Hydrogen Supply System Research Articles

Experimental and numerical assessment on co-combustion of hydrogen with ammonia in passive pre-chamber engines

This paper explores the combustion and emission characteristics of TJI ammonia/hydrogen (NH3/H2) dual-fuel engines through experiments and numerical simulations. The NH3/H2 engine operates at 1600 rpm with a manifold absolute pressure of 60 kPa. Two independent hydrogen supply systems enable hydrogen port injection (HPI) and hydrogen direct injection (HDI). The results indicate that HDI yields higher power output compared to HPI. The strong injection ignition ability of the pre-chamber (PC) realizes the stable combustion of the NH3/H2 engine under different ammonia volume share (AVS) conditions. With the increase of AVS, the mixture of HDI in PC is stratified and the jet velocity is significantly reduced. Power output under HDI conditions decreases with increasing AVS. At an AVS of 10 %, the brake mean effective pressure (BMEP) and brake thermal efficiency (BTE) reach maximum values of 3.67 bar and 30.25 %, respectively. The BMEP and BTE increase and then decrease with increasing AVS under HPI conditions. An AVS of 40 % achieves peak power and efficiency. The CA10-90 is always shorter than CA0-10 in the combustion process. At an AVS of 20 %, NO emissions peak and then decrease with increasing AVS, but higher AVS increases unburned NH3 and N2O. Experimental results show that spark timing (ST) has relatively low sensitivity to H2-dominated TJI NH3/H2 combustion. With the increase of AVS to 60 %, the delayed ST will lead to a rapid decrease in power output and a sharp deterioration in combustion stability. When the ST is postponed from 12 °CA BTDC to 4 °CA ATDC, and AVS is 60 %, the COVPmax of the TJI engine increases rapidly from 1.9 % to 13.9 %.

Performance evaluation and energy management strategy of drone methanol reforming fuel cell hybrid power system: A case study

The performance of hydrogen production by methanol steam reforming and high temperature proton exchange membrane fuel cells on drone lacks the comparison of experimental data, resulting in the overall performance improvement of the system is difficult to evaluate. Therefore, the energy management strategy of methanol reforming high temperature proton exchange membrane fuel cell hybrid power system and state machine is designed and optimized. The performance of this system is analyzed and compared with the flight experiment data of a proton exchange membrane fuel cell hybrid UAV. The results show that the SOC of the system can be stabilized between 70 and 80 during the long cruise phase. The test results show that the maximum hydrogen storage mass density of the hydrogen supply system is increased by 67.6%. The flight time of the system under economic cruise flight of the drone is improved by 29.1%–44.9% with different quality of fuel. Under the maximum flight speed of a certain wind speed, the system can meet the flight requirements and increase the flight time by 31.9% and 17.6% respectively under the wind speed of 1.5 m/s and 4 m/s. Its flight time has been greatly improved, and it has great potential as a drone system.

Insight process safety of a hydrogen turbine supply system: A comprehensive dynamic risk assessment using a fuzzy Bayesian network

This study conducts a comprehensive risk assessment for a selected hydrogen supply system within a pilot hydrogen power plant. The assessment begins with hazard identification through Hazard and Operability (HAZOP) analysis, followed by quantification using bow-tie analysis and consequence modeling to evaluate the impacts of credible scenarios resulting from random failures. Furthermore, a fuzzy Bayesian network is employed to address uncertainties inherent in the quantitative approaches and to account for event combinations and dependencies. Sensitivity analysis is subsequently conducted to identify critical events. Utilizing three quantitative approaches, fault tree analysis, the Bayesian network, without and with evidence updating, the probability of the top event is determined to be 4.52 × 10−2/year, 4.50 × 10−2/year, and 4.70 × 10−2/year, respectively. Additionally, the estimated firezone resulting from the explosion's 300 mbar overpressure was 12 m. The findings highlight the significant role of pressure regulator valve and pressure transmitter failures, with posterior probabilities of 0.17/year and 1.90 × 10−3/year, in ensuring the system's safety.

Study on Performance Simulation Matching of One-Dimensional Hydrogen Storage and Supply System for Hydrogen Fuel Cell Vehicles

Article Study on Performance Simulation Matching of One-Dimensional Hydrogen Storage and Supply System for Hydrogen Fuel Cell Vehicles Qi Liu 1,2, * , Biao Xiong 1,3, Yuxuan Liu 1,3, Chuanyu Zhang 1,3, Shuo Yuan 1,2, and Wenshang Ma 1,3 1 College of Mechanical and Vehicle Engineering, Hunan University, Changsha 410082, China 2 Research Institute of Hunan University in Chongqing, Chongqing 401120, China 3 State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body, Hunan University, Changsha 410082, China * Correspondence: author: hnuliuqi@hnu.edu.cn Received: 1 July 2024; Accepted: 12 September 2024; Published: 27 September 2024 Abstract: With the improvement of environmental protection requirements, hydrogen fuel cell vehicles are considered one of the most potential and promising new energy vehicles because of their advantages, such as pollution-free emission, long cruising range, and short hydrogenation time. However, there are still unresolved problems between the storage and supply of hydrogen and the power demand during the operation of hydrogen fuel cell vehicles. In this study, a hydrogen fuel cell vehicle is taken as the research object, and a one-dimensional model is built according to the basic performance parameters so as to explore the operation law of the power performance demand of the hydrogen fuel cell vehicle, simulate the power demand in the actual operation process, summarize the influence of different parameters on the power economic performance of the vehicle, and put forward optimization strategies to improve the power, durability, and fuel economy of the vehicle.

Local Energy Community as a Small Hydrogen Valley – H2LEC

A Local energy community (LEC) is a vertically nested system in energy supply and an ecosystem with joint values and objectives. On-site integrated hydrogen-based systems connected to the grid, and consisting of electrolyser, hydrogen storage and fuel cell system - hydrogen prosumers - provide efficient balancing of local energy consumption and local production of renewable energy that can be extended over annual cycles. There is no transport of hydrogen needed. Thus, the H2LEC – Local energy community with integrated hydrogen systems - represents the carrier of dispersed energy and hydrogen production as a complement of concentrated energy and hydrogen production: on average, H2LEC will predictably achieve at least 75% self-supply. Additionally, with Combined Heat-and-Power systems, coupling to the thermal system adds to energy efficiency. H2LEC represents a virtual socio-economic system based on community values and thus engages initiative, innovation and capital of local actors, new technology start-ups and local industry; and represents opportunities for new disruptive business models. It brings into the energy supply system new players – prosumer who actively trade their flexibilities among themselves and on the external markets, and stimulates new enabling technologies - notably automated close-to-real time trading - thereby boosting end-to-end automated solutions. The H2LEC create the need and the market for smaller integrated hydrogen-based systems ranging from a few kWe for residential homes to a few MWe units for larger industrial companies or local districts with a complete range of capacities in between, for public or tertiary buildings and smaller enterprises. Thus, they provide an opening for participation of SMEs in local and international value chains and will create a strong complementary energy bottom-up pillar and hydrogen supply system locally and in Europe.

Performance analysis of a low-pressure cryogenic vaporizer for liquified hydrogen supply system

In this paper, we theoretically investigated the thermal performance of a low-pressure cryogenic vaporizer for liquified hydrogen supply system. A performance analysis model was developed by the modified effectiveness-NTU method considering the axial conduction and phase change of liquified hydrogen. In the analysis model, a plate-fin heat exchanger (PFHE) was chosen as the type of a cryogenic vaporizer. The inlet temperature and pressure conditions of liquified hydrogen were 20 K and 10 bar, respectively and the outlet temperature condition of hydrogen was a room temperature. Based on the theoretical results, we presented effects of geometric parameters on the performance of the vaporizer under the fixed pumping power condition. Especially, it is shown that the effectiveness of the hot fluid and cold fluid exhibit opposite trends depending on the axial conduction. In addition, we presented the effect of the aspect ratio of microchannels on the effectiveness considering both cases where the microchannel heights of the EGW mixture and hydrogen were either the same or different. Also, we showed the effect of the vaporizer length on the performance of the vaporizer. Finally, geometric parameters that can satisfy the two target performances are suggested.

MATHEMATICAL MODELS OF THE THERMAL PROTECTION COATING OF THE GAS GENERATOR OF THE HYDROGEN STORAGE AND SUPPLY SYSTEM

The article describes the properties of the thermal protection coating of the gas generator of the hydrogen storage and supply system by two transfer functions with Hurwitz polynomials of the third order. Obtaining such transfer functions is based on the solution of the non-stationary heat conduction equation, represented in operator form using the integral Laplace transform, and in which approximating spline functions in the form of second-order polynomials are used. The article gives the solution of the non-stationary thermal conductivity equation, which describes the thermal processes in the heat-protective coating of the gas generator of the hydrogen storage and supply system under the thermal effect of a fire. This solution comes in the operator form for the surface temperature of the heat-protective coating on the side of the gas generator wall. The peculiarity of this decision is the presence of hyperbolic functions of an irrational argument in its composition. The structural and dynamic scheme of the thermodynamic system ‘gas generator wall – heat-protective coating’ is presented, the feature of which is the presence of two entrances. The signal at the scheme’s first input reflects the thermal effect of the fire, and the signal at the second input reflects the thermal state of the gas generator cavity. An equivalent mathematical transition to the description of thermal processes in the heat-protective coating of the gas generator of the hydrogen storage and supply system was carried out. This transition happened due to the use of spline functions, which approximate the hyperbolic functions of the irrational argument and are polynomials of the second order. The article gives a verbal interpretation of the algorithm for determining the transfer functions of the heat-protective coating of the gas generator of the hydrogen storage and supply system and also an example of its implementation. Furthermore, it shows that for the given conditions of functioning of the gas generator heat-protective coating, the relative errors in approximation of hyperbolic functions by second-order polynomials do not exceed 1.7 %, and the average relative error when equivalent replacement of transfer functions does not exceed 3.8 %. Keywords: gas generator, hydrogen storage and supply system, thermal protection coating.

Development of low-carbon technologies in China's integrated hydrogen supply and power system

Hydrogen and electricity are crucial and interdependent energy carriers in China's pursuit of carbon neutrality, suggesting the necessity of utilizing cost-effective low-carbon technologies that facilitate their integrated development. The cost-optimal, provincial level, deployment of low-carbon technologies under this long-term goal remains to be determined. This study employs the REPO model to identify the cost-optimal, low-carbon hydrogen production mixes and the evolution of the integrated power system of China from 2020 to 2050. The integrated planning and operation of hydrogen supply and power systems are explored at the provincial level. The role of high-temperature gas-cooled reactors in this integrated energy system is also analyzed. The results reveal that electrolytic hydrogen would dominate China's hydrogen supply after 2040, with alkaline, proton exchange membrane, and solid oxide electrolyzers produce over 1 Mt of hydrogen in the short term, by 2035, and in 2050. Leveraging the low-carbon heat production of high-temperature gas-cooled reactors in addition to its electricity generation to meet the thermal requirements of solid oxide electrolyzers could boost the output to 4.2 Mt in 2050 and reducing the total system CO2 emissions and costs by 2.28% and 0.05%, respectively. By 2050, the integration of hydrogen supply and power systems also generates up to 2194 TW h of flexible electricity demand by electrolyzers, which raised the renewable energy penetration by 4 percentage points while decreasing the need of flexible natural gas power generations and energy storages. This study is valuable for proposing the analytical framework and performing the provincial-level study of decarbonization of China's integrated hydrogen supply and power system.

EFFICIENCY OF OPERATION OF THE FIRE SAFETY SUBSYSTEM OF THE HYDROGEN STORAGE AND SUPPLY SYSTEM

Hydrogen may become one of the most valuable energy carriers in the 21st century. A big step to this is the safe, compact, and cost-effective storage of hydrogen provided by hydrogen storage systems (HSS). One of the operating system elements of the hydrogen storage and supply system is its fire safety subsystem. The effectiveness of such a subsystem’s functioning depends on a conditional probability that this subsystem correctly recognises the actual state of the hydrogen storage and supply system. We carry out the formalisation of the operation of the fire safety subsystem of the hydrogen storage and supply system in the form of a graph of its states. The study considers three modes of operation of such a subsystem: control, testing, and self-control. We build a weight matrix of the fire safety subsystem states. Its elements include the intensity of transitions from one state to another, the recovery intensity, and the completeness of control and testing. The study shows that the roots of the system of Kolmogorov equations determine the efficiency of the functioning of the fire safety subsystem of the hydrogen storage and supply system. We represent this system of equations in matrix form, with the main matrix having a size of 8×7. Next, we obtain expressions for the roots of such a system of comparisons and construct an expression for the efficiency of the fire safety subsystem’s functioning of the hydrogen storage and supply system. This expression applies to all three modes of operation of such a fire safety subsystem. The considered typical modes of operation of the fire safety subsystem of the hydrogen storage and supply system are control mode, control mode with self-control, and control and testing mode. For each of these modes, we obtain expressions that describe their effectiveness. It is necessary to note that the magnitudes of recovery intensities, in contrast to transition intensities, can vary. We further provide an example of choosing the intensities of restoration of the subsystem during its control using the acceptance criterion for the probability of finding the subsystem in a state corresponding to the fire-hazardous state of the hydrogen storage and supply system. Keywords: fire safety, efficiency, hydrogen storage and supply system.

Modeling and Control of Ejector-Based Hydrogen Circulation System for Proton Exchange Membrane Fuel Cell Systems

Ejector-based proton exchange membrane fuel cells (PEMFCs) are of great interest due to their simplicity and feasibility. Thus, proton exchange membrane fuel cells are considered the most suitable technology for in-vehicle systems, industrial applications, etc. Despite the passive characteristics of the ejector, active control of the hydrogen supply system is needed to ensure sufficient hydrogen, maintain the stack pressure, and ensure effective entrainment. In this research, a novel semi-empirical model is proposed to accurately predict the entrainment performance of the ejector with an 80 kW fuel cell system. According to the precise semi-empirical model, the hydrogen supply system and the anode channel are modeled. Then, a fuzzy logic controller (FLC) is developed to supply sufficient and adequate gas flow and maintain the rapid dynamic response. Compared to the conventional proportional–integral–derivative controller, the fuzzy logic controller could reduce the anode pressure variability by 5% during a stepped case and 2% during a dynamic case.

Design and operation optimization of an on-site hydrogen production and purification integration system for PEMFC

Proton exchange membrane fuel cell (PEMFC) is a promising green and efficient power generation unit using high-purity hydrogen. A high-purity hydrogen supply is significant for the PEMFC. However, previous studies on hydrogen generation for PEMFC mainly focus on simulation, small-scale hydrogen production, or the production and purification in separation. In the present study, an on-site hydrogen supply system with methanol steam reforming and membrane separator is designed and constructed with the goal of providing high-purity hydrogen for a 200 W scale PEMFC. The operation performance of the integrated system is experimentally evaluated, and the influences of critical parameters on hydrogen production are investigated. The response surface method (RSM) is employed to analyze the interaction effect of factors on the hydrogen production rate and optimize the operating parameters. The experimental results show that the integrated system can continuously and stably supply high-purity hydrogen with CO concentration below 10 ppm. The maximum attainable hydrogen flow obtained by RSM is 1460.33 ml/min, which is 24.32% higher than that achieved in the original experiment. The results hold significant implications for revealing the operational characteristics of the integrated system and optimizing the operating parameters.

Determining the functioning efficiency of a fire safety subsystem when operating the hydrogen storage and supply system

The object of research is the fire safety subsystem of hydrogen storage and supply systems. The subject of the study is the efficiency index of the fire safety subsystem of hydrogen storage and supply systems for different modes of its operation. As such an efficiency indicator, the conditional probability that the fire safety subsystem correctly recognizes the actual state of the hydrogen storage and supply system is used. The fire safety subsystem functions under the control mode and under the test mode. Mathematical models of the operation of the fire safety subsystem were built for such modes, based on the use of graph theory. The weight matrices of these graphs include the completeness of control or testing and the intensity of transition of the fire safety subsystem from one state to another. Determination of the effectiveness of such a subsystem – reliability of functioning – is carried out using Kolmogorov’s equations. It is shown that during the testing of hydrogen storage and supply system, the probability of its being in a fire-safe state has a maximum. It is shown that with values of completeness of control (testing) that do not differ from 1.0, the effectiveness of the functioning of the fire safety subsystem is invariant with respect to the mode of its functioning. With values of completeness of control (testing), which are significantly different from 1.0, the functioning of the fire safety subsystem under the testing mode is more effective. The identified features of the functioning of the fire safety subsystem make it possible in practice to implement an optimal or adaptive algorithm for the functioning of such subsystems. For example, with the appropriate selection of testing parameters, the fire safety subsystem provides determination of the location of the hydrogen storage and supply system with maximum probability

DETERMINING THE RECOVERY TIME OF THE FIRE-SAFE CONDITION OF HYDROGEN STORAGE AND SUPPLY SYSTEMS

The fire prevention system can function in passive or active modes. In active mode, such a system implements a set of measures aimed at restoring the fire-safe state of the hydrogen storage and supply system after it is in a fire-hazardous state. The authors consider variants of its functioning for a highly reliable fire prevention system. The first option has the reliability of the fire inspection, which is equal to one, and the second option has the reliability of the fire inspection, which is different from one. Using graphs of the states of the hydrogen storage and supply system, we constructed systems of Kolmogorov equations and derived expressions for the probabilities of finding this system in the corresponding states. The article shows that the time to restore the fire-safe state of the hydrogen storage and supply system in the first variant should not exceed the probability of its being in a fire-hazardous state, reduced to the unit of the intensity of the transition of this system from a fire-safe state to a fire-hazardous state. In the second option, the time to restore the fire-safe state of the hydrogen storage and supply system increases following the law described by a hyperbola of the first order, the argument of which is the reliability of the fire safety inspection of such a system. We have obtained an expression for the reliability of the functioning of the fire prevention system focused on ensuring the fire safety of hydrogen storage and supply systems. We show that the reliability of the functioning of such a prevention system depends significantly on the reliability of the fire-engineering inspection of the hydrogen storage and supply system. We have also derived an expression for the time to restore the fire-safe state of the hydrogen storage and supply system that is determined a priori by the reliability of the fire prevention system functioning, the reliability of the fire inspection, and the intensity of the transition of the hydrogen storage and supply system from the fire-safe to the fire-hazardous state. Keywords: hydrogen storage and supply system, fire prevention, recovery time.

Decision-level fusion detection method of hydrogen leakage in hydrogen supply system of fuel cell truck

The hydrogen supply system is the high-pressure section of fuel cell system, consisting of many valves, pipelines and joints. A hydrogen leak may occur due to the reduced sealing performance or crash accidents. Therefore, a quick and accurate hydrogen leakage detection method is essential to support hydrogen safety. The traditional multisensor-based hydrogen leakage detection method directly classifies the hydrogen leakage fault according to the hydrogen concentration. However, using hydrogen concentrations at local points to describe leak fault severity has significant limitations. A novel hydrogen leakage detection method based on Stacking ensemble machine learning is proposed to classify hydrogen leak rate. The hydrogen leakage simulations are performed to form the database containing a series of hydrogen leakage scenarios. The sensor placement is optimized and the features extracted from hydrogen concentration time series are selected by applying ReliefF algorithm. The model-based hydrogen leakage detection method is analyzed and fused with proposed hydrogen leakage detection method based on Stacking ensemble machine learning by applying decision-level fusion algorithm. Compared with traditional multisensor-based hydrogen leakage detection method, the detection time of proposed multisensor-based hydrogen leakage detection method is shorter under nearly 80% of all scenarios. The classification accuracy of the proposed hydrogen leakage detection method based on Stacking ensemble machine learning and model-based hydrogen leakage detection method is 92.1% and 93.5%, respectively. The probability of class is increased and classification accuracy can be improved through D-S evidence theory.

Long-term planning and coupling optimization of multi-regional natural gas and hydrogen supply systems: A case study of China

Low-carbon transition of energy systems features more natural gas and hydrogen consumption to replace coal and oil. Planning of natural gas and hydrogen supply systems with multiple supply sources, end-consumers, large infrastructures and spatio-temporal mismatches are challenging tasks. In this study, two long-term, multi-regional and monthly time-scale optimization models for natural gas and hydrogen supply systems are developed respectively. China is taken as a case. The natural gas demand will initially increase and then decrease, leading to a premature decommissioning of infrastructure. A coupling model is established to explore the retrofitting of decommissioned natural gas infrastructure for hydrogen supply. Results show that 44.14 % decommissioned pipelines and 34.17 % decommissioned storage facilities of natural gas supply system can be retrofitted, with an annual increase of 63.98 % and 62.80 % in hydrogen pipelines and storage facilities, and a 9.15 % reduction in transition costs.

Key technology and application of AB2 hydrogen storage alloy in fuel cell hydrogen supply system

At present, there is limited research on the application of fuel cell power generation system technology using solid hydrogen storage materials, especially in hydrogen-assisted two-wheelers. Considering the disadvantages of low hydrogen storage capacity and poor kinetics of hydrogen storage materials, our primary focus is to achieve smooth hydrogen ab-/desorption over a wide temperature range to meet the requirements of fuel cells and their integrated power generation systems. In this paper, the Ti0.9Zr0.1Mn1.45V0.4Fe0.15 hydrogen storage alloy was successfully prepared by arc melting. The maximum hydrogen storage capacity reaches 1.89 ​wt% at 318 ​K. The alloy has the capability to absorb 90% of hydrogen storage capacity within 50 ​s at 7 ​MPa and release 90% of hydrogen within 220 ​s. Comsol Multiphysics 6.0 software was used to simulate the hydrogen ab-/desorption processes of the tank. The flow rate of cooling water during hydrogen absorption varied in a gradient of (0.02 ​+ ​x) m s−1 (x = 0, 0.02, 0.04, 0.06, 0.08, 0.1, 0.12). Cooling water flow rate is positively correlated with the hydrogen absorption rate but negatively correlated with the cost. When the cooling rate is 0.06 m s−1, both simulation and experimentation have shown that the hydrogen storage tank is capable of steady hydrogen desorption for over 6 h at a flow rate of 2 L min−1. Based on the above conclusions, we have successfully developed a hydrogen-assisted two-wheeler with a range of 80 km and achieved regional demonstration operations in Changzhou and Shaoguan. This paper highlights the achievements of our team in the technological development of fuel cell power generation systems using solid hydrogen storage materials as hydrogen storage carriers and their application in two-wheelers in recent years.

Experimental Study on Distribution Characteristics and Leakage Detection of Hydrogen Release from Hydrogen Supply System of Fuel Cell Truck

The hydrogen supply system of a fuel cell truck is in a semi-enclosed space where hydrogen is easy to accumulate if a hydrogen leak occurs. The acquisition of hydrogen dispersion behavior data is essential to support the detection of hydrogen release. The purpose of this article is to present the characteristics of hydrogen concentration distribution and delay time of hydrogen leakage detection under different leakage parameters. The experiments have been performed in a hydrogen storage cabin with six hydrogen sensors arranged on the roof to measure hydrogen concentration. During the tests, hydrogen was released into the test cabin through standard leaks. Two different release rates (80 NL/min and 450 NL/min), three different release positions, and six release directions are investigated to analyze the effects on the distribution of hydrogen concentration and leakage detection delay time. This article presents both the experimental facility and results. The experimental results can help optimize the placement of hydrogen sensors and the design of a hydrogen leakage detection system.

Proposal and Fundamental Investigation of Energy Storage and Hydrogen Supply System Using the Lithium

In recent years, variable renewable energy such as solar power and wind power spreads rapidly. At the same time, taking measures against output fluctuations and utilization of surplus electricity become important issues. Conversion of electricity to hydrogen is considered as one of the utilizations of surplus electricity [1]. The hydrogen is stored and can be supplied to the fuel cell vehicles according to demand, regardless of weather or time. However, the disadvantage of hydrogen is its low energy density. Although several methods have been investigated for high-density storage of hydrogen, there are still issues about safety, energy loss, cost, and durability [2].In this study, we propose a new energy storage and hydrogen supply method using lithium (Figure 1). The surplus electricity can be converted by the following reaction, and the energy is stored as the lithium.Li+ + e- → Li (-3.04 V vs. SHE) (1)4LiOH → 4Li+ + O2 + 2H2O + 4e- (0.41 V vs. SHE) (2)The lithium can be stored at room temperature and pressure, and its volumetric energy is higher than that of conventional hydrogen storage methods. When hydrogen is needed, the system can be discharged to produce hydrogen by the following reaction.Li → Li+ + e- (-3.04 V vs. SHE) (3)2Li+ + 2H2O + 2e-→ 2LiOH + H2 (-0.82 V vs. SHE) (4)Since the lithium is highly reactive, discharge reaction with water occurs, and hydrogen can be produced without energy input from the outside. As shown in Equation (2) and Equation (4), charge and discharge reactions at the cathode are different, and this system combines the characteristics of lithium-air cell [3] and lithium-water cell [4]. This system has a potential to utilize the surplus electricity; but it has not been fully evaluated from the viewpoint of hydrogen production [5]. Therefore, present study investigated the characteristics of the discharge reaction and hydrogen production behavior.Figure 2 shows experimental cell. The composite anode was water-stable and had a multilayer structure [6]. LATP (Li1+x+yAlxTi2-xSiyP3-y, Ohara Co., Kanagawa, Japan), which is a water-stable lithium-ion-conducting glass ceramic, was used, along with PEO18LiTFSI as the organic electrolyte. The lithium foil and polyethylene oxide (PEO) membrane were sealed inside the cell to prevent direct contact with water vapor and oxygen. Since the cell resistance depends on the temperature, the composite anode was kept at 70°C. For the cathode, glassy carbon rod was used.Figure 3 shows current-voltage (I-V) characteristics. The cathode potential at low-current discharge is higher than theoretical value (-0.82 V). It was caused by reaction with dissolved oxygen in the electrolyte. As the current value is increased, the cathode potential drops sharply, and many bubbles were observed on the cathode end face. It is thought that oxygen concentration overvoltage increased significantly and the discharge reaction with water (hydrogen production as shown in Equation (4)) was occurred.The volume of the produced bubble was measured with using a sealed cathode and adding a liquid level gauge (not shown in Figure 2). As a result, the measured volume showed good agreement with the theoretical hydrogen volume produced by the reaction of Equation (4). It is considered that the reaction shifts to hydrogen production and the effect of dissolved oxygen can be negligible at sufficiently low cathode potential (i.e. high current discharge).The efficiency of this system was estimated by using the obtained experimental results. Generated electricity and enthalpy of produced hydrogen was calculated. When a 20 μA discharge test was conducted by using experimental cell, the discharge efficiency and conversion rate to hydrogen were 30% and 39%, respectively. For comparison, the experimental cell was converted to the lithium-air battery mode and discharged at 20 μA. The discharge efficiency was 56%. Considering the conversion ratio of lithium to electricity and hydrogen, the proposed hydrogen supply system using the lithium can utilize the variable renewable energy.

INFORMATION CAPABILITIES OF THE TRANSITION FUNCTION OF THE HYDROGEN STORAGE AND SUPPLY SYSTEM GAS GENERATOR TO ASSESS ITS FIRE HAZARD LEVEL

To estimate the level of fire hazard of hydrogen storage and supply systems, it is advisable to use reliability indicators, in particular, of their core element, which is a gas generator. Such indicators include indicators of amplitude and phase reliability of the gas generator, which are determined through the Laplace function. The arguments of this function are the relative errors of the parameters of the gas generator, which are determined by its transition function. Three options for determining the parameters of the gas generator have been developed, the feature of which is obtaining information about its parameters at two a priori given moments. The magnitudes of these moments do not exceed the time of the transient process. In the a priori specified moments, the values of the transient fraction are measured (option 1), and the values of its derivative (option 2) or the value of the integral of the transient function (option 3) are additionally measured. Algorithms for processing the received information have been developed for all options, the implementation of which ensures the determination of gas generator parameters. In terms of its structure, the second option for determining gas generator parameters is the simplest, which has 1.5 times fewer arithmetic operations compared to the first option. In addition, the second option for determining the parameters of the gas generator is invariant to the value of the time parameters that determine the measurement moments. The results of determining the parameters of the gas generator and their nominal values are used to determine the arguments of the Laplace functions. We have specified that when determining the parameters of the gas generator, the complexing method can be used, which involves the implementation of all three information processing algorithms. As an example of the second option of determining gas generator parameters, the structural diagram of the algorithm is presented. We have emphasised that the implementation of the developed algorithms for determining the parameters of the gas generator has no subjective factor associated with the use of expert judgments. Keywords: gas generator, fire hazard level, transition function.

A new design method for the vortex hydrogen circulating pump system

Against the backdrop of “carbon peak and carbon neutrality,” the hydrogen and fuel cell vehicle industry are rapidly developing. Within the on-board hydrogen supply system, the hydrogen circulation pump serves as an essential component of the hydrogen fuel cell system. The spiral disk, as a core part of the hydrogen fuel cell system’s vortex hydrogen circulation pump (VHCP), plays a crucial role in determining the performance of the hydrogen circulation system in hydrogen fuel cell vehicles. To meet the requirements for high-performance and high-reliability development of the hydrogen circulation pump, the VHCP scheme is adopted as the choice for the hydrogen pump solution. Through the magnetic suspension and no connection shaft structural design, the feasibility of applying the high speed and high flow hydrogen turbine was initially validated. Utilizing Fluent analysis software and high precision performance test bench, a comprehensive three-dimensional numerical simulation of the turbine design under various operating conditions was conducted and performance test verification, demonstrating that the performance meets the required specifications. By conducting research in both strength optimization design and performance requirement, two major technical challenges in turbine pump application were overcome. Combined with the experimental results of the turbine medium, it is concluded that the vortex pump can meet the flow and pressure rise under the premise of low power consumption in the hydrogen circulation system so as to perfectly increase the hydrogen return amount. Based on these findings, recommendations are proposed for the future development direction of hydrogen supply systems in hydrogen fuel cell vehicles.