A Numerical Simulation on the Leakage Event of a High-Pressure Hydrogen Dispenser

For the sake of the increasing demand of hydrogen fuel cell vehicles, there are more concerns on the safety of hydrogen refueling stations. As one of the key pieces of equipment, the hydrogen dispenser has drawn attention on this aspect since it involves massive manual operations and may be bothered by a high probability of failure. In this paper, a numerical study is conducted to simulate the possible leakage events of the hydrogen dispenser based on a prototype in China whose working pressure is 70 MPa. The leakage accident is analyzed with respect to leakage sizes, leak directions, and the time to stop the leakage. It is found that, due to the large mass flow rate under such high pressure, the leak direction and the layout of the components inside the dispenser become insignificant, and the ignitable clouds will form inside the dispenser in less than 1 s if there is a leakage of 1% size of the main tube. The ignitable clouds will form near the vent holes outside the dispenser, which may dissipate quickly if the leakage is stopped. On the other hand, the gas inside the dispenser will remain ignitable for a long time, which asks for a design with no possible ignition source inside. The results can be useful in optimizing the design of the dispenser, regarding the reaction time and sensitivity requirements of the leakage detector, the size and amount of vent holes, etc.

A Decarbonization Roadmap for Singapore and Its Energy Policy Implications

As a signatory to the Paris Agreement, Singapore is committed to achieving net-zero carbon emissions in the second half of the century. In this paper, we propose a decarbonization roadmap for Singapore based on an analysis of Singapore’s energy landscape and a technology mapping exercise. This roadmap consists of four major components. The first component, which also underpins the other three components, is using centralized post-combustion carbon capture technology to capture and compress CO2 emitted from multiple industrial sources in Jurong Island. The captured CO2 is then transported by ship or an existing natural gas pipeline to a neighboring country, where it will be stored permanently in a subsurface reservoir. Important to the success of this first-of-a-kind cross-border carbon capture and storage (CCS) project is the establishment of a regional CCS corridor, which makes use of economies of scale to reduce the cost of CO2 capture, transport, and injection. The second component of the roadmap is the production of hydrogen in a methane steam reforming plant which is integrated with the carbon capture plant. The third component is the modernizing of the refining sector by introducing biorefineries, increasing output to petrochemical plants, and employing post-combustion carbon capture. The fourth component is refueling the transport sector by introducing electric and hydrogen fuel cell vehicles, using biofuels for aviation and hydrogen for marine vessels. The implications of this roadmap on Singapore’s energy policies are also discussed.

Life Cycle Assessment of Electric Vehicles and Hydrogen Fuel Cell Vehicles Using the GREET Model—A Comparative Study

Facing global warming and recent bans on the use of diesel in vehicles, there is a growing need to develop vehicles powered by renewable energy sources to mitigate greenhouse gas and pollutant emissions. Among the various forms of non-fossil energy for vehicles, hydrogen fuel is emerging as a promising way to combat global warming. To date, most studies on vehicle carbon emissions have focused on diesel and electric vehicles (EVs). Emission assessment methodologies are usually developed for fast-moving consumer goods (FMCG) which are non-durable household goods such as packaged foods, beverages, and toiletries instead of vehicle products. There is an increase in the number of articles addressing the product carbon footprint (PCF) of hydrogen fuel cell vehicles in the recent years, while relatively little research focuses on both vehicle PCF and fuel cycle. Zero-emission vehicles initiative has also brought the importance of investigating the emission throughout the fuel cycle of hydrogen fuel cell and its environmental impact. To address these gaps, this study uses the life-cycle assessment (LCA) process of GREET (greenhouse gases, regulated emissions, and energy use in transportation) to compare the PCF of an EV (Tesla Model 3) and a hydrogen fuel cell car (Toyota MIRAI). According to the GREET results, the fuel cycle contributes significantly to the PCF of both vehicles. The findings also reveal the need for greater transparency in the disclosure of relevant information on the PCF methodology adopted by vehicle manufacturers to enable comparison of their vehicles’ emissions. Future work will include examining the best practices of PCF reporting for vehicles powered by renewable energy sources as well as examining the carbon footprints of hydrogen production technologies based on different methodologies.

Location and Volume Determination of Hydrogen Refueling Stations Based on Oligopoly Equilibrium

The energy transformation in China is picking up speed, thanks to the mass development and utilization of various clean energies. As an emerging clean energy, hydrogen energy has been highly recognized, and gradually introduced to industry and transport. As a result, hydrogen fuel cell vehicles (HFCVs) attract a growing attention from the government and the public. However, the is a severe lack of hydrogen refueling stations (HRSs). Therefore, this paper explores into the determination of HRS location and volume. The HRS investment market was treated as an oligopoly market, due to the huge investment and few investors of HRSs. To ensure the long-term balanced development of hydrogenation, it is assumed that all investors fully analyze the possible investment behaviors of competitors and HFCV driver preference before making any investment decision. On this basis, a multi-agent optimization model was established to determine the location and volume of HRSs. The results show that, to avoid supply-demand imbalance induced by information asymmetry, the HRSs should be constructed along with an intelligent software platform, which provides HFCV drivers with rich information on hydrogenation service. Our model helps investors determine the core issues of the HRS, including location, size, and supply scale.