Spain

The present study investigates the design and scale-up of a pure hydrogen oxy-fuel combustion burner for industrial applications. In recent years this technology has garnered attention as an effective approach to the decarbonisation of high-temperature industrial processes. Replacing air with oxygen in combustion processes significantly reduces nitrogen oxides emissions and leads to sustainable energy use. A laboratory-scale burner was designed with inlet nozzle dimensions adapted to the specific properties of hydrogen and oxygen as fuel and oxidant respectively. Implementing oxy-fuel combustion requires addressing several technical issues to prevent the burner wall from overheating and to ensure a stable flame. An infrared camera was used to characterise the performance and operating conditions of the laboratory-scale burner in the range of 2.5–30 kW. The 10 kW baseline case was analysed numerically and validated experimentally using thermocouples. This revealed stable lifted flames with maximum temperatures of 2800 K and a flame length of 0.15 m. A key challenge in engineering is transferring results from laboratory-scale to large-scale industrial applications. Once validated the prototype design was scaled up numerically from 10 kW to 1 MW investigating the feasibility of different scaling criteria. The impact of these criteria on flame characteristics mixing patterns and the volumetric distribution of the reaction zone was then assessed. The constant velocity criterion yielded the lowest pressure drops although it also resulted in longer flame lengths. In contrast the constant residence time criterion generated the highest pressure drops. The increased velocities associated with this criterion enhanced mixing leading to shorter flame lengths as noted in the cases of 200 kW decreasing from 0.98 m under constant velocity criterion to 0.46 m. The intermediate criteria demonstrated a feasible alternative for scaling up the burner by effectively balancing flame length mixing rate and pressure losses. Nevertheless all criteria enabled the burner to sustain high combustion efficiency. Overall this investigation provides valuable insight into the potential of hydrogen oxy-fuel combustion technology to reduce carbon emissions in high-temperature processes.

Hydrogen is a key energy carrier for decarbonizing multiple sectors particularly when produced via water electrolysis powered by renewable energy. Proton exchange membrane (PEM) electrolyzers are well suited for this application due to their ability to rapidly adjust to fluctuating power inputs. Despite being conventionally operated at high temperatures and pressures to reduce heating and compression needs recent studies suggest that under partial loads lower operating conditions may enhance efficiency. This study introduces a novel optimization framework for dynamically adjusting pressure and temperature in PEM electrolyzers. The model integrates an efficiency map within a Mixed-Integer Linear Programming (MILP) formulation and applies McCormick tightening to address nonlinearities. A one-week case study demonstrates operational cost reductions of up to 12.5 % through optimal control favoring lower temperatures and pressures at low current densities and higher temperatures near rated load while maintaining moderate pressures. The results show improved efficiency and reduced hydrogen crossover enhancing safety and enabling scalable application over extended time horizons. These insights are valuable for long-term planning and evaluation of hydrogen production and storage systems.

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.

Hydrogen production via water electrolysis and renewable electricity is expected to play a pivotal role as an energy carrier in the energy transition. This fuel emerges as the most environmentally sustainable energy vector for non-electric applications and is devoid of CO2 emissions. However an electrolyzer´s infrastructure relies on scarce and energyintensive metals such as platinum palladium iridium (PGM) silicon rare earth elements and silver. Under this context this paper explores the exergy cost i.e. the exergy destroyed to obtain one kW of hydrogen. We disaggregated it into non-renewable and renewable contributions to assess its renewability. We analyzed four types of electrolyzers alkaline water electrolysis (AWE) proton exchange membrane (PEM) solid oxide electrolysis cells (SOEC) and anion exchange membrane (AEM) in several exergy cost electricity scenarios based on different technologies namely hydro (HYD) wind (WIND) and solar photovoltaic (PV) as well as the different International Energy Agency projections up to 2050. Electricity sources account for the largest share of the exergy cost. Between 2025 and 2050 for each kW of hydrogen generated between 1.38 and 1.22 kW will be required for the SOEC-hydro combination while between 2.9 and 1.4 kW will be required for the PV-PEM combination. A Grassmann diagram describes how non-renewable and renewable exergy costs are split up between all processes. Although the hybridization between renewables and the electricity grid allows for stable hydrogen production there are higher non-renewable exergy costs from fossil fuel contributions to the grid. This paper highlights the importance of nonrenewable exergy cost in infrastructure which is required for hydrogen production via electrolysis and the necessity for cleaner production methods and material recycling to increase the renewability of this crucial fuel in the energy transition.

Brazil has emerged as one of the global leaders in adopting renewable energy standing out in the implementation of onshore wind energy and more recently in the development of future offshore wind energy projects. Onshore wind energy has experienced exponential growth in the last decade positioning Brazil as one of the countries with the largest installed capacity in the world by 2023 with 30 GW. Wind farms are mainly concentrated in the northeast region where winds are constant and powerful enabling efficient and cost-competitive generation. Although in its early stages offshore wind energy presents significant potential of 1228 GW due to Brazil’s extensive coastline which exceeds 7000 km. Offshore wind projects promise greater generating capacity and stability as offshore winds are more constant than onshore winds. However their development faces challenges such as high initial costs environmental impacts on marine ecosystems and the need for specialized infrastructure. From a sustainability perspective this article discusses that both types of wind energy are key to Brazil’s energy transition. They reduce dependence on fossil fuels generate green jobs and foster technological innovation. However it is crucial to implement policies that foster synergy with green hydrogen production and minimize socio-environmental impacts such as impacts on local communities and biodiversity. Finally the article concludes that by 2050 Brazil is expected to consolidate its leadership in renewable energy by integrating advanced technologies such as larger more efficient turbines energy storage systems and green hydrogen production. The combination of onshore and offshore wind energy and other renewable sources could position the country as a global model for a clean sustainable and resilient energy mix.

Dark fermentation (DF) has gained increasing interest over the past two decades as a sustainable route for biohydrogen production; however understanding how reproducible the process can be both from macro- and microbiological perspectives remains limited. This study assessed the reproducibility of a parallel continuous DF system using fruit-vegetable waste as a substrate under strictly controlled operational conditions. Three stirred-tank reactors were operated in parallel for 90 days monitoring key process performance indicators. In addition to baseline operation different process enhancement strategies were tested including bioaugmentation supplementation with nutrients and/or additional fermentable carbohydrates and modification of key operational parameters such as pH and hydraulic retention time all widely used in the field to improve DF performance. Microbial community structure was also analyzed to evaluate its reproducibility and potential relationship with process performance and metabolic patterns. Under these conditions key performance indicators and core microbial features were reproducible to a large extent yet full consistency across reactors was not achieved. During operation unforeseen operational issues such as feed line clogging pH control failures and mixing interruptions were encountered. Despite these disturbances the system maintained an average hydrogen productivity of 3.2 NL H2/L-d with peak values exceeding 6 NL H2/L-d under optimal conditions. The dominant microbial core included Bacteroides Lactobacillus Veillonella Enterococcus Eubacterium and Clostridium though their relative abundances varied notably over time and between reactors. An inverse correlation was observed between lactate concentration in the fermentation broth and the amount of hydrogen produced suggesting it can serve as a precursor for hydrogen. Overall the findings presented here demonstrate that DF processes can be resilient and broadly reproducible. However they also emphasize the sensitivity of these processes to operational disturbances and microbial shifts. This underscores the necessity for refined control strategies and further systematic research to translate these insights into stable high-performance real-world systems.

The transition towards a low-carbon energy system remains a critical challenge for regions heavily dependent on fossil fuels such as Andalusia. This study proposes an energy planning framework based on the Low Emissions Analysis Platform (LEAP) to model alternative scenarios and assess the feasibility of meeting the 2030 and 2050 decarbonisation targets. Three scenarios are evaluated the Tendential Scenario (TS01) the Efficient Scenario (ES01) and the Efficient UJA (EEUJA) Scenario with this last being specifically designed to ensure full compliance with regional energy goals. The results indicate that while the Tendential Scenario falls short in reducing primary energy consumption and greenhouse gas (GHG) emissions the Efficient Scenario achieves significant progress though it is still insufficient to meet renewable energy integration targets. The proposed EEUJA Scenario introduces more ambitious measures including large-scale electrification smart grids energy storage and green hydrogen deployment resulting in a 39.5% reduction in primary energy demand by 2030 and 97% renewable energy penetration by 2050. Furthermore by implementing sector-specific decarbonisation strategies for the industry transport residential and services sectors Andalusia could position itself as a frontrunner in the energy transition while minimising economic and environmental risks. These findings underscore the importance of policy enforcement technological innovation and financial incentives in securing a sustainable energy future. The methodology developed in this study is replicable for other regions aiming for carbon neutrality and energy resilience through strategic planning and scenario analysis.

This article presents an innovative approach to address the optimization and planning of hydrogen network transmission focusing on minimizing computational and operational costs including capital operational and maintenance expenses. The mathematical models developed for gas flow rate pipelines junctions and storage form the basis for the optimization problem which aims to reduce costs while satisfying equality inequality and binary constraints. To achieve this we implement a dynamic algorithm incorporating 100 scenarios to account for uncertainty. Unlike conventional successive linear programming methods our approach solves successive piecewise problems and allows comparisons with other techniques including stochastic and deterministic methods. Our method significantly reduces computational time (56 iterations) compared to deterministic (92 iterations) and stochastic (77 iterations) methods. The non-convex nature of the model necessitates careful selection of starting points to avoid local optimal solutions which is addressed by transforming the primal problem into a linear program by fixing the integer variable. The LP problem is then efficiently solved using the Complex Linear Programming Expert (CPLEX) solver enhanced by Monte Carlo simulations for 100 scenarios achieving a 39.13% reduction in computational time. In addition to computational efficiency this approach leads to operational cost savings of 25.02% by optimizing the selection of compressors (42.8571% decreased) and storage facilities. The model’s practicality is validated through realworld simulations on the Belgian gas network demonstrating its potential in solving large-scale hydrogen network transmission planning and optimization challenges.

Hydrogen internal combustion engines (ICEs) have gained significant attention as a promising solution for achieving zero-carbon emissions in the transportation sector. This study investigates the conversion of a 2 L Diesel ICE into a lean hydrogen-powered ICE focusing on key challenges such as hydrogen mixing pre-ignition combustion flame development and NOx emissions. The novelty of this research lies in the specific modifications made to optimize engine performance and reduce emissions while utilizing the existing Diesel engine infrastructure. The study identifies several important design changes for the successful conversion of a Diesel engine to hydrogen including the following: Intake port design: transitioning from a swirl to a tumble design to enhance hydrogen mixing; Injection and spark plug configuration: using a lateral injection system combined with a central spark plug to improve combustion; Piston design: employing a lenticular piston shape with adaptable depth to enhance mixing; Mitigating Coanda effect: preventing hydrogen issues at the spark plug using deflectors or caps; and Head design: maintaining a flat head design for efficient mixing while ensuring adequate cooling to avoid pre-ignition. These findings highlight the importance of specific modifications for converting Diesel engines to hydrogen providing a solid foundation for further research in hydrogen-powered ICEs which could contribute to carbon emission reduction and a more sustainable energy transition.

The study of the electrochemical catalyst conversion of renewable electricity and carbon oxides into chemical fuels attracts a great deal of attention by different researchers. The main role of this process is in mitigating the worldwide energy crisis through a closed technological carbon cycle where chemical fuels such as hydrogen are stored and reconverted to electricity via electrochemical reaction processes in fuel cells. The scientific community focuses its efforts on the development of high-performance polymeric membranes together with nanomaterials with high catalytic activity and stability in order to reduce the platinum group metal applied as a cathode to build stacks of proton exchange membrane fuel cells (PEMFCs) to work at low and moderate temperatures. The design of new conductive membranes and nanoparticles (NPs) whose morphology directly affects their catalytic properties is of utmost importance. Nanoparticle morphologies like cubes octahedrons icosahedrons bipyramids plates and polyhedrons among others are widely studied for catalysis applications. The recent progress around the high catalytic activity has focused on the stabilizing agents and their potential impact on nanomaterial synthesis to induce changes in the morphology of NPs.