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"Tugboats"
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Little Tug
Little Tug knows what to do when the tall ship, the speedboat, and the ocean liner need him, and at such times, he is indispensible.
Book
Analysis of Hull Shape Impact on Energy Consumption in an Electric Port Tugboat
The trend to replace internal combustion engines with electric zero-emission drives, visible in the automotive industry, also exists in the shipbuilding industry. In contrary to land vehicles, the requirements for the electric propulsion system of tugs are much greater, which combined with the limited space and energy on board, makes any amount of energy valuable. Strategic changes in the policy of many countries, such as the “Fit for 55” package, introduce plans to significantly reduce CO2 emissions, which favors the development of alternative drives and their introduction to new areas of operation. This article presents that it is possible to reduce the amount of energy an electric tug spends for movement by applying the Particle Swarm Optimization method to modify the shape of its hull. A statistical analysis of public data was performed to determine the speed profiles of actual port tugs. The Van Oortmerssen method was used to determine the hull resistances of the proposed tug and the impact of the hull shape modification sets on reducing these resistances. Based on the six obtained speed profiles, it was determined that one of the tested variants of modifications made it possible to reduce energy consumption on average by 2.12%, to even 3.87% for one of the profiles, and that some modifications increase energy consumption by even 6.59%.
Journal Article
Little Toot
Little Toot the tugboat conquers his fear of rough seas when he single-handedly rescues an ocean liner during a storm. On board pages.
Book
Structural evaluation of a pusher-tug vessel to comply with the requirements for navigation in ice covered waters
The design of a standalone ice breaker vessel destined for inland navigation could be a costly solution for a temporary problem, due to the limited period of time when the vessel is engaged in ice breaking operations. The Romanian Authorities have in their possession a dedicated ice breaker, Perseus, destinated to clear the navigation path on the Maritime Danube River but which cannot navigate upstream on the Fluvial Danube River due to its draft limitations. As a consequence, most vessels trading from Braila and upstream are exposed to high risks due to the possibility of being trapped in ice formations that could be dangerous for both for the crew and vessels during the winter season. A viable solution is represented by designing a removable ice breaker module that could be attached to the existing fleet of pusher vessels. Since it is not a stand-alone vessel, it will not require a dedicated crew onboard and will only operate when ice dams are created along the river and the navigation path needs to be cleared. The existing fleet of pusher vessels is not prepared to navigate in ice covered water and thus structural reinforcement are required to comply with the requirements provided by classification society. The current paper presents the evaluation of the existing structure of a pusher vessel and proposes means of reinforcement to comply with ICE B class notation provided by DNV Class Society. The paper will conclude on the definition of the ice belt area (LIWL, UIWL) along the ship’s side and will provide scantling information for the new structure within the ice belt area.
Journal Article
Little Toot : pictures and story
Little Toot the tugboat conquers his fear of rough seas when he single-handedly rescues an ocean liner during a storm.
BOOK
Joint Scheduling of New Energy Hybrid Tugboats and Berths Under Shore Power Constraint
With the rapid advancement of battery technology, new energy hybrid tugboats have been progressively adopted. In order to align with the trend of electrifying tugboat fleets, a mixed-integer linear programming (MILP) model for the joint scheduling of new energy hybrid tugboats and berths has been established. The model incorporates the constraint imposed by the limited number of tugboat charging connectors. The objective is to minimize the total cost over the scheduling horizon, including ship waiting, delayed-departure costs, and the operating costs of both conventional diesel and hybrid tugboats. In light of the characteristics inherent to the problem, a hybrid solution approach combining CPLEX with a heuristic-enhanced whale optimization algorithm (WOA) is employed to solve the model. A case study was conducted using data on the energy consumption of tugboats at Xiamen Port. The effectiveness of the model and algorithm was then verified through a series of small-scale instance experiments. Finally, a comprehensive sensitivity analysis of key parameters is finally conducted, including the number of tugboat charging connectors, battery capacity, and charging rate. This analysis provides valuable guidance for port tugboat operations.
Journal Article
Scuffy the tugboat
A toy tugboat that doesn't want simply to live in a toy store or sail in a bathtub gets more than he bargained for when he makes a getaway.
Book
Comparative Analysis of Carbon Intensity Indicators Applicable to Harbor Tugboats
This study compares four carbon intensity indicators applicable to harbor tugboats to identify the most representative greenhouse gas emissions management. Using operational data from SAAM Towage’s fleet, the indicators evaluated traveled distance, operating time, energy consumption, and average engine load demand. Statistical analyses revealed that the energy consumption-based indicator exhibited lower variability and greater capacity to reflect the operational particularities of tugboats. In contrast, indicators based on average load presented high dispersion, limiting their applicability. These conclusions highlight the importance of considering vessel-specific characteristics when selecting indicators. This work provides tools to improve environmental monitoring and facilitates the implementation of sustainability strategies aligned with the maritime industry’s emission reduction objectives.
Journal Article
Logic-Based Benders Decomposition for Unmanned Electric Tugboat Scheduling Considering Battery-Swapping Operations
As the electrification reform accelerates in ports worldwide, the application of electric tugboats is becoming more widely applied, posing a challenge in the balance between working arrangement and energy replenishment, especially when the shore energy replenishment facilities are limited. Aligning with the emerging trends of port electrification, unmanned operations, and intelligentization, this paper investigates unmanned electric tugboat scheduling considering battery-swapping operations that combine the assignment of tasks to the working periods of tugboats, the allocation of battery-swapping operations to the shore battery-swapping stations, and the sequencing of operations at each station. The problem is formulated into a mixed-integer linear programming to minimize the total completion time of the battery-swapping operations. A logic-based Benders decomposition method is proposed that decomposes the problem into a master problem and a subproblem. The master problem relaxes the sequencing constraints and solves the assignment of tasks to tugboats and the allocation of battery-swapping operations to stations. The SP, based on the solution to the master problem, determines the sequencing of battery-swapping operations at each station. Considering the interdependence of swapping operations of each tugboat that might be allocated to different stations, a dispatching heuristic is designed to efficiently obtain high-quality sequences for the stations. Numerical experiments are conducted based on 80 randomly-generated instances with up to 100 tasks, ten tugboats, and six battery-swapping stations. The results demonstrate that LBBD is capable of solving all 80 instances, whereas the commercial solver CPLEX fails to solve those with 80 or more tasks. Moreover, the average computational time of CPLEX on the instances it can solve is 241.32 s, nearly 32 times that of LBBD (7.57 s). This clearly indicates that LBBD significantly outperforms CPLEX in terms of both computational capacity and efficiency. Further analyses show that the increase in the number of tugboats will significantly shorten the makespan and make ETSBS easier to solve, while the increase in the number of battery-swapping stations makes the problem more challenging with longer computational time.
Journal Article
A Review of Autonomous Tugboat Operations for Efficient and Safe Ship Berthing
Autonomous ship technology, which includes real-time monitoring, satellite communication, and automatic navigation, is rapidly advancing. Despite significant research on single unmanned ships, there is a lack of studies on complex tasks, such as ship berthing using a swarm of autonomous tugboats. This review article provides an overview of various projects related to autonomous tugboats for ship berthing and discusses the research trends in the required technologies, including recognition, decision making, modeling, and control. We identify the areas that have been underexplored in existing studies and suggest future research directions to advance the field. Overall, this review contributes to a better understanding of the challenges and opportunities for the development of autonomous tugboats for ship berthing.
Journal Article