Spain

One of the options to reduce the dependence on fossil fuels is to produce gas with the quality of natural gas but based on renewable energy sources. It can encompass among other biogas generation from various types of biomass and its subsequent upgrading. The main aim of this study is to analyze under a combined technical economic and environmental perspective three of the most representative technologies for the production of biomethane (bio-based natural gas): (i) manure fermentation and its subsequent upgrading by CO₂ removal (ii) manure fermentation and biogas methanation using renewable hydrogen from electrolysis and (iii) biomass gasification in the atmosphere of oxygen and methanation of the resulted gas. Thermodynamic economic and environmental analyses are conducted to thoroughly compare the three cases. For these purposes detailed models in Aspen Plus software were built while environmental analysis was performed using the Life Cycle Assessment methodology. The results show that the highest efficiency (66.80%) and the lowest break-even price of biomethane (19.2 €/GJ) are reached for the technology involving fermentation and CO₂ capture. Concerning environmental assessment the system with the best environmental performance varies depending on the impact category analyzed being the system with biomass gasification and methanation a suitable trade-off solution for biomethane production.

A review of the effect of hydrogen on materials is addressed in this paper. General aspects of the interaction of hydrogen and materials hydrogen embrittlement low temperature effects material suitability for hydrogen service and materials testing are the main subjects considered in the first part of the paper. As a particular case of the effect of hydrogen in materials the hydride formation of titanium alloys is considered. Alpha titanium alloys are considered corrosion resistant materials in a wide range of environments. However hydrogen absorption and the possible associated problems must be taken into account when considering titanium as a candidate material for high responsibility applications. The sensitivity of three different titanium alloys Ti Gr-2 Ti Gr-5 and Ti Gr-12 to the Hydrogen Assisted Stress Cracking phenomena has been studied by means of the Slow Strain Rate Technique (SSRT). The testing media has been sea water and hydrogen has been produced on the specimen surface during the test by cathodic polarization. Tested specimens have been characterized by metallography and scanning electron microscopy. Results obtained show that the microstructure of the materials particularly the β phase content plays an important role on the sensitivity of the studied alloys to the Hydrogen Assisted Stress Cracking Phenomena.

Thermal power plants face substantial challenges to remain competitive in energy systems with high shares of variable renewables especially inflexible integrated gasification combined cycles (IGCC). This study addresses this challenge through the integration of Gas Switching Combustion (GSC) and Membrane Assisted Water Gas Shift (MAWGS) reactors in an IGCC plant for flexible electricity and/or H₂ production with inherent CO₂ capture. When electricity prices are high H₂ from the MAWGS reactor is used for added firing after the GSC reactors to reach the high turbine inlet temperature of the H-class gas turbine. In periods of low electricity prices the turbine operates at 10% of its rated power to satisfy the internal electricity demand while a large portion of the syngas heating value is extracted as H₂ in the MAWGS reactor and sold to the market. This product flexibility allows the inflexible process units such as gasification gas treating air separation unit and CO2 compression transport and storage to operate continuously while the plant supplies variable power output. Two configurations of the GSC-MAWGS plant are presented. The base configuration achieves 47.2% electric efficiency and 56.6% equivalent hydrogen production efficiency with 94.8–95.6% CO₂ capture. An advanced scheme using the GSC reduction gases for coal-water slurry preheating and pre-gasification reached an electric efficiency of 50.3% hydrogen efficiency of 62.4% and CO₂ capture ratio of 98.1–99.5%. The efficiency is 8.4%-points higher than the pre-combustion CO₂ capture benchmark and only 1.9%-points below the unabated IGCC benchmark.

This paper presents a compilation and discussion of the results supplied by HySafe partners participating in the Standard Benchmark Exercise Problem (SBEP) V1 which is based on an experiment on hydrogen release mixing and distribution inside a vessel. Each partner has his own point of view of the problem and uses a different approach to the solution. The main characteristics of the models employed for the calculations are compared. The comparison between results together with the experimental data when available is made. Relative deviations of each model from the experimental values are also included. Explanations and interpretations of the results are presented together with some useful conclusions for future work.

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%.

The utilization of power to gas technologies to store renewable electricity surpluses in the form of hydrogen enables the integration of the gas and electricity sectors allowing the decarbonization of the natural gas network through green hydrogen injection. Nevertheless the injection of significant amounts of hydrogen may lead to high local concentrations that may degrade materials (e.g. hydrogen embrittlement of pipelines) and in general be not acceptable for the correct and safe operation of appliances. Most countries have specific regulations to limit hydrogen concentration in the gas network. The methanation of hydrogen represents a potential option to facilitate its injection into the grid. However stoichiometric methanation will lead to a significant presence of carbon dioxide limited in gas networks and requires an accurate design of several reactors in series to achieve relevant concentrations of methane. These requirements are smoothed when the methanation is undertaken under non-stoichiometric conditions (high H/C ratio). This study aims to assess to influence of nonstoichiometric methanation under different H/C ratios on the limitations presented by the pure hydrogen injection. The impact of this injection on the operation of the gas network at local level has been investigated and the fluid-dynamics and the quality of gas blends have been evaluated. Results show that non-stoichiometric methanation could be an alternative to increase the hydrogen injection in the gas network and facilitates the gas and electricity sector coupling.

The safest way to store hydrogen is in solid form physically entrapped in molecular form in highly porous materials or chemically bound in atomic form in hydrides. Among the different families of these compounds alkaline and alkaline earth metals alumino-hydrides (alanates) have been regarded as promising storing media and have been extensively studied since 1997 when Bogdanovic and Schwickardi reported that Ti-doped sodium alanate could be reversibly dehydrogenated under moderate conditions. In this review the preparative methods; the crystal structure; the physico-chemical and hydrogen absorption-desorption properties of the alanates of Li Na K Ca Mg Y Eu and Sr; and of some of the most interesting multi-cation alanates will be summarized and discussed. The most promising alanate-based reactive hydride composite (RHC) systems developed in the last few years will also be described and commented on concerning their hydrogen absorption and desorption performance.

Hydrogen has been extensively used in many industrial applications for more than 100 years including production storage transport delivery and final use. Nevertheless the goal of the hydrogen energy system implies the use of hydrogen as an energy carrier in a more wide scale and for a public not familiarised with hydrogen technologies and properties.<br/>The road to the hydrogen economy passes by the development of safe practices in the production storage distribution and use of hydrogen. These issues are essential for hydrogen insurability. We have to bear in mind that a catastrophic failure in any hydrogen project could damage the insurance public perception of hydrogen technologies at this early step of development of hydrogen infrastructures.<br/>Safety is a key issue for the development of hydrogen economy and a great international effort is being done by different stakeholders for the development of suitable codes and standards concerning safety for hydrogen technologies [1 2]. Additionally to codes and standards different studies have been done regarding safety aspects of particular hydrogen energy projects during the last years [3 4]. Most of such have been focused on hydrogen production and storage in large facilities transport delivery in hydrogen refuelling stations and utilization mainly on fuel cells for mobile and stationary applications. In comparison safety considerations for hydrogen storage in small or medium scale facilities as usual in hydrogen production plants from renewable energies have received relatively less attention.<br/>After a brief introduction to risk assessment for hydrogen facilities this paper reports an example of risk assessment of a small solar hydrogen storage system applied to the INTA Solar Hydrogen Production and Storage facility as particular case and considers a top level Preliminary Failure Modes and Effects Analysis (FMEA) for the identification of hazard associated to the specific characteristics of the facility.

Mountain huts as special stand-alone micro-grid systems are not connected to a power grid and represent a burden on the environment. The micro-grid has to be flexible to cover daily and seasonal fluctuations. Heat and electricity are usually generated with fossil fuels due to the simple on-off operation. By introducing renewable energy sources (RESs) the generation of energy could be more sustainable but the generation and consumption must be balanced. The paper describes the integration of a hydrogen-storage system (HSS) and a battery-storage system (BattS) in a mountain hut. The HSS involves a proton-exchange-membrane water electrolyser (PEMWE) a hydrogen storage tank (H₂ tank) a PEM fuel cell (PEMFC) and a BattS consisting of lead-acid batteries. Eight micro-grid configurations were modelled using HOMER and evaluated from the technical environmental and economic points of view. A life-cycle assessment analysis was made from the cradle to the gate. The micro-grid configurations with the HSS achieve on average a more than 70% decrease in the environmental impacts in comparison to the state of play at the beginning but require a larger investment. Comparing the HSS with the BattS as a seasonal energy storage the hydrogen-based technology had advantages for all of the assessed criteria.

Worldwide the road transport sector typically arises as one of the main sources of air pollutants due to its high energy intensity and the use of fossil fuels. Thus governments and social agents work on the development and prospective planning of decarbonisation strategies oriented towards sustainable transport. In this regard the increase in the use of alternative fuels is the recurrent approach to energy planning e.g. through the promotion of electric vehicles biofuels natural gas liquefied petroleum gas etc. However there is a lack of comprehensive information on the techno-economic performance of production pathways for alternative fuels. The acquisition of robust techno-economic data is still a challenge for energy planners modellers analysts and policy-makers when building their prospective models to support decision-making processes. Hence this article aims to fill this gap through a deep literature review including the most representative production routes for a wide range of road transportation fuels. This led to the development of datasets including investment costs operating and maintenance costs and transformation efficiencies for more than 40 production pathways. The techno-economic data presented in this work are expected to be especially useful to those energy actors interested in performing long-term studies on the transition to a sustainable transport system.