United Arab Emirates

Optimal design and performance analysis of renewable energy system to serve the cruise ship main and auxiliary power in Stockholm Sweden is presented in this paper. The goal is to integrate renewable energy systems in small and large ships for greener and sustainable marine transport. The power load for the cruise ship was determined and modeling and simulation analysis was used to investigate the daily and annual performance of the power system architectures including the efficiency and capacity factors of the energy conversion systems. The total electrical power generated from the solar PV PEM fuel cell and Diesel generator; the cost of electricity; and the greenhouse gas and particulate matter PM emissions were determined. The proposed renewable energy system offers a good penetration of renewable energy system (13.83%) and greenhouse gas and particulate emissions reduction (9.84% emissions reduction compared to baseline system using Diesel engines). The integration of renewable and clean power systems such as solar PV and PEM fuel cell (high electrical efficiency) is very attractive solution for onboard ship power generation. They are economically viable (reduce the cost of Diesel fuel) cleaner than the conventional gas turbine and internal combustion engines and reduce the dependency on fossil fuel.

This paper presents a novel energy management strategy (EMS) to control a wind-hydrogen microgrid which includes a wind turbine paired with a hydrogen-based energy storage system (HESS) i.e. hydrogen production storage and re-electrification facilities and a local load. This complies with the mini-grid use case as per the IEA-HIA Task 24 Final Report where three different use cases and configurations of wind farms paired with HESS are proposed in order to promote the integration of wind energy into the grid. Hydrogen production surpluses by wind generation are stored and used to provide a demand-side management solution for energy supply to the local and contractual loads both in the grid-islanded and connected modes with corresponding different control objectives. The EMS is based on a hierarchical model predictive control (MPC) in which long-term and short-term operations are addressed. The long-term operations are managed by a high-level MPC in which power production by wind generation and load demand forecasts are considered in combination with day-ahead market participation. Accordingly the hydrogen production and re-electrification are scheduled so as to jointly track the load demand maximize the revenue through electricity market participation and minimize the HESS operating costs. Instead the management of the short-term operations is entrusted to a low-level MPC which compensates for any deviations of the actual conditions from the forecasts and refines the power production so as to address the real-time market participation and the short time-scale equipment dynamics and constraints. Both levels also take into account operation requirements and devices’ operating ranges through appropriate constraints. The mathematical modeling relies on the mixed-logic dynamic (MLD) framework so that the various logic states and corresponding continuous dynamics of the HESS are considered. This results in a mixed-integer linear program which is solved numerically. The effectiveness of the controller is analyzed by simulations which are carried out using wind forecasts and spot prices of a wind farm in center-south of Italy.

The commercialization of hydrogen as a fuel faces severe technological economic and environmental challenges. As a method to overcome these challenges microalgal biohydrogen production has become the subject of growing research interest. Microalgal biohydrogen can be produced through different metabolic routes the economic considerations of which are largely missing from recent reviews. Thus this review briefly explains the techniques and economics associated with enhancing microalgae-based biohydrogen production. The cost of producing biohydrogen has been estimated to be between $10 GJ-1 and $20 GJ−1 which is not competitive with gasoline ($0.33 GJ−1 ). Even though direct biophotolysis has a sunlight conversion efficiency of over 80% its productivity is sensitive to oxygen and sunlight availability. While the electrochemical processes produce the highest biohydrogen (>90%) fermentation and photobiological processes are more environmentally sustainable. Studies have revealed that the cost of producing biohydrogen is quite high ranging between $2.13 kg−1 and 7.24 kg−1 via direct biophotolysis $1.42kg−1 through indirect biophotolysis and between $7.54 kg−1 and 7.61 kg−1 via fermentation. Therefore low-cost hydrogen production technologies need to be developed to ensure long-term sustainability which requires the optimization of critical experimental parameters microalgal metabolic engineering and genetic modification.

Green hydrogen stands as a promising clean energy carrier with potential net-zero greenhouse gas emissions. However different system-level configurations for green hydrogen production yield different levels of efficiency cost and maturity necessitating a comprehensive assessment. This review evaluates the components of hydrogen production plants from technical and economic perspectives. The study examines six renewable energy sources—solar photovoltaics solar thermal wind biomass hydro and geothermal—alongside three types of electrolyzers (alkaline proton exchange membrane and solid oxide electrolyzer cells) and five hydrogen storage methods (compressed hydrogen liquid hydrogen metal hydrides ammonia and liquid organic hydrogen carriers). A comprehensive assessment of 90 potential system configurations is conducted across five key performance indicators: the overall system cost efficiency emissions production scale and technological maturity. The most cost-effective configurations involve solar photovoltaics or wind turbines combined with alkaline electrolyzers and compressed hydrogen storage. For enhanced system efficiency geothermal sources or biomass paired with solid oxide electrolyzer cells utilizing waste heat show significant promise. The top technologically mature systems feature combinations of solar photovoltaics wind turbines geothermal or hydroelectric power with alkaline electrolyzers using compressed hydrogen or ammonia storage. The highest hydrogen production scales are observed in systems with solar PV wind or hydro power paired with alkaline or PEM electrolyzers and ammonia storage. Configurations using hydro geothermal wind or solar thermal energy sources paired with alkaline electrolyzers and compressed hydrogen or liquid organic hydrogen carriers yield the lowest life cycle GHG emissions. These insights provide valuable decision-making tools for researchers business developers and policymakers guiding the optimization of system efficiency and the reduction of system costs.

Hydrogen and methane as secondary fuels in diesel engines can be promising solutions to meet energy demand. The current study investigated the effect of the specialty gases of different compositions on diesel engine performance and exhaust gases. Four gases with various compositions of exhaust gas recirculation (Carbon monoxide Carbon dioxide and Nitrogen) and fuels (Hydrogen and Methane) were used at various mass flow rates of 10 20 and 25 LPM (liter per minute) and various engine speeds of 2000 2500 3000 and 3500 rpm (revolutions per minute). The procured results revealed that adding specialty gases improved brake thermal efficiency and power. Similarly the brake-specific fuel consumption was also massively retarded compared to diesel due to the influence of the hydrogen and methane composition. However the fuel with the higher nitrogen reported less BTE (brake thermal efficiency) and comparatively higher exhaust gas temperature owing to the higher presence of nitrogen in their composition. Regarding emissions including exhaust gas recirculation dropped the formation of pollutants efficiently compared to diesel. Among various fuels Case 1 (30 % H2 5 % CH4 5 CO2 and 60 % CO) reported the lowest emission of NOx and Case 2 (25 % H2 5 % CH4 5 CO2 30 % CO and 35 % N2) of CO and CO2 emissions. Generally specialty gases with a variable composition of exhaust gas recirculation gases can be a promising sustainable replacement for existing fossil fuels.

Hydrogen is increasingly recognized as a key energy vector for achieving deep decarbonization across urban and industrial sectors. Supporting global efforts to reduce greenhouse gas (GHG) emissions and achieve the Sustainable Development Goals (SDGs) it is essential to understand the multi-sectoral role of the hydrogen value chain spanning production storage and end-use applications with particular emphasis on smart city systems and industrial processes. Green hydrogen production technologies including alkaline water electrolysis (AWE) proton exchange membrane (PEM) electrolysis anion exchange membrane (AEM) electrolysis and solid oxide electrolysis cells (SOECs) are evaluated in terms of efficiency scalability and integration potential. Storage pathways are examined across physical storage (compressed gas cryo-compressed and liquid hydrogen) material-based storage (solid-state absorption in metal hydrides and chemical carriers such as LOHCs and ammonia) and geological storage (salt caverns depleted gas reservoirs and deep saline aquifers) highlighting their suitability for urban and industrial contexts. In the smart city domain hydrogen is analyzed as an enabler of zero-emission transportation low-carbon residential and commercial heating and renewable-integrated smart grids with long-duration storage capabilities. System-level studies demonstrate that coordinated integration of these applications can deliver higher overall energy efficiency deeper reductions in life-cycle GHG emissions and improved resilience of urban energy systems compared with sector-specific approaches. Policy frameworks safety standards and digitalization strategies are reviewed to illustrate how hydrogen infrastructure can be embedded into interconnected urban energy systems. Furthermore industrial applications focus on hydrogen’s potential to decarbonize energy-intensive processes and enable sector coupling between electricity heat and manufacturing. The environmental implications of hydrogen deployment are also considered including resource efficiency life-cycle emissions and ecosystem impacts. In contrast to reviews addressing isolated aspects of hydrogen technologies this study synthesizes technological infrastructural and policy dimensions integrating insights from over 400 studies to highlight the multifaceted role of hydrogen in sustainable urban development and industrial decarbonization and the added benefits achievable through coordinated cross-sector deployment strategies.

While hydrogen production through pure water splitting remains a key focus in solar hydrogen research photocatalytic seawater splitting presents a more sustainable alternative better aligned with global development goals amid increasing freshwater scarcity. Nevertheless the deactivation of the photocatalyst by the corrosion of various ions present in seawater as well as the chloride ions’ redox side reaction limits the practical use of the photocatalytic seawater splitting process. In this context sulfur has emerged as a crucial component in photocatalytic composites for seawater splitting owing to its unique chemical properties. It acts as a chlorine-repulsive agent effectively suppressing chloride ion oxidation which mitigates corrosion enhances structural stability and significantly improves overall photocatalytic performance in saline environments. This review offers a thorough explanation of the basic ideas of solar-driven seawater splitting delves into various synthesis strategies and explores recent advancements in sulfur-based composites for efficient hydrogen generation using seawater. Optimizing synthesis techniques and incorporating strategies like doping cocatalyst and heterojunctions significantly enhance the performance of sulfur-based photocatalysts for seawater splitting. Future advances include integrating AI-guided material discovery sustainable use of industrial sulfur waste and precise control of sacrificial agents to ensure long-term efficiency and stability.

Underground hydrogen storage (UHS) represents a large-scale energy storage system aiming to ensure a consistent supply by storing hydrogen generated from surplus energy. In the practice of UHS cushion gas is typically injected into the formation to maintain reservoir pressure for efficient hydrogen withdrawal. This paper reviews the impact of cushion gas on the performance of UHS from both experimental and numerical simulation perspectives. The thermophysical (e.g. density viscosity compressibility and solubility) and petrophysical (interfacial tension wettability and relative permeability) properties as well as the mixing and diffusion behavior of different cushion gases were compared. The corresponding impact of different cushion gases on plume migration and trapping potential is then discussed. Furthermore this review critically analyzes and explains the impact of various factors on the performance of UHS including the type of cushion gas the composition of cushion gas mixtures the volume of injected cushion gas and the effects of bio-methanation processes. The corresponding analysis specifically focuses on key performance indicators including H2 recovery factor formation pressure brine production and H2 outflow purity. Thus this review provides a comprehensive analysis of the role of cushion gas in UHS offering insight into the effective management and optimization of cushion gas injection in field-scale UHS operations.

As hydrogen gains prominence in energy systems its adoption as an energy source for fuel cell electric vehicles (FCEVs) necessitates the establishment of hydrogen refueling stations (HRS). These stations contain critical compo-nents including nozzles storage tanks heat exchangers and compressors which must be certified by regulatory agen-cies to ensure safety and public trust. Current certification processes are fragmented and manually intensive creating inefficiencies and limiting transparency across the infrastructure lifecycle. In this paper we propose a blockchain-based solution that creates a secure and auditable network for certifying key HRS components. The system integrates an EVM-compatible blockchain decentralized storage and a modular suite of smart contracts (SCs) that formalize registration bidding accreditation certification and governance. Each contract encodes a distinct actor-driven work-flow enabling traceable and role-specific operations. A Decentralized Application (DApp) interface supports real-time and role-based interaction across the ecosystem. We present and evaluate the SCs and their underlying algorithms us-ing gas usage analysis load testing and security auditing. Load testing across the certification lifecycle shows stable transaction throughput and predictable cost profiles under increasing actor activity. A static security analysis con-firms resilience against common vulnerabilities. Our cost analysis indicates that while the framework is technically deployable on public blockchains the execution costs of certain functions make it more cost-effective for private blockchains or Layer 2 networks. We also compare our framework with existing systems to highlight its novelty and technical advantages. Our SCs DApp interface and load testing scripts are publicly available on GitHub.