Publications

This paper investigates the economic competitiveness of hydrogen-powered trucks. It reviews the growing number of papers that provide an estimate of the total cost of ownership (TCO) of hydrogen-powered trucks relative to their diesel equivalents. It examines the methodology applied the variables considered the data used for estimation and the results obtained. All reviewed studies conclude that hydrogen-powered trucks are not currently cost-competitive while they might become competitive after 2030. The conclusion holds across truck types and sizes hydrogen pathways mission profiles and countries. However we find that there is still a huge area of uncertainty regarding the purchase price of hydrogen-powered trucks and the cost of hydrogen which hampers the reliability of the results obtained. Various areas of methodological improvements are suggested.

Blending hydrogen into natural gas and using existing natural gas infrastructure provides energy storage greenhouse gas emission reduction from combustion and other benefits as the world transitions to a hydrogen economy. Though this seems to be a simple and attractive technique there is a dearth of existing safety codes and standards and understanding the safety implications is warranted before implementation. In this paper we present some preliminary findings on the dispersion characteristics of hydrogen-methane blends performed under controlled conditions inside a laboratory. Experiments were performed at two different upstream pressures of 5 and 10 bar as the blends dispersed into air through a 1 mm diameter orifice. Blends of 25 50 and 75 vol-% hydrogen in methane were tested. Spatially resolved Raman signals from hydrogen methane and nitrogen were acquired simultaneously at 10 Hz using separate ICCD cameras from which the individual concentrations and jet boundaries could be determined. Finally a comparison between dispersion characteristics of blended fuel jets with pure hydrogen and pure methane jets was made.

The unsustainable and continuous growth of anthropogenic emissions of greenhouse gases (GHG) has pushed governments private companies and stakeholders to adopt measures and policies to fight against climate change. Within this framework increasing the contribution of renewable energy sources (RES) to final consumed energy plays a key role in the planned energy transition. Regarding the residential sector in Europe 92% of GHG emissions comes from 75% of the building stock that is over 25 years old and highly inefficient. Thus this sector must raise RES penetration from the current 36% to 77% by 2050 to comply with emissions targets. In this regard the hybridization of hydrogen-based technologies and RES represents a reliable and versatile solution to facilitate decarbonization of the residential sector. This study provides an overview and analysis of standalone renewable hydrogen-based systems (RHS) focusing on the residential and buildings sector as well as critical infrastructures like telecom stations data servers etc. For detailed evaluation of RHS several pilot plants and real demonstration plants implemented worldwide are reviewed. To this end a techno-economic assessment of relevant parameters like self-sufficiency ratio levelized cost of energy and hydrogen roundtrip efficiency is provided. Moreover the performance of the different configurations is evaluated by comparing the installed power of each component and their energy contribution to cover the load over a defined period of time. Challenges ahead are identified for the wider deployment of RHS in the residential and buildings sector.

The article reviews gas turbine combustion technologies focusing on their current ability to operate with hydrogen enriched natural gas up to 100% H2. The aim is to provide a picture of the most promising fuel-flexible and clean combustion technologies the object of current research and development. The use of hydrogen in the gas turbine power generation sector is initially motivated highlighting both its decarbonisation and electric grid stability objectives; moreover the state-of-the-art of hydrogen-blend gas turbines and their 2024 and 2030 targets are reported in terms of some key performance indicators. Then the changes in combustion characteristics due to the hydrogen enrichment of natural gas blends are briefly described from their enhanced reactivity to their pollutant emissions. Finally gas turbine combustion strategies both already commercially available (mostly based on aerodynamic flame stabilisation self-ignition and staging) or still under development (like the micro-mixing and the exhaust gas recirculation concepts) are described.

This paper studies fast fueling of gaseous hydrogen into large hydrogen (H2) tanks suitable for maritime applications. Three modeling methods have been developed and evaluated: (1) Two-dimensional computational fluid dynamic (CFD) modeling (2) One-dimensional wall discretized modeling and (3) Zero-dimensional modeling. A detailed 2D CFD simulation of a small H2-tank was performed and validated with data from literature and then used to simulate a large H2-tank. Results from the 2D-model show non-uniform temperature distribution inside the large tank but not in the small H2-tank. The 1D-model can predict the mean temperature in small H2-tanks but not the inhomogeneous temperature field in large H2-tanks. The 0D-model is suitable as a screening tool to obtain rough estimates. Results from the modeling of the large H2-tank show that the heat transfer to the wall during fast filling is inhibited by heat conduction in the wall which leads to an unacceptably high mean hydrogen temperature.

This study proposes a multitype electrolytic collaborative hydrogen production model for optimizing the capacity configuration of renewable energy off grid hydrogen production systems. The electrolytic hydrogen production process utilizes the synergistic electrolysis of an alkaline electrolyzer (AEL) and proton exchange membrane electrolyzer (PEMEL) fully leveraging the advantages of the low cost of the AEL and strong regulation characteristics of the PEMEL. For the convenience of the optimization solution the article constructs a mixed linear optimization model that considers the constraints during system operation with the objective function of minimizing total costs while meeting industrial production requirements. Gurobi is used for the optimal solution to obtain the optimal configuration of a renewable energy off grid hydrogen production system. By comparing and analyzing the optimal configuration under conventional load and high-load conditions it is concluded that collaborative electrolysis has advantages in improving resource consumption and reducing hydrogen production costs. This is of great significance for optimizing the capacity configuration of off grid hydrogen production systems and improving the overall economic benefits of the system.

The UK government’s plans to decarbonise residential heating will mean major changes to the energy system whatever the specific technology pathway chosen driving a range of impacts on users and suppliers. We use an energy system model (UK TIMES) to identify the potential energy system impacts of alternative pathways to low or zero carbon heating. We find that the speed of transitioning can affect the network investment requirements the overall energy use and emissions generated while the primary heating fuel shift will determine which sectors and networks require most investment. Crucially we identify that retail price differences between heating fuels in the UK particularly gas and electricity could erode or eliminate bill savings from switching to more efficient heating systems.

This paper investigates the untapped potential of the Permian Basin a multifaceted energy axis in Texas and adjoining states in the emerging era of decarbonization. Aligned with current policy directives on regional hydrogen hubs this study explores the viability of developing a hydrogen energy hub in the Permian Basin thereby producing low-carbon intensity hydrogen from natural gas in the Basin and transporting it to the Greater Houston area. Diverging from existing literature this study provides an integrated techno-economic evaluation of the entire hydrogen value chain in the Permian Basin encompassing production storage and transportation. Furthermore it comparatively analyzes the scenario of interest against an optimized base scenario thereby underlining comparative advantages and disadvantages. The paper concludes that the delivered cost of Permian based low-carbon intensity hydrogen to the Greater Houston area is $1.85/kg benchmarked to the scenario with hydrogen produced close to the Greater Houston area and delivered at $1.42/kg. Our findings reveal that Permian-based low-carbon intensity hydrogen production can achieve cost savings in feedstock ($0.25/kg) and potentially accrue a higher production tax credit due to a shorter gas supply chain to production ($0.33/kg). Nevertheless a significant cost barrier is the expense of long-haul pipeline transport ($0.90/kg) from the Permian Basin to Houston as opposed to local production. Despite the obstacles the study identifies a potential breakeven solution where increasing the production scale to at least 412000 metric ton per year (about 3 steam reforming plants) in the Permian Basin can effectively lower costs in the transport sector. Hence a scaled-up production can mitigate the cost difference and establish the Permian Basin as a competitive player in the hydrogen market. In conclusion a SWOT analysis presents Strengths Weaknesses Opportunities and Threats associated with Permian-based hydrogen production.

Growth in Australia’s demand for engineers is fast outpacing supply. A significant challenge for Australia to achieve high projected low emissions hydrogen export targets by 2030 will be finding engineers with suitable knowledge skills and attributes to deliver hydrogen engineering projects safely and sustainably. This systematic review investigates educational outcomes needed to develop a hydrogen engineering workforce. Sixteen relevant studies published between 2003 and 2023 were identified to explore “What key knowledge skills and attributes support the development of a hydrogen engineering workforce?”. While these studies advocated the need for training and prescribed areas of required knowledge for the low-emissions hydrogen sector there was limited empirical evidence that informed what knowledge skills and attributes are relevant for entry to practice. This finding represents a significant opportunity for researchers to engage with employers and engineering practitioners within emerging low-emissions hydrogen sector capture empirical evidence and inform the design of educational programs.

Hydrogen is deemed as a crucial component in the transition to a carbon-free energy system and researchers are actively working to realize the hydrogen economy. While hydrogen derived from renewable energy sources is a promising means of providing clean energy to households and industries its practical usage is currently hindered by difficulties in transportation and storage. Due to the extreme operating conditions required for liquefying hydrogen various hydrogen carriers are being considered which can be transported and stored at mild operating conditions and provide hydrogen at the site of usage. Among various candidates green hydrogen carriers obtained via carbon dioxide utilization have been proposed as an economically and environmentally feasible option. Herein the potential of using methanol and formic acid as green hydrogen carriers are evaluated regarding various production and dehydrogenation pathways within a hydrogen distribution system including the recycle of carbon dioxide. Recent progress in carbon dioxide utilization processes especially conversion of carbon dioxide captured in amine solutions have demonstrated promising results for methanol and formic acid production. This study analyzes seven scenarios that consider carbon dioxide utilization-based thermocatalytic and electrochemical methanol and formic acid production as well as different dehydrogenation pathways and compares them to the scenario of delivering liquefied hydrogen. The scenarios are thoroughly analyzed via techno-economic analysis and life cycle assessment methods. The results of the study indicate that methanol-based options are economically viable reducing the cost up to 43% compared to liquefied hydrogen delivery. As for formic acid only the electrochemical production method is profitable retaining 10% less cost compared to liquefied hydrogen delivery. In terms of environmental impact all of the scenarios show higher global warming impact values than liquefied hydrogen distribution. However results show that in an optimistic case where wind electricity is widely used electrochemical formic acid production is competitive with liquefied hydrogen distribution retaining 39% less global warming impact values. This is because high conversion can be achieved at mild operating conditions for the production and dehydrogenation reactions of formic acid reducing the input of utilities other than electricity. This study suggests that while methanol can be a shortterm solution for hydrogen distribution electrochemical formic acid production may be a viable long-term option.

Conventional transportation systems are facing many challenges related to reducing fuel consumption noise and pollutants to satisfy rising environmental and economic criteria. These requirements have prompted many researchers and manufacturers in the transportation sector to look for cleaner more efficient and more sustainable alternatives. Powertrains based on fuel cell systems could partially or completely replace their conventional counterparts used in all modes of transport starting from small ones such as scooters to large mechanisms such as commercial airplanes. Since hydrogen fuel cells (HFCs) emit only water and heat as byproducts and have higher energy conversion efficiency in comparison with other conventional systems it has become tempting for many scholars to explore their potential for resolving the environmental and economic concerns associated with the transportation sector. This paper thoroughly reviews the principles and applications of fuel cell systems for the main transportation schemes including scooters bicycles motorcycles cars buses trains and aerial vehicles. The review showed that fuel cells would soon become the powertrain of choice for most modes of transportation. For commercial long-rage airplanes however employing fuel cells will be limited due to the replacement of the axillary power unit (APU) in the foreseeable future. Using fuel cells to propel such large airplanes would necessitate redesigning the airplane structure to accommodate the required hydrogen tanks which could take a bit more time.

CO2 emissions have been identified as the main driver for climate change with devastating consequences for the global natural environment. The steel industry is responsible for ~7–11% of global CO2 emissions due to high fossil-fuel and energy consumption. The onus is therefore on industry to remedy the environmental damage caused and to decarbonise production. This desk research report explores the Bio Steel Cycle (BiSC) and proposes a seven-step-strategy to overcome the emission challenges within the iron and steel industry. The true levels of combined CO2 emissions from the blast-furnace and basic-oxygen-furnace operation at 4.61 t of CO2 emissions/t of steel produced are calculated in detail. The BiSC includes CO2 capture implementing renewable energy sources (solar wind green H2 ) and plantation for CO2 absorption and provision of biomass. The 7-step-implementation-strategy starts with replacing energy sources develops over process improvement and installation of flue gas carbon capture and concludes with utilising biogas-derived hydrogen as a product from anaerobic digestion of the grown agrifood in the cycle. In the past CO2 emissions have been seemingly underreported and underestimated in the heavy industries and implementing the BiSC using the provided seven-steps-strategy will potentially result in achieving net-zero CO2 emissions in steel manufacturing by 2030.

Due to the increase in electric energy consumption and the significant growth in the number of electric vehicles (EV) at the level of the distribution network new networks have started using new fuels such as hydrogen to improve environmental indicators and at the same time better efficiency from the excess capacity of renewable resources. In this article the services that can be provided by hydrogen refueling stations and charging electric vehicles in the optimal performance of microgrids have been investigated. The model proposed in this paper includes a two-stage stochastic framework for scheduling resources in microgrids especially hydrogen refueling stations and electric vehicle charging. In this model two main goals of cost minimization and greenhouse gas emissions are considered. In the proposed framework and in the first stage the service range of microgrids is determined precisely according to the electrical limitations of distribution systems in emergency situations. Then in the second stage the problem of energy management in each microgrid will be solved centrally. In this situation various indicators including the output energy of renewable sources smart charging of hydrogen and electric vehicle charging stations (EV/FCV) and flexible loads (FL) are evaluated. The final mathematical model is implemented as a multivariate integer multiple linear problem (MILP) using the GUROBI solver in GAMS software. The simulation results on the modified IEEE 118-Bus network show the positive effect of the presence of flexible loads and smart charging strategies by charging stations. Also the numerical derivation shows that the operating costs of the entire system can be reduced by 4.77% and the use of smart charging strategies can reduce greenhouse gas emissions by 49.13%.

Fossil fuels and materials on Earth are a finite resource and the disposal of waste into the air on land and into water has an impact on our environment on a global level. Using Switzerland as an example the energy demand and the technical challenges and the economic feasibility of a transition to an energy economy based entirely on renewable energy were analyzed. Three approaches for the complete substitution of fossil fuels with renewable energy from photovoltaics called energy systems (ES) were considered i.e. a purely electric system with battery storage (ELC) hydrogen (HYS) and synthetic hydrocarbons (HCR). ELC is the most energy efficient solution; however it requires seasonal electricity storage to meet year-round energy needs. Meeting this need through batteries has a significant capital cost and is not feasible at current rates of battery production and expanding pumped hydropower to the extent necessary will have a big impact on the environment. The HYS allows underground hydrogen storage to balance seasonal demand but requires building of a hydrogen infrastructure and applications working with hydrogen. Finally the HCR requires the largest photovoltaic (PV) field but the infrastructure and the applications already exist. The model for Switzerland can be applied to other countries adapting the solar irradiation the energy demand and the storage options.

Global transitions from carbon- to hydrogen-based economies are an essential component of curbing greenhouse gas emissions and climate change. This study provides an investigative review of the technological development trends within the overall hydrogen value chain in terms of production storage transportation and application with the aim of identifying patterns in the announcement and execution of hydrogen-based policies both domestically within Korea as well as internationally. The current status of technological trends was analyzed across the three areas of natural hydrogen carbon dioxide capture utilization and storage technology linked to blue hydrogen and green hydrogen production linked to renewable energy (e.g. water electrolysis). In Korea the establishment of underground hydrogen storage facilities is potentially highly advantageous for the storage of domestically produced and imported hydrogen providing the foundations for large-scale application as economic feasibility is the most important national factor for the provision of fuel cells. To realize a hydrogen economy pacing policy and technological development is essential in addition to establishing a roadmap for efficient policy support. In terms of technological development it is important to prioritize that which can connect the value chain all of which will ultimately play a major role in the transformation of human energy consumption.

The environment is seriously threatened by the rising energy demand and the use of conventional energy sources. Renewable energy sources including hydro solar and wind have been the focus of extensive research due to the proliferation of energy demands and technological advancement. Wind energy is mostly harvested in coastal areas and little work has been done on energy extraction from winds in a suburban environment. The fickle behavior of wind makes it a less attractive renewable energy source. However an energy storage method may be added to store harvested wind energy. The purpose of this study is to evaluate the feasibility of extracting wind energy in terms of hydrogen energy in a suburban environment incorporating artificial intelligence techniques. To this end a site was selected latitude 33.64◦ N longitude 72.98◦ N and elevation 500 m above mean sea level in proximity to hills. One year of wind data consisting of wind speed wind direction and wind gust was collected at 10 min intervals. Subsequently long short-term memory (LSTM) support vector regression (SVR) and linear regression models were trained on the empirically collected data to estimate daily hydrogen production. The results reveal that the overall prediction performance of LSTM was best compared to that of SVR and linear regression models. Furthermore we found that an average of 6.76 kg/day of hydrogen can be produced by a 1.5 MW wind turbine with the help of an artificial intelligence method (LSTM) that is well suited for time-series data to classify process and predict.

The Russian invasion of Ukraine has undeniably disrupted the EU's energy system and created a window of opportunity for an acceleration of the low-carbon energy transition in Europe. As the trading bloc's biggest gas supplier Norway faces the imminent threat of fast-depleting gas reserves and declining value for its exports. Norway is trying to beat the clock by aggressively exploring more petroleum therefore delaying its energy transition. In anticipation of the future drop in gas prices Norway is counting on blue hydrogen to valorise its gas resources before gradually shifting to green hydrogen export. Against this background this article seeks to understand how changes in the EU's energy landscape have affected the energy export sector and low-carbon hydrogen export developments in Norway from a multi-level perspective. Using the exploratory scenario approach the article assesses the implications of the different petroleum exploration outcomes on the development of the low-carbon hydrogen export market in Norway. The findings show that despite gas discoveries there is an urgent need for a phase-out plan for the Norwegian petroleum sector. For low-carbon hydrogen to play an important role in Norway's energy transition time is of the essence and action needs to be taken during this window of opportunity. An industrial sector and its value chain could take 25 years to transform which means that actions and policies for a full transformation pathway need to take place in Norway by 2025 to be ready for a climate-neutral Europe in 2050.

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.

Welcome to our Future Energy Scenarios. These scenarios which stimulate debate and help inform the decisions that will shape our energy future have never been more important – especially when you consider the extent to which the energy landscape is being transformed.

Hydrogen is an energy carrier with potential applications in decarbonizing difficult-to-electrify energy and industrial systems. The environmental profile of hydrogen varies substantially with its inputs. Water consumption is a particular issue of interest as decisions are made about capital and other investments that will affect the scale and scope of hydrogen use. This study focuses on electrolytic hydrogen due to its path to greenhouse gas neutrality and irreducible water demand (though other pathways might be more water intensive). Specifically it evaluates life cycle consumptive freshwater intensity of electrolytic hydrogen in the United States at volumes associated with 12 scenarios for a deeply decarbonized 2050 US energy system from two modeling efforts for which both electricity fuel mix and electrolytic hydrogen production were projected (America’s Zero Carbon Action Plan and Net Zero America) in addition to volumes for a stylized energy storage project (500 MW hydrogen-fired turbine). Freshwater requirements for hydrogen could be large. Under a central estimate for 2050 US electrolytic hydrogen production electrolytic freshwater demand for process and feedstock inputs alone (i.e. excluding water for electricity) would be about 7.5% of total 2014 US freshwater consumption for energy (1 billion cubic meters/year 109 m3 /y; [0.2% 15%] across scenarios for 2050 electrolytic hydrogen production of [0.3 18] exajoules EJ). Including water associated with production of input electricity doubles this central estimate to 15% (2 × 109 m3 /y; [1% 23%] across scenarios). Turbines using electrolytic hydrogen are estimated to be about as freshwater intensive as a coal or nuclear plant assuming decarbonized low-water electricity inputs. Although a decarbonized energy system is projected to require less water for resource capture and electricity conversion than the current fossil-dominated energy system additional conversion processes supporting decarbonization like electrolysis could offset water savings.

Recently with the large-scale integration of renewable energy sources into microgrid (µGs) power electronics distributed energy systems have gained popularity. However low inertia reduces system frequency stability and anti-disturbance capabilities exposing power quality to intermittency and uncertainty in photovoltaics or wind turbines. To ensure system stability the virtual inertia control (VIC) is presented. This paper proposes two solutions to overcome the low inertia problem and the surplus in capacities resulting from renewable energy sources. The first solution employs superconducting magnetic energy storage (SMES) which can be deemed as an efficient solution for damping the frequency oscillations. Therefore in this work SMES that is managed by a simple proportional-integral-derivative controller (PID) controller is utilized to overcome the low inertia. In the second solution the hydrogen storage system is employed to maintain the stability of the microgrid by storing surplus power generated by renewable energy sources (RESs). Power-to-Power is a method of storing excess renewable energy as chemical energy in the form of hydrogen. Hydrogen can be utilized locally or delivered to a consumption node. The proposed µG operation demonstrates that the integration of the photovoltaics (PVs) wind turbines (WTs) diesel engine generator (DEG) electrolyzer micro gas turbine (µGT) and SMES is adequate to fulfill the load requirements under transient operating circumstances such as a low and high PV output power as well as to adapt to sudden changes in the load demand. The effectiveness of the proposed schemes is confirmed using real irradiance data (Benban City Egypt) using a MATLAB/SIMULINK environment.

If a hydrogen economy is to become a reality along with efficient and decarbonized production and adequate transportation infrastructure deployment of suitable hydrogen storage facilities will be crucial. This is because due to various technical and economic reasons there is a serious possibility of an imbalance between hydrogen supply and demand. Hydrogen storage could also be pivotal in promoting renewable energy sources and facilitating the decarbonization process by providing long duration storage options which other forms of energy storage such as batteries with capacity limitations or pumped hydro with geographical limitations cannot meet. However hydrogen is not the easiest substance to store and handle. Under ambient conditions the extremely low volumetric energy density of hydrogen does not allow for its efficient and economic storage which means it needs to be compressed liquefied or converted into other substances that are easier to handle and store. Currently there are different hydrogen storage solutions at varying levels of technology market and commercial readiness with different applications depending on the circumstances. This paper evaluates the relative merits and techno-economic features of major types of hydrogen storage options: (i) pure hydrogen storage (ii) synthetic hydrocarbons (iii) chemical hydrides (iv) liquid organic hydrogen carriers (v) metal hydrides and (vi) porous materials. The paper also discusses the main barriers to investment in hydrogen storage and highlights key features of a viable business model in particular the policy and regulatory framework needed to address the primary risks to which potential hydrogen storage investors are exposed.

Interest in hydrogen-powered rail vehicles has gradually increased worldwide over recent decades due to the global pressure on reduction in greenhouse gas emissions technology availability and multiple options of power supply. In the past research and development have been primarily focusing on light rail and regional trains but the interest in hydrogen-powered freight and heavy haul trains is also growing. The review shows that some technical feasibility has been demonstrated from the research and experiments on proof-of-concept designs. Several rail vehicles powered by hydrogen either are currently operating or are the subject of experimental programmes. The paper identifies that fuel cell technology is well developed and has obvious application in providing electrical traction power while hydrogen combustion in traditional IC engines and gas turbines is not yet well developed. The need for on-board energy storage is discussed along with the benefits of energy management and control systems.

Hydrogen production through electrolysis from renewable sources is expected to play an important role to achieve the reduction targets of carbon dioxide emissions set for the next decades. Electrolysers can use the renewable energy surplus to produce green hydrogen and contribute to making the electrical grid more stable. Hydrogen can be used as medium-long term energy storage converted into other fuels or used as feedstock in industry thus contributing to decarbonise hard-to-abate-sectors. However due to the intermittent and variable nature of solar and wind power the direct coupling of electrolysers with renewables may lead to high production fluctuations and frequent shutdowns. As a consequence accelerated electrolyser degradation and safety issues related to low load operation may arise. In this study simulations of hydrogen production with an electrolyser fed by a PV system are performed in Matlab for a reference year. The effect of PV power fluctuations on the electrolyser operation and production is investigated. The impact of the electrolyser size for a fixed nominal power of the PV plant is also analysed from both energetic and economic points of view.

In the sustainability context the performance of energy-producing technologies using different energy sources needs to be scored and compared. The selective criterion of a higher level of useful energy to feed an ever-increasing demand of energy to satisfy a wide range of endo- and exosomatic human needs seems adequate. In fact surplus energy is able to cover energy services only after compensating for the energy expenses incurred to build and to run the technology itself. This paper proposes an energy sustainability analysis (ESA) methodology based on the internal and external energy use of a given technology considering the entire energy trajectory from energy sources to useful energy. ESA analysis is conducted at two levels: (i) short-term by the use of the energy sustainability index (ESI) which is the first step to establish whether the energy produced is able to cover the direct energy expenses needed to run the technology and (ii) long-term by which all the indirect energy-quotas are considered i.e. all the additional energy requirements of the technology including the energy amortization quota necessary for the replacement of the technology at the end of its operative life. The long-term level of analysis is conducted by the evaluation of two indicators: the energy return per unit of energy invested (EROI) over the operative life and the energy payback-time (EPT) as the minimum lapse at which all energy expenditures for the production of materials and their construction can be repaid to society. The ESA methodology has been applied to the case study of H2 production at small-scale (10–15 kWH2) comparing three different technologies: (i) steam-methane reforming (SMR) (ii) solar-powered water electrolysis (SPWE) and (iii) two-stage anaerobic digestion (TSAD) in order to score the technologies from an energy sustainability perspective.

The valorization of integrated steelworks process off-gases as feedstock for synthesizing methane and methanol is in line with European Green Deal challenges. However this target can be generally achieved only through process off-gases enrichment with hydrogen and use of cutting-edge syntheses reactors coupled to advanced control systems. These aspects are addressed in the RFCS project i3 upgrade and the central role of hydrogen was evident from the first stages of the project. First stationary scenario analyses showed that the required hydrogen amount is significant and existing renewable hydrogen production technologies are not ready to satisfy the demand in an economic perspective. The poor availability of low-cost green hydrogen as one of the main barriers for producing methane and methanol from process off-gases is further highlighted in the application of an ad-hoc developed dispatch controller for managing hydrogen intensified syntheses in integrated steelworks. The dispatch controller considers both economic and environmental impacts in the cost function and although significant environmental benefits are obtainable by exploiting process off-gases in the syntheses the current hydrogen costs highly affect the dispatch controller decisions. This underlines the need for big scale green hydrogen production processes and dedicated green markets for hydrogen-intensive industries which would ensure easy access to this fundamental gas paving the way for a C-lean and more sustainable steel production.

Hydrogen eliminates carbon emissions from compression ignition (CI) engines while noble gases eliminate nitrogen oxide (NOx) emissions by replacing nitrogen. Noble gases can increase the in-cylinder temperature during the compression stroke due to their high specific heat ratio. This paper aims to find the optimum parameters for hydrogen combustion in an argon–oxygen atmosphere and to study hydrogen combustion in all noble gases providing hydrogen combustion data with suitable engine parameters to predict hydrogen ignitability under different conditions. Simulations are performed with Converge CFD software based on the Yanmar NF19SK direct injection CI (DICI) engine parameters. The results are validated with the experimental results of hydrogen combustion in an argon–oxygen atmosphere with a rapid compression expansion machine (RCEM) and modifications of the hydrogen injection timing and initial temperature are proposed. Hydrogen ignition in an argon atmosphere is dependent on a minimum initial temperature of 340 K but the combustion is slightly unstable. Helium and neon are found to be suitable for hydrogen combustion in low compression ratio (CR) engines. However krypton and xenon require temperature modification and a high CR for stable ignition. Detailed parameter recommendations are needed to improve hydrogen ignitability in conventional diesel engines with the least engine modification.

Liquid organic hydrogen carriers (LOHC) can be used as a lossless form of hydrogen storage at ambient conditions. The storage cycle consists of the exothermic hydrogenation of a hydrogen-lean molecule at the start of the transport usually the hydrogen production site becoming a hydrogen-rich molecule. This loaded molecule can be transported long distances or be used as long-term storage due to its ability to not lose hydrogen over long periods of time. At the site or time of required hydrogen production the hydrogen can be released through an endothermic dehydrogenation reaction. LOHCs show similar properties to crude oils such as petroleum and diesel allowing easy handling and possibilities of integration with current infrastructure. Using this background this paper reviews a variety of aspects of the LOHC life cycle with a focus on currently studied materials. Important factors such as the hydrogenation and dehydrogenation requirements for each material are analysed to determine their ability to be used in current scenarios. Toluene and dibenzyltoluene are attractive options with promising storage attributes however their dehydrogenation enthalpies remain a problem. The economic feasibility of LOHCs being used as a delivery device were briefly analysed. LOHCs have been shown to be the cheapest option for long distance transport (>200 km) and are cheaper than most at shorter distances in terms of specifically transport costs. The major capital cost of an LOHC delivery chain remains the initial investment for the raw materials and the cost of equipment for performing hydrogenation and dehydrogenation. Finally some studies in developing the LOHC field were discussed such as microwave enhancing parts of the process and mixing LOHCs to acquire more advantageous properties.

This paper discusses the technical specifications of how U.S. petroleum refineries can reduce facility emissions and shift to produce low-carbon fuels for hard to abate sectors by utilizing existing innovative technologies.

Austria is committed to the net-zero climate goal along with the European Union. This requires all sectors to be decarbonized. Hereby hydrogen plays a vital role as stated in the national hydrogen strategy. A report commissioned by the Austrian government predicts a minimum hydrogen demand of 16 TWh per year in Austria in 2040. Besides hydrogen imports domestic production can ensure supply. Hence this study analyses the levelized cost of hydrogen for an off-grid production plant including a proton exchange membrane electrolyzer wind power and solar photovoltaics in Austria. In the first step the capacity factors of the renewable electricity sources are determined by conducting a geographic information system analysis. Secondly the levelized cost of electricity for wind power and solarphotovoltaics plants in Austria is calculated. Thirdly the most cost-efficient portfolio of wind power and solar photovoltaics plants is determined using electricity generation profiles with a 10-min granularity. The modelled system variants differ among location capacity factors of the renewable electricity sources and the full load hours of the electrolyzer. Finally selected variables are tested for their sensitivities. With the applied model the hydrogen production cost for decentralized production plants can be calculated for any specific location. The levelized cost of hydrogen estimates range from 3.08 EUR/kg to 13.12 EUR/kg of hydrogen whereas it was found that the costs are most sensitive to the capacity factors of the renewable electricity sources and the full load hours of the electrolyzer. The novelty of the paper stems from the model applied that calculates the levelized cost of renewable hydrogen in an off-grid hydrogen production system. The model finds a cost-efficient portfolio of directly coupled wind power and solar photovoltaics systems for 80 different variants in an Austria-specific context.

The impact of hydrogen added to natural gas on the performance of commercial domestic water heating devices has been discussed in several recent papers in the literature. Much of the work focuses on performance at specific hydrogen levels (by volume) up to 20–30% as a near term blend target. In the current work new data on several commercial devices have been obtained to help quantify upper limits based on flashback limits. In addition results from 39 individual devices are compiled to help generalize observations regarding performance. The emphasis of this work is on emissions performance and especially NOx emissions. It is important to consider the reporting bases of the emissions numbers to avoid any unitended bias. For water heaters the trends associated with both mass per fuel energy input and concentration-based representation are similar For carbon free fuels bases such as 12% CO2 should be avoided. In general the compiled data shows that NOx NO UHC and CO levels decrease with increasing hydrogen percentage. The % decrease in NOx and NO is greater for low NOx devices (meaning certified to NOx <10 ng/J using premixing with excess air) compared to conventional devices (“pancake burners” partial premixing). Further low NOx devices appear to be able to accept greater amounts of hydrogen above 70% hydrogen in some cases without modification while conventional water heaters appear limited to 40–50% hydrogen. Reporting emissions on a mass basis per unit fuel energy input is preferred to the typical dry concentration basis as the greater amount of water produced by hydrogen results in a perceived increase in NOx when hydrogen is used. While this effort summarizes emissions performance with added hydrogen additional work is needed on transient operation higher levels of hydrogen system durability/reliability and heating efficiency.

The energy transition calls for natural hydrogen exploration with most occurrences discovered either inadvertently or more recently at the location of potentially diffusive circles observed from a change of vegetation cover at the surface. However some notable hydrogen occurrences are not directly associated with the presence of diffusive circles like the Bourakebougou field in Mali. Thus the objective of this work was to highlight geological areas that have some potential to find natural hydrogen in Quebec a Canadian province where no diffusive circles have yet been documented but which is rich in potential source rocks and where no exploration for natural hydrogen has been undertaken so far. A review of the different geological regions of Quebec was undertaken to highlight the relevant characteristics and geographical distribution of geological assemblages that may produce or have produced natural hydrogen in particular iron-rich rocks but also uranium-rich rocks supramature shales and zones where significant structural discontinuities are documented or suspected which may act as conduits for the migration of fluids of mantle origin. In addition to regional and local geological data an inventory of available geochemical data is also carried out to identify potential tracers or proxies to facilitate subsequent exploration efforts. A rating was then proposed based on the quality of the potential source rocks which also considers the presence of reservoir rocks and the proximity to end-users. This analysis allowed rating areas of interest for which fieldwork can be considered thus minimizing the exploratory risks and investments required to develop this resource. The size of the study area (over 1.5 million km2 ) the diversity of its geological environments (from metamorphic cratons to sedimentary basins) and their wide age range (from Archean to Paleozoic) make Quebec a promising territory for natural hydrogen exploration and to test the systematic rating method proposed here.

Fossil fuel consumption has triggered worries about energy security and climate change; this has promoted hydrogen as a viable option to aid in decarbonizing global energy systems. Hydrogen could substitute for fossil fuels in the future due to the economic political and environmental concerns related to energy production using fossil fuels. However currently the majority of hydrogen is produced using fossil fuels particularly natural gas which is not a renewable source of energy. It is therefore crucial to increase the efforts to produce hydrogen from renewable sources rather from the existing fossil-based approaches. Thus this study investigates how renewable energy can accelerate the production of hydrogen fuel in the future under three hydrogen economy-related energy regimes including nuclear restrictions hydrogen and city gas blending and in the scenarios which consider the geographic distribution of carbon reduction targets. A random effects regression model has been utilized employing panel data from a global energy system which optimizes for cost and carbon targets. The results of this study demonstrate that an increase in renewable energy sources has the potential to significantly accelerate the growth of future hydrogen production under all the considered policy regimes. The policy implications of this paper suggest that promoting renewable energy investments in line with a fairer allocation of carbon reduction efforts will help to ensure a future hydrogen economy which engenders a sustainable low carbon society.

Within integrated steelmaking industries significant research efforts are devoted to the efficient use of resources and the reduction of CO2 emissions. Integrated steelworks consume a considerable quantity of raw materials and produce a high amount of by-products such as off-gases currently used for the internal production of heat steam or electricity. These off-gases can be further valorized as feedstock for methane and methanol syntheses but their hydrogen content is often inadequate to reach high conversions in synthesis processes. The addition of hydrogen is fundamental and a suitable hydrogen production process must be selected to obtain advantages in process economy and sustainability. This paper presents a comparative analysis of different hydrogen production processes from renewable energy namely polymer electrolyte membrane electrolysis solid oxide electrolyze cell electrolysis and biomass gasification. Aspen Plus® V11-based models were developed and simulations were conducted for sensitivity analyses to acquire useful information related to the process behavior. Advantages and disadvantages for each considered process were highlighted. In addition the integration of the analyzed hydrogen production methods with methane and methanol syntheses is analyzed through further Aspen Plus®-based simulations. The pros and cons of the different hydrogen production options coupled with methane and methanol syntheses included in steelmaking industries are analyzed

The path to the mitigation of global climate change and global carbon dioxide emissions avoidance leads to the large-scale substitution of fossil fuels for the generation of electricity with renewable energy sources. The transition to renewables necessitates the development of large-scale energy storage systems that will satisfy the hourly demand of the consumers. This paper offers an overview of the energy storage systems that are available to assist with the transition to renewable energy. The systems are classified as mechanical (PHS CAES flywheels springs) electromagnetic (capacitors electric and magnetic fields) electrochemical (batteries including flow batteries) hydrogen and thermal energy storage systems. Emphasis is placed on the magnitude of energy storage each system is able to achieve the thermodynamic characteristics the particular applications the systems are suitable for the pertinent figures of merit and the energy dissipation during the charging and discharging of the systems.

The green hydrogen–electric coupling system can consume locally generated renewable energy thereby improving energy utilization and enabling zero-carbon power supply within a certain range. This study focuses on a green hydrogen–electric coupling system that integrates photovoltaic energy storage and proton exchange membrane electrolysis (PEME). Firstly the impact of operating temperature power quality and grid auxiliary services on the characteristics of the electrolysis cell is analyzed and a voltage model and energy model for the cell are established. Secondly a multi-operating conditions adaptability experiment for PEME grid-connected operation is designed. A test platform consisting of a grid simulator simulated photovoltaic power generation system lithium battery energy storage system PEME and measurement and acquisition device is then built. Finally experiments are conducted to simulate multi-operating conditions such as temperature changes voltage fluctuations frequency offsets harmonic pollution and current adjustment speed. The energy efficiency and consumption is calculated based on the recorded data and the results are helpful to guide the operation of the system.

National Implementation Plans (NIP) in regard hydrogenation motor transport are in place in European Union (EU) countries e.g.Germany France or Belgium Denmark Netherlands. Motor transport hydrogenization plans exist in the Japan and USA. In Poland the methodology deployment Hydrogen Refuelling Stations (HRS) developed in Motor Transport Institute is of multi-stage character are as follows: Stage I: Method allowing to identify regions in which HRS should be located. Stage II: Method allowing to identify urban centres in which should be located the said stations. Stage III: Method for determining the area of the station location. The presentation of the aforesaid NIPS and based on that and the mentioned methodology the conditions for hydrogenization of motor transport in Poland is the purpose of this article which constitutes its novelty. The scope of the article concerns the hydrogenization of motor transport in the abovementioned countries. With the above criteria the order the construction in Poland of a HRS in the order of their creation along the TEN-T corridors is as follows: 1 - Poznan 2 - Warsaw 3 - Bialystok 4 - Szczecin 5 - the Lodz region 6 - the Tri-City region 7 - Wrocław 8 - the Katowice region 9 – Krakow. The concluding discussion sets out the status of deployment HRS and FCEVs in the analysed countries.

This study presents the results of economic and environmental analysis for two types of zero-emission ships (ZESs) that are receiving more attention to meet strengthened environmental regulations. One of the two types of ZES is the ZES using only the energy storage system (All-ESS) and the other is the ZES with fuel cell and ESS hybrid system (FC–ESS). The target ship is a tug operating in South Korea and the main parameters are based on the specific circumstances of South Korea. The optimal capacity of the ESS for each proposed system is determined using an optimization tool. The total cost for a ship’s lifetime is calculated using economic analysis. The greenhouse gas (GHG) emission for the fuel’s lifecycle (well-to-wake) is calculated using environmental analysis. The results reveal that the proposed ZESs are 1.7–3.4 times more expensive than the conventional marine gas oil (MGO)-fueled ship; however it could be reduced by 1.3–2.4 times if the carbon price is considered. The proposed ZESs have 58.7–74.3% lower lifecycle GHG emissions than the one from the conventional ship. The results also highlight that the electricity- or hydrogen-based ZESs should reduce GHG emissions from the upstream phase (well-to-tank) to realize genuine ZESs.

This paper presents a wind-methanol-fuel cell system with hydrogen storage. It can manage various energy flow to provide stable wind power supply produce constant methanol and reduce CO2 emissions. Firstly this study establishes the theoretical basis and formulation algorithms. And then computational experiments are developed with MATLAB/Simulink (R2016a MathWorks Natick MA USA). Real data are used to fit the developed models in the study. From the test results the developed system can generate maximum electricity whilst maintaining a stable production of methanol with the aid of a hybrid energy storage system (HESS). A sophisticated control scheme is also developed to coordinate these actions to achieve satisfactory system performance.

China is the world’s largest producer and consumer of hydrogen. The country has adopted a domestic strategy that targets significant growth in hydrogen consumption and production. Given the importance of hydrogen in the low-carbon energy transition it is critical to understand China’s hydrogen policies and their implementation as well as the extent to which these contribute to the country’s low-carbon goals.<br/>Existing research has focused on understanding policies and regulations in China and their implications for the country’s hydrogen prospects. This study aims to improve our understanding of central-government initiatives and look at how China’s hydrogen policies are implemented at the local level. The paper examines the three cities of Zhangjiakou (in China’s renewable-rich Hebei province) Datong (in the country’s coal-heartland of Shanxi province) and Chengdu which is rich in hydropower and natural gas. To be sure the three cities analysed in this paper do not cover all regional plans and initiatives but they offer a useful window into local hydrogen policy implementation. They also illustrate the major challenges facing green hydrogen as it moves beyond the narrow highly subsidized field of fuel cell vehicles (FCVs). Indeed costs as well as water land availability and technology continue to be constraints.<br/>The hydrogen policies and road maps reviewed in this paper offer numerous targets—often setting quantitative goals for FCVs hydrogen refuelling stations hydrogen supply chain revenue and new hydrogen technology companies—aligning with the view that hydrogen development is currently more of an industrial policy than a decarbonisation strategy. Indeed hydrogen’s potential to decarbonise sectors such as manufacturing and chemicals is of secondary importance if mentioned at all. But as the cities analysed here view hydrogen as part of their industrial programmes economic development and climate strategies support is likely to remain significant even as the specific incentive schemes will likely evolve.<br/>Given this local hydrogen development model rising demand for hydrogen in China could ultimately increase rather than decrease CO₂ emissions from fossil fuels in the short run. At the same time even though the central government’s hydrogen targets (as laid out in its 2022 policy documents) seem relatively conservative Chinese cities’ appetite for new sources of growth and the ability to fund various business models are worth watching.

Decarbonising energy is fundamental in the transition towards a sustainable future. Our Future Energy Scenarios aim to stimulate debate to inform the decisions that will help move us towards achieving carbon reduction targets and ultimately shape the energy system of the future.

Supporting policies to achieve a green revolution and ecological transition is a global trend. Although the maritime transport of goods and people can rightly be counted among the least polluting sectors much can be done to further reduce its environmental footprint. Moreover to boost the ecological transition of vessels a whole series of international regulations and national laws have been promulgated. Among these the most impactful on both design and operational management of ships concern the containment of air-polluting emissions in terms of GHG NOx SOx and PM. To address this challenge it might seem that many technologies already successfully used in other transport sectors could be applied. However the peculiar characteristics of ships make this statement not entirely true. In fact technological solutions recently adopted for example in the automotive sector must deal with the large size of vessels and the consequent large amount of energy necessary for their operation. In this paper with reference to the case study of a medium/large-sized passenger cruise ship the use of different fuels (LNG ammonia hydrogen) and technologies (internal combustion engines fuel cells) for propulsion and energy generation on board will be compared. By imposing the design constraint of not modifying the payload and the speed of the ship the criticalities linked to the use of one fuel rather than another will be highlighted. The current limits of application of some fuels will be made evident with reference to the state of maturity of the relevant technologies. Furthermore the operational consequences in terms of autonomy reduction will be presented. The obtained results underline the necessity for shipowners and shipbuilders to reflect on the compromises required by the challenges of the ecological transition which will force them to choose between reducing payload or reducing performance.

Traditional charging stations have a single function which usually does not consider the construction of energy storage facilities and it is difficult to promote the consumption of new energy. With the gradual increase in the number of new energy vehicles (NEVs) to give full play to the complementary advantages of source-load resources and provide safe efficient and economical energy supply services this paper proposes the optimal operation strategy of a PV-charging-hydrogenation composite energy station (CES) that considers demand response (DR). Firstly the operation mode of the CES is analyzed and the CES model including a photovoltaic power generation system fuel cell hydrogen production hydrogen storage hydrogenation and charging is established. The purpose is to provide energy supply services for electric vehicles (EVs) and hydrogen fuel cell vehicles (HFCVs) at the same time. Secondly according to the travel law of EVs and HFCVs the distribution of charging demand and hydrogenation demand at different periods of the day is simulated by the Monte Carlo method. On this basis the following two demand response models are established: charging load demand response based on the price elasticity matrix and interruptible load demand response based on incentives. Finally a multi-objective optimal operation model considering DR is proposed to minimize the comprehensive operating cost and load fluctuation of CES and the maximum–minimum method and analytic hierarchy process (AHP) are used to transform this into a linearly weighted single-objective function which is solved via an improved moth–flame optimization algorithm (IMFO). Through the simulation examples operation results in four different scenarios are obtained. Compared with a situation not considering DR the operation strategy proposed in this paper can reduce the comprehensive operation cost of CES by CNY 1051.5 and reduce the load fluctuation by 17.8% which verifies the effectiveness of the proposed model. In addition the impact of solar radiation and energy recharge demand changes on operations was also studied and the resulting data show that CES operations were more sensitive to energy recharge demand changes.

Tropical countries can approach their natural resources to produce low-carbon H2 from solar wind hydro and biomass resources to satisfy their domestic demand and to export it. To do so Colombia published the National Hydrogen Roadmap in which green H2 was prioritized. This study estimates Colombia's potential to produce green H2 and a timeline of scenarios displaying the required installed capacity capital investment and environmental analysis related to water utilization and CO2 capture. Accordingly Colombia can produce H2 at a rate of 9 Mt/a by 2050 by installing 121 GW renewables while processing 303 Mt/a of residual biomass. In this scenario Colombia's share of the H2 international market can reach 1.2% with a cumulative investment of over 244 billion USD by 2050. This study provides insights into potential global resources for low-carbon H2 generation.

Hydrogen has recently been proposed as a versatile energy carrier to contribute to archiving universal access to clean cooking. In hard-to-reach rural settings decentralized produced hydrogen may be utilized (i) as a clean fuel via direct combustion in pure gaseous form or blended with Liquid Petroleum Gas (LPG) or (ii) via power-to-hydrogen-to-power (P2H2P) to serve electric cooking (e-cooking) appliances. Here we present the first techno-economic evaluation of hydrogen-based cooking solutions. We apply mathematical optimization via energy system modeling to assess the minimal cost configuration of each respective energy system on technical and economic measures under present and future parameters. We further compare the potential costs of cooking for the end user with the costs of cooking with traditional fuels. Today P2H2P-based e-cooking and production of hydrogen for utilization via combustion integrated into the electricity supply system have almost equal energy system costs to simultaneously satisfy the cooking and electricity needs of the isolated rural Kenyan village studied. P2H2P-based e-cooking might become advantageous in the near future when improving the energy efficiency of e-cooking appliances. The economic efficiency of producing hydrogen for utilization by end users via combustion benefits from integrating the water electrolysis into the electricity supply system. More efficient and cheaper hydrogen technologies expected by 2050 may improve the economic performance of integrated hydrogen production and utilization via combustion to be competitive with P2H2P-based e-cooking. The monthly costs of cooking per household may be lower than the traditional use of firewood and charcoal even today when applying the current life-line tariff for the electricity consumed or utilizing hydrogen via combustion. Driven by likely future technological improvements and the expected increase in traditional and fossil fuel prices any hydrogen-based cooking pathway may be cheaper for end users than using charcoal and firewood by 2030 and LPG by 2040. The results suggest that providing clean cooking in rural villages could economically and environmentally benefit from utilizing hydrogen. However facing the complexity of clean cooking projects we emphasize the importance of embedding the results of our techno-economic analysis in holistic energy delivery models. We propose useful starting points for future aspects to be investigated in the discussion section including business and financing models.

Although polymer electrolyte water electrolyzers (PEWEs) have been used in small-scale (kW to tens of kW range) applications for several decades PEWE technology for hydrogen production in energy applications (power-to-gas power-to-fuel etc.) requires significant improvements in the technology to address the challenges associated with cost performance and durability. Systems with power of hundreds of kW or even MWs corresponding to hydrogen production rates of around 10 to 20 kg/h have started to appear in the past 5 years. The thin (∼0.2 mm) polymer electrolyte in the PEWE with low ohmic resistance compared to the alkaline cell with liquid electrolyte allows operation at high current densities of 1–3 A/cm2 and high differential pressure. This article after an introductory overview of the operating principles of PEWE and state-of-the-art discusses the state of understanding of key phenomena determining and limiting performance durability and commercial readiness identifies important ‘gaps’ in understanding and essential development needs to bring PEWE science & engineering forward to prosper in the energy market as one of its future backbone technologies. For this to be successful science engineering and process development as well as business and market development need to go hand in hand.

Electrochemical ammonia generation allows direct low pressure synthesis of ammonia as an alternative to the established Haber-Bosch process. The increasing need to drive industry with renewable electricity central to decarbonisation and electrochemical ammonia synthesis offers a possible efficient and low emission route for this increasingly important chemical. It also provides a potential route for more distributed and small-scale ammonia synthesis with a reduced production footprint. Electrochemical ammonia synthesis is still early stage but has seen recent acceleration in fundamental understanding. In this work two different ammonia electrolysis systems are considered. Balance of plant (BOP) requirements are presented and modelled to compare performance and determine trade-offs. The first option (water fed cell) uses direct ammonia synthesis from water and air. The second (hydrogen-fed cell) involves a two-step electrolysis approach firstly producing hydrogen followed by electrochemical ammonia generation. Results indicate that the water fed approach shows the most promise in achieving low energy demand for direct electrochemical ammonia generation. Breaking the reaction into two steps for the hydrogen fed approach introduces a source of inefficiency which is not overcome by reduced BOP energy demands and will only be an attractive pathway for reactors which promise both high efficiency and increased ammonia formation rate compared to water fed cells. The most optimised scenario investigated here with 90% faradaic efficiency (FE) and 1.5 V cell potential (75% nitrogen utilisation) gives a power to ammonia value of 15 kWh/kg NH3 for a water fed cell. For the best hydrogen fed arrangement the requirement is 19 kWh/kg NH3. This is achieved with 0.5 V cell potential and 75% utilisation of both hydrogen and nitrogen (90% FE). Modelling demonstrated that balance of plant requirements for electrochemical ammonia are significant. Electrochemical energy inputs dominate energy requirements at low FE however in cases of high FE the BOP accounts for approximately 50% of the total energy demand mostly from ammonia separation requirements. In the hydrogen fed cell arrangement it was also demonstrated that recycle of unconverted hydrogen is essential for efficient operation even in the case where this increases BOP energy inputs

Alternative fuels are crucial to decarbonize the European maritime transport but their net climate benefits vary with the type of fuel and production country. In this study we assess the energy potential and climate change mitigation benefits of using agricultural and forest residues in different European countries for drop-in (Fast Pyrolysis Hydrothermal Liquefaction and Gasification to Fischer-Tropsch fuels or Bio-Synthetic Natural Gas) and hydrogen-based biofuels (hydrogen ammonia and methanol) with or without carbon capture and storage (CCS). Our results show the combinations of countries and biofuel options that successfully achieve the decarbonization targets set by the FuelEU Maritime initiative for the next years including a prospective analysis that include technological changes projected for the biofuel supply chains until 2050. With the current technologies the largest greenhouse gas (GHG) mitigation potential per year at a European scale is obtained with bio-synthetic natural gas and hydrothermal liquefaction. Among carbon-free biofuels ammonia currently has higher mitigation but hydrogen can achieve a lower GHG intensity per unit of energy with the projected decarbonization of the electricity mixes until 2050. The full deployment of CCS can further accelerate the decarbonization of the maritime sector. Choosing the most suitable renewable fuels requires a regional perspective and a transition roadmap where countries coordinate actions to meet ambitious climate targets.

Ammonia (NH3) is among the largest-volume chemicals produced and distributed in the world and is mainly known for its use as a fertilizer in the agricultural sector. In recent years it has sparked interest in the possibility of working as a high-quality energy carrier and as a carbon-free fuel in internal combustion engines (ICEs). This review aimed to provide an overview of the research on the use of green ammonia as an alternative fuel for ICEs with a look to the future on possible applications and practical solutions to related problems. First of all the ammonia production process is discussed. Present ammonia production is not a “green” process; the synthesis occurs starting from gaseous hydrogen currently produced from hydrocarbons. Some ways to produce green ammonia are reviewed and discussed. Then the chemical and physical properties of ammonia as a fuel are described and explained in order to identify the main pros and cons of its use in combustion systems. Then the most viable solutions for fueling internal combustion engines with ammonia are discussed. When using pure ammonia high boost pressure and compression ratio are required to compensate for the low ammonia flame speed. In spark-ignition engines adding hydrogen to ammonia helps in speeding up the flame front propagation and stabilizing the combustion. In compression-ignition engines ammonia can be successfully used in dual-fuel mode with diesel. On the contrary an increase in NOx and the unburned NH3 at the exhaust require the installation of apposite aftertreatment systems. Therefore the use of ammonia seems to be more practicable for marine or stationary engine application where space constraints are not a problem. In conclusion this review points out that ammonia has excellent potential to play a significant role as a sustainable fuel for the future in both retrofitted and new engines. However significant further research and development activities are required before being able to consider large-scale industrial production of green ammonia. Moreover uncertainties remain about ammonia safe and effective use and some technical issues need to be addressed to overcome poor combustion properties for utilization as a direct substitute for standard fuels.

The report “Policy Toolbox for Low Carbon and Renewable Hydrogen” is based on an assessment of the performance of hydrogen policies in different stages of market maturity and segments of the value chain. 48 policies were shortlisted based on their economic efficiency and effectiveness and mapped to barriers across the value chain and over time. These policies were subsequently clustered into policy packages for three country archetypes: a self-sufficient hydrogen producer an importer and an exporter of hydrogen.

The paper can be found on their website.