Saudi Arabia

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.

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 %.

The rock wettability is one of the most critical parameters that influences rock storage potential trapping and H2 withdrawal rate during Underground hydrogen storage (UHS). However the existing review articles on wettability of H2-brine-rock systems do not provide detailed information on complexities introduced by reservoir wettability influencing parameters such as high pressure temperature salinity conditions micro-biotic effects cushion gases and organic acids relevant to subsurface environments. Therefore a comprehensive review of existing research on various parameters influencing rock wettability during UHS and residual trapping of H2 was conducted in this study. Literature that provides insight into molecular-level interaction through machine learning and molecular dynamic (MD) simulations and role of surface-active chemicals such as nanoparticles surfactants and wastewater chemicals were also reviewed. The review suggested that UHS could be feasible in clean geo-storage formations but the presence of rock surface contaminants at higher storage depth and microbial effects should be accounted for to prevent over-estimation of the rock storage potentials. The H2 wettability of storage/caprocks and associated risks of UHS projects could be higher in rocks with high proportion of carbonate minerals organic-rich shale and basalt with high plagioclase minerals content. However treatment of rock surfaces with nanofluids surfactants methylene blue and methyl orange has proven to alter the rock wettability from H2-wet towards water-wet. Research results on effect of rock wettability on residually trapped hydrogen and snap-off effects during UHS are contradictory thus further studies would be required in this area. The review generally concludes that rock wettability plays prominent role on H2 storage due to the frequency and cyclic loading of UHS hence it is vital to evaluate the effects of all possible wettability influencing parameters for successful designs and implementation of UHS projects.

Blue hydrogen technology generated from natural gas through carbon capture and storage (CCS) technology is a promising solution to mitigate greenhouse gas emissions and meet the growing demand for clean energy. To improve the sustainability of blue hydrogen it is crucial to explore alternative feedstocks production methods and improve the efficiency and economics of carbon capture storage and utilization strategies. Two established technologies for hydrogen synthesis are Steam Methane Reforming (SMR) and Autothermal Reforming (ATR). The choice between SMR and ATR depends on project specifics including the infrastructure energy availability environmental goals and economic considerations. ATR-based facilities typically generate hydrogen at a lower cost than SMR-based facilities except in cases where electricity prices are elevated or the facility has reduced capacity. Both SMR and ATR are methods used for hydrogen production from methane but ATR offers an advantage in minimizing CO2 emissions per unit of hydrogen generated due to its enhanced energy efficiency and unique process characteristics. ATR provides enhanced utility and flexibility regarding energy sources due to its autothermal characteristics potentially facilitating integration with renewable energy sources. However SMR is easier to run but may lack flexibility compared to ATR necessitating meticulous management. Capital expenditures for SMR and ATR hydrogen reactors are similar at the lower end of the capacity spectrum but when plant capacity exceeds this threshold the capital costs of SMR-based hydrogen production surpass those of ATR-based facilities. The less profitably scaled-up SMR relative to the ATR reactor contributes to the cost disparity. Additionally individual train capacity constraints for SMR CO2 removal units and PSA units increase the expenses of the SMR-based hydrogen facility significantly.

Hydrogen’s increasing potential as an alternative fuel for heavy-duty transport has led to the conversion of conventional diesel compression-ignition engines to spark-ignition hydrogen operation. Hydrogen’s broad flammability range enables leaner operation achieving both higher engine efficiency and near-zero emissions. In particular direct injection hydrogen combustion improves volumetric efficiency and reduces problems including pre-ignition and knock related to hydrogen port-fuel injection. In the present work we performed an optical investigation of direct injection (DI) hydrogen combustion under leaner mixture conditions. The study was conducted using a heavy-duty optical diesel engine modified for spark-ignition operation. Bottom-view natural flame luminosity and OH-PLIF imaging were conducted along with in-cylinder pressure measurements. Experiments were conducted at three air-excess ratios (3 3.4 and 3.8) with spark timings (ST) varied from − 15 ◦CA aTDC to − 30 ◦CA aTDC. Hydrogen injection ended at − 30 ◦CA aTDC with the start of injection adjusted accordingly to achieve the desired lambda conditions. The maximum IMEPg corresponded to the lowest COV of the IMEPg indicating optimal spark timing for lean DI hydrogen combustion. The optimized spark timing for λ = 3 λ = 3.4 and λ = 3.8 were occurred at − 25 ◦CA aTDC − 25 ◦CA aTDC and − 30 ◦CA aTDC respectively. The corresponding COV of IMEPg values were below 5 % indicating stable combustion. The flame kernel first initiates at the spark plug and then propagates toward the piston’s outer boundary however the flame propagation does not remain as a continuous front unlike port-fuel injected hydrogen combustion. The effect of fuel stratification is evident in combustion luminosity and OH-PLIF images showing pockets of varying intensity within the combustion chamber. Natural flame luminosity images reveal incomplete flame coverage and asymmetric combustion emphasizing the need for metal engine experiments to further quantify the unburned hydrogen and associated combustion losses.

Global renewable hydrogen trade is expected to play a key role in decarbonizing future energy systems. Yet hydrogen exporters may deviate from perfectly competitive behaviour to influence prices similarly to the existing fossil fuel market with important implications for consumer welfare and the pace of the energy transition. This study develops a global renewable hydrogen trade model that captures potential strategic interactions among exporters using a Stackelberg game-theoretic framework. The model is formulated as an Equilibrium Problem with Equilibrium Constraints (EPEC) and solved under three alternative equilibria: a profitmaximizing Nash equilibrium a cost-minimizing Nash equilibrium and a welfare-maximizing benchmark representing perfect competition. Results indicate that producers may strategically reduce their export quantities by up to 40 % relative to perfect competition to maximize profits. Such behaviour raises prices to a minimum of 4.5 USD/kg in 2050 across major import markets thereby significantly eroding consumer surplus. Strategic behaviour of dominant exporters also shifts trade flows reshaping the global allocation of hydrogen supply. Sensitivity analysis further reveals that financing costs play a key role in shaping strategic producers’ behaviour with lower financing costs helping to reduce prices and stimulate demand. These findings highlight the implications of imperfect competition in global hydrogen trade and suggest that policy measures may be needed to mitigate potential negative consequences.

This study considers the use of an enhanced super-twisting sliding mode control (STSMC) scheme via the incorporation of a hybrid extended state observer (ESO) and a higher order sliding mode observer (HOSMO) state estimation and disturbance observer (DO) based on exponential decay embedded via a tracking element in order to hasten the estimation of disturbance thus improving performance significantly. This scheme is employed to generate single and multiple control signals per agent based on the microgrid’s presented components such as energy storage devices and renewable energy sources (RESs) alongside the harness of a puma optimizer (PO) metaheuristics scheme to optimize each area regulator’s performance. The sliding surface incorporated is chosen based on desired control objectives. Adjusting the constricted area frequency and reducing tie-line power transfer fluctuations are considered the primary goals for frequency regulation in a multi-area power system. Also based on the presented simulations adequate performance in terms of minimum chattering low complexity fast convergence and adequate robustness has been achieved. Using various microgrid peripheral components such as a multi-terminal soft open point (SOP) with a dedicated terminal for hydrogen energy storage alongside the proposed enhanced STSMC the frequency change and power transfer rate of change are maintained within the range of ×10−6 values substantially preserving proper performance compared to other simulated scenarios. In regard to the final simulated case involving SOP the following has been achieved: steady state errors of 2.538×10−6 Hz for ΔF1 3.125×10−6 Hz for ΔF2 and 1.920×10−6 p.u for ΔPtie alongside peak disturbance overshoot reduction in comparison to stochastic case of 99.580% 99.605% and 99.771% for same mentioned elements respectively. Also a reduction in peak disturbance undershoot of 95.589% 99.547% and 99.573% respectively has been achieved. Thus the enhanced STSMC can effectively mitigate frequency fluctuations and tie-line power transfer abnormalities.