Spain

Recently perovskite-type oxides have attracted researchers as new materials for solid hydrogen storage. This paper presents the performances of perovskite-type oxide LaCrO3 dedicated for hydrogen solid storage using both numerical and experimental methods. Ab initio calculations have been used here with the aim to investigate the electronic mechanical and elastic properties of LaCrO3Hx (x = 0 6) for hydrogen storage applications. Cell parameters crystal structures and mechanical properties are determined. Additionally the cohesive energy indicates the stability of the hydride. Furthermore the mechanical properties showed that both compounds (before and after hydrogenation) are stable. The microstructure and storage capacity at different temperatures of these compounds have been studied. We have shown that storage capacities are around 4 wt%. The properties obtained from this type of hydride showed that it can be used for future applications. XRD analysis was conducted in order to study the structural properties of the compound. Besides morphological thermogravimetric analysis was also conducted on the perovskite-type oxide. Finally a comparison of these materials with other hydrides used for hydrogen storage was carried out.

Prestressing steel wires are manufactured by cold drawing during which a preferential orientation is achieved in the matter of pearlitic colonies and lamellae. In addition to this general trend special (unconventional) pearlitic pseudocolonies evolve during the heavy-drawing manufacture process affecting the posterior macro- micro- and nano-structural integrity of the material. This paper discusses the important role of such a special microstructural unit (the pearlitic pseudocolony) in the fracture process in air (inert) environment in the presence of crack-like defects as well as in the case of environmentally assisted cracking (stress corrosion cracking by localized anodic dissolution) or hydrogen embrittlement. Results clearly demonstrate the key role of pearlitic pseudocolonies in promoting crack deflection (and thus mixed-mode propagation) after a global mode I cracking especially in the case of fracture in air and stress corrosion cracking.

Many countries have assigned an indispensable role for carbon capture and storage (CCS) in their national climate change mitigation pathways. However CCS deployment has stalled in most countries with only limited commercial projects realised mainly in hydrocarbon-rich countries for enhanced oil recovery. If the Paris Agreement is to be met then this progress must be replicated widely including hydrocarbon-limited countries. In this study we present a novel source-to-sink assessment methodology based on a hubs and clusters approach to identify favourable regions for CCS deployment and attract renewed public and political interest in viable deployment pathways. Here we apply this methodology to Spain where fifteen emission hubs from both the power and the hard-to-abate industrial sectors are identified as potential CO2 sources. A priority storage structure and two reserves for each hub are selected based on screening and ranking processes using a multi-criteria decision-making method. The priority source-to-sink clusters are identified indicating four potential development regions with the North-Western and North-Eastern Spain recognised as priority regions due to resilience provided by different types of CO2 sources and geological structures. Up to 68.7 Mt CO2 per year comprising around 21% of Spanish emissions can be connected to clusters linked to feasible storage. CCS especially in the hard-to-abate sector and in combination with other low-carbon energies (e.g. blue hydrogen and bioenergy) remains a significant and unavoidable contributor to the Paris Agreement’s mid-century net-zero target. This study shows that the hubs and clusters approach can facilitate CCS deployment in Spain and other hydrocarbon-limited countries.

In this paper we present the first systematic review of Power to X processes applied to the iron and steel industry. These processes convert renewable electricity into valuable chemicals through an electrolysis stage that produces the final product or a necessary intermediate. We have classified them in five categories (Power to Iron Power to Hydrogen Power to Syngas Power to Methane and Power to Methanol) to compare the results of the different studies published so far gathering specific energy consumption electrolysis power capacity CO2 emissions and technology readiness level. We also present for the first time novel concepts that integrate oxy-fuel ironmaking and Power to Gas. Lastly we round the review off with a summary of the most important research projects on the topic including relevant data on the largest pilot facilities (2–6 MW).

The energy transition's success hinges on the effectiveness to curbing carbon emissions from hard-to-abate sectors. Hydrogen (H2) has been proposed as the candidate vector that could be used to replace fossils in such energy-intensive industries. Despite green H2 via solar-powered water electrolysis being a reality today the overall defossilization of the hard-to-abate sectors by electrolytic H2 would be unfeasible as it relies on the availability of renewable electricity. In this sense the unbiassed photoelectrochemical water splitting (PEC) as inspired by natural photosynthesis may be a promising alternative expected in the long term. PEC could be partly or even completely decoupled from renewable electricity and then could produce H2 autonomously. However some remaining challenges still limit PEC water splitting to operate sustainably. These limitations need to be evaluated before the scaling up and implementation. A prospective life cycle assessment (LCA) has been used to elucidate a positive performance scenario in which the so-called super-green H2 or photo-H2 could be a sustainable alternative to electro-H2. The study has defined future scenarios by conducting a set of sensitivity assessments determining the figures of operating parameters such as i) the energy to produce the cell; ii) solar-to-hydrogen efficiency (STH); and iii) lifetime. These parameters have been evaluated based on two impact categories: i) Global Warming Potential (GWP); and ii) fossil Abiotic Depletion Potentials (fADP). The mature water electrolysis was used for benchmarking in order to elucidate the target performance in which PEC technology could be positively implemented at large-scale. Efficiencies over 10% (STH) and 7 years of lifetime are compulsory in the coming developments to achieve a positive scaling-up.

Bioelectrochemical systems (BES) are becoming popular technologies with a plethora of applications in the environmental field. However research on the scale-up of these systems is scarce. To understand the limiting factors of hydrogen production in microbial electrolysis cell (MEC) at pilot scale a 135 L MEC was operated for six months under a wide range of operational conditions: applied potential [0.8-1.1 V] hydraulic residence time [1.1-3.9 d] and temperature [18-30 ºC] using three types of wastewater; synthetic (900 mg CODs L-1) raw urban wastewater (200 mg CODs L-1) and urban wastewater amended with acetate (1000 mg CODs L-1). The synthetic wastewater yielded the maximum current density (1.23 A m-2) and hydrogen production (0.1 m3 m-3 d-1) ever reported in a pilot scale MEC with a cathodic recovery of 70% and a coulombic efficiency of 27%. In contrast the use of low COD urban wastewater limited the plant performance. Interestingly it was possible to improve hydrogen production by reducing the hydraulic residence time finding the optimal applied potential or increasing the temperature. Further the pilot plant demonstrated a robust capacity to remove the organic matter present in the wastewater under different conditions with removal efficiencies above 70%. This study shows improved results compared to similar MEC pilot plants treating domestic wastewater in terms of hydrogen production and treatment efficiency and also compares its performance against conventional activated sludge processes.

Although alkaline water electrolysis (AWE) is the most widespread technology for hydrogen production by electrolysis its electrochemical and fluid dynamic optimization has rarely been addressed simultaneously using Computational Fluid Dynamics (CFD) simulation. In this regard a two-dimensional (2D) CFD model of an AWE cell has been developed using COMSOL® software and then experimentally validated. The model involves transport equations for both liquid and gas phases as well as equations for the electric current conservation. This multiphysics approach allows the model to simultaneously analyze the fluid dynamic and electrochemical phenomena involved in an electrolysis cell. The electrical response was evaluated in terms of polarization curve (voltage vs. current density) at different operating conditions: temperature electrolyte conductivity and electrode-diaphragm distance. For all cases the model fits very well with the experimental data with an error of less than 1% for the polarization curves. Moreover the model successfully simulates the changes on gas profiles along the cell according to current density electrolyte flow rate and electrode-diaphragm distance. The combination of electrochemical and fluid dynamics studies provides comprehensive information and makes the model a promising tool for electrolysis cell design.

Sustainability is one of the main challenges the aviation industry is currently facing. In a global context of energy transition towards cleaner and renewable sources the sector is developing technologies to fly more efficiently and mitigate its environmental impact. Innovative propulsion alternatives such as biofuels electric aircraft and hydrogen engines are already a reality or are close to becoming so. To assess their feasibility a study is conducted on specific routes and aircraft across different flight ranges. The analysis focuses on the Canary Islands an outermost region of the EU with high mobility and no comparable alternative means of transport. For three routes flight profiles are analyzed obtaining the fuel consumption and emissions generated by the conventional propulsion and later applying the sustainable alternatives. The results indicate optimistic perspectives with reductions in environmental impact ranging between 40% and 75% compared to the present.

Achieving European climate neutrality by 2050 requires further efforts not only from the industry and society but also from policymakers. The use of high-efficiency cogeneration facilities will help to reduce both primary energy consumption and CO2 emissions because of the increase in overall efficiency. Fuel cell-based cogeneration technologies are relevant solutions to these points for small- and microscale units. In this research an innovative and new fuel cell-based cogeneration plant is studied and its performance is compared with other cogeneration technologies to evaluate the potential reduction degree in energy consumption and CO2 emissions. Four energy consumption profile datasets have been generated from real consumption data of different dwellings located in the Mediterranean coast of Spain to perform numerical simulations in different energy scenarios according to the fuel used in the cogeneration. Results show that the fuel cell-based cogeneration systems reduce primary energy consumption and CO2 emissions in buildings to a degree that depends on the heat-to-power ratio of the consumer. Primary energy consumption varies from 40% to 90% of the original primary energy consumption when hydrogen is produced from natural gas reforming process and from 5% to 40% of the original primary energy consumption if the cogeneration is fueled with hydrogen obtained from renewable energy sources. Similar reduction degrees are achieved in CO2 emissions.

A main restriction of renewables from intermittent sources is the mismatch between energy resource availability and energy requirements especially when extensive power plants are producing at their highest potential causing huge energy surpluses. In these cases excess power must be stored or curtailed. One alternative is increasing urban solar potential which could be integrated to feed electric buses directly or alternatively through hydrogen (H2 ) as an energy vector. H2 from renewable electricity can be stored and used directly or through fuel cells. This study aims to determine the H2 capability that could be achieved when integrating large-scale photovoltaic (PV) generation in urban areas. This analysis was carried out by determining the PV energy potentially generated by installing PV in Cuenca City downtown (Ecuador). Cuenca is in the process of adopting renewal of the public transport vehicle fleet introducing a new model with an electric tram main network combined with “clean type buses”. The conventional diesel urban transport could be replaced establishing a required vehicle fleet of 475 buses spread over 29 routes emitting 112 tons of CO2 and burning 11175 gallons of diesel daily. Between the main findings we concluded that the electricity that could be produced in the total roof area exceeds the actual demand in the study area by 5.5 times. Taking into account the energy surplus it was determined that the available PV power will cover from 97% to 127% of the total demand necessary to mobilize the city bus fleet. The novelty of this work is the proposal of a combined methodology to find the potential to feed urban transport with urban solar power in cities close to the equatorial line.