A Novel Control Strategy on Stable Operation of Fuel Gas Supply System and Re-Liquefaction System for LNG Carriers

Liquefied natural gas has attracted attention through an explosive increase in demands and environmental requirements. During this period, the Energy Efficiency Design Index (EEDI), which was adopted by the International Maritime Organization, expecting to significantly reduce CO2 from ships, has become an important key. It has triggered a change in use from steam turbine systems and dual fuel diesel electrics to high-efficiency main engines such as ME-GI engines to meet the EEDI requirements. However, since the ME-GI engines use 300 bar of fuel gas pressure, it is necessary to resolve problems of the pressure controllability and to prevent the reductions of the re-liquefaction amount caused by clogging of the lubricant mixed with the fuel gas during the compression. The purpose of this study is to propose a novel control strategy with a newly developed configuration for controlling the pressure so as not to trip the BOG compressors when the ME-GI engines are tripped, and for preventing a reduction on re-liquefaction amount. Unlike the typical configuration used in the current vessels, this proposal separately provides the fuel gas at 150 bar without lubricants to the re-liquefaction. In addition, three control strategies are proposed, depending upon the application of multi-controllers and the location of the pressure transmitters. A simulation was conducted to verify the efficacy of the proposed method, focusing on the controllability of the pressure and the re-liquefaction amount, in comparison with the typical configuration. As results of the simulation, the proposal showed excellent controllability without trips of the BOG compressors even in abnormal conditions and confirmed the great re-liquefaction performance.

Assessment of Energy Efficiency and Ship Emissions from Speed Reduction Measures on a Medium Sized Container Ship

Greenhouse gases and other emissions from vessels and related activities in maritime trade have caused significant environmental impacts especially global warming of the atmosphere. Consequently, the International Maritime Organization (IMO) concern significant care to the reduction of ship emissions and improvement of energy efficiency through operational and technical measures. The proposed short-term measure is ship speed reduction in which the ship speed is reduced below its designed value. Therefore, the present paper aims at evaluating the potential energy efficiency and environmental benefits from using speed reduction measure through energy efficiency design index (EEDI), energy efficiency operational indicator (EEOI) and ship emissions calculation models as recommended from IMO. As a case study, a medium sized Container Ship is investigated. The results show that, reducing ship speed by 12.6% will reduce CO2 emissions by about 36%. Moreover, the attained EEDI value will be improved by 31.7% and comply with not only the current IMO requirements but also with the future ones. Additionally, reducing ship speed by 12.6% will reduce EEOI value from its value at design speed by 26.5%. Furthermore, it is noticed that SOx emission will comply with IMO 2020 limit if ship speed is reduced by 6.8% and above.

Research on Main Engine Power of Transport Ship with Different Bows in Ice Area According to EEDI Regulation

The Energy Efficiency Design Index (EEDI) has been applied to ship carbon emission standards since 2013, ice ships subject to the Finnish Swedish Ice Class Rules (FSICR) also need to meet the requirements of EEDI. In this study, the engine power requirements by EEDI at different stages for the considered ice class ships with different ice classes (1C, 1B, 1A, 1A Super) are compared with engine power requirements obtained from the resistance calculated by FSICR or Lindqvist method. Three different bow shapes for the considered ice class ships and different pack ice coverage are studied. The results from FSICR or Lindqvist formula show that 1A Super ice classes for all considered bow shapes cannot meet the requirement by EEDI at Phase 2 and 3; For 1B and 1A class, some bow shapes can meet the EEDI requirement for all stages, but some cannot; For 1C class, all bow shapes can meet the EEDI requirements for all stages. The ship main engine power requirements under different pack ice concentration are studied and compared to EEDI requirements.

Thermal Efficiency and Economics of a Boil-Off Hydrogen Re-Liquefaction System Considering the Energy Efficiency Design Index for Liquid Hydrogen Carriers

This study analyzes the thermodynamic, economic, and regulatory aspects of boil-off hydrogen (BOH) in liquid hydrogen (LH2) carriers that can be re-liquefied using a proposed re-liquefaction system or used as fuel in a fuel cell stack. Five LH2 carriers sailing between two designated ports are considered in a case study. The specific energy consumption of the proposed re-liquefaction system varies from 8.22 to 10.80 kWh/kg as the re-liquefaction-to-generation fraction (R/G fraction) is varied. The economic evaluation results show that the cost of re-liquefaction decreases as the re-liquefied flow rate increases and converges to 1.5 $/kg at an adequately large flow rate. Three energy efficient design index (EEDI) candidates are proposed to determine feasible R/G fractions: an EEDI equivalent to that of LNG carriers, an EEDI that considers the energy density of LH2, and no EEDI restrictions. The first EEDI candidate is so strict that the majority of the BOH should be used as fuel. In the case of the second EEDI candidate, the permittable R/G fraction is between 25% and 33%. If the EEDI is not applied for LH2 carriers, as in the third candidate, the specific life-cycle cost decreases to 67% compared with the first EEDI regulation.

Ship Energy Efficiency Measures and Climate Protection

This paper addresses the importance of the implementation and enforcement of the energy efficiency measures for ships. These measures are frequently referred to and used as a tool for carbon mitigation by reducing greenhouse gas emissions from ships in order to protect the Earth’s climate. Moreover, these measures can also play an important role in climate adaptation. The purpose of this paper is to look briefly at the current and expected impact of the ships’ energy efficiency measures developed under auspices of the International Maritime Organization, i.e.: the Energy Efficiency Design Index (EEDI) and the Ship Energy Efficiency Management Plan (SEEMP) on climate change mitigation. Both of them, EEDI and SEEMP became mandatory measures after the adoption of amendments to the Annex VI of the International Convention for the Prevention of Pollution from Ships (MARPOL), and their entry into force in 2013. Furthermore, those measures were also the first legally binding tools relating to climate change, adopted since the Kyoto Protocol.

Optimization of Resistance Performance for Inland Twin-Skeg Ship Based on CFD and Surrogate Modeling

With the increasingly serious energy problems in the world and the introduction of Energy Efficiency Design Index (EEDI) by International Maritime Organization (IMO), the application of energy conservation and emission reduction methods in ships has been paid more and more attention. With the rapid development of computational fluid dynamics (CFD), ship hull form optimization based on CFD has become a hot topic, Inland twin-skeg ship has a relatively complicated hull form, and it has strong theoretical significance and engineering practical value to carry out hull form optimization research on this type of ship. Based on the multidisciplinary comprehensive optimization platform for ship hydrodynamic performance (SHIPMDO-WUT) self-developed by Wuhan University of Technology research institute of multidisciplinary design optimization of ship performance, this paper using the hull surface deformation method based on the radial basis function interpolation to change the hull form and skeg shape of a 3000t inland twin-skeg oil tanker with invisible bulbous bow. And the high-precision CFD calculation software SHIPFLOW was used to predict the resistance of this ship. Finally, combined with CFD surrogate model and optimization algorithm, the ship with excellent resistance performance is obtained and ensuring the ship displacement and the longitudinal position of the buoyancy center are within the range of certain constraints. At last, the optimization results were verified numerically.

Application of Energy Saving Bow Shape in Actual Seas to JBC

Energy Efficiency Design Index (EEDI) entered Phase 2 in 2020. In this situation, ship performance in actual seas is more important than ever. As an energy saving bow shape in actual seas, the authors are developing a bow shape named “COVE (Concave shape optimized in waves)”. The aim of COVE is to improve performance in waves without deteriorating performance in a calm sea by transformation above the static swell up at the target speed. Since the bow shape is concave above the static swell up, COVE reduces waves reflected forward because the most concave line has a fine triangular shape instead of the blunt shape of the original. In this paper, COVE is applied to a Capesize bulk carrier, the JBC (Japan Bulk Carrier). The parameters of COVE are examined and the shape is optimized for the JBC. The effect of COVE is validated by tank tests in terms of wave lengths, wave angles, wave heights and ship speeds. The results clarified the fact that COVE reduces added resistance in waves by approximately 30 % in head waves compared with the original shape. Validity was verified by the radiating wave shape and the side wall wave form recorded by a video camera in the tests.

To estimation of the Energy Efficiency Design Index (EEDI) for a ship with energy-saving wing devices

В статье приводится оценка индекса проектной энергетической эффективности (EEDI) для судна с энергосберегающими крыльевыми устройствами на встречном регулярном волнении. Вначале на основе предыдущих работ авторов с применением линейной теории поперечных сечений определяются характеристики продольной (вертикальной и килевой) качки судна без крыльев, и такого же судна с крыльями большого удлинения, установленными на днище вблизи оконечностей с целью преобразования волновой энергии в дополнительную тягу. После определения параметров качки судна с крыльями как твердого тела, с применением теории Теодорсена колеблющегося профиля определяется средняя по периоду тяга энергосберегающих крыльевых элементов, совершающих поступательно-вращательные колебания. С другой стороны, в статье находится общее сопротивление системы «судно-крыльевые элементы». При этом применяется метод Холтропа в сочетании с теорие Бейкельмана-Герритсмы. Последняя дает возможность произвести оценку дополнительного волнового сопротивления по найденным параметрам продольной качки судна с крыльями и без крыльев. Затем оценивается значение индекса проектной энергетической эффективности (EEDI) контейнеровоза, снабженного энергосберегающими крыльями на встречном волнении. Исследование показывает, что установка на днище крыльевых элементов может использоваться как один из способов сокращения выброса углекислого газа и уменьшения в соответствии с требованиями Международной морской организации ИМО, значения индекса EEDI для репрезентативных морских условий. In this paper an estimation is presented of the Energy Efficiency Design Index (EEDI) for a ship with energy-saving wing devices in headwind regular waves. At first, based on previous works of the authors, there are determined with use of linear strip theory the characteristics of longitudinal (heaving and pitching) motions of a ship without wings and identical ship equipped with wings of large aspect ratio fitted on the bottom near extremities for the purpose of converting wave energy into additional thrust. After motions of the ship with wings as a solid boy are determined Theodorsen theory of oscillating foil is applied to calculate period averaged thrust of energy-saving wing elements, performing combined heave-pitch oscillations. On the other hand, the paper addresses the problem of determining overall drag of the “wing-plus-wings” system with use of Holtrop method combined with Beikelmann-Gerritsma theory. The latter enables carrying out an estimation of additional wave resistance based on the calculated parameters of the ship longitudinal motions with and without wings. Then follows an estimation of the EEDI for a containership equipped with wings in headwind regular waves. The study shows that fitting wing elements on the ship bottom can be seen as one of the methods for decreasing the magnitude of the EEDI for representative sea conditions as per requirements of the International Maritime Organization.