Marine Electrification is the Future:
A Tugboat Case Study
Mark Hayton(&)
United States Coast Guard, Buffalo, USA
mhayton9@gmail.com
Abstract. Increased emissions regulations, global volatility of petroleum supply chains, and a significant push to source energy from renewable and sustainable sources encourages companies and governments to move away from
petroleum-based products. Research was conducted on the efficiencies and
optimal operating parameters of internal combustion engines and electric
motors, exposing situations where each would be best utilized given current
energy infrastructure. To support the claim of partially electrified solutions for
inland waterway vessels, an in-depth analysis was conducted for an inland
waterway tugboat with a rated engine of 1800 kW. The unique operating
parameters for tugboats make them prime candidates for plug-in-hybrid
propulsion solutions. In this case, the 1800 kW rated tugboat operates at
360 kW or less 87% of the time. This means that most of the operating profile
requires a very large engine to be running at low loads, wasting fuel. Proposing
electric propulsion for operating modes that require 360 kW or less yields a 62%
decrease in fuel consumption. Plug-in hybrid propulsion solutions allow for
vessels to plug-in to charging stations after the completion of each voyage.
Renewable sources like wind and solar, among others, directly feed the grid,
permitting more flexibility in the move for sustainability. New developments in
battery technology, require regulatory oversight to maintain safety compliance,
specifically regarding the standardization of charging plugs and fire suppression
systems for lithium-ion batteries. Implementing charging stations at frequented
mooring locations will open the door for sustainable technology, like electrified
propulsion solutions, to permeate the inland waterway infrastructure.
Keywords: Charging stations Smart shipping
compliance Electric propulsion
Efficiency Safety
1 Introduction
Energy diversification is closely tied to the independence of nations around the world.
Countries that source energy from a multitude of renewable energy sources will prove
resilient for generations. Global economic volatility shows the unpredictability of oil
sourcing and distribution. During global crises, supply chains are largely disrupted,
especially when sanctions are imposed on specific countries. To deal with economic
turmoil and trade disruptions, energy diversification is the solution. Traditionally
speaking, the marine industry is dominated by internal combustion engines and
steam/gas turbine propulsion systems. Although slightly different in mechanical power
© The Author(s) 2023
Y. Li et al. (Eds.): PIANC 2022, LNCE 264, pp. 868–879, 2023.
https://doi.org/10.1007/978-981-19-6138-0_77
Marine Electrification is the Future: A Tugboat Case Study
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transmission, both methods derive power from a single source: petroleum-based
products. Combustion propulsion systems have been fine-tuned and optimized over the
last century but are still limited by the theoretical efficiencies of the Otto, Rankine, and
Carnot cycles. Over the last 40 years, new ship construction has been centered largely
on internal combustion engines that have the ability to burn various petroleum-based
products. Countries walk themselves into a geopolitical and economic trap when
sourcing energy outside of their own territory.
In 2020, the International Maritime Organization (IMO) updated the Regulations for
the Prevention of Air Pollution from Ships via MARPOL 73/78 Annex VI. IMO changed
the allowable limits of sulfur content of fuel to not exceed 0.5% globally and 0.1% in
emission control areas. As a result, vessels are forced to use more expensive, cleaner fuel or
install costly exhaust gas scrubber systems. This updated regulation incentivizes companies to look for alternative means of energy. Hybrid or fully electric drives are the
solution for the marine shipping industry. Although fully electric shipping for large-scale
containerships and freighters is currently not feasible, electrification solutions for smaller
operations are realistic and lucrative. Based on recent progress, it is evident that the
maritime industry is moving towards a cleaner and more sustainable future.
The benefits of electric propulsion systems are numerous and have been implemented in some large-scale applications. For example, the United States Naval Ship
(USNS) T-AKE Class ships are powered by a diesel electric propulsion system that
boasts high maneuverability and quick start/stop capabilities, which greatly outperforms direct-link slow-speed propulsion engines. These engines need to be fully
stopped, reversed, and started again to change the rotation of the propulsion shaft.
Although the USNS T-AKE vessels use electric propulsion motors to actuate the shaft,
the primary source of energy still resides with diesel fuel. Current technology and
infrastructure deem fully electric large-scale vessels infeasible. Because of this, the
commercial maritime industry is very reluctant to move away from fossil fuels. For
example, it is very difficult to match the energy density of diesel fuel (42,800 J/g) when
using batteries as the sole fuel source.
Throughout the world, governments will need to encourage electric propulsion in
the maritime industry while still maintaining necessary standards for safety. Direct
current (DC) charging stations at mooring locations give hybrid and electric commercial river tenders, recreational boaters, and transportation vessels the opportunity to
charge after each voyage. Growing electrical applications across transportation and
power generation industries have spurred an energy revolution backed by versatility
and efficiency. However, large scale marine installation of electric or plug-in-hybrid
technology remains to be implemented. Such applications are suited for vessels with
shorter operating periods, an ideal situation for vessels operating on inland waters.
Several small-scale applications of hybridized technology have resulted in reduced
maintenance costs, increased maneuverability, and reduced consumption of petroleumbased fuel. Large-scale implementation of marine DC charging stations will yield a
cleaner, lower maintenance, propulsion solution to steer the industry away from
petroleum-based fuels. However, specific practices for the prevention and suppression
of large-scale lithium-ion battery fires have not been published or standardized. It is
essential that governments and regulatory agencies are at the forefront of battery
developmental research to ensure that maritime safety remains a priority.
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2 Propulsion Systems for Vessels
During the design process for new ship construction, engineers and naval architects
conduct an in-depth analysis of the operating characteristics of newly constructed
vessels. Sizing a propulsion system for a vessel largely relies on the needs of the
customer, which is typically outlined in the customer’s request for proposal
(RFP) package. In the commercial maritime industry, sizing a propulsion plant for a
standard vessel, like a containership or a bulk freighter, is relatively simple. The
propulsion designer considers the expected tonnage and power requirements at maximum load parameters, while also meeting the speed requirement as specified by the
RFP. In ideal situations, the vessel will be operating fully loaded with cargo for a
majority of the time, which would maximize profits for the vessel owner. Internal
combustion diesel engines are generally sized to operate at a high proportion of the
maximum continuous rating (MCR), usually around 80%–90% MCR (Harrington
1992). That range of operation typically correlates to the best range for specific fuel
consumption, meaning the engine operates most efficiently when fully loaded. Furthermore, smaller main engine load variations, while also maintaining the 80%–90%
MCR, will lead to decreased fuel consumption. For operational characteristics of large
vessels like containerships, diesel engines are functionally appropriate but retain high
operational and maintenance costs.
3 A Closer Look, Inland Waterway Tugboat
3.1
Unique Operating Parameters of a Tugboat
Traditionally speaking, tugboat designers would size the rated power output of the
engine according to the expected load at max towing capacity, which is usually around
80% of the maximum continuous rating (MCR). So far, this seems similar to the design
profile of a containership, which is designed for optimal performance when operating at
80%–90% MCR.
To model the benefits of plug-in hybrid vessels, an in-depth review of an inland
waterway tugboat will be examined. The vessel is a commercial tug with published
operational data (Boyd and Macpherson 2014). See Table 1 and Table 2 below for the
specific operating modes, conditions, and fuel specifications that will be referenced for
the calculations and results.
Table 1. Engine and fuel data (Boyd and Macpherson 2014)
Engine data & fuel
Rated RPM
Rated power (kW)
Density (kg/m3)
Heating value (J/g)
basis
1000
1800
840.00
42800
Marine Electrification is the Future: A Tugboat Case Study
871
Table 2. Tugboat operating conditions and data (Boyd and Macpherson 2014)
Mode
1
2
3
4
5
6
7
8
9
10
Standby
Transit
low
Transit
high
Assist
Assist
Assist
Assist
Barge Mv
Barge Mv
Barge Mv
Service
Speed
(kt)
Time
Percentage
Percent
Engine
Load
Engine
Output
(kW)
Idle
Transit
0
6.6
0.15
0.3
0.05
0.024
90
43.2
Mass
flow
rate of
fuel
(t/hr)
0.042
0.019
Transit
10
0.07
0.1
180
0.075
80%
60%
40%
20%
60%
40%
20%
1
1
1
1
5
5
5
0.01
0.01
0.09
0.26
0.01
0.01
0.09
0.8
0.6
0.4
0.2
0.6
0.4
0.2
1440
1080
720
360
1080
720
360
0.599
0.448
0.305
0.159
0.448
0.305
0.159
pull
pull
pull
pull
pull
pull
pull
Tugboats operate at 80% MCR only about 2% of the time underway. This is largely
due to the small size of the vessel which requires high power output only when
assisting larger vessels in maneuvering and mooring operations. This results in most
tugboats operating the propulsion engines of the tug at an output much less than the
MCR for 80%–90% of the time. Applying the above-mentioned procedure of sizing a
diesel engine to a tugboat in order to maintain normal loading within 80%–90% of
MCR creates a highly inefficient operating profile. The result is that most of the time
the vessel is operating in a region of high inefficiency. For the purposes of this case
study, a standard 8-h day was applied to the operating parameter percentages. Using the
data from Table 2, the time bar chart was superimposed on the engine power output bar
chart, as seen in Fig. 1.
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Power & Time vs. Tugboat Operating Modes
3
1600
1400
2.5
2
kW
1000
1.5
800
600
1
400
0.5
200
Time (hrs)
1200
Engine Output (kW)
Time (per day, hr)
0
0
Idle
80%
pull
60%
pull
40%
pull
20%
pull
60%
pull
40%
pull
20%
pull
Standby Transit Transit Assist
low
high
Assist
Assist
Assist
Barge
Mv
Barge
Mv
Barge
Mv
5
6
7
8
9
10
1
Transit Transit
2
3
4
Operating Mode
Fig. 1. Operating mode showing time allocations with coinciding power requirements
As seen above, for operational modes 4, 5, 8, and 9, a large amount of power is
required for a short period of time. Conversely, for operational modes 1, 2, 3, 7, and 10,
a much smaller amount of power is required for a significantly larger period of time.
Considering both situations, a power threshold can be determined. The power threshold
refers to the cut-off point where the vessel is operating at an abnormally low power
output for a significant amount of time. The power threshold derived from this analysis
is 360 kW. This means that modes that stay below 360 kW operate significantly
outside of the range of peak efficiency for the rated 1800 kW engine, resulting in a high
potential for fuel savings if alternative energy sources and power applications are used
for these modes. Operating Mode 6 is an outlier because it requires moderate power for
a moderate amount of time, approximately 518.4 kWh, with a peak power of 720 kW.
In the specific case of this operating profile, the tug has a rated output power of 360 kW
or less for 87% of the time underway.
3.2
Hybrid Propulsion
The sole focus of commercial enterprise in the maritime sector is centered on costsaving measures with the goal of increasing profits. This includes maximizing fuel
efficiency to decrease fuel costs, which account for a high percentage of the overall
operating costs for commercial vessels. For vessels that have large fluctuations between
high propulsion loads and low hotel loads, hybrid propulsion presents potential cost
savings. Electric motors offer clear advantages in terms of versatility and maneuverability, namely, being able to operate at a larger range of loads while maintaining
relatively high efficiency. While electric motors also tend to operate most efficiently at
high loads, the efficiency taper at lower loads is much more gradual when compared to
diesel engines (US Department of Energy 2014). This means the electric motors are
able to retain a higher efficiency over the same operating conditions compared to diesel
Marine Electrification is the Future: A Tugboat Case Study
873
engines. Hybrid applications that boast large fuel savings are being implemented in
various ways in industries that include ferry and tug vessels. One example of such
benefits can be seen at Derecktor Shipyards of Mamaroneck, NY. Derecktor Shipyards
has constructed a hybrid propulsion vessel with a 55% reduction in fuel usage by using
two BAE Systems AC traction motors. Taking a closer look at Fig. 1 above reveals that
electric propulsion from stored power in battery packs can be used to supplement the
diesel engine for power conditions at 360 kW or less. Applying this analysis, Fig. 2
displays which operating modes should be powered by electricity.
kW
Engine Output (kW)
1600
1400
1200
1000
800
600
400
200
0
1440
1080
1080
720
90
43.2
720
360
180
360
1.2
2.4
0.56
0.08
0.08
0.72
2.08
0.08
0.08
0.72
Idle
Transit
Transit
80% pull
60% pull
40% pull
20% pull
60% pull
40% pull
20% pull
Transit
high
Assist
Assist
Assist
Assist
Standby Transit low
Barge Mv Barge Mv Barge Mv
Time (hrs)
Fig. 2. Operating modes differentiated by diesel and electric power in proposed hybrid
propulsion system
The yellow-filled bars represent operating conditions to be powered by a fully
electric system. The blue bars represent the operating conditions where the diesel
engine will be turned on for high power output push-pull operations. Following this
proposed power profile, the tugboat will use approximately 0.7 tons less fuel per 8-h
working day when compared with a diesel-only vessel. Decreasing fuel usage by 0.7
tons per day equates to a 62% decrease in fuel consumption for this vessel. It should be
noted that these calculations do not include the added weight of the electric propulsion
system and storage batteries, which would require a capacity of just over 1320 kWh.
Calculating new ship-specific power requirements and hull changes in order to
implement hybrid technology are beyond the scope of this analysis. However, the
estimated fuel savings shows the potential for hybridized electric propulsion in the
tugboat industry and similar industries. Additionally, the 0.7 ton decrease in fuel
consumption, the tugboat would only require 0.43 tons of fuel for an operational 8-h
day, which would decrease the fuel storage tank capacity.
3.3
Battery Sizing
When designing a battery-electric or hybrid vessel, the primary limiting factor is the
space required for battery storage. Even with modern advancements in battery technology, the volume required to store the needed watt-hours (W-HR) of energy needed
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for propulsion eventually limits the range and cargo capacity of the vessel. Balancing
all three requires careful design of the battery storage areas.
Calculating the volume needed for battery storage first requires determining two
design parameters: (1) the intended voltage (V) for the battery system, and (2) the total
kilo-watt hours (kWh) needed for propulsion. With these two parameters determined,
Eq. (1) can be used to calculate the Whr required for the system.
Watt hours ¼ Volt Amp hours ¼ ðkWhÞ 1000 W
VA
kW
W
ð1Þ
With the required kWh for the system calculated, the volumetric energy density
(kWh/L) can be used to determine the Liters of volumetric space needed for batteries.
The gravimetric energy density, in kilowatt-hours per kilogram (kWh/kg) can also be
used to determine the mass of batteries needed for the system.
A predictive model was constructed to approximate the weight of battery packs per
kWh using the Tesla 5.3 kWh Battery Module as a standard due to the high energy
density of the battery. Figure 3 below shows the trend of the weight of the battery as
the kWh increases for larger applications, such as vessels. Included in Fig. 3 is the
calculated kWh for the tugboat with corresponding weight of 6,216 kg.
Battery Pack Weight Approximation (kg)
16,000
y = 2452.6x - 3190.8
14,000
12,000
9,415
Weight (kg)
10,000
6,216
8,000
4,708
6,000
4,000
2,000
471
25
(2,000)
Weight (kg)
100
1,000.0
1,320.5
2,000.0
Tesla 5.3
kWh Module
5.3
Small kWh
Medium
kWh
Plug-inHybrid Tug
Large kWh
25
471
4,708
6,216
9,415
Projected
Projected
Battery kWh
Weight (kg)
Linear (Weight (kg))
Fig. 3. Battery Pack Weight Approximation as kWh increases, based on Tesla 5.3 kWh Module
Having batteries on board a vessel that replace liquid fuel serves several advantages. As batteries are used for power, their mass effectively does not change, only
about 0.5 mg of mass for a 1.7 MW battery system. When petroleum is used, the vessel
Marine Electrification is the Future: A Tugboat Case Study
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becomes increasingly lighter, posing a ballast issue (Schurke 2021). As a result, batteries become solid ballast for the vessel, without the dangerous addition of the free
surface effect from liquid ballast or fuel tanks.
Once the volumetric and mass requirements for the batteries are determined, several
other factors must be accounted for. For example, batteries generate heat as they charge
and release energy, so a cooling system must be designed to account for this heat load.
Additionally, the heat load can require spacing batteries to allow space for the cooling
system, which results in increased volume and mass requirements for the overall
system. Fire suppression systems also account for additional space in the battery
storage area.
4 Inland Waterway Infrastructure, Charging Stations
4.1
Applicability
The benefits of hybridized technology for an inland waterway tugboat operating profile
are numerous, providing benefits to the vessel owner as well as the surrounding
environment. These solutions are undercut by waterway electric grid infrastructure,
which would take significant time and money to upgrade. Improving grid capacity for
highly trafficked ports, to include recreational marinas, will give consumers the ability
to explore plug-in hybrid or even fully electric propulsion options for vessels. These
options are appealing to sailors and commercial operators who operate for limited
hours per day, allowing for the time to recharge the battery pack(s) at night or during
periods of non-operation. Current electric vehicle charging stations can be referenced
when looking to install charging stations at marinas and commercial ports. Table 3
below depicts current electric vehicle charging stations with operating characteristics.
Table 3. Typical battery charging stations (Palconit et al. 2018)
Voltage (V) Current (A) Power (kW) Type
Level 1 110
16
1.9
AC
Level 2 208/240
32
19
AC
Level 3 480
400
240
DC
For recreational sailors, installing lower-rated charging stations, like Level 1 or
Level 2 chargers, would directly reduce the amount of fuel required at dockside
refueling stations. Less frequent fueling operations directly correlate to a decrease in
pollution incidents. For commercial operations that require significantly more power
and larger capacity battery packs, like tugboats, Level 3 charging stations should be
installed. If implemented, commercial enterprise and civilian sailors would have the
opportunity to choose hybrid or fully electric boating options, further reducing the
reliance on exclusively petroleum-based products.
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Standardization
Bringing electric propulsion solutions to the maritime industry provides regulatory
authorities and design engineers with an opportunity to learn from the previous
implementation in the automotive transportation industry. Standardizing a grid approach
is essential to streamline future upgrades to the system and accelerate widespread
installation. Currently, there are three types of electric vehicle DC fast charging connections: CHAdeMO (developed by the Tokyo Electric Power Company for DC
charging), SAE Combo (CCS), and Tesla Supercharger Plug. This is the result of
regulatory authority lagging behind technological advancement. Simply put, private
industry developed their own system and charger plugs, offering the public several
options. Standardization was later implemented for Level 1 and Level 2 charging stations but remains to be updated as Level 3 charging stations become more abundant. The
problem that this causes is inconvenience and inefficient charging station installment.
This means, depending on the vehicle a customer purchases, only certain charging
stations will be compatible. Learning from this, the marine industry has the opportunity
to standardize two plugs for recreational boaters: regular charging and DC fast charging,
resulting in base-line infrastructure widely available, regardless of manufacturer.
For commercial use, a higher rated standard should be developed based on the line
voltage from the grid, to scale charging times for significantly larger battery packs. In the
Port of Göteborg, medium voltage transformers provide 10 kV/6.6 kV 1250 kVA on
the quay (Ericsson and Fazlagic 2008). Commercial ports have the available grid support to cater to larger battery packs used for propulsion, and a standard ship connection
used for charging batteries, instead of supplying hotel loads, needs to be developed.
5 Solid-State Batteries
An in-depth discussion of the electrochemical properties of lithium-ion and solid-state
batteries is beyond the scope of this paper. However, a brief overview and various
benefits and drawbacks will be covered. Recent developments in solid-state lithium-ion
battery production yield optimistic futures for recreational and commercial transportation industries. Limitations with liquid electrolytes in current lithium-ion batteries
are extensive and have significant drawbacks in both performance and safety when
compared to solid-state batteries. Therefore, further research in solid-state batteries may
allow the maritime industry to decrease the added mass on a vessel when compared to
traditional lithium-ion batteries.
The physical orientation of solid-state batteries allows for the cells to be arranged in
series stacking and bipolar structures, thus allowing for less volume occupation on the
vessel. As the total displaced volume of the battery decreases, ceteris paribus, the
energy density increases. This is achieved by swapping the electrolyte material from an
organic liquid to a solid electrolyte. This transition boasts higher electron transfer rates
and further increases safety due to the inherently flammable nature of liquid organic
electrolytes. Further, solid-state batteries are able to fully cycle thousands of times
without losing capacity (Pistoia 2014).
Designing modular battery-pack systems in easily crane-accessible areas on the
vessel would allow the battery storage pack to be upgraded over time, simply by
Marine Electrification is the Future: A Tugboat Case Study
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swapping out the battery pack onto established battery mounts. Easily upgraded
propulsion systems are the future of the marine industry.
6 Regulatory Oversight
6.1
Overview
Rapid advancements in technology require regulatory agencies to maintain safety
compliance as a continuation of current standards, applying to shore-side infrastructure
and waterborne transport. Electric propulsion systems and shore-side charging systems
need to be designed and inspected to ensure tolerances for various load conditions that
may arise from atypical operations. For example, systems need to be tested to withstand
overloading conditions, under loading conditions, short circuit situations, and
mechanical deformation of the battery packs, to name a few. The United States Coast
Guard is working at the deck-plate level with manufacturers when constructing new
systems, as well as reviewing plans for future builds to ensure safety compliance. Both
levels of oversight are necessary to reduce the risk of failure at all system components.
6.2
Fire Prevention
Prevention of fire becomes a life or death scenario when applied to waterborne
transport. There are several difficulties that present themselves when extinguishing a
lithium-ion battery that will be covered in Sect. 6.3, but preventing fires in the first
place is a priority. Lithium-ion batteries are at risk of thermal runaways. Thermal
runaways occur when an exothermic reaction is caused by exposure to high temperatures (130 C–150 C) or when the battery is short-circuited. When this occurs,
temperatures rise and gasses build up, which create an environment prone to fire or
explosion. To prevent the occurrence of a fire or explosion, several safety measures
must be installed and regulated. These measures include preventing thermal runaway
using separators, preventing fire using flame retardant additives, and preventing the
buildup of gas and pressure by cell venting.
Separators are components within the structure of the battery made of a semiporous polymer in most cases. Placed in-between the positive and negative electrodes
inside the battery, the separator prevents direct contact between the electrodes, which
prevents an electrical short from occurring. Furthermore, as the temperature in the
battery increases during a thermal runaway, the polymer material approaches its
melting point, thus closing the pores and preventing the electrochemical reactions
caused by the pathway between the electrodes. When this occurs, it is called a separator
shutdown and is an inherently safe component of the battery structure.
Using flame retardants as an additive to the electrolyte or directly in the separator
makes the batteries much safer. As the temperature in the battery rises during a thermal
runaway, the electrolyte will not flash or combust when the flame retardant additive is
used.
Safety vents are installed to release gasses from the battery in the event of a
buildup. If the separator shutdown fails, thermal runaway will continue causing the
internal venting mechanism to activate. This mechanism vents the battery abruptly,
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purging the gas buildup and drastically reducing the pressure to prevent a rupture or
explosion. This will include toxic gas sensors and ventilation systems to remove toxic
gasses created by batteries while charging/discharging. Items such as ductwork for
ventilation and discharge piping and nozzles for the fire extinguishing system all must
be accounted for when sizing a battery room for a vessel (Kong et al. 2018).
6.3
Fire Suppression
Subsequent systems for new technology must also be installed, and further research
needs to be conducted to learn more about the thermal properties of lithium-ion batteries. For the safety of vessel operators, a fire detection and extinguishing system is
necessary. When lithium batteries catch fire, they cause fires that range in classification.
Additionally, thermal runaways make the extinguishing process slightly more complex.
Instead of simply putting out the flame, extensive cooling is necessary to prevent a reflash from occurring. Various agents can be used to extinguish lithium-ion batteries,
including dry chemical, carbon dioxide, water, and halons to name a few. However,
regulatory standards published by the Institute of Electrical and Electronics Engineers
(IEEE) only focus on abuse and threshold testing of the batteries. Published data
indicates that large-scale battery storage spaces require extended water hose stream
application in order to fully extinguish the fire (Long and Misera 2019). There is a need
to develop a system that adequately extinguishes lithium-ion batteries, cools the batteries sufficiently to prevent them from reigniting, and does not put the vessel in danger
in terms of stability. There is no specific standard for extinguishing lithium-ion batteries, which leaves a major gap in the regulatory realm of safety compliance.
7 Conclusions
Electricity provides an opportunity to create a maritime industry more resilient to future
energy changes. Rather than relying solely on petroleum-based energy, tapping into a
diverse energy grid to source power from the growing number of renewable resources
provides a flexible and secure maritime economy. There is an opportunity to start
implementing electric or hybrid propulsion with smaller vessels that operate for relatively short periods of time while standardizing practices like charging station plugs. In
addition to the energy diversification benefits, significant fuel savings are observed
when compared to traditional internal combustion engines. It is common for vessels
with large engines to operate under-loaded. These situations provide an opportunity to
implement electric propulsion. A case study was conducted for an inland waterway
tugboat with 10 distinct operating modes. The study yielded a 62% reduction in fuel
consumption with hybridized technology. Applying this technology to vessels with
similar operating modes has the potential to provide energy savings industry-wide.
Progressing the grid in a more sustainable direction will take significant time and
resources. As new battery technologies and applications continue to enter the maritime
industry, governments need to be at the forefront of research and development in order
to enforce new safety regulations that include fire prevention and suppression of
lithium-ion battery fires. In order to get there, maritime authorities need to incentivize
Marine Electrification is the Future: A Tugboat Case Study
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the installation of charging stations while maintaining regulatory oversight on
emerging technologies to ensure safety compliance.
Acknowledgements. I would like to express my deepest appreciation to Lieutenant Commander
Jon Benvenuto (USCG), PE, PMP, who offered steadfast mentorship and encouragement
throughout the research process. I would also like to acknowledge the assistance of Ensign Kevin
Reed (USN), Mercedes Walter, and John Hayton for providing thorough guidance and advice
during the drafting of this paper.
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