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Reducing fuel usage and CO2 emissions from tug boat fleets: Sea trials and theoretical modelling
Abstract
Sea trials on a harbour tug have been conducted and are explained. The experimental results for fuel consumption per unit transport effort, under free-running (transiting) conditions, are presented and engine speed-propulsor pitch combinations for improved fuel economy are identified. A simplified analytical approach to predict fuel consumption, including the coupled engine-propulsor-hull system, is described. This rationale is combined with experimental observations and, consequently, performance maps present the complete operating envelopes of the harbour tug under both free-running and towing conditions. This combined approach proved to be effective and can be applied to the study of other tug vessels. As a consequence of this research, the engine control system on the harbour tug was modified to permit it to operate fully within the region of best fuel economy during free-running. The results from the bollard-pull predictions provide insight for the design and operation of harbour tugs in the future.
... As a result of the analysis carried out by Murphy et al. (2012), a new "eco-button" has been installed, which corresponds to an additional engine rotational speed setting of approximately 33%. Murphy et al. (2012) claim that a reduction of approximately 20% in fuel consumption could be made at a speed of 67% of the maximum recorded value. ...
... As a result of the analysis carried out by Murphy et al. (2012), a new "eco-button" has been installed, which corresponds to an additional engine rotational speed setting of approximately 33%. Murphy et al. (2012) claim that a reduction of approximately 20% in fuel consumption could be made at a speed of 67% of the maximum recorded value. The following analysis will determine if this claim has any foundation, and whether or not the eco-button is being utilised. ...
... In the time between which the sea-trials were undertaken, and the time the data for analysis was recorded, a new "eco-button" engine speed selector has been installed on the basis vessel. The "eco-button" is based upon the work of Murphy et al. (2012), who suggest a reduction in fuel consumption of approximately 20% at 67% speed-over-ground would result from the installation of this new engine speed setting. The results of this analysis suggests that the tug boat skippers are actively using the eco-button, and that the eco-button is indeed providing reduced fuel consumption. ...
There are incentives from maritime regulatory bodies to operate ships more efficiently, driven by the need to reduce CO2 budget.
In order to genuinely establish more efficient ship operations, fuel consumption across the full operational profile of a vessel is needed. This could be accomplished through a complete characterisation through extensive sea-trials, or interpretation of data from monitoring systems. Results from repeated testing under highly controlled sea-trial conditions provides high-fidelity data, however, this approach is prohibitively expensive and requires repeating as the condition of the vessel changes with time. Conversely, data monitoring devices are relatively inexpensive, however, the process of analysing data can be complex, particularly when a ship's activities are diverse.
This paper describes a methodology for associating ship activity with corresponding segments of a data-stream from a commercially available monitoring system. Further analysis is then performed to determine the fuel efficient performance of the ship. The case-study used in this paper is a harbour tug, although the approach used is applicable to other ship types, its success on this basis indicates the methodology is robust. To validate the methodology, results from the data analysis are compared to fuel consumption data measured under sea-trial conditions, and are found to be in close agreement.
... Trodden et al. (2015) analyzed fuel consumption and speed over the ground using a continuous data stream from a tug boat. Murphy et al. (2012) used fuel consumption data and engine load from sea trials to investigate reduction in fuel consumption. Zaman et al. (2017) presented a statistical analysis to automatically detect the vessel operational modes (port, manoeuvring, sailing) based on sensor data acquired on board as a pre-cursor to modelling fuel consumption in transit mode. ...
New regulations in the shipping sector aim to give greater transparency to operations and public access to CO2 emissions data. EU regulation 2015/757 became mandatory in January 2018 and urges shipping companies to set up systems for daily monitoring, reporting and verification (MRV) of emissions for individual ships. Manual acquisition and handling of emissions data may be allowed (e.g. bunker fuel delivery note, bunker fuel tank monitoring), but is adversely affected by uncertainty due to human intervention and will eventually be unusable for monitoring purposes. However, the massive amounts of navigation data acquired by multi-sensor systems installed on-board of modern ships have great potential to aid compliance with regulations but their use is hampered by the lack of effective analytical methods in the maritime literature. This work demonstrates a statistical framework and automatic reporting system for fuel consumption monitoring that addresses the MRV requirements needed to comply with the regulations. The framework has been applied to the Grimaldi Group’s Ro-Ro Pax cruise ships and is shown, in addition, to be capable of supporting fault detection as well as verifying CO2 savings achieved after energy efficiency initiatives.
... Acquiring reliable and validated data is the first step towards optimisation of systems, fault detection and forecasting vessel performance. Knowledge of the detailed energy flow architecture and the relative proportions of energy consumed during the different operations and within each system or component will give a better understanding for decision making on improving energy efficiency and subsequently reducing the overall fuel consumption and reduce the impact of emissions [33]. The next phase is to conduct a careful analysis on the information obtained through this methodology to gain useful knowledge that can contribute to future designs and operations of vessels. ...
Ship performance monitoring is increasingly necessary due to continued pressures to reduce environmental impacts and operational costs throughout ship and fleet lifecycles. It also has the potential to enhance the structural design and improve the crew's safety. The current technology is enabling the development of highly robust monitoring platforms to continuously capture many diverse aspects of the ship and fleet activity in the ocean. The near future will see further enhancements of performance monitoring with the widespread advancement of sensor technology, data capture techniques, data filtering and cloud-based storage capacity. This must be coupled to further innovations in big data analysis to interpret and effectively exploit these real-world laboratory experiments. Conventional practice exploits design calculations, small-scale tests and numerical analyses to predict the full-scale ship performance. A body of diverse research activities at Newcastle University challenges this conventional approach by demonstrating the use of the real world as a laboratory. This paper discusses a multi-dimensional ship performance envelope which includes: on-board energy flow distribution; environmental impact and emissions; power and propulsion, structural response and the socioeconomic aspects of ship operations.
At present, the sensitivity of society towards emissions in commercial maritime ports is increasing, which is reflected in the large number of studies on the control of emissions in them, perhaps because the most important commercial ports are located in cities with high population density. The objective of this work was to determine the greenhouse gas emissions caused by the activity of the Spanish tugboat fleet, studying the tugboat fleet of the eleven autonomous coastal Spanish communities from 2004 to 2017 and their impact on the carbon footprint of the country’s shipping sector. To do this, the methodology used by the International Maritime Organization for merchant ships to estimate the emissions of a tugboat fleet is formalized, and Gini concentration index methodology was applied to the concentration of emissions from this fleet. This has made it possible to obtain results on the distribution of the concentration of emissions from Spanish ports by region, age, and size, as well as to establish the profile of the tugboat port that pollutes the most and its carbon footprint. One of the results is that in the period analyzed, the concentration of emissions from the Spanish tugboat fleet increased if we looked at its distribution by region, and decreased if we look at its distribution by age and size. This is because tugboat activity was very different by region; however, their characteristics related to age and size evolved in a more homogeneous way.
The effects of exhaust gas emissions from all modes of shipping are a subject of concern for two main reasons. Firstly, they contribute CO 2, causing anthropogenic global climate change and, secondly, other exhaust gas species, e.g. PM, NO x, SO x, are detrimental to environmental and human health. This second point is of particular concern where high-levels of shipping activity occur in regions of high population density. To address this, there are a variety of technological mitigation methods and devices. This paper provides an analysis of these technologies in terms of their effectiveness and suitability against a range of exhaust gas species of interest. Furthermore, another approach to reduce harmful emissions is to modify the way in which ships are operated, and this requires accurate prediction of emissions for all operational conditions, machinery and ship types. This paper therefore also reports on research being conducted to predict these emissions.
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