Applications & Pathways

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.

This study presents a Two-Layer Deep Deterministic Policy Gradient (TL-DDPG) energy management strategy for Hydrogen fuel cell hybrid train that aims to solve the problem that traditional reinforcement learning strategies require high initial values and are difficult to optimize global variables. Augmenting the optimization capabilities of the inner layer a frequency decoupling algorithm integrates into the outer layer furnishing a fitting initial value for strategy optimization. This addition aims to bolster the stability of fuel cell output thereby enhancing the overall efficiency of the hybrid power system. In comparison with the traditional reinforcement learning algorithm the proposed approach demonstrates notable improvements: a reduction in hydrogen consumption per 100 km by 16.3 kg a 9.7% increase in the output power stability of the fuel cell and a 1.8% enhancement in its efficiency.

Hydrogen as an energy carrier could help decarbonize industrial building and transportation sectors and be used in fuel cells to generate electricity power or heat. One of the numerous ways to solve the climate crisis is to make the vehicles on our roads as clean as possible. Fuel cell electric vehicles (FCEVs) have demonstrated a high potential in storing and converting chemical energy into electricity with zero carbon dioxide emissions. This review paper comprehensively assesses hydrogen’s potential as an innovative alternative for reducing greenhouse gas (GHG) emissions in transportation particularly for on-board applications. To evaluate the industry’s current status and future challenges the work analyses the technology behind FCEVs and hydrogen storage approaches for on-board applications followed by a market review. It has been found that to achieve long-range autonomy (over 500 km) FCEVs must be capable of storing 5–10 kg of hydrogen in compressed vessels at 700 bar with Type IV vessels being the primary option in use. Carbon fiber is the most expensive component in vessel manufacturing contributing to over 50% of the total cost. However the cost of FCEV storage systems has considerably decreased with current estimates around 15.7 $/kWh and is predicted to drop to 8 $/kWh by 2030. In 2021 Toyota Hyundai Mercedes-Benz and Honda were the major car brands offering FCEV technology globally. Although physical and chemical storage technologies are expected to be valuable to the hydrogen economy compressed hydrogen storage remains the most advanced technology for on-board applications.

In order to promote low-carbon fuels such as hydrogen to decarbonize the maritime sector it is crucial to promote clean fuels and zero-emission propulsion systems in demonstrative projects and to showcase innovative technologies such as fuel cells in vessels operating in local public transport that could increase general audience acceptability thanks to their showcase potential. In this study a short sea journey ferry used in the port of Genova as a public transport vehicle is analyzed to evaluate a ”zero emission propulsion” retrofitting process. In the paper different types of solutions (batteries proton exchange membrane fuel cell (PEMFC) solid oxide fuel cell (SOFC)) and fuels (hydrogen ammonia natural gas and methanol) are investigated to identify the most feasible technology to be implemented onboard according to different aspects: ferry daily journey and scheduling available volumes and spaces propulsion power needs energy storage/fuel tank capacity needed economics etc. The paper presents a multi-aspect analysis that resulted in the identification of the hydrogen-powered PEMFC as the best clean power system to guarantee for this specific case study a suitable retrofitting of the vessel that could guarantee a zero-emission journey

The number of Fuel Cell Electric Vehicles (FCEVs) in circulation has undergone a significant increase in recent years. This trend is foreseen to be stronger in the near future. In correlation with the FCEVs market increase the hydrogen delivery infrastructure must be developed. With this aim many countries have announced ambitious projects. For example Spain has the objective of increasing the number of Hydrogen Refuelling Stations (HRS) with public access from three units in operation currently to about 150 by 2030. HRSs are complex systems with high variability in terms of layout design size of components operational strategy hydrogen generation method or hydrogen generation location. This paper is focused on on-site HRS with electrolysis-based hydrogen production which provides interesting advantages when renewable energy is utilized compared to off-site hydrogen production despite their complexity. To optimize HRS design and operation a simulation model must be implemented. This paper describes a generic on-site HRS with electrolysis-based hydrogen production a cascaded multi-tank storage system with multiple compressors renewable energy sources and multiple types of dispensing formats. A modelling approach of the layout is presented and tested with real-based parameters of an HRS currently under development which is capable of producing 11.34 kg/h of green H2 with irradiation at 1000 W/m2. For the operation an operational strategy is proposed. The modelled system is tested through several simulations. A sensitivity analysis of the effects of hydrogen demand and day-ahead hydrogen production objective on emissions demand satisfaction and variable costs is performed. Simulation results show how the operational strategy has achieved service up to 310 FCEVs refuelling events of heavy duty and light duty FCEVs bringing the total H2 sold up to almost 7200 H2kg in one month of winter. Additionally considering variable costs of the energy from the utility grid the model shows a profit in the range of 21–50 k€ for a daily demand of 60 H2kg/day and 100 H2kg/day respectively. In terms of emissions a year simulation with 60 H2kg/day of demand shows specific emissions in the production of H2 in Spain of 6.26 kgCO2eq/H2kg which represents a greenhouse gas emission intensity of 52.26 kgCO2eq/H2MJ.

The shipping sector is facing increasing pressure to implement clean fuels and drivetrains. Especially hydrogen fuel cell drivetrains seem attractive. Although several studies have been conducted to assess the carbon footprint of hydrogen and its application in ships their results remain hard to interpret and compare. Namely it is necessary to include a variety of drivetrain solutions and different studies are based on various assumptions and are expressed in other units. This paper addresses this problem by offering a three-step meta-review of life cycle assessment studies. First a literature review was conducted. Second results from the literature were harmonized to make the different analyses comparable serving cross-examination. The entire life cycle of both the fuels and drivetrains were included. The results showed that the dominant impact was fuel use and related fuel production. And finally life-cycle hot spots have been identified by looking at the effect of specific configurations in more detail. Hydrogen production by electrolysis powered by wind has the most negligible impact. For this ultra-low carbon pathway the modes of hydrogen transport and the use of specific materials and components become relevant.

In the context of the increasingly strict pollutant emission regulations and carbon emission reduction targets proposed by the International Maritime Organization the shipping industry is seeking new types of marine power plants with the advantages of high efficiency and low emissions. Among the possible alternatives the fuel cell is considered to be the most practical technology as it provides an efficient means to generate electricity with low pollutant emissions and carbon emissions. Very few comprehensive reviews focus on the maritime applications of the fuel cell. Thus news reports and literature on the maritime applications of the fuel cell in the past sixty years were collected and the industrial development status and prospects of the marine fuel cell were summarized as follows. Some countries in Europe North America and Asia have invested heavily in researching and developing the marine fuel cell and a series of research projects have achieved concrete results such as the industrialized marine fuel cell system or practical demonstration applications. At present the worldwide research of the marine fuel cell focuses more on the proton exchange membrane fuel cell (PEMFC). However the power demand of the marine fuel cell in the future will show steady growth and thus the solid oxide fuel cell (SOFC) with the advantages of higher power and fuel diversity will be the mainstream in the next research stage. Although some challenges exist the SOFC can certainly lead the upgrading and updating of the marine power system with the cooperative efforts of the whole world.

This paper introduces a Techno-Economic Assessment (TEA) on present and future scenarios of different energy storage technologies comprising hydrogen and batteries: Battery Energy Storage System (BESS) Hydrogen Energy Storage System (H2ESS) and Hybrid Energy Storage System (HESS). These three configurations were assessed for different time horizons: 2019 2022 and 2030 under both on-grid and off-grid conditions. For 2030 a sensitivity analysis under different energy scenarios was performed covering other trends in on-grid electric consumption and prices CO2 taxation and the evolution of hydrogen technology prices from 2019 until 2030. The selected case study is the Research Park Zellik (RPZ) a CO2- neutral sustainable Local Energy Community (LEC) in Zellik Belgium. The software HOMER (Hybrid Optimisation Model for Electric Renewable) has been selected to design model and optimise the defined case study. The results showed that BESS was the most competitive when the electric grid was available among the three possible storage options. Additionally HESS was overall more competitive than H2ESS-only regardless of the grid connection mode. Finally as per HESS hydrogen was proved to play a complementary role when combined with batteries enhancing the flexibility of the microgrid and enabling deeper decarbonisation by reducing the electricity bought from the grid increasing renewable energy production and balancing toward an island operating mode.

A proton exchange membrane fuel cell (PEMFC) is known as one of the most promising energy sources for electric vehicles. A hydrogen system is required to provide hydrogen to the stack in time to meet the flow and pressure requirements according to the power requirements. In this study a 1-D model of a hydrogen system including the fuel cell stack was established. Two modes one with and one without a proportion integration differentiation (PID) control strategy were applied to analyze the pressure characteristics and performance of the PEMFC. The results showed that the established model could be well verified with experimental data. The anode pressure fluctuation with a PID control strategy was more stable which reduced the damage to the fuel cell stack caused by sudden changes of anode pressure. In addition the performance of the stack with the PID control mode was slightly improved. There was an inflection point for hydrogen utilization; the hydrogen utilization rate was higher under the mode without PID control when the current density was greater than 0.4 A/cm2 . What is more a hierarchical control strategy was proposed which made the pressure difference between the anode and cathode meet the stack working requirements and more importantly maintained the high hydrogen utilization of the hydrogen system.

In vertically integrated energy systems integration frequently entails operational gains that must be traded off against the requisite cost of capacity investments. In the context of the model analyzed in this study the operational gains are subject to inherent volatility in both the price and the output of the intermediate product transferred within the vertically integrated structure. Our model framework provides necessary and sufficient conditions for the value (NPV) of an integrated system to exceed the sum of two optimized subsystems on their own. We then calibrate the model in Germany and Texas for systems that combine wind energy with Power-to-Gas (PtG) facilities that produce hydrogen. Depending on the prices for hydrogen in different market segments we find that a synergistic investment value emerges in some settings. In the context of Texas for instance neither electricity generation from wind power nor hydrogen production from PtG is profitable on its own in the current market environment. Yet provided both subsystems are sized optimally in relative terms the attendant operational gains from vertical integration more than compensate for the stand-alone losses of the two subsystems.