Hydrogen application technologies and environmentally friendly smart energy system

Climate change and fossil fuel depletion are the main reasons for many countries around the world to develop and implement energy transition strategies. Being a very clean burning fuel (generating steam only), hydrogen will play an important role in the transition from fossil energy to CO2-free energy. The paper introduces recent advances of hydrogen technology applied in transportation, industry, and power generation in the world; challenges regarding hydrogen safety and technology; barriers in social perception; and some recommendations for the development of hydrogen technology and environmentally friendly smart energy systems in Vietnam.

Numerical Simulation of Hydrogen Leakage and Diffusion Process of Fuel Cell Vehicle

Regarding the problem of hydrogen diffusion of the fuel cell vehicle (HFCV) when its hydrogen supply system leaks, this research uses the FLUENT software to simulate numerical values in the process of hydrogen leakage diffusion in both open space and closed space. This paper analyzed the distribution range and concentration distribution characteristics of hydrogen in these two different spaces. Besides, this paper also took a survey about the effects of leakage rate, wind speed, wind direction in open space and the role the air vents play on hydrogen safety in closed space, which provides a reference for the hydrogen safety of HFCV. In conclusion, the experiment result showed that: In open space, hydrogen leakage rate has a great influence on its diffusion. When the leakage rate doubles, the hydrogen leakage range will expand about 1.5 times simultaneously. The hydrogen diffusion range is the smallest when the wind blows at 90 degrees, which is more conducive to hydrogen diffusion. However, when the wind direction is against the direction of the leakage of hydrogen, the range of hydrogen distribution is maximal. Under this condition, the risk of hydrogen leakage is highest. In an enclosed space, when the vent is set closest to the leakage position, the volume fraction of hydrogen at each time is smaller than that at other positions, so it is more beneficial to safety.

Hydrogen Safety Prediction and Analysis of Hydrogen Refueling Station Leakage Accidents and Process Using Multi-Relevance Machine Learning

Hydrogen energy vehicles are being increasingly widely used. To ensure the safety of hydrogenation stations, research into the detection of hydrogen leaks is required. Offline analysis using data machine learning is achieved using Spark SQL and Spark MLlib technology. In this study, to determine the safety status of a hydrogen refueling station, we used multiple algorithm models to perform calculation and analysis: a multi-source data association prediction algorithm, a random gradient descent algorithm, a deep neural network optimization algorithm, and other algorithm models. We successfully analyzed the data, including the potential relationships, internal relationships, and operation laws between the data, to detect the safety statuses of hydrogen refueling stations.

Numerical Simulation of Hydrogen Leakage from Fuel Cell Vehicle in an Outdoor Parking Garage

It is significant to assess the hydrogen safety of fuel cell vehicles (FCVs) in parking garages with a rapidly increased number of FCVs. In the present work, a Flame Acceleration Simulator (FLACS), a computational fluid dynamics (CFD) module using finite element calculation, was utilized to predict the dispersion process of flammable hydrogen clouds, which was performed by hydrogen leakage from a fuel cell vehicle in an outdoor parking garage. The effect of leakage diameter (2 mm, 3 mm, and 4 mm) and parking configurations (vertical and parallel parking) on the formation of flammable clouds with a range of 4–75% by volume was considered. The emission was assumed to be directed downwards from a Thermally Activated Pressure Relief Device (TPRD) of a 70 MPa storage tank. The results show that the 0.7 m parking space stipulated by the current regulations is less than the safety space of fuel cell vehicles. Compared with a vertical parking configuration, it is safer to park FCVs in parallel. It was also shown that release through a large TPRD orifice should be avoided, as the proportion of the larger hydrogen concentration in the whole flammable domain is prone to more accidental severe consequences, such as overpressure.

Liquid Hydrogen Spills on Water—Risk and Consequences of Rapid Phase Transition

Liquid hydrogen (LH2) spills share many of the characteristics of liquefied natural gas (LNG) spills. LNG spills on water sometimes result in localized vapor explosions known as rapid phase transitions (RPTs), and are a concern in the LNG industry. LH2 RPT is not well understood, and its relevance to hydrogen safety is to be determined. Based on established theory from LNG research, we present a theoretical assessment of an accidental spill of a cryogen on water, including models for pool spreading, RPT triggering, and consequence quantification. The triggering model is built upon film-boiling theory, and predicts that the mechanism for RPT is a collapse of the gas film separating the two liquids (cryogen and water). The consequence model is based on thermodynamical analysis of the physical processes following a film-boiling collapse, and is able to predict peak pressure and energy yield. The models are applied both to LNG and LH2, and the results reveal that (i) an LNG pool will be larger than an LH2 pool given similar sized constant rate spills, (ii) triggering of an LH2 RPT event as a consequence of a spill on water is very unlikely or even impossible, and (iii) the consequences of a hypothetical LH2 RPT are small compared to LNG RPT. Hence, we conclude that LH2 RPT seems to be an issue of only minor concern.