challenges
Article
Case Studies of Energy Storage with Fuel Cells and
Batteries for Stationary and Mobile Applications
Nadia Belmonte 1 , Carlo Luetto 2 , Stefano Staulo 3 , Paola Rizzi 1, * and Marcello Baricco 1
1
2
3
*
Department of Chemistry, Centre for Nanostructured Interfaces and Surfaces (NIS), University of Turin,
10125 Torino, Italy; [email protected] (N.B.); [email protected] (M.B.)
Tecnodelta Srl., 10034 Chivasso, Italy; [email protected]
Stones Sas., 10093 Collegno, Italy; [email protected]
Correspondence: [email protected]; Tel.: +39-011-670-7565
Academic Editors: Annalisa Paolone and Lorenzo Ulivi
Received: 31 January 2017; Accepted: 20 March 2017; Published: 22 March 2017
Abstract: In this paper, hydrogen coupled with fuel cells and lithium-ion batteries are considered as
alternative energy storage methods. Their application on a stationary system (i.e., energy storage
for a family house) and a mobile system (i.e., an unmanned aerial vehicle) will be investigated.
The stationary systems, designed for off-grid applications, were sized for photovoltaic energy
production in the area of Turin, Italy, to provide daily energy of 10.25 kWh. The mobile systems, to be
used for high crane inspection, were sized to have a flying range of 120 min, one being equipped
with a Li-ion battery and the other with a proton-exchange membrane fuel cell. The systems were
compared from an economical point of view and a life cycle assessment was performed to identify
the main contributors to the environmental impact. From a commercial point of view, the fuel cell
and the electrolyzer, being niche products, result in being more expensive with respect to the Li-ion
batteries. On the other hand, the life cycle assessment (LCA) results show the lower burdens of
both technologies.
Keywords: fuel cell; battery; life cycle assessment; integrated power system; unmanned aerial
vehicle (UAV)
1. Introduction
Energy is one of the keys to the development of nations and society. Civilization is dependent on a
constant, consistent supply of energy; globally, the demand for energy has been increasing consistently
in parallel with growth in population and economic consumption [1]. Stringent energy-related
problems have led to an increased interest in renewable energy sources. Due to the intermittent nature
of those sources, the energy production varies significantly according, for example, to the hour of the
day and the period of the year. Therefore, it is necessary to store the produced energy allowing its use
after production. The criteria for the selection of solutions for the storage of renewable energy are still
under debate, both for stationary and mobile applications [2].
Hydrogen is considered as an energy carrier and its chemical energy can be converted into
electricity through a chemical reaction by a fuel cell. Therefore, coupling energy storage systems
with renewable energy sources through an electrolyzer, which can transform electric energy into
hydrogen chemical energy, is considered as a highly sustainable process of exploitation of energy [3–5].
A good storage system should also be useful if the system is located in a remote off-grid area [6–8],
like mountainous regions [9] or small islands [10], as an alternative to the less-efficient and less
environmentally-friendly diesel generators that are normally used in these contexts [11–13]. For the
same type of applications, Li-ion batteries are also used coupled with renewable energy sources.
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The tradeoff between batteries and fuel cells is an issue not only for stationary applications,
but also for mobile ones, as shown in the literature about PEMFCs (proton exchange membrane
fuel cells) and electric vehicles [14,15]. The choice of one of these technologies for a specific application
can be made taking into account different factors, such as the hydrogen source, the electricity mix or
the price of the fuel, or specific application-related issues, like the weight of the system. This is the
case of small and mini unmanned aerial vehicles (UAVs), also known as drones. Due to an increased
interest in these devices [16–19], a large number of efforts have been dedicated to the estimation and
optimization of the flying range [20,21].
Since the currently commercialized drones are battery fed, increasing the size of the battery
could represent the easiest solution. According to some authors, however, this is not a viable
solution, as the weight of the battery becomes a limiting factor [22]. Studies on other portable power
applications [23,24] concluded similarly that, for shorter operational times, the battery system is best,
while for longer operational times the fuel cell is preferred from a weight perspective. Another explored
option is the use of a fuel cell: in this case, in fact, the only limit to the flying range is given by the
amount of fuel onboard. Hydrogen and methanol both represent valid alternatives as fuels for the
PEM fuel cell. In both cases, the power supply system of the device becomes more complicated with
respect to the use of batteries, requiring a fuel tank (for liquid methanol, or compressed hydrogen gas),
auxiliary components, and in the case of the use of methanol, a reformer unit. In particular, the presence
of a reformer unit determines the addition of extra weight and auxiliary components not necessary in
the case of a hydrogen-powered system.
Since it is not possible to find a general solution for the energy storage, specific case studies,
such as those aforementioned, have to be considered. However, when comparing batteries and fuel
cells for different stationary and mobile applications, some general benefits and drawbacks can be
outlined. For this reason, two alternative energy storage systems will be investigated in this work, i.e.,
Li-ion batteries and hydrogen coupled with PEM fuel cell-based technologies. The two technologies
will be considered for both a stationary and a mobile application. In particular, the stationary system
is a family house designed to have two days of self-sufficiency, while the mobile application is a
coaxial octocopter having a flying time of 120 min. A cost analysis will be shown, evidencing the main
contributions to the final cost of the considered devices. In addition, both systems will be investigated
focusing on the energy and materials used for their production, through a life cycle assessment tool.
Both energy storage technologies showed low environmental burdens if compared to other
components of the same system. Batteries have lower costs than fuel cells, and require less auxiliary
components. On the other hand, fuel cell-based systems showed a better adaptability to long operating
times. Starting from results on specific applications, it will be possible to obtain a wider overview of
the advantages and issues of the use of both technologies.
2. Systems Description
2.1. Stationary Application: Family House Energy Storage
A family house with 3–4 inhabitants, located in the area of Turin, Italy, was considered. This area
was chosen since it offers a great multiplicity of different scenarios, going from the grid-connected
urban area, to small, but still grid-connected villages, up to the remote mountain lodges, located in the
alpine chain, which cannot rely on grid connection. In all of these scenarios the application of a system
coupling renewable energy production and storage would lead to an improvement. In the case of
mountain lodges, this scenario will benefit from energy efficiency and self-sufficiency while, in urban
areas, the renewable energy system will help in meeting peak electrical load demands, thus reducing
risks of blackout phenomena.
Photovoltaics are the most widely applicable solution for renewable energy production in
this area. For an estimation of the energy production, the irradiation data for Turin in winter,
summer, and spring/autumn have been considered. The average daily irradiation has been obtained,
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as explained in detail in [25], and power curves were calculated. To estimate the electricity consumption
by
estimated
considering
commercial
electrical
appliances.
In
by the
the family
familyhouse,
house,load
loadcurves
curveswere
were
estimated
considering
commercial
electrical
appliances.
Figure
1, the
estimated
power
consumption
and
In Figure
1, the
estimated
power
consumption
andproduction
productioncurves
curvesfor
forthe
the winter
winter months
months are
are
reported
colored
areas
represent
thethe
system
working.
In the
area,area,
the
reported as
asaafunction
functionofoftime.
time.The
The
colored
areas
represent
system
working.
In green
the green
electricity
production
exceeds
thethe
amount
required
byby
thethe
load.
the electricity
production
exceeds
amount
required
load.This
Thisexcess
excessisisused
usedtotorecharge
recharge the
the
batteries,
case of
ofthe
thebattery-based
battery-basedsystem,
system,and
andtoto
produce
hydrogen
through
electrolysis,
in
batteries, in the case
produce
hydrogen
through
electrolysis,
in the
the
of the
cell-powered
system.
In red
the area,
red area,
or little
electricity
is produced
the
casecase
of the
fuelfuel
cell-powered
system.
In the
no orno
little
electricity
is produced
with with
the solar
solar
panels,
the storage
system
intervenes.
panels,
thus, thus,
the storage
system
intervenes.
Figure
electricityproduction
productionfrom
fromphotovoltaics
photovoltaics
during
winter
months
compared
with
Figure 1. Average
Average electricity
during
winter
months
compared
with
the
the
energy
consumption
same
season.
The
area
green
represents
produced
energy
that
energy
consumption
for for
thethe
same
season.
The
area
in in
green
represents
thethe
produced
energy
that
is
notnot
directly
used
by the
and isand
stored
hydrogen
production
or batteryor
charging),
is
directly
used
by household
the household
is (through
stored (through
hydrogen
production
battery
while in the
red area
the
stored
is used
by the
household.
charging),
while
in the
red
area energy
the stored
energy
is used
by the household.
On
basis of
ofthese
theseconsiderations,
considerations,both
both
systems
were
sized
being
self-sufficient
for days
two
On the
the basis
systems
were
sized
for for
being
self-sufficient
for two
days
in
the
worst
conditions,
i.e.,
with
the
irradiation
data
of
December.
The
two
systems,
in the worst conditions, i.e., with the irradiation data of December. The two systems, the schemesthe
of
schemes
which are
reported2 in
Figures
2 and
3, storage
differ inunit,
the which
storageisunit,
which isbyrepresented
by
which areofreported
in Figures
and
3, differ
in the
represented
a battery pack
ainbattery
pack
inan
one
case, and an
electrolyzer
a fuel
cellother
system
in the other case.
one case,
and
electrolyzer
coupled
with acoupled
fuel cellwith
system
in the
case.
As
the
average
daily
consumption
of
the
examined
household
was
estimated
As the average daily consumption of the examined household was estimated to
to be
be 11
11 kWh
kWh with
with
33 kW
maximum
load,
a
fuel
cell
with
a
3
kW
nominal
power
output
will
be
considered.
The
hydrogen
kW maximum load, a fuel cell with a 3 kW nominal power output will be considered. The hydrogen
necessary
necessary for
for two
two days
days of
of self-sufficiency
self-sufficiency is
is produced
produced by
by an
an electrolyzer.
electrolyzer. In
In order
order to
to produce
produce the
the
necessary
amount
of
hydrogen
during
the
sunny
hours
of
one
day,
a
nominal
power
input
necessary amount of hydrogen during the sunny hours of one day, a nominal power input of
of 55 kW
kW
is
is considered.
considered. Hydrogen
Hydrogenwill
willbe
bestored
storedat
at30
30bar,
bar, which
whichisisthe
thepressure
pressurereleased
releasedby
bythe
theelectrolyzer,
electrolyzer,
into
type
I
aluminum
tanks
with
an
internal
volume
of
50
L.
For
two
days
of
self-sufficiency
into type I aluminum tanks with an internal volume of 50 L. For two days of self-sufficiency 10
10 tanks
tanks
are
needed,
but
since
standard
cylinder
bundles
are
composed
of
12
tanks,
two
additional
cylinders
are needed, but since standard cylinder bundles are composed of 12 tanks, two additional cylinders
are
are added
added to
to the
the system.
system. The
Thehydrogen-based
hydrogen-based system
system needs
needs an
an additional
additional photovoltaic
photovoltaic array
array because
because
of
the
electrolyzer
power
requirements.
A
simplified
scheme
of
this
system
is
shown
in
Figure 2.
2.
of the electrolyzer power requirements. A simplified scheme of this system is shown in Figure
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Figure
2. Scheme
of the
fuelfuel
cell-based
stationary
system.
Figure
2. Scheme
of the
cell-based
stationary
system.
Figure 2. Scheme of the fuel cell-based stationary system.
TheThe
battery-based
ofwhich
which is
reported
in Figure
is composed
of 12
battery-basedsystem,
system,the
the scheme
reported
in Figure
3, is 3,
composed
of 12 batteries,
The battery-based
system,
the
scheme of
of whichis is
reported
in Figure
3,
is composed
of 12
batteries,
with
12
V
and
150
Ah.
with
12
V
and
150
Ah.
batteries, with 12 V and 150 Ah.
Figure 3. Scheme of the battery-based stationary system.
Figure 3. Scheme of the battery-based stationary system.
Figure 3. Scheme of the battery-based stationary system.
It is noteworthy that both systems schematized in Figures 2 and 3 have the possibility of being
It is noteworthy that both systems schematized in Figures 2 and 3 have the possibility of being
connected
the grid, if that
available.
This gives
the possibility
of conferring
extra
produced
It isto
both systems
schematized
in Figures
2 and 3the
have
theenergy
possibility
of being
connected
tonoteworthy
the grid, if available.
This gives
the possibility
of conferring
the
extra
energy
produced
to the
grid,
as
well
as
getting
this
back
during
the
night
hours.
connected
the as
grid,
if available.
This
givesthe
thenight
possibility
to the
grid, astowell
getting
this back
during
hours.of conferring the extra energy produced to
the grid, as well as getting this back during the night hours.
2.2. Mobile Application: UAV
2.2. Mobile Application: UAV
2.2. Mobile Application: UAV
In recent years the use of UAVs, traditionally related to military operations, has been gaining
In recent years the use of UAVs, traditionally related to military operations, has been gaining
years
the use ofinUAVs,
traditionally
related
to military
operations,
has been
gaining
interestIn
forrecent
civilian
applications
different
fields [24–26].
Among
these, one
particularly
promising
interest for civilian applications in different fields [24–26]. Among these, one particularly promising
interest for
civilian applications
in different
fields
[24–26].
Amongperformed
these, oneby
particularly
application
is structure
health monitoring
[27,28].
Video
inspection
drone canpromising
also be
application is structure health monitoring [27,28]. Video inspection performed by drone can also be
application
structure
health
monitoring
[27,28].equipment
Video inspection
performed
drone canare,
alsoin
be a
a valid
tool foristhe
periodical
inspection
of lifting
and cranes.
Theseby
inspections
a valid tool for the periodical inspection of lifting equipment and cranes. These inspections are, in
valid
tool forcarried
the periodical
of lifting
and
These
are,toinbe
fact,
fact,
normally
out byinspection
disassembling
andequipment
putting on
thecranes.
ground
the inspections
components
fact, normally carried out by disassembling and putting on the ground the components to be
normally
carried
out by disassembling
putting on the ground the components to be inspected,
inspected,
but
this procedure
is expensive and time-consuming.
inspected, but this procedure is expensive and time-consuming.
but
this
procedure
is expensive
time-consuming.
For
this
application
the droneand
must
have a flying time of at least 120 min and a high stability to
For this application the drone must have a flying time of at least 120 min and a high stability to
For this
application
the drone
must have
a flying
of of
at aleast
120 octocopter
min and a [29].
highAs
stability
allow image
acquisition.
Stability
requirements
lead
to thetime
choice
coaxial
far
allow image acquisition. Stability requirements lead to the choice of a coaxial octocopter [29]. As far
to
allow
image
acquisition.
Stability
requirements
lead
to
the
choice
of
a
coaxial
octocopter
[29].
as the flying range is concerned, two power alternatives are considered: the Li-ion battery
as the flying range is concerned, two power alternatives are considered: the Li-ion battery
As far as the
flying
range devices
is concerned,
considered:demonstrated
the Li-ion battery
traditionally
used
for these
[24,30]two
andpower
a PEMalternatives
fuel cell, asare
successfully
in
traditionally used for these devices [24,30] and a PEM fuel cell, as successfully demonstrated in
traditionally
used forThe
these
devices
and a PEM
demonstrated
previous
works [31–33].
latter
is not [24,30]
a conventional
PEMfuel
fuelcell,
cell, as
butsuccessfully
a lightweight
one, suitable in
previous works [31–33]. The latter is not a conventional PEM fuel cell, but a lightweight one, suitable
[31–33].[34],
The
not a is
conventional
PEM
fuel
cell,
but a lightweight
one,
forprevious
aerospaceworks
applications
forlatter
whichisweight
a crucial issue.
This
also
determines
the need for
for aerospace applications [34], for which weight is a crucial issue. This also determines the need for
suitable
aerospace
applications
[34], for
which weight
a crucial
issue. This
alsomeans
determines
limiting
thefor
number
of auxiliary
components
necessary
for the is
fuel
cell to operate,
which
airlimiting the number of auxiliary components necessary for the fuel cell to operate, which means airthe need
limiting
thecircuit
number
of auxiliary
necessary for
to to
operate,
cooling
(no for
cooling
liquid
necessary),
andcomponents
dry-type membranes,
thatthe
dofuel
notcell
need
be
cooling (no cooling liquid circuit necessary), and dry-type membranes, that do not need to be
which means
air-coolingrepresentation
(no cooling liquid
circuit
and dry-type
that do4.not
humidified.
A simplified
of the
UAVnecessary),
fuel cell-based
system ismembranes,
shown in Figure
humidified. A simplified representation of the UAV fuel cell-based system is shown in Figure 4.
needfrom
to bethis
humidified.
simplified representation
of the UAV
fuelbattery-powered
cell-based system
is shown
Aside
PEM fuel A
cell-powered
device, a commercial
Li-ion
device
was in
Aside from this PEM fuel cell-powered device, a commercial Li-ion battery-powered device was
Figure 4. Aside from this PEM fuel cell-powered device, a commercial Li-ion battery-powered device
considered.
considered.
was considered.
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Figure 4.
4. Scheme
Scheme of
Figure
of the
thePEM
PEMfuel
fuelcell-based
cell-basedUAV.
UAV.
Figure 4. Scheme of the PEM fuel cell-based UAV.
Simplified schemes of the battery-based and the fuel cell-based drones are reported in Figures 5
Figure
4.the
Scheme
of the PEM fuel
cell-based
UAV.
Simplified
schemes
ofbattery-based
battery-based
fuel
cell-based
arein reported
Simplified
schemes
of the
and theand
fuelthe
cell-based
drones aredrones
reported
Figures 5 in
and 6, respectively.
Figures
5
and
6,
respectively.
and 6, respectively.
Simplified schemes of the battery-based and the fuel cell-based drones are reported in Figures 5
and 6, respectively.
Figure 5. Simplified scheme for the battery-powered UAV.
Figure
5. Simplified
scheme
battery-powered
UAV.
Figure
5. Simplified
scheme
for for
the the
battery-powered
UAV.
The dashed arrow in Figure 6, going from the gas tanks to the fuel cell represents the hydrogen
Figure 5. Simplified scheme for the battery-powered UAV.
flow,
which is
regulated
by the
electronics.
auxiliary
components
of the fuel
system,
TheThe
dashed
arrow
in Figure
6,control
going
from
thethe
gasThe
tanks
to the
fuel
cellcell
represents
thecell
hydrogen
dashed
arrow
in Figure
6, going
from
gas
tanks
to the
fuel
represents
the
hydrogen
such
as air arrow
compressor,
blower
and from
solenoid
valves,
require
power
of about
22 W. For this
The
dashed
in Figure
6,control
going
the gas
tanks
to the afuel
cell supply
represents
thefuel
hydrogen
flow,
which
is
regulated
by
the
electronics.
The
auxiliary
components
of
the
cell
system,
flow,
which
is
regulated
by
thebecontrol
electronics.
The auxiliary
of the fuel
celldrone
system,
reason,
an
extra
power
must
supplied
to the
aside
fromcomponents
the 728
W required
by the
flow,
which
is
regulated
by
the
control
electronics.
Thesystem,
auxiliary
of the
cell22
system,
such
as air
compressor,
blower
and
solenoid
valves,
require
acomponents
power
supply
offuel
about
W.
ForFor
this
such
as
air
compressor,
blower
and
solenoid
valves,
require
a
power
supply
of
about
22
W.
engines
(commonblower
to both
systems).
Thus, the
two asystems,
although
designed
for this
the samethis
such
as
air
compressor,
and
solenoid
valves,
require
power
supply
of
about
22
W.
For
reason,
an an
extra
power must
be be
supplied
to the
system,
aside
from
thethe
728728
WW
required
by by
thethe
drone
reason,
extra
must
supplied
to the
system,
aside
from
required
drone
application
andpower
size,
are
different
the amount
of
power
effectively
supplied
to drone
the engines.
reason,
an(common
extra power
must
beslightly
supplied
to
the in
system,
aside
from
thealthough
728
W required
by the
engines
to
both
systems).
Thus,
the
two
systems,
designed
for
the
same
engines
(common
to
both
systems).
Thus,
the
two
systems,
although
designed
for
the
same
application
As (common
a consequence,
considering
1 Thus,
kW power,
the systems,
battery-based
system
has a slightly
longer
flying
engines
to are
both
systems).
although
designed
for the
same
application
and
size,
slightly
different
inthe
the two
amount
of power
effectively
supplied
to the
engines.
and
size,
arerespect
slightly
different
insystem.
the amount
of power
effectively
supplied
to the
engines.
As a
time,
with
to
the
fuel
cell
application and size, are slightly different in the amount of power effectively supplied to the engines.
Asconsequence,
a consequence,
considering
1
kW
power,
the
battery-based
system
has
a
slightly
longer
flying
the battery-based
battery-basedsystem
systemhas
hasa aslightly
slightly
longer
flying time,
As a consequence,considering
considering 11 kW
kW power,
power, the
longer
flying
time,
with
respect
to the
fuel
cell
system.
with
respect
to
the
fuel
cell
system.
time, with respect to the fuel cell system.
Figure 6. Simplified scheme for the fuel cell-powered UAV.
Unlike for the stationary
application,
for the
application
the hydrogen production aspect
Figure
6. Simplified
scheme
for mobile
the fuel
cell-powered
Figure
6. Simplified
scheme
for the
fuel
cell-powered
UAV.UAV.
Figure
6.
Simplified
scheme
for
the
fuel
cell-powered
UAV.400 nl/h with a power
has not been examined. However, considering a small electrolyzer producing
supplyfor
equal
tostationary
2.8 kW,application,
the
amountfor
of for
hydrogen
necessary
forthe
thehydrogen
fuelhydrogen
cell-powered
drone
running
Unlike
for
the
application,
mobile
application
the
production
aspect
Unlike
the
stationary
thethe
mobile
application
production
aspect
for
120
min
can
be
produced
in
about
250
min,
with
a
total
energy
consumption
of
11.8
kWh.
Unlike
for the stationary
application,
mobile
application
the400
hydrogen
production
aspect
has
However,
considering
afor
small
electrolyzer
producing
nl/h
awith
power
hasnot
notbeen
beenexamined.
examined.
However,
considering
athe
small
electrolyzer
producing
400 with
nl/h
a power
has equal
not
been
examined.
However,
considering
anecessary
smallfor
electrolyzer
producing
400
nl/h
with
a power
supply
toto2.8
thethe
amount
of hydrogen
necessary
the
cell-powered
drone
running
supply
equal
2.8kW,
kW,
amount
of
hydrogen
for fuel
the fuel
cell-powered
drone
running
3. Cost Analysis
for
can
in in
about
250of
min,
with
a total
energy
of 11.8
supply
equal
toproduced
2.8
kW, the
amount
hydrogen
necessary
forconsumption
theconsumption
fuel cell-powered
drone
running for
for120
120min
min
canbebe
produced
about
250
min,
with
a total
energy
ofkWh.
11.8
kWh.
be a deciding
factor250
in min,
the choice
two different
systems
for applications.
In
120 minCost
can can
be produced
in about
with abetween
total energy
consumption
of 11.8
kWh.
3.3.Cost
Analysis
order
to identify which solutions are more competitive and the impact of the energy storage solution
Cost
Analysis
3. on
Cost Analysis
of thefactor
system,
a cost
analysis
has been
performed
for both
andInmobile
Costthe
cantotal
be acost
deciding
in the
choice
between
two different
systems
forstationary
applications.
Cost can be a deciding factor in the choice between two different systems for applications. In
order
solutions
areare
more
competitive
andand
the
impact
of the
storage
solution
Cost
canwhich
be
a deciding
factor
inmore
the
choice
between
two
systems
for
applications.
In order
ordertotoidentify
identify
which
solutions
competitive
thedifferent
impact
ofenergy
the energy
storage
solution
on the
total
cost
of
the
system,
a
cost
analysis
has
been
performed
for
both
stationary
and
mobile
to identify which solutions are more competitive and the impact of the energy storage solution on the
on the total cost of the system, a cost analysis has been performed for both stationary and mobile
Challenges 2017, 8, 9
6 of 15
Challenges 2017, 8, 9
6 of 15
total cost of the system, a cost analysis has been performed for both stationary and mobile applications.
applications
. The
estimated
costscomponents
of the main components
the two systems
stationary
areinreported
The estimated
costs
of the main
for the two for
stationary
aresystems
reported
Table 1,
in
Table
1,
and
their
distribution
and
total
prices
are
shown
in
Figure
7.
and their distribution and total prices are shown in Figure 7.
Table
Table 1. Costs
Costs of
of the
the main
main components
components for the stationary systems.
System
System
Fuel
cellcell
Fuel
Battery
Battery
Component
Component
Fuel cell system
Fuel cell system
Type
I gas tanks
Type I gas tanks
PV
(photovoltaic)
panels
PV (photovoltaic) panels
Auxiliary
components
Auxiliary components
Li-ion
Li-ionbatteries
batteries
PV
panels
PV panels
Auxiliary components
Auxiliary components
Cost (€)
30,000
30,000
7500
7500
5500
5500
7000
7000
18,000
18,000
3500
3500
3500
3500
Cost (€)
Figure 7. Total costs and cost distributions for the two alternatives of the stationary systems.
Figure 7. Total costs and cost distributions for the two alternatives of the stationary systems.
As can be seen from Figure 7, although the total costs are very different for these solutions, the
can be seen
fromthe
Figure
7, although
the total
are very
different
these solutions,
price As
distribution
among
components
is similar,
withcosts
the energy
storage
unitfor
representing
more
the
price
distribution
among
the
components
is
similar,
with
the
energy
storage
unit
representing
more
than half of the total cost for both systems. The reason is two-fold: on one hand, the high number
of
than
half
of
the
total
cost
for
both
systems.
The
reason
is
two-fold:
on
one
hand,
the
high
number
batteries required by the battery-powered system to guarantee two days of self-sufficiency gives of
a
batteries required
byprice,
the battery-powered
system
tothe
guarantee
two
days
of self-sufficiency
gives
significant
rise to the
while, on the other
hand,
high cost
of the
electrolyzer
+ PEM fuel
cella
significant
rise to the price,
while,
on the
otherpenetration
hand, the high
cost of
the electrolyzer
PEM
fuel cell
system
is, nowadays,
fixed by
the low
market
of these
devices.
The use of+ gas
cylinders
system
is,
nowadays,
fixed
by
the
low
market
penetration
of
these
devices.
The
use
of
gas
cylinders
gives another significant contribution to the cost of the hydrogen technology system.
givesDifferent
another significant
the
hydrogen
system. for which the
trends cancontribution
be observedtointhe
thecost
caseofof
the
selected technology
mobile application,
trends
can be2,observed
the case ofamong
the selected
mobile application,
for which
the costs
costs Different
are reported
in Table
and theirin
distribution
the components
is summarized
in Figure
8.
are reported in Table 2, and their distribution among the components is summarized in Figure 8.
Table 2. Costs of the main components for the mobile systems.
Table 2. Costs of the main components for the mobile systems.
System
Component
FuelComponent
cell system
Engines
structure
Fueland
cell system
Engines
Fuel cell
Type IIIand
gasstructure
tanks
Type
III
gas
tanks
Fuel cell
Auxiliary components
Auxiliary components
Image
acquisition
Image
acquisition system
system
Li-ion battery
Li-ion battery
Engines
and
Engines
andstructure
structure
Battery
Battery
Auxiliarycomponents
components
Auxiliary
Image
acquisition system
system
Image
acquisition
System
Cost (€)
Cost
(€)
13,200
5800
13,200
5800
2200
2200
3200
3200
2600
2600
1000
1000
5800
5800
1600
1600
2600
2600
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7 of 15
7 of 15
Figure 8. Total costs and cost distributions for the two alternatives of the mobile system.
Figure 8. Total costs and cost distributions for the two alternatives of the mobile system.
In this case, the PEM fuel cell is responsible for about half of the total cost of the fuel cell-powered
In this case,
fuelincell
responsible for about
total
cost impact,
of the fuel
drone,
while the
thePEM
battery
theisbattery-powered
systemhalf
hasofa the
much
lower
notcell-powered
only if
compared
to battery
the fuel in
cell
of battery-powered
the fuel cell-basedsystem
mobile has
system,
but also
to impact,
the previously-presented
drone,
while the
the
a much
lower
not only if compared
stationary
application.
This is
simplybut
duealso
to the
number of batteries battery-based
required
to thebattery-based
fuel cell of the
fuel cell-based
mobile
system,
todifferent
the previously-presented
by
the
two
applications.
In
the
case
of
the
UAV,
a
single
battery
is
enough
for
a
single
run
while,
stationary application. This is simply due to the different number of batteries required by for
the two
the stationary application, 12 batteries are necessary to guarantee two days of self-sufficiency. The
applications.
In the case of the UAV, a single battery is enough for a single run while, for the stationary
impact of the engines and structure of the drone to the total cost of the drone, as well as that of the
application, 12 batteries are necessary to guarantee two days of self-sufficiency. The impact of the engines
control and image acquisition part, is quite different for the two systems, even if the absolute cost is
and structure
of the drone to the total cost of the drone, as well as that of the control and image acquisition
obviously the same. This result indicates a very different contributions of the two energy storage
part, methods
is quite different
the
systems, even if the absolute cost is obviously the same. This result
to the totalfor
cost
oftwo
the drone.
indicates In
a very
different
of the two
storage
to the
total and
coststructure.
of the drone.
the case
of the contributions
battery-based drone,
52% energy
of the total
pricemethods
is due to the
engines
In the
case
of the battery-based
theproduction
total priceofisthis
duematerial
to the engines
structure.
This
can
be attributed
to the use ofdrone,
carbon 52%
fiber.ofThe
is, in fact,and
energyand
capital-intensive.
Therefore,
a
large
effort
is
being
done
to
develop
new
production
technologies
This can be attributed to the use of carbon fiber. The production of this material is, in fact, energy- and
of carbon fiber,Therefore,
in order to
significantly
costsnew
[35].production
Structure and
engines
capital-intensive.
a large
effort isreduce
beingmanufacturing
done to develop
technologies
of
represent
21%
of
the
total
price
of
the
fuel
cell-powered
UAV.
In
this
case,
however,
the
type
IIIrepresent
gas
carbon fiber, in order to significantly reduce manufacturing costs [35]. Structure and engines
partly made of carbon fiber and contribute to 8% of the total price of the system, suggesting
21% tanks
of theare
total
price of the fuel cell-powered UAV. In this case, however, the type III gas tanks are
the need of an improvement in composite tank manufacturing [36].
partly made of carbon fiber and contribute to 8% of the total price of the system, suggesting the need
The systems examined for the two applications show the same main critical aspect from a cost
of anpoint
improvement
in composite tank manufacturing [36].
of view: the higher impact of the fuel cell with respect to Li-ion batteries. In fact, the latter
The systems
examined
for the
two applications
show
same
main
critical aspect
fromofa cost
represents
a mature
technology
already
commercialized
on athe
large
scale.
In particular,
in the case
pointselected
of view:
the
higher
impact
of
the
fuel
cell
with
respect
to
Li-ion
batteries.
In
fact,
the latter
applications, battery-powered drones are already available at different prices and sizes,
represents
a mature
technology
commercialized
on a largepanels,
scale. and
In particular,
in the
while for
stationary
applicationalready
kits containing
batteries, photovoltaic
controllers can
be case
purchased
in a variety battery-powered
of power options. drones are already available at different prices and sizes,
of selected
applications,
commercial
situation kits
of fuel
cell technology
is, at present,
quite different,
thesecontrollers
products not
while forThe
stationary
application
containing
batteries,
photovoltaic
panels, and
can be
yet
being
commercialized
on
a
large
scale.
Their
production
process,
which
still
needs
improvement
purchased in a variety of power options.
[37], makes them quite expensive. If there is a market for PEM fuel cells for stationary use (e.g., smallThe commercial situation of fuel cell technology is, at present, quite different, these products not
scale CHP), when PEM fuel for mobile and aerospace applications are considered, the prices increase
yet being commercialized on a large scale. Their production process, which still needs improvement [37],
significantly. This is due to the use of lightweight materials and to a significantly lower diffusion on
makes
quite
there
a market
for PEM
fuel cells
for stationary
use (e.g.,
small-scale CHP),
thethem
market
of expensive.
this type of If
fuel
cell,iswhen
compared
to similar
systems
for stationary
applications.
when PEM fuel for mobile and aerospace applications are considered, the prices increase significantly.
This is
the Assessment
use of lightweight materials and to a significantly lower diffusion on the market of this
4. due
Life to
Cycle
type of fuel
cell,
when
compared
to similar
systems for
stationary
applications.
Life cycle assessment
(LCA)
is an important
tool
to evaluate
the environmental impact of a
product, as described by the ISO 14040/14044 methodology [38,39]. LCA has been already carried out
on stationary energy-storage systems on both battery-based [40,41] and fuel cell-based systems [42–
44].
novelty
of this study
is given
a comparison
between
the twothe
different
solutions, sized
for of a
LifeThe
cycle
assessment
(LCA)
is anbyimportant
tool
to evaluate
environmental
impact
the
same
conditions
for
the
stationary
application.
As
far
as
the
UAV
is
concerned,
to
our
knowledge,
product, as described by the ISO 14040/14044 methodology [38,39]. LCA has been already carried out
no previous LCA studies have been reported.
4. Life Cycle Assessment
on stationary energy-storage systems on both battery-based [40,41] and fuel cell-based systems [42–44].
The novelty of this study is given by a comparison between the two different solutions, sized for the
same conditions for the stationary application. As far as the UAV is concerned, to our knowledge,
no previous LCA studies have been reported.
Challenges 2017, 8, 9
8 of 15
4.1. Goal and Scope
The goal of this study is to obtain an overview of the potential environmental impacts of the
described systems, identifying the main bottlenecks associated with the manufacturing process of
corresponding components. The functional unit of an LCA study is the reference to which all of the
inputs and outputs are related, thus allowing a comparison among different systems. In this study the
systems examined have different applications and sizes, so a functional unit of 1 kW power supplied
has been chosen.
4.2. Inventory
The data used for this LCA study have been taken from the Ecoinvent database [45].
Components and materials composing the systems are listed in the Tables 3–6 (left column),
together with data taken from Ecoinvent (right column) to model them. All elements are rescaled on
the basis of the system being examined, as explained later in detail.
4.2.1. Inventory for the Stationary Systems
The inventory for the fuel cell-based stationary system has been grouped in Table 3
Table 3. Inventory for the fuel cell- based stationary system.
Components
Data from Ecoinvent
Polycrystalline silicon solar panel (32 × 0.25 kW)
PEM Fuel cell (3 kW)
Alkaline electrolyzer (5 kW)
Inverter (3 kW)
Solar controller
Polycrystalline silicon solar panel (0.21 kW)
PEM fuel cell (2 kW)
PEM fuel cell (2 kW)
Inverter (2.5 kW)
Electric scooter controller
Auxiliary Components for the Fuel Cell System
Aluminum gas tanks (12 × 50 l)
Plastics (6 kg)
Steel (356.4 kg)
Connection cables (145 m)
Li-ion batteries for startup (3.6 kWh)
Brass (0.6 kg)
Steel (1.1 kg)
Steel (0.6 kg)
Drawing of a wrought aluminum alloy (1 kg)
Molding of bottle grade PET granulate (1 kg)
Galvanized steel (1 kg)
Connector cable for computer (1 m)
Li-ion battery for electric vehicle
Brass (1 kg) + Brass casting
Stainless steel (1 kg) + average metal working
for manufacturing of a chromium steel product
Chromium steel pipe (1 kg)
The PEM fuel cell in Ecoinvent [45], with a nominal power output of 2 kW, has been rescaled on
the 3 kW PEM fuel cell of the fuel cell system. Due to the unavailability of data on alkaline electrolyzers,
this device has been modeled with the same rescaled PEM fuel cell, as discussed in [25]. The inventory
for the battery-based stationary system has been grouped in Table 4.
Table 4. Inventory for the battery-based system.
Components
Data from Ecoinvent
Polycrystalline silicon solar panel (20 × 0.25 kW)
LiFePO4 batteries (22 kWh)
Inverter (3 kW)
Solar controller
Polycrystalline silicon solar panel (0.21 kW)
LiMn2 O4 battery for electric vehicle (2 kWh)
Inverter (2.5 kW)
Electric scooter controller
Auxiliary Components for the Fuel Cell System
Steel (222.7 kg)
Connection cables (100 m)
Galvanized steel (1 kg)
Connector cable for computer (1 m)
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9 of 15
Even though the photovoltaic panels present in Ecoinvent [45] have a lower watt-peak with
respect to those reported in the datasheet of the panels considered for this study, they comprise of the
same number of cells. It is, thus, reasonable to consider the use of a similar amount of materials for
their manufacturing.
4.2.2. Inventory for the Mobile System
The inventory for the fuel cell-based UAVs is shown in Table 5.
Table 5. Inventory for the fuel cell-based mobile system.
Components
Data from Ecoinvent
PEM Fuel cell 1 kW
PEM fuel cell 2 kW
Engines and structure
Copper production (1.6 kg) + wires drawing
PAN fiber production (2.92 kg)
Aluminum production (0.3 kg) + impact extraction
Gas tanks
Aluminum production (1.45 kg) + sheet rolling
PAN fiber production (1.21 kg)
Liquid epoxy resin production (0.81 kg)
Auxiliary Components for Fuel Cell System
Printed circuit board
Stainless steel
Plastics
Copper
Titanium
Brass
Air filter
Printed wiring board for power supply unit
Chromium steel production (secondary) (0.33 kg) + Impact extrusion
Polyethylene production (0.3 kg) + Injection molding
Copper production (0.17 kg)
Titanium production (0.17 kg)
Brass casting (0.07 kg)
Polyethylene fleece (0.05 kg)
Since data on carbon fiber (CF) were not available in Ecoinvent [45], polyacrylonitrile (PAN)
production was considered, which is used as a precursor to obtain carbon fiber. Being that PAN is
a precursor, the conversion processes of the former into carbon fiber is not accounted for and, thus,
the impact of this process will be underestimated. According to a manufacturer [46] the energy input
for CF production from PAN is 72 MJ/kg, while the production of PAN requires 69.3 MJ/kg [47].
According to another study [48], the energy input for the overall process of CF production ranges from
286 to 704 MJ/kg. These energy input data give an idea of the potential environmental impacts of the
associated processes: from these values it seems that the impact of CF production is three times higher
than that of PAN fiber (or even more, according to Duflou et al. [48]). For copper, titanium, and brass,
due to their low amount, only production has been considered because the contribution of further
processing is negligible. The inventory for the battery-based UAVs is shown in Table 6.
Table 6. Inventory for the battery-based mobile system.
Components
Data from Ecoinvent
Li-ion battery 1.5 kWh
LiMn2 O4 battery for electric vehicle 2 kWh
Copper production (1.6 kg) + wire drawing
Engines and structure
PAN fiber production (2.92 kg)
Aluminum production (0.3 kg) + impact of extraction
Auxiliary Components for Battery System
Printed circuit board
Printed wiring board for power supply unit
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Challenges
2017, 8, 9
4.3.
LCA
4.3.
LCA Results
Results
10 of 15
performed
Pro 8.2
LCA
was
performed by
by means
means of
of the
the commercial
commercial software
software Sima
Sima Pro
8.2 (PRé
(PRé Sustainability,
Sustainability,
4.3.LCA
LCA was
Results
Amersfoort,
The
Netherlands)
[49].
The
impact
assessment
method
chosen
was
Impact
Amersfoort, The Netherlands) [49]. The impact assessment method chosen was Impact
2002+
[50].
LCA
was
performed
by
means
of
the
commercial
software
Sima
Pro
8.2
(PRé
Sustainability,
2002+
Globalpotential
warming(GWP)
potential
(GWP)
and non-renewable
energy
have
been considered
as
Global[50].
warming
and
non-renewable
energy have
been
considered
as impact
Amersfoort, The Netherlands) [49]. The impact assessment method chosen was Impact 2002+ [50].
impact
categories.
categories.
Global warming potential (GWP) and non-renewable energy have been considered as impact
The
impact assessment
assessmentresults
results
the stationary
and mobile
are reported
The impact
for for
the stationary
and mobile
systemssystems
are reported
in Figuresin9
categories.
Figures
9respectively.
and 10, respectively.
and 10,The
impact assessment results for the stationary and mobile systems are reported in Figures 9
and 10, respectively.
Figure 9. Impact distribution for the main components of the stationary systems for global warming
Figure
9. 9.
Impact
of the
thestationary
stationarysystems
systemsforfor
global
warming
Figure
Impactdistribution
distributionfor
forthe
themain
main components
components of
global
warming
potential and
and non-renewable
non-renewableenergy.
energy.
potential
potential and non-renewable energy.
Figure
10.
Impactdistribution
distributionfor
for the
the main
main components
components
for
global
warming
Figure
10.
Impact
distribution
for
the
main
componentsof
ofthe
themobile
mobilesystems
systems
for
global
warming
Figure
10.
Impact
of
the
mobile
systems
for
global
warming
potential and non-renewable energy.
potential
potential and
and non-renewable
non-renewableenergy.
energy.
LCA results show similar trends for stationary and mobile applications. As can be noticed in the
LCA results
results show
show similar
similar trends for
for stationary
stationaryand
andmobile
mobileapplications.
applications. As
As can
can be
be noticed
noticed in
in the
LCA
Figures
9 and 10,
both fuel celltrends
and battery-based
systems
have low environmental
burdens.
In fact,the
Figures 99 and
and 10,
10, both
both fuel
fuel cell
cell and
and battery-based
battery-based systems
systems have
have low environmental
environmental burdens.
burdens. In
In fact,
fact,
Figures
for the stationary
application,
the GWP is 1% and
3%, for thelow
battery-based and fuel
cell-based
for
the
stationary
application,
the
GWP
is
1%
and
3%,
for
the
battery-based
and
fuel
cell-based
forsystems,
the stationary
application,
theitGWP
1%29%,
andrespectively,
3%, for the battery-based
fuel cell-based
systems,
respectively,
whereas
is 5% is
and
for the mobileand
application.
These values
systems, respectively,
whereas
it is
5% respectively,
and 29%, respectively,
for the
mobile application.
These
values
respectively,
whereas
it
is
5%
and
29%,
for
the
mobile
application.
These
values
are
are rather low, if compared to GWP of other components for the same systems. For example, in rather
the
are
rather
low,
if
compared
to
GWP
of
other
components
for
the
same
systems.
For
example,
in the
the
low,
if compared
to GWP
of other components
the same
systems.
For example,
the case
case
of the stationary
application,
photovoltaicfor
panels
provide
85% and
31% of theinGWP
for of
the
case
of
the
stationary
application,
photovoltaic
panels
provide
85%
and
31%
of
the
GWP
for
the
stationary
application,
photovoltaic
panels provide
85% and
of the GWP
for the battery-based
battery-based
and fuel
cell-based systems,
respectively.
For 31%
the mobile
systems,
engine and
battery-based
andUAV
fuelresult
cell-based
respectively.
Forthe
the
mobile
the cell-based
engine
and
and
fuel cell-based
systems,
respectively.
systems,
the
engine systems,
andand
structure
of the UAV
structure
of the
in 58%systems,
andFor
12%the
of mobile
the GWP
for
battery-based
fuel
structure
of
the
UAV
result
in
58%
and
12%
of
the
GWP
for
the
battery-based
and
fuel
cell-based
systems,
respectively.
result
in 58%
and 12% of the GWP for the battery-based and fuel cell-based systems, respectively.
systems,
respectively.
Although
directcomparison
comparisonwith
with previous
previous studies
methods
forfor
Although
a adirect
studies isisnot
noteasy
easydue
duetotothe
thedifferent
different
methods
Although
a direct
comparison
with previous
studiessystems
is not easy
due to the
different
methods
for
impact
assessment
used,
similarbattery-based
battery-based
investigated
byby
Balcombe
et et
al.al.
[51]
impact
assessment
used,
similar
stationary
systems
investigated
Balcombe
[51]
impact
assessment
used,
similar
battery-based
stationary
systems
investigated
by
Balcombe
et
al.
[51]
and
Kabakian
et
al.
[40]
confirm
the
dominating
impact
of
the
solar
panels
with
respect
to
batteries.
and Kabakian et al. [40] confirm the dominating impact of the solar panels with respect to batteries.
NoKabakian
detailed LCA
on stationary
systems coupling
PVthe
and
fuelpanels
cells are
available.
study
and
et al.studies
[40] confirm
the dominating
impact of
solar
with
respectIntoabatteries.
No detailed LCA studies on stationary systems coupling PV and fuel cells are available. In a study
Challenges 2017, 8, 9
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Challenges 2017, 8, 9
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No detailed LCA studies on stationary systems coupling PV and fuel cells are available. In a study by
by
Bauer
et [15]
al. [15]
a comparison
between
battery
electric
vehicles,
batteries
Bauer
et al.
in aincomparison
between
battery
andand
fuelfuel
cell cell
electric
vehicles,
bothboth
batteries
and and
fuel
fuel
cells
resulted
in
having
lower
environmental
burdens
for
GWP
with
respect
to
the
glider
of
the
cells resulted in having lower environmental burdens for GWP with respect to the glider of the vehicle
vehicle
(i.e.,
the
vehicle
without
drivetrain).
Even
if
the
structure
of
the
drone
and
the
glider
of
the
(i.e., the vehicle without drivetrain). Even if the structure of the drone and the glider of the vehicle
vehicle
in [15]
are different
in the materials
used
and in with
weight
with to
respect
to the battery/fuel
cell, a
in [15] are
different
in the materials
used and
in weight
respect
the battery/fuel
cell, a similar
similar
trend
can
be
observed
in
Figure
10,
as
the
structure
of
the
UAV
represents
the
largest
trend can be observed in Figure 10, as the structure of the UAV represents the largest contribution to
contribution
to the
total impact,
the case
of the battery system.
the total impact,
especially
in theespecially
case of theinbattery
system.
The
impact
of
the
batteries
is
mainly
given
by
the by
electrode
manufacturing
[52], although
The impact of the batteries is mainly given
the electrode
manufacturing
[52],
distribution
of
the
impacts
between
anode
and
cathode
depends
on
the
battery
chemistry
[53]. [53].
The
although distribution of the impacts between anode and cathode depends on the battery chemistry
environmental
performance
of batteries
can becan
enhanced
by improving
the manufacturing
process,
The environmental
performance
of batteries
be enhanced
by improving
the manufacturing
for
example,
by
reducing
or
replacing
some
elements,
like
gallium
used
for
the
resistors
[54],[54],
or
process, for example, by reducing or replacing some elements, like gallium used for the resistors
improving
recycling
and
recovery
of
materials
[55].
or improving recycling and recovery of materials [55].
Similar
cells,
where
thethe
largest
contribution
to
Similar considerations
considerationscan
canbe
beoutlined
outlinedininthe
thecase
caseofoffuel
fuel
cells,
where
largest
contribution
the
environmental
impact
is
given
by
the
platinum
group
metals.
The
impact
of
platinum
group
to the environmental impact is given by the platinum group metals. The impact of platinum group
metals,
metals, although
although their
their small
small amount,
amount, lies
lies mainly
mainly in
in their
their extraction
extraction process,
process, as
as suggested
suggested in
in previous
previous
studies
[56,57]
and
confirmed
by
the
impacts
flowchart
shown
in
Figure
11.
studies [56,57] and confirmed by the impacts flowchart shown in Figure 11.
Environmental impacts flowchart for the PEM fuel cell.
Figure 11. Environmental
As
can be
beseen
seenininFigures
Figures
9 and
both
hydrogen-based
systems,
a significant
impact
is
As can
9 and
10,10,
forfor
both
hydrogen-based
systems,
a significant
impact
is given
given
by
the
gas
tanks
(62%
for
the
stationary
system
and
49%
for
the
mobile
one).
It
must
be
pointed
by the gas tanks (62% for the stationary system and 49% for the mobile one). It must be pointed out that
out
due
to the application
different application
requirements,
different
types
of been
tankschosen
have been
chosen
for
due that
to the
different
requirements,
different types
of tanks
have
for the
systems:
the
Typetanks
I aluminum
[58] for the
stationary
system
and Type III
(aluminum
Typesystems:
I aluminum
[58] for tanks
the stationary
system
and Type
III (aluminum
liner
wrapped liner
with
wrapped
with
carbon
fiber
[58])
for
the
mobile
application,
due
to
the
stringent
weight
issues.
carbon fiber [58]) for the mobile application, due to the stringent weight issues. Although different,
Although
different,types
both have
gas cylinders
types have burdens,
high environmental
burdens,
mainly
associated
both gas cylinders
high environmental
mainly associated
with
the production
with the production of the materials they are made of. In the case of the Type III tank, one of the main
contributors is the PAN fiber production. However, the last step of PAN conversion into carbon fiber
has not been considered in this study, as previously reported in paragraph 4.2.2. In other studies, the
Challenges 2017, 8, 9
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of the materials they are made of. In the case of the Type III tank, one of the main contributors is
the PAN fiber production. However, the last step of PAN conversion into carbon fiber has not been
Challenges 2017,
8, 9 study, as previously reported in paragraph 4.2.2. In other studies, the contribution
12 of 15 of
considered
in this
carbon fiber was considered [46–48]. In [46] the authors report that the production of carbon fiber from
contribution of carbon fiber was considered [46–48]. In [46] the authors report that the production of
PAN is a very energy-intensive process, involving the thermosetting of PAN fibers into an oxidizing
carbon fiber from PAN is a very energy-intensive process, involving the thermosetting of PAN fibers
atmosphere at 200–300 ◦ C and carbonizing them at 1000–1700 ◦ C, leading to 80% of the total impact
into an oxidizing atmosphere at 200–300 °C and carbonizing them at 1000–1700 °C, leading to 80% of
for carbon fiber production. Both the liner of the Type III tanks and the Type I tanks for the stationary
the total impact for carbon fiber production. Both the liner of the Type III tanks and the Type I tanks
system are made of aluminum. The main contribution to the environmental impact of this material is
for the stationary system are made of aluminum. The main contribution to the environmental impact
theofelectrical
energy consumption, the most critical step being the electrolytic smelting of bauxite [59].
this material is the electrical energy consumption, the most critical step being the electrolytic
Furthermore,
this study,
primary aluminum
was considered,
which is much
less environmentally
smelting of in
bauxite
[59]. Furthermore,
in this study,
primary aluminum
was considered,
which is
friendly
than
secondary
aluminum
[59].
much less environmentally friendly than secondary aluminum [59].
5. Conclusions
5. Conclusions
In In
order
toto
compare
technologyfor
forenergy
energystorage
storage
stationary
order
comparethe
thebattery
batteryand
andfuel
fuel cell-based
cell-based technology
inin
stationary
and
mobile
applications,
analysishave
havebeen
beennormalized
normalized
per
kWh
energy
and
mobile
applications,the
theresults
resultsof
ofLCA
LCA and
and cost
cost analysis
per
kWh
energy
supplied
and
they
are
summarized
in
Figure
12.
The
mass
of
the
storage
system,
cost,
and
global
supplied and they are summarized in Figure 12. The mass of the storage system, cost, and global
warming
potential
togetherwith
withthe
the
corresponding
impact
of energy
the energy
storage
warming
potentialare
arereported,
reported, together
corresponding
impact
of the
storage
on theon
thesystem.
system.
Figure
Resultsnormalized
normalizedper
per kWh
kWh energy supplied
systems.
Figure
12.12.Results
suppliedfor
forthe
thedifferent
differentexamined
examined
systems.
Both systems examined, whether for stationary or mobile use, present similar advantages and
Both systems examined, whether for stationary or mobile use, present similar advantages and
drawbacks. For both stationary and mobile systems presented, the battery-based systems are simpler
drawbacks. For both stationary and mobile systems presented, the battery-based systems are simpler
than the fuel cell-based ones, requiring fewer auxiliary components. The latter requires a power
than the fuel cell-based ones, requiring fewer auxiliary components. The latter requires a power
supply that determines a reduction in the overall system efficiency, since this power is not used for
supply
that determines
a reduction
in the
system
since this
power is not
the household
or the flying
range. The
fueloverall
cell systems
are,efficiency,
thus, oversized
to compensate
thisused
extrafor
theconsumption
household or
the
flying
range.
The
fuel
cell
systems
are,
thus,
oversized
to
compensate
this
(and efficiency of the electrolyzer, in the case of the fuel cell-based stationary system).
extra
consumption
(andstorage
efficiency
of the electrolyzer,
in the case diffusion
of the fuel
cell-based
stationary
Systems
using battery
can benefit
from a wide commercial
of Li-ion
batteries
and
system).
Systems
using
battery
storage
can
benefit
from
a
wide
commercial
diffusion
of
Li-ion
batteries
correlated devices for the chosen application (for example, the already assembled micro-UAVs, as
well as kits containing battery packs, solar panels, controllers, and an inverter for stationary off-grid
applications), which makes the prices more attractive. On the other hand, as soon as the amount of
energy to be stored increases, new batteries have to be added, which means additional costs and the
Challenges 2017, 8, 9
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and correlated devices for the chosen application (for example, the already assembled micro-UAVs,
as well as kits containing battery packs, solar panels, controllers, and an inverter for stationary off-grid
applications), which makes the prices more attractive. On the other hand, as soon as the amount of
energy to be stored increases, new batteries have to be added, which means additional costs and the
increasing weight of the system. In stationary applications weight is not an issue. However, in UAV
applications the weight of the additional battery might not be compatible with the features of a drone
and become a limiting factor.
In FC-based systems, given the maximum power output of a fuel cell (and its fuel consumption),
the only limiting factor is the amount of hydrogen to be stored. The main drawback of fuel cell-based
systems is, at present, represented by their high cost, which is about double that of a battery-based
system of the same size and for the same applications. Fuel cell-based systems are more complex and
require a larger number of auxiliary components for their operation, which means additional weight.
This has to be taken into account, especially when considering mobile applications.
LCA results have shown that both battery and fuel cells have low environmental burdens with
respect to other components of the same systems.
Acknowledgments: This work was performed in the framework of the Piedmont Regional projects “STERIN” and
“Dron-Hy”, financed by FINPIEMONTE, POR-FESR Asse I, Attività I.1.3 Innovazione e P.M.I., Polo “Architettura
Sostenibile e Idrogeno” and Polo “Polight”, respectively.
Author Contributions: Nadia Belmonte performed cost and Life cycle assessment analysis and drafted the paper;
Carlo Luetto and Stefano Staulo defined the size and auxiliaries of the investigated systems; Paola Rizzi and
Marcello Baricco coordinated the activities and finalized the text.
Conflicts of Interest: The authors declare no conflict of interest.
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article distributed under the terms and conditions of the Creative Commons Attribution
(CC BY) license (http://creativecommons.org/licenses/by/4.0/).