Applications & Pathways

The maritime industry is under increasing pressure to reduce greenhouse gas emissions especially in countries such as Saudi Arabia that are actively working to transition to cleaner energy. In this paper a new hybrid shipboard power system which incorporates wind turbines solar photovoltaic (PV) panels proton-exchange membrane fuel cells (PEMFCs) and a battery energy storage system (BESS) together for propulsion and hotel load services is proposed. A multi-loop Energy Management System (EMS) based on proportional–integral control (PI) is developed to coordinate the interconnections of the power sources in real time. In contrast to the widely reported model predictive or artificial intelligence optimization schemes the PI-derived EMS achieves similar power stability and hydrogen utilization efficiency with significantly reduced computational overhead and full marine suitability. By taking advantage of the high solar irradiance and coastal wind resources in Saudi Arabia the proposed configuration provides continuous near-zeroemission operation. Simulation results show that the PEMFC accounts for about 90% of the total energy demand the BESS (±0.4 MW 2 MWh) accounts for about 3% and the stationary renewables account for about 7% which reduces the demand for hydro-gas to about 160 kg. The DC-bus voltage is kept within ±5% of its nominal value of 750 V and the battery state of charge (SOC) is kept within 20% to 80%. Sensitivity analyses show that by varying renewable input by ±20% diesel consumption is ±5%. These results demonstrate the system’s ability to meet International Maritime Organization (IMO) emission targets by delivering stable near-zero-emission operation while achieving high hydrogen efficiency and grid stability with minimal computational cost. Consequently the proposed system presents a realistic certifiable and regionally optimized roadmap for next-generation hybrid PEMFC–battery–renewable marine power systems in Saudi Arabian coastal operations.

Green hydrogen is essential for advancing the energy transition as it is regarded as a CO2-neutral flexible and storable energy carrier. Particularly in steel production which is known for its high energy intensity hydrogen has great potential to replace conventional energy sources. In a game-theoretic bi-level optimization model involving a power plant operator and a steel company we investigate in which situations the production and use of green hydrogen is advantageous from an economic and ecological point of view. Through an extensive case study based on a realworld scenario we can observe that hydrogen production can serve as a profitable and flexible secondary income opportunity for the power plant operator and help avoid curtailment and spot market losses. On the other hand the steel manufacturer can reduce CO2 emissions and associated costs while also meeting the growing customer demand for low-carbon products. However our findings also highlight important trade-offs and uncertainties. While lower electricity generation costs or improved electrolyzer efficiency enhance hydrogen’s competitiveness increases in coal and CO2 emission prices do not always result in greater hydrogen adoption. This is due to the persistent reliance on a non-replaceable share of coal in steel production which raises the overall cost of both low-carbon and carbon-intensive steel. The model further shows that consumer demand elasticity plays a critical role in determining hydrogen uptake. These insights underscore the importance of not only reducing hydrogen costs but also designing supportive policies that address market acceptance and the full cost structure of green industrial products.

Modern ports are pivotal to global trade facing increasing pressures from operational demands resource optimization complexities and urgent decarbonization needs. This study highlights the critical importance of digital model adoption within the maritime industry particularly in the port sector while integrating sustainability principles. Despite a growing body of research on digital models industrial simulation and green transition a specific gap persists regarding the intersection of port management hydrogen energy integration and Digital Twin (DT) applications. Specifically a bibliometric analysis provides an overview of the current research landscape through a study of the most used keywords while the document analysis highlights three primary areas of advancement: optimization of hydrogen storage and integrated energy systems hydrogen use in propulsion and auxiliary engines and DT for management and validation in maritime operations. The main outcome of this research work is that while significant individual advancements have been made across critical domains such as optimizing hydrogen systems enhancing engine performance and developing robust DT applications for smart ports a major challenge persists due to the limited simultaneous and integrated exploration of them. This gap notably limits the realization of their full combined benefits for green ports. By mapping current research and proposing interdisciplinary directions this work contributes to the scientific debate on future port development underscoring the need for integrated approaches that simultaneously address technological environmental and operational dimensions.

This study investigates the combustion process in a marine spark-ignition engine fueled with an ammonia–hydrogen blend (15% hydrogen by volume) using a passive pre-chamber. A 3D-CFD model supported by a 1D engine model was employed to analyze equivalence ratios between 0.7 and 0.9 and pre-chamber nozzle diameters from 7 to 3 mm. Results indicate that combustion is consistently initiated by turbulent jets but at an equivalence ratio of 0.7 the charge combustion is incomplete. For lean mixtures reducing nozzle size improves flame propagation although not sufficiently to ensure stable operation. At an equivalence ratio of 0.8 reducing the nozzle diameter from 7 to 5 mm advances CA50 by about 6 CAD while further reduction causes minor variations. At richer conditions nozzle diameter plays a negligible role. Optimal performance was achieved with a 7 mm nozzle at equivalence ratio 0.8 delivering about 43% efficiency and 1.17 MW per cylinder.

The hydrogen energy industry is rapidly developing positioning hydrogen refueling stations (HRSs) as critical infrastructure for hydrogen fuel cell vehicles. Within these stations hydrogen compressors serve as the core equipment whose performance and reliability directly determine the overall system’s economy and safety. This article systematically reviews the working principles structural features and application status of mechanical hydrogen compressors with a focus on three prominent types based on reciprocating motion principles: the diaphragm compressor the hydraulically driven piston compressor and the ionic liquid compressor. The study provides a detailed analysis of performance bottlenecks material challenges thermal management issues and volumetric efficiency loss mechanisms for each compressor type. Furthermore it summarizes recent technical optimizations and innovations. Finally the paper identifies current research gaps particularly in reliability hydrogen embrittlement and intelligent control under high-temperature and high-pressure conditions. It also proposes future technology development pathways and standardization recommendations aiming to serve as a reference for further R&D and the industrialization of hydrogen compression technology.

Fuel cells are highly efficient electrochemical devices that convert the chemical energy of fuel directly into electrical energy while generating minimal pollutant emissions. In recent decades they have established themselves as a key technology for sustainable energy supply in the transport sector stationary systems and portable applications. In order to assess their real contribution to environmental protection and energy efficiency a comprehensive analysis of their life cycle Life Cycle Assessment (LCA) is necessary covering all stages from the extraction of raw materials and the production of components through operation and maintenance to decommissioning and recycling. Particular attention is paid to the environmental challenges associated with the extraction of platinum catalysts the production of membranes and waste management. Economic aspects such as capital costs the price of hydrogen and maintenance costs also have a significant impact on their widespread implementation. This manuscript presents detailed mathematical models that describe the electrochemical characteristics energy and mass balances degradation dynamics and cost structures over the life cycle of fuel cells. The models focus on proton exchange membrane fuel cells (PEMFCs) with possible extensions to other types. LCA is applied to quantify environmental impacts such as global warming potential (GWP) while the levelized cost of electricity (LCOE) is used to assess economic viability. Particular attention is paid to the sustainability challenges of platinum catalyst extraction membrane production and end-of-life material recovery. By integrating technical environmental and economic modeling the paper provides a systematic perspective for optimizing fuel cell deployment within a circular economy.

This experimental study examines the effect of adding a hydrogen-enriched synthetic gaseous mixture (HGM’) on the combustion and fuel conversion efficiency of a singlecylinder research engine (SCRE). The work assesses the viability of using this mixture as a supplemental fuel for flex-fuel engines operating under urban driving cycling conditions. An SCRE the AVL 5405 model was employed operating with ethanol and gasoline as primary fuels through direct injection (DI) and a volumetric compression ratio of 11.5:1. The HGM’ was added in the engine’s intake via fumigation (FS) with volumetric proportions ranging from 5% to 20%. The tests were executed at 1900 rpm and 2500 rpm engine speeds with indicated mean effective pressures (IMEPs) of 3 and 5 bar. When HGM’s 5% v/v was applied at 2500 rpm the mean indicated effective pressure of 3 bar was observed. A decrease of 21% and 16.5% in the ISFC was observed when using gasoline and ethanol as primary fuels respectively. The usage of an HGM’ combined with gasoline or ethanol proved to be a relevant and economically accessible strategy in the improvement of the conversion efficiency of combustion fuels once this gaseous mixture could be obtained through the vapor-catalytic reforming of ethanol giving up the use of turbochargers or lean and ultra-lean burn strategies. These results demonstrated the potential of using HGM’ as an effective alternative to increase the efficiency of flex-fuel engines.

Achieving global decarbonization is essential to mitigate climate change yet heat-intensive industries remain challenging to decarbonize through electrification alone. Green hydrogen offers a clean alternative to replace fossil fuels and fossil fuel–based hydrogen but its deployment requires careful planning and robust economic assessment. This study addresses the optimal design of a green hydrogen supply chain in a Mediterranean region where ceramics and cement dominate as energy-intensive industries while oil refining is the main consumer of fossil fuel–based hydrogen. The region also faces freshwater scarcity due to its climate and the high demand for water from tourism and agriculture. A Mixed-Integer Linear Programming (MILP) model is developed to minimize the total cost of supplying green hydrogen by determining the optimal size and location of renewable energy sources integrating desalinated seawater from existing desalination plants as feedstock and designing the infrastructure connecting production storage and demand centers. The cost-optimal configuration includes 3.4 GW of PEM electrolyzers requiring 41.1 m3 /h of desalinated seawater supplied by existing desalination plants along with 5.1 GW of wind and 12 GW of solar power as renewable energy sources for large-scale hydrogen production. Results show that supplying green hydrogen to these industries can avoid approximately 4.4 million tons of CO2 emissions annually achieving a levelized cost of hydrogen (LCOH) of $2.18/kg for the period 2030–2050. Beyond this case study the proposed framework provides a replicable methodology for planning hydrogen-based energy systems in regions facing similar water and decarbonization challenges.

The thermal protection of rocket engine combustion chambers presents a critical challenge in supersonic flight applications. This study numerically investigates the enhancement of heat transfer and coolant flow characteristics in regenerative cooling channels through cylindrical rib integration employing ANSYS Fluent with SST k-ω turbulence modeling to evaluate single- and double-row configurations (0.75–1.25 mm diameter) under supercritical hydrogen conditions (3 MPa 300 K inlet). Results demonstrate that rib-induced turbulence disrupts thermal boundary layers with a 1.25 mm single-row design achieving a 13.67 % reduction in peak wall temperature compared to smooth channels while double-row arrangements show diminishing returns due to increased flow resistance. The thermal performance factor (η = (Nu/Nu₀)/(f/f₀) 1/3) reveals Case 3′s superiority (21.88 % improvement over the smooth channel configuration) in balancing heat transfer enhancement against pressure drop penalties (9.23–20.93 % for single-row 8.26–18.7 % for double-row). Notably density-driven flow acceleration near heated walls mitigates pressure losses through localized viscosity reduction. Furthermore cylindrical ribs reduce thermal stratification by up to 30 % in single-row configurations with double-row designs providing additional temperature homogenization at the cost of increased flow resistance. These findings offer critical insights for optimizing rib-enhanced cooling systems in high-performance rocket engines achieving simultaneous thermal efficiency and hydraulic performance improvements.

This work investigates a biomass-driven multi-generation system designed for simultaneous power freshwater and hydrogen production addressing the interlinked energy-waterenvironment nexus. The configuration integrates Brayton supercritical carbon dioxide (SCO2) organic Rankine cycle (ORC) and thermoelectric generator (TEG) subsystems to maximize utilization of biomass-derived syngas. The recovered energy drives a reverse osmosis (RO) desalination unit for freshwater production and an alkaline electrolyzer for hydrogen generation followed by two-stage compression for storage. Under baseline conditions the system generates 1.99 MW of electricity 9.38 kg/h of hydrogen and 88.6 m3 /h of freshwater with an overall exergetic efficiency of 20.25 % emissions intensity of 0.85 kg/kWh and a payback period of 5.87 years. The Brayton cycle accounts for 49.3 % of the total cost rate while the gasifier exhibits the highest exergy destruction at 46 %. Sensitivity analyses show that varying biomass moisture content (10–30 %) and operating temperatures (700–900 ◦C) significantly influence system performance. Using a data-driven optimization framework that combines artificial neural networks (ANN) and a genetic algorithm (GA) the system’s exergetic efficiency improves to 21.76 % freshwater output rises to 90.96 m3 /h and emissions intensity decreases to 0.877 kg/kWh. Additionally optimization reduces the total cost rate by 2.71 % leading to a payback period of 5.4 years and enhances the system’s overall performance by 12.64 %.