Analysis of the Parameters of an Ecological Power Supply Wire System for Moving and Stabilising the Position of a Floating Dock

Abstract

This research study aims to develop a system which ensures the mobility of a floating dock and its stability in position during docking operations. The dock is designed for operation in a river canal. In order to dock a ship, it is moved away from the quay over a dock trench. Initial requirements and design criteria for the system were determined. The most important of them include docking in the maximum weather conditions, corresponding to a wind speed of 5° Beaufort (5°B), and a zero-emission target for the power supply system (use of a renewable energy source). A wire and winch system was designed to move the dock and stabilise it in position during docking operations. The system comprises mooring wires which are tied to bollards on both quays, and wire winches mounted on both sides of the dock. The wire winches are hydraulically driven, and the hydraulic pumps, run by electric motors, are powered with batteries charged using photovoltaic panels. Statistical environmental parameters (wind, river current) were analysed and the probability of certain mooring wire loads and the corresponding wire winch power output were quantified. Based on these calculations, the power of photovoltaic panels and capacity of the batteries required to power the dock moving system were determined. This paper discusses the system design as well as the results of trials.

1. Introduction

One of the frequently repeated operations over a ship’s life span is docking. During docking, ships undergo maintenance, such as hull cleaning, painting, overhauls, and repairs. Docking is performed in repair shipyards, typically using a floating dock. The docking of a ship in a floating dock is usually performed at the quay. The dock submerges to a depth which allows the ship to enter. Once the ship is in the dock, the dock emerges and picks up the ship. The ship leaves the dock in the reverse sequence. The depth of water at the repair quay must be sufficient for the dock to submerge to a certain depth as required by the size of the dock and the size of the docked ship.

A floating dock (Figure 1) of a size suitable for the docking of ships up to 6 m has been built in the Pomerania Shipyard in Szczecin (Poland).

The dimensions of the dock and the maximum size of vessels which can be docked, as well as the dimensions of the Parnicki Canal, are provided in [1].

According to [1], the Parnicki Canal can be entered by ships drawing up to 6.0 m. However, the depth of water at the repair quay is insufficient for the dock to submerge for a docking operation. In order to perform the docking operation at the quay, the canal would need to be deepened to a minimum depth of 11 m over a surface area larger than the bottom of the dock. Although technically feasible, the hydro-engineering works would require a substantial financial investment. The deepened canal would require a new quay of 11 m in depth. Alternatively, and at a much smaller cost, a dock trench has been built along the axis of the Parnicki Canal. The location of the floating dock on the Parnicki Canal and the location and dimensions of the dock trench are specified in [1].

The process of docking a ship in the dock trench is shown in

Table 1. Docking of a ship in the dock trench at the Parnicki Canal.

	Stage of Docking
	The dock is moved away from the repair quay over the dock trench. (dock’s draft T = 2 m)
	The dock is over the dock trench. (dock’s draft T = 2 m)
	The dock submerges and the ship is pulled into the dock. (dock’s draft T = 10 m)
	The dock emerges, picking up the ship. (dock’s draft T = 10 m)
	The dock with the ship onboard is moved back to the repair quay. (dock’s draft T = 2 m)
	The dock with the ship is at the repair quay. (dock’s draft T = 2 m)

.

The dock can be moved and stabilised in position over the dock trench with the use of either of the following:

• Port tugs;
• An alternative system, with no need to use port tugs.

Powered by combustion engines, port tugs are costly to operate, consume large amounts of fuel, and generate toxic emissions.

The operation time of tug boats in hours, number of tug boats, and fuel consumption during the operations of moving the dock away from the quay, docking, and pulling the dock back to the quay are shown in

Table 2. Estimated operation time of tug boats [h] and fuel consumption per one docking operation.

No.	Operation	Duration [h]	Number of Tugs	Fuel [L]
1.	Moving the dock over the dock trench	4	2	4000 *
2.	Submerging of the dock to pick up the ship	4	2	4000
3.	Picking up of the ship	2	2	2000
4.	Emerging of the dock together with the ship	3	2	3000
°.	Moving the dock back to the quay	4	2	4000
	∑	17	-	17,000

* Fuel consumption for one tug boat: 500 L/h.

.

Operations 1 and 5 include the time necessary for the tug boats to reach the dock and return to the Pomerania Shipyard.

A total of 17,000 L of fuel would be used in the operation, generating high emissions of fumes, including CO₂. Once the repair of the ship in the dock is completed, the tug boats must be used again to move the dock away from the quay and pull the ship out of the dock; i.e., the operation must be repeated, in a reverse sequence.

At least 16 ships are expected to be repaired in the floating dock each year.

The total yearly consumption of fuel would be as follows:

$$G_P=17.000·2·16=\mathrm{544,000} \mathrm{L}/\mathrm{y}\mathrm{e}\mathrm{a}\mathrm{r}=490\ast \mathrm{t}/\mathrm{y}\mathrm{e}\mathrm{a}\mathrm{r}$$

* Average density of light marine diesel oil MDO ρ = 0.9 t/m³.

Based on data on the combustion engines installed in the tug boats [2,3], emissions of fumes and their components (NOx, CO, CO₂, HC) were estimated. The estimations are shown in

Table 3. Estimated yearly emissions of fumes from tug boats used in ship docking.

	Unit	Value
Fuel consumption	t/year	490
NOx emissions	t/year	100
CO emissions	t/year	30
CO2 emissions	t/year	8640
HC emissions	t/year	10

.

The data shown in Table 3 suggest that tug boats used to move the dock would generate extremely high yearly emissions of fumes, and the operation would have a negative environmental impact.

2. Objective and Scope of Study

The objective of this study is to develop an innovative, eco-friendly system to ensure mobility and stability of docks during docking operations (shown schematically in Table 1), powered by renewable energy.

In order to avoid generation of fumes during the docking of a ship (see Table 3), the designed system must be able to move the dock away from the quay and over the dock trench, and stabilise the dock while the ship is pulled into and out of the dock, without the use of tug boats. For this purpose, a research and development study [4] has been carried out with a view to

• analyse the feasibility of building a dock moving system;
• specify optimal parameters of an environmentally friendly power supply for the dock moving system.

The requirements of modern design extend beyond the conventional determination of the structure and strength parameters and include the development of suitable ecological power sources. A newly designed system must meet both technical/technological and environmental criteria and be possibly environmentally neutral.

An in-depth analysis of the literature on the subject and the sources available on the Internet shows that research into floating docks is focused mainly on the design, structure, strength, and safety of docking operations.

,Various types of floating docks and their applications, structure, and design principles are discussed in [5,6,7]. Typical geometrical parameters of floating docks and the relations among them, as well as the impact of the maritime architecture on the design of floating docks, are analysed in [6]. The sources referred to above propose methods of calculation of the stress, strength, and stability of the dock, and discuss ballast systems. Certain floating dock design procedures, aimed to ensure reliability and safety, are discussed in [7,8,9]. Two eco-friendly designs of a floating dock are discussed in [10]; however, their eco-friendliness is considered only with reference to repairs of the ship’s hull.

Another important research problem is the dock’s stability and strength. Analyses of stability across the stages of submerging and emerging of the dock are discussed in [11,12,13]. Results of strength analyses taking into consideration operational conditions (the impact of wave motions), and practical applications of the analyses in the design process, are discussed in [6,14,15,16].

A dynamic analysis of a floating dock in random conditions, included in [17], is aimed to minimise accidents, and has been used to propose corresponding safety measures. For example, in [18], the boundary operational conditions (wave height) ensuring the required safety level were determined by the method of finite elements.

The authors of [19] have examined safety during docking operations and conducted a cause and effect analysis on a sample of real-life accidents.

Many publications discuss safety, strength, stability, and environmental protection during the pulling of ships into docks. These include textbooks [20], as well as guidebooks and scientific papers [21,22,23,24].

The above analysis of the literature shows that no methods or design solutions have been developed for a system to move and stabilise a floating dock in position. The concept of moving the dock away from the repair quay over a dock trench and pulling the ship into the dock has not yet been examined, and no solution has been created to power such a system using an environmentally friendly energy source.

In view of the above, this research into a system of moving and stabilising the dock in position (MSPD) over a dock trench built in the axis of a river canal, powered by renewable energy, is fully innovative and addresses the need for environmentally friendly solutions.

3. Design Criteria for the System Moving and Stabilising the Dock in Position and External Forces Acting on It

In order to solve the main research problem, i.e., develop a design solution for the system moving and stabilising the floating dock in position, it is necessary to define the following:

• Requirements for a successful docking operation and the operation of the system;
• Permissible weather conditions at which a docking operation can be performed;
• Design criteria for the system moving and stabilising the dock in position.

The design requirements and criteria for the development of the system moving and stabilising the dock in position (MSDP system) are specified in [1]. This publication also includes a design scheme, according to the adopted criteria.

Once the above is achieved, the following must occur:

• The system must be designed;
• The designed system must be checked for meeting the design requirements and criteria;
• The environmental impact of the system must be examined.

The design must provide for the use of a renewable energy source.

A detailed description of the process of designing a system for moving and stabilising a dock in position during the docking operation is provided in [1]. Analyses of various concepts of the system and their advantages and disadvantages are included in [4]. Based on an appraisal of the proposed systems, two of the concepts have been found to meet the adopted criteria. Since the dock must be equipped with machinery to pull the ship into the dock, a wire and winch system has been selected for this purpose. Its cost is lower than that of an alternative system which also meets the specified requirements.

The technical and operational parameters of the system have been specified based on the requirements and an analysis of the occurrence of certain hydrographic and meteorological conditions in the Port of Szczecin.

An integral part of the system moving and stabilising the dock in position is a power supply system using renewable energy. The parameters of the power supply system must be sufficient for the dock to be moved in various seasons of the year. A block diagram of how to achieve this objective is shown in Figure 2.

The load on the dock (empty or with a ship) is exerted by the following external forces:

• The wind force R_Ax, R_Ay, M_Az (components of the resultant wind pressure force and wind moment, whose directions depend on the wind direction β_A relative to the dock and the wind speed V_A);
• The river current R_Cx (depending on its speed V_C along the canal axis);
• Wave motions (considering the very small waves occurring on the Parnicki Canal, this has been omitted);
• The drag of the dock while being moved away from the repair quay over the dock trench R_Dy (depending on the transverse speed of the dock V_y; its direction is opposite to the direction of speed);
• The acting force of the ship being pulled into the dock R_DS.

The external forces working on the dock with a ship onboard, which have been taken into consideration, are defined and shown in Figure 3.

Depending on the stage of docking, the direction of speed V_y will vary; it will converge with the Y-axis when moving the dock away from the quay to the dock trench, or diverge from the Y-axis when moving the dock to the quay.

All the external forces acting on the dock will exert loads on the MSDP system.

Analyses of the MSDP system were performed for two extreme positions of the dock:

• Elevated, with a ship;
• Submerged, with a ship.

All forces exerting load on the dock and the MSDP system have been determined for two extreme positions of the dock. Calculations of the external forces taking into consideration the safety factor have served as a basis for the development the optimal design solution for the MSDP system and its technical and operational parameters.

The equations used to calculate the forces acting on the dock (and the ship in the dock) and their values are provided in [1].

The measured average current speed V_c = 0.5 knots (0.26 m/s) has been adopted for the calculation of the impact of the river current on the dock and the MSDP system [18]. The distribution of the underwater transverse surface of the dock has been calculated on the basis of the dock design documentation [25].

The impact of wind force on the dock and the MSDP system has been calculated using historical data on wind speed and direction in the analysed area (in the Port of Szczecin) [17,18,19]. It was established on the basis of the historical data that the probability of a certain wind direction is highly variable.

Table 4. Wind frequency, broken down by force [°B] and direction, for the period from 1 January 2004 to 31 December 2004 [27].

Wind Direction	Frequency of Wind Direction [%]	Frequency [%] of Wind Force [°B]
		1°B	2°B	3°B	4°B	5°B
N	7.38	14.81	59.26	25.93	0.00	0.00
NE	6.01	40.91	31.82	27.27	0.00	0.00
E	14.21	13.46	36.54	26.92	19.23	3.85
SE	3.55	0.00	38.46	23.08	23.08	15.38
S	15.85	1.72	41.38	37.93	17.24	1.72
SW	1.09	0.00	50.00	25.00	25.00	0.00
W	40.98	7.33	58.67	24.67	7.33	2.00
NW	9.02	9.09	39.40	27.27	15.15	9.09
VAR	1.91	42.86	42.86	14.29	0.00	0.00

shows the results of wind frequency measurements, broken down by force (in °B) and direction [26,27,28].

Based on the conducted computational analyses, it was found that the strongest external force acting on the dock is the wind force. Since the probabilities of certain wind speeds and geographical directions are highly variable (Table 4), the loads acting on the dock will also be variable throughout the year.

The impact of wind is the strongest when the wind acts on the side (the largest surface) of the dock, or is oblique relative to the centre line of the dock (Figure 3). The geographical coordinates of the repair quay (dock basin) are as follows: latitude 53°24′ N, longitude 14°60′ E, geographical direction 27°.

The statistical data (Table 4) show that wind directions NE and SW are lateral relative to the dock. The probability of a NE wind is very small, and that of a SW wind (from the repair quay) is close to zero. A W wind, oblique relative to the dock, may have a strong effect on the dock.

It can be seen in Table 4 that the frequency of wind from certain directions is varied. The calculated forces acting on the dock with a ship will have the same frequency of occurrence. Cumulative distribution functions of wind frequency (Figure 4) for the most unfavourable wind directions acting on the dock were determined for the data included in Table 4.

The probabilities of wind directions during a year are as follows:

W→41%

E→14.2%

NE→6%

It results from the analyses (distribution functions shown in Figure 4) that the probability of a wind force higher than 3°B for the most unfavourable wind directions relative to the dock is very small.

Having conducted an analysis of the port regulations concerning ship docking operations and taking into consideration all the design criteria and assumptions for the MSDP system, it was decided that wind forces acting on the dock would be calculated for the following:

• The average wind speed corresponding to a wind force of 5°B;
• Any direction (angle β_A) of wind relative to the dock.

Detailed results of calculations of wind forces acting on a dock are included in [1,4].

Figure 5 shows the impact of wind R_Ay on the side of an elevated dock with a ship, depending on the wind force [°B] and direction relative to the dock (angle β_A, Figure 3).

Table 5. Total maximum external forces acting on the dock with a ship.

Dock’s Draft T [m]	Wind Force °B	Wind Speed VA [m/s]	Rx [kN] (βA = 30°)	Ry [kN] (βA = 90°)	Mz [kNm] (βA = 45°)
2	2	2.37	3.24	5.93	−110.0
	3	4.31	5.87	19.62	−395.0
	4	6.67	11.12	46.98	−905.0
	5	9.33	19.76	91.92	−1740.0

lists the total, maximum external forces acting on the dock with a ship and the MSPD system for various wind speeds (°B) and draft T = 2 m (when the wind impact is the strongest), taking into consideration forces from the river current, the drag of the dock, and the drag of the pulled-in ship (Figure 3). The MSDP system was designed on the basis of these values.

Since wind speed and direction are random variables (Table 4 and Figure 4), the resulting impact of wind will be random and have a variable frequency of occurrence during a year. The frequency of wind impact on the dock will correspond to the frequency of a certain wind speed (°B) and direction.

4. Design of the Autonomous System for Moving and Stabilising the Dock in Position

Several design concepts (each of them in several variants) of the dock moving system have been developed as a result of the conducted analyses and research work, described in [1,4]. Two of them have been found to meet the adopted criteria. The dock has been designed to be equipped with a wire and winch system.

The wire and winch system utilises four wire winches installed on two towers of the dock, one at the bow, and one at the stern (Figure 6).

The winches move the dock and stabilise it in position during the docking operation. Additionally, two auxiliary winches are mounted on the port side of the dock, which support the pulling of the dock to the repair quay. The mooring wires on the port side of the dock are tied to bollards at the repair quay, while those on the starboard side of the dock are tied to the opposite quay. The wires on the starboard side of the dock must be carried to the other bank of the canal. Once the ship is docked and the dock pulled to the repair quay, they must be released from the bollards at the opposite quay and wound on the drums of the winches which move the dock.

Arrangement of Mooring Wires in the Wire and Winch System

Depending on the position of the dock relative to the repair quay, active lengths of wires will vary as the wires are wound on or out of the winch drums. In this way, the dock is moved (pulled away from or towards the repair quay). The process in shown in Figure 7 and Figure 8.

Figure 9 shows the distribution of forces (external and in the wires) acting on the dock equipped with a 4-wire system with winches.

The total external forces R_x, R_y and moment M_z acting on the dock are represented by the following equations:

$$R_x=\mathrm{c}\mathrm{o}\mathrm{s}\gamma \left(T_1+T_4-T_2-T_3\right),$$

$$R_y=\mathrm{s}\mathrm{i}\mathrm{n}\gamma \left(T_1+T_2-T_3-T_4\right),$$

(1)

$$M_z=\mathrm{s}\mathrm{i}\mathrm{n}\gamma \left[l_x\left(T_1-T_2+T_3-T_4\right)\right]-\mathrm{c}\mathrm{o}\mathrm{s}\gamma \left[l_y\left(T_1-T_2+T_3-T_4\right)\right]$$

The system is statically indeterminate. This means that in order to determine the forces in the wires T₁, T₂, T₃, T₄, the value of one of them must be predefined. For the purpose of this analysis, the value of force T₃ was predefined and the other wire forces were worked out from the system of Equation (1) for various predetermined external loads (R_x, R_y, M_z), as shown in

Table 6. Total maximum external forces acting on the dock with a ship for wind speed 5°B.

Dock’s Draft T [m]	Wind Direction Relative to the Dock βA	Rx [kN]	Ry [kN]	Mz [kNm]
2	0°	17.08	−0.95	0.0
	30°	19.76	48.29	−944.31
	60°	13.72	80.92	−944.98
	90°	2.66	91.92	−698.67
	120°	−9.49	79.46	−386.75
	150°	−18.81	45.39	−177.42
	180°	−21.59	−5.31	22.16

.

Selected calculated forces in the wires of the dock moving and stabilising system, for various wind speeds (°B) and directions (β_A) relative to the dock, are shown in Figure 10.

Dedicated wire winches were designed specifically for the dock, for the maximum external forces (wind speed of 5°B, Table 6) acting on the dock with the ship, to move it away from the quay and stabilise it in position (Figure 11), and to pull it back to the quay (Figure 12). The arrangement of the winches is shown in Figure 6, and their technical and operating parameters are listed in

Table 7. Technical and operational parameters of the wire and winch system for moving the dock.

Parameters of Winches Moving and Stabilising the Dock	Unit of Measurement	Value
Maximum calculated stress in the wire	kN	80
Diameter of the steel wire (safety factor 5)	mm	20
Wire strength (1960 N/mm2)	kN	400
Diameter of the winch drum	Mm	630
Length of the winch drum	Mm	366
Total length of the wire:
on the winch on the starboard side	m	120
on the winch on the port side	m	90
Diameter of the winch flange	Mm	400
Torque for the upper layer	kNm	28
Rated power of one winch	kW	10
Weight of one winch with the wire	Kg	~4500
Parameters of Winches Pulling the Dock to the Repair Quay	Unit of Measurement	Value
Diameter of the steel wire (safety factor 3)	Mm	11
Wire strength (2160 N/mm2)	kN	120
Diameter of the winch drum	Mm	310
Diameter of the winch flange	Mm	420
Length of the winch drum	Mm	138
Total lengths of wires	m	50
Winch power output	kN	37 ÷ 41
Torque for the upper layer	kNm	83
Rated power of 1 winch	kW	1.5
Weight of one winch with the wire	kg	~400

.

The wire winches moving and stabilising the dock are controlled from the control panels located at the winches.

5. Environmentally Friendly Power Supply System for a Hydraulically Driven Winch

5.1. The Concept of an Environmentally Friendly Power Supply System for the Dock Moving and Stabilising System

The dock moving and stabilising system consists of four main and two auxiliary wire winches (Figure 6). The rated power output of the winches is shown in Table 7.

During the moving of the dock away from the repair quay, once the wires are tied on bollards at the opposite quay (Figure 7), the winches mounted on the starboard side of the dock start winding up the wires. The real power output of a winch depends on weather conditions and, at a wind force of 5°B, its maximum value is 8 kW (in moderate weather conditions, the real power output of a winch is much smaller). Other winches, mounted on the port side of the dock, wind out the wires, and their real power output is equivalent to ca. 10% of the rated power. When the dock is moved away from the quay and during the docking operation, the winches keep the wires taut and their brakes are activated (Figure 8). Once the ship is pulled into the dock, the winches on the starboard side start winding out the wires, and those on the port side wind up the wires and pull the dock towards the quay (considering the arrangement, the auxiliary winches mostly pull the dock to the quay).

The design solution for the system of moving a floating dock and stabilising it in position (the main research problem) is accompanied by the concept of an environmentally friendly power supply for the system. The authors propose to power the hydraulically driven MSDP system with energy generated in photovoltaic panels and stored in batteries.

The Pomerania Shipyard expects to use the floating dock to carry out ca. 16 docking operations in a year. The cycle of moving the dock away from the repair quay, pulling the ship into the dock, and moving the dock back to the quay lasts ca. 35 min. On the basis of the information above, the demand for electricity and the capacity of the batteries required to power the hydraulically driven system were determined. The batteries will be charged in periods between the docking operations, i.e., on average, for ca. 24 days. For this purpose, the required power output of the photovoltaic panels was estimated for moderate sunlight conditions. In summer, the surplus of electricity generated by the photovoltaic panels will be transmitted to the power grid or used for repair works in the dock. Any shortages of energy, e.g., in winter, will be covered by energy from the power grid.

5.2. Determination of Parameters of the Environmentally Friendly Power Supply System for the Dock Moving and Stabilising System

Table 7 lists the calculated technical and operational parameters of wire winches. The rated power output of one winch is ca. 10 kW (for maximum forces in the wires and a wind speed of 5°B; see Figure 10). The real power output of the winch power supply system depends on the prevailing weather conditions (i.e., wind speed during the operation of moving the dock; see Figure 10). Wind speed is a random value; a cumulative distribution function of wind speed frequency (°B) for the most unfavourable wind directions is shown in Figure 4. This means that the real power output of the winches during the docking of a ship will also be random and will depend on the actual wind speed and direction relative to the dock.

Based on the calculated loads of the system’s wires (Figure 10), the maximum loads on the wires by wind speed (°B) have been quantified. For the resultant values, the real power output of the winches has been determined, depending on wind speed (Figure 13).

It follows from the analyses that

• The least favourable wind direction relative to the dock is NE (Table 4), and its probability in a year is 6%;
• The frequency of a NE wind of a speed of up to 3°B (distribution function) is 97% (Figure 4);
• For a wind direction of NE and speed 3°B, the maximum force in the system’s wires is 19 kN (Figure 13a), and the real power output of the winches is 2.9 kW (Figure 13b);
• For other wind directions, e.g., W or E, although they have a higher frequency (41% and 14.2%, respectively (Table 4)), the maximum forces in the wires for wind speed 3°B are smaller than those for a NE wind, and the real power output of the winches is lower (Figure 10).

It results from the analysis above that the parameters of the environmentally friendly power supply system for the hydraulically driven dock moving system can be determined based on the maximum load on the wires and the power output of the winches for a wind speed of 3°B and direction of NE. The determined parameters are listed in

Table 8. Parameters of the environmentally friendly power supply system for the hydraulically driven dock moving system.

Parameter	Unit of Measurement	Value
Real power output of winches during moving of the dock away from the quay	kW	7
Real power output of winches during pulling of the dock to the quay	kW	10
Energy consumption during moving of the dock away from the quay	kWh	4
Energy consumption during pulling of the dock to the quay	kWh	6
Total energy consumption in one operational cycle	kWh	10
Planned number of docking operations during a year	-	16
Required battery capacity	kWh	15
Battery charging time (in periods between docking operations)	day	24

below.

5.3. Eco-Friendly Dock Moving Power Supply System Setup

The selection and configuration of photovoltaic panels is discussed, inter alia, in [29,30].

The authors of [29] provide an integrated review of factors influencing the efficiency of photovoltaic panels. Environmental factors, installation, and the construction and materials of the panels, as well as the operating conditions, are examined.

In [30], PV panels which are best suited for use in households are investigated. Although application of such panels is obviously different, the article is a valuable source of information considering the location of the panels, which is similar to the location of the dock.

Another important topic is appropriate selection of batteries and optimal management of the generated energy [31]. Energy management is often discussed in the context of road transport (electric buses), e.g., in [32]. Problems of energy management and optimisation of energy consumption in ports are reviewed in [33].

Using the information and conclusions contained in the available literature, a system of photovoltaic panels to power the MSPD system has been designed.

Based on the total energy consumption during one full cycle of the MSPD system operation and the planned number of dockings during the year, the annual energy demand for the system has been determined. It amounts to 170 kWh and is relatively small for modern photovoltaic (PV) systems. The process of designing a PV system requires a thorough analysis of the geographical location of the facility at which it will be installed, its immediate surroundings, and the installation site. Factors such as sunlight conditions and shaded areas (including those caused by the shape of the facility and surrounding buildings, trees, etc.) are crucial for the selection of appropriate PV panels. It should be noted that, with the current standards for PV panels, an output power of ca. 220 W/m² is obtained.

For the expected demand for electricity, panels of 2278 × 1134 mm, in a popular standard for panels within the power range of 550–600 W, have been selected. The designed installation consists of eight Tiger Neo JKM-575N-72HL4-BDV panels from Jinko (Wuxi City, China) with an output power of 575 Wp each, i.e., a total of 4.6 kWp of rated power. These bifacial, double glass panels capture sunlight from both sides of the panel.

The PV installation is supplemented with a three-phase, hybrid STP 15–50 inverter from SMA (Niestetal, Germany) and an SMA Home Storage 16.4 energy bank with a capacity of 16.40 kWh and a discharge power of 6.0 kW. Configured in this way, the system ensures flexible control of the stored energy consumption, offers an output power suitable for powering the wire winches, and can be expanded in the future. Ultimately, it will generate 4028 kWh per year (calculated with SMA Sunny Design software ver. 1.5), and will be characterised by an energy yield of 834 kWh/kWp at an efficiency of 84.7%. Monthly energy yields are shown in Figure 14. Considering that the demand for the system is 170 kWh, the surplus of 3858 kWh can be used for purposes other than the docking operations.

6. Trials and Tests of the Dock Moving System

The dock was launched in September 2023. A series of tests and trials of moving the dock and submerging it over the dock trench was carried out on a fully equipped dock in November 2023. The first tests checked the system for moving the dock, submerging it, stabilising it in position, and pulling the elevated dock with the ship to the quay. The tests and trials validated the complete functionality of the dock:

• The dock can be moved at a distance of 27 m away from the quay;
• The dock can be moved in maximum weather conditions corresponding to a wind speed of 5°B;
• The dock can be submerged to a depth of 10 m;
• The time required to move the dock a distance of 27 m is ca. 26 min;
• During the docking operation, the dock can be stabilised in position within the adopted tolerance levels.

Early 2024 saw the first planned dockings and repairs of ships in the mobile dock using the dock moving and stabilising system. It can be seen in the photos (Figure 15) that the wire and winch system was applied to move and stabilise the dock in position without the use of tug boats. The operation of moving the dock and docking the ship was successful. Thus, full controllability of the dock and its operational parameters has been achieved.

The power supply system (photovoltaic panels) for the dock moving devices has been in use since early 2024, i.e., for about 6 months. Measurements are being taken and data and experience from the designed PV system are gathered. Assessment of its reliability, including, without limitation, in extreme weather conditions, as well as long-term costs of maintenance, will only be possible after at least one year of operation. It should be noted here that the eco-friendly power supply system is a prototype solution, and will most probably be subject to modification in the future.

It has been mentioned before that ca. 16 ship repairs are planned per year, which corresponds to the number of docking operations and times the MSDP system will be used. Since the MSDP system does not operate on a continuous basis, its operation can be scheduled for spells of good weather when it can be powered by the PV system. Based on the data and experience gathered during the trial operation of the MSDP system, the authors plan to develop an energy management system to ensure its effective use, including in the period between dockings during the ship’s repair.

7. Conclusions

Following a thorough analysis of the literature and Internet resources, a conclusion can be made that the designed floating dock moving and stabilising system is an innovative solution supporting the docking of a ship in the dock trench.

The MSDP system ensures mobility of the floating dock and its stability in position during a docking operation, and meets all the requirements and criteria for proper operation of the system in the maximum weather conditions, corresponding to a wind speed of 5°B.

One of the significant advantages of the system is the use of renewable energy. The electricity required to power the system is generated by photovoltaic panels and stored in batteries. The set of panels was selected with a view to storing energy required to power the system for one hour. An ample reserve of energy will be available, since one complete cycle of moving the dock away from the quay lasts ca. 35 min. Thus, this is a system with zero greenhouse gas emissions and zero carbon footprint.

The parameters of the environmentally friendly power supply system (photovoltaic panels) were calculated based on the probability of certain weather conditions (wind speed and direction relative to the dock). Calculated for a wind speed of 3°B (in spite of the fact that the MSDP system was designed for a wind speed of 5°B), the system parameters have proven to be sufficient for the design under analysis.

The developed MSDP system completely eliminates the necessity to use port tugs, which are powered by combustion engines.

The system moving the dock is currently operated manually by operators of the wire winches. A concept of automated control, using sensors and computer software, is under development.

This research study can definitely be considered innovative. Owing to the application of an environmentally friendly energy source to power the system, the solution meets environmental protection requirements. The MSDP system can be used in shipyards situated at river canals, where ships cannot be pulled into a dock positioned along the quay. Further research is being conducted towards a solution where the wire and winch system can be operated at one quay only, without the need to use the opposite quay which may sometimes cause the need to stop navigation on the canal. The new wire and winch system under development will use dead anchors instead of tying wires to bollards at the opposite quay.