Denmark

The goals of the long-term tests were to see the impact of blends of hydrogen and natural gas on the technical condition of the appliances and their performance after several hours of operation. To do so they were run through an accelerated test program amounting to more than 3000 testing hours for the boilers and more than 2500 testing hours for the cookers. The percentage of hydrogen in the test gas was 30% by volume. Three boilers and two cookers were tested by DGC and two boilers by GWI. This report describes the test protocol the results and analysis on the seven appliances tested.

The world is undergoing a substantial energy transition with an increasing share of intermittent sources of energy on the grid which is increasing the challenges to operate the power grid reliably. An option that has been receiving much focus after the COVID pandemic is the development of a hydrogen economy. Challenges for a hydrogen economy are the high investment costs involved in compression storage and long-distance transportation. This paper analyses an innovative proposal for the creation of hydrogen ocean links. It intends to fill existing gaps in the creation of a hydrogen economy with the increase in flexibility and viability for hydrogen production consumption compression storage and transportation. The main concept behind the proposals presented in this paper consists of using the fact that the pressure in the deep sea is very high which allows a thin and cheap HDPE tank to store and transport large amounts of pressurized hydrogen in the deep sea. This is performed by replacing seawater with pressurized hydrogen and maintaining the pressure in the pipes similar to the outside pressure. Hydrogen Deep Ocean Link has the potential of increasing the interconnectivity of different regional energy grids into a global sustainable interconnected energy system.

Hydrogen production is the key in utilizing an excess renewable energy. Many studies and projects looked at the energy management systems (EMSs) that allow to couple hydrogen production with renewable generation. In the majority of these studies however hydrogen demand is either produced for powering fuel cells or sold to the external hydrogen market. Hydrogen demand from actual industrial plants is rarely considered. In this paper we propose an EMS based on the industrial cluster of GreenLab Skive (GLS) that can minimize the system’s operational cost or maximize its green hydrogen production. EMS utilizes a conventional and P2X demand response (DR) flexibility from electrolysis plant hydrogen storage tank electric battery and hydrogen-consuming plants to design the optimal schedule with maximized benefits. A potential addition to the existing components at GLS - an ammonia plant is modelled to identify its P2X potential and assess the economic viability of its construction. The results show a potential reduction of 51.5–61.6% for the total operational cost of the system and an increase of the share of green hydrogen by 10.4–37.6% due to EMS operation.

The Danish government plans two energy islands to collect offshore wind power for power distribution and green fuel production. Wind power is often criticized for lacking stability which challenges downstream fuel synthesis processes. Solid oxide electrolysis cells (SOEC) are promising for green hydrogen production on a commercial scale but the impact of fluctuating power on SOEC remains uncertain. This paper explores the feasibility of a Wind-SOEC coupled system by conducting a 2104-h durability test with the state-of-the-art Topsoe TSP-1 stack. Three periods of steady operation and two periods of dynamic operation were conducted. Wind power fluctuation was simulated during the dynamic period and two control strategies were used to handle it. The constant flow (CF) and constant conversion (CC) strategies maintain the feedstock flow rate and conversion ratio of steamto‑hydrogen respectively. Compared to steady operation the stack shows no signs of additional degradation in dynamic operation. Thus the TSP-1 stack has been proven robust and flexible enough to handle fluctuating wind power supplies under both operation strategies. Further stack performance during dynamic periods was compared and analyzed by removing degradation effects. Accordingly SOEC stacks with CC control will consume less external heat than CF to maintain a heat balance. Nevertheless SOEC systems with CF and CC control strategies may have different efficiency or hydrogen production costs. Tech-economic analyses will be needed to investigate control strategies at the system level.

This paper presents a day-ahead economic optimization scheduling model for Regional Electricity–Hydrogen Integrated Energy System (REHIES) with high penetration of renewable energies. The electricity–hydrogen coupling devices are modelled with energy storage units and Insensitive Electrical Load (ISEL). The proposed objective function is able to capture the maximum benefits for REHIES in terms of economic benefits and can be summarized as a Quadratic Programming (QP) problem. The simulation verification is performed by MATLAB/CPLEX solver. The simulation results show that the proposed optimization model adapts the market requirement by contributing flexible collaboration between electricity and hydrogen. Also the translational properties of ISEL can implement higher economic profits and more effective utilization of renewable energy.

Hydrogen is believed as a promising energy carrier that contributes to deep decarbonization especially for the sectors hard to be directly electrified. A grid-connected wind/hydrogen system is a typical configuration for hydrogen production. For such a system a critical barrier lies in the poor cost-competitiveness of the produced hydrogen. Researchers have found that flexible operation of a wind/hydrogen system is possible thanks to the excellent dynamic properties of electrolysis. This finding implies the system owner can strategically participate in day-ahead power markets to reduce the hydrogen production cost. However the uncertainties from imperfect prediction of the fluctuating market price and wind power reduce the effectiveness of the offering strategy in the market. In this paper we proposed a decision-making framework which is based on data-driven robust chance constrained programming (DRCCP). This framework also includes multi-layer perception neural network (MLPNN) for wind power and spot electricity price prediction. Such a DRCCP-based decision framework (DDF) is then applied to make the day-ahead decision for a wind/hydrogen system. It can effectively handle the uncertainties manage the risks and reduce the operation cost. The results show that for the daily operation in the selected 30 days offering strategy based on the framework reduces the overall operation cost by 24.36% compared to the strategy based on imperfect prediction. Besides we elaborate the parameter selections of the DRCCP to reveal the best parameter combination to obtain better optimization performance. The efficacy of the DRCCP method is also highlighted by the comparison with the chance-constrained programming method.

For the usage of domestic gas meters with combustible gases like hydrogen natural gas or mixtures of hydrogen and natural gas in public grids the metrological behaviour of the gas meters has to fulfil the requirements described in the Measuring Instrument Directive (MID). The MID requires also that a measuring instrument shall be suitable for the application. The tightness of a meter is required in order to obtain correct results in case of accuracy tests but also for an application in the grid or for durability tests to avoid risks such as explosive gas mixtures. Due to the different properties of renewable gases leak tightness to one gas mixtures does not necessarily imply leak tightness for other gases. Hydrogen molecules are smaller than those in conventional natural gas which can more easily result in a gas leakage. The EMPIR project NEWGASMET includes beside metrological investigations also a durability test with hydrogen. In order to carry out these activities but also for further hydrogen leakage investigations for instance the investigation of proper seal materials used in the gas meter installation a reliable gas tightness test was developed.

To achieve the Net-Zero Emissions goal by 2050 a major upscale in green hydrogen needs to be achieved; this will also facilitate use of renewable electricity as a source of decarbonised fuel in hard-to-abate sectors such as industry and transport. Nearly 80% of the world’s offshore wind resource is in waters deeper than 60 m where bottom-fixed wind turbines are not feasible. This creates a significant opportunity to couple the high capacity factor floating offshore wind and green hydrogen. In this paper we consider dedicated large-scale floating offshore wind farms for hydrogen production with three coupling typologies; (i) centralised onshore electrolysis (ii) decentralised offshore electrolysis and (iii) centralised offshore electrolysis. The typology design is based on variables including for: electrolyser technology; floating wind platform; and energy transmission vector (electrical power or offshore hydrogen pipelines). Offshore hydrogen pipelines are assessed as economical for large and distant farms. The decentralised offshore typology employing a semi-submersible platform could accommodate a proton exchange membrane electrolyser on deck; this would negate the need for an additional separate structure or hydrogen export compression and enhance dynamic operational ability. It is flexible; if one electrolyser (or turbine) fails hydrogen production can easily continue on the other turbines. It also facilities flexibility in further expansion as it is very much a modular system. Alternatively less complexity is associated with the centralised offshore typology which may employ the electrolysis facility on a separate offshore platform and be associated with a farm of spar-buoy platforms in significant water depth locations.

Since the 1970s hydrogen has been considered as a possible energy carrier for the storage of renewable energy. The main focus has been on addressing the ultimate challenge: developing an environmentally friendly successor for gasoline. This very ambitious goal has not yet been fully reached as discussed in this review but a range of new lightweight hydrogen-containing materials has been discovered with fascinating properties. State-of-the-art and future perspectives for hydrogen-containing solids will be discussed with a focus on metal borohydrides which reveal significant structural flexibility and may have a range of new interesting properties combined with very high hydrogen densities.

The pressure swing adsorption (PSA) system is widely applied to separate and purify hydrogen from gaseous mixtures. The extended Langmuir equation fitted from the extended Langmuir-Freundlich isotherm has been used to predict the adsorption isothermal of hydrogen and methane on the zeolite 5A adsorbent bed. A six-step two-bed PSA model for hydrogen purification is developed and validated by comparing its simulation results with other works. The effects of the adsorption pressure the P/F ratio the adsorption step time and the pressure equalization time on the performance of the hydrogen purification system are studied. A four-step two-bed PSA model is taken into consideration and the six-step PSA system shows higher about 13% hydrogen recovery than the four-step PSA system. The performance of the vacuum pressure swing adsorption (VPSA) system is compared with that of the PSA system the VPSA system shows higher hydrogen purity than the PSA system. Based on the validated PSA model a dataset has been produced to train the artificial neural network (ANN) model. The effects of the number of neurons in the hidden layer and the number of samples used for training ANN model on the predicted performance of ANN model are investigated. Then the well-trained ANN model with 6 neurons in the hidden layer is applied to predict the performance of the PSA system for hydrogen purification. Multi-objective optimization of hydrogen purification system is performed based on the trained ANN model. The artificial neural network can be considered as a very effective method for predicting and optimizing the performance of the PSA system for hydrogen purification.

The paper presents the first outcomes of the experimental numerical and theoretical studies performed in the funded by Fuel Cell and Hydrogen Joint Undertaking (FCH2 JU) project HyTunnel-CS. The project aims to conduct pre-normative research (PNR) to close relevant knowledge gaps and technological bottlenecks in the provision of safety of hydrogen vehicles in underground transportation systems. Pre normative research performed in the project will ultimately result in three main outputs: harmonised recommendations on response to hydrogen accidents recommendations for inherently safer use of hydrogen vehicles in underground traffic systems and recommendations for RCS. The overall concept behind this project is to use inter-disciplinary and inter-sectoral prenormative research by bringing together theoretical modelling and experimental studies to maximise the impact. The originality of the overall project concept is the consideration of hydrogen vehicle and underground traffic structure as a single system with integrated safety approach. The project strives to develop and offer safety strategies reducing or completely excluding hydrogen-specific risks to drivers passengers public and first responders in case of hydrogen vehicle accidents within the currently available infrastructure.

The concerns over food security and protein scarcity driven by population increase and higher standards of living have pushed scientists toward finding new protein sources. A considerable proportion of resources and agricultural lands are currently dedicated to proteinaceous feed production to raise livestock and poultry for human consumption. The 1st generation of microbial protein (MP) came into the market as land-independent proteinaceous feed for livestock and aquaculture. However MP may be a less sustainable alternative to conventional feeds such as soybean meal and fishmeal because this technology currently requires natural gas and synthetic chemicals. These challenges have directed researchers toward the production of 2nd generation MP by integrating renewable energies anaerobic digestion nutrient recovery biogas cleaning and upgrading carbon-capture technologies and fermentation. The fermentation of methane-oxidizing bacteria (MOB) and hydrogen-oxidizing bacteria (HOB) i.e. two protein rich microorganisms has shown a great potential on the one hand to upcycle effluents from anaerobic digestion into protein rich biomass and on the other hand to be coupled to renewable energy systems under the concept of Power-to-X. This work compares various production routes for 2nd generation MP by reviewing the latest studies conducted in this context and introducing the state-of-the-art technologies hoping that the findings can accelerate and facilitate upscaling of MP production. The results show that 2nd generation MP depends on the expansion of renewable energies. In countries with high penetration of renewable electricity such as Nordic countries off-peak surplus electricity can be used within MP-industry by supplying electrolytic H2 which is the driving factor for both MOB and HOB-based MP production. However nutrient recovery technologies are the heart of the 2nd generation MP industry as they determine the process costs and quality of the final product. Although huge attempts have been made to date in this context some bottlenecks such as immature nutrient recovery technologies less efficient fermenters with insufficient gas-to-liquid transfer and costly electrolytic hydrogen production and storage have hindered the scale up of MP production. Furthermore further research into techno-economic feasibility and life cycle assessment (LCA) of coupled technologies is still needed to identify key points for improvement and thereby secure a sustainable production system.

Power-to-X is one of the most attention-grabbing topics in the energy sector. Researchers are exploring the potential of harnessing power from renewable technologies and converting it into fuels used in various industries and the transportation sector. With the current market and research emphasis on Power-to-X and the accompanying substantial investments a review of Power-to-X is becoming essential. Optimization will be a crucial aspect of managing an energy portfolio that includes Power-to-X and electrolysis systems as the electrolyzer can participate in multiple markets. Based on the current literature and published reviews none of them adequately showcase the state-of-the-art optimization algorithms for energy portfolios focusing on Power-to-X. Therefore this paper provides an in-depth review of the optimization algorithms applied to energy portfolios with a specific emphasis on Power-to-X aiming to uncover the current state-of-the-art in the field.

Instead of storing the energy produced by photovoltaic panels in batteries for later use to power electric loads green hydrogen can also be produced and used in transportation heating and as a natural gas alternative. Green hydrogen is produced in a process called electrolysis. Generally the electrolyser can generate hydrogen from a fluctuating power supply such as renewables. However due to the startup time of the electrolyser and electrolyser degradation accelerated by multiple shutdowns an idle mode is required. When in idle mode the electrolyser uses 10% of the rated electrolyser load. An energy management system (EMS) shall be applied where a storage technology such as a lithium-ion capacitor or lithium-ion battery is used. This paper uses a state-machine EMS of PV microgrid for green hydrogen production and energy storage to manage the hydrogen production during the morning from solar power and in the night using the stored energy in the energy storage which is sized for different scenarios using a lithium-ion capacitor and lithium-ion battery. The mission profile and life expectancy of the lithium-ion capacitor and lithium-ion battery are evaluated considering the system’s local irradiance and temperature conditions in the Australian climate. A tradeoff between storage size and cutoffs of hydrogen production as variables of the cost function is evaluated for different scenarios. The lithium-ion capacitor and lithium-ion battery are compared for each tested scenario for an optimum lifetime. It was found that a lithium-ion battery on average is 140% oversized compared to a lithium-ion capacitor but a lithium-ion capacitor has a smaller remaining capacity of 80.2% after ten years of operation due to its higher calendar aging while LiB has 86%. It was also noticed that LiB is more affected by cycling aging while LiC is affected by calendar aging. However the average internal resistance after 10 years for the lithium-ion capacitor is 264% of the initial internal resistance while for lithium-ion battery is 346% making lithium-ion capacitor a better candidate for energy storage if it is used for grid regulation as it requires maintaining a lower internal resistance over the lifetime of the storage.

Hydrogen is commonly mentioned as a future proof energy carrier. Hydrogen supporters 6 advocate for repurposing existing natural gas grids for a sustainable hydrogen supply. While the 7 long-term vision of the hydrogen community is green hydrogen the community acknowledges that 8 in the short term it will be to large extent manufactured from natural gas but in a decarbonized 9 way giving it the name blue hydrogen. While hydrogen has a role to play in hard to decarbonize 10 sectors its role for building heating demands is doubtful as mature and more energy efficient alter- 11 natives exist. As building heat supply infrastructures built today will operate for the decades to 12 come it is of highest importance to ensure that the most efficient and sustainable infrastructures are 13 chosen. This paper compares the source to sink efficiencies of hydrogen-based heat supply system 14 to a district heating system operating on the same primary energy source. The results show that a 15 natural gas-based district heating could be 267% more efficient and consequently have significantly 16 lower global warming potential than a blue hydrogen-based heat supply A renewable power-based 17 district heating could achieve above 440% higher efficiency than green hydrogen-based heat supply 18 system.

Hydrogen is often suggested as a universal fuel that can replace fossil fuels. This paper analyses the feasibility of direct hydrogen utilisation in all energy sectors in a 100% renewable energy system for Europe in 2050 using hour-by-hour energy system analysis. Our results show that using hydrogen for heating purposes has high costs and low energy efficiency. Hydrogen for electricity production is beneficial only in limited quantities to restrict biomass consumption but increases the system costs due to losses. The transport sector results show that hydrogen is an expensive alternative to liquid e-fuels and electrified transport due to high infrastructure costs and respectively low energy efficiency. The industry sector may benefit from hydrogen to reduce biomass at a lower cost than in the other energy sectors but electrification and e-methane may be more feasible. Seen from a systems perspective hydrogen will play a key role in future renewable energy systems but primarily as e-fuel feedstock rather than direct end-fuel in the hard-to-abate sectors.

With the rise of hydrogen use in the natural gas grid a need exists for reliable measurements of the amount of energy being transported and traded for hydrogen admixtures. Using VSL’s high-pressure Gas Oil Piston Prover (GOPP) primary standard the effect of mixing hydrogen with natural gas on the performance of a high-pressure gas flow meter was investigated. The error of a rotary flow meter was determined using the best possible uncertainty by calibration with the primary standard for high-pressure natural gas flow. The rotary flow meter was calibrated using both natural gas and hydrogen enriched natural gas (nominally 15% hydrogen) at two different pressures: 9 and 16 bar. Results indicate that for the rotary flow meter and hydrogen admixtures used the differences in the meter errors between high-pressure hydrogen-enriched natural gas calibration and high-pressure natural gas calibration are smaller than the corresponding differences between atmospheric pressure air calibration and high-pressure natural gas calibration.

Hydrogen can be key in the energy system transition. We investigate the role of offshore hydrogen generation in a future integrated energy system. By performing energy system optimisation in a model application of the Northern-central European energy system and the North Sea offshore grid towards 2050 we find that offshore hydrogen generation may likely only play a limited role and that offshore wind energy has higher value when sent to shore in the form of electricity. Forcing all hydrogen generation offshore would lead to increased energy system costs. Under the assumed scenario conditions which result in deep decarbonisation of the energy system towards 2050 hydrogen generation – both onshore and offshore – follows solar PV generation patterns. Combined with hydrogen storage this is the most cost-effective solution to satisfy future hydrogen demand. Overall we find that the role of future offshore hydrogen generation should not simply be derived from minimising costs for the offshore sub-system but by also considering the economic value that such generation would create for the whole integrated energy system. We find as a no-regret option to enable and promote the integration of offshore wind in onshore energy markets via electrical connections.

Hydrogen storage is one of the energy storage methods that can help realization of an emission free future by saving surplus renewable energy for energy deficit periods. Utilization of depleted hydrocarbon reservoirs for large-scale hydrogen storage may be associated with the risk of chemical/biochemical reactions. In the specific case of chalk reservoirs the principal reactions are abiotic calcite dissolution acetogenesis methanogenesis and biological souring. Here we use PHREEQC to evaluate the dynamics and the extent of hydrogen loss by each of these reactions in hydrogen storage scenarios for various Danish North Sea chalk hydrocarbon reservoirs. We find that: (i) Abiotic calcite dissolution does not occur in the temperature range of 40-180◦ C. (ii) If methanogens and acetogens grow as slow as the slowest growing methanogens and acetogens reported in the literature methanogenesis and acetogenesis cannot cause a hydrogen loss more than 0.6% per year. However (iii) if they proceed as fast as the fastest growing methanogens and acetogens reported in the literature a complete loss of all injected hydrogen in less than five years is possible. (iv) Co-injection of CO2 can be employed to inhibit calcite dissolution and keep the produced methane due to methanogenesis carbon neutral. (v) Biological sulfate reduction does not cause significant hydrogen loss during 10 years but it can lead to high hydrogen sulfide concentrations (1015 ppm). Biological sulfate reduction is expected to impact hydrogen storage only in early stages if the only source of sulfur substrates are the dissolved species in the brine and not rock minerals. Considering these findings we suggest that depleted chalk reservoirs may not possess chemical/biochemical risks and be good candidates for large-scale underground hydrogen storage.

Carbon dioxide (CO2 ) and hydrogen (H2 ) are essential energy vectors in the green energy transition. H2 is a fuel produced by electrolysis and is applied in heavy transportation where electrification is not feasible yet. The pollutant substance CO2 is starting to be captured and stored in different European locations. In Denmark the energy vision aims to use this CO2 to be reacted with H2 producing green methanol. Typically the production units are not co-located with consumers and thus the required transportation infrastructure is essential for meeting supply and demand. This work presents a novel scheme to allocate the transportation costs of CO2 and H2 in pipeline networks which can be applied to any network topology and with any allocation method. During the tariff formation process coordinated adjustments are made by the novel scheme on the original tariffs produced by the allocation method employed considering the location of each customer connected to pipeline network. Locational tariffs are provided as result and the total revenue recovery is guaranteed to the network owner. Considering active customers the novel scheme will lead to a decrease of distant pipeline flows thereby contributing to the prevention of bottlenecks in the transportation network. Thus structural reinforcements can be avoided reducing the total transportation cost paid by all customers in the long-term.

Hydrogen has emerged in the context of large-scale renewable uptake and deep decarbonization. However the high cost of splitting water into hydrogen using renewable energy hinders the development of green hydrogen. Here we provide a cost analysis of hydrogen from off-grid wind. It is found that the current cost evaluation can be improved by examining the operational details of electrolysis. Instead of using low-resolution wind-speed data and linear electrolysis models we generate 5-min resolution wind data and utilize detailed electrolysis models that can describe the safe working range startup time and efficiency variation. Economic assessments are performed over 112 locations in seven countries to demonstrate the influence of operational models. It is shown that over-simplified models lead to less reliable results and the relative error can be 63.65% at most. Further studies have shown the global picture of producing green hydrogen. Based on the improved model we find that the levelized cost of hydrogen ranges from 1.66$/kg to 13.61$/kg. The wind-based hydrogen is cost-competitive in areas with abundant resources and lower investment cost such as China and Denmark. However it is still costly in most of the studied cases. An optimal sizing strategy or involving a battery as electricity storage can further reduce the hydrogen cost the effectiveness of which is location-specific. The sizing strategies of electrolyzers differ by country and rely on the specific wind resource. In contrast the sizing of batteries presents similar trends. Smaller batteries are preferred in almost all the investigated cases.

The design of future energy systems requires the efficient use of all available renewable resources. Biomass can complement variable renewable energy sources by ensuring energy system flexibility and providing a reliable feedstock to produce renewable fuels. We identify biomass gasification suitable to utilise the limited biomass resources efficiently. In this study we inquire about its role in a 100% renewable energy system for Denmark and a net-zero energy system for Europe in the year 2050 using hourly energy system analysis. The results indicate bio-electrofuels produced from biomass gasification and electricity to enhance the utilisation of wind and electrolysis and reduce the energy system costs and fuels costs compared to CO2-electrofuels from carbon capture and utilisation. Despite the extensive biomass use overall biomass consumption would be higher without biomass gasification. The production of electromethanol shows low biomass consumption and costs while Fischer-Tropsch electrofuels may be an alternative for aviation. Syngas from biomass gasification can supplement biogas in stationary applications as power plants district heat or industry but future energy systems must meet a balance between producing transport fuels and syngas for stationary units. CO2-electrofuels are found complementary to bio-electrofuels depending on biomass availability and remaining non-fossil CO2 emitters

Ports are critical hubs in the global supply chain yet they face mounting challenges in achieving carbon neutrality. Port Integrated Multi-Energy Systems (PIMESs) offer a comprehensive solution by integrating renewable energy sources such as wind photovoltaic (PV) hydrogen and energy storage with traditional energy systems. This study examines the implementation of a real-word PIMES showcasing its effectiveness in reducing energy consumption and emissions. The findings indicate that in 2024 the PIMES enabled a reduction of 1885 tons of CO2 emissions with wind energy contributing 84% and PV 16% to the total decreases. The energy storage system achieved a charge–discharge efficiency of 99.15% while the hydrogen production system demonstrated an efficiency of 63.34% producing 503.87 Nm3/h of hydrogen. Despite these successes challenges remain in optimizing renewable energy integration expanding storage capacity and advancing hydrogen technologies. This paper highlights practical strategies to enhance PIMESs’ performances offering valuable insights for policymakers and port authorities aiming to balance energy efficiency and sustainability and providing a blueprint for carbon-neutral port development worldwide.

As the European countries strive to meet their ambitious climate goals renewable hydrogen has emerged to aid in decarbonizing energy-intensive sectors and support the overall energy transition. To ensure that hydrogen production aligns with these goals the European Commission has introduced criteria for additionality temporal correlation and geographical correlation. These criteria are designed to ensure that hydrogen production from renewable sources supports the growth of renewable energy. This study assesses the impact of these criteria on green hydrogen production focusing on production costs and technology impacts. The European energy market is simulated up to 2048 using stochastic programming applying these requirements exclusively to green hydrogen production without the phased-in compliance period outlined in the EU regulations. The findings show that meeting the criteria will increase expected system costs by €82 billion from 2024 to 2048 largely due to the rapid shift from fossil fuels to renewable energy. The additionality requirement which mandates the use of new renewable energy installations for electrolysis proves to be the most expensive but also the most effective in accelerating renewable energy adoption.

With the rapid development of alternative fuel vehicles (AFVs) and renewable energy sources the increasing coordination between electric vehicles (EVs) and hydrogen vehicles (HVs) in urban coupled powertransportation networks (CPTNs) fosters optimized energy scheduling and enhanced system performance. This study proposes a two-level Stackelberg-Nash game framework for AFV-integrated microgrids in a CPTN to enhance the economic efficiency of microgrid. This framework employs a Stackelberg game model to define the leader-follower relationship between the microgrid operator and the vehicle-to-grid (V2G) aggregator. Nash equilibrium games are established to capture competitive interactions among charging stations (CSs) and among hydrogen refueling stations (HRSs). Furthermore an optimal scheduling model is proposed to minimize microgrid operation costs considering the spatiotemporal dynamics and user preferences of EVs and HVs supported by the proposed dynamic choice model. A game-theoretic pricing and incentive mechanism promotes AFV participation in V2G services enhancing the profitability of CSs and HRSs. Afterward a momentum-enhanced Stackelberg-Nash equilibrium algorithm is developed to address the bi-level optimization problem. Finally numerical simulations validate the effectiveness of the proposed method in improving economic efficiency and reducing operation costs. The proposed approach offers an effective solution for integrating large-scale AFV fleets into sustainable urban energy and transportation systems.