Applications & Pathways

The integrated energy system with electric vehicles can realize multi-energy coordination and complementarity and effectively promote the realization of low-carbon environmental protection goals. However the temporary change of vehicle travel plan will have an adverse impact on the system. Therefore a multi-layer coordinated optimization strategy of electric-thermal-hydrogen integrated energy system including vehicle to grid (V2G) load feedback correction is proposed. The strategy is based on the coordination of threelevel optimization. The electric vehicle charging and discharging management layer comprehensively considers the variance of load curve and the dissatisfaction of vehicle owners and the charging and discharging plan is obtained through multi-objective improved sparrow search algorithm which is transferred to the model predictive control rolling optimization layer. In the rolling optimization process according to the actual situation selectively enter the V2G load feedback correction layer to update V2G load so as to eliminate the impact of temporary changes in electric vehicle travel plans. Simulation results show that the total operating cost with feedback correction is 4.19% lower than that without feedback correction and tracking situation of tie-line planned value is improved which verifies the proposed strategy.

Building heating is one of the sectors for which multiple decarbonisation options exist and current geopolitical tensions provide urgency to design adequate regional policies. Heat pumps and hydrogen boilers alongside alternative district heating systems are the most promising alternatives. Although a host of city or country-level studies exist it remains controversial what role hydrogen should play for building heating in the European Union compared with electrification and how blue and green hydrogen differ in terms of costs and environmental impacts. This works assesses the optimal technology mix for staying within planetary boundaries and the influence of international cooperation and political restrictions. To perform the analysis a bottom-up optimisation model was developed incorporating life cycle assessment constraints and covering production storage transport of energy and carbon dioxide as well as grid and non-grid connected end-users of heat. It was found that a building heating system within planetary boundaries is feasible through large-scale electrification via heat pumps although at a higher cost than the current system with abatement costs of around 200 €/ton CO2. Increasing interconnector capacity or onshore wind energy is found to be vital to staying within boundaries. A strong trade-off for hydrogen was identified with blue hydrogen being cost-competitive but vastly unsustainable (when applied to heating) and green hydrogen being 2–3 times more expensive than electrification while still transgressing several planetary boundaries. The insights from this work indicate that heat pumps and renewable electricity should be prioritised over hydrogen-based heating in most cases and grid-stability and storage aspects explored further while revealing a need for policy instruments to mitigate increased costs for consumers.

This paper presents the application of a multidisciplinary approach for the preliminary design and evaluation of the potential improvements in performance and environmental impact through the utilization of compressed (CGH2) and liquefied (LH2) hydrogen fuel for a civil tilt-rotor modelled after the NASA XV-15. The methodology deployed comprises models for rotorcraft flight dynamics engine performance flight path analysis hydrogen tank and thermal management system sizing. Trade-offs between gravimetric efficiency energy consumption fuel burn CO2 emissions and cost are quantified and compared to the kerosene-fuelled rotorcraft. The analysis carried out suggests that for these vehicle scales gravimetric efficiencies of the order of 13% and 30% can be attained for compressed and liquid hydrogen storage respectively leading to reduced range capability relative to the baseline tilt-rotor by at least 40%. At mission level it is shown that the hydrogen-fuelled configurations result in increased energy consumption by at least 12% (LH2) and 5% (CGH2) but at the same time significantly reduced life-cycle carbon emissions compared to the kerosene counterpart. Although LH2 storage at cryogenic conditions has a higher gravimetric efficiency than CGH2 (at 700 bar) it is shown that for this class of rotorcraft the latter is more energy efficient when the thermal management system for fuel pressurization and heating prior to combustion is accounted for.

According to the specific requirements of railway engineering a techno-economic comparison for onboard hydrogen storage technologies is conducted to discuss their feasibility and potentials for hydrogen-powered hybrid trains. Physical storage methods including compressed hydrogen (CH2 ) liquid hydrogen (LH2 ) and cryo-compressed hydrogen (CcH2 ) and material-based (chemical) storage methods such as ammonia liquid organic hydrogen carriages (LOHCs) and metal hydrides are carefully discussed in terms of their operational conditions energy capacity and economic costs. CH2 technology is the most mature now but its storage density cannot reach the final target which is the same problem for intermetallic compounds. In contrast LH2 CcH2 and complex hydrides are attractive for their high storage density. Nevertheless the harsh working conditions of complex hydrides hinder their vehicular application. Ammonia has advantages in energy capacity utilisation efficiency and cost especially being directly utilised by fuel cells. LOHCs are now considered as a potential candidate for hydrogen transport. Simplifying the dehydrogenation process is the important prerequisite for its vehicular employment. Recently increasing novel hydrogen-powered trains based on different hydrogen storage routes are being tested and optimised across the world. It can be forecasted that hydrogen energy will be a significant booster to railway decarbonisation.

The use of autonomous vehicles for marine and submarine work has risen considerably in the last decade. Developing new monitoring systems navigation and communications technologies allows a wide range of operational possibilities. Autonomous Underwater Vehicles (AUVs) are being used in offshore missions and applications with some innovative purposes by using sustainable and green energy sources. This paper considers an AUV that uses a hydrogen fuel cell achieving zero emissions. This paper analyses the life cycle cost of the UAV and compares it with a UAV powered by conventional energy. The EN 60300-3-3 guidelines have been employed to develop the cost models. The output results show estimations for the net present value under different scenarios and financial strategies. The study has been completed with the discount rate sensibility analysis in terms of financial viability.

Europe’s aviation sector continues its resilient and pioneering spirit as it leads the world’s transport system into its new era of great transformation. Surviving the pandemic it is adapting rapidly to satisfy the rising demand for competitive air mobility services while managing a scarcity of resources and embracing the new challenges of climate change and energy transition. Facilitated by ACARE the European Commission its Member States aviation research organisations design and manufacturing industries airlines airports and aviation energy and service providers have all joined together to envision a synchronized transformation path that will ensure that Europe can lead the world towards a climate neutral citizen centric and competitive air mobility system. “Fly the Green Deal” is Europe’s Vision for Sustainable Aviation. It describes the actions and actors necessary towards aviation’s three main strategic goals. It details three time horizons and defines as well the requirement for a proactive and synchronised implementation framework facilitated by the European Commission and EU Member States that includes both the initiating instruments (policies regulations and incentives) and a system of measuring and impact monitoring to ensure the goals are achieved.

The objective of this paper is to design and simulate for rural areas isolated from the electricity grid a system based on solar energy for the optimal supply of green electricity and medical oxygen to a hospital. The system sized to produce 20 Nm3 /day is constituted of a 37.46 kW photovoltaic farm a 15.47 kW electrolyzer and a 15.47 kW fuel cell. The simulation of the Photovoltaic system is performed using the single diode model solved with the Lambert function defined in MATLAB Software. The daily production of oxygen and hydrogen during the sunniest day of the month is respectively 20.81 Nm3 /day and 41.61 Nm3 /day. The daily energy that can be stored is relevant to the hydrogen production and an electricity storage capacity of 124.89 kWh is feasible. During the least sunny day of the least sunny month the daily production of oxygen and hydrogen is respectively 7.72 Nm3 /day and 15.44 Nm3 /day. The recorded values prove that the system sized can constitute a viable solution to ensure the permanent supply a green electricity and oxygen to the hospital with good energy storage capacity.

Decarbonization of the steel industry is one of the pathways towards a fossil-fuel-free environment. The steel industry is one of the top contributors to greenhouse gas emissions. Most of these emissions are directly linked to the use of a fossil-fuelbased reductant. Replacing the fossil-based reductant with green H2 enables the transition towards a fossil-free steel industry. The carbon-free iron produced will cause the refining and steelmaking operations to have a starting point far from today’s operations. In addition to carbon being an alloying element in steel production carbon addition controls the melting characteristics of the reduced iron. In the present study the effect of carbon content and form (cementite/graphite) in hydrogen-reduced iron ore pellets on their melting characteristics was examined by means of a differential thermal analyser and optical dilatometer. Carburized samples with a carbon content < 2 wt % did not show any initial melting at the eutectic temperature. At and above 2 wt % the carburized samples showed an initial melting at the eutectic temperature irrespective of the carbon content. However the absorbed heat varies with varied carbon content. The carbon form does not affect the initial melting temperature but it affects the melting progression. Carburized samples melt homogenously while melting of iron-graphite mixtures occurs locally at the interface between iron and carbon particles and when the time is not long enough melting might not occur to any significant extent. Therefore at any given carbon content > 2 wt % the molten fraction is higher in the case of carburized samples which is indicated by the amount of absorbed melting heat.

Alternatives to cope with the challenges of high shares of renewable electricity in power systems have been addressed from different approaches such as energy storage and low-carbon technologies. However no model has previously considered integrating these technologies under stability requirements and different climate conditions. In this study we include this approach to analyse the role of new technologies to decarbonise the power system. The Spanish power system is modelled to provide insights for future applications in other regions. After including storage and low-carbon technologies (currently available and under development) batteries and hydrogen fuel cells have low penetration and the derived emission reduction is negligible in all scenarios. Compressed air storage would have a limited role in the short term but its performance improves in the long term. Flexible generation technologies based on hydrogen turbines and long-duration storage would allow the greatest decarbonisation providing stability and covering up to 11–14 % of demand in the short and long term. The hydrogen storage requirement is equivalent to 18 days of average demand (well below the theoretical storage potential in the region). When these solutions are considered decarbonising the electricity system (achieving Paris targets) is possible without a significant increase in system costs (< € 114/MWh).

The expected increase of hydrogen fuel cell vehicles has motivated the emergence of a significant number of studies on Hydrogen Refuelling Stations (HRS). Some of the main HRS topics are sizing location design optimization and optimal operation. On-site green HRS where hydrogen is produced locally from green renewable energy sources have received special attention due to their contribution to decarbonization. This kind of HRS are complex systems whose hydraulic and electric linked topologies include renewable energy sources electrolyzers buffer hydrogen tanks compressors and batteries among other components. This paper develops a linear model of a real on-site green HRS that is set to be built in Zaragoza Spain. This plant can produce hydrogen either from solar energy or from the utility grid and is designed for three different types of services: light-duty and heavy-duty fuel cell vehicles and gas containers. In the literature there is a lack of online control solutions developed for HRS even more in the form of optimal online control. Hence for the HRS operation a Model Predictive Controller (MPC) is designed to solve a weighted multi-objective online optimization problem taking into account the plant dynamics and constraints as well as the disturbances prediction. Performance is analysed throughout 210 individual month-long simulations and the effect of the multi-objective weighting prediction horizon and hydrogen selling price is discussed. With the simulation results this work shows the suitability of MPC for HRS control and its significant economic advantage compared to the rule-based control solution. In all simulations the MPC operation fulfils all required services. Moreover results show that a seven-day prediction horizon can improve profits by 57% relative to a one-day prediction horizon; that the battery is under-sized; or that the MPC operation strategy is more resolutive for low hydrogen selling prices.

Hydrogen consumption and mileage are important economic indicators of fuel cell vehicles. Hydrogen consumption is the fundamental reason that restricts mileage. Since there are few quantitative studies on hydrogen consumption during actual vehicle operation the high cost of hydrogen consumption in outdoor testing makes it impossible to guarantee the accuracy of the test. Therefore this study puts forward a test method based on the hydrogen consumption of fuel cell vehicles under CLTC-P operating conditions to test the hydrogen consumption of fuel cell vehicles per 100 km. Finally the experiment shows that the mileage calculated by hydrogen consumption has a higher consistency with the actual mileage. Based on this hydrogen consumption test method the hydrogen consumption can be accurately measured and the test time and cost can be effectively reduced.

With the clear adverse impacts of fossil fuel-based energy systems on the climate and environment ever-growing interest and rapid developments are taking place toward full or nearly full dependence on renewable energies in the next few decades. Estonia is a European country with large demands for electricity and thermal energy for district heating. Considering it as the case study this work explores the feasibility and full potential of optimally sized photovoltaic (PV) wind and PV/wind systems equipped with electric and thermal storage to fulfill those demands. Given the large excess energy from 100% renewable energy systems for an entire country this excess is utilized to first meet the district heating demand and then to produce hydrogen fuel. Using simplified models for PV and wind systems and considering polymer electrolyte membrane (PEM) electrolysis a genetic optimizer is employed for scanning Estonia for optimal installation sites of the three systems that maximize the fulfillment of the demand and the supply–demand matching while minimizing the cost of energy. The results demonstrate the feasibility of all systems fully covering the two demands while making a profit compared to selling the excess produced electricity directly. However the PV-driven system showed enormous required system capacity and amounts of excess energy with the limited solar resources in Estonia. The wind system showed relatively closer characteristics to the hybrid system but required a higher storage capacity by 75.77%. The hybrid PV/wind-driven system required a total capacity of 194 GW most of which belong to the wind system. It was also superior concerning the amount (15.05 × 109 tons) and cost (1.42 USD/kg) of the produced green hydrogen. With such full mapping of the installation capacities and techno-economic parameters of the three systems across the country this study can assist policymakers when planning different country-scale cogeneration systems.

We present a numerical simulation procedure for analyzing hydrogen oxygen and carbon dioxide gases injections mixed with pulverized coals within the tuyeres of blast furnaces. Effective use of H2 rich gas is highly attractive into the steelmaking blastfurnace considering the possibility of increasing the productivity and decreasing the specific emissions of carbon dioxide becoming the process less intensive in carbon utilization. However the mixed gas and coal injection is a complex technology since significant changes on the inner temperature and gas flow patterns are expected beyond to their effects on the chemical reactions and heat exchanges. Focusing on the evaluation of inner furnace status under such complex operation a comprehensive mathematical model has been developed using the multi interaction multiple phase theory. The BF considered as a multiphase reactor treats the lump solids (sinter small coke pellets granular coke and iron ores) gas liquids metal and slag and pulverized coal phases. The governing conservation equations are formulated for momentum mass chemical species and energy and simultaneously discretized using the numerical method of finite volumes. We verified the model with a reference operational condition using pulverized coal of 215 kg per ton of hot metal (kg thm−1). Thus combined injections of varying concentrations of gaseous fuels with H2 O2 and CO2 are simulated with 220 kg thm−1 and 250 kg thm−1 coals injection. Theoretical analysis showed that stable operations conditions could be achieved with productivity increase of 60%. Finally we demonstrated that the net carbon utilization per ton of hot metal decreased 12%.

Hydrogen has the potential to decarbonize a variety of energy-intensive sectors including steel production. Using the life cycle assessment (LCA) methodology the state of the art is given for current hydrogen production with a focus on the hydrogen carbon footprint. Beside the state of the art the outlook on different European scenarios up to the year 2040 is presented. A case study of the transformation of steel production from coal-based towards hydrogen- and electricity-based metallurgy is presented. Direct reduction plants with integrated electric arc furnaces enable steel production which is almost exclusively based on hydrogen and electricity or rather on electricity alone if hydrogen stems from electrolysis. Thus an integrated steel site has a demand of 4.9 kWh of electric energy per kilogram of steel. The carbon footprint of steel considering a European sustainable development scenario concerning the electricity mix is 0.75 kg CO2eq/kg steel in 2040. From a novel perspective a break-even analysis is given comparing the use of natural gas and hydrogen using different electricity mixes. The results concerning hydrogen production presented in this paper can also be transferred to application fields other than steel.

This paper reviews the relationship between the production of steel and the environment as it stands today. It deals with raw material issues (availability scarcity) energy resources and generation of by-products i.e. the circular economy the anthropogenic iron mine and the energy transition. The paper also deals with emissions to air (dust Particulate Matter heavy metals Persistant Organics Pollutants) water and soil i.e. with toxicity ecotoxicity epidemiology and health issues but also greenhouse gas emissions i.e. climate change. The loss of biodiversity is also mentioned. All these topics are analyzed with historical hindsight and the present understanding of their physics and chemistry is discussed stressing areas where knowledge is still lacking. In the face of all these issues technological solutions were sought to alleviate their effects: many areas are presently satisfactorily handled (the circular economy—a historical’ practice in the case of steel energy conservation air/water/soil emissions) and in line with present environmental regulations; on the other hand there are important hanging issues such as the generation of mine tailings (and tailings dam failures) the emissions of greenhouse gases (the steel industry plans to become carbon-neutral by 2050 at least in the EU) and the emission of fine PM which WHO correlates with premature deaths. Moreover present regulatory levels of emissions will necessarily become much stricter.

This study proposes a data-driven methodology for modeling power and hydrogen generation of a sustainable energy converter. The wave and hydrogen production at different wave heights and wind speeds are predicted. Furthermore this research emphasizes and encourages the possibility of extracting hydrogen from ocean waves. By using the extracted data from the FLOW-3D software simulation and the experimental data from the special test in the ocean the comparison analysis of two data-driven learning methods is conducted. The results show that the amount of hydrogen production is proportional to the amount of generated electrical power. The reliability of the proposed renewable energy converter is further discussed as a sustainable smart grid application.

Energy consumption is essential for evaluating the competitiveness of fuel cell electric vehicles. A critical step in energy consumption measurement is measuring hydrogen consumption including the mass method the P/T method and the flowmeter method. The flowmeter method has always been a research focus because of its simple operation low cost and solid real-time performance. Current research has shown the accuracy of the flowmeter method under specific conditions. However many factors in the real scenario will influence the test result such as unintended vibration environment temperature and onboard hydrogen capacity calibration. On the other hand the short-cut method is also researched to replace the run-out method to improve test efficiency. To evaluate whether the flowmeter method basing on the short-cut method can genuinely reflect the hydrogen consumption of an actual vehicle we research and test for New European Driving Cycle (NEDC) and China Light-Duty Vehicle Test Cycle (CLTC) using the same vehicle. The results show that the short-cut method can save at least 50% of the test time compared with the run-out method. The error of the short-cut method based on the flowmeter for the NEDC working condition is less than 0.1% and for the CLTC working conditions is 8.12%. After adding a throttle valve and a 4L buffer tank the error is reduced to 4.76% from 8.12%. The test results show that hydrogen consumption measurement based on the flowmeter and short-cut method should adopt corresponding solutions according to the scenarios.

Power-to-X processes where renewable energy is converted into storable liquids or gases are considered to be one of the key approaches for decarbonizing energy systems and compensating for the volatility involved in generating electricity from renewable sources. In this context the production of “green” hydrogen and hydrogen-based derivatives is being discussed and tested as a possible solution for the energy-intensive industry sector in particular. Given the sharp ongoing increases in electricity and gas prices and the need for sustainable energy supplies in production systems non-energy-intensive companies should also be taken into account when considering possible utilization paths for hydrogen. This work focuses on the following three utilization paths: “hydrogen as an energy storage system that can be reconverted into electricity” “hydrogen mobility” for company vehicles and “direct hydrogen use”. These three paths are developed modeled simulated and subsequently evaluated in terms of economic and environmental viability. Different photovoltaic system configurations are set up for the tests with nominal power ratings ranging from 300 kWp to 1000 kWp. Each system is assigned an electrolyzer with a power output ranging between 200 kW and 700 kW and a fuel cell with a power output ranging between 5 kW and 75 kW. There are also additional variations in relation to the battery storage systems within these basic configurations. Furthermore a reference variant without battery storage and hydrogen technologies is simulated for each photovoltaic system size. This means that there are ultimately 16 variants to be simulated for each utilization path. The results show that these utilization paths already constitute a reasonable alternative to fossil fuels in terms of costs in variants with a suitable energy system design. For the “hydrogen as an energy storage system” path electricity production costs of between 43 and 79 ct/kWh can be achieved with the 750 kWp photovoltaic system. The “hydrogen mobility” is associated with costs of 12 to 15 ct/km while the “direct hydrogen use” path resulted in costs of 8.2 €/kg. Environmental benefits are achieved in all three paths by replacing the German electricity mix with renewable energy sources produced on site or by substituting hydrogen for fossil fuels. The results confirm that using hydrogen as a storage medium in manufacturing companies could be economically and environmentally viable. These results also form the basis for further studies e.g. on detailed operating strategies for hydrogen technologies in scenarios involving a combination of multiple utilization paths. The work also presents the simulation-based method developed in this project which can be transferred to comparable applications in further studies.

Hydrogen has received much attention in the development of direct reduction of iron ores because hydrogen metallurgy is one of the effective methods to reduce CO2 emission in the iron and steel industry. In this study the kinetic mechanism of reduction of hematite particles was studied in a hydrogen atmosphere. The phases and morphological transformation of hematite during the reduction were characterized using X-ray diffraction and scanning electron microscopy with energy dispersive spectroscopy. It was found that porous magnetite was formed and the particles were degraded during the reduction. Finally sintering of the reduced iron and wüstite retarded the reductive progress. The average activation energy was extracted to be 86.1 kJ/mol and 79.1 kJ/mol according to Flynn-Wall-Ozawa (FWO) and Starink methods respectively. The reaction fraction dependent values of activation energy were suggested to be the result of multi-stage reactions during the reduction process. Furthermore the variation of activation energy value was smoothed after heat treatment of hematite particles.

In contrast to sustainable aviation fuels for use in conventional combustion engines hydrogen-electric powertrains constitute a fundamentally novel approach that requires extensive effort from various engineering disciplines. A transient system analysis has been applied to a 500 kW shaft-power-class powertrain. The model was fed with high-level system requirements to gain a fundamental understanding of the interaction between sub-systems and components. Transient effects such as delays in pressure build up heat transfer and valve operation substantially impact the safe and continuous operation of the propulsion system throughout a typical mission profile which is based on the Daher TBM850. The lumped-parameters network solver provides results quickly which are used to derive requirements for subsystems and components which support their in-depth future development. E.g. heat exchanger transfer rates and pressure drop of the motor's novel hydrogen cooling system are established. Furthermore improvements to the system architecture such as a compartmentalization of the tank are identified.

This paper analyzes the operation of an energy hub on a community level with an integrated P2X facility and with access to energy markets. In our case P2X allows converting power to hydrogen heat methane or back to power. We consider the energy hub as a large prosumer who can be both a producer and consumer in the markets with the novelty that P2X technology is available. We investigate how such a P2X energy hub trades optimally in the electricity market and satisfies local energy demand under the assumption of a long-term strong climate scenario in year 2050. For numerical analysis a case study of a mountain village in Switzerland is used. One of the main contributions of this paper is to quantify key conditions for profitable operations of such a P2X energy hub. In particular the analysis includes impacts of influencing factors on profits and operational patterns in terms of different degrees of self-sufficiency and different availability of local renewable resources. Moreover the access to real-time wholesale market electricity price signals and a future retail hydrogen market is assessed. The key factors for the successful operation of a P2X energy hub are identified to be sufficient local renewable resources and access to a retail market of hydrogen. The results also show that the P2X operation leads to an increased deployment of local renewables especially in the case of low initial deployment; on the other hand seasonal storage plays a subordinated role. Additionally P2X lowers for the community the wholesale electricity market trading volumes.

Low or even zero carbon dioxide emissions will be an essential requirement for energy supplies in the near future. Besides transport and electricity generation industry is another large carbon emitter. Hydrogen produced by renewable energy provides a flexible way of utilizing that energy. Hydrogen as an energy carrier could be stored in a large capacity compared to electricity. In Sweden hydrogen will be used to replace coal for steel production. This paper discusses how the need for electricity to produce hydrogen will affect the electricity supply and power flow in the Swedish power grid and whether it will result in increased emissions in other regions. Data of the Swedish system will be used to study the feasibility of implementing the hydrogen system from the power system viewpoint and discuss the electricity price and emission issues caused by the hydrogen production in different scenarios. This paper concludes that the Swedish power grid is feasible for accommodating the additional electricity capacity requirement of producing green hydrogen for the steel industry. The obtained results could be references for decision makers investors and power system operators.

Solid oxide fuel cells are an emerging energy conversion technology suitable for high-temperature power generation with proper auxiliary heat. Combining SOFCs and polygeneration has produced practical applications for modern energy system designs. Even though many researchers have reviewed these systems’ technologies opportunities and challenges reviews regarding the optimal strategy for designing and operating the systems are limited. Polygeneration is more complicated than any other energy generation type due to its ability to generate many types of energy from various prime movers. Moreover integration with other applications such as vehicle charging and fueling stations increases the complication in making the system optimally serve the loads. This study elaborates on the energy planning and guidelines for designing a polygeneration system especially for residential applications. The review of polygeneration technologies also aligns with the current research trend of developing green technology for modern and smart homes in residential areas. The proposed guideline is expected to solve the complication in other applications and technologies and design the polygeneration system optimally.

Green hydrogen produced using renewable energy is nowadays one of the most promising alternatives to fossil fuels for reducing pollutant emissions and in turn global warming. In particular the use of hydrogen as fuel for internal combustion engines has been widely analyzed over the past few years. In this paper the authors show the results of some experimental tests performed on a hydrogen-fueled CFR (Cooperative Fuel Research) engine with particular reference to the combustion. Both the air/fuel (A/F) ratio and the engine compression ratio (CR) were varied in order to evaluate the influence of the two parameters on the combustion process. The combustion duration was divided in two parts: the flame front development (characterized by laminar flame speed) and the rapid combustion phase (characterized by turbulent flame speed). The results of the hydrogen-fueled engine have been compared with results obtained with gasoline in a reference operating condition. The increase in engine CR reduces the combustion duration whereas the opposite effect is observed with an increase in the A/F ratio. It is interesting to observe how the two parameters CR and A/F ratio have a different influence on the laminar and turbulent combustion phases. The influence of both A/F ratio and engine CR on heat transfer to the combustion chamber wall was also evaluated and compared with the gasoline operation. The heat transfer resulting from hydrogen combustion was found to be higher than the heat transfer resulting from gasoline combustion and this is probably due to the different quenching distance of the two fuels.

Hydrogen may represents a good alternative fuel that can be used to fuel internal combustion engines in order to ameliorate energetic and emissions performance. The paper presents some experimental aspects registered at hydrogen use to fuel a diesel engine different substitute ratios being use in the area of 18–34% at 40% engine load and speed of 2000 rev/min. The engine is equipped with an open ECU and the control of the cyclic dosses of diesel fuel and hydrogen are adjusted in order to maintain the engine power performance. The in-cylinder pressure diagrams show the increase of the maximum pressure with 17% from 78.5 bar to 91.8 bar for the maximum substitute ratio. Also values of maximum pressure rise rate start to increase for hydrogen addition in correlation with the increase of fuel amount burned into the premixed stage without exceed the normal values with assure the normal and reliable engine operation. Higher Lower Heating Value and combustion speed of hydrogen assure the increase in thermal efficiency the brake specific energy consumption decreases with 5.4%–7.8% at substitute ratios of 20–27%. The CO2 emission level decreases with 20% for maximum hydrogen cyclic dose. In terms of pollutant emission level at hydrogen use the emission level of the NOx decreases with 50% and the smoke number decreases with 73.8% comparative to classic fuelling at the maximum hydrogen cyclic dose.

Conventional fuels for vehicular applications generate hazardous pollutants which have an adverse effect on the environment. Therefore there is a high demand to shift towards environment-friendly vehicles for the present mobility sector. This paper highlights sustainable mobility and specifically sustainable transportation as a solution to reduce GHG emissions. Thus hydrogen fuel-based vehicular technologies have started blooming and have gained significance following the zero-emission policy focusing on various types of sustainable motilities and their limitations. Serving an incredible deliverance of energy by hydrogen fuel combustion engines hydrogen can revolution various transportation sectors. In this study the aspects of hydrogen as a fuel for sustainable mobility sectors have been investigated. In order to reduce the GHG (Green House Gas) emission from fossil fuel vehicles researchers have paid their focus for research and development on hydrogen fuel vehicles and proton exchange fuel cells. Also its development and progress in all mobility sectors in various countries have been scrutinized to measure the feasibility of sustainable mobility as a future. This paper is an inclusive review of hydrogen-based mobility in various sectors of transportation in particular fuel cell cars that provides information on various technologies adapted with time to add more towards perfection. When compared to electric vehicles with a 200-mile range fuel cell cars have a lower driving cost in all of the 2035 and 2050 scenarios. To stimulate the use of hydrogen as a passenger automobile fuel the cost of a hydrogen fuel cell vehicle (FCV) must be brought down to at least the same level as an electric vehicle. Compared to gasoline cars fuel cell vehicles use 43% less energy and generate 40% less CO2.

This study presents a novel design and development of a 280000 m3 liquefied hydrogen tanker ship by implementing a set of 6 Flettner rotors as an assistance propulsion system in conjunction with a combined-cycle gas turbine fuelled by hydrogen as a prime mover. The study includes assessment of the technical and environmental aspects of the developed design. Furthermore an established method was applied to simulate the LH2 tanker in different voyages and conditions to investigate the benefits of harnessing wind energy to assist combined-cycle gas turbine in terms of performance and emission reduction based on engine behaviour for different voyages under loaded and unloaded normal as well as 6 % degraded engine and varying ambient conditions. The results indicate that implementing a set of 6 Flettner rotors for the LH2 tanker ship has the potential to positively impact the performance and lead to environmental benefits. A maximum contribution power of around 1.8 MW was achieved in the winter season owing to high wind speed and favourable wind direction. This power could save approximately 3.6 % of the combined-cycle gas turbine total output power (50 MW) and cause a 3.5 % reduction in NOx emissions.

Combustion of hybrid natural gas (methane) and hydrogen mixture in domestic swirl stoves has been characterized using hot-state experiments and numerical analysis. The detailed combustion mechanism of methane and hydrogen (GRI-Mech 3.0) has been simplified to obtain reduced number of chemical reactions involved (82 % reduction). The novel simplified combustion mechanism developed has been used to obtain combustion characteristics of hybrid methane-hydrogen mixture. The difference between the calculations from the detailed and the simplified mechanisms has been found to be Combustion of hybrid natural gas (methane) and hydrogen mixture in domestic swirl stoves has been characterized using hot-state experiments and numerical analysis. The detailed combustion mechanism of methane and hydrogen (GRI-Mech 3.0) has been simplified to obtain reduced number of chemical reactions involved (82 % reduction). The novel simplified combustion mechanism developed has been used to obtain combustion characteristics of hybrid methane-hydrogen mixture. The difference between the calculations from the detailed and the simplified mechanisms has been found to be <1 %. A numerical model based on the simplified combustion model is developed rigorously tested and validated against hot-state tests. The results depict that the maximum difference in combustion zone’s average temperature is <13 %. The investigations have then been extended to hybrid methane-hydrogen mixtures with varying volume fraction of hydrogen. The results show that for a mixture containing 15 % hydrogen the release of CO due to combustion reduces by 25 % while the combustion zone’s average temperature reduces by 6.7 %. The numerical results and hot-state tests both confirm that the temperature remains stable when hybrid methane-hydrogen mixture is used in domestic swirl gas stoves demonstrating its effectiveness in cooking processes.

In order to reduce the emission of carbon dioxide gas turbine power station will expect to use more clean fuels in the future especially those like hydrogen. Hydrogen-rich fuel(syngas) combustion characteristics of the novel counter dual-swirl gas turbine combustor under fixed calorific value input were studied by experiment and numerical simulation. PIV and temperature rake were used respectively to obtain the velocity and temperature distribution in the combustion chamber. The turbulence model of Reynolds stress and the kinetic model of detailed chemical syngas combustion were used simultaneously in the computational simulations. Based on the obtained results it was found that there is a reasonable agreement between the numerical results and the experimental data. The analysis shows that the flow field and temperature field of the combustor were almost unaffected by the change of hydrogen content and shows a nearly identical distribution structure under all conditions with hydrogen content below 90%; but when the H2 content reaches 90% the above characteristic plots were significantly changed. As the H2 content in the fuel increases on the center line of the combustor the jet velocity of the fuel decreased the temperature of the gas flow increased the recovery coefficient of total pressure decreased and the temperature distribution at the combustor outlet became more uniform. In addition it is also found that the syngas turbine with the same output power consumed less fuel than the gas turbine with hydrocarbon fuel. This paper provides reference for the study of hydrogen-rich syngas turbine and the application of hydrogen-rich fuel in combustor of energy system.

A novel carbon capture and utilization (CCU) process is described in which process-related carbon dioxide is captured from cement plant exhaust gas (10000 tons/year) and converted with green hydrogen in a Fischer Tropsch synthesis to liquid mainly paraffinic hydrocarbons (syncrude approx. 3000 tons/year) which is finally processed to polyolefins. This CCU process chain is simulated with the software package ASPEN Plus V12.1®. In a first step the influence of hydrogen production technology such as PEM and SOEC and reverse water-gas shift reactor (rWGS) technology (electrified and autothermal design) on plant specific efficiencies (Power-to-Liquid PtL carbon conversion) product volumes and investment operating and net production costs (NPC) is investigated. Furthermore process routes reducing the CO2 content in the Fischer Tropsch feed gas are elaborated implementing a CO2 separation unit or recycle streams back to the rWGS reactor. Unexpectedly CO2 capture and recycle streams back to the rWGS show no significant impact on the performance of each process scenario particularly in terms of the product quantity. However lower PtL efficiencies and higher NPC are noticeable for these cases. The techno-economic assessment reveals that the use of a SOEC and an electrified rWGS reactor offers the technologically best and economically most optimized process chain with NPC of 8.40 EUR/kgsyncrude a PtL efficiency of 54% and a carbon conversion of 85%.

The negative consequences of toxic emissions from internal combustion engines energy security climate change and energy costs have led to a growing demand for clean power sources in the automotive industry. The development of eco-friendly vehicle technologies such as electric and hydrogen vehicles has increased. This article investigates whether hydrogen vehicles will replace electric vehicles in the future. The results showed that fuel-cell cars are unlikely to compete with electric cars. This is due to the advancements in electric vehicles and charging infrastructure which are becoming more cost-effective and efficient. Additionally the technical progress in battery electric vehicles (BEVs) is expected to reduce the market share of fuel-cell electric vehicles (FCEVs) in passenger vehicles. However significant investments have been made in hydrogen cars. Many ongoing investments seem to follow the sunk cost fallacy where decision-makers continue to invest in an unprofitable project due to their already invested resources. Furthermore even with megawatt charging fuel-cell trucks cost more than battery-powered electric trucks. The use cases for fuel-cell electric trucks are also much more limited as their running expenses are higher compared to electric cars. Hydrogen vehicles may be beneficial for heavy transport in remote areas. However it remains to be seen if niche markets are large enough to support fuel-cell electric truck commercialization and economies of scale. In summary we believe that hydrogen vehicles will not replace electric cars and trucks at least before 2050.

Issues related to the reduction of the environmental impact of means of road transport by the use of electric motors powered by Proton Exchange Membrane (PEM) fuel cells are presented in this article. The overall functional characteristics of electric vehicles are presented as well as the essence of the operation of a fuel cell. On the basis of analyzing the energy conversion process significant advantages of electric drive are demonstrated especially in vehicles for urban and suburban applications. Moreover the analyzed literature indicated problems of controlling and maintaining fuel cell power caused by its highest dynamic and possible efficiency. This control was related to the variable load conditions of the fuel cell vehicle (FCV) engine. The relationship with the conventional dependencies in the field of vehicle dynamics is demonstrated. The final part of the study is related to the historical outline and examples of already operating fuel cell systems using hydrogen as an energy source for energy conversion to power propulsion vehicle’s engines. In conclusion the necessity to conduct research in the field of methods for controlling the power of fuel cells that enable their effective adaptation to the temporary load resulting from the conditions of vehicle motion is indicated.

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.

Hydrogen is seen as a future energy carrier since its chemical compounds make up a large part of the Earth’s surface. This study sought to analyze the impact related to the inclusion of hydrogen and oxygen gases produced on demand by an alkaline electrolyzer to the engine added directly through the fuel intake line. For this purpose performance parameters were monitored such as liquid fuel consumption and greenhouse gas emissions and correlated to any effect observed on the engine’s power output and combustion behavior. A 58 kVA nominal power motor-generator was used coupled with a resistive load bank (20 kW) where two fuel configurations were tested (diesel injection only and a mixture of diesel hydrogen and oxygen) and compared. A total of 42 tests were performed considering both the admission gases into the fuel intake line and also diesel supply only for baseline. A substantial decrease in fuel consumption was observed (7.59%) when the blend configuration was used despite a decrease in the engine’s work (1.07%). It was also possible to see a common pattern between NO and NO2 emissions for both fuel configurations while the behavior of the CO2 and CO emissions indicated a higher complete diesel burning fraction when using the gases on demand. Therefore we can verify that the use of hydrogen and oxygen gases produced on demand in the fuel intake line is a promising alternative to provide a decrease in liquid fuel consumption and an overall improvement in engine combustion.

Fuel transition can decarbonize shipping and help meet IMO 2050 goals. In this paper HFO with CCS LNG with CCS bio-methanol biodiesel hydrogen ammonia and electricity were studied using empirical ship design models from a fleet-level perspective and at the Tank-ToWake level to assist operators technology developers and policy makers. The cargo attainment rate CAR (i.e. cargo that must be displaced due to the low-C propulsion system) the ES (i.e. TTW energy needed per ton*n.m.) the CS (economic cost per ton*n.m.) and the carbon intensity index CII (gCO2 per ton*n.m.) were calculated so that the potential of the various alternatives can be compared quantitatively as a function of different criteria. The sensitivity of CAR towards ship type fuel type cargo type and voyage distance were investigated. All ship types had similar CAR estimates which implies that considerations concerning fuel transition apply equally to all ships (cargo containership tankers). Cargo type was the most sensitive factor that made a ship either weight or volume critical indirectly impacting on the CAR of different fuels; for example a hydrogen ship is weight-critical and has 2.3% higher CAR than the reference HFO ship at 20000 nm. Voyage distance and fuel type could result in up to 48.51% and 11.75% of CAR reduction. In addition to CAR the ES CS and CII for a typical mission were calculated and it was found that HFO and LNG with CCS gave about 20% higher ES and CS than HFO and biodiesel had twice the cost while ammonia methanol and hydrogen had 3–4 times the CS of HFO and electricity about 20 times suggesting that decarbonisation of the world’s fleet will come at a large cost. As an example of including all factors in an effort to create a normalized scoring system an equal weight was allocated to each index (CAR ES CS and CII). Biodiesel achieved the highest score (80%) and was identified as the alternative with the highest potential for a deep-seagoing containership followed by ammonia hydrogen bio-methanol and CCS. Electricity has the lowest normalized score of 33%. A total of 100% CAR is achievable by all alternative fuels but with compromises in voyage distance or with refuelling. For example a battery containership carrying an equal amount of cargo as an HFO-fuelled containership can only complete 13% of the voyage distance or needs refuelling seven times to complete 10000 n.m. The results can guide decarbonization strategies at the fleet level and can help optimise emissions as a function of specific missions.

Nowadays we face a series of global challenges including the growing depletion of fossil energy environmental pollution and global warming. The replacement of coal petroleum and natural gas by secondary energy resources is vital for sustainable development. Hydrogen (H2 ) energy is considered the ultimate energy in the 21st century because of its diverse sources cleanliness low carbon emission flexibility and high efficiency. H2 fuel cell vehicles are commonly the end-point application of H2 energy. Owing to their zero carbon emission they are gradually replacing traditional vehicles powered by fossil fuel. As the H2 fuel cell vehicle industry rapidly develops H2 fuel supply especially H2 quality attracts increasing attention. Compared with H2 for industrial use the H2 purity requirements for fuel cells are not high. Still the impurity content is strictly controlled since even a low amount of some impurities may irreversibly damage fuel cells’ performance and running life. This paper reviews different versions of current standards concerning H2 for fuel cell vehicles in China and abroad. Furthermore we analyze the causes and developing trends for the changes in these standards in detail. On the other hand according to characteristics of H2 for fuel cell vehicles standard H2 purification technologies such as pressure swing adsorption (PSA) membrane separation and metal hydride separation were analyzed and the latest research progress was reviewed.

The state of environmental pollution brought about as a result of the modern civilization has been monitored in the interests of the environment and human health since the seventies of the last century. Ensuring the energy security is one of the most basic existential requirements for a functional civilized society. The growing civilizational needs caused by broadly understood development generate demand for the production of all kinds of goods in all sectors of the economy as well as world-wide information transfer. The current energy demand is mostly covered using fossil fuels such as coal oil and natural gas. Some of the energy demand is covered by the energy generated in nuclear reactions and a small part of it comes from renewable energy sources. Energy derived from fossil fuels is inevitably associated with fuel oxidation processes. These processes in addition to generating heat are responsible for the emission of harmful compounds to the atmosphere: carbon monoxide carbon dioxide nitrogen oxides hydrocarbons and particulate matter. These pollutants pose a serious threat to the people as well as the environment in which they live. Due to the large share of fossil fuel energy generation in the process of combustion it becomes necessary to seek other means of obtaining the so-called "clean energy". Fuel cells may have a very high potential in this respect. Their development has enabled attempts to use them in all modes of transport. An important factor in the development of fuel cells is their relatively high efficiency and the coinciding strictening of the emission norms from internal combustion engines used to power maritime transport. Therefore the aim of this article has been to assess the potential of fuel cells as a main source of propulsion power source. A review of the designs of fuel cell systems and their use was performed. The article summarizes the assessment of the potential role of fuel cells as a power source of maritime transport.

Currently transitioning from fossil fuels to renewable sources of energy is needed considering the impact of climate change on the globe. From this point of view there is a need for development in several stages such as storage transmission and conversion of power. In this paper we demonstrate a simulation of a hybrid energy storage system consisting of a battery and fuel cell in parallel operation. The novelty in the proposed system is the inclusion of an electrolyser along with a switching algorithm. The electrolyser consumes electricity to intrinsically produce hydrogen and store it in a tank. This implies that the system consumes electricity as input energy as opposed to hydrogen being the input fuel. The hydrogen produced by the electrolyser and stored in the tank is later utilised by the fuel cell to produce electricity to power the load when needed. Energy is therefore stored in the form of hydrogen. A battery of lower capacity is coupled with the fuel cell to handle transient loads. A parallel control algorithm is developed to switch on/off the charging and discharging cycle of the fuel cell and battery depending upon the connected load. Electrically equivalent circuits of a polymer electrolyte membrane electrolyser polymer electrolyte membrane fuel cell necessary hydrogen oxygen water tanks and switching controller for the parallel operation were modelled with their respective mathematical equations in MATLAB® Simulink®. In this paper we mainly focus on the modelling and simulation of the proposed system. The results showcase the simulated system’s mentioned advantages and compare its ability to handle loads to a battery-only system.

Split hydrogen direct injection (SHDI) has been proved capable of better efficiency and fewer emissions. Therefore to investigate SHDI deeply a numerical study on the effect of second injection timing was presented at a gasoline/hydrogen spark ignition (SI) engine with SHDI. With an excess air ratio of 1.5 five different second injection timings achieved five kinds of hydrogen mixture distribution (HMD) which was the main factor affecting the engine performances. With SHDI since the HMD is manageable the engine can achieve better efficiency and fewer emissions. When the second injection timing was 105◦ crank angle (CA) before top dead center (BTDC) the Pmax was the highest and the position of the Pmax was the earliest. Compared with the single hydrogen direct injection (HDI) the NOX CO and HC emissions with SHDI were reduced by 20% 40% and 72% respectively.

Appropriate climate change mitigation requires solutions for all actors of the energy system. The residential sector is a major part of the energy system and solutions for the implementation of a seasonal hydrogen storage system in residential houses has been increasingly discussed. A global analysis of prosumer systems including seasonal hydrogen storage with water electrolyser hydrogen compressor storage tank and a fuel cell studying the role of such a seasonal household storage in the upcoming decades is not available. This study aims to close this research gap via the improved LUT-PROSUME model which models a fully micro sector coupled residential photovoltaic prosumer system with linear optimisation for 145 regions globally. The modelling of the cost development of hydrogen storage components allows for the simulation of a residential system from 2020 until 2050 in 5-year steps in hourly resolution. The systems are cost-optimised for either on– or off-grid operation in eight scenarios including battery electric vehicles which can act as an additional vehicle-to-home electricity storage for the system. Results show that implementation of seasonal hydrogen systems only occurs in least cost solutions in high latitude countries when the system is forced to run in off-grid mode. In general a solar photovoltaic plus battery system including technologies that can cover the heat demand is the most economic choice and can even achieve lower cost than a full grid supply in off-grid operation for most regions until 2050. Additional parameters including the self-consumption ratio the demand cover ratio and the heat cover ratio can therefore not be improved by seasonal storage systems if economics is the main deciding factor for a respective system. Further research opportunities and possible limitations of the system are then identified.

In the modern world zero-carbon society has become a new buzzword of the era. Many projects have been initiated to develop alternatives not only to the environmental crisis but also to the shortage of fossil fuels. With successful projects in automobile technology hydrogen fuel is now being tested and utilized as a sustainable green fuel in the aviation sector which will lead to zero carbon emission in the future. From the mid-20th century to the early 21st numerous countries and companies have funded multimillion projects to develop hydrogen-fueled aircraft. Empirical data show positive results for various projects. Consequently large companies are investing in various innovations undertaken by researchers under their supervision. Over time the efficiency of hydrogen-fueled aircraft has improved but the lack of refueling stations large production cost and consolidated carbon market share have impeded the path of hydrogen fuel being commercialized. In addition the Unmanned Aerial Vehicle (UAV) is another important element of the Aviation industry Hydrogen started to be commonly used as an alternative fuel for heavy-duty drones using fuel cell technology. The purpose of this paper is to provide an overview of the chronological development of hydrogen-powered aircraft technology and potential aviation applications for hydrogen and fuel cell technology. Furthermore the major barriers to widespread adoption of hydrogen technology in aviation are identified as are future research opportunities.

The electrification of heavy-duty trucks stands as a critical and challenging cornerstone in the low-carbon transition of the transportation sector. This paper employs the total cost of ownership (TCO) as the economic evaluation metric framed within the context of China’s ambitious goals for heavy truck electrification by 2035. A detailed TCO model is developed encompassing not only the vehicles but also their related energy replenishing infrastructures. This comprehensive approach enables a sophisticated examination of the economic feasibility for different deployment contexts of both fuel cell and battery electric heavy-duty trucks emphasizing renewable energy utilization. This study demonstrates that in the context where both fuel cell components and hydrogen energy are costly fuel cell trucks (FCTs) exhibit a significantly higher TCO compared to battery electric trucks (BETs). Specifically for a 16 ton truck with a 500 km range the TCO for the FCT is 0.034 USD/tkm representing a 122% increase over its BET counterpart. In the case of a 49 ton truck designed for a 1000 km range the TCO for the FCT is 0.024 USD/tkm marking a 36% premium compared to the BET model. The technological roadmap suggests a narrowing cost disparity between FCTs and BETs by 2035. For the aforementioned 16 ton truck model the projected TCO for the FCT is expected to be 0.016 USD/tkm which is 58% above the BET and for the 49 ton variant it is anticipated at 0.012 USD per ton-kilometer narrowing the difference to just 4.5% relative to BET. Further analysis within this study on the influences of renewable energy pricing and operational range on FCT and BET costs highlights a pivotal finding: for the 49 ton truck achieving TCO parity between FCTs and BETs is feasible when renewable energy electricity prices fall to 0.022 USD/kWh or when the operational range extends to 1890 km. This underscores the critical role of energy costs and efficiency in bridging the cost gap between FCTs and BETs.

System durability is crucial for the successful commercialization of polymer electrolyte fuel cells (PEFCs) in fuel cell electric vehicles (FCEVs). Besides conventional electrochemical cycling durability during long-term operation the effect of operation in cold climates must also be considered. Ice formation during start up in sub-zero conditions may result in damage to the electrocatalyst layer and the polymer electrolyte membrane (PEM). Here we conduct accelerated cold start cycling tests on prototype fuel cell stacks intended for incorporation into commercial FCEVs. The effect of this on the stack performance is evaluated the resulting mechanical damage is investigated and degradation mechanisms are proposed. Overall only a small voltage drop is observed after the durability tests only minor damage occurs in the electrocatalyst layer and no increase in gas crossover is observed. This indicates that these prototype fuel cell stacks successfully meet the cold start durability targets for automotive applications in FCEVs.

Hydrogen is an emerging technology changing the context of heating with cleaner combustion than traditional fossil fuels. Studies indicate the potential to repurpose the existing natural gas infrastructure offering consumers a sustainable economically viable option in the future. The integration of hydrogen in combined heat and power systems could provide residential energy demand and reduce environmental emissions. However the widespread adoption of hydrogen will face several challenges such as carbon dioxide emissions from the current production methods and the need for infrastructure modification for transport and safety. Researchers indicated the viability of hydrogen in decarbonizing heat while some studies also challenged its long-term role in the future of heating. In this paper a comprehensive literature review is carried out by identifying the following key aspects which could impact the conclusion on the overall role of hydrogen in heat decarbonization: (i) a holistic view of the energy system considering factors such as renewable integration and system balancing; (ii) consumer-oriented approaches often overlook the broader benefits of hydrogen in emission reduction and grid stability; (iii) carbon capture and storage scalability is a key factor for large-scale production of low-emission blue hydrogen; (iv) technological improvements could increase the cost-effectiveness of hydrogen; (v) the role of hydrogen in enhancing resilience especially during extreme weather conditions raises the potential of hydrogen as a flexible asset in the energy infrastructure for future energy supply; and finally when considering the UK as a basis case (vi) incorporating factors such as the extensive gas network and unique climate conditions necessitates specific strategies.

Proton Exchange Membrane Fuel Cells (PEMFCs) are seen as an alternative for heavy-duty transportation electrification. Powered by a green hydrogen source they can provide high efficiency and low carbon emissions compared to traditional fuels. However to be competitive these systems require high reliability when operated in real-life conditions as well as safe and efficient operating management. In order to achieve these goals the X-in-the-loop (also called model-based design) methodology is well suited. It has been largely adopted for PEMFC system development and optimisation as they are complex multi-component systems. In this paper a systematic analysis of the scientific literature is conducted to review the methodology implementation for the design and improvement of the PEMFC systems. It exposes a precise definition of each development step in the methodology. The analysis shows that it can be employed in different ways depending on the subsystems considered and the objectives sought. Finally gaps in the literature and technical challenges for fuel cell systems that should be addressed are identified.

There is renewed interest in hydrogen as an alternative fuel for aero engines due to their perceived environmental and performance benefits compared to jet fuel. This paper presents a cycle thermal performance energy and creep life assessment of hydrogen compared with jet fuel using a turbofan aero engine. The turbofan cycle performance was simulated using a code developed by the authors that allows hydrogen and jet fuel to be selected as fuel input. The exergy assessment uses both conservations of energy and mass and the second law of thermodynamics to understand the impact of the fuels on the exergy destruction exergy efficiency waste factor ratio environmental effect factor and sustainability index for a turbofan aero engine. Finally the study looks at a top-level creep life assessment on the high-pressure turbine hot section influenced by the fuel heating values. This study shows performance (64% reduced fuel flow rate better SFC) and more extended blade life (15% increase) benefits using liquefied hydrogen fuel which corresponds with other literary work on the benefits of LH2 over jet fuel. This paper also highlights some drawbacks of hydrogen fuel based on previous research work and gives recommendations for future work aimed at maturing the hydrogen fuel concept in aviation.

Decarbonisation of heavy haul rail is an essential contributor to a zero-emissions future. However the transition from diesel to battery locomotives is not always practical given the unique characteristics of each haul. This paper demonstrates the limitations of state-of-the-art batteries using real-world data from multiple locomotives operating in Australian rail freight. An energy model was developed to assess each route’s required energy and potential regenerated energy. The tractive and regenerative battery energy mass and cost were determined using data from the energy model coupled with battery specifications. The feasibility of implementing lithium iron phosphate (LFP) nickel manganese cobalt (NMC) and lithium titanium oxide (LTO) chemistries was explored based on cost energy density cycle lifespan and locomotive data. LFP was identified as the most suitable current battery solution based on current chemistries. Further examination of the energy demands and associated mass/volume constraints concluded that three platforms are required for heavy haul rail decarbonisation i) a battery electric locomotive for low-energy demands which can be coupled with either ii) a battery electric tender for medium energy demands or iii) a hydrogen fuel cell electric tender for higher energy demands. A future-looking techno-economic assessment of battery and hydrogen fuel cell platforms concludes that the lowest cost solution for low-energy hauls is a battery-only system and for high-energy hauls a battery-hydrogen system.

Green liquid hydrogen (LH2) could play an essential role as a zero-carbon aircraft fuel to reach long-term sustainable aviation. Excluding challenges such as electrolysis transportation and use of renewable energy in setting up hydrogen (H2) fuel infrastructure this paper investigates the interface between refueling systems and aircraft and the impacts on fuel distribution at the airport. Furthermore it provides an overview of key technology design decisions for LH2 refueling procedures and their effects on the turnaround times as well as on aircraft design. Based on a comparison to Jet A-1 refueling new LH2 refueling procedures are described and evaluated. Process steps under consideration are connecting/disconnecting purging chill-down and refueling. The actual refueling flow of LH2 is limited to a simplified Reynolds term of v · d = 2.35 m2/s. A mass flow rate of 20 kg/s is reached with an inner hose diameter of 152.4 mm. The previous and subsequent processes (without refueling) require 9 min with purging and 6 min without purging. For the assessment of impacts on LH2 aircraft operation process changes on the level of ground support equipment are compared to current procedures with Jet A-1. The technical challenges at the airport for refueling trucks as well as pipeline systems and dispensers are presented. In addition to the technological solutions explosion protection as applicable safety regulations are analyzed and the overall refueling process is validated. The thermodynamic properties of LH2 as a real compressible fluid are considered to derive implications for airport-side infrastructure. The advantages and disadvantages of a subcooled liquid are evaluated and cost impacts are elaborated. Behind the airport storage tank LH2 must be cooled to at least 19 K to prevent two-phase phenomena and a mass flow reduction during distribution. Implications on LH2 aircraft design are investigated by understanding the thermodynamic properties including calculation methods for the aircraft tank volume and problems such as cavitation and two-phase flows. In conclusion the work presented shows that LH2 refueling procedure is feasible compliant with the applicable explosion protection standards and hence does not impact the turnaround procedure. A turnaround time comparison shows that refueling with LH2 in most cases takes less time than with Jet A-1. The turnaround at the airport can be performed by a fuel truck or a pipeline dispenser system without generating direct losses i.e. venting to the atmosphere.

The production storage and use of hydrogen for energy purposes will become increasingly important during the energy transition. One way to use hydrogen is to apply it to power vehicles. This green technological solution affects low-emissions transport which is beneficial and important especially in cities. The authors of this article analyzed the use of hydrogen production infrastructure for bus propulsion in the city of Katowice (Poland). The methods used in the study included a greedy algorithm and cost methods which were applied for the selection of vehicles and identification of the infrastructure for the production storage and refueling of hydrogen as well as to conduct the economic analysis during this term. The article presented the complexity of the techno-economic analysis of the infrastructure and its installation. The key element was the selection of the number of vehicles to the hydrogen production possibilities of an electrolyser and capabilities of the storage and charging infrastructure.

Power-to-X technologies that convert renewable electricity to chemically stored energy in “X” may provide a gaseous liquid or solid fuel that can be used in winter to provide both heat and electricity and thus replace fossil fuels that are currently used in many countries with cold winters. This contribution compares two options for power-to-X technologies for providing heat and electricity supply of buildings with high solar photovoltaic coverage at times of low solar availability. The option “compressed hydrogen” is based on water electrolysis that produces hydrogen on-site. This hydrogen is subsequently compressed and stored at high pressure (350 bar) for use in winter by a fuel cell. The option “aluminium redox-cycle” includes an inert electrode high temperature electrolysis process that is carried out at industrial scale. Produced aluminium is subseqeuntly transported to the site of use and converted to hydrogen and heat – and finally to electricity and heat - by aluminium-water reaction in combination with a fuel cell. Results of cost and LCA analysis show that the overall energetic efficiency of the compressed hydrogen process is slightly higher than for the aluminium redox cycle. However the aluminium redox-cycles needs far less on-site storage volume and is likely to become available at lower investment cost for the end user. Total annual cost of ownership and global warming potential of the two options are quite similar.