Analysis and assessment of partial re-liquefaction system for liquefied hydrogen tankers using liquefied natural gas (LNG) and H2 hybrid propulsion

“…Moreover, a recently built storage tank by NASA [80] features an integrated refrigeration system, leading to net zero boil-off [80][81][82], with a trade-off of additional capital expenditures of 3.1 million USD (0.06 USD • kg −1 of BOG per year) and an energy demand of 6.33 kWh el • kg −1 BOG . Other estimates in the literature assume capital costs (CCs) of 6.85-7.42 USD • kg −1 of BOG per year and energy demand of 3.3-11.0 kWh el • kg −1 BOG [83,84] for re-liquefaction.…”

Section: 3mentioning

confidence: 99%

Techno-economic assessment of long-distance supply chains of energy carriers: Comparing hydrogen and iron for carbon-free electricity generation

Neumann¹,

Rocha²,

Debiagi³

et al. 2023

Preprint

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The effective usage of renewable energy sources requires ways of storage and delivery to balance energy demand and availability divergences. Carbon-free chemical energy carriers are proposed solutions, converting clean electricity into stable media for storage and long-distance energy trade. Among them, hydrogen (H 2 ) is noteworthy, being the subject of significant investment and research. Metal fuels, such as iron (Fe), represent another promising solution for a clean energy supply, but establishing an interconnected ecosystem still requires considerable research and development. This work proposes a model to assess the supply chain characteristics of hydrogen and iron as clean, carbon-free energy carriers and then examines case studies of possible trade routes between the potential energy exporters Morocco, Saudi Arabia, and Australia and the energy importers Germany and Japan. The work comprehends the assessment of economic (levelized cost of electricity -LCOE), energetic (thermodynamic efficiency) and environmental (CO 2 emissions) aspects, which are quantified by the comprehensive model accounting for the most critical processes in the supply chain. The assessment is complemented by sensitivity and uncertainty analyses to identify the main drivers for energy costs. Iron is shown to be lower-cost and more efficient to transport in longer routes and for long-term storage, but potentially more expensive and less efficient than H 2 to produce and convert. Uncertainties related to the supply chain specifications and the sensitivity to the used variables indicate that the path to viable energy carriers fundamentally depends on efficient synthesis, conversion, storage, and transport. A break-even analysis demonstrated that clean energy carriers could be competitive with conventional energy carriers at low renewable energy prices, while carbon taxes might be needed to level the playing field. Thereby, green iron shows potential to become an important energy carrier for long-distance trade in a globalized clean energy market.

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“…The value of e reliq is dependent on the cryogenic fuel undergoing reliquefaction; due to its lower boiling point, LH2 requires more energy to reliquefy than LNG. Its value and the value of η gen can be determined from the literature (e.g., References [45][46][47][48]56,57]).…”

Section: Power Consumption and Fuel Utilisationmentioning

confidence: 99%

Modelling of Boil-Off and Sloshing Relevant to Future Liquid Hydrogen Carriers

2022

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This study presents an approach for estimating fuel boil-off behaviour in cryogenic energy carrier ships, such as future liquid hydrogen (LH2) carriers. By relying on thermodynamic modelling and empirical formulas for ship motion and propulsion, the approach can be used to investigate boil-off as a function of tank properties, weather conditions, and operating velocities during a laden voyage. The model is first calibrated against data from a liquefied natural gas (LNG) carrier and is consequently used to investigate various design configurations of an LH2 ship. Results indicate that an LH2 ship with the same tank volume and glass wool insulation thickness as a conventional LNG carrier stores 40% of the fuel energy and is characterised by a boil-off rate nine times higher and twice as sensitive to sloshing. Adding a reliquefaction unit can reduce the LH2 fuel depletion rate by at least 38.7% but can increase its variability regarding velocity and weather conditions. In calm weather, LH2 boil-off rates can only meet LNG carrier standards by utilising at least 6.6 times the insulation thickness. By adopting fuel cell propulsion in an LH2 ship, a 1.1% increase in fuel delivery is expected. An LH2 ship with fuel cells and reliquefaction is required to be at least 1.7 times larger than an existing LNG carrier to deliver the same energy. Further comparison of alternative scenarios indicates that LH2 carriers necessitate significant redesigns if LNG carrier standards are desired. The present approach can assist future feasibility studies featuring other vessels and propulsion technologies, and can be seen as an extendable framework that can predict boil-off in real-time.

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Analysis and assessment of partial re-liquefaction system for liquefied hydrogen tankers using liquefied natural gas (LNG) and H2 hybrid propulsion

Cited by 39 publications

References 40 publications

Hydrogen liquefaction: a review of the fundamental physics, engineering practice and future opportunities

Hydrogen liquefaction: a review of the fundamental physics, engineering practice and future opportunities

Techno-economic assessment of long-distance supply chains of energy carriers: Comparing hydrogen and iron for carbon-free electricity generation

Modelling of Boil-Off and Sloshing Relevant to Future Liquid Hydrogen Carriers

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