Publications

In a context of the decarbonization of the power sector the gas turbine manufacturers are expected tohandle and burn hydrogen or hydrogen/natural gas mixtures. This evolution is conceptually simple in order to displace CO2 emissions by H2O in the combustion exhaust but raises potential engineering andsafety related questions. Concerning the safety aspect the flammability domain is wider and the laminar flame speed is higher for hydrogen than for natural gas. As a result handling fuels with increased hydrogen concentration should a priori lead to an increased the risk of flammable cloud formation with air and also increase the potential explosion violence.<br/>A central topic for the gas turbine manufacturer is the quantification of the hydrogen fuel content from which the explosion risk increases significantly when compared with the use of natural gas. This work will be focused on a risk study of the fuel supply piping of a gas turbine in a scenario where mixing between fuel and air would occur. The pipes are a few dozens of meters long and show singularities: elbows connections with other lines … They are operated at high temperature and atmospheric or high pressure.<br/>The paper will first highlight through CFD modelling the impact of increasing hydrogen content in the fuel on the explosion risk based on a geometry representative of a realistic system. Second the quantification of the explosion effects will be addressed. Some elements of the bibliography relative to flame propagation in pipes will be recalled and put in sight of the characteristics of the industrial case. Finally a CFD model proposed recently for accounting for methane or hydrogen flames propagating in long open steel tubes was used to assess a hydrogen fuel content from which the flame can strongly accelerate and generate significative pressure effects for a flammable mixture initially at atmospheric conditions.

This paper presents model predictions obtained with the CFD tool FLACS for hydrogen releases and vented deflagrations in containers and larger enclosures. The paper consists of two parts. The first part compares experimental results and model predictions for two test cases: experiments performed by Gexcon in 20-foot ISO containers (volume 33 m3 ) as part of the HySEA project and experiments conducted by SRI International and Sandia National Laboratories in a scaled warehouse geometry (volume 45.4 m3 ). The second part explores the use of the model system validated in the first part to accidental releases of hydrogen from forklift trucks inside a full-scale warehouse geometry (32 400 m3 ). The results demonstrate the importance of using realistic and reasonably accurate geometry models of the systems under consideration when performing CFD-based risk assessment studies. The discussion highlights the significant inherent uncertainty associated with quantitative risk assessments for vented hydrogen deflagrations in complex geometries. The suggestions for further work include a pragmatic approach for developing empirical correlations for pressure loads from vented hydrogen deflagrations in industrial warehouses with hydrogen-powered forklift trucks.

This report evaluates the main options to provide required hydrogen storage capacity including the relevant system-level considerations and provides recommendations for further actions including low-regrets actions that are needed in a range of scenarios.

Hydrogen is crucial in achieving global energy transition and carbon neutrality goals. Existing market estimates typically presume linear or exponential growth but fail to consider how market demand responds to the declining cost of underlying technologies. To address this this study utilizes a learning curve model to project the cost of electrolyzers and its subsequent impact on hydrogen market aligning with a premise that the market demand is proportional to the cost of hydrogen. In a case study of China’s hydrogen market projecting from 2020 to 2060 we observed substantial differences in market evolution compared to exponential growth scenarios. Contrary to exponential growth scenarios China’s hydrogen market experiences faster growth during the 2020–2040 period rather than later. Such differences underscore the necessity for proactive strategic planning in emerging technology markets particularly for those experiencing rapid cost decline such as hydrogen. The framework can also be extended to other markets by using local data providing valuable insights to investors policymakers and developers engaged in the hydrogen market.

The cross-regional renewable hydrogen supply is significant for China to resolve the uneven distribution of renewable energy and decarbonize the transportation sector. Yet the economic comparison of various hydrogen supply routes remains obscure. This paper conducts a techno-economic analysis on six hydrogen supply routes for hydrogen refueling stations including gas-hydrogen tube-trailer gas-hydrogen pipeline liquid-hydrogen truck natural gas pipeline MeOH truck and NH3 truck. Furthermore the impacts of three critical factors are examined including electrolyzer selection transportation distance and electricity price. The results indicate that with a transport distance of 2000 km the natural gas pipeline route offers the lowest cost while the gas-hydrogen tube-trailer route is not economically feasible. The gas-hydrogen pipeline route shows outstanding cost competitiveness between 200 and 2000 km while it is greatly influenced by the utilization rate. The liquid-hydrogen truck route demonstrates great potential with the electricity price decreasing. This study may provide guidance for the development of the cross-regional renewable hydrogen supply for hydrogen refueling stations in China.

With an increase in the use of eco-friendly vehicles such as hybrid electric and hydrogen vehicles in response to the global climate crisis accidents related to these vehicles have also increased. Numerical analysis was performed to optimize the safety of first responders responding to hydrogen vehicle accidents wherein hydrogen jet flames occur. The influence range of the jet flame generated through a 1.8-mm-diameter nozzle was analyzed based on five discharge angles (90 75 60 45 and 30◦ ) between the road surface and the downward vertical. As the discharge angle decreases toward the road surface the risk area that could cause damage moves from the center of the vehicle to the rear; at a discharge angle of 90◦ the range above 9.5 kW/m2 was 1.59 m and 4.09 m to the front and rear of the vehicle respectively. However at a discharge angle of 30◦ it was not generated at the front but was 10.39 m to the rear. In response to a hydrogen vehicle accident first responders should perform rescue activities approaching from a diagonal direction to the vehicle front to minimize injury risk. This study can be used in future hydrogen vehicle design to develop the response strategy of the first responders.

The energy transition from hydrocarbon-based energy sources to renewable and carbon-free energy sources such as wind solar and hydrogen is facing increasing demands. The decarbonization of global transportation could come true via applying carbon-free fuel such as ammonia especially for internal combustion engines (ICEs). Although ammonia has advantages of high hydrogen content high octane number and safety in storage it is uninflammable with low laminar burning velocity thus limiting its direct usage in ICEs. The purpose of this review paper is to provide previous studies and current research on the current technical advances emerging in assisted combustion of ammonia. The limitation of ammonia utilization in ICEs such as large minimum ignition energy lower flame speed and more NOx emission with unburned NH3 could be solved by oxygen-enriched combustion ammonia–hydrogen mixed combustion and plasma-assisted combustion (PAC). In dual-fuel or oxygen-enriched NH3 combustion accelerated flame propagation speeds are driven by abundant radicals such as H and OH; however NOx emission should be paid special attention. Furthermore dissociating NH3 in situ hydrogen by non-noble metal catalysts or plasma has the potential to replace dual-fuel systems. PAC is able to change classical ignition and extinction S-curves to monotonic stretching which makes low-temperature ignition possible while leading moderate NOx emissions. In this review the underlying fundamental mechanism under these technologies are introduced in detail providing new insight into overcoming the bottleneck of applying ammonia in ICEs. Finally the feasibility of ammonia processing as an ICE power source for transport and usage highlights it as an appealing choice for the link between carbon-free energy and power demand.

The shift from centralized to distributed generation and the need to address energy shortage and achieve the sustainability goals are among the important factors that drive increasing interests of governments planners and other relevant stakeholders in microgrid systems. Apart from the distributed renewable energy resources fuel cells (FCs) are a clean pollution-free highly efficient flexible and promising energy resource for microgrid applications that need more attention in research and development terms. Furthermore they can offer continuous operation and do not require recharging. This paper examines the exciting potential of FCs and their utilization in microgrid systems. It presents a comprehensive review of FCs with emphasis on the developmental status of the different technologies comparison of operational characteristics and the prevailing techno-economic barriers to their progress and the future outlook. Furthermore particular attention is paid to the applications of the FC technologies in microgrid systems such as grid-integrated grid-parallel stand-alone backup or emergency power and direct current systems including the FC control mechanisms and hybrid designs and the technical challenges faced when employing FCs in microgrids based on recent developments. Microgrids can help to strengthen the existing power grid and are also suitable for mitigating the problem of energy poverty in remote locations. The paper is expected to provide useful insights into advancing research and developments in clean energy generation through microgrid systems based on FCs.

This paper presents an economic impact analysis and carbon footprint study of a hydrogenbased microgrid. The economic impact is evaluated with respect to investment costs operation and maintenance (O&M) costs as well as savings taking into account two different energy management strategies (EMSs): a hydrogen-based priority strategy and a battery-based priority strategy. The research was carried out in a real microgrid located at the University of Huelva in southwestern Spain. The results (which can be extrapolated to microgrids with a similar architecture) show that although both strategies have the same initial investment costs (EUR 52339.78) at the end of the microgrid lifespan the hydrogen-based strategy requires higher replacement costs (EUR 74177.4 vs. 17537.88) and operation and maintenance costs (EUR 35254.03 vs. 34877.08) however it provides better annual savings (EUR 36753.05 vs. 36282.58) and a lower carbon footprint (98.15% vs. 95.73% CO2 savings) than the battery-based strategy. Furthermore in a scenario where CO2 emission prices are increasing the hydrogen-based strategy will bring even higher annual cost savings in the coming years.