4.1. Data Extraction
The vessels designed or modified for electrification to achieve green transformation are presented in Table 2
]. The name of the ship in Column 2 of Table 2
is followed by the country name in Column 3. The power trains (Column 4) are either electric (purely battery operated) or hybrid (batteries along with a diesel engine or fuel cell). The battery capacity (in kWh) and type are provided in Column 5 and Column 6, respectively. Similarly, the year of manufacturing and the name of the company are provided in Column 7 and Column 8, respectively. Finally, the parameters, such as passengers, car carrying capacity, cruising speed, and size (length) of the vessels are provided in Columns 9–12, respectively.
Vessel study for battery technology towards electrification.
Vessel study for battery technology towards electrification.
|Ref. No.||Name||Country||Power Train||Battery (kWh)||Battery Type||Year||Company||Passengers||Cars||Speed (knots)||Length (m)|
|||Nemo H2||Nether-lands||Hybrid||70||-||2009||Govt. and Industry||87||-||9||22|
|||MV Hallaig||Scotland||Hybrid||700||Li-ion||2012||CalMac Ferries Ltd||150||23||9||43|
|||MV Lochinvar||Scotland||Hybrid||700||Li-ion||2013||CalMac Ferries Ltd||150||23||9||43|
|||MV Island Clipper||Norway||Hybrid||875||Li-ion||2015||Inland Offshore Management AS||56||-||15||97|
|||BB Green||Nether-lands||Hybrid||200||Li-ion||2015||Partly funded by an EU dev. project||100||-||30||22|
|||Vision of the Fjords||Norway||Hybrid||600||Li-ion||2016||The Fjords||399||-||19.5||40|
|||MV Catriona||Scotland||Hybrid||700||Li-ion||2016||CalMac Ferries Ltd||150||23||9||43|
|||OV Bokfjord||Denmark||Hybrid||850||Li-ion||2016||Hvide Sande Shipyard||16||-||13.5||44|
|||Aditya||India||Electric||50||Li-ion||2016||Kerala State Water Transport Dept.||75||-||7.5||21|
|||MF Tycho Brahe||Denmark||Electric||4100||Li-ion||2017||Scandlines||1250||240||14.5||111|
|||Zhongtiandianyun 001||China||Electric||2400||Li-ion||2017||Guangzhou Shipyard International||-||-||7||70|
|||Future of the Fjords||Norway||Electric||1800||Li-ion||2018||The Fjords||400||-||16||43|
|||Enhydra||USA||Hybrid||160||Li-ion||2018||Red & White Fleet||600||-||13||39|
|||MV Waterman||USA||Hybrid||80||Li-ion||2019||All America Marine, Inc.||150||-||15||21|
|||MS Color Hybrid||Norway||Hybrid||5000||Li-ion||2019||Color Line||2000||-||17||160|
The data in Table 2
is organized in chronological order (year of manufacture). In this context, Zemships from Germany [40
] designed a hybrid vessel, named the FSC Alsterwasser, in 2008 with a battery capacity of 200 kWh. The passenger capacity is 100 and it can sail with a speed of 8 knots. The most recent entries (2019) in Table 2
are Ellen from Denmark [43
], MV Waterman from the USA [60
], and MS Color Hybrid from Norway [63
]. The passenger capacities in these vessels are 200, 150, and 2000, respectively. Similarly, the battery capacity in these vessels are 4300, 80, and 5000 kWh, respectively. The differences in battery capacities is due to the power train and size of the ships. For example, the battery capacity in Ellen [43
] is 4300 because its power train is pure electric, while the power train of MV Waterman [60
] is hybrid and, therefore, the battery requirement is 80 kWh. Furthermore, the higher battery capacity requirement (5000 kWh) of the MS Color Hybrid ferry [63
] is due to its passenger carrying capacity (2000 persons).
While Table 2
provides the data, extracted directly from the websites of manufacturers, Table 3
summarizes some important R&D projects [32
] related to ferry electrification. The information in Table 3
is organized in a fashion similar to Table 2
, except that the year of manufacture in Column 7 of Table 2
is replaced with the year of publication in Column 7 of Table 3
Case studies through research and publications.
Case studies through research and publications.
|Ref. No.||Name||Country||Power Train||Battery (kWh)||Battery Type||Year||Project||Passengers||Cars||Speed (knots)||Length (m)|
|||Typical Shuttle||Italy||Hybrid||500, 300, 160||Li-ion||2015||R&D||48||-||13||24|
4.2. Data Synthesis
Based on the data presented in Table 2
and Table 3
, this section interprets/synthesizes the data to reveal some meaningful information. For example, Figure 4
shows the countrywide electrification of ships (both pure electric and hybrid) in the last decade. In this context, the data can be classified into three categories. The first category consists of three countries: Scotland, Denmark, and Norway. The countries in the first category have electrified three, five, and seven ships, respectively, and play a leading role in this technology. The second category consists of Germany, the Netherlands, Sweden, and the USA, in that each country in this category has electrified two ships. Finally, the third category includes China, Finland, and India, who have each electrified one ship in the last decade. It is important to note that the countrywide electrification of ships in Figure 4
is purely based on the data presented in Table 2
. The data in Table 3
is mainly related to some R&D activities and are, therefore, not included in Figure 4
In addition to countrywide electrification, companywide electrification of vessels is equally important and is shown in Figure 5
, which depicts the companywide electrification for the period 2008–2019. It can be seen that Zemships (Germany) [40
] started the process in 2008, followed by the Govt. and Industrial project (Netherlands) [41
] and Eidesvik (Norway) [42
] in 2009. After a gap of two years, CalMac Ferries Ltd. (Scotland) built two ships [46
] in 2012 and 2013. Scandlines (Denmark) electrified a ship [49
] in 2013 and two ships [50
] in 2014. Two more companies, Ballerina [52
] and Echandia Marine [53
] (both from Sweden) built ships in 2014. The two Norwegian companies, Norled [54
] and Inland Offshore Management AS [55
], as well as a project partially funded by an EU development project [61
] in the Netherlands, electrified ships in 2015. Four ships were electrified in 2016 by The Fjords (Norway) [45
], CalMac Ferries Ltd. (Scotland) [48
], Hvide Sande Shipyard (Denmark) [56
], and Kerala State Water Transport Department (India) [62
]. In 2017, four vessels were electrified by Scandlines (Denmark) [33
], Finferries (Finland) [34
], Eidesvik (Norway) [57
], and Guangzhou Shipyard International (China) [58
]. The Fjords (Norway) [44
] and Red and White Fleet (USA) [59
] electrified two ships in 2018. Three ships were electrified in 2019 by the EU H2020 Project (Denmark) [43
], All American Marine, Inc. (USA) [60
], and Color Line (Norway) [63
While Figure 4
and Figure 5
provide a classification of vessels according to different countries and companies, respectively, a classification of vessels according to battery capacity and ship size (length) is provided in Figure 6
. It has been shown in Figure 6
that the ships designed in the last decade can be classified into pure electric (31%) and hybrid (69%). The figure has a dual scale; the battery capacity range is shown on the left hand side in kWh, while the vessel size is shown on the right hand side in meters.
The battery capacity used in pure electric vessels is in the range of 50–500 kWh, with a median value of 140 kWh, while, in hybrid ships, the range is 500–5000 kWh, with a median of 1000 kWh. From the analysis, it is clear that hybrid technology (used in 69% of the vessels) has an almost 10 times larger battery capacity compared to the pure electric vessels. The pure electric vessel length is in the range of 21–39 m, with a median at 22 m, while the hybrid ship lengths are in the range of 40–160 m, with a median of 84.5 m. The difference between lengths is at least twice at minimum range, while this difference in size becomes four times at maximum values. Finally, the green dotted line shows the trend of battery capacity in kWh for different electric and hybrid vessels, and the red dotted line shows the trend of vessel length for various electric and hybrid vessels.
Similar to Figure 6
, Figure 7
classifies the pure electric and hybrid technology on the basis of three parameters: (1) passengers capacity, (2) car carrying capacity, and (3) the maximum speed of the vessel. The figure has a dual scale; the passenger and car capacity are shown on the left side of the graph, while the vessel speed in knots is shown on the right side of the graph. It is obvious from Figure 7
that the passenger capacity of pure electric vessels is in the range of 75–1250, with a median value of 200 persons. It is important to note that only some of the vessels (and not all the vessels) can also carry up to 240 cars. On the other hand, the hybrid vessels can transport 16–2000 passengers with a median value of 150 personnel, but in addition they can also carry 23–364 cars depending upon their size. The speed of pure electric vessels is in the range of 7–21 knots, with a median value of 9.5 knots, while hybrid ships use 8–30 knots with a median value of 14.25 knots. From the analysis, it can be seen that the speed of hybrid vessels is almost 1.5 times greater than that of pure electric vessels. Finally, the blue dotted line shows the trend of passenger capacity for several electric and hybrid vessels, and the red dotted line shows the trend of the maximum speed of various electric and hybrid vessels. The trend for car carrying capacity is not shown in Figure 7
because not all the vessels have this facility.
The aforementioned Figure 4
, Figure 5
, Figure 6
and Figure 7
have portrayed some valuable information related to green transformation in the maritime sector. In addition to previously discussed parameters, the information about the application of a particular vessel in the last ten years may provide an overall idea about their usage. Consequently, Figure 8
provides the distribution of vessels according to their use.
It can be observed from Figure 8
that the usage of vessels in the context of green transformation can be distributed into three categories: (1) Transportation, (2) Tourism, and (3) Other. The transportation category is related to the movement of passengers from one place to another for their daily routines, e.g., work, and has the widest use (65% of the total vessels) [63
]. In addition to the transportation of passengers, another major use of vessels is in the tourism sector. It has been found that 23% of the total vessels in the last ten years (according to Table 2
and Table 3
) have been particularly designed for tourism [43
]. Finally, the remaining 12% of vessels are used for miscellaneous applications such as a multi-purpose use or the offshore supply of oil and gas [42
4.3. Energy Storage System (ESS): Batteries
and Section 4.2
have summarized various parameters of electric/hybrid vessels for green transformation. However, the most critical parameter in electric/hybrid vessels is the energy storage system. Therefore, this section highlights some important issues related to the most frequently used battery technology. It is important to note that this section is not going to target the leading manufacturers of energy storage systems in electric/hybrid vessels, as this list can be seen in [73
]. Similarly, the cost analysis of various products from the leading manufacturers is presented in [74
]. In addition to the list of manufacturers and cost analysis, the life cycle analysis of frequently used batteries in the context of electric/hybrid vessels has already been discussed in [75
]. Readers are requested to please consult references [73
] for more details on these issues. Consequently, this section discusses various configurations of energy storage systems along with a discussion on frequently used Li-ion batteries.
Traditionally, fossil fuels are used in ferries to operate the main engine for propulsion and to provide electricity for appliances. Various efforts have been made for a green transformation from fossil fuel to battery operation to reduce CO2 emissions and noise level, especially in highly populated areas. From a propulsion point of view, battery operation can be divided into two categories/configurations.
In the first case, fully electric vessels use large battery banks to drive an electric motor; however, in these cases, regular charging of the batteries is a challenge. In addition, the continuous use of batteries requires a suitable cooling system for satisfactory performance and battery life. Due to limited battery capacity and high energy requirements, this system is used in vessels used for short distances and limited time operations. The battery bank of the vessel is charged from the shore grid; however, a small generator is available to charge batteries in emergency situations.
In the second option, i.e., hybrid propulsion systems, a typical diesel or gasoline engine along with the battery bank is used to operate an electric motor. This system allows the vessel to travel longer distances. The batteries are used at lower speed, especially at the time of docking to ensure zero-emissions. The electrification of a vessel depends highly upon the battery system, which includes the dimension, weight, recharging time, lifetime, cost, the cooling system, and recycling.
From the study of state-of-the-art commercial vessels in Table 2
and the case studies in Table 3
, we found that battery technology has moved from lead-acid to Li-ion batteries [28
]. One of the major reasons for this is the cost, which has declined from USD 917 to USD 135 in the last decade and is expected to be reduced to USD 100 in 2021, as shown in Figure 9
Due to cost-effectiveness, Li-ion batteries are widely used in the energy storage systems of electric and hybrid ferries. Although the Li-ion batteries are cost effective and provide high energy, their life degrades with charging and discharging cycles [28
]. Usually, the lifetime of the batteries is calculated in terms of number of charging and discharging cycles rather than calendar time. Typically, the battery life is considered to end when battery performance is reduced by 70–80% of the early capacity [76
]; exact values can be determined from the manufacturer’s datasheet. The expected life of a Li-ion battery is 7–10 years, which depends upon charging, discharging cycles, cooling, and physical degradation [47
]. Compared to lead acid batteries that have low cost but heavy weight, Li-ion batteries are a bit costly but are light enough to be used in electric ferries [28
]. In addition, Li-ion batteries can be charged at a fast rate and have good safety specifications [48
Performance and life of the batteries depends upon operating temperature; therefore, proper cooling is required for battery life as well as for safety. Popular methods include (1) air cooling, (2) liquid cooling (direct and indirect), and (3) fin cooling. Each has trade-offs that include cost, complexity, and power requirements. From an implementation point of view, air cooling is the most inexpensive and simplest technique and depletes the most parasitic power. Liquid cooling is more effective but is also more complex and costly; however, maximum temperature difference can be achieved using indirect liquid cooling. Finally, fins are used for heat removal with uniformity, but extra weight is added in the system compared with the above two methods [49
]. The heat dissipated by the battery requires suitable ventilation, otherwise the battery system gets overheated, which not only provides poor performance but also becomes a safety concern.