Assessment of Emission Reduction and Fuel Savings using Ship Speed Optimization in Realistic Weather Conditions

In this work, our objective is to quantify emission reductions using speed optimization considering a realistic ship route and a broad range of weather conditions. Two representative bulk carriers have been selected for the analysis. An optimization algorithm has been used to minimize voyage fuel consumption while completing the voyage on or before the expected arrival time. A constraint on engine power has been used for realistic estimates of achievable ship speeds in different weather conditions considering the available engine power. Multiple voyages at different ship speeds and in different seasons have been simulated with and without speed optimization to observe the effect of these factors on emission reduction. The effect of wind and waves on engine power has been considered by calculating wind and wave resistance along with propeller efficiency as a function of advance coefficients. Up to 11% reduction in fuel consumption was obtained by optimizing speed as compared to the constant speed profile. It was observed that a significant amount of fuel could be saved especially in seasons with a higher likelihood of heavy weather. Variation in fuel savings in different seasons has been discussed in the context of metocean conditions experienced in the selected months. Additionally, higher fuel savings were obtained for lower average ship speed which means speed reduction combined with speed optimization has greater potential to reduce emissions. Realistic estimates of fuel savings in a range of operating conditions presented in this paper would help ship owners, operators, and policymakers to assess the benefits of speed optimization among other technologies to decarbonize the shipping industry

The Effect of Waves on Marine Propellers and Propulsion

Ship design is evolving around ever-increasing market demands in quest of competitive and cost-effective solutions. The global increase of shipping activities has raised concerns regarding the environmental impact of sea operations- transportation, fishing and exploitation of offshore resources. These conditions have driven naval architects to look for novel and energy efficient ship designs. Currently, there is increasing demand to optimize ships for actual environmental conditions i.e. in the presence of wind, waves, etc. The work in this thesis explores the effect of waves on ship propulsion; it consists of two major parts. First, the analysis of propulsion system in the presence of waves where the effects of added resistance, wake variation, propulsion losses and propeller-engine interactions have been studied on engine efficiency, propulsion efficiency, power and RPM fluctuations in waves. It was found that the effect of waves on engine performance is relatively small, for the studied cases, however; wake variation and propulsion losses can cause considerable changes in vessel performance. The second part deals with propeller performance in terms of cavitation, pressure pulses and efficiency in the presence of waves. The effects of wake change, speed loss, RPM variation and ship motions have been investigated. It was found that wake variations in waves has by far the largest impact on pressure pulses. Therefore, it is recommended to consider wake variation in waves while designing propellers. Due to the practical difficulties in doing this, which mainly are related to determining the wake variations, the recommended compromise is to consider the wake variation in one regular wave of length close to the ship length. A framework of systematic analysis laid out in this thesis would be useful for analyzing different propulsion systems and propeller designs in the presence of waves. Methods and tools used in the work can be further incorporated into the optimization process to consider the effect of waves. The investigation in this thesis will help the optimization as various factors affecting the propulsion have been recognized and their effect has been quantifie

Analysis of Propulsion Performance of KVLCC2 in Waves

In this paper, we have analyzed the propulsion performance of KVLCC2 in presence of waves. Different factors affecting the propulsion performance have been studied. Analysis of the extent of change in wake quality and its effect on the cavitation of propeller has been presented. Effect of wake change alone was separately calculated to analyze its importance in the design process, as wake data in waves is usually not available. It was observed that wake change itself does not significantly affect the amount of cavitation hence; cavitation margin should be considered only to handle increased load and relative stern motion

Effect of waves on cavitation and pressure pulses of a tanker with twin podded propulsion

There is increasing interest in optimizing ships for the actual operating condition rather than just for calm water. In order to optimize the propeller designs for operations in waves, it is essential to study how the propeller performance is affected by operation in waves. The effect of various factors that influence the propeller is quantified in this paper using a 8000 dwt chemical tanker equipped with twin-podded propulsion as a case vessel. Propeller performance in waves in terms of cavitation, pressure pulses, and efficiency is compared with the performance in calm water. The influence of wake variation, ship motions, RPM fluctuations and speed loss is studied. Substantial increase in cavitation and pressure pulses due to wake variation in the presence of waves is found. It is found that the effect of other factors is relatively small and easier to take into account as compared to wake variation. Therefore, considering the wake variation at least in the critical wave condition (where the wavelength is close to ship length) in addition to calm water wake is recommended in order to ensure that the optimized propeller performs well both in calm water and in waves

Statistical modeling of Ship’s hydrodynamic performance indicator

The traditional method used to estimate the hydrodynamic performance of a ship uses either the model test results or one of the many empirical methods to estimate and observe the trend in fouling friction coefficient () over time. The biggest weakness of this method is that the model test results as well as the empirical methods used here is sometimes not well-fitted for the full-scale ship due to several reasons like scale effects and, therefore, this method may result in an inaccurate performance prediction. Moreover, in the case of a novel ship design, it would be nearly impossible to find a well-fitting empirical method. The current work establishes a new performance indicator, formulated in the form of generalized admiralty coefficient with displacement and speed exponents statistically estimated using the in-service data recorded onboard the ship itself. The current method completely removes the dependence on empirical methods or model test results for the performance prediction of ships. It is observed here that the performance predictions using the current method and the traditional method are based on the same underlying logic as well as the results obtained from both the methods are found to be in good agreement