H2 Volume Research Articles

Effect of low volume fraction of H2 on explosion characteristics and mechanism of AlH3 dust via connected container

During the storage and use of AlH3, a small amount of H2 is easily decomposed, forming a multiphase composite system that increases explosive hazard. This article discussed the AlH3 dust inducing low concentration H2 explosion and venting characteristics by a connected vessel. The results show that when the concentration of H2 was 1 % and 3 %, which was lower than the lower explosive limit of H2 (4 %), H2 was non-flammable, and the explosion was dust-driven explosion. At H2 volume fraction of 5 %, a dual-fuel-driven explosion dominated, culminating in the maximum explosion pressure, reduced pressure, venting flame length, and velocity. The microscopic reaction mechanism of AlH3 with H2 was explored using molecular dynamics simulations. Meanwhile, for the security strategy of AlH3 dust explosion venting with low H2 atmosphere, the NFPA 68 and EN 14491 standards predicted the venting flame length effectively, offering critical insights for the application and safety design of AlH3.

Deflagration dynamics of ammonia-syngas-air premixed flames in T-type tube

In the context of carbon peak carbon neutrality, the carbon-free emission of NH3 combustion has received increasing attention within the field of combustion, but due to the low activity of NH3, research has generally been carried out through NH3 blending with other more active hydrocarbon fuels. In this work, a combination of experimental and simulation approach was used to study the premixed flame combustion characteristics of ammonia-syngas-air mixture. Two fuels, NH3 and H2 (one of the main components of syngas), were used as the main body of the mixture and their volume fractions were set to vary from 0 to 1, respectively. Then comparative analyses were performed on the flame base combustion characteristics. The results of the study showed that an increase in the volume fraction of NH3 decreases the flame propagation speed, while H2 has the opposite effect. For example, when both NH3 and H2 volume fractions were 0.6, the time required for the premixed flame to travel from the combustion chamber bifurcation to rush out of the pipe was 15 ms and 3.5 ms, respectively. The stability of the flame also decreased with the increase of NH3 content, the fold area of the flame tip increased, and the flame tip structure became cellular at 81 ms when the NH3 volume fraction was 0.6. With the increase of NH3 volume fraction, Lewis gradually decreases, and the decrease rate of Lewis is basically the same, linearly decreasing. The Lewis of pure ammonia combustion is less than the critical value of 1, and the flame is unconditionally unstable. The stability of the flame of the gas mixture with H2 as the main fuel is with the increase of the volume fraction of H2 first rise and then fall, the most stable is X(H2) = 0.7, Lev = 1.16495, when the volume fraction of CO and NH3 in the fuel are both 0.15. Meanwhile, the main reaction paths in the combustion reaction process are similar for both fuel bodies, but the rate of each reaction path in the NOx formation process is faster when H2 is the fuel body.

Flow-by membraneless electrolyzer designs: A macroporous flow dividing mesh enhances maximum allowable electrode length

The membraneless electrolyzer design promises a low-cost and robust electrolyzer technology, eliminating the disadvantages associated with the membranes/diaphragms in conventional electrolyzers. Flow-by membraneless electrolyzers exploit the Segré–Silberberg effect, where the electrolyte flow between parallel face-to-face cathode and anode forbids the evolving hydrogen and oxygen bubbles to cross over to the other side, while still allowing ionic currents between the electrodes to pass. The removal of the membrane from traditional electrolyzers, and instead exploiting the electrolyte flow itself to function as a gas separator also imposes certain requirements, namely: 1) upward laminar flow and, 2) vertically aligned electrodes. Given the upper limit of the laminar flow regime (Reynolds number, Re ∼ 1800), the admissible length of both vertically aligned electrodes is constrained by the production volume of H2 and O2 at both electrodes. Beyond a certain production rate the evolving gas plume increases in thickness until it reaches the central line dividing the channel between the electrodes. From that point onwards, flow mediated separation of both gases becomes practically impossible. In this work the design constraints of membraneless electrolyzers are investigated by combined multiphysics modeling and mass-balance analysis. Next, a macroporous flow dividing mesh is introduced in the design that allows seamless ionic flow between the electrodes while facilitating a higher electrolyte velocity in the laminar regime. This in turn enables to increase the maximum electrode length (or height) by >50 %. The model based analysis provides important guidelines for further development of membraneless electrolyzers, significantly reducing future experimental optimization efforts.

Health, safety and environmental risk assessment tool applied to site selection for geological hydrogen storage in saline aquifers

Hydrogen (H2) emerges as a pivotal player in the transition to renewable energy sources. To address the seasonal fluctuations in energy dynamics, underground storage emerges as the most efficient approach, and saline aquifers within sedimentary basins as promising repositories for substantial H2 volumes. However, this potential storage solution remains relatively unexplored. Conducting a comprehensive health, safety, and environment (HSE) risk assessment is vital for the technological advancement and public acceptance of geological H2 storage sites. This study introduces a methodology designed to select and classify potential formations based on their HSE risks, offering a safety-oriented approach to identifying suitable storage sites. The proposed methodology underwent testing in two deep saline aquifers located in distinct geological contexts within the Iberian Peninsula. The aim of this study is to establish a foundation for further investigations and implementation of geological H2 storage sites while ensuring safety and adhering to environmental and health standards.

Interaction of aluminum alloys with MKPC and Portland-based cements on the metal-matrix interface

Cementitious matrices are considered for the immobilisation of radioactive aluminium. The processes occurring at the interface between both materials are relevant for the long-term stability of the repository. The present study compares Ordinary Portland cement (OPC), CEM I-type, with alternative Portland blended cement (CEM IV and CEM I + 50% silica fume) and magnesium potassium phosphate cement (MKPC). Al A1050 and Al AA5754, with 3.5% Mg, have been used as reactive metal alloys. Two exposure conditions were employed: (1) water immersion and (2) isolated in sealed plastic films. Long-term corrosion monitoring (Ecorr, icorr and Vcorr) was evaluated to understand the effect of Al reactivity in the matrix. The associated H2 release was quantified to understand the changes at the metal/matrix interface. Furthermore, pore ion concentrations and the pore microstructure were evaluated. The metal/matrix interface alterations were analysed at the end of the tests. The study revealed that after 300 days of water immersion, the CEM I + 50% of silica fume matrix had reduced the pore solution pH down to 10.5 compared to CEM I, which remained high alkaline (pH 12.9), and CEM IV with no significant decreases (pH 12.3). In contrast, MKPC showed the lowest pH (7–9.8). Low Al corrosion rates were found with MKPC, followed by CEM I + 50% SF according to their lower pH. A corrosion product layer of 90-50 μm thickness was observed at the Al/CEM I matrix interface constituted of aluminium and oxygen. Furthermore, enrichment in Al was detected in the matrix (around 1 mm depth), causing the formation of ettringite nodules. Voids were detected at the interface level associated with the high volume of H2 released. The MKPC matrix showed no alteration at the metal/matrix interface due to the lower reactivity of the matrix and lower H2 release. A homogeneous and dense region (30 μm) rich in phosphorous, potassium and magnesium was observed near the metal surface.

Three-Dimensional Modeling of Anion Exchange Membrane Electrolysis: A Two-Phase Flow Approach

Anion exchange membrane water electrolyzers (AEMWEs) are attracting growing interest as a green hydrogen production technology. Unlike proton exchange membrane (PEM) systems, AEMWEs operate in an alkaline environment, allowing one to use less expensive, non-noble materials as catalysts for the reactions and non-fluorinated anion exchange polymer membranes. However, the performance and stability of AEMWEs strongly depend on the alkaline electrolyte concentration. In this work, a three-dimensional multi-physics model considering two-phase flow effects is applied to understand the impact of KOH electrolyte concentration and its flow rate on AEMWE performance, as well as on the current and gas volume fraction distributions. The numerical results were compared to experimental data published in the literature. For current densities above 1 A/cm2, a strongly non-uniform H2 and O2 gas volume distribution could be evidenced by the 3D simulations. Increasing the KOH electrolyte flow rate from 10 to 100 mL/min noticeably improves cell performance for current densities above 1 A/cm2. These results show the importance of accounting for the three-dimensional geometry of an AEMWE and two-phase flow effects to accurately describe its operation and performance.

Effect of cathode ink formulation on the hydrogen crossover and cell performance of proton exchange membrane water electrolyzers

The permeation of H2 through the membranes of proton exchange membrane water electrolyzers (PEMWEs) is a critical safety concern because of the risk of explosion when H2 mixes with O2 at the anode and increases in concentration. In this study, we investigated the modification of the cathode catalyst layer in the membrane electrode assembly as a strategy for achieving the safe operation of PEMWEs. The effects of the polytetrafluoroethylene (PTFE) content and type of ionomer in the cathode catalyst layer on the dissolved H2 concentration, H2 crossover, and electrochemical performance were investigated. The lowest dissolved H2 concentration and H2 permeation rate were achieved when 8 wt% PTFE was used. Consequently, the H2 volume fraction in O2 at the anode was less than 0.88 %. Additionally, using the Nafion ionomer (D520, ion exchange capacity: 1 mmol g−1), H2 volume fractions of 1.27 % and 1.34 % were obtained at 0.08 and 5 A cm−2, respectively. These values are below the lower explosion limit of H2 in O2 (4 %), implying that the PEMWE can be safely operated in the low-to-high current density range under ambient pressure. These results provide key guidelines for the design of high-safety cathode catalyst layers for PEMWEs.

Natural hydrogen extracted from ophiolitic rocks: A first dataset

Serpentinization is an important geochemical process producing natural hydrogen (H2), and mafic and ultramafic serpentinized rocks, typically occurring in ophiolites and peridotite massifs, are major targets for H2 exploration. Understanding the volumes of H2 stored in these rocks is a key step towards establishing the potential of sepentinized systems to host H2 sources and reservoirs. Nonetheless, published data on the concentration of H2 directly extracted from serpentinized rocks are extremely scarce. This work provides a first dataset of H2 extracted by planetary ball mill from 58 rock samples from different ophiolites in Greece, peridotites of the Tekirova ophiolite in Turkey, and chromitites and surrounding talc schist from an Archean-Paleoproterozoic greenstone belt in Brazil. The highest H2 concentrations, from 0.1 mL/kg (considered as a threshold above which artificial H2 by milling is negligible) to 16.2 mL/kg, were found in serpentinized harzburgites or dunites, and in chromitites hosted within serpentinized peridotites. The H2 content of other mafic rocks that are not in contact or influenced by a serpentinized system, mostly basalts, is below 0.1 mL/kg. Serpentinized peridotites represent the logical source rocks of H2 (i.e., hydrogen in peridotites is generally autochtonous) and chromitites, lacking significant olivine and serpentinized minerals, may host H2 derived by the surrounding serpentinized rocks (hydrogen in chromitites is mostly allochtonous). The H2 dataset of this work can be used as a reference for further studies on the capacity of ophiolitic rocks to produce and host natural hydrogen.

Numerical simulation study on hydrogen ammonia mixed combustion in a swirl combustion chamber

Abstract The NO x emissions and combustion performance of pure ammonia and hydrogen-doped combustion (90% NH3 volume fraction and 10% H2 volume fraction) in the cyclone combustion chamber were comprehensively analyzed through numerical simulations under varying thermal operating conditions. The findings reveal that the flame characteristic length in hydrogen-doped combustion surpasses that in pure ammonia combustion, indicating an extended migration of the high-temperature zone after hydrogen doping. Furthermore, the addition of hydrogen results in an elevated exhaust temperature within the combustion chamber, while the Outlet Temperature Distribution Function (OTDF) decreases, signifies an enhancement in the uniformity of temperature distribution at the outlet. Moreover, the reflux zone experiences less impact, and the mixed gas velocity increases following hydrogen doping. Notably, NO x emissions demonstrate a significant decrease after the addition of hydrogen. The average NO emission concentration in pure ammonia combustion, under various operating conditions, is measured at 212.47 mg/m3, representing a 3.51-fold increase compared to hydrogen-doped combustion.

Investigation of differential diffusion in lean, premixed, hydrogen-enriched swirl flames

Hydrogen combustion is a promising alternative to fossil fuel combustion in an effort to reduce our carbon footprint. However, hydrogen combustion is prone to thermodiffusive instabilities largely dependent on differential diffusion, a phenomenon that can lead to higher probabilities of flashback in industrial burners, given hydrogen’s high reactivity and diffusivity. This paper evaluates low-swirl flames of methane and air enriched with hydrogen to highlight the onset of differential diffusion. Testing was conducted in a fully controllable swirl burner, where bulk velocity Uav = 13 m/s and swirl number S = 0.6 were kept constant for each hydrogen–methane blend to isolate increases in flame surface area from increases in turbulence intensity. Furthermore, each fuel blend of hydrogen and methane is evaluated at the same laminar flame speed of SLo = 0.267 m/s to isolate flame stretch effects on the turbulent burning rate. Combined hydroxyl (OH) PLIF and stereoscopic PIV at the National Research Council of Canada were used to analyze the OH fluorescence in a 2D-3C velocity field for each flame condition. High-speed PIV at McGill University was used to resolve local flame phenomena, such as local flame displacement velocity and flame stretch rate. Using these techniques, it can be observed that the flame displaces axially in response to turbulent flame speed while exhibiting increases in flamefront wrinkling. This increased corrugation due to flame stretch is highlighted in the PDFs of local curvature and κSf and is further evidenced by a shift towards positive curvatures (κ> 0) for increasing H2 volume fraction. This trend suggests that there is a strong correlation with increases in turbulent burning rate and positive curvature as a result of differential diffusion, but it is not necessarily a control mechanism of the most forward propagating points proposed by the theory of leading points.

The First Spatially Resolved Detection of 13CN in a Protoplanetary Disk and Evidence for Complex Carbon Isotope Fractionation

Recent measurements of carbon isotope ratios in both protoplanetary disks and exoplanet atmospheres have suggested a possible transfer of significant carbon isotope fractionation from disks to planets. For a clearer understanding of the isotopic link between disks and planets, it is important to measure the carbon isotope ratios in various species. In this paper, we present a detection of the 13CN N = 2 − 1 hyperfine lines in the TW Hya disk with the Atacama Large Millimeter/submillimeter Array. This is the first spatially resolved detection of 13CN in disks, which enables us to measure the spatially resolved 12CN/13CN ratio for the first time. We conducted nonlocal thermal equilibrium modeling of the 13CN lines in conjunction with previously observed 12CN lines to derive the kinetic temperature, H2 volume density, and column densities of 12CN and 13CN. The H2 volume density is found to range between (4 − 10) × 107 cm−3, suggesting that CN molecules mainly reside in the disk's upper layer. The 12CN/13CN ratio is measured to be 70−6+9 at 30 < r < 80 au from the central star, which is similar to the 12C/13C ratio in the interstellar medium. However, this value differs from the previously reported values found for other carbon-bearing molecules (CO and HCN) in the TW Hya disk. This could be self-consistently explained by different emission layer heights for different molecules combined with preferential sequestration of 12C into the solid phase toward the disk midplane. This study reveals the complexity of the carbon isotope fractionation operating in disks.

In-situ plasma assisted lithium-ion battery cathodes to catalytically pyrolyze lignin for H2-rich syngas production

In-situ plasma assisted lithium-ion battery cathodes catalysis was investigated to pyrolyze lignin to H2-rich syngas, oil and char. The effects of temperature, cathode to lignin ratio and plasma current on syngas production were investigated by using the typical ternary cathode NCM111 (LiNi1/3Co1/3Mn1/3O2) as catalyst and adopting dielectric barrier discharge mode. Response surface methodology based on BOX-BEHNKEN design was used to analyze the significance and interactions of process factors on the syngas yield. The conditions of 837℃, 10.4 %, and 185 mA for obtaining high-yield syngas (22.58 %) were more stringent; thereinto, from high to low, the intensity of factors on the yield was temperature, plasma current, and cathode ratio. Furthermore, different cathodes (non-cathode, NCM811 (LiNi4/5Co1/10Mn1/10O2), LCO (LiCoO2), and LMO (LiMn2O4)) were applied to decouple the catalytic effects of three metals in the NCM111. NCM111 enhanced both lignin gasification and carbonization by reducing condensable components, and NCM811 further improved gasification, but LCO and LMO had weaker gasification ability. NCM111 increased H2 volume fraction from 22.35 % to 67.31 %, NCM811 elevated the micro-discharge performance, promoting the hydrogasification reactions between energetic H species and char to produce more CH4, while LCO and LMO tended to produce the CO-rich syngas. Besides, in-situ plasma and its synergy with cathodes inhibited the formation of heavy aromatics and produced some high-value bio-oils rich in light aromatics, in which NCM111 achieved 92.30 % selectivity towards MAHs. High Ni ratio was beneficial for improving the char porosity, and the chars obtained by using NCM811 had a surface area of 409.29 m2/g, and a pore volume of 0.401 cm3/g. Comparably, the degree of catalytic lignin gasification for preparing H2-rich syngas could be ranked as Ni > Co > Mn in the ternary cathode.

Application of a Hybrid Energy System Combining RES and H2 in an Office Building in Lavrion Greece

In the framework of the H2SusBuild project, a prototype hybrid energy system combining Renewable Energy Sources (RES) and hydrogen (H2), as energy storage material and as a green fuel, has been designed, installed and is currently in operation in Lavrion, Greece. The system comprises thin-film PV panels, wind turbines, a water electrolysis unit, a H2 compressor, a micro-CHP unit (PEM fuel cell) and a H2 burner. The aim of this system is to cover the energy needs of a ≈500 m2 office building and to render it a self-sustained, zero CO2 emission installation. The entire site is operated through an advanced Energy Management and Control System (EMCS), responsible for monitoring magnitudes of interest (for example power, energy, stored H2 volume etc.) and managing the synergistic operation of all components based on a custom developed control algorithm. This paper’s aim is to present the results of system operation and evaluate the performance of key components based on data collected during system operation under real conditions. The results show good efficiencies for all major system components and that the implemented control algorithm achieves the zero CO2 emissions goal.

Extractive fermentation as a strategy to increase the co-production of H2 and carboxylates in dark fermentation

Ion exchange resins were used to remove carboxylates from a dark fermentation batch reactor to enhance hydrogen (H2) and carboxylate production. Three anion exchange resins were tested. The A110 resin (macroporous, primary amine functionalized) was selected as suitable for carboxylates removal due to its total exchange capacity (1.25 ± 0.12 mmol/g) and affinity towards butyrate. The extractive fermentation system included a column packed with the A110 resin which was connected to a batch-stirred tank H2 reactor. This setup achieved 3762.9 ± 229.1 NmL H2/L of total accumulated H2 volume, equivalent to a 15.2 % increase compared with the control experiment (3288.6 ± 279.0 NmL H2/L). Also, the molar yields of acetate (0.81 ± 0.11 mol/mol hexose) and butyrate (1.01 ± 0.21 mol/mol hexose) increased by 62.7 % and 71.3 %, respectively. The extractive fermentation system could dampen the inhibitory processes by product accumulation and possibly favor a change in the metabolism of dark fermentation microbial communities that enhanced the production of butyrate and H2 from lactate and acetate. Future studies might guarantee molecular analysis of the microbial communities in extractive fermentation as well testing different extraction systems.

An Experimental Investigation of Hydrogen Production through Biomass Electrolysis

This work investigated hydrogen production from biomass feedstocks (i.e., glucose, starch, lignin and cellulose) using a 100 mL h-type proton exchange membrane electrolysis cell. Biomass electrolysis is a promising process for hydrogen production, although low in technology readiness level, but with a series of recognised advantages: (i) lower-temperature conditions (compared to thermochemical processes), (ii) minimal energy consumption and low-cost post-production, (iii) potential to synthesise high-volume H2 and (iv) smaller carbon footprint compared to thermochemical processes. A Lewis acid (FeCl3) was employed as a charge carrier and redox medium to aid in the depolymerisation/oxidation of biomass components. A comprehensive analysis was conducted, measuring the H2 and CO2 emission volume and performing electrochemical analysis (i.e., linear sweep voltammetry and chronoamperometry) to better understand the process. For the first time, the influence of temperature on current density and H2 evolution was studied at temperatures ranging from ambient temperature (i.e., 19 °C) to 80 °C. The highest H2 volume was 12.1 mL, which was produced by FeCl3-mediated electrolysis of glucose at ambient temperature, which was up to two times higher than starch, lignin and cellulose at 1.20 V. Of the substrates examined, glucose also showed a maximum power-to-H2-yield ratio of 30.99 kWh/kg. The results showed that hydrogen can be produced from biomass feedstock at ambient temperature when a Lewis acid (FeCl3) is employed and with a higher yield rate and a lower electricity consumption compared to water electrolysis.

ALMA Survey of Orion Planck Galactic Cold Clumps (ALMASOP): Discovery of an Extremely Dense and Compact Object Embedded in the Prestellar Core G208.68-19.92-N2

The internal structure of the prestellar core G208.68-19.02-N2 (G208-N2) in the Orion Molecular Cloud 3 (OMC-3) region has been studied with the Atacama Large Millimeter/submillimeter Array. The dust continuum emission revealed a filamentary structure with a length of ∼5000 au and an average H2 volume density of ∼6 × 107 cm−3. At the tip of this filamentary structure, there is a compact object, which we call a nucleus, with a radius of ∼150–200 au and a mass of ∼0.1 M ⊙. The nucleus has a central density of ∼2 × 109 cm−3 with a radial density profile of r −1.87±0.11. The density scaling of the nucleus is ∼3.7 times higher than that of the singular isothermal sphere (SIS). This as well as the very low virial parameter of 0.39 suggests that the gravity is dominant over the pressure everywhere in the nucleus. However, there is no sign of CO outflow localized to this nucleus. The filamentary structure is traced by the N2D+ 3–2 emission, but not by the C18O 2–1 emission, implying the significant CO depletion due to high density and cold temperature. Toward the nucleus, the N2D+ also shows the signature of depletion. This could imply either the depletion of the parent molecule, N2, or the presence of the embedded very-low luminosity central source that could sublimate the CO in the very small area. The nucleus in G208-N2 is considered to be a prestellar core on the verge of first hydrostatic core (FHSC) formation or a candidate for the FHSC.

Simultaneous wastewater treatment and H2 evolution using Mg-Cu galvanic coupling

Contamination-free drinking water and potential sources of green energy are two major concerns of modern society. This article aims to address these through the development of some novel processes and facile experimental setups using analytical grade metals and seawater. Here, the Mg-Cu galvanic coupling process has been successfully used for dye removal from industrial wastewater and for green H2 production. It has been observed that the electrochemical process in the presence of seawater removes ∼100 % rhodamine B, ∼91 % methyl orange and ∼72 % methyl blue dyes within 240 min through an electrochemical reaction. The rate of dye degradation can be enhanced by increasing the area of the counter electrode. The H2 evolution is simultaneously observed from both window and counter electrodes during the dye degradation process. Collected H2 from both electrodes is equivalent to the NTP H2 volume against a meagre loss of metallic Mg dissolved in seawater. In the present work, H2 is produced for the first time by removing the pollutant from wastewater without using any external energy and without hindering the rate of H2 production.

Identifying Noble Metal Catalysts for the Hydrogenation and Dehydrogenation of Dibenzyltoluene: A Combined Theoretical-Experimental Study.

We present a comprehensive theoretical and experimental investigation of the hydrogenation and dehydrogenation of dibenzyltoluene (DBT) using Pd-, Pt-, Ru-, and Rh-supported metal catalysts to identify the optimal catalysts for hydrogen storage and release processes. Our results demonstrated significant variation in the catalytic activity of the metal catalysts. 5 wt % Rh/Al2O3 and 5 wt % Pt/Al2O3 showed the highest activity for hydrogenation and dehydrogenation with the highest selectivity and turnover frequency (TOF), respectively. Conversely, 5 wt % Pd/Al2O3 and 5 wt % Ru/Al2O3 exhibited lower catalytic activity toward full hydrogenation and dehydrogenation. Rh/Al2O3 showed the best catalytic hydrogenation activity with a TOF of 26.49 h-1 and a hydrogenation degree of 92.69% in 2 h, while Pt/Al2O3 exhibited the best catalytic dehydrogenation activity with a released H2 volume of 3755 mL, a dehydrogenation degree of 78.23%, and a TOF of 39.56 h-1 in 2 h. Additionally, we estimated the activation energies for hydrogenation and dehydrogenation to be 67.20 and 82.78 kJ/mol, respectively. Notably, the produced hydrogen gas was of high purity and suitable for use in fuel cells. Density functional theory (DFT) calculations were used to analyze the adsorption structure and reaction energy changes of all intermediate products of DBT on the surface of the chosen catalysts. Our research provides valuable insights into developing efficient catalysts for liquid organic hydrogen carriers.

First assessment of hydrogen/brine/Saudi basalt wettability: implications for hydrogen geological storage

Introduction: Underground hydrogen (H2) storage is a prominent technique to enable a large-scale H2-based economy as part of the global energy mix for net-zero carbon emission. Recently, basalts have gained interest as potential caprocks for subsurface H2 storage due to their low permeability, vast extension, and potential volumetric capacity induced by structural entrapment of the buoyant H2. Wettability represents a fundamental parameter which controls the capillary-entrapment of stored gases in porous media.Methods: The present study evaluates the wettability of basalt/H2/brine system of two basalt samples from Harrat Uwayrid, a Cenozoic volcanic field, in Saudi Arabia. The H2/basalt contact angle was measured using a relevant reservoir brine (10% NaCl) under storage conditions of 323K temperature and pressure ranges from 3 to 28 MPa using the modified sessile drop method. The surface roughness of the basaltic rocks was determined to ensure accurate results.Results: The investigated Saudi basalt samples are water-wet, thereby they did not achieve a 100% hydrogen wetting phase even at 28 MPa pressure. The measured contact angles slightly decrease as pressure increases, thereby pressure did not significantly influences the height of the H2 column.Discussion: We interpret this trend to the slight increase in H2 density with increasing pressure as well as to the olivine-rich mineralogical composition of the Saudi basalt. Thus, from the wettability aspects, Saudi basalt has the potential to store a large volume of H2 (&amp;gt;1,400 m height) and maintain its excellent storage capacity even in deep, high-pressure regimes. This study demonstrates that the basalt rock texture (pore throat radii) and mineralogy control their capacity for subsurface H2 storage.

Experimental investigation of the co-combustion of LPG-hydrogen blends on LPG-fueled systems

The need for sustainable and less pollutant heating solutions has started an energy transition process. Some of the short-term alternatives proposed are based on the use of hydrocarbon-hydrogen blends in conventional combustion systems. In this work, LPG-H2 blends are studied in (a) a gas heater, (b) a water heater and (c) a porous media burner. Thermal and emission behavior, as well as thermal efficiency, are studied for different fractions of H2 in the fuel blend. Stable combustion was sustained for H2 volume fractions up to (a) 44%, (b) 68% and (c) 58%, for the above-mentioned appliances, respectively. Both gas and water heaters showed an overall reduction in thermal efficiency and temperatures as H2 presence was increased. On the other hand, higher temperatures, and thermal efficiencies, along with a 30% reduction in CO emissions were registered for the porous media burner for large H2 fractions in the fuel blend. In conclusion, the technical feasibility of adding H2 to the LPG feed lines of conventional combustion systems was demonstrated, through the stable operation of the 3 appliances studied.