Korea, Republic of

The rise in hydrogen fuel cell electric vehicles (FCEVs) is expected to pose a variety of hazards on the road. Vehicles using hydrogen could cause significant damage owing to hydrogen vapor cloud explosions jet fires caused by leakage or hydrogen tank explosions. This risk is expected to further increase in semi-enclosed spaces such as underground parking lots and road tunnels. Therefore it is necessary to study the fire safety of hydrogen vehicles in semi-enclosed spaces. In this study an experiment on hydrogen tank explosion was performed. In addition the CFD numerical model was verified using the experimental results and the damaging effect due to pressure propagation during hydrogen tank explosions in underground parking lots and road tunnels was analyzed using numerical analysis. From the experiment results the hydrogen tank exploded at about 80 Mpa a maximum incident pressure is generated 267 kPa at a distance of 1.9 m. As a result of numerical analysis based on the experimental results the limit distance that can cause serious injury due to the explosion of a hydrogen tank in a road tunnel or underground parking lot was analyzed up to about 20 m from the point of explosion.

The temperature of the hydrogen cylinder needs to be carefully controlled during fuelling process. The maximum temperature should be less than 85℃ according to the ISO draft code. If the fuelling period is reduced the maximum temperature should increase. In this study temperature change of a Type IV cylinder was measured during the hydrogen fuelling process up to 35 MPa. Fuelling period was 3 to 5 minutes. Twelve thermocouples were installed to measure inside gas temperature and seven were attached on the outside of the cylinder. An infrared camera was also used for measuring temperature distribution of outside of cylinder. The maximum gas temperature was higher than 85℃ inside of the cylinder. Significant temperature difference between the upper and lower part of the vessel was observed. Temperature near the plug and the valve was quickly increased and maintained higher than that of the other region. Temperature increases for the partial refuelling process were also discussed.

We performed a hydrogen combustion analysis in the Advanced Power Reactor 1400 MWe (APR1400) containment during a severe accident initiated by a small break loss of coolant accident (SBLOCA) which occurred at a lower part of the cold leg using a multi-dimensional hydrogen analysis system (MHAS) to confirm the integrity of the APR1400 containment. The MHAS was developed by combining MAAP GASFLOW and COM3D to simulate hydrogen release distribution and combustion in the containment of a nuclear power plant during the severe accidents in the containment of a nuclear power reactor. The calculated peak pressure due to the flame acceleration by the COM3D using the GASFLOW results as an initial condition of the hydrogen distribution was approximately 555 kPa which is lower than the fracture pressure 1223 kPa of the APR1400 containment. To induce a higher peak pressure resulted from a strong flame acceleration in the containment we intentionally assumed several things in developing an accident scenario of the SBLOCA. Therefore we may judge that the integrity of the APR1400 containment can be maintained even though the hydrogen combustion occurs during the severe accident initiated by the SBLOCA.

Hydrogen can be produced in undesired ways such as a high temperature metal oxidation during an accident. In this case the hydrogen must be carefully managed. A hydrogen mitigation system (HMS) should be installed to protect a containment of a nuclear power plant (NPP) from hazards of hydrogen produced by an oxidation of the fuel cladding during a severe accident in an NPP. Among hydrogen removal devices passive auto-catalytic recombiners (PARs) are currently applied to many NPPs because of passive characteristics such as not requiring a power supply nor an operators’ manipulations. However they offer several disadvantages resulting in issues related to hydrogen control by PARs. One of the issues is a hydrogen stratification in which hydrogen is not well-mixed in a compartment due to the high temperature exhaust gas of PARs and accumulation in the lower part. Therefore experimental simulation on hydrogen stratification phenomenon by PARs is required. When the hydrogen stratification by PARs is observed in the experiment the verification and improvement of a PAR analysis model using the experimental results can be performed and the hydrogen removal characteristics by PARs installed in an NPP can be evaluated using the improved PAR model. View Full-Text

NaBH4-based hydrogen generator for fuel cell Unmanned Aerial Vehicle (UAVs) with movable fuel cartridge was developed in the present study. The main fuel of hydrogen generator is Sodium borohydride (NaBH4) that is a kind of chemical hydride and has a high hydrogen storage density. In the previous studies hydrogen generators were developed in which hydrogen was directly generated from solid state NaBH4. However it was a prototype so inconvenient to replace the fuel after used up and lacked user convenience. Therefore the performance evaluation and the development procedure of NaBH4-based hydrogen generator that was designed taking user convenience in consideration for commercialization were described in this paper.

The amount of hydrogen gas generated from metal oxide materials based on a thermochemical water-splitting method gradually reduces as the surface of the metal oxide oxidizes during the hydrogen generation process. To regenerate hydrogen the oxygen reduction process of a metal oxide at high temperatures (1000–2500 °C) is generally required. In this study to overcome the problem of an energy efficiency imbalance in which the required energy of the oxygen reduction process for hydrogen regeneration is higher than the generated hydrogen energy we investigated the possibility of the oxygen reduction of a metal oxide with a low energy using microwave irradiation. For this purpose a macroporous nickel-oxide structure was used as a metal oxide catalyst to generate hydrogen gas and the oxidized surface of the macroporous nickel-oxide structure could be reduced by microwave irradiation. Through this oxidation reduction process ∼750 μmol g⁻¹ of hydrogen gas could be continuously regenerated. In this way it is expected that oxygen-enriched metal oxide materials can be efficiently reduced by microwave irradiation with a low power consumption of <∼4% compared to conventional high-temperature heat treatment and thus can be used for efficient hydrogen generation and regeneration processes in the future.

In this study ethylene glycol (EG) and terephthalic acid (TPA) were used to generate hydrogen using copper electrodes in an alkaline aqueous solution and the corresponding reaction mechanism was experimentally investigated. Both EG and TPA produced hydrogen; however TPA consumed OH− inhibiting the production of intermediary compounds of EG and causing EG to actively react with H2O ultimately leading to enhanced hydrogen production. In addition the initiation potential of water decomposition of the EG and TPA alkaline aqueous solution was 1.0 V; when 1.8 V (vs. RHE) was applied the hydrogen production reached 440 mmol L⁻¹ which was substantially greater than the hydrogen production rate of 150 mmol L⁻¹ during water decomposition.

It is important to examine in detail how the distribution of academic research topics related to renewable energy is structured and which topics are likely to receive new attention in the future in order for scientists to contribute to the development of renewable energy. This study uses an advanced probabilistic topic modeling to statistically examine the temporal changes of renewable energy topics by using academic abstracts from 2010–2019 and explores the properties of the topics from the perspective of future signs such as weak signals. As a result in strong signals methods for optimally integrating renewable energy into the power grid are paid great attention. In weak signals interest in large-capacity energy storage systems such as hydrogen supercapacitors and compressed air energy storage showed a high rate of increase. In not-strong-but-well-known signals comprehensive topics have been included such as renewable energy potential barriers and policies. The approach of this study is applicable not only to renewable energy but also to other subjects.

The hydrogen economy refers to an economic and industrial structure that uses hydrogen as its main energy source replacing traditional fossil-fuel-based energy systems. In particular the widespread adoption of hydrogen fuel cell vehicles (HFCVs) is one of the key factors enabling a hydrogen economy and aggressive investment in hydrogen refuelling infrastructure is essential to make large-scale adoption of HFCVs possible. In this study we address the problem of effectively designing a hydrogen supply network for refuelling HFCVs in urban areas relatively far from a large hydrogen production site such as a petrochemical complex. In these urban areas where mass supply of hydrogen is not possible hydrogen can be supplied by reforming city gas. In this case building distributed hydrogen production bases that extract large amounts of hydrogen from liquefied petroleum gas (LPG) or compressed natural gas (CNG) and then supply hydrogen to nearby hydrogen stations may be a cost-effective option for establishing a hydrogen refuelling infrastructure in the early stage of the hydrogen economy. Therefore an optimization model is proposed for effectively deciding when and where to build hydrogen production bases and hydrogen refuelling stations in an urban area. Then a case study of the southeastern area of Seoul known as a commercial and residential center is discussed. A variety of scenarios for the design parameters of the hydrogen supply network are analyzed based on the target of the adoption of HFCVs in Seoul by 2030. The proposed optimization model can be effectively used for determining the time and sites for building hydrogen production bases and hydrogen refuelling stations.

316L stainless steel is a promising material candidate for a hydrogen containment system. However when in contact with hydrogen the material could be degraded by hydrogen embrittlement (HE). Moreover the mechanism and the effect of HE on 316L stainless steel have not been clearly studied. This study investigated the effect of hydrogen exposure on the impact toughness of 316L stainless steel to understand the relation between hydrogen charging time and fracture toughness at ambient and cryogenic temperatures. In this study 316L stainless steel specimens were exposed to hydrogen in different durations. Charpy V-notch (CVN) impact tests were conducted at ambient and low temperatures to study the effect of HE on the impact properties and fracture toughness of 316L stainless steel under the tested temperatures. Hydrogen analysis and scanning electron microscopy (SEM) were conducted to find the effect of charging time on the hydrogen concentration and surface morphology respectively. The result indicated that exposure to hydrogen decreased the absorbed energy and ductility of 316L stainless steel at all tested temperatures but not much difference was found among the pre-charging times. Another academic insight is that low temperatures diminished the absorbed energy by lowering the ductility of 316L stainless steel