Spain
Fuel-Cell Electric Vehicles: Plotting a Scientific and Technological Knowledge Map
Mar 2020
Publication
The fuel-cell electric vehicle (FCEV) has been defined as a promising way to avoid road transport greenhouse emissions but nowadays they are not commercially available. However few studies have attempted to monitor the global scientific research and technological profile of FCEVs. For this reason scientific research and technological development in the field of FCEV from 1999 to 2019 have been researched using bibliometric and patent data analysis including network analysis. Based on reports the current status indicates that FCEV research topics have reached maturity. In addition the analysis reveals other important findings: (1) The USA is the most productive in science and patent jurisdiction; (2) both Chinese universities and their authors are the most productive in science; however technological development is led by Japanese car manufacturers; (3) in scientific research collaboration is located within the tri-polar world (North America–Europe–Asia-Pacific); nonetheless technological development is isolated to collaborations between companies of the same automotive group; (4) science is currently directing its efforts towards hydrogen production and storage energy management systems related to battery and hydrogen energy Life Cycle Assessment and greenhouse gas (GHG) emissions. The technological development focuses on technologies related to electrically propelled vehicles; (5) the International Journal of Hydrogen Energy and SAE Technical Papers are the two most important sources of knowledge diffusion. This study concludes by outlining the knowledge map and directions for further research.
On Green Hydrogen Generation Technologies: A Bibliometric Review
Mar 2024
Publication
Green hydrogen produced by water electrolysis with renewable energy plays a crucial role in the revolution towards energy sustainability and it is considered a key source of clean energy and efficient storage. Its ability to address the intermittency of renewable sources and its potential to decarbonize sectors that are difficult to electrify make it a strategic component in climate change mitigation. By using a method based on a bibliometric review of scientific publications this paper represents a significant contribution to the emerging field of research on green hydrogen and provides a detailed review of electrolyzer technologies identifying key areas for future research and technology development. The results reflect the immaturity of a technology which advances with different technical advancements waiting to find the optimal technical solution that allows for its massive implementation as a source of green hydrogen generation. According to the results found in this article alkaline (ALK) and proton exchange membrane (PEM) electrolyzers seem to be the ones that interest the scientific community the most. Similarly in terms of regional analysis Europe is clearly committed to green hydrogen in view of the analysis of its scientific results on materials and electrolyzer capacity forecasts for 2030.
Future of Electric and Hydrogen Cars and Trucks: An Overview
Apr 2023
Publication
The negative consequences of toxic emissions from internal combustion engines energy security climate change and energy costs have led to a growing demand for clean power sources in the automotive industry. The development of eco-friendly vehicle technologies such as electric and hydrogen vehicles has increased. This article investigates whether hydrogen vehicles will replace electric vehicles in the future. The results showed that fuel-cell cars are unlikely to compete with electric cars. This is due to the advancements in electric vehicles and charging infrastructure which are becoming more cost-effective and efficient. Additionally the technical progress in battery electric vehicles (BEVs) is expected to reduce the market share of fuel-cell electric vehicles (FCEVs) in passenger vehicles. However significant investments have been made in hydrogen cars. Many ongoing investments seem to follow the sunk cost fallacy where decision-makers continue to invest in an unprofitable project due to their already invested resources. Furthermore even with megawatt charging fuel-cell trucks cost more than battery-powered electric trucks. The use cases for fuel-cell electric trucks are also much more limited as their running expenses are higher compared to electric cars. Hydrogen vehicles may be beneficial for heavy transport in remote areas. However it remains to be seen if niche markets are large enough to support fuel-cell electric truck commercialization and economies of scale. In summary we believe that hydrogen vehicles will not replace electric cars and trucks at least before 2050.
Transition to a Low-carbon Building Stock. Techno-economic and Spatial Optimization of Renewables‑hydrogen Strategies in Spain
Oct 2022
Publication
Europe has set ambitious targets to reduce the final energy consumption of buildings in concerning the degree of electrification energy efficiency and penetration of renewable energy sources (RES). So far hydrogen is becoming an increasingly important energy vector offering huge opportunities to promote the share of intermittent RES. Thus this manuscript proposes an energy model for the complete decarbonization of the estimated electricity consumed by the Spanish building stock in 2030 and 2050 scenarios; the model is based on the combination of photovoltaic and wind primary sources and hydrogen technologies considering both distributed and centralized configurations applying also geospatial criteria for their optimal allocation. Large-scale RES generation centralized hydrogen production and re-electrification along with underground hydrogen storage result in the lowest levelized cost of energy (LCOE) hydrogen production costs (HPC) and the highest overall efficiency (μSYS). Wind energy is mainly harvested in the north of Spain while large PV farms are deployed in the mid-south. Furthermore reinforcement of underground hydrogen storage enhances the overall system performance reducing surplus energy and the required RES generation capacity. Finally all the considered scenarios achieve LCOE below the Spanish utility grid benchmark apart from accomplishing the decarbonization goals established for the year 2030.
Analysis of Power to Gas Technologies for Energy Intensive Industries in European Union
Jan 2023
Publication
Energy Intensive Industries (EII) are high users of energy and some of these facilities are extremely dependent on Natural Gas for processing heat production. In European countries where Natural Gas is mostly imported from external producers the increase in international Natural Gas prices is making it difficult for some industries to deliver the required financial results. Therefore they are facing complex challenges that could cause their delocalization in regions with lower energy costs. European countries lack on-site Natural Gas resources and the plans to reduce greenhouse gas emissions in the industrial sector make it necessary to find an alternative. Many different processes cannot be electrified and in these cases synthetic methane is one of the solutions and also represents an opportunity to reduce external energy supply dependency. This study analyzes the current development of power-to-gas technological solutions that could be implemented in large industrial consumers to produce Synthetic Methane using Green Hydrogen as a raw source and using Renewable Energy electricity mainly produced with photovoltaic or wind energy. The study also reviews the triple bottom line impact and the current development status and associated costs for each key component of a power-to-gas plant and the requirements to be fulfilled in the coming years to develop a cost-competitive solution available for commercial use.
Comparative Sustainability Study of Energy Storage Technologies Using Data Envelopment Analysis
Mar 2022
Publication
The transition to energy systems with a high share of renewable energy depends on the availability of technologies that can connect the physical distances or bridge the time differences between the energy supply and demand points. This study focuses on energy storage technologies due to their expected role in liberating the energy sector from fossil fuels and facilitating the penetration of intermittent renewable sources. The performance of 27 energy storage alternatives is compared considering sustainability aspects by means of data envelopment analysis. To this end storage alternatives are first classified into two clusters: fast-response and long-term. The levelized cost of energy energy and water consumption global warming potential and employment are common indicators considered for both clusters while energy density is used only for fast-response technologies where it plays a key role in technology selection. Flywheel reveals the highest efficiency between all the fast-response technologies while green ammonia powered with solar energy ranks first for long-term energy storage. An uncertainty analysis is incorporated to discuss the reliability of the results. Overall results obtained and guidelines provided can be helpful for both decision-making and research and development purposes. For the former we identify the most appealing energy storage options to be promoted while for the latter we report quantitative improvement targets that would make inefficient technologies competitive if attained. This contribution paves the way for more comprehensive studies in the context of energy storage by presenting a powerful framework for comparing options according to multiple sustainability indicators.
Three-dimensional Simulations of Lean H2-air Flames Propagating in a Narrow Gap: n the Validity of the Quasi-two-dimensional Appoximation
Sep 2021
Publication
The premixed propagation of lean isobaric H2-air flames (φ = 0.3) in Hele-Shaw cells (i.e. two parallel plates separated by a small distance h on the order of the thickness of the planar adiabatic flame δf ∼ 3 mm) is investigated numerically. Three-dimensional (3D) simulations with detailed chemistry and transport are used to examine the effect of h on the flame dynamics and its overall normalized propagation speed (S T /S L) for a semi-closed system of size 25δf × 25δf × h. To determine the validity of an existing quasi-two-dimensional (quasi-2D) formulation (derived in the limit of h → 0) to capture the 3D dynamics results for h = 0.1δf h = 0.5δf and h = δf are reported. For h = 0.1δf strong cell splitting/merging is observed with associated low frequency/high amplitude oscillations in the temporal evolution of S T /S L (10-17Hz; 6 ≤ S T /S L ≤ 10). Larger values of h exhibit a much smoother evolution. For h = 0.5δf the cell splitting/merging is milder relaxing to a steady propagating speed of S T /S L ∼ 6 after an initial transient; for h = 1δf the flame dynamics along the h direction starts to play an important role showing two distinct phases: (i) initial symmetric propagation with a linear increase in S T /S L (from 5.3 to 6.8) as early signs of asymmetry are visible (ii) followed by a fully non-symmetric propagation resulting in an abrupt increase in S T /S L that quickly relaxes to a constant value thereafter (S T /S L ∼ 10). Our preliminary results suggest that for the lean H2-air mixture considered the quasi-2D approximation breaks down for h > 0.1δf .
Hydrogen-powered Refrigeration System for Environmentally Friendly Transport and Delivery in the Food Supply Chain
Mar 2023
Publication
Urban population and the trend towards online commerce leads to an increase in delivery solution in cities. The growth of the transport sector is very harmful to the environment being responsible for approximately 40% of greenhouse gas emissions in the European Union. The problem is aggravated when transporting perishable foodstuffs as the vehicle propulsion engine (VPE) must power not only the vehicle but also the refrigeration unit. This means that the VPE must be running continuously both on the road and stationary (during delivery) as the cold chain must be preserved. The result is costly (high fuel consumption) and harmful to the environment. At present refrigerated transport does not support full-electric solutions due to the high energy consumption required which motivates the work presented in this article. It presents a turnkey solution of a hydrogen-powered refrigeration system (HPRS) to be integrated into standard light trucks and vans for short-distance food transport and delivery. The proposed solution combines an air-cooled polymer electrolyte membrane fuel cell (PEMFC) a lithium-ion battery and low-weight pressurised hydrogen cylinders to minimise cost and increase autonomy and energy density. In addition for its implementation and integration all the acquisition power and control electronics necessary for its correct management have been developed. Similarly an energy management system (EMS) has been developed to ensure continuity and safety in the operation of the electrical system during the working day while maximizing both the available output power and lifetime of the PEMFC. Experimental results on a real refrigerated light truck provide more than 4 h of autonomy in intensive intercity driving profiles which can be increased if necessary by simply increasing the pressure of the stored hydrogen from the current 200 bar to whatever is required. The correct operation of the entire HPRS has been experimentally validated in terms of functionality autonomy and safety; with fuel savings of more than 10% and more than 3650 kg of CO2/ year avoided.
Low Temperature Autoignition of Diesel Fuel Under Dual Operation with Hydrogen and Hydrogen-carriers
Mar 2022
Publication
While electrification of light duty vehicles is becoming a real solution to abate local pollutant as well as greenhouse gases emission heavy duty applications (such as long distance freight and maritime transport) will keep requiring fuel-based propulsion systems. In these sectors dominated by compression ignition engines research on alternative biofuels and new combustion modes is still highly necessary. Dual-fuel combustion appears as a very promising concept to replace conventional diesel fuel by sustainable ones. Among the latter hydrogen-derived fuels (the so-called electrofuels or e-fuels) are maybe the most interesting. This work addresses the effect of partial substitution of diesel fuel by hydrogen and hydrogen-carriers (ammonia and methane) on the autoignition process under low temperature conditions. Tests were carried out in a constant volume combustion chamber at different temperatures (535 600 and 650 ◦C) and pressures (11 16 and 21 bar). While the cool flames timing and intensity was only slightly affected by the low reactivity fuel energy content the main ignition was delayed this effect being much more noticeable for ammonia followed by hydrogen and finally methane. Kinetic simulations showed a clear competition for active radicals between both fuels (diesel and low reactivity fuel). The combustion duration also increased with the hydrogen or hydrogen-carrier content which greatly points to the need of modifications in the injection strategy of compression ignition engines operating under dual mode. A correlation was proposed for estimating the autoignition delay time for dual-fuel lean combustion at low temperature.
Recent Insights into Low-Surface-Area Catalysts for Hydrogen Production from Ammonia
Nov 2022
Publication
A potential method of storing and transporting hydrogen safely in a cost-effective and practical way involves the utilization of molecules that contain hydrogen in their structure such as ammonia. Because of its high hydrogen content and carbon-free molecular structure as well as the maturity of related technology (easy liquefaction) ammonia has gained attention as a “hydrogen carrier” for the generation of energy. Unfortunately hydrogen production from ammonia requires an efficient catalyst to achieve high conversion at low reaction temperatures. Recently very attractive results have been obtained with low-surface-area materials. This review paper is focused on summarizing and comparing recent advances in novel economic and active catalysts for this reaction paying particular attention to materials with low surface area such as silicon carbide (SiC) and perovskites (ABO3 structure). The effects of the supports the active phase and the addition of promoters in such low-porosity materials have been analyzed in detail. Advances in adequate catalytic systems (including support and active metal) benefit the perspective of ammonia as a hydrogen carrier for the decarbonization of the energy sector and accelerate the “hydrogen economy”.
Production of Hydrogen by Chemical Looping Reforming of Methane and Biogas using a Reactive and Durable Cu-based Oxygen Carrier
Apr 2022
Publication
The objective of this work was to assess the suitability of a synthetic Cu-based oxygen carrier in a continuous pilot plant for the production of blue and green hydrogen through the autothermal Chemical Looping Reforming (CLRa). In CLRa methane is converted to a H2 + CO mixture through partial oxidation and reforming reactions in the fuel reactor. The degree of the partial oxidation of methane was defined by controlling the oxygen flow in the air reactor. Steam was used as reforming gas in natural gas to produce blue H2 but the existing CO2 in biogas was the reforming gas to produce green H2. Operating at 950 ◦C in the fuel and air reactors CH4 conversion and H2 yield parameters were 96 % and 2.60 mol of H2 per mole of CH4 respectively. These experimental results were close to the theoretical values that could be achieved in the CLRa process. Furthermore the physico-chemical characterization of the samples extracted from the pilot plant throughout the experimental campaign revealed that the Cu-based oxygen carrier maintained its mechanical integrity and chemical stability under harsh operating conditions. Therefore it can be concluded that Cu-based oxygen carriers can be considered a promising alternative to Ni-based materials for the production of blue and green hydrogen through the CLRa process.
The Role of the Testing Rate on Small Punch Tests for the Estimation of Fracture Toughness in Hydrogen Embrittlement
Dec 2020
Publication
In this paper different techniques to test notched Small Punch (SPT) samples in fracture conditions in aggressive environments are studied based on the comparison of the micromechanisms at different rates. Pre-embrittled samples subsequently tested in air at rates conventionally employed (0.01 and 0.002 mm/s) are compared to embrittled ones tested in environment at the same rates (0.01 and 0.002 mm/s) and at a very slow rate (5E-5 mm/s). A set of samples tested in environment under a set of constant loads that produce very slow rates completes the experimental results. As a conclusion it is recommended to test SPT notched specimens in environment at very slow rates of around E-6 mm/s when characterizing in Hydrogen Embrittlement (HE) scenarios in order to allow the interaction material-environment to govern the process.
Environmentally Assisted Cracking Behavior of S420 and X80 Steels Containing U-notches at Two Different Cathodic Polarization Levels: An Approach from the Theory of Critical Distances
May 2019
Publication
This paper analyzes using the theory of critical distances the environmentally assisted cracking behaviour of two steels (S420 and API X80) subjected to two different aggressive environments. The propagation threshold for environmentally assisted cracking (i.e. the stress intensity factor above which crack propagation initiates) in cracked and notched specimens (KIEAC and KNIEAC) has been experimentally obtained under different environmental conditions. Cathodic polarization has been employed to generate the aggressive environments at 1 and 5 mA/cm2 causing hydrogen embrittlement on the steels. The point method and the line method both belonging to the theory of critical distances have been applied to verify their capacity to predict the initiation of crack propagation. The results demonstrate the capacity of the theory of critical distances to predict the crack propagation onset under the different combinations of material and aggressive environments.
Hydrogen Embrittlement and Notch Tensile Strength of Pearlitic Steel: A Numerical Approach
Dec 2020
Publication
This paper offers a numerical approach to the problem of hydrogen embrittlement and notch tensile strength of sharply notched specimens of high-strength pearlitic steel supplied in the form of hot rolled bars by using the finite element method in order to determine how the notch depth influences the concentration of hydrogen in the steady-state regime for different loading values. Numerical results show that the point of maximum hydrostatic stress (towards which hydrogen is transported by a mechanism of stress-assisted diffusion) shifts from the notch tip to the inner points of the specimen under increasing load with numerical evidence of an elevated inwards gradient of hydrostatic stress “pumping” hydrogen inside the sample.
Opportunities and Barriers of Hydrogen–Electric Hybrid Powertrain Vans: A Systematic Literature Review
Oct 2020
Publication
The environmental impact of the road transport sector together with urban freight transport growth has a notable repercussions in global warming health and economy. The need to reduce emissions caused by fossil fuel dependence and to foster the use of renewable energy sources has driven the development of zero-emissions powertrains. These clean transportation technologies are not only necessary to move people but to transport the increasing demand for goods and services that is currently taking place in the larger cities. Full electric battery-powered vans seem to be the best-placed solution to the problem. However despite the progress in driving range and recharge options those and other market barriers remain unsolved and the current market share of battery electric vehicles (BEVs) is not significant. Based on the development of hydrogen fuel cell stacks this work explains an emerging powertrain architecture concept for N1 class type vans that combines a battery-electric configuration with a fuel cell stack powered by hydrogen that works as a range extender (FC-EREV). A literature review is conducted with the aim to shed light on the possibilities of this hybrid light-duty commercial van for metropolitan delivery tasks providing insights into the key factors and issues for sizing the powertrain components and fuel management strategies to meet metropolitan freight fleet needs.
Hydrogen Permeation Studies of Composite Supported Alumina-carbon Molecular Sieves Membranes: Separation of Diluted Hydrogen from Mixtures with Methane
Jun 2020
Publication
One alternative for the storage and transport of hydrogen is blending a low amount of hydrogen (up to 15 or 20%) into existing natural gas grids. When demanded hydrogen can be then separated close to the end users using membranes. In this work composite alumina carbon molecular sieves membranes (Al-CMSM) supported on tubular porous alumina have been prepared and characterized. Single gas permeation studies showed that the H2/CH4 separation properties at 30 °C are well above the Robeson limit of polymeric membranes. H2 permeation studies of the H2–CH4 mixture gases containing 5–20% of H2 show that the H2 purity depends on the H2 content in the feed and the operating temperature. In the best scenario investigated in this work for samples containing 10% of H2 with an inlet pressure of 7.5 bar and permeated pressure of 0.01 bar at 30 °C the H2 purity obtained was 99.4%.
An Autonomous Device for Solar Hydrogen Production from Sea Water
Feb 2022
Publication
Hydrogen production from water electrolysis is one of the most promising approaches for the production of green H2 a fundamental asset for the decarbonization of the energy cycle and industrial processes. Seawater is the most abundant water source on Earth and it should be the feedstock for these new technologies. However commercial electrolyzers still need ultrapure water. The debate over the advantages and disadvantages of direct sea water electrolysis when compared with the implementation of a distillation/purification process before the electrolysis stage is building in the relevant research. However this debate will remain open for some time essentially because there are no seawater electrolyser technologies with which to compare the modular approach. In this study we attempted to build and validate an autonomous sea water electrolyzer able to produce high-purity green hydrogen (>90%) from seawater. We were able to solve most of the problems that natural seawater electrolyses imposes (high corrosion impurities etc.) with decisions based on simplicity and sustainability and those issues that are yet to be overcome were rationally discussed in view of future electrolyzer designs. Even though the performance we achieved may still be far from industrial standards our results demonstrate that direct seawater electrolysis with a solar-to-hydrogen efficiency of ≈7% can be achieved with common low-cost materials and affordable fabrication methods.
Perspectives on Cathodes for Protonic Ceramic Fuel Cells
Jun 2021
Publication
Protonic ceramic fuel cells (PCFCs) are promising electrochemical devices for the efficient and clean conversion of hydrogen and low hydrocarbons into electrical energy. Their intermediate operation temperature (500–800 °C) proffers advantages in terms of greater component compatibility unnecessity of expensive noble metals for the electrocatalyst and no dilution of the fuel electrode due to water formation. Nevertheless the lower operating temperature in comparison to classic solid oxide fuel cells places significant demands on the cathode as the reaction kinetics are slower than those related to fuel oxidation in the anode or ion migration in the electrolyte. Cathode design and composition are therefore of crucial importance for the cell performance at low temperature. The different approaches that have been adopted for cathode materials research can be broadly classified into the categories of protonic–electronic conductors oxide-ionic–electronic conductors triple-conducting oxides and composite electrodes composed of oxides from two of the other categories. Here we review the relatively short history of PCFC cathode research discussing trends highlights and recent progress. Current understanding of reaction mechanisms is also discussed.
Direct Route from Ethanol to Pure Hydrogen through Autothermal Reforming in a Membrane Reactor: Experimental Demonstration, Reactor Modelling and Design
Nov 2020
Publication
This work reports the integration of thin (~3e4 mm thick) Pd-based membranes for H2 separation in a fluidized bed catalytic reactor for ethanol auto-thermal reforming. The performance of a fluidized bed membrane reactor has been investigated from an experimental and numerical point of view. The demonstration of the technology has been carried out over 50 h under reactive conditions using 5 thin Pd-based alumina-supported membranes and a 3 wt%Pt-10 wt%Ni catalyst deposited on a mixed CeO2/SiO2 support. The results have confirmed the feasibility of the concept in particular the capacity to reach a hydrogen recovery factor up to 70% while the operation at different fluidization regimes oxygen-to-ethanol and steam-to-ethanol ratios feed pressures and reactor temperatures have been studied. The most critical part of the system is the sealing of the membranes where most of the gas leakage was detected. A fluidized bed membrane reactor model for ethanol reforming has been developed and validated with the obtained experimental results. The model has been subsequently used to design a small reactor unit for domestic use showing that 0.45 m2 membrane area is needed to produce the amount of H2 required for a 5 kWe PEM fuel-cell based micro-CHP system.
Use of Hydrogen in Off-Grid Locations, a Techno-Economic Assessment
Nov 2018
Publication
Diesel generators are currently used as an off-grid solution for backup power but this causes CO2 and GHG emissions noise emissions and the negative effects of the volatile diesel market influencing operating costs. Green hydrogen production by means of water electrolysis has been proposed as a feasible solution to fill the gaps between demand and production the main handicaps of using exclusively renewable energy in isolated applications. This manuscript presents a business case of an off-grid hydrogen production by electrolysis applied to the electrification of isolated sites. This study is part of the European Ely4off project (n◦ 700359). Under certain techno-economic hypothesis four different system configurations supplied exclusively by photovoltaic are compared to find the optimal Levelized Cost of Electricity (LCoE): photovoltaic-batteries photovoltaic-hydrogen-batteries photovoltaic-diesel generator and diesel generator; the influence of the location and the impact of different consumptions profiles is explored. Several simulations developed through specific modeling software are carried out and discussed. The main finding is that diesel-based systems still allow lower costs than any other solution although hydrogen-based solutions can compete with other technologies under certain conditions.
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