Applications & Pathways

The increasing global demand for sustainable energy solutions has intensified the need to replace fossil fuels in gas turbines particularly in aviation and power generation where alternatives to gas turbines are currently limited. This review explores the feasibility of utilizing sustainable liquid and gaseous fuels in gas turbines by evaluating their environmental impacts performance characteristics and technical integration potential. The study examines a broad range of alternatives including biofuels hydrogen alcohols ethers synthetic fuels and biogas focusing on their production methods combustion behavior and compatibility with existing turbine technology. Key findings indicate that several bioderived and synthetic fuels can serve as viable drop-in replacements for conventional jet fuels especially under ASTM D7566 standards. Hydrogen and other gaseous alternatives show promise for industrial applications but require significant combustion system adaptations. The study concludes that a transition to sustainable fuels in gas turbines is achievable through coordinated advancements in combustion technology fuel infrastructure and regulatory support thus enabling meaningful reductions in greenhouse gas emissions and advancing global decarbonization efforts.

This study presents the design and techno-economic comparison of two standalone photovoltaic (PV) systems each supplying a 1 kW critical load with 100% reliability under Cairo’s climatic conditions. These systems are modeled for both the constant and the night load scenarios accounting for the worst-case weather conditions involving 3.5 consecutive cloudy days. The primary comparison focuses on traditional lead-acid battery storage versus green hydrogen storage via electrolysis compression and fuel cell reconversion. Both the configurations are simulated using a Python-based tool that calculates hourly energy balance component sizing and economic performance over a 21-year project lifetime. The results show that the PV/H2 system significantly outperforms the PV/lead-acid battery system in both the cost and the reliability. For the constant load the Levelized Cost of Electricity (LCOE) drops from 0.52 USD/kWh to 0.23 USD/kWh (a 56% reduction) and the payback period is shortened from 16 to 7 years. For the night load the LCOE improves from 0.67 to 0.36 USD/kWh (a 46% reduction). A supplementary cost analysis using lithium-ion batteries was also conducted. While Li-ion improves the economics compared to lead-acid (LCOE of 0.41 USD/kWh for the constant load and 0.49 USD/kWh for the night load) this represents a 21% and a 27% reduction respectively. However the green hydrogen system remains the most cost-effective and scalable storage solution for achieving 100% reliability in critical off-grid applications. These findings highlight the potential of green hydrogen as a sustainable and economically viable energy storage pathway capable of reducing energy costs while ensuring long-term resilience.

The turbocharged dual-fuel engine is modeled and connected online to optimiser platform for transient input variation of input parameters decided by designed algorithms. This task is undertaken to enable intelligent control of the propulsion system including the Hydrogen injection instantly to reduce the thermal irreversibility. Therefore two methods of optimisation are applied to data collected from a turbocharged dual fuel operated propulsion system with direct diesel fuel injection and hydrogen port injection. This study investigates the application of multi-objective game theory (MOGT) and non-dominated sorting genetic algorithm II (NSGA-II) for optimising the performance of a diesel-hydrogen dual-fuel engine. The system is designed in 1D framework with input variability of the turbocharger efficiency hydrogen mass injection air compression ratio (Rp) and start of combustion (SoC). The objective is to set maximized the volume work while minimising the entropy generation and NO emission. The first populations in the optimisation procedures are initialised with uniform Latin hypercube and random space filler design of experiment (DoE) for both optimisers. The MOGT can find the best solution faster than NSGA-II with slightly better result. The statistics showed that MOGT generates 12 more unfeasible designs that do not meet the constraint limit on NO emission. The findings indicate that for different optimisation algorithms there are some factors with different effect direction and size on the objectives. Addi tionally it is discovered that although MOGT solution makes higher objective function value the NSGA-II optimal solution leads to better engine efficiency and lower fuel consumption.

Due to increasing energy demand limited fossil fuels and increasing greenhouse gasses people is in need for alternative energy sources to have a sustainable world. The objective of this study is to look for alternative solutions and design a hybrid energy system to meet any energy needs of a single family house including both utility and transportation. The system is designed and optimized using HOMER software. According to the optimization studies levelized cost of electricity and hydrogen production was found to be 0.685$/kWh and 6.85$/kg respectively and the cost of hydrogen which is half of its market price is very attractive. To project possible future costs in advance sensitivity analysis was carried out and the results show that when the main components’ price decays to the half both costs of energy will be reduced by 26.4%. This implies that further decrease on the components’ cost would bring the cost of energy to the level of energy produced by fossil fuels or even lower. Hydrogen would also be produced with much lower and tempting price. It is important to note that energy used by residential electrical load and fuel cell electric car in this study was generated by sole renewable energies and the system consumes zero fossil fuels thus emitting no greenhouse gasses. The study considering both utility and transportation simultaneously is believed to be the first on a small scale and to attract the interest of everyone.

With the gradual maturity of wind power technology China’s wind power generation has grown rapidly over the recent years. However due to the on-site inconsumable electricity the phenomenon of large-scale “wind curtailment” occurs in some areas. In this paper a novel hybrid hydrogen/electricity refueling station is built near a wind farm and a part of the surplus wind power is used to charge electric trucks and the other part of the surplus power is used to produce “green hydrogen”. According to real-time load changes different amounts of liquid hydrogen and gas hydrogen can be properly coordinated to provide timely energy supply for hydrogen trucks. For a 400 MW wind farm in the western Inner Mongolia China the feasibility of the proposed system has been carried out based on the sensitivity and reliability analysis the static and dynamic economic modeling with an entire life cycle analysis. Compared to the conventional technology the initial investment of the proposed scheme (700.07 M$) decreases by 13.97% and the dynamic payback period (10.93 years) decreases by 25.87%. During the life cycle of the proposed system the accumulative NPV reaches 184.63 M$ which increases by 3.14 times compared to the case by conventional wind technology.

Trains have been a crucial part of modern transport and their high energy efficiency and low greenhouse gas emissions make them ideal candidates for the future transport system. Transitioning from diesel trains to hydrogen fuel cell electric trains is a promising way to decarbonize rail transport. That’s because the fuel cell electric trains have several advantages over other electric trains such as lower life-cycle emissions and shorter refueling time than battery ones and less requirements for wayside infrastructure than the ones with overhead electric wires. However hydrogen fuel technology still needs to be advanced in areas including hydrogen production storage refueling and on-board energy management. Currently there are several pilot projects of hydrogen fuel cell electric trains across the globe especially in developed countries including one commercialized and permanent route in Germany. The experiences from the pilot projects will promote the technological and economic feasibility of hydrogen fuel in rail transport.

Modern energy conversion technologies with low or no emissions are needed to achieve sustainable development goals. This research examines the thermodynamic and exergy-economic features of a high-temperature proton exchange membrane fuel cell. A cutting-edge integrated energy system uses high-temperature proton exchange membrane fuel cells an organic Rankine cycle a proton exchange membrane electrolyzer and a multi-effect desalination unit. This setup generates electricity hydrogen and fresh water. Methanol-steam reformation produces hydrogen for the fuel cell. The recommended cycle drives an organic Rankine power producing cycle using 120-200 °C waste heat from hightemperature proton exchange membrane fuel cell to power water electrolysis and hydrogen generation. An integrated method incorporates energy and exergy balances and cost analysis to assess the proposed system's exergetic economic and environmental impacts. The suggested integration delivers high energy and exergy efficiency at an acceptable cost and environmental effect. According to parametric research boosting the fuel cell's working temperature decreases production costs and carbon dioxide emissions per mass. Raising current density has positive technical and environmental impacts. As the current density increases from 0.4 to 0.8 (A/cm2 ) the net power generation increases to 46.67% and the exergy efficiency increases from 64.5% to 68%. An increase in multi-effect distillation motivate steam pressure from 200 to 600 kPa results in an increase in the daily freshwater generated from 111.68 m3 to 116.41 m3 . For environmental protection and output optimization fuel utilization ratio must be reduced. The ideal system's exergy efficiency product unit cost and environmental impact are 65.78% 86.28 ($/h) and 4.33% respectively.

Healthcare facilities in isolated rural areas of sub-Saharan Africa face challenges in providing essential health services due to unreliable energy access. This study examines the use of hybrid renewable energy systems consisting of solar PV wind turbines batteries and hydrogen storage for the electrification of rural healthcare facilities in Nigeria and South Africa. The study deployed the efficacy of Hybrid Optimization of Multiple Energy Resources software for techno-economic analysis and the Evaluation based on the Distance from Average Solution method for multicriteria decision-making for sizing optimizing and selecting the optimal energy system. Results show that the optimal configurations achieve cost-effective levelized energy costs ranging from $0.336 to $0.410/kWh for both countries. For the Nigeria case study the optimal energy system includes 5 kW PV 10 kW fuel cell 10 kW inverter 10 kW electrolyzer and 16 kg hydrogen tank. South Africa's optimal configuration has 5 kW PV 10 kW battery 10 kW inverter and 7.5 kW rectifier. Solar PV provides more than 90% of energy with dual axis tracking yielding the highest output: 8889kWh/yr for Nigeria and 10470kWh/yr for South Africa. The multi-criteria decisionmaking analysis reveals that Nigeria's preferred option is the hybrid system without tracking. In contrast the horizontal axis weekly adjustment tracking configuration is optimal for South Africa considering technical economic and environmental criteria. The findings highlight the importance of context-specific optimization for hybrid renewable energy systems in rural healthcare facilities to accelerate Sustainable Development Goals 3 and 7.

This paper delves into the enhancement and optimization of on-grid renewable energy systems using a variety of renewable energy sources with a particular focus on large-scale applications designed to meet the energy demand of a certain load. As global concerns surrounding climate change continue to mount the urgency of replacing traditional fossil fuel-based power generation with cleaner more cost-effective and dependable alternatives becomes increasingly apparent. In this context a comprehensive investigation is conducted on grid connected hybrid energy system that combines photovoltaic wind and fuel cell technologies. The study employs three state-of-the-art optimization algorithms namely Walrus Optimization Algorithm (WaOA) Coati Optimization Algorithm (COA) and Osprey Optimization Algorithm (OOA) to determine the optimal system size and energy management strategies all aimed at minimizing the cost of energy (COE) for grid-based electricity. The results of the optimization process are compared with the results obtained from the utilization of the Particle swarm optimization (PSO) and Grey Wolf optimizer (GWO). The findings of this study underscore both the practical feasibility and the critical importance of adopting on-grid renewable energy systems to decrease the dependence on traditional energy sources within the grid. The proposed WaOA succeeded to reach the optimal solution of the optimal design process with a COE of 0.51758129611 $//kwh while keeping the loss of power supply probability (LPSP) the reliability index at 7.303681e-19. The practical recommendations and forwardlooking insights provided within this research hold the potential to foster sustainable development and effectively mitigate carbon emissions in the future.

Germany aligned with the European Union has set important targets for decreasing greenhouse gas emissions by 65% by 2030 and achieving climate neutrality by 2045. In this context Power-to-X fuels have emerged as promising solutions for defossilizing transport modes less suitable for electrification. However a significant challenge in developing Power-to-X fuels is the absence of a well-defined regulatory framework for their production and utilization. Thus this study investigates the regulatory landscapes of the EU and Germany aiming to comprehend objectives support schemes and advancements. A total of 25 legal frameworks from the EU and Germany with direct or indirect effects on Power-to-X fuels were identified. For a detailed and comprehensive policy analysis a qualitative inductive approach based on a coding scheme and policy content analysis was implemented. Findings indicate that several updates in the German and EU regulatory frameworks addressed Power-to-X fuels in the 2010s and 2020s. The RED III the REFuelEU Aviation and the FuelEU Maritime have shown to be turning points for Power-to-X fuels in the EU. In Germany the most relevant policies are the 37. BImSchV the National Hydrogen Strategy and the PtL Roadmap. Key challenges are identified related to the limited coherence among policies supporting the sustainable use of resources for the fuel production.

Because ammonia is easier to store and transport over long distances than hydrogen it is a promising research direction as a potential carrier for hydrogen. However its low ignition and combustion rates pose challenges for running conventional ignition engines solely on ammonia fuel over the entire operational range. In this study we attempted to identify a stable engine combustion zone using a high-pressure direct injection of ammonia fuel into a 2.5 L spark ignition engine and examined the potential for extending the operational range by adding hydrogen. As it is difficult to secure combustion stability in a low-temperature atmosphere the experiment was conducted in a sufficiently-warmed atmosphere (90 ± 2.5 ◦C) and the combustion emission and efficiency results under each operating condition were experimentally compared. At 1500 rpm the addition of 10% hydrogen resulted in a notable 20.26% surge in the maximum torque reaching 263.5 Nm in contrast with the case where only ammonia fuel was used. Furthermore combustion stability was ensured at a torque of 140 Nm by reducing the fuel and air flow rates.

This research explores the optimal operation of an offshore wave-powered hydrogen system specifically designed to supply electricity and water to a bay in Humboldt California USA and also sell it with hydrogen. The system incorporates a desalination unit to provide the island with fresh water and feed the electrolyzer to produce hydrogen. The optimization process utilizes a mixture of experts in conjunction with the Quantitative Structure-Activity Relationship (QSAR) algorithm traditionally used in drug design to achieve two main objectives: minimizing operational costs and maximizing revenue from the sale of water hydrogen and electricity. Many case studies are examined representing typical electricity demand and wave conditions during typical summer winter spring and fall days. The simulation optimization and results are carried out using MATLAB 2018 and SAM 2024 software applications. The findings demonstrate that the combination of the QSAR algorithm and quantum-inspired MoE results in higher revenue and lower costs compared to other current techniques with hydrogen sales being the primary contributor to increased income.

This work discusses the current scenario and future growth of electrochemical energy devices such as water electrolyzers and fuel cells. It is based on the pivotal role that hydrogen can play as an energy carrier to replace fossil fuels. Moreover it is envisaged that the scaled-up and broader deployment of the technologies can hold the potential to address the challenges associated with intermittent renewable energy generation. From a sustainability perspective this synergy between hydrogen and electricity from renewable sources is particularly attractive: electrolyzers convert the excess energy from renewables into green hydrogen and fuel cells use this hydrogen to convert it back into electricity when it is needed. Although this transition endorses the ambitious goal to supply greener energy for all it also entails increased demand for the materials that are essential for developing such cleaner energy technologies. Herein several economic and environmental issues are highlighted besides a critical overview regarding each technology. The aim is to raise awareness and provide the reader (a non-specialist in the field) with useful resources regarding the challenges that need to be overcome so that a green hydrogen energy transition and a better life can be fully achieved.

The transport sector heavily relies on the use of fossil fuels which are causing major environmental concerns. Solutions relying on the direct or indirect use of electricity through efuel production are emerging to power the transport sector. To ensure environmental benefits are achieved over this transition an accurate estimation of the impact of the use of electricity is needed. This requires a high temporal resolution to capture the high variability of electricity. This paper presents a previously unseen temporal analysis of the carbon intensity of e-fuels using grid electricity in countries that are members of the European Network of Transmission System Operators (ENTSO-E). It also provides an estimation of the potential load factor for producing low-carbon e-fuels according to the European Union legislative framework. This was achieved by building on top of the existing EcoDynElec tool to develop EcoDynElec_xr a python tool enabling—with an hourly time resolution—the calculation visualisation and analysis of the historical time-series of electricity mixing from the ENTSO-E. The results highlight that in 2023 very few European countries were reaching low carbon intensity for electricity that enables the use of grid electricity for the production of green electrolytic hydrogen. The methodological assumptions consider the consumption of the electricity mix instead of the production mix and the considered time step is of paramount importance and drastically impacts the potential load factor of green hydrogen production. The developed tools are released under an open-source license to ensure transparency result reproducibility and reuse regarding newer data for other territories or for other purposes.

The aviation industry is facing challenges related to its environmental impact and thus the pressing need to develop aircraft technologies aligned with the society climate goals. Hydrogen is emerging as a potential clean fuel for aviation as it offers several advantages in terms of supply potential and weight specific energy. One of the key factors enabling the use of H2 in aviation is the development of reliable and safe storage technologies to be integrated into aircraft design. This work provides an overview of the technologies currently being investigated or developed for the storage of hydrogen within the aircraft which would enable the use of hydrogen as a sustainable fuel for aviation with emphasis on tanks material and structural aspects. The requirements dictated by the need of integrating the fuel system within existing or ex-novo aircraft architectures are discussed. Both the storage of gaseous and liquid hydrogen are considered and the main challenges related to the presence of either high internal pressures or cryogenic conditions are explored in the background of recent literature. The materials employed for the manufacturing of hydrogen tanks are overviewed. The need to improve the storage tanks efficiency is emphasized and issues such as thermal insulation and hydrogen embrittlement are covered as well as the reference to the main structural health monitoring strategies. Recent projects dealing with the development of onboard tanks for aviation are eventually listed and briefly reviewed. Finally considerations on the tank layout deemed more realistic and achievable in the near future are discussed.

Currently green hydrogen generated through renewable energy sources stands out as one of the best substitutes for fossil fuels in mitigating pollutant emissions and consequent global warming. Particularly the utilization of hydrogen in spark ignition engines has undergone extensive study in recent years. Many aspects have been analyzed: the conversion of gasoline engines to hydrogen operation the combustion duration the heat transfer and in general the engine thermal efficiency. Hydrogen combustion is characterized by a smaller quenching distance compared to traditional hydrocarbon fuels such as gasoline or natural gas and this produces a smaller thermal boundary layer and consequently higher heat transfer. This paper presents findings from experimental trials and numerical simulations conducted on a hydrogen-powered CFR (cooperative fuel research) engine focusing specifically on heat transfer with combustion chamber walls. The engine has also been fueled with methane and isooctane (two reference fuels); both the engine compression ratio and the air/fuel ratio have been changed in a wide range in order to compare the three fuels in terms of heat transfer combustion duration and engine thermal efficiency in different operating conditions. A numerical model has been calibrated with experimental data in order to predict the amount of heat transfer under the best thermal efficiency operating conditions. The results show that when operated with hydrogen the best engine efficiency is obtained with a compression ratio of 11.9 and an excess air ratio (λ) of 2.

In the latest OIES podcast from the Hydrogen Programme James Henderson talks to Abdurahman Alsulaiman about his latest paper entitled “Navigating Turbulence: Hydrogen’s Role in the Decarbonisation of the Aviation Sector.” In the podcast we discuss the current balance of fuels in the aviation sector the importance of increasing efficiency of aero-engines and the impact of increasing passenger miles travelled. The podcast then considers different decarbonisation options for the sector focussing on a change of engine technology to allow the use of alternative fuels such as hydrogen or electricity but also looking at the potential for hydrogen to play an important role in the development of Sustainable Aviation Fuels (SAFs) for use with current engine technology. We also look at Low Carbon Aviation Fuels which are essentially existing fuels derived from a significantly decarbonised supply chain and assess whether they have an important role to play as the aviation sector targets a net zero outcome.

The podcast can be found on their website.

Reversible solid oxide cells (rSOC) enable the efficient cyclic conversion between electrical and chemical energy in the form of fuels and chemicals thereby providing a pathway for longterm and high-capacity energy storage. Amongst the different fuels under investigation hydrogen methane and ammonia have gained immense attention as carbon-neutral energy vectors. Here we have compared the energy efficiency and the energy demand of rSOC based on these three fuels. In the fuel cell mode of operation (energy generation) two different routes have been considered for both methane and ammonia; Routes 1 and 2 involve internal reforming (in the case of methane) or cracking (in the case of ammonia) and external reforming or cracking respectively. The use of hydrogen as fuel provides the highest round-trip efficiency (62.1%) followed by methane by Route 1 (43.4%) ammonia by Route 2 (41.1%) methane by Route 2 (40.4%) and ammonia by Route 1 (39.2%). The lower efficiency of internal ammonia cracking as opposed to its external counterpart can be attributed to the insufficient catalytic activity and stability of the state-of-the-art fuel electrode materials which is a major hindrance to the scale-up of this technology. A preliminary cost estimate showed that the price of hydrogen methane and ammonia produced in SOEC mode would be ~1.91 3.63 and 0.48 $/kg respectively. In SOFC mode the cost of electricity generation using hydrogen internally reformed methane and internally cracked ammonia would be ~52.34 46.30 and 47.11 $/MWh respectively.

The refining industry is shifting from decarbonization to hydrogenation for processing heavy fractions to reduce pollution and improve efficiency. However the carbon footprint of hydrogen production presents significant environmental challenges. This study couples refinery linear programming models with life cycle assessment to evaluate from a long-term perspective the role of low-carbon hydrogen in promoting sustainable and profitable hydrogenation refining practices. Eight hydrogen-production pathways were examined including those based on fossil fuels and renewable energy providing hydrogen for three representative refineries adopting hydrogenation decarbonization and co-processing routes. Learning curves were used to predict future hydrogen cost trends. Currently hydrogenation refineries using fossil fuels benefit from significant cost advantages in hydrogen production demonstrating optimal economic performance. However in the long term with increasing carbon taxes hydrogenation routes will be affected by the high carbon emissions associated with fossil-based hydrogen losing economic advantages compared to decarbonization pathways. With increasing installed capacity and technological advancements low-carbon hydrogen is anticipated to reach cost parity with fossil-based hydrogen before 2060. Coupling renewable hydrogen is expected to yield the most significant economic advantages for hydrogenation refineries in the long term. Renewable hydrogen drives the transition of refining processing routes from a decarbonization-oriented approach to a hydrogenation-oriented paradigm resulting in cleaner refining processes and enhanced competitiveness under emission-reduction pressures.

Growing expectations are being placed on green hydrogen-based steel for decarbonising the global steel industry. However the scale of the expected demand is dispersed across numerous case studies resulting in a fragmented picture. This study examines 28 existing scenarios to provide a cohesive view of future global demand. In the short term the demand for green hydrogen-based steel is expected to be limited constituting 2% of current total steel production by 2030. However a transformation phase is expected around 2040 marked by accelerated growth. By 2050 global demand is projected to reach 660 Mt (with an interquartile range of 368–1000 Mt) equivalent to 35% (19%–53%) of current total steel production. To meet such growing demand green hydrogen supply and electrolyser capacity will need to increase to more than 1000 times current levels by 2050. These trends highlight both short-term limitations and long-term potential. Decarbonisation efforts will therefore require immediate emission reductions with already scalable options while simultaneously building the enabling infrastructure for green hydrogen-based steelmaking to ensure long-term impacts.

Global warming’s major cause is the emission of greenhouse-effect gases (GHG) especially carbon dioxide (CO2) whose main source is the combustion of fossil fuels. Fossil fuels serve as the primary energy source in many industries including shipping which is the focus of this study. One of the measures proposed to tackle GHG emissions is the development of green shipping corridors - carbon-free shipping routes that require the transition to alternative fuels which are gaining competitiveness. One of the reasons for that is carbon pricing which taxes CO2 emissions. However the lack of consensus on the most cost-advantageous alternative fuel in the long run results in the delay of the implementation of green shipping corridors. To make it more accessible for stakeholders to conduct an economic analysis of the various options a framework to determine and minimize the costs of transitioning from fossil fuels to any alternative fuel is proposed over the period of one voyage considering the lost opportunity cost the deployment cost of bunkering vessels at the necessary call ports the cost of converting the vessel the car-bon emissions tax cost and the fuel cost. This will allow stakeholders to choose the most economical alternative fuel accelerating the development of green shipping corridor initiatives. To validate the effectiveness of the framework it was applied in a case study involving a shipowner seeking to transition from heavy fuel oil (HFO) to Ammonia Hydrogen Liquefied Natural Gas (LNG) or Methanol. This study faced limitations due to the unknown costs of installing bunkering vessels for Ammonia and Hydrogen. However it evaluates the cost-effectiveness of alternative fuels providing insights into their short-term economic viability. The results showed that Hydrogen is the most costadvantageous fuel until a deployment cost per bunkering vessel of 1990285$ for a sailing speed of 22 knots and 2190171$ for a sailing speed of 18 knots is reached after which LNG becomes the most economical option regardless of variations in the carbon tax. Moreover a sensitivity analysis was conducted to determine the effects of variations in parameters such as carbon tax fuel prices and vessel conversion costs in the total cost of each fuel option. Results highlighted that even though HFO remains the most economical fuel option even when considering a high increase in carbon tax the cost gap between HFO and alternative fuels narrows significantly with the increase in carbon tax. Furthermore the sailing speed impacts the fuels’ competitiveness as the cost difference between HFO and alternative fuels decreases at higher speeds.

Integrated hydrogen energy systems (IHESs) have attracted extensive attention in miti-gating climate problems. As a kind of large-scale hydrogen storage device undergroundhydrogen storage (UHS) can be introduced into IHES to balance the seasonal energy mis-match while bringing challenges to optimal operation of IHES due to the complex geolog-ical structure and uncertain hydrodynamics. To address this problem a deep deterministicpolicy gradient (DDPG)-based optimal scheduling method for underground space basedIHES is proposed. The energy management problem is formulated as a Markov decisionprocess to characterize the interaction between environmental states and policy. Based onDDPG theory the actor-critic structure is applied to approximate deterministic policy andactor-value function. Through policy iteration and actor-critic network training the oper-ation of UHS and other energy conversion devices can be adaptively optimised which isdriven by real-time response data instead of accurate system models. Finally the effective-ness of the proposed optimal scheduling method and the benefits of underground spaceare verified through time-domain simulations.

To meet the International Maritime Organization’s (IMO) goal of decarbonising the shipping sector by 2050 zero-emission ship propulsion systems should be developed to replace conventional fossil fuel-based ones. In this study we propose a zero-emission hybrid hydrogen-wind-powered propulsion system to be retrofitted to a benchmark merchant ship with a conventional propulsion system. The ship and its propulsion systems are modelled using an in-house platform. We analyse power and energy requirements for the ship over a realistic route and one-year schedule factoring in actual sea and weather conditions. Initially we examine the battery-powered propulsion system which proves impractical even with a reduction in the ship’s speed and the addition of a charging station. This retrofitted battery-powered propulsion system will occupy a significant portion of the existing ship’s deadweight due to its substantial weight consequently reducing the ship’s cargo capacity. To address this we evaluate integrating a hydrogen-powered fuel cell system with power equal to the non-propulsive constant load in the ship. We demonstrate that under these conditions and with four Flettner rotors and the charging station positioned mid-port on the ship’s route the size of the zero-emission propulsion system can be approximately 20% of the deadweight rendering such a system feasible.

The most practical way of storing hydrogen gas for fuel cell vehicles is to use a composite overwrapped pressure vessel. Depending on the driving distance range and power requirement of the vehicles there can be various operational pressure and volume capacity of the tanks ranging from passenger vehicles to heavy-duty trucks. The current commercial hydrogen storage method for vehicles involves storing compressed hydrogen gas in high-pressure tanks at pressures of 700 bar for passenger vehicles and 350 bar to 700 bar for heavy-duty trucks. In particular hydrogen is stored in rapidly refillable onboard tanks meeting the driving range needs of heavy-duty applications such as regional and line-haul trucking. One of the most important factors for fuel cell vehicles to be successful is their cost-effectiveness. So in this review the cost analysis including the process analysis raw materials and manufacturing processes is reviewed. It aims to contribute to the optimization of both the cost and performance of compressed hydrogen storage tanks for various applications.

High-speed passenger vessels have high greenhouse gas emissions per passenger kilometre trav elled and require optimizations to provide a role in a low carbon society. This article works to wards this goal as a study of the potential for replacing high-speed passenger vessels with compressed hydrogen or battery electric zero emission solutions. To do this a model was developed based on automatic identification system data to calculate energy use for the existing Norwegian fleet in 2018. Using modelled energy consumption and assuming a maximum battery weight or compressed hydrogen volume each vessel can carry the most likely candidates for replacement were identified. Results showed that 51 out of 73 vessels are most suitable for hydrogen propulsion with 12 also suitable for battery electric propulsion. However timetable and route changes are required for more vessels to be suitable. Route optimisation studies are therefore required along with further detailed feasibility studies of the identified candidates and infrastructure requirements.