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Economic analysis and the EEXI reduction potential of parallel hybrid dual-fuel engine‒fuel cell propulsion systems for LNG carriers

Ammar Nader R., Almas Majid, Nahas Qusai

Polish Maritime Research

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2023

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nr 3

59--70

EN

One potential solution for reducing carbon dioxide emissions from ships and meeting the Energy Efficiency Existing Ship Index (EEXI) requirements is to use a hybrid propulsion system that combines liquid hydrogen and liquefied natural gas fuels. To improve energy efficiency for diesel-electric dual-fuel ship propulsion systems, an engine power limitation system can also be used. This paper examines the potential use of these systems with regard to several factors, including compliance with EEXI standards set by the International Maritime Organization, fuel ratio optimisation, installation requirements, and economic feasibility. As a case study, an LNG carrier is analysed, with dual-fuel diesel-electric and two hybrid systems adjusted to meet IMO-EEXI requirements with engine power limitation percentages of 25%, 0% (hybrid option 1), and 15% (hybrid option 2), respectively. From an economic standpoint, the liquid hydrogenbased system has competitive costs compared to the dual-fuel diesel-electric system, with costs of 2.1 and 2.5 dollars per kilogram for hybrid system options 1 and 2, respectively.

2

Evaluating an inland waterway cargo vessel’s energy efficiency indices

Kalajdžić Milan, Vasilev Matija, Momčilović Nikola

Polish Maritime Research

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2022

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nr 2

27--34

EN

Although the International Maritime Organization (IMO) introduced the energy efficiency requirements for ships more than a decade ago, to date, inland navigation has not been affected by corresponding regulations at all. Therefore, inland waterway vessels are left with no mandatory requirements that could push their technology into more energy efficient design. Fortunately, there are certain pioneering attempts to define energy efficiency criteria for inland vessels. This paper tries to gather and provide a review of such methods. Moreover, a typical Danube cargo inland vessel’s data are used to evaluate their current energy efficiency levels with respect to provisional criteria. Consequently, two methods are found and used here. They are both based on IMO’s energy efficiency concept but modified for the inland waterway vessels. The methods delivered a significant difference in applicability and were difficult to compare. Moreover, shallow and deep-water effects are explored in the same regard but provided unsound conclusions. The final results displayed discrepancies in energy efficiency levels for the same vessels and so the methodology should be improved and harmonised, if it is to be introduced as mandatory for inland waterway vessels. The analysis provided a glimpse into the current condition of the traditional design of the Danube inland fleet, with respect to the emerging energy efficiency policies.

3

Prediction of the amount of waste cold from liquefied natural gas (LNG) regasification for gas-fuelled low-speed main engines

Korlak Piotr Kamil

Zeszyty Naukowe Akademii Morskiej w Szczecinie

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2021

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nr 68 (140)

69--79

EN

Existing and future regulations on ship energy efficiency and methods for their improvement are presented in this work. The design and operational features of gas-fuelled low-speed main engines, liquefied natural gas (LNG) regasification conditions, and amount of waste cold are compared. Using a simple linear regression model based on the least squares method, formulae were developed to predict the amount of waste cold as a function of the brake power of gas-fuelled low-speed main engines operating under ISO ambient conditions in Tier III-compliant mode. A sufficiently accurate prediction of the waste cold amount at the initial design stage is feasible due to the formulae developed as part of this work