Applications & Pathways

Renewable hydrogen is a promising energy carrier that facilitates greater renewable energy integration while supporting the decarbonization of the industrial and transportation sectors. This study investigates the optimal design and operation of two hydrogen-based energy systems. The first energy system comprises an electrolyser compressor and hydrogen storage system. It aims to supply hydrogen as a drop-in fuel for a future potential hydrogen fleet. The electrolyser provides excess heat and oxygen for a combined heat and power (CHP) plantand ancillary services to the grid for frequency support. In the second energy system the hydrogen stored in the hydrogen tank is used by a fuel cell or gas turbine to sell electricity to the grid following price signals. The optimisation algorithm developed in this study finds the optimal capacities for the hydrogen production and storage systems and optimizes the hourly dispatch of the electrolyser. The profitability of the first investigated hydrogen-based energy system is closely connected to the hydrogen production cost which fluctuates depending on the average electricity price. The profitability is also affected by the average compensation of the ancillary services and to a lesser extent by the value of excess heat and oxygen produced during the electrolysis. Only 2020 marked out by the lowest average electricity price among the investigated years could lead to a profitable investment for the first studied energy system. The breakeven hydrogen selling price varied between 24.13 SEK/kg in 2020 to 65.63 SEK/kg in 2022 while considering the extra revenues of the grid service compensation and heat and oxygen sale. If only hydrogen sale was considered the breakeven hydrogen selling prices varied between 31.28 SEK/kg in 2020 to 86.08 SEK/kg in 2022. For the second investigated hydrogen-based energy system if the threshold electricity price for activating the hydrogen consumption system is the 90th percentile of the electricity prices every week the profitability is never attained. The fuel cell system leads to lower electrolyser and hydrogen tank capacities to meet the targeted power supply given the higher assumed efficiency as compared to the gas turbine. Nevertheless the fuel cell system shows in all the investigated subcases lower net present values as compared to the gas turbine subcases due to the higher investment and running costs. The fuel cell system shows better performances in terms of net present values than the gas turbine only in an optimistic sub case marked out by higher conversion efficiencies and lower investment and running costs for the fuel cell. The profitability of the second investigated hydrogen-based energy system is guaranteed only at an annual average electricity price above 2.7 SEK/kWh.

Eco-design is an innovative design methodology that focuses on minimizing the environmental footprint of industries including aviation right from the conceptual and development stages. However rising industrial demand calls for a more comprehensive strategy wherein beyond environmental considerations competitiveness becomes a critical factor supported by additional pillars of sustainability such as economic viability circularity and social impact. By incorporating sustainability as a primary design driver at the initial design stages this study suggests a shift from eco-driven to sustainability-driven design approaches for aircraft components. This expanded strategy considers performance and safety goals environmental impact costs social factors and circular economy considerations. To provide the most sustainable design that balances all objectives these aspects are rigorously quantified and optimized during the design process. To efficiently prioritize different variables methods such as multi-criteria decision-making (MCDM) are employed and a sustainability index is developed in this framework to assess the overall sustainability of each design alternative. The most sustainable design configurations are then identified through an optimization process. A typical aircraft component namely a hat-stiffened panel is selected to demonstrate the proposed approach. The study highlights how effectively sustainability considerations can be integrated from the early stages of the design process by exploring diverse material combinations and geometric configurations. The findings indicate that the type of fuel used and the importance given to the sustainability pillars—which are ultimately determined by the particular requirements and goals of the user—have a significant impact on the sustainability outcome. When equal prioritization is given across the diverse dimensions of sustainability the most sustainable option appears to be the full thermoplastic component when kerosene is used. Conversely when hydrogen is considered the full aluminum component emerges as the most sustainable choice. This trend also holds when environmental impact is prioritized over the other aspects of sustainability. However when costs are prioritized the full thermoplastic component is the most sustainable option whether hydrogen or kerosene is used as the fuel in the use phase. This innovative approach enhances the overall sustainability of aircraft components emphasizing the importance and benefits of incorporating a broader range of sustainability factors at the conceptual and initial design phases.

In order to improve energy utilization efficiency and the flexibility of resource transfer in oceanic-island-group microgrids a water–electricity–hydrogen flexible scheduling strategy based on a multi-rate hydrogen-powered ship is proposed. First the characteristics of the seawater desalination unit (SDU) proton exchange membrane electrolyzer (PEMEL) and battery system (BS) in consuming surplus renewable energy on resource islands are analyzed. The variable-efficiency operation characteristics of the SDU and PEMEL are established and the effect of battery life loss is also taken into account. Second a spatiotemporal model for the multi-rate hydrogen-powered ship is proposed to incorporate speed adjustment into the system optimization framework for flexible resource transfer among islands. Finally with the goal of minimizing the total cost of the system a flexible water–electricity–hydrogen hybrid resource transfer model is constructed and a certain island group in the South China Sea is used as an example for simulation and analysis. The results show that the proposed scheduling strategy can effectively reduce energy loss promote renewable energy absorption and improve the flexibility of resource transfer.

The electric–hydrogen coupled integrated energy system (EHCS) is a critical pathway for the low-carbon transition of energy systems. However the inherent uncertainties of renewable energy sources present significant challenges to optimal energy management in the EHCS. To address these challenges this paper proposes an energy management method for the EHCS based on an improved proximal policy optimization (IPPO) algorithm. This method aims to overcome the limitations of traditional heuristic algorithms such as low solution accuracy and the inefficiencies of mathematical programming methods. First a mathematical model for the EHCS is established. Then by introducing the Markov decision process (MDP) this mathematical model is transformed into a deep reinforcement learning framework. On this basis the state space and action space of the system are defined and a reward function is designed to guide the agent to learn to the optimal strategy which takes into account the constraints of the system. Finally the efficacy and economic viability of the proposed method are validated through numerical simulation.

Hydrogen use is increasing in transportation including within the railway sector. In collaboration with a governmental institution in the Netherlands we study how to design an efficient hydrogen fueling infrastructure for a railway system. The problem involves selecting yards in a network for hydrogen fueling assigning trains to these yards locating hydrogen storage and fueling stations and connecting them via pipelines. This key planning phase must avoid oversizing costly fueling infrastructure while accounting for track availability at yards and costs due to fueling operations. We formulate this novel problem which has the structure of a nested facility location problem as a mixed-integer linear program to minimize total annualized investment and operational costs. Due to the complexity of real-sized instances we propose a matheuristic that estimates the infrastructural costs for each yard and train assignment by combining a constructive algorithm with a set covering model. It then solves a single-stage facility location problem to select yards and assign trains followed by a yard-level improvement phase. Numerical experiments on a real Dutch case show that our approach delivers high-quality solutions quickly and offer insights into the optimal infrastructure design depending on the discretization of yard areas number of trains and other parameters.

Microgrids enable the integration of renewable energy sources; however managing electricity from intermittent wind and solar power remains a significant challenge. This study investigates two storage strategies for managing surplus renewable electricity in an IEEE 84-Bus microgrid with wind turbines and photovoltaic units. The first option involves producing hydrogen via electrolyzers which is stored for later electricity generation through fuel cells. The second option involves converting surplus electricity into heat using heat pumps which is then stored in thermal energy storage systems to efficiently meet the microgrid's thermal load requirements. A scenariobased day-ahead scheduling model is proposed to optimize the microgrid's electrical and thermal load management while considering uncertainties in market prices wind speeds and solar irradiance. The resulting large-scale optimization challenge is effectively tackled using the self-adaptive charge system search algorithm. The results indicate that for the optimal utilization of excess renewable electricity heat generation via heat pumps is more cost-effective than hydrogen production primarily due to the inefficiencies in hydrogen conversion and the ability of heat pumps to produce several units of heat for each unit of electricity consumed. Moreover heat pumps prove to be more economical than natural gas combustion in boilers for meeting the thermal demands across a wide range of gas prices. These findings highlight the economic benefits of integrating heat pumps and thermal energy storage systems into renewable energy microgrids.

As one of the most promising clean energy sources hydrogen power has gradually emerged as a viable alternative to traditional energy sources. However hydrogen safety remains a significant concern due to the potential for explosions and the associated risks. This review systematically examines hydrogen explosions with a focus on high-pressure and low-temperature storage transportation and usage processes mostly based on the published papers from 2020. The fundamental principles of hydrogen explosions classifications and analysis methods including experimental testing and numerical simulations are explored. Key factors influencing hydrogen explosions are also discussed. The safety issues of hydrogen power on railway applications are focused and finally recommendations are provided for the safe application of hydrogen power in railway transportation particularly for long-distance travel and heavy-duty freight trains with an emphasis on storage safety considerations.

Green hydrogen has emerged as a promising energy vector for the decarbonisation of heavy industry. The EU and national governments have recently introduced incentives to address the high costs of green hydrogen production and accelerate the economic development of hydrogen. This study investigates the local production of green hydrogen to decarbonise the high-temperature process heat demand of a heavy industry located in Italy. The hydrogen generation is powered by PV electricity and from the electric grid. We have optimised the sizes of the energy system components including battery storage and hydrogen tanks. The Levelised Cost of Hydrogen (LCOH) was found to be 7.7 EUR/kg in the unincentivised base scenario but this amount significantly reduced to 3.3 EUR/kg when incentives on hydrogen production in abandoned industrial areas were considered. Thanks to such incentives the greenhouse gas emissions decreased by as much as 85 % with respect to the non-incentivised base case. Our results show that the effect of the incentives on the design and economics of the system is comparable with the expected reductions in equipment costs over the next decade. Importantly our findings reveal a linear relationship between Capital Costs and LCOH thereby enabling precise cost estimations to be made for the considered location without any further simulations. A side effect of the size optimisation in the presence of incentives is an increase of the plant footprint. However the limited availability of land could lead to non-optimal configurations with important impacts on emission intensity and LCOH.

This study compares hydrogen ammonia-hydrogen fuel blends and Jet-A2 fuel in gas turbine combustors using a well-stirred reactor model and validated MATLAB library H2ools to assess flame temperature pollutant generation combustion stability and thermal efficiency. The aim is to address a significant deficiency in existing research which frequently lacks standardized turbine-related comparisons among new zero-carbon fuels. Quantitative data indicate that pure hydrogen attains the maximum adiabatic flame temperature (2552 Kelvin) laminar flame speed (7.73 meters per second) and heat generation (9.02 × 1010 watts per cubic meter) while also demonstrating increased nitrogen oxide emissions (up to 6400 parts per million). Jet-A2 exhibits reduced flame temperatures (2429 Kelvin) and minimal nitrogen oxide emissions (1308 parts per million) whereas a 50% ammonia-hydrogen blend yields the maximum nitrogen oxide output (7022 parts per million) attributable to the nitrogen content in ammonia. Hydrogen generates the minimal nitrogen oxide emissions per unit of energy output—approximately 0.1 grams per kilowatt-hour at a residence time of five milliseconds. This study integrates reactor-level study with a high-fidelity modeling tool providing insights for combustor design fuel selection and emissions control strategies in low-carbon aircraft and power systems.

Hydrogen-based mobility solutions could offer viable technology for sustainable transportation. Current research often examines single pathways leaving broader comparisons unexplored. This comparative life cycle assessment (LCA) evaluates which vehicle type achieves the best environmental performance when using hydrogen from grey blue and green production pathways the three dominant carbon-intensity variants currently deployed. This study examines seven distinct vehicle configurations that rely on hydrogen-derived energy sources across various propulsion systems: a hydrogen fuel cell electric vehicle (H2FCEV) hydrogen internal combustion engine vehicle (H2ICEV) methanol flexible fuel vehicle (MeOH FFV) ethanol flexible vehicle (EtOH FFV) Fischer-Tropsch (FT) diesel internal combustion vehicle (FTD ICEV) and renewable compressed natural gas vehicle (RNGV). Via both grey and blue hydrogen production H2 FCEVs are the best options from the viewpoint of GWP but surprisingly in the green category FT-fueled vehicles take over both first and second place as they produce nearly half the lifetime carbon emissions of purely hydrogen-fueled vehicles. RNGV also emerges as a promising alternative offering optimal engine properties in a system similar to H2ICEVs enabling parallel development and technological upgrades. These findings not only highlight viable low-carbon pathways but also provide clear guidance for future targeted detailed applied research.