Hydrogen System Research Articles

Hydrogen permeation behavior and mechanisms in nitrile butadiene rubber composites for hydrogen sealing

As the most widely used sealing component in hydrogen systems, rubber seals are affected by hydrogen over long-term service. Hydrogen molecules can dissolve into rubber materials and diffuse through the material. Studies have shown that adding fillers can enhance rubber's performance, improve its compatibility with hydrogen, and reduce the damage caused by hydrogen diffusion. Therefore, this study integrates experimental hydrogen permeation research with finite element modeling for nitrile butadiene rubber (NBR). The aim is to investigate the influence of filler properties on the microstructure, hydrogen permeation behavior, and hydrogen concentration distribution within NBR. Ultimately, the study elucidates the mechanisms governing hydrogen distribution evolution and permeation in NBR under hydrogen environments. The results indicate that the crosslink density of NBR filled with carbon black (NBR-CB) and silica (NBR-SC) is directly proportional to the filler content. NBR with higher filler content exhibits a lower hydrogen permeation coefficient and superior hydrogen barrier properties. In contrast to silica fillers, carbon black fillers demonstrate strong adsorption and a more pronounced barrier effect against hydrogen molecules, thereby enhancing the hydrogen barrier efficiency. The increase in carbon black's hydrogen solubility (from 2.2 × 10-4 to 16.9 × 10-4 cc(STP)·cm-3(polymer)·cmHg-1) effectively reduces the hydrogen permeation coefficient. In contrast, the rise in carbon black's hydrogen diffusion coefficient (from 0.1 × 10-6 to 4.1 × 10-6 cm2·s-1) exacerbates the overall hydrogen permeation coefficient of NBR-CB, thereby intensifying the hydrogen permeation process.

Determining onshore or offshore hydrogen storage for large offshore wind parks: The North Sea Wind Power Hub case

The large-scale integration of renewable energy sources leads to daily and seasonal mismatches between supply and demand and the curtailment of wind power. Hydrogen produced from surplus wind power offers an attractive solution to these challenges. In this paper, we consider a large offshore wind park and analyze the need for hydrogen storage at the onshore and offshore sides of a large transportation pipeline that connects the wind park to the mainland. The results show that the pipeline with line pack storage, though important for day-to-day fluctuations, will not offer sufficient storage capacity to bridge seasonal differences. Furthermore, the results show that if the pipeline is sufficiently sized, additional storage is only needed on one side of the pipeline, which would limit the needed investments. Results show that the policy which determines what part of the wind power is fed into the electricity grid and what part is converted into hydrogen has a significant influence on these seasonal storage needs. Therefore, investment decisions for hydrogen systems should be made by considering both the onshore and offshore storage requirements in combination with electricity transport to the mainland.

A review of challenges with using the natural gas system for hydrogen

AbstractHydrogen, as an energy carrier, is attractive to many stakeholders based on the assumption that the extensive global network of natural gas infrastructure can be repurposed to transport hydrogen as part of a zero‐carbon energy future. Therefore, utility companies and governments are rapidly advancing efforts to pilot blending low‐carbon hydrogen into existing natural gas systems, many with the goal of eventually shifting to pure hydrogen. However, hydrogen has fundamentally different physical and chemical properties to natural gas, with major consequences for safety, energy supply, climate, and cost. We evaluate the suitability of using existing natural gas infrastructure for distribution of hydrogen. We summarize differences between hydrogen and natural gas, assess the latest science and engineering of each component of the natural gas value chain for hydrogen distribution, and discuss proposed solutions for building an effective hydrogen value chain. We find that every value chain component is challenged by reuse. Hydrogen blending can circumvent many challenges but offers only a small reduction in greenhouse gas emissions due to hydrogen's low volumetric energy density. Furthermore, a transition to pure hydrogen is not possible without significant retrofits and replacements. Even if technical and economic barriers are overcome, serious safety and environmental risks remain.

Assessing the 3E performance of multiple energy supply scenarios based on photovoltaic, wind turbine, battery and hydrogen systems

Supplying buildings with cost-effective, eco-friendly and reliable energy by hybridizing sustainable renewable energy systems (RESs) and energy storage methods is becoming increasingly interesting. This study investigates the energy, environmental and economic (3E) effectiveness of three energy supply scenarios (ESSs) designed to meet the electricity and thermal needs of a typical residential building under the Mediterranean climate of Morocco. The first scenario aims to directly supply the energy produced by two RESs, namely photovoltaic and wind systems, to the building and inject the surplus electricity into the grid. In contrast, in the second scenario, the excess solar and wind energy is stored in batteries, while in the third one a proton exchange membrane electrolyzer is used to produce hydrogen and store it for later use through fuel cells. To examine the performance of these scenarios, numerous software, such as EnergyPlus and PVsyst, as well as numerical models are used. The findings indicate that the second and third scenarios can achieve an energy coverage ratio of up to 100 %, whilst the first scenario reaches lower ratio of 52.56 %. Environmentally, the first scenario exhibits the best outcomes with a carbon payback period of one year and a reduction in carbon emissions of 18.21 tCO2e/year. On the other side, the carbon payback period and carbon emissions reduction are 1.66 years and 15.13 tCO2e/year for the second scenario, and 1.14 years and 14.82 tCO2e/year for the third scenario. Economically, the first scenario reveals the best economic findings, followed by the second one, while the third scenario is not economically feasible. The obtained simple payback period values for the first, second and third scenarios are 5.80, 7.89 and 16.30 years, whereas their levelized cost of energy shares are 0.05, 0.09 and 0.21 $/kWh, sequentially. The outcomes of this research significantly contribute to the field by providing crucial information for building owners and professionals to help them in discerning the most efficient ESSs in the 3E prospects, and hence improving their decision-making and implementation processes.

Analysis on failure test and evaluation about refueling receptacle of onboard hydrogen system

ABSTRACT As the key component of the onboard hydrogen system, the service life and failure problem of the refueling receptacle easily leads to the hydrogen leakage accident which give rise to the suffocation, the frostbite, the burns, and the impact injuries. The typical hydrogen leakage accidents include the accidental leakage, the ignition, the deflagration, and the explosion. Therefore, the failure test and evaluation problem about the refueling receptacle is focused on. In this paper, the failure test and evaluation about the refueling receptacle covering the vibration resistance performance, the temperature resistance performance, and the durability was studied. First, the failure mechanisms of the refueling receptacle involving the vibration, the temperature, and the durability based on the vehicle operating conditions were clarified. Second, according to the test experience and the vehicle operating condition, the test methods about the failure phenomenon of the refueling receptacle were established, respectively. Finally, the failure test results of the refueling receptacle were analyzed. The failure of the refueling receptacle may caused by the aging and failure of sealing element, the metal creep aging and material damage, the decline in the contact stress at the low-temperature connection, the loose connection, and the internal structural ectopia.

Hydrogen diffusion and hydrogen embrittlement in iron (steel)

This article examines the diffusion of hydrogen (H-diffusion) and the temperature dependences of the diffusion coefficient of hydrogen (DH) in the metal (M)-hydrogen system. The metal used was iron and low-alloy steel. Taking into account experimental data on hydrogen diffusion in the Fe-H and steel-H systems, the main diffusion parameters were calculated and compared. It is shown that the temperature dependences of the hydrogen diffusion coefficient in metal samples in a one-stage reaction under isothermal conditions are described by the Arrhenius equation. For some M-H systems, experimental data show a deviation of the diffusion coefficient from the ideal one calculated using the Arrhenius equation. This discrepancy can be eliminated using the statistical theory of absolute reaction rates. For the temperature range 25–1250 oС, the pre-exponential coefficient and activation energy of hydrogen diffusion in a body-centered cubic (bcc) lattice of iron (α–Fe) were calculated using the Arrhenius equation. These parameters make it possible to describe the dependence of the rate of hydrogen diffusion in a metal on temperature and to predict the behavior of hydrogen diffusion when changing the conditions of the kinetic process (concentration of substances, pressure, structure, composition, etc.). Tabular values of the calculated pre-exponential factor and activation energy of hydrogen diffusion in previously studied iron-based samples are presented. The temperature dependences of the hydrogen diffusion coefficient in a lattice of iron α–Fe can be divided into low-temperature and high-temperature regions. The calculated diffusion parameters of hydrogen in the metal lattice for the low-temperature 25– 800 oC and high-temperature 800–1250 oC regions differ markedly from each other. In addition, these calculated values are significantly influenced by the structure and composition of the metal. We also studied the diffusion of hydrogen in α-iron using ab initio density functional calculations. Molecular dynamics calculations using transition state theory were used. The calculated diffusion coefficient of hydrogen in α-Fe is consistent with previously obtained experimental data. Hydrogen embrittlement (HE) is considered using internal pressure, hydrogen enhanced localized plasticity (HELP) and hydrogen enhanced decohesion embrittlement (HEDE) theories.

A clean hydrogen and electricity co-production system based on an integrated plant with small modular nuclear reactor

The present study aims to develop a novel configuration of hydrogen and electricity co-production based on a small modular nuclear reactor (SMR) by synergistically integrating the Vanadium Chloride thermochemical (V–Cl) and helium-closed Brayton cycles. For the V–Cl thermochemical cycle, a steady-state simulation model is developed for the first time in the Aspen Plus environment. The entire system is assessed thermodynamically by calculating the exergy destruction rate and exergy efficiency of major components employed in different subsections (nuclear power production, clean hydrogen production, supporting Rankine cycle, hydrogen compression, and storage) of the plant. Various parametric studies are conducted to identify the scope of improvement and evaluate suitable operating parameters that exhibit optimized system performance. It is found that a maximum H2 production rate is achieved when the VCl4 flow is 3.6 kmol/h. A specific hydrogen production rate of 9.63 g/kWh is achieved. The reduction reactor and Deacon reactors are responsible for the highest and lowest exergy destruction with a value of 155.46 kW and 37.60 kW accounting for 49 % and 11.86 % of the overall exergy destruction within the V–Cl cycle. The share of power production from the secondary Rankine cycle in the overall hydrogen compression train is 16.48 %. The parametric study results show that with an outlet helium pressure of 15 bar, the overall work output and electrical efficiency peaked with a value of 4.6 MW and 15.64 % respectively. The overall energy and exergy efficiencies of the proposed system are found to be 16.94 % and 21.42 % respectively.

Simulation analysis of BOP thermal management system for hydrogen fuel cell bus

Hydrogen fuel cell bus has been rapidly developed. As an important part of the hydrogen fuel cell system, its BOP (Balance of plant) mainly includes air compressor, controller, and intercooler. In practical applications, the BOP thermal management system generally includes separated cooling circuits. This study proposes an integrated BOP thermal management system, in which the air compressor, the controller and the intercooler share the same cooling circuit. A 1-D numerical model is built in this paper. On the basis of the model, the 13 possible layout schemes of cooling circuit are investigated. Additionally, the BOP temperature variation characteristics under the UDDS (Urban Dynamometer Driving Schedule) condition are also analyzed. The results indicate that not all layouts of integrated scheme can meet the cooling requirements. To meet cooling requirements of the whole BOP, the coolant should pass through the intercooler first in the serial schemes. As for the parallel schemes, the air compressor should be in a single branch, and the controller and the intercooler should be in series successively at another branch. Under the same total flow rate, the average temperature of BOP in the series scheme can be lower than that in parallel scheme by 8 %. In the three components, the intercooler is most affected by the stack power. This study provides reference for the design of the BOP thermal management system.

Contact electrification characteristics of solid oxygen particle-laden flows in liquid hydrogen transportation

The issue of electrostatic safety in liquid hydrogen systems has garnered increasing attention, especially concerning the potential threat of electrostatic explosions due to the collision-electrification phenomenon of solid oxygen particles formed after air leakage in liquid hydrogen pipelines. To delve into the contact electrification characteristics of solid oxygen particle-laden flows in liquid hydrogen transportation, a mathematical model based on the computational fluid dynamics-discrete element method (CFD-DEM) two-phase flow dynamics has been developed. This model integrates the Hertz contact theory for describing particle collision processes and the condenser model for describing particle collision-electrification. The reliability of this model has been validated in existing literature through its ability to capture the flow characteristics of two-phase flow and the electrification characteristics of particle groups. Using density functional theory to compute the solid oxygen work function and considering the low-temperature properties of liquid hydrogen, a series of numerical studies on the flow sedimentation and electrification characteristics of solid oxygen particle-laden flows in liquid hydrogen pipelines have been conducted. The results indicate that particles carry negative charges after colliding with stainless steel pipe walls, with single charge exchange magnitudes of approximately 10−12C for particle-wall continuous collision processes and 10−14C for particle-particle collision processes, resulting in particle charge-to-mass ratios on the order of tens of μC/kg at the outlet interface. The impact of electrostatic forces on particle motion is significant and cannot be overlooked. Furthermore, the effects of velocity, particle diameter, and pipe diameter on particle charge characteristics have been thoroughly analyzed. At low flow velocities, severe particle settlement occurs, leading to increased collision frequency between particles and walls and significant charge accumulation. Increasing flow velocity can mitigate particle settlement and reduce charge levels. Changes in particle and pipe diameters have a minor impact on particle settlement but can increase single charge amounts with larger particle diameters and intensify particle charging with reduced pipe diameters due to shortened radial travel distances, leading to increased collision frequency. Our study meticulously illustrates the charge characteristics of individual particles and particle groups, providing a theoretical basis for assessing the electrostatic safety of liquid hydrogen transportation systems under extreme conditions.

Sustainable and Tunable Electrochemical CO2 Conversion to Chemicals and Fuels at Industrial Scale Using Metal-Oxide-Based Materials

The most challenging deal we face these years is the need to lower greenhouse gas (GHG) emissions and tackle climate change; though calls to reduce it are growing louder yearly, emissions remain high. CO2 is the key contributor. For this reason, the synthesis of high-added-value products from CO2 conversion is a promising approach to mitigate the problem.1 Among the different alternatives, exploiting CO2 via electrochemical reduction under mild conditions (ambient pressure and temperature) represents an opportunity to support a low-carbon economy.2 The electrocatalytic (EC) CO2 reduction (CO2R) driven by renewable energy can be exploited for the future energy transition, for the carbon storage into valuable products like syngas (H2/CO mixtures), organic acids (formic acid) and chemicals/fuels (C1+ alcohols).3 A big challenge for the industrialisation of this technology is to find low-cost electrocatalysts, efficient reactors and process conditions. In the efforts to develop efficient, selective and stable materials, we have exploited the current knowledge of thermocatalytic CO2 hydrogenation to develop noble-metal-free CO2R electrocatalysts.4 For instance, Cu/Zn/Al synthesised catalyst producing methanol and CO from the CO2 thermocatalytic (TC) hydrogenation (at H2 pressure (P) of 30 bar and temperature (T) > 200 oC) promotes the formation of methanol (⁓32% of FE) during the EC CO2R in a gas-diffusion-electrode system; while operating in the liquid phase, the same catalyst produces syngas with a tunable composition (95% of FE at the most positive applied potential) and other liquid C2+ products (in both cases at ambient T, P).4 On the other hand, Cu/ZnO electrocatalyst has also been tested at industrially relevant current densities in liquid phase configuration.5 We demonstrated through ex-situ characterisations that the presence of ZnO nanoparticles in the mixed Cu/ZnO catalyst plays an important role in forming and stabilising mixed oxidation states of copper and Cu1+/Cu0 interfaces in the electrocatalyst (in bulk and surface). These interfaces seem to promote CO dimerisation to ethanol. Indeed, ethanol was produced with the Cu/ZnO catalyst, reaching ethanol productivity of about 5.3 mmol∙gcat -1∙h-1 in a liquid-phase configuration at ambient conditions. The Cu/Zn/Al and Cu/ZnO electrocatalysts also have been tested in a catholyte-free configuration with an increased selectivity to ethylene, reaching approx. 60% and 70% of FE, respectively. Here, Cu catalyst structure transformed, on average, completely to metallic with a very thin layer of Cu1+ during testing, which seems to promote the selectivity towards C2H4, demonstrating that the reaction pathways for EC CO2R are largely determined by transport limitations rather than only by the intrinsic properties of the electrocatalysts. Our results open a promising path for the prospective implementation of metal-oxide nanostructures for CO2 conversion to the chemicals and fuels of the future. Acknowledgements This work has received financial support by the EU H2020 SunCOChem Project, grant agreement: 862192. References Guzmán, H., Russo, N. & Hernández, S. CO2 valorisation towards alcohols by Cu-based electrocatalysts: challenges and perspectives. Green Chem. 23, 1896–1920 (2021).Romero Cuellar, N. S., Wiesner-Fleischer, K., Fleischer, M., Rucki, A. & Hinrichsen, O. Advantages of CO over CO2 as reactant for electrochemical reduction to ethylene, ethanol and n-propanol on gas diffusion electrodes at high current densities. Electrochim. Acta 307, 164–175 (2019).Guzmán, H., Farkhondehfal, M. A., Rodulfo Tolod, K., Russo, N. & Hernández, S. Photo/electrocatalytic hydrogen exploitation for CO2 reduction toward solar fuels production. in Solar Hydrogen Production Processes, Systems and Technologies 560 (Elsevier Inc., 2019). doi:10.1016/C2017-0-02289-9.Guzmán, H. et al. How to make sustainable CO2 conversion to Methanol: Thermocatalytic versus electrocatalytic technology. Chem. Eng. J. 417, 127973 (2021).Guzmán, H. et al. CO2 Conversion to Alcohols over Cu/ZnO Catalysts: Prospective Synergies between Electrocatalytic and Thermocatalytic Routes. ACS Appl. Mater. Interfaces 14, 517−530 (2022).

(Invited) Hydrogen Detection Strategies to Support H2@Scale--the NREL Sensor Laboratory

Hydrogen represents a major pathway to decarbonize and stabilize the national and international energy industry and select manufacturing markets. To facilitate the development of hydrogen markets, the US Department of Energy initiated H2@Scale to bring together stakeholders to advance affordable hydrogen production, transport, storage, and utilization to increase revenue opportunities in multiple energy sectors. One major impediment to hydrogen implementation is cost. To expedite the use of hydrogen in energy and other markets, the United States announced in 2021 the Hydrogen Shot, which seeks to reduce the cost of clean hydrogen by 80% to $1 per 1 kilogram in 1 decade ("1 1 1"). As the cost of hydrogen drops, new applications will emerge that will require unique configurations of existing equipment and infrastructure, and eventually lead to advances in the generation and utilization of hydrogen. As the hydrogen economy expands, sensors and detection methods will need to adapt to changing infrastructure demands to address the primary targets of health & safety, emissions monitoring, and process control. The NREL Sensor Laboratory is playing a pivotal role in advancing the use of hydrogen sensors and detection methodologies in each of these categories to support DOE’s mission for safe and efficient utilization in emerging markets. Health & safety monitors are required to ensure that operators and facilities can react to unintended hydrogen releases, either as GH2, LH2, or as a constituent of blends (e.g., natural gas or ammonia). Current detection methodologies focus on safety applications to detect near its lower flammable limit (4 vol %), and typically include point sensors in applications such as fixed or mobile detectors (e.g., personal gas monitors). Methodologies amenable for area detection include acoustic, emerging optical imaging methods, and flame detectors.Comparable detection strategies can be utilized for emissions monitoring and quantization, however few methods can simultaneously cover both low (emissions) and high (health & safety) levels. Deployment of emission level detectors will be required to 1) reduce product loss through small but potentially significant leaks from an environmental or cost perspective, 2) reduce downtime of high demand systems by early identification of eminent system failures (leaks through pump or compressor seals indicative of impending failure), and 3) address potential emission monitoring requirements that may be set by regulating bodies. The first two points should be adopted by industry to reduce the cost-of-goods-sold.The third main category for hydrogen detection relates to process control and may be advantageous for many existing applications. Two main applications are emerging. For example, the purity requirements for hydrogen that is dispensed from refueling systems for hydrogen fuel cell electric vehicles (FCEV) is rigorously regulated by the Standard SAE J2719, which prescribes maximum allowable levels of multiple impurities in the hydrogen fuel and must be verified by a regulatory body. Hydrogen contaminant detectors (HCD) integrated to the fueling station can assure this compliance. HCDs must be able operate in 100% H2 backgrounds and be able to distinguish between multiple contaminants at low ppm to low ppb levels.Secondly, as a strategy to decarbonize the natural gas grid, there are proposals to blend hydrogen with natural gas. This blending will affect transport applications (pipeline infrastructure), stationary combustion systems (turbines), and consumer and commercial appliances. In the short-term, hydrogen levels up to 20% are proposed. Variations in the hydrogen level can have dramatic impact on the combustion process and on the potential response of safety sensors. These mixtures may be regulated so that the concentration at a delivery point must be monitored with high precision. However, routine maintenance may introduce background gases such as ambient air (with water) or maintenance gases (introduced with welding processes or adhesive outgassing.) Therefore, the detection methodology must be robust enough to recover or respond to various contaminants.Several reviews can be found in literature addressing sensing and detection technologies, including their limitations and applications. However, for most applications, limitations can be alleviated by combining various detection techniques either through system integration or implementation of machine learning methods (artificial intelligence). Many detection methods already implement some sort of senor fusion, i.e., integrated temperature and humidity sensors allow for compensation methods of point sensors to increase the accuracy and precision of detectors through a wide range of environmental conditions. Similarly, sensing arrays (electronic noses) may implement intelligent algorithms to quantify multiple gasses present in a sample, or simply to identify a single gas in a mixture.In this presentation, we will discuss several applications, highlight their current approach for hydrogen detection, and suggest detection strategies to supplement their limitations.

Detection of hydrogen gas leak using distributed temperature sensor in green hydrogen system

This study addresses the challenges of hydrogen gas detection in pipelines, focusing on the highly flammable nature and low ignition energy of hydrogen. It highlights the limitations of traditional point-based detection methods and emphasizes the need for advanced safety technologies. An integrated approach combining onsite monitoring with Internet of Things (IoT) technology is proposed to enhance systematic safety management and quick leak detection in hydrogen infrastructures. The study reviews various hydrogen detection methods, emphasizing distributed temperature sensing (DTS) techniques to identify leaks through temperature variations. Over nine months of monitoring, the results indicate that DTS temperature variations are more influenced by sensor location than chamber configuration, suggesting that external DTS chamber installation is more effective for leak detection. Additionally, the study integrates Gaussian Process Regression with Machine Learning to predict temperature distribution in pipelines, providing valuable insights for future hydrogen leak detection research.

Facile generation of unsaturated-coordinated and atomically-dispersed hafnium active sites for the highly efficient catalytic transfer hydrogenation of levulinic acid

The sluggish kinetic of the hydrogen transfer reaction pose a significant challenge in developing efficient catalytic transfer hydrogenation (CTH) system for upgrading biomass-derived platform molecules. In this contribution, for the first time, hafnium (Hf) species have been found to coordinate with the hydroxyl groups on halloysite nanotubes surface to construct a single-atom Hf catalyst (Hf@HNTs) with unsaturated-coordinated structure at room temperature. Especially, the Hf(1.7)@HNTs delivered an impressive catalytic performance for the CTH of levulinic acid (LvA) to gamma-valerolactone (GVL) with high turn-over frequency (TOF) of 43.1 h−1 at 160 °C, considerably exceeding that of coordination-saturated HfO2 and state-of-art Hf-based catalysts. Experimental and density functional theory (DFT) studies revealed that Hf(1.7)@HNTs possessed unsaturated-coordinated and atomically-dispersed Hf-O Lewis acid-base pairs, which favored the adsorption and activation of LvA. Moreover, DFT calculations explicitly demonstrated that the energy barriers for the hydrogen transfer between the LvA and hydrogen donor were significantly reduced on the Hf(1.7)@HNTs than that of HfO2.

A spatial ranking of optimal sites for solar-driven green hydrogen production using GIS and multi-criteria decision-making approach: A case of Tunisia

The unpredictable nature of renewable energy sources, such as solar and wind, raises concerns about consistent power supply based on a single type. Green hydrogen presents a promising solution to mitigate the environmental effects of fossil fuels and control the unpredictability of renewable energy sources. Yet, developing green hydrogen systems mandates immense financial commitments, vitally stressing the importance of determining the most appropriate locations before constructing them. As such, the primary purpose of this paper was to propose an initial spatial analysis and prioritize the most suitable locations for installing solar-based green hydrogen systems in Tunisia. For this reason, an exhaustive literature survey was conducted to develop a GIS-based MCDM approach, taking into account technical, topography, environmental, and accessibility criteria. Then, EDAS, ARAS, MOORA, and COPRAS techniques were used to rank the most promising sites resulting from the previous stage. The study revealed that sites of high suitability, primarily in the southeastern and southwestern parts of Tunisia, spanned a total area of 1591 km2 (0.78%). Among such regions, Sfax, Monastir, and Sousse appeared to hold the top ranking as the most suitable locations for solar-based hydrogen. The “most suitable” sites had a hydrogen potential capacity of 9910 Mt per year, with Sfax, Monastir, and Sousse accounting for 14.5% of that capacity. By tapping into this immense potential and embracing the green hydrogen industry, Tunisia has the opportunity to lead in renewable energy adoption. This move could help ensure energy security, reduce dependence on imports, stimulate economic growth, and steer the nation toward a more sustainable and prosperous future.

Large-scale off-grid wind power hydrogen production multi-tank combination operation law and scheduling strategy taking into account alkaline electrolyzer characteristics

This paper proposes a multi-electrolyzer switching scheduling strategy based on the Pelican Optimization Algorithm (POA) to enhance the efficiency of large-scale wind power hydrogen production systems. To validate the effectiveness of the proposed strategy, we analyzed wind power data from three typical days in northern Hebei, China, with a 2.5 MW wind turbine output. We designed three strategies for comparative analysis: a simple start-stop strategy, a rule-based multi-electrolyzer switching strategy, and a POA-based multi-electrolyzer switching strategy. The study results demonstrate that the POA-based strategy exhibits higher hydrogen production efficiency and system stability under various wind conditions. Particularly, in extreme wind scenarios, this strategy significantly reduces the start-stop cycles of electrolyzers, thereby lowering operational costs and improving overall system performance. The main contribution of this study lies in the novel optimization algorithm and its validation through real-world data, demonstrating its effectiveness in large-scale wind power hydrogen production systems. Our findings provide new insights for enhancing the utilization of renewable energy and the economics of hydrogen production systems.

A LoRa-based safety monitoring system for hydrogen compressed natural gas (HCNG)

Abstract Hydrogen compressed with natural gas pipeline for gas mixture delivery is an effective way to realize large-scale, low-cost delivery of hydrogen. The Internet of Things (IoT) technology is one of the important supporting technologies for smart energy transformation, and the low power wide area network (LPWAN) represented by LoRa will play a key role. In this paper, a LoRa-based hydrogen compressed natural gas safety monitoring system is designed, which can collect, transmit, and analyze multiple types of data, such as ambient temperature and humidity, gas concentration, pipeline and equipment vibration, etc., and store the data and configure the alarm thresholds through the cloud server, and finally complete the real-time safety monitoring in the application layer. The system is characterized by high efficiency, high precision, low power consumption, and intelligence, which will have a positive effect on the safe transportation of hydrogen.

Transitioning to a renewable hydrogen system: Optimal infrastructure for self-sufficient hydrogen supply in Austria by 2030

In this study, we employ an optimization model to optimally design a self-sufficient, independent of any imports and exports, hydrogen infrastructure for Austria by 2030. Our approach integrates key hydrogen technologies within a detailed spatial investment and operation model – coupled with a European scale electricity market model. We focus on optimizing diverse infrastructure components including trailers, pipelines, electrolyzers, and storages to meet Austria's projected hydrogen demand. To accurately estimate this demand in hourly resolution, we combine existing hydrogen strategies and projections to account for developments in various industrial sectors, consider demand driven by the transport sector, and integrate hydrogen demand arising from its use in gas-powered plants. Accounting for the inherent uncertainty linked to such projections, we run the analysis for two complementary scenarios. Our approach addresses the challenges of integrating large quantities of renewable hydrogen into a future energy system by recognizing the critical role of domestic production in the early market stages. The main contribution of this work is to address the gap in optimizing hydrogen infrastructure for effective integration of domestic renewable hydrogen production in Austria by 2030, considering sector coupling potentials, optimal electrolyzer placement, and the design of local hydrogen networks.

Solar–Hydrogen-Storage Integrated Electric Vehicle Charging Stations with Demand-Side Management and Social Welfare Maximization

The reliable operation of a power system requires a real-time balance between supply and demand. However, it is difficult to achieve this balance solely by relying on supply-side regulation. Therefore, it is necessary to cooperate with effective demand-side management, which is a key strategy within smart grid systems, encouraging end-users to actively engage and optimize their electricity usage. This paper proposes a novel bi-level optimization model for integrating solar, hydrogen, and battery storage systems with charging stations (SHS-EVCSs) to maximize social welfare. The first level employs a non-cooperative game theory model for each individual EVCS to minimize capital and operational costs. The second level uses a cooperative game framework with an internal management system to optimize energy transactions among multiple EVCSs while considering EV owners’ economic interests. A Markov decision process models uncertainties in EV charging times, and Monte Carlo simulations predict charging demand. Real-time electricity pricing based on the dual theory enables demand-side management strategies like peak shaving and valley filling. Case studies demonstrate the model’s effectiveness in reducing peak loads, balancing energy utilization, and enhancing overall system efficiency and sustainability through optimized renewable integration, energy storage, EV charging coordination, social welfare maximization, and cost minimization. The proposed approach offers a promising pathway toward sustainable energy infrastructure by harmonizing renewable sources, storage technologies, EV charging demands, and societal benefits.

Transactive energy framework in fuel cell based multi-carrier energy hubs based on conditional value-at-risk

The prevalence of peer-to-peer operation among industrial energy hubs is considered a promoting method to enhance local energy autonomy, efficiency, and flexibility. By conducting stochastic programming, this paper aims to minimize the operating cost of multiple industrial energy hubs that trade power and heat energies with each other and utility. Concerning the important role of hydrogen systems, fuel cell-based combined heat and power (CHP) generators are employed within the hubs to increase sustainability. The presence of electric vehicles (EVs) and shiftable loads enhances the flexibility during peer-to-peer operating mode. The trading price for power and heat energies are derived at first by solving a deterministic problem and considering average values for demands and generation. However, to address the uncertainties in renewable generation, electric and heat demands, and electricity prices under operation, scenario-based stochastic programming tries to optimize the expected objective function. Furthermore, the Conditional Value-at-Risk (CVaR) approach is proposed to provide various risk-averse scheduling tactics and measure the risk of each scenario. The results show that the proposed risk-constrained approach reduces the risk and makes cautious decisions about energy resources and trades. In this regard, the expected profit has been reduced by 75%, i.e., from 1636.78 NOK under a risk-neutral case to 414.97 NOK under a risk-averse case to reduce the expected risk in operating cost.

Novel integrated system for power, hydrogen, and ammonia production using direct oxy-combustion sCO2 power cycle with automatic CO2 capture, water electrolyzer, and Haber-Bosch process

Renewable energy-based multigeneration systems for power, hydrogen, and ammonia production suffer from intermittency issues and high production costs. On the other hand, conventional fossil-fuel-based systems yield high levels of CO2 emissions. Thus, to eliminate the intermittency issue with low production costs and near zero CO2 emissions, a novel integrated, efficient, compact, and interactive system for power, hydrogen (H2), and ammonia (NH3) production is developed and investigated in this study. A direct oxy-combustion supercritical carbon dioxide (DOC-sCO2) power plant is integrated with a water electrolyzer (WE) and Haber-Bosch process (HBP) system for the cogeneration of power, H2, and NH3, respectively. The power consumption of the air separation unit (ASU) of the DOC-sCO2 cycle is significantly reduced by the utilization of the oxygen produced from the WE system. Moreover, the cost of ammonia production is minimized by the internal utilization of the nitrogen gas produced by the ASU. Furthermore, the feedwater of the WE system is supplied internally from the DOC-sCO2 power block. In addition, the CO2 emissions of the system are captured to realize near-zero emissions to the ambiance. Based on these features, thorough energy, exergy, economic, and environmental (4E) analyses were performed to evaluate the performance of the proposed system. The obtained results showed an impressive levelized cost of electricity of 3.72¢/kWh, levelized cost of hydrogen of 1.162$/kgH2, and ammonia of 0.197$/kgNH3 at an overall energy and exergy efficiencies of 44.09 %, and 63.6 %, respectively. The system has no emissions of nitrogen oxides (NOx) and reduces the CO2 emissions of the H2 production by 49.6 % and of the NH3 production by 48.8 % compared to the conventional gasification, SMR, and HBP systems, respectively. This research work also provides insights into wet versus dry cooling, part load operation, and the advantages over renewable-based systems in terms of stability, reliability, and economic feasibility.