
output while having a significantly higher resistance to carbon
monoxide poisoning. In the study, five researchers
synthesized a large body of research that centered on HTPEMFC fuel sources, engine start-up times, possible
applications of HT-PEMFC’s, cooling cell arrangements, and
carbon monoxide tolerance levels in order to determine the
optimal procedures to satisfy these criteria [14].
With regards to obtaining fuel, the biggest hurdle facing
the research group were the logistics required to obtain the
large amounts of hydrogen fuel needed to power the cell
stack. Since no large-scale industries exist that distribute pure
hydrogen gas (which rarely occurs naturally in its gaseous
state), the fuel would have to be obtained from existing
components. One proposed method involved using liquid
hydrocarbon fuel to extract hydrogen. This method was
especially popular amongst the research group as it drew
parallels to methods used in obtaining diesel fuel [14].
Yet another detail brought up in the paper was the matter
of power consumption of a heavy vehicle during stationary
periods, or “idling”. The diesel engines of heavy trucks and
buses are estimated to idle for 20-40% of their lifespan, which
led to the researchers to reconsider implementing an HT-PEM
engine as an auxiliary power unit (APU) as a backup to the
main power source of the vehicle to counteract the normally
high emission levels produced during diesel engine idling.
Such an APU would have to generate at least 1.4 kilowatts of
energy to keep up with the demands of a similar vehicle, like
a transit bus [14].
One of the most important, yet neglected factors in
designing the fuel cell engine was the projected startup time
after charging the cells. As this was estimated to take at least
five to ten minutes, it was necessary to consider a joint power
system to maintain some level of vehicle functionality until
startup. Thus, a buffer battery system was proposed to power
the vehicle until at least 85% fuel cell efficiency would be
reached [14].
An HT-PEMFC obtains its name from the relatively
high temperatures it operates at: 120 to 180 degrees Celsius,
more than 100 degrees Celsius above the standard LTPEMFC’s normal operating temperature range. However,
temperatures exceeding this upper limit can cause damage to
cell components, so a system consisting of cooling cell
arrangements was considered. After comparing the pros and
cons of four different case studies of cooling cell
arrangements in an HT-PEMFC stack, two preferred
arrangements came out on top: one with a 3:1 cell to cooling
plate ratio and one with a 4:1 cell to cooling plate ratio.
Between the two, it was shown that the latter model produced
up to 80% more wattage while under load, at the cost of a
higher than normal temperature variation (40K in comparison
to the preferred 20K) [14].
The excellent catalyzing properties of the platinum
catalyst in a PEMFC is offset by a rather small tolerance for
carbon monoxide, which, in LT-PEMFC’s can cause
FIGURE 4 [13]
The transmission mechanism for the stack/battery pack
hybrid engine
In this type of transmission, it was noted that while
stationary, the nature of the connection of the battery and fuel
cell stack to the DC converter would allow for the battery to
recharge over while not under load, i.e., while parked or in
traffic. Also of importance was the fact that the nature of a
transit bus meant that load size would be dynamic: throughout
a day of operation, the amount of passengers at a single time
is generally never constant and thus the significance of the DC
converter would be to switch between the battery or the cell
stack for its power source [13].
Mathematically, the total current generated by the
transmission can be described by,
Ireq = Icell + Ibat (13)
, where Icell and Ibat are the output current of the cell stack and
battery source, respectively, and Ireq being the required
electrical load for the bus. The purpose of this equation was
to predict hydrogen consumption and SOC, which would give
an estimate of the desired cell stack size and battery charge
control strategy [13].
When it came time to simulate the modeled engine under
load during a 12 hour duration, the researchers ran
approximately four trials of 25 cycles each in the Matlab
environment. In each trial, the power output of the cell stack
was varied, with the end goal of having the SOC of the battery
not fall below .8 from an initial value of .9. After the
simulation’s end, it was shown that the only case that satisfied
the above criteria was one which used two 16.5 kW fuel cell
stacks, and this resulted in a final SOC of 0.812. In addition,
the determined amount of hydrogen fuel was revealed to be
18.53 kilograms, which concluded the experiment [13].
Modeling the Engine: Startup Times, Temperature, and
Impurity Control
A PEM cell under load tends to generate a large amount
of heat that if not regulated, can damage the cell stack. More
importantly, the platinum catalysts used in a conventional LTPEMFC cell’s anode are rather susceptible to pollutants,
especially carbon monoxide (CO). A study of the viability of
high-temperature PEMFC’s (HT-PEMFC) for use in heavy,
4
Justin Komp
Sooraj Sharma
significant performance drops if amounts as small as 100 parts
per million of the compound are present. HT-PEMFC’s on the
other hand, due to the higher temperature they operate at, have
a significantly higher resistance to impurities. This property
of HT-PEMFC’s made the option of using hydrogen mixed in
with liquid hydrocarbons containing carbon monoxide as a
fuel for the cell stack much more viable of an option [14].
In the paper, data from nine experimental methods
dealing with carbon monoxide tolerance at
varying
temperatures were compared, and a relationship between
output current density (cell performance), operating
temperature, and impurity (carbon monoxide) levels in the
proposed liquid hydrocarbon fuel was discovered: at lower
temperatures, higher levels of CO resulted in a lower current
density [14].
With the theoretical viability of LT- and HT-PEMFC’s
in buses having been tested through simulation and basic
models, the results are rather satisfactory. However, the fact
remains that in all of the discussed studies, no one-to-one
PEMFC engines were developed, and no testing was done
with existing fuel cell buses. A simulation is a synthetic
benchmark and does not hold as much water as a real-world
one. Furthermore, while great expense was taken to analyze
the technical details of the engine variants, little stress was
placed on factors like commercial viability, real-world
testing, and the logistics of managing a fleet of such buses,
additional factors that bridge the gap between the worlds of
engineering and commercial transportation.
buses. This complete process is demonstrated in steps 6-8 of
the following figure [15].
FIGURE 5 [15]
A diagram showing the commercialization process for
new technologies.
Diesel-powered buses fall at number 9 on this spectrum,
with most fuel cell electric buses (FCEB’s) falling in the 4-5
range. To see how these vehicles held up against their diesel
variants, the report included the same data categories for
conventional “baseline” buses from Gillig’s diesel and
compressed natural gas fleets [15].
When it came to the desired lifetime of the PEM engine
in a roadworthy FCEB, the FTA determined the minimum life
cycle to be set at 12 years, or roughly 500,000 miles traveled.
Since diesel engines tend to be replaced at around the halfway
point in this timespan, the FTA set an ultimate lifespan target
for around 4 to 6 years, with an interim one of 18,000 hours
(2.1 years). According to the figure below, the eighteen
FCEB’s from AC Transit, SunLine, and UCI averaged 12,032
cumulative road hours without any major engine failures, with
67% of them surpassing that average and two breaching the
FTA 2016 interim target [15].
FUEL CELL BUSES: HOW DO THEY
STACK UP ON THE ROAD?
Case Studies of Fuel Cell Buses: NREL’s Assessment
Designing a transit bus engine powered primarily by
fuel cells is one thing; determining whether or not such an
endeavor will be viable in the real world is as dependent on
existing technology as it is on the infrastructure needed to
support large scale fuel cell bus operations.
In July 2016, three researchers in the U.S. Department
of Energy’s National Renewable Energy Laboratory released
their yearly report on the current status of all operational fuel
cell bus fleets in the United States. The purpose of this report
was to assess the progress of three bus operators (AC Transit,
SunLine Transit Agency, and University of California at
Irvine (UCI)) made regarding transitioning their vehicles into
mass transit, from August 2015 to July 2016. This was
assessed by obtaining and placing relevant data into separate
categories, the most important of which included bus lifetime
in terms of years/miles, fueling times, and road call
frequency, among other criteria. Each category had a yearly
interim target and an ultimate target set by the Federal Transit
Authority (FTA), with the latter target serving to determine a
technology readiness level (TRL) comparable to conventional
FIGURE 6 [15]
A visual of engine lifespan per FCEB.
Transit services reserve a 6 to 8 hour window of each
day to service and refuel their buses. This means that a ten
minute window is required for refueling each bus. As FCEB’s
rely on pressurized hydrogen gas for fuel, the fueling rate is
directly affected by the pressure of the fueling pump. As the
dangers of a hydrogen leak are more concerning than a liquid
fuel-based one, larger funds are required to build safer and
more efficient fueling pumps. Thus, AC transit, with the
5
Justin Komp
Sooraj Sharma
largest FCEB fleet of the three operators, has pumps with a
fill rate of 5 kg per minute, which totals up to a sub-ten minute
refueling period. On the other hand, SunLine’s pumps require
around 22 minutes and UCI’s are slightly higher at 24 minutes
[15].
A large part of ensuring the quality of public transport is
achieving consistency. That is, reducing the ratio of
equipment failure occurrences to the distance traveled in
order to ensure a smooth travelling experience. Mean distance
between roadcalls (MBRC) measures this by observing the
miles traveled until the bus must be stopped due to equipment
failure or general maintenance. A larger MBRC shows a
smaller propensity for failure and thus a more reliable system
overall. The below figure shows recorded MBRC values over
the almost one year timespan in relation to interim and
ultimate targets set by the FTA [15].
A HYPOTEHTICAL TRANSITION
Making the Jump to FCEB’s: Analyzing Tennessee’s
Knoxville Area Transit System
In a case study of the logistics of Knoxville Area Transit
(KAT), researchers analyzed the service’s fleet size,
production and storage facilities, and personnel to develop a
roadmap for hypothetically transitioning KAT to a FCEBdominated transit service over a given amount of time.
The first step in determining whether such a transition
would be viable would be to calculate the projected FCEB
fleet size as the current development state of hydrogen cell
technology might require an increase to compensate for
relative inefficiency. This new figure can be calculated using
the following equation,
N = C(1 + Z/A)(1+X) (16)
, where C represents the current fleet size, Z is the availability
goal of the transit fleet, A is the average availability for the
specific fuel cell technology sought after, X is the planned
percent increase in fleet size, and N is the amount of extra
FCEB’s required. Z was shown to hover around 60% (.6), and
to obtain a value of A of at least 85%, C(1+Z/A) can be
simplified to 1.42C. As KAT was observed to be in economic
stasis due to financial matters, it was estimated that the fleet
would have to expand from its current fleet of 93 diesel buses
to a total of 132 FCEB’s [16].
The next step in this assessment was to determine an
effective fueling infrastructure. The proposed process for
obtaining hydrogen fuel revolved around obtaining natural
gas in the form of liquid hydrocarbons, and using electrolysis
to retrieve the gas from the liquid. Assuming that no special
deals between energy providers had been brokered, the cost
per mile compared to diesel fuel would be at least $0.75
higher. This increase in expenditures was viewed as small
price to pay for effectively eliminating KAT’s dependence on
the total of 850,000 gallons of diesel fuel consumed per year,
as the environmental advantages were deemed to compensate
[16].
To complete the hypothetical transition, it would be
necessary to overhaul current maintenance and refueling
facilities, as well as the skillsets of active personnel. KAT
refueling buildings contained a single service bay with fuel
pumps, revenue collection equipment, and bus washing
machines. As for maintenance sites, existing locations contain
a maximum of 12 service bays, with staff that operates
specialized equipment. Due to the scale of upgrades and
overhauls needed to house a FCEB fleet, the researchers
decided the best course of option would be to build separate
facilities for it [16].
KAT’s 171 service personnel consisted of 141 bus,
trolley, and van operators, as well as 30 bus operators from
the University of Tennessee. The maintenance department
contained 45 employees, with 21 of them serving as
FIGURE 7 [15]
A visual comparing MBRC values over the time period.
This displays a general upward trend for both FCEB
reliability and fuel cell powered systems in general, with both
ultimate and interim targets being surpassed by the end of July
16th. An analysis of cumulative MBRC since August of 2012
shows a 94.4% increase, a considerable improvement over
such a short span of time [15].
Although the performance figures of fuel cell buses
were shown to be promising, with the general trend towards
reaching the goals set by the FTA displaying an upwards
slope towards the late stages of the TRL spectrum, the fact
remained that the commercialization of fuel cell buses was
held back by a lack of support infrastructure. That is, there is
no widespread, large-scale hydrogen fueling system across
the United States and other countries with active fleets, and
there are a rather small amount of maintenance facilities and
workers with the knowledge to repair and service fuel cell
buses. Since researchers were able to accurately quantify the
viability of an experimental PEM engine without having to
build one with raw materials, would it not make sense to judge
the difficulty of creating such an infrastructure, without
having to go through the pains of creating one in the real
world?
6
Justin Komp
Sooraj Sharma
mechanics. Each operator would require a basic level of
understanding of troubleshooting with fuel cell systems,
whilst the mechanics would have to undergo more rigorous
training to understand the mechanisms of the new engines
they were to work with [16].
Thus, the transition strategy was as follows: first
calculate the projected new fleet size based on availability
constants, then develop a hydrogen gas fueling infrastructure,
and finally determine overhauls and upgrades needed for
maintenance facilities and personnel. However, estimated
costs to carry out these procedures were determined to
overwhelm KAT’s spending power as time progressed, so a
plan to instead slowly phase in the FCEB fleet was proposed,
instead of original one of removing the old one instantly. One
of the more intelligent strategies to propagate this plan
focused around introducing a small amount of FCEB’s into
KAT’s most used bus routes, and building a small amount of
refueling and maintenance facilities by major roadways. By
spending the minimum amount of capital, public awareness
of these new buses would rapidly increase, which would lead
to a more widespread acceptance of fuel cell technology,
willingness to try these means of transport, and therefore
would influence other transit magnates to consider
implementing FCEB’s into their fleets [16].
The plan to transition Knoxville’s transit system to one
used completely by fuel cell buses was undeniably an
ambitious one, as it tried to put both an established and
effective means of transport and a newly developing, but
promising one, on the same ground. The fact holds that
widespread acceptance of hydrogen cell buses is a journey
that contains many seemingly insurmountable obstacles, and
this is only magnified by the fact that the case study is one of
the only of its kind to tackle this problem on such a large scale.
Such an analysis bridges on the topic of whether or not fuel
cell technology is sustainable, and what implications it holds
for future generations: the population that will utilize it to its
fullest extent.
on to this by placing the constraint that such a process must
be designed to satisfy present needs yet not hamper those of
future generations [17]. As fuel cell technology is rather
infantile in its development, researchers and engineers have
encountered two major conflicts in developing a PEM engine:
whether the cost of manufacturing components is worth the
money saved by the projected reduction in pollution, and if
the importation of rare earth minerals in PEM cells,
specifically Platinum, could pose potential financial and
human rights violations in the relatively underdeveloped
nations that contain the majority of the world’s platinum ore
reserves.
The First Dilemma: Bus Expenses
The NREL’s report stated that AC Transit’s FCEB’s
costed over 2.5 million dollars to build in 2010, although
recent orders by SunLine produced figures in the 1.8-2million-dollar range. The FTA set a 2016 goal for the mean
FCEB production cost at one million dollars per bus—a hefty
sum—with an ultimate future goal of 600,000 dollars per bus.
Assuming that the average public transit diesel bus costs half
the FTA’s ultimate target, and if FCEB’s are projected to
eventually phase out these buses, the cost of this transition
would undoubtedly be extremely expensive [15].
FIGURE 8 [15]
A table of NREL statistics with an emphasis on cost and
fuel economy.
To rationalize these expenses, the fuel economy of
FCEB’s and the current costs in maintaining procedures that
actively reduce the effects of greenhouse gases on the
environment must be analyzed and compared. The NREL
report calculated AC Transit, SunLine Transit, and UCI’s
buses to have an average fuel economy of 5.43 miles per
kilogram of hydrogen fuel consumed, compared to the 6-8
mile per gallon fuel economy of the average diesel bus. With
a mean fuel capacity of 47 kilograms of hydrogen, this means
that modern FCEB’s can travel at least 230 miles on a single
refill. This trait is further exemplified by the fact that diesel
fuel isn’t free—it must be obtained at stations for roughly 23 dollars per gallon—whilst hydrogen, as stated earlier, can
be obtained not only from pumping stations, but also from the
atmosphere and electrolysis [15].
With regards to the cost of pollution caused by road
transportation, the Organization for Economic Co-operation
and Development (OCED) estimated that from 2005 to 2010,
roughly 3.5 million people around the world died per year due
to health complications caused by road vehicle pollution
(mostly in developing countries), overtaking figures caused
SUSTAINABLE DEVELOPMENT:
MINIMIZING THE AFTERSHOCKS OF AN
EARTHQUAKE
In designing solutions to problems in engineering, it
becomes very easy for one to be caught up in a fury of
idealism, the belief that their innovation can only benefit its
users in the long run. This is simply not the case. As Newton
proved in his Philisophiæ Naturalis Principia Mathematica
almost four hundred years ago, for every action, there is an
equal and opposite reaction. That is, benign innovations can
elicit unwanted malignancies. Thus, engineers must consider
the topic of sustainability, or rather, sustainable development,
in their design processes.
Sustainability is broadly defined as processes’ ability to
continue itself indefinitely, specifically in the environmental,
economic, and social sectors. Sustainable development adds
7
Justin Komp
Sooraj Sharma
by poor sanitation and scare clean drinking water. At the end
of that time period, the cost of the health impact of air
pollution in China and India totaled over 1.4 trillion and 0.5
trillion dollars, respectively. In response to this epidemic, the
OCED petitioned its 34 member countries to collectively
assess how much they would be willing to pay towards efforts
to reduce pollution caused by transportation; a final figure of
1.7 trillion USD was reached [18].
If one could place a price on a human life (as is often
done in the economic sector), it’s conclusive that fuel cell
buses, which seek to offer accessible and clean transportation
incur a cost that pales in comparison to money lost on damage
control due to air pollution. In turn, this may result in many
lives being saved. The implication is that FCEB’s can be
sustained for a long amount of time without causing any harm
to future generations, which fits the definition of a sustainable
process.
But is it really true that no external harm is caused in the
production of PEM engines, and the research that surrounds
them? In most manufacturing processes, at least one step
(usually at the lowest tiers of production), relies upon the use
of cheap human labor, usually in developing countries where
human rights violations are ignored. This encroaches upon the
topic of social sustainability, and whether progress made at
the expense of others’ suffering is progress at all.
these costs? The answer, ultimately, is dependent on its future
consequences, which are shrouded by the fog of time.
COMING FULL CIRCLE…IN A BUS
Replacing automobiles with transit buses for mass
transport rakes in more benefits than losses, chief amongst
these being their price of use, safety features, and most
importantly, lower emission levels across the board.
However, these levels can be brought to zero by replacing
diesel transit buses with fuel cell buses that run on hydrogen
and oxygen gas, producing only harmless water vapor and
trace amounts of excess hydrogen gas as a byproduct.
Amongst the many types of fuel cells, proton exchange
membrane fuel cells are the first choice regarding vehicular
transport, as multiple studies and data simulations have
displayed their effectiveness in a hypothetical fuel cell bus
engine.
Approaching the topic of sustainability, PEM
technology and fuel cell buses, for the most part, seem to fit
the definition of sustainable processes, as they’re projected to
produce net benefits across the environmental and economic
sectors whilst incurring a somewhat noticeable penalty in the
social sector.
The fuel cell bus industry, at the current time, is only
starting to take its first steps in the world of public transit.
Although the desired goals set by the FTA concerning the
ability of FCEB’s to function properly on the road are far from
being met, what’s clear is that substantial progress has been
made over the years towards those endpoints. Similarly, the
process of phasing out diesel buses entirely is difficult, as was
the case in Knoxville, but not impossible, to achieve.
The Second Dilemma: Foreign Importations and Human
Rights Violations
The efficiency of the electrolysis in a PEM cell is
directly correlated to the platinum catalysts they use, which
speed up the rate of chemical reaction, and thereby the amount
of current produced in a given amount of time. However, the
United States and other developed nations contain only a
fraction of the world’s total platinum reserves, and thus must
import them from ore-rich countries. With over 80% of the
world’s natural platinum reserves, South Africa is the largest
exporter of the incredibly expensive metal, which is
monopolized by Anglo Platinum. In the past decade, the
mining company has received unwanted attention due to a
series of strikes led by labor unions in the Mapela community
in the city of Limpopo, brought upon by air pollution, a lack
of clean drinking water to workers and their families, adverse
effects on agriculture due to land marginalization, and an
overall shortage of food in families of mine workers [19].
Of the two conflicts, the latter is undoubtedly of more
import. It is viewed as unethical to profit at others’
misfortune, especially when such events occur from halfway
around the world, making it easy for one to turn a blind eye
or deaf ear to such suffering. If, however, we consider these
evils in the grand scheme of pollution reduction, are they
really so terrible as to abandon fuel cell technology entirely?
In utilitarian terms, which considers the net good produced at
the end of the day, they aren’t. In deontological terms, which
only cares about what is inherently right and wrong, they are.
Regardless, is PEM technology truly sustainable if it comes at
SOURCES
[1] “Greenhouse Gas Emissions from a Typical
Passenger Vehicle” United States Environmental
Protection
Agency.
Accessed
3.1.2017.
https://www.epa.gov/greenvehicles/greenhouse-gasemissions-typical-passenger-vehicle-0
[2] “Evaluating Public Transit Benefits and Costs” Victoria
Transport Policy Institute. 2.1.2017. Accessed 2.28.2017.
http://www.vtpi.org/tranben.pdf
[3] “Transit Buses” Respiratory Health Association. Accessed
2.27.2017.
http://www.lungchicago.org/diesel-pollutiontransit-buses/
[4] “How Fuel Cells Work.” Fueleconomy.gov. Accessed
2.28.2017.
https://www.fueleconomy.gov/feg/fcv_PEM.shtml
[5] “What is a Fuel Cell” Juliantrubin.com. 2013. Accessed
2.20.2017.
http://www.juliantrubin.com/bigten/fuel_cell_experiments.ht
ml
8
Justin Komp
Sooraj Sharma
[6] “What is a Hydrogen Fuel Cell?” Science Education for
Public Understanding Program. 11.2.2016. Accessed
3.2.2017. http://sepuplhs.org/high/hydrogen/hydrogen.html
[7] “Electrolysis”. Chemistry Libretexts. Accessed 3.1.2017.
https://chem.libretexts.org/Core/Analytical_Chemistry/Elect
rochemistry/Electrolytic_Cells/Electrolysis
[8] “Fuel Cells”. Hydrogenics Webpage. 2017. Accessed
3.1.2017.
http://www.hydrogenics.com/technologyresources/hydrogen-technology/fuel-cells/
[9] “PEMFC.” FuelCellToday. Accessed 1.8.2017.
http://www.fuelcelltoday.com/technologies/pemfc
[10] “All About Nafion”. Perma Pure LLC. Accessed
3.2.2017. http://www.permapure.com/resources/all-aboutnafion-and-faq/
[11] M. A. Hickner, B.S. Pivovar. “The Chemical and
Structural Nature of Proton Exchange Membrane Fuel Cell
Properties.” Fuel Cells. 11-2004. Accessed 3.1.2017. p.227.
http://onlinelibrary.wiley.com/doi/10.1002/fuce.200400064/
pdf
[12] “Fuel Cell Stacks”. Fuel Cell Store. 2017. Accessed
3.2.2017. http://www.fuelcellstore.com/fuel-cell-stacks
[13] B. Linda, B. Gianni, O. Andrea. "Optimization of a
PEMFC/battery pack power system for a bus application."
Applied Energy. 9-2012. Accessed 2.26.2016. p.777-784.
http://www.sciencedirect.com/science/article/pii/S03062619
11007409
[14] L. Wongfeng, L. Werner, J. Holger, R Sansum, S. Detlef.
"A review of high-temperature polymer electrode membrane
fuel-cell (HT-PEMFC)-based auxiliary power units for
diesel-powered road vehicles." Journal of Power Sources. 42016.
Accessed
3.1.2017.
p.91-102.
http://www.sciencedirect.com/science/article/pii/S03787753
16301410
[15] "Fuel Cell Buses in U.S. Transit Fleets: Current Status
2016." National Renewable Energy Laboratory. 11.2016.
Accessed
1.25.2017.
p.1-46.
http://www.nrel.gov/docs/fy17osti/67097.pdf
[16] L. Brian, Cherry. Christopher. “Transitioning a bus
transit fleet to hydrogen fuel: A case study of Knoxville Area
Transit.” International Journal of Hydrogen Energy. 2-2012.
Accessed
1.8.2017.
p.2636-2642.
http://www.sciencedirect.com/science/article/pii/S03603199
11024487.
[17] “Sustainability”. Thwink.org. Accessed 3.28.2017.
http://www.thwink.org/sustain/glossary/Sustainability.htm
[18] “The Cost of Air Pollution”. Organization for Economic
Co-operation and Development. 5.21.2014. Accessed
3.30.2017.
http://www.oecd.org/env/the-cost-of-airpollution-9789264210448-en.htm
[19] “ActionAid South Africa launches report highlighting
human rights violations at Anglo Platinum mine.” Creamer
Media’s Engineering News website. 6.23.2016. Accessed
3.29.2017.
http://www.engineeringnews.co.za/article/actionaid-southafrica-launches-report-highlighting-human-rights-violationsat-anglo-platinum-mine-2016-06-23/rep_id:4136
ACKNOWLEDGEMENTS
Justin and Sooraj would like to thank our writing
instructor, Amanda Ambrant, for her insightful comments and
advice on how to shape this paper, Emily Irwin for her inperson critique of our drafts, and conference Co-Chair Nick
for his hard analysis of how our paper should be laid out
before the conference next week.
9