Applications & Pathways

Cruise ship decarbonisation was studied on a Mediterranean cruise profile. The analysis focused on ship energy flows fuel consumption carbon emissions ship CII and EEDI. A combination of technologies for reducing ship fuel consumption was simulated before introducing hydrogen fueled machinery for the ship. The studied technologies included ultrasound antifouling shore power battery hybrid machinery waste heat recovery and air lubrication. Their application on the selected operational profile led to combined fuel savings of 187%. When the same technologies were combined to a hydrogen machinery the ship total energy consumption compared to baseline was reduced by 25%. The cause of this was the synergies in the ship energy system such as ship auxiliary powers heat consumption and machinery efficiency. The proposed methodology of ship energy analysis is important step in starting to evaluate new fuels for ships and in preliminary technology screening prior to integrating them in the ship design.

The world is experiencing the effects of climate change at an increasing rate including rising average global temperature caused primarily by greenhouse gas (GHG) emissions. Energy-intensive industries (EIIs) are major contributors to greenhouse gas emissions. The pulp and paper industry (PPI) is among the top five most energyintensive industries and it accounts for approximately 6 % of global industrial energy use and 2 % of direct industrial CO2 emissions. Therefore it is important to decarbonize this industrial sector to achieve the climate policy goal of achieving net-zero emissions as per the Paris Agreement. This paper presents a comprehensive review of the decarbonization options also known as decarbonization pathways for the pulp and paper industrial sector. These pathways are selected from available literature and they mainly include energy efficiency measures (EEMs) paper recycling switching to carbon-neutral fuels such as biomass and hydrogen electrification of heat supply and carbon capture & storage (CCS) among other emerging technologies. After identifying each decarbonization pathway is discussed in detail with its drivers and barriers to implementation. The Analytical Hierarchy Process AHP a multi-criteria decision-making MCDM technique is carried out to rank the decarbonization pathways on five distinct criteria: cost emission reduction potential technological readiness level (TRL) implementation time and scalability. The ranking is carried out in four distinct criteria weight regimes to present clear choices on different criterion weights. This review paper aims to add to the existing literature to provide clear indications in choosing the pathways toward the decarbonization effort in the pulp & paper industry under various strategic priorities.

The main motivation for this paper was the lack of studies and comparative analyses on the new generation of alternative fuels in the marine sector such as methane methanol ammonia and hydrogen. Firstly a review of international legislation and the status of these new fuels was carried out highlighting the current situation and the different existing alternatives for reducing greenhouse gas (GHG) emissions. In addition the status and evolution of the current order book for ships since the beginning of this decade were used for this analysis. Secondly each fuel and its impact on the geometry and operation of the engine were evaluated in a theoretical engine called MW-1. Lastly an economic analysis of the current situation of each fuel and its availability in the sector was carried out in order to select using the indicated methodology the most viable fuel at present to replace traditional fuels with a view to the decarbonization set for 2050.

The burgeoning adoption of photovoltaic and wind energy has limitations of volatility and intermittency which hinder their application. Electro-hydrogen coupling energy storage systems emerge as a promising solution to address this issue. This technology combines renewable energy power generation with hydrogen production through water electrolysis and hydrogen fuel cell power generation effectively enabling the consumption and peak load management of renewable energy sources. This paper presents a power system with a 10 kW photovoltaic system and lithium battery energy storage system designed for hydrogen-electric coupled energy storage validated through the physical experiments. The results demonstrate the system's effectiveness in mitigating the impact of randomness and volatility in photovoltaic power generation. Moreover the energy management system can adjust bus power based on load demand. Testing the system in the absence of photovoltaic power generation reveals its capability to supply energy to the load for three hours with a minimum operating load power of 3 kW even under weather conditions unsuitable for photovoltaic power generation. These findings showed the potential of electro-hydrogen coupling energy storage systems in addressing the challenges associated with renewable energy integration paving the way for a reliable and sustainable energy supply.

Buildings are major energy consumers accounting for a significant portion of global energy consumption. Integrating hydrogen systems electrolyzers accumulation and fuel cells is proposed as a clean and efficient energy alternative to mitigate this impact and move toward a more sustainable future. This paper presents a systematic procedure for incorporating these technologies into buildings considering building engineers and stakeholders. First an in-depth analysis of buildings’ main energy consumption parameters is conducted identifying areas of energy need with the most significant optimization potential. Next a detailed review of the various opportunities for hydrogen applications in buildings is conducted evaluating their advantages and limitations. Performing a scientific review to find and understand the requirements of building engineers and the stakeholders has given notions of integration that emphasize the needs. As a result of the review process and identifying the needs to integrate hydrogen into buildings a flowchart is proposed to facilitate decision-making regarding integrating hydrogen systems into buildings. This flowchart is accompanied by a matrix of variables that considers the defined requirements allowing for combining the most suitable solution for each case. The results of this research contribute to advancing the adoption of hydrogen technologies in buildings thus promoting the transition to a more sustainable and resilient energy model.

This research presents a hierarchically synchronized Multi-Energy System (MES) designed for regional communities incorporating a network of small-scale Integrated Energy Microgrids (IEMs) to augment efficiency and collective advantages. The MES framework innovatively integrates energy complementarity pairing algorithms with efficient iterative optimization processes significantly curtailing operational expenditures for constituent microgrids and bolstering both community-wide benefits and individual microgrid autonomy. The MES encompasses electricity hydrogen and heat resources while leveraging controllable assets such as battery storage systems fuel cell combined heat and power units and electric vehicles. A comparative study of six IEMs demonstrates an operational cost reduction of up to 26.72% and a computation time decrease of approximately 97.13% compared to traditional methods like ADMM and IDAM. Moreover the system preserves data privacy by limiting data exchange to aggregated energy information thus minimizing direct communication between IEMs and the MES. This synergy of multi-energy complementarity iterative optimization and privacy-aware coordination underscores the potential of the proposed approach for scalable community-centered energy systems.

Electric arc furnace slag is a major by-product of steelmaking yet its industrial utilization remains limited due to its complex chemical and mineralogical composition. This study presents a hydrogen-based approach to recover metallic components from EAF slag for potential reuse in steelmaking. Laboratory experiments were conducted by melting 50 g of industrial slag samples at 1600 ◦C and injecting hydrogen gas through a ceramic tube into the liquid slag. After cooling both the slag and the metallic phases were analyzed for their chemical and phase compositions. Additionally the reduction process was modeled using a combination of approaches including the thermochemical software FactSage 8.1 models for density surface tension and viscosity as well as a diffusion model. The injection of hydrogen resulted in the reduction of up to 40% of the iron oxide content in the liquid slag. In addition the fraction of reacted hydrogen gas was calculated.

The turbocharging of hydrogen fuel cell systems (FCSs) has recently become a prominent research area aiming to improve FCS efficiency to help decarbonise the energy and transport sectors. This work compares the performance of an electrically assisted variable-geometry turbocharger (VGT) with a fixed-geometry turbocharger (FGT) by optimising both the sizing of the components and their operating points ensuring both designs are compared at their respective peak performance. A MATLAB-Simulink reducedorder model is used first to identify the most efficient components that match the fuel cell air path requirements. Maps representing the compressor and turbines are then evaluated in a 1D flow model to optimise cathode pressure and stoichiometry operating targets for net system efficiency using an accelerated genetic algorithm (A-GA). Good agreement was observed between the two models’ trends with a less than 10.5% difference between their normalised e-motor power across all operating points. Under optimised conditions the VGT showed a less than 0.25% increase in fuel cell system efficiency compared to the use of an FGT. However a sensitivity study demonstrates significantly lower sensitivity when operating at non-ideal flows and pressures for the VGT when compared to the FGT suggesting that VGTs may provide a higher level of tolerance under variable environmental conditions such as ambient temperature humidity and transient loading. Overall it is concluded that the efficiency benefits of VGT are marginal and therefore not necessarily significant enough to justify the additional cost and complexity that they introduce.

Liquid hydrogen (LH2) is a promising energy carrier to decrease the climate impact of aviation. However the inevitable formation of hydrogen boil-off gas (BOG) is a main drawback of LH2. As the venting of BOG reduces the overall efficiency and implies a safety risk at the airport means for capturing and re-using should be implemented. Metal hydrides (MHs) offer promising approaches for BOG recovery as they can directly absorb the BOG at ambient pressures and temperatures. Hence this study elaborates a design concept for such an MH-based BOG recovery system at hydrogen-ready airports. The conceptual design involves the following process steps: identify the requirements establish a functional structure determine working principles and combine the working principles to generate a promising solution.

Hydrogen is increasingly recognized as an element in the effort to decarbonize the energy sector. Within the development of large-scale supply chain the storage phase emerges as a significant challenge. This study reviews Life Cycle Assessment (LCA) literature focused exclusively on hydrogen as an energy vector aiming to identify areas for improvement highlight effective solutions and point out research gaps. The goal is to provide a comprehensive overview of hydrogen storage technologies from an environmental perspective. A systematic search was conducted in the SCOPUS database using a specific set of keywords resulting in the identification of 30 relevant studies. These works explore hydrogen storage across different scales and applications which were classified into five categories based on the type of storage application most of them related to stationary use. The majority of the selected studies focus on storing hydrogen in compressed gas tanks. Notably 33 % of the analyzed articles assess only greenhouse gas (GHG) emissions and 10 % evaluate only two environmental impact categories including GHGs. This reflects a limited understanding of broader environmental impacts with a predominant focus on CO₂eq emissions. When comparing different case studies storage methods associated with the lowest emissions include metal hydrides and underground hydrogen storage. Another important observation is the trend of decreasing CO₂eq emissions as the storage system scale increases. Future studies should adopt more comprehensive approaches by analyzing a wider range of hydrogen storage technologies and considering multiple environmental impact categories in LCA. Moreover it is crucial to integrate environmental economic and social dimensions of sustainability as multidimensional assessments are essential to support well-informed balanced decisions that align with the sustainable development of hydrogen storage systems.