Renewable energy enhanced combined cycle for LH2 carrier ship

Abstract

Achieving global climate change mitigation targets requires serious solutions to the global energy sources decarbonisation. Hydrogen as a clean alternative fuel represents a successful and viable option to achieve the future zero-carbon target, and it is considered a leading contender as a fuel for the future economy, and it is anticipated that there will be a strong demand for vessels capable of transporting liquefied hydrogen from the production to the consumption sites. However, the seaborn transportation of hydrogen represents a significant gap in the hydrogen supply chain; this leads to the following philosophical question: what would the hydrogen carrier ship look like? The novel contributions of this study are to present a design and evaluation for a liquefied hydrogen (LH2) tanker fuelled by hydrogen named JAMILA in support of decarbonisation, storage and transportation of liquefied hydrogen with a total capacity of ~280,000 mᶟ as a cargo and uses the boil-off gas for propulsion for the loaded leg of the journey. A hydrogen-fuelled combined-cycle gas turbine was modelled and examined as a ship prim-mover to achieve the twin objectives of high efficiency and zero-carbon footprint. Also, the study presents an economic analysis of a liquefied hydrogen tanker, to determine the viability of using such ships to transport hydrogen in the future to contribute toward implementing a green hydrogen economy. In terms of operation, the LH2 tanker was simulated for different journeys under various conditions to assess the ship's performance in terms of efficiency and environmental aspects. Moreover, the design was developed by implementing a set of 6 Flettner rotors for the JAMILA ship to achieve the fuel-saving and emission reduction targets. Established methods were employed using state-of-the-art design and analysis for determining the LH2 tank sizing, ship hull design, ship stability, and ship characteristics. Additionally, the ship propulsion system was designed and evaluated based on the ship resistance requirements in off-design and degraded performance of the gas-turbine topping cycle. Moreover, a techno-economic and environmental risk assessment (TERA) method were developed to evaluate the suggested design in different conditions such as loaded and unloaded conditions, a normal and 6% degraded engine, and various weather conditions in different scenarios. The results indicated that the LH2 tanker could carry 20,000 tonnes of liquefied hydrogen in a fully loaded with a displacement tonnage of 232,000 tonnes, and the design has been shown to be stable. The liquid hydrogen boil-off is supplied to the ship's main engine, thereby saving 29% of the liquefied hydrogen fuel consumption of the ship in the fully loaded condition. Its propulsion system contains a combined-cycle gas turbine of approximately 50 MW. The results reveal that the output power allows ship operation at a great speed even with a degraded engine and adverse ambient conditions. However, implementing 6 Flettner rotors for the LH2 tanker ship impacts the performance and leads to environmental benefits. A maximum contribution power of around 1.8 MW was achieved, saving approximately 3.6% of the combined- cycle gas turbine total output power (50 MW) and causing a 3.5% reduction in NOx emissions. Economically, the results indicate that the JAMILA ship's implementation can cover the ship's capital cost within no more than 2.5 and 6 years in the best and worst-case maritime shipping prices conditions, respectively. The economic assessment results indicate a promising perception of the future development of sustainable energy systems and provide new information that is important for bridging the gap between research, development, and implementation of a green hydrogen economy that will contribute to mitigating climate change. Investments in ships such as the vessel designed and evaluated in this study represent an essential constituent of the decarbonisation process and could be one of the solutions to achieving almost the zero- emissions target in the future. This study definitively answers the question regarding the hydrogen tankers design and assessments.