On-board Storage Research Articles

Hydrogen Leakage Risks and Mitigation Measures in Large Underground Garages

Abstract Hydrogen fuel cell vehicles, characterized by zero emissions, pollution-free operation, and high efficiency, have emerged as a key focus in the development of the global automotive industry. The operating pressure for onboard hydrogen storage tanks commonly ranges from 30 to 70 MPa. Due to hydrogen's wide combustion and explosion concentration range and its exceptionally rapid combustion rate, there is a high risk of explosions and other accidents once equipment failure happens during storage and transportation. The research presented in this paper focuses on the analysis of hydrogen leakage from storage tanks in an underground garage using FLUENT simulations. The findings reveal that released hydrogen forms a jet from the storage tank under high pressure, dispersing along the ceiling upon reaching it and accumulating at the edges and corners. Moreover, larger leakage ports on the storage tank result in a greater mass flow of hydrogen, leading to an expanded diffusion range of the hydrogen cloud and decreased local concentration. To mitigate the risk of hydrogen combustion and explosion within the garage, this study introduces 16 extraction vents on the garage ceiling and 6 natural vents on its sides. The validation of the proposed hydrogen risk mitigation measures demonstrates their effectiveness in reducing the concentration and range of flammable clouds within the garage, especially when dealing with larger leakage ports.

Life prediction of on-board supercapacitor energy storage system based on gate recurrent unit neural network using sparse monitoring data

With the increasing use of supercapacitor in transportation and energy sectors, service life prediction becomes an important aspect to consider. As the aging process of onboard supercapacitors is closely related to practical working conditions, the actual service life may be inconsistent with the cycle life measured in the laboratory. However, the low-quality onboard monitoring data recording the historical working conditions is usually sparse and fragmented, making it difficult to extract valuable information. In our previous study, we successfully obtained the characteristic parameters from sparse and fragmented data, whereas those characteristic parameters change periodically and couldn't be used directly for life prediction. In this paper, we firstly extract the degradation trend term of supercapacitor by a composite sine and polynomial time series decomposition model from the characteristic parameters. Secondly, in order to make up for the lack of data, a GRU network is designed to generate more sample data which is in consistent with historical data evolution trends. The combination of input characteristic variables including the extracted historical characteristic capacitance C, temperature T and the time fitting sequences CtD are selected to improve the accuracy of GRU predictions. The predictive error of the characteristic capacitance C is 2.36 %. Finally, the life prediction of on-board supercapacitors based on actual working conditions is realized.

Analysis of Dual, Onboard Storage and Separation of Biogas in Carbon-Based Adsorbed Gas Systems

Analysis of Dual, Onboard Storage and Separation of Biogas in Carbon-Based Adsorbed Gas Systems

Ca-decorated holey graphyne for reversible hydrogen storage: Insights from DFT analysis

We theoretically examine the hydrogen storage capabilities of a newly synthesized carbon allotrope known as holey graphyne (HGY). HGY exhibits weak interaction with H2, making it unsuitable for storage, thus prompting surface modification. Ca binds to HGY with a binding energy of −2.03 eV and experiences a diffusion energy barrier of 1.49 eV. The supercell of HGY accommodates six Ca atoms, and each Ca atom binds five H2 with an average binding energy of −0.27 eV, resulting in an uptake capacity of 12.07 wt% and desorption temperature of 331K at 5 bar. AIMD simulation and positive phonon frequencies confirms thermal and dynamic stability of Ca-decorated HGY. RDG analysis reveals electrostatic interactions between Ca and HGY, and van der Waals interactions between H2 and Ca. Thus, Ca-decorated HGY shows exceptional uptake capacity, desirable adsorption energy and desorption temperature, making it a suitable material for on-board reversible hydrogen storage in light vehicles.

Investigation of Onboard Power Generation Method Using Waste Energy at Altitude Conditions

Abstract Demand for increased onboard power generation on small aircraft is ever growing due to increased electrical power demand. The objective of this study is to investigate onboard power generation using waste energy at various altitude and ambient conditions. Experiments were performed on a 2-liter turbocharged direct-injection intermittent combustion engine fueled with jet fuel (F-24). The turbocharger has an integrated motor-generator system that is designed to generate electricity using the enthalpy in the engine exhaust, or to use as a motor to rotate the turbocharger using the energy stored in onboard energy storage device. An electrically actuated wastegate was used to control useful exhaust flowrate that is used to generate electricity. An external power supply system was used to emulate the energy storage. The engine was installed in the US DEVCOM Army Research Laboratory?s altitude chamber in which absolute outside air pressure was controlled up to 37.6 kPa to simulate the altitude conditions up to 7,620 m (25,000 ft). Three different ambient conditions were selected to represent International Standard Atmosphere (ISA), polar, and tropical conditions. Based on the experimental results, a response surface model was developed to predict the power generation of the motor-generator integrated turbocharger using waste energy as a function of altitude, engine power, and the wastegate position. The result from this study provides an insight into onboard power generation method using waste energy at altitude conditions.

Enhancing hydrogen storage efficiency: Computational insights into scandium-decorated 2D polyaramid

This study explores hydrogen storage in 2D polyaramid (2DPA) and its enhancement via scandium decoration for onboard storage in fuel cell vehicles. Sc decoration in 2DPA is accompanied by a net 1.6 e charge transfer from Sc to 2DPA. Hydrogen binding in 2DPA + Sc proceeds with a net charge transfer of 0.32 e from Sc towards H2. 2DPA + Sc demonstrates a maximum hydrogen loading capacity of 8.589 wt% with an average adsorption energy of −0.376 eV/H2. These findings meet the stipulated criteria by the US Department of Energy for solid-state hydrogen storage in light-duty vehicles. Feasibility studies were conducted considering practical limitations in transition metal-modified carbon nanomaterials, including Sc-Sc clustering tendencies, stability, and hydrogen desorption behavior via ab initio molecular dynamics simulations, phonon dispersion, and diffusion studies. The highest barrier height for hydrogen desorption from 2DPA + Sc is 0.48 eV, and desorption is predicted to occur at 412 K (5 bar) indicating possibility of room temperature and reversible hydrogen storage. Our findings indicate that 2DPA + Sc is a promising hydrogen storage substrate material and should be explored in experimental trials.

Onboard amino acid salt-based CO2 integrated absorption and mineralization: Kinetics, mechanism, economics and life cycle

The International Maritime Organization's ambitious greenhouse gas reduction strategy is driving efforts to capture carbon from marine engine exhaust gas. Onboard carbon capture and storage (OCCS) faced significant challenges, particularly due to the substantial thermal energy requirements during the capture process and the complexities of transporting captured CO2 to storage facilities. The integrated CO2 absorption and mineralization (IAM) process, a thermodynamically downhill process, offered a potential solution for rapidly absorbing and sequestering CO2 in-situ. In this study, a single-step amino acid salt-based IAM process was employed to address carbon emissions from ships. Under optimized conditions, over 85 % of the CO2 in simulated marine engine exhaust gas was captured and completely converted to calcium carbonate using a potassium glycinate/ calcium hydroxide blend absorption slurry. This approach tackled the key challenges of effectively capturing CO2 from ships, while minimizing energy consumption, and ensuring the safe storage of the captured CO2. A case study on a 1700 TEU container ship evaluated the economic benefits and global warming potential of the OCCS system, indicating that capturing CO2 from ships could be profitable (87.2 $/ton CO2) and calcium carbonate could be a commercial product. Despite high-carbon-intensity absorbents (such as calcium hydroxide) partially offset the carbon reduction effort, resulting in a decline of carbon capture efficiency from 85 % to 44 %. The proposed amino acid salt-based IAM method could be considered a promising technique for reducing carbon emissions from ships, providing a feasible technical means for achieving the International Maritime Organization's ambition strategy for zero-carbon shipping.

Cathode-less RF plasma thruster design and optimisation for an atmosphere-breathing electric propulsion (ABEP) system

Atmosphere-breathing electric propulsion (ABEP) is a concept that ingests residual atmospheric gases as a source of propellant for an electric thruster, removing the need for onboard propellant storage. This would enable continuous low-thrust drag compensation, extending the lifetime of spacecraft in Very-Low Earth Orbit (VLEO); <250 km. VLEO is an appealing region for spacecraft operations, enabling new remote sensing missions with improved radiometric performance and spatial resolution, whilst reducing size, mass and power requirements, as well as mission cost. A preliminary design review and optimisation is therefore conducted for an ABEP system that uses the cathode-less radio frequency (RF) plasma thruster from Technology for Innovation & Propulsion (T4i) S.p.A. This removes the issue of thruster erosion by means of magnetic confinement and offers reduced susceptibility to varying atmospheric composition. A semi-empirical oxygen-nitrogen global source model (GSM) has been developed which considers the volume-averaged flux, momentum, and energy balance of the RF discharge. This includes a detailed chemistry model for the complex electron-molecular reactions and energy-loss channels of air plasma in the ionisation chamber. The GSM is coupled to an analytical model of flux balance for an air intake, verified by Direct Simulation Monte-Carlo (DSMC) simulation, to consider its design for maximum collection efficiency. This is then utilised in a robust multi-objective optimisation of the ABEP system, accounting also for spacecraft aerodynamics and power requirements.

Study on the rapid decompression rate of PA6 liner material of type IV on-board hydrogen storage cylinders

Investigations were carried out in this paper to study the influence of rapid decompression rate on the polyamide 6 (PA6) liner materials through experimental and numerical methods. Firstly, hydrogen permeation tests at different pressures were conducted to obtain the functions representing the trend of permeation parameters with the pressure. Then decompression tests at different decompression rates had been carried out to get whitening specimens which would be observed using scanning electron microscopy (SEM). Cavitation was found and the variety of the number of cavities with the decompression rate was recorded. It was found that the faster the decompression rate was, the higher the number of cavities in the specimen was. Thirdly, to determine the hydrogen concentration throughout the specimen and numerically check if cavitation occurred at various decompression rates, a 2D finite element model was established which introduced the permeation parameters as functions of pressure but not temperature, as another numerical model indicated the temperature field of specimens changed little. Then an approach was proposed to successfully implement the risk assessment of cavitation, and the liner material was considered as elastoplastic neglecting its viscoelasticity-viscoplasticity. Based on the assumptions and experimental conditions in the study, the Mises yield criterion was successful to assess the cavitation risk, and the approach was verified as the analysis results about the cavitation agree well with the SEM observations. In the end, based on the approach, it could be concluded that 11h was the critical safe decompression time for the PA6 material in this study, and the decompression rate was 7.95 MPa/h. The approach in this study can also be used as guidelines for the cavitation risk assessment of other systems and materials undergoing rapid decompression.

Design and optimization of a high thrust density air-breathing pulsed plasma thruster array

For satellites in Very Low Earth Orbit (VLEO) or the upper atmosphere, Air-Breathing Electric Propulsion (ABEP) can be used to counteract the drag effects of the atmosphere or provide attitude control without the need for onboard propellant storage. The Dense Plasma Focus (DPF) inspired the design of an ABEP Pulsed Plasma Thruster (TAMU PPT) which takes advantage of the simplicity, scalability, and high energy density of the DPF. This work details the design and testing of a PPT for use on satellites in the upper atmosphere. Testing was conducted at a variety of pressures and pulsing energies to determine which conditions provide maximum thrust and thrust to power ratios (TPR). It was found through single pulse experiments that a pressure of 6.3 hPa (corresponding to an altitude of about 35 km) and an energy per pulse of 9 J yield a TPR of 21 mN/kW. High frequency operation at 20 Hz in similar conditions showed a TPR of up to 28 mN/kW with a corresponding thrust of 4.8 mN. High speed imaging of the plasma plume found plasma velocities in excess of 2 km/s and identified metal ejecta with velocities up to 350 m/s. The pinching phenomenon associated with a DPF was also observed and a plasma jet velocity up to 50 km/s was recorded. The TPR of the TAMU PPT demonstrated in this work is comparable to that of other ABEP thrusters, however the TAMU PPT has an advantage when comparing thrust density. The TAMU PPT has a thrust density between 4.8 and 19 mN/cm2 while other ABEP thrusters have thrust densities between 0.019 and 0.36 mN/cm2.

Greenhouse gas emissions of shipping with onboard carbon capture under the FuelEU Maritime regulation: A well-to-wake evaluation of different propulsion scenarios

International shipping has extended its decarbonization strategy to reduce greenhouse gas emissions beyond onboard CO2 emissions. Onboard carbon capture and storage systems are being investigated as a potential solution for fossil-fueled ships, however there is a lack of knowledge on the reduction of well-to-wake greenhouse gas emissions that could be enabled. Considering the ambitious emission reduction targets, this may lead to inaccurate estimations of the future fuel mix in the maritime sector and the market share of marine engines. This study defines nine ship propulsion scenarios based on combinations of fossil fuels and marine engines. To better understand the greenhouse gas emission reduction of onboard carbon capture, this study calculates the well-to-wake greenhouse gas intensity of each scenario with and without onboard carbon capture and storage from the ship’s main engine(s). Deploying onboard carbon capture and storage systems notably reduces the tank-to-wake greenhouse gas intensity (54–68 % depending on the scenario). Contrary to onboard emissions, oil-fueled ships with onboard carbon capture and storage are found to be less greenhouse gas intensive and more cost-effective than LNG-fueled ships. The four-stroke oil-fueled engine achieves the lowest well-to-wake greenhouse gas intensity of 38.31 gCO2eq/MJ, while the four-stroke LNG-fueled engine has the highest intensity of 50.34 gCO2eq/MJ. The greenhouse gas emission levels enabled by onboard carbon capture from the main engine would allow fossil-fueled ships to comply with the FuelEU Maritime greenhouse gas intensity requirement until 2044. To be compliant in subsequent periods, onboard carbon capture and storage systems will need to consider carbon capture from the auxiliary boiler and generator and higher capture rate, as well as measures to reduce upstream emissions from fossil fuel production and transport.

Modeling and SOC estimation of on-board energy storage device for trains under emergency traction

The sudden interruption of train power supply in an extreme environment will seriously threaten the safety of passengers and affect the operational efficiency of the railway system. In this case, the focus of attention becomes a method of running the train to the nearest rescue point based on the limited capacity of the on-board emergency energy storage device. Therefore, this paper reports research on the state of charge (SOC) estimation of train energy storage equipment to optimize the emergency traction strategy and energy utilization rate of trains to the maximum extent. First, with the emergency power supply of on-board lithium titanate batteries, the energy flow model of train emergency power supply is constructed for the first time. Second, based on the second-order equivalent circuit model and considering the utilization of regenerative braking energy, the relationship between battery capacity and open circuit voltage (OCV), temperature, current and SOC are constructed through experimental data, which significantly improves the accuracy and robustness of SOC estimation in complex and variable environments. Then, to effectively eliminate the impact of environmental on the estimation especially in the case of extremely low temperature (−20 °C), online model parameter discrimination and SOC estimation of lithium batteries are realized by combining recursive least squares with an optimal forgetting factor (FRLS) algorithm and a new temperature forgetting factor based adaptive extended Kalman filter (TFFAEKF) algorithm. The experimental results show that the proposed method achieves accurate SOC estimation, and the maximum error is less than 1% at different temperatures.

Maximizing Onboard Hydrogen Storage Capacity by Exploring High-Strength Novel Materials Using a Mathematical Approach.

Hydrogen fuel holds promise for clean energy solutions, particularly in onboard applications such as fuel cell vehicles. However, the development of efficient hydrogen storage systems remains a critical challenge. This study addresses this challenge by exploring the potential of high-strength novel materials, including glass, to maximize onboard hydrogen storage capacity. A mathematical approach was employed to evaluate the feasibility and efficacy of various high-strength materials for hydrogen storage. This study focused on capillary arrays as a promising storage medium and utilized mathematical modeling techniques to estimate the storage capacity enhancement achievable with different materials. The analysis revealed significant variations in storage capacity enhancements in different high-strength novel materials, with glass having promising results. Glass-based materials demonstrated the potential to meet or exceed US Department of Energy (DOE) targets for both gravimetric and volumetric hydrogen storage capacities in capillary arrays. By leveraging a mathematical approach, this study identified high-strength novel materials, including glass and polymers, capable of substantially improving onboard hydrogen storage capacity: 29 wt.% with 40 g/L for quartz glass and 25 wt.% with 38 g/L for Kevlar compared to 5.2 wt.% with 26.3 g/L from a conventional type IV tank. These findings underscore the importance of material selection in optimizing hydrogen storage systems and provide valuable insights for the design and development of next-generation hydrogen storage technologies for onboard applications.

A structural mechanics analysis on a Type IV hydrogen storage tank during refueling and discharging

High-pressure hydrogen gas, as a power generation fuel widely used in transportation, has significantly contributed to the development of hydrogen fuel cell electric vehicles. However, obvious temperature rise and drop during fast refueling and discharging cause serious safety risk to the structural stability of on-board hydrogen storage tank. The American Society of Automotive Engineers SAE J2601 and the international standard ISO 15869 strictly stipulate that the operation temperature range of hydrogen storage tank varies from −40 °C to 85 °C. In this study, a finite element mechanics model was constructed using ACP and Static Mechanical software to better understand the deformation, stress, strain, and failure modes experienced by a Type IV tank during charging and discharging. Detailed parameters such as ply angle, ply thickness, mesh generation, and boundary conditions, were extensively elucidated. The results indicate that the high temperature and pressure generated during fast fueling of the storage tanks are less likely to cause yield failure of the inner, outer layers and plug, but the stress concentration caused by low temperature and high pressure may lead to the fracture rupture of internal polyethylene materials. Aluminum alloy plug, serving as sealing devices for the tank, are most susceptible to yielding failure under coupled conditions. The mechanical load reaching the yield stress of the plug is approximately 85 MPa with the nominal working temperature of 85 °C. Additionally, the maximum stress on the outer layer can be reduced by adjusting the circumferential layer direction from 90° to 70° or by optimizing the orientation of the maximum stress layer increasing it by 110°. The present study can offer new insights into the dynamic loading behavior of the Type IV tanks during fast charging and discharging, and may provide technical references for optimization design of the tank structures.

From nanorods to nanoparticles: Morphological engineering enables remarkable hydrogen storage by lithium borohydride

Nanostructured LiBH4 with greatly improved de-/hydrogenation thermodynamics and kinetics has been attracting the ever-growing interest for on-board hydrogen storage applications. However, it is challenging to controllably fabricate various nanostructures of LiBH4 due to its strong reducibility, high chemical activity and sensitivity to water and oxygen. Here, we demonstrate the very first success in tailoring the nanoscaled LiBH4 morphology from nanorods to nanoparticles by using few-layer graphenes (FL-Grs) as supporters. The presence of 30 wt% FL-Grs is optimal because it contributes not only substantial nucleation sites for LiBH4 nanoparticles but also sufficient catalytic activity for hydrogen storage in LiBH4. The resultant LiBH4-30 wt% FL-Grs displays 20–50 nm-sized particles in morphology, which enables the complete reversible storage of 7.2 wt% H2 starting from 230 ºC for desorption and 190 ºC for absorption along with a stable cyclability, greatly superior to pristine sample and even the nano-LiBH4/FL-Grs mixture. The somewhat particle growth as well as the segregation and isolation of B and LiH with cycling is reasonably responsible for the gradually slowed desorption/absorption kinetics. This important insight guides the design and development of nanostructured LiBH4-based composites featured high capacity and long life by combining nanometer size effect and catalytic effect.

Safety evaluation on ammonia-fueled ship: Gas dispersion analysis through vent mast

The maritime industry is exploring ammonia as an alternative fuel to reduce greenhouse gas emissions. However, the high toxicity of ammonia poses significant safety challenges for onboard handling and storage. This study investigates ammonia dispersion and toxicity levels from vent mast releases on ships, aiming to enhance safety measures for future ammonia-fueled vessels. Using CFD analysis on a 31,000-dwt general cargo ship model, the research examines various release scenarios, considering regulatory requirements, vent mast design, and environmental conditions. Results show that direct ammonia release from the vent mast poses fatal risks to the crew in the accommodation area and on adjacent ships, regardless of current regulatory stipulations. The study recommends installing an ammonia-catching system to reduce concentrations to safe levels of 30 ppm before release. These findings offer crucial insights for improving the safety of using ammonia as marine fuel through risk assessment and management.

Numerical simulation of high-pressure jet fire in on-board hydrogen storage cylinders under fire conditions

Hydrogen fuel cell vehicles (HFCVs) may cause fires in the event of an accident. When the high-pressure hydrogen storage cylinders are exposed to fire for a long time, there will be a risk of catastrophic consequences such as leakage, jet fire and explosion. Fire test is the main method to study the safety performance of hydrogen storage cylinders. During the firing process, the wall and internal temperature of the hydrogen storage cylinder rise gradually, and the thermally activated pressure relief device (TPRD) of the cylinder reaches a certain temperature and then releases high-pressure hydrogen to prevent the cylinder from bursting. As the hydrogen storage cylinder is in the fire environment, the release of high-pressure hydrogen will be ignited to form a jet fire and cause damage to personnel and equipment. In this paper, CFD software Fluent was used to numerically simulate the local fire test of the hydrogen storage cylinder with high-temperature air as the fire source. The variation law of cylinder wall temperature, gas temperature and pressure inside the cylinder, and the activation of TPRD were analyzed. At the same time, on the basis of the fire test simulation, a high-pressure hydrogen jet fire simulation numerical model caused by the TPRD action was established. The velocity field, temperature field and hydrogen concentration distribution of the jet fire were obtained, and the overpressure generated by the jet fire and the flame length size were analyzed. The results show that the high-pressure hydrogen released by TPRD was ignited under the fire condition to produce a jet flame and generated an overpressure in the jet direction, and the influence range of the overpressure was smaller than the influence range of the jet flame.

Onboard carbon capture and storage (OCCS) for fossil fuel-based shipping: A sustainability assessment

Limiting the carbon intensity of maritime transport is crucial to meet 2050 net-zero targets. Onboard carbon capture and storage (OCCS) offers a practical short-term solution for reducing shipping-related CO2 emissions until cleaner technologies are ready for large-scale adoption. This study introduces an innovative multi-objective approach to integrate sustainability into the conceptual design and decision-making phases of OCCS. A systematic technology screening identified possible OCCS solutions, which were then assessed for onboard feasibility. Specific indicators were defined to evaluate OCCS performance based on technological, economic, environmental, and social criteria, and aggregated sustainability perspectives. Using a fossil fuel-powered cruise ship as a case study, results were benchmarked against zero-carbon alternatives. Among the alternatives considered, chemical absorption by amine scrubbing (AS) and advanced cryogenic carbon capture (A3C) appeared as the only feasible solutions considering onboard energy requirements. The emerging cryogenic A3C concept resulted in being outperformed by benchmark AS, primarily due to an environmental impact 1.5 times higher. All alternative technologies, whether OCCS- or cleaner fuel-based, were found to be more sustainable than the baseline fossil fuel-based engine, lowering the environmental impact by at least 61%. Hydrogen as a marine fuel leads to the most promising scenario for future cleaner shipping operations, reducing the sustainability footprint by up to 76%. The robustness of the proposed method was confirmed by a probabilistic Monte Carlo sensitivity analysis. Overall, the results obtained can guide toward more informed solutions and policies promoting the sustainability of ship propulsion systems.

Design of on-board energy storage system using SiC MOSFET

Design of on-board energy storage system using SiC MOSFET

Scaling up a hollow fibre adsorption unit for on-board CCS applications using a real gasoline engine exhaust

Decarbonising road transport using on-board carbon capture and storage (CCS) is challenged by inherent space and energy limitations. Thus, to be technically and economically viable, robust and compact carbon capture units need to be developed. Hence, in this work, a scaled up hollow fibre adsorption unit was tested downstream of a real 90:10 gasoline-ethanol engine exhaust gas to evaluate its CO2 capture performance after 100 adsorption–desorption cycles. The scaled up hollow fibre adsorption unit consisted of 37 four-channel hollow fibre adsorption units coated with a thin carbon xerogel layer, referred to as the CX-coated hollow fibre module (HFM). It should be noted that this is the first study to report the results of a HFM tested under real conditions over 100 adsorption–desorption cycles and is one of the few studies that reports the desorption step. Furthermore, despite the presence of CO, THC, NOx, and H2O in the exhaust gas, the CX-coated HFM exhibited high CO2 capture stability and mechanical integrity. This was evidenced through the CX-coated HFM obtaining and maintaining an average total capacity of 1.2 mmol/g over 100 adsorption–desorption cycles, and showing no visible signs of deterioration or a loss of mechanical integrity.