Publications

Alternative and especially renewable marine fuels are needed to reduce the environmental and climate impacts of the shipping sector. This paper investigates the business case for hydrogen as an alternative fuel in a new-built vessel utilizing fuel cells and liquefied hydrogen. A real option approach is used to model the optimal time and costs for investment as well as the value of deferring an investment as a result of uncertainty. This model is then used to assess the impact of a carbon tax on a ship owner’s investment decision. A low carbon tax results in ship owners deferring investments which then slows the uptake of the technology. We recommend that policymakers set a high carbon tax at an early stage in order to help hydrogen compete with fossil fuels. A clear and timely policy design promotes further investments and accelerates the uptake of new technologies that can fulfill decarbonization targets.

This paper deals with the main safety aspects of the EOS project. The partners of the project – Politecnico di Torino Gas Turbine Technologies (GTT Siemens group) Hysylab (Hydrogen System Laboratory) of Environment Park and Regione Piemonte – aim to create the main node of a regional fuel cell generator network. As a first step the Pennsylvania-based Stationary Fuel Cells division of Siemens Westinghouse Power Corporation (SWPC) supplied GTT with a CHP 100 kWe SOFC (Solide Oxide Fuel Cell) field unit fuelled by natural gas with internal reforming. The fuel cell is connected to the electricity national grid and provides part of the industrial district energy requirement. The thermal energy from the fuel cells is used for heating and air-conditioning of GTT offices bringing the total first Law efficiency of the plant to 70-80%. In the second phase of the EOS project (2007/2008) the maximum power produced by the SOFC systems installed in the GTT EOS test room will be increased to a total of about 225 kWe by means of an additional SOFC generator rated 125 kWe and up to 115 kWth. The paper provides information about the safety analysis which was performed during the main steps of the design of the system i.e. the HAZOP during the SOFC design by SWPC and the safety evaluations during the test hall design by GTT and Politecnico di Torino.

Nowadays heterogeneous photocatalysis for water treatment and hydrogen production are topics gaining interest for scientists and developers from different areas such as environmental technology and material science. Most of the efforts and resources are devoted to the development of new photocatalyst materials while the modeling and development of reaction systems allowing for upscaling the process to pilot or industrial scale are scarce. In this work we present what is known on the upscaling of heterogeneous photocatalysis to purify water and to produce green H2. The types of reactors successfully used in water treatment plants are presented as study cases. The challenges of upscaling the photocatalysis process to produce green H2 are explored from the perspectives of (a) the adaptation of photoreactors (b) the competitiveness of the process and (c) safety. Throughout the text Green Chemistry and Engineering Principles are described and discussed on how they are currently being applied to the heterogeneous photocatalysis process along with the challenges that are ahead. Lastly the role of automation and high-throughput methods in the upscaling following the Green Principles is discussed.

The Republic of Djibouti has untapped potential in terms of renewable energy resources such as geothermal wind and solar energy. This study examines the economic feasibility of green hydrogen production by water electrolysis using wind and geothermal energy resources in the Asal–Ghoubbet Rift (AG Rift) Republic of Djibouti. It is the first study in Africa that compares the cost per kg of green hydrogen produced by wind and geothermal energy from a single site. The unit cost of electricity produced by the wind turbine (0.042 $/kWh) is more competitive than that of a dry steam geothermal plant (0.086 $/kWh). The cost of producing hydrogen with a suitable electrolyzer powered by wind energy ranges from $0.672/kg H2 to $1.063/kg H2 while that produced by the high-temperature electrolyzer (HTE) powered by geothermal energy ranges from $3.31/kg H2 to $4.78/kg H2 . Thus the AG Rift area can produce electricity and green hydrogen at low-cost using wind energy compared to geothermal energy. The amount of carbon dioxide (CO2 ) emissions reduced by using a “Yinhe GX113-2.5MW” wind turbine and a single flash geothermal power plant instead of fuel-oil generators is 2061.6 tons CO2/MW/year and 2184.8 tons CO2/MW/year respectively.

An essential prerequisite for safe transport and use of natural gas is their appropriate odorization. This enables the detection of uncontrolled gas leaks. Proper and systematic odorization inspection ensures both safe use of gas and continuity of the process itself. In practice it is conducted through among others measuring odorant concentrations in gas. Control devices for rapid gas odorization measurements that are currently used on a large scale in the gas industry are equipped with electrochemical detectors selective for sulfur compounds like tetrahydrothiophene (THT). Because the selectivity of electrochemical detector response to one compound (e.g. THT) the available declarations of manufacturers show that detector sensitivity (indirectly also the quality of the measurement result) is influenced by the presence of increased e.g. sulfur or hydrogen compound content in the gas. Because of the lack of sufficient source literature data in this field it was necessary to experimentally verify this impact. The results of studies on experimental verification of suspected influence of increased amounts of hydrogen in gas on the response of electrochemical detector was carried out at the Oil and Gas Institute—National Research Institute (INiG—PIB). They are presented in this article. The data gathered in the course of researching the dependence between THT concentration measurement result quality and hydrogen content in gas composition enabled a preliminary assessment of the threat to the safety of end users of gaseous fuels caused by the introduction of this gas into the distribution network. Noticing the scope of necessary changes in the area of odorization is necessary to guarantee this safety.

The H21 National Innovation Competition project is examining the feasibility of repurposing the existing GB natural gas distribution network for transporting 100% hydrogen. It aims to undertake an experimental testing programme that will provide the necessary data to quantify the comparative risk between a 100% hydrogen network and the natural gas network. The first phase of the project focuses on leakage testing of a strategic set of assets that have been removed from service which provide a representative sample of assets across the network. This paper presents the work undertaken for Phase 1A (background testing) where HSE and industry partners have tested a range of natural gas pipework assets of varying size material age and pressure-rating in a new bespoke open-air testing facility at the HSE Science and Research Centre Buxton. The assets have been pressurised with hydrogen and then methane and the leakage rate from the assets measured in both cases. The main finding of this work is that the assets tested which leak hydrogen also leak methane. None of the assets were found to leak hydrogen but not methane. In addition repair techniques that were effective at stopping methane leaks were also effective at stopping hydrogen leaks. The data from the experiments have been interpreted to obtain a range of leakage ratios between the two gases for releases under different conditions. This has been compared to the predicted ratio of hydrogen to methane volumetric leak rates for laminar (1.2:1) and turbulent (2.9:1) releases and good agreement was observed.

Leading countries are developing clean energy to replace fossil fuels. In this context Russia is changing its energy policy towards fostering new energy resources such as hydrogen and helium. Hydrogen will not only contribute to Russia’s financial revenue by replacing natural gas but will also provide a basis for it to maintain its dominance over the international energy market by pioneering new energy markets. Russia is aiming to produce more than two million tons of hydrogen fuel for export to Europe and Asia by 2035. However it is facing many challenges including developing hydrogen fuel storage systems acquiring the technology required for exporting hydrogen and building trust in the fuel market. Meanwhile South Korea has a foundation for developing a hydrogen industry as it has the highest capacity in the world to produce fuel cells and the ability to manufacture LNG: (liquefied natural gas) carriers. Therefore South Korea and Russia have sufficient potential to create a new complementary and reciprocal cooperation model in the hydrogen fuel field. This study examines the present and future of Russia’s energy policy in this area as well as discusses South Korea and Russia’s cooperation plans in the hydrogen fuel sector and the related implications.

This paper investigates the optimal planning of microgrids including the hydrogen energy system through mixed-integer linear programming model. A real case study is analyzed by extending the only microgrid lab facility in Austria. The case study considers the hydrogen production via electrolysis seasonal storage and fuelling station for meeting the hydrogen fuel demand of fuel cell vehicles busses and trucks. The optimization is performed relative to two different reference cases which satisfy the mobility demand by diesel fuel and utility electricity based hydrogen fuel production respectively. The key results indicate that the low emission hydrogen mobility framework is achieved by high share of renewable energy sources and seasonal hydrogen storage in the microgrid. The investment optimization scenarios provide at least 66% and at most 99% carbon emission savings at increased costs of 30% and 100% respectively relative to the costs of the diesel reference case (current situation)

In order to ensure the safety of shore-based hydrogen bunkering operations this paper takes a 2000-ton bulk hydrogen powered ship as an example. Firstly the HAZID method is used to identify the hazards of hydrogen bunkering then the probability of each scenario is analyzed and then the consequences of scenarios with high risk based on FLACS software is simulated. Finally the personal risk of bunkering operation is evaluated and the bunkering restriction area is defined. The results show that the personal risk of shore-based bunkering operation of hydrogen powered ship is acceptable but the following risk control measures should be taken: (1) The bunkering restriction area shall be delineated and only the necessary operators are allowed to enter the area and control the any form of potential ignition source; (2) The hose is the high risk hazards during bunkering. The design form of bunkering arm and bunkering hose is considered to shorten the length of the hose as far as possible; (3) A safe distance between shore-based hydrogenation station and the building outside the station should be guaranteed. The results have a guiding role in effectively reducing the risk of hydrogen bunkering operation.

Current standard practice at wastewater treatment plants (WWTPs) involves the recycling of digestate liquor produced from the anaerobic digestion of sludge back into the treatment process. However a significant amount of energy is required to enable biological breakdown of ammonia present in the liquor. This biological processing also results in the emission of damaging quantities of greenhouse gases making diversion of liquor and recovery of ammonia a noteworthy option for improving the sustainability of wastewater treatment. This study presents a novel process which combines ammonia recovery from diverted digestate liquor for use (alongside biomethane) in a solid oxide fuel cell (SOFC) system for implementation at WWTPs. Aspen Plus V.8.8 and numerical steady state models have been developed using data from a WWTP in West Yorkshire (UK) as a reference facility (750000p.e.). Aspen Plus simulations demonstrate an ability to recover 82% of ammoniacal nitrogen present in digestate liquor produced at the WWTP. The recovery process uses a series of stripping absorption and flash separation units where water is recovered alongside ammonia. This facilitates effective internal steam methane as a case of study has the potential to make significant impacts energetically and environmentally; findings suggest the treatment facility could transform from a net consumer of electricity to a net producer. The SOFC has been demonstrated to run at an electrical efficiency of 48% with NH3 contributing 4.6% of its power output. It has also been demonstrated that 3.5 kg CO2e per person served by the WWTP could be mitigated a year due to a combination of emissions savings by diversion of ammonia from biological processing and lifecycle emissions associated with the lack of reliance on grid electricity.

Power to substitute natural gas (PtSNG) is a promising technology to store intermittent renewable electricity as synthetic fuel. Power surplus on the electric grid is converted to hydrogen via water electrolysis and then to SNG via CO2 methanation. The SNG produced can be directly injected into the natural gas infrastructure for long-term and large-scale energy storage. Because of the fluctuating behaviour of the input energy source the overall annual plant efficiency and SNG production are affected by the plant operation time and the standby strategy chosen. The re-use of internal (waste) heat for satisfying the energy requirements during critical moments can be crucial to achieving high annual efficiencies. In this study the heat recovery from a PtSNG plant coupled with wind energy based on proton exchange membrane electrolysis adiabatic fixed bed methanation and membrane technology for SNG upgrading is investigated. The proposed thermal recovery strategy involves the waste heat available from the methanation unit during the operation hours being accumulated by means of a two-tanks diathermic oil circuit. The stored heat is used to compensate for the heat losses of methanation reactors during the hot-standby state. Two options to maintain the reactors at operating temperature have been assessed. The first requires that the diathermic oil transfers heat to a hydrogen stream which is used to flush the reactors in order to guarantee the hot-standby conditions. The second option entails that the stored heat being recovered for electricity production through an Organic Rankine Cycle. The electricity produced is used to compensate the reactors heat losses by using electrical trace heating during the hot-standby hours as well as to supply energy to ancillary equipment. The aim of the paper is to evaluate the technical feasibility of the proposed heat recovery strategies and how they impact on the annual plant performances. The results showed that the annual efficiencies on an LHV basis were found to be 44.0% and 44.3% for the thermal storage and electrical storage configurations respectively.

The demand for fossil fuels is increasing because of globalization and rising energy demands. As a result many nations are exploring alternative energy sources and hydrogen is an efficient and practical alternative fuel. In the transportation industry the development of hydrogen-powered cars aims to maximize fuel efficiency and significantly reduce exhaust gas emission and concentration. The impact of using hydrogen as a supplementary fuel for spark ignition (SI) and compression ignition (CI) engines on engine performance and gas emissions was investigated in this study. By adding hydrogen as a fuel in internal combustion engines the torque power and brake thermal efficiency of the engines decrease while their brake-specific fuel consumption increase. This study suggests that using hydrogen will reduce the emissions of CO UHC CO2 and soot; however NOx emission is expected to increase. Due to the reduction of environmental pollutants for most engines and the related environmental benefits hydrogen fuel is a clean and sustainable energy source and its use should be expanded.

As a countermeasure to the greenhouse gas problem the world is focusing on alternative fuel vehicles (AFVs). The most prominent alternatives are battery electric vehicles (BEV) and fuel cell electric vehicles (FCEVs). This study examines FCEVs especially considering hydrogen refueling stations to fill the gap in the research. Many studies suggest the important impact that infrastructure has on the diffusion of AFVs but they do not provide quantitative preferences for the design of hydrogen refueling stations. This study analyzes and presents a consumer preference structure for hydrogen refueling stations considering the production method distance probability of failure to refuel number of dispensers and fuel costs as core attributes. For the analysis stated preference data are applied to choice experiments and mixed logit is used for the estimation. Results indicate that the supply stability of hydrogen refueling stations is the second most important attribute following fuel price. Consumers are willing to pay more for green hydrogen compared to gray hydrogen which is hydrogen produced by fossil fuels. Driver fuel type and perception of hydrogen energy influence structure preference. Our results suggest a specific design for hydrogen refueling stations based on the characteristics of user groups.

One strategy for arresting propagating detonation waves in pipes is by imposing a sudden area enlargement which provides a rapid lateral divergence of the gases in the reaction zone and attenuates the leading shock. For sufficiently small tube diameter the detonation decays to a deflagration and the shock decays to negligible strengths. This is known as the critical tube diameter problem. In the present study we provide a closed form model to predict the detonation quenching for 2D channels. This problem also applies to the transmission of a detonation wave from a confined layer to a weakly-confined layer. Whitham’s geometric shock dynamics coupled with a shock evolution law based on shocks sustained by a constant source obtained by the shock change equations of Radulescu is shown to capture the lateral shock dynamics response to the failure wave originating at the expansion corner. A criterion for successful detonation transmission to open space is that the lateral strain rate provided by the failure wave not exceed the critical strain rate of steady curved detonations. Using the critical lateral strain rate obtained by He and Clavin a closed form solution is obtained for the critical channel opening permitting detonation transmission. The predicted critical channel width is found in excellent agreement with our recent experiments and simulations of diffracting H2/O2/Ar detonations. Model comparison with available data for H2/air detonation diffraction into open space at ambient conditions or for transmission into a weakly confined layer by air is also found in good agreement within a factor never exceeding 2 for the critical opening or layer dimension.

Various concepts have been proposed to use hydrocarbon fuels in solid oxide fuel cell (SOFC) systems. A combination of either allothermal or adiabatic pre-reforming and water recirculation (WR) or anode off-gas recirculation (AOGR) is commonly used to convert the fuel into a hydrogen rich mixture before it is electrochemically oxidised in the SOFC. However it is unclear how these reforming concepts affect the electrochemistry and temperature gradients in the SOFC stack. In this study four reforming concepts based on either allothermal or adiabatic pre-reforming and either WR or AOGR are modelled on both stack and system level. The electrochemistry and temperature gradients in the stack are simulated with a one-dimensional SOFC model and the results are used to calculate the corresponding system efficiencies. The highest system efficiencies are obtained with allothermal pre-reforming and WR. Adiabatic pre-reforming and AOGR result in a higher degree of internal reforming which reduces the cell voltage compared to allothermal pre-reforming and WR. Although this lowers the stack efficiency higher degrees of internal reforming reduce the power consumption by the cathode air blower as well leading to higher system efficiencies in some cases. This illustrates that both stack and system operation need to be considered to design an efficient SOFC system and predict potentially deteriorating temperature gradients in the stack.

The major demand of energy in today’s world is fulfilled by the fossil fuels which are not renewable in nature and can no longer be used once exhausted. In the beginning of the 21st century the limitation of the fossil fuels continually growing energy demand and growing impact of greenhouse gas emissions on the environment were identified as the major challenges with current energy infrastructure all over the world. The energy obtained from fossil fuel is cheap due to its established infrastructure; however these possess serious issues as mentioned above and cause bad environmental impact. Therefore renewable energy resources are looked to as contenders which may fulfil most energy requirements. Among them hydrogen is considered as the most environmentally friendly fuel. Hydrogen is clean sustainable fuel and it has promise as a future energy carrier. It also has the ability to substitute the present energy infrastructure which is based on fossil fuel. This is seen and projected as a solution for the above-mentioned problems including rise in global temperature and environmental degradation. Environmental and economic aspects are the important factors to be considered to establish hydrogen infrastructure. This article describes the various aspects of hydrogen including production storage and applications with a focus on fuel cell based electric vehicles. Their environmental as well as economic aspects are also discussed herein.

In order to limit the effects of climate change the carbon dioxide emissions associated with the energy sector need to be reduced. Significant reductions can be achieved by using appropriate technologies and policies. In the context of recent discussions about climate change and energy transition this article critically reviews some technologies policies and frequently discussed solutions. The options for carbon emission reductions are grouped into (1) generation of secondary energy carriers (2) end-use energy sectors and (3) sector interdependencies. The challenges on the way to a decarbonized energy sector are identified with respect to environmental sustainability security of energy supply economic stability and social aspects. A global carbon tax is the most promising instrument to accelerate the process of decarbonization. Nevertheless this process will be very challenging for humanity due to high capital requirements the competition among energy sectors for decarbonization options inconsistent environmental policies and public acceptance of changes in energy use.

This paper describes a generic and systematic method to calculate the efficiency and the annual performance for Power-to-Gas (PtG) systems. This approach gives the basis to analytically compare different PtG systems using different technologies under different boundary conditions. To have a comparable basis for efficiency calculations a structured break down of the PtG system is done. Until now there has not been a universal approach for efficiency calculations. This has resulted in a wide variety of efficiency calculations used in feasibility studies and for business-case calculations. For this the PtG system is divided in two sub-systems: the electrolysis and the methanation. Each of the two sub-systems consists of several subsystem boundary levels. Staring from the main unit i.e. the electrolysis stack and/or methanation reactor further units that are required to operate complete PtG system are considered with their respective subsystem boundary conditions. The paper provides formulas how the efficiency of each level can be calculated and how efficiency deviations can be integrated which are caused by the extended energy flow calculations to and from energy users and thermal losses. By this a sensitivity analysis of the sub-systems can be gained and comprehensive goal functions for optimizations can be defined. In a second step the annual performance of the system is calculated as the ratio of useable output and energetic input over one year. The input is the integral of the annual need of electrical and thermal energy of a PtG system depending on the different operation states of the plant. The output is the higher heating value of the produced gas and – if applicable – heat flows that are used externally. The annual performance not only evaluates the steady-state operating efficiency under full load but also other states of the system such as cold standby or service intervals. It is shown that for a full system operation assessment and further system concept development the annual performance is of much higher importance than the steady-state system efficiency which is usually referred to. In a final step load profiles are defined and the annual performance is calculated for a specific system configuration. Using this example different operation strategies are compared.

Power-to-Gas technologies offer a promising approach for converting renewable electricity into a molecular form (fuel) to serve the energy demands of non-electric energy applications in all end-use sectors. The technologies have been broadly developed and are at the edge of a mass roll-out. The barriers that Power-to-Gas faces are no longer technical but are foremost regulatory and economic. This study focuses on a Power-to-Gas pathway where electricity is first converted in a water electrolyzer into hydrogen which is then synthetized with carbon dioxide to produce synthetic natural gas. A key aspect of this pathway is that an intermittent electricity supply could be used which could reduce the amount of electricity curtailment from renewable energy generation. Interim storages would then be necessary to decouple the synthesized part from hydrogen production to enable (I) longer continuous operation cycles for the methanation reactor and (II) increased annual full-load hours leading to an overall reduction in gas production costs. This work optimizes a Power-to-Gas plant configuration with respect to the cost benefits using a Monte Carlo-based simulation tool. The results indicate potential cost reductions of up to 17% in synthetic natural gas production by implementing well-balanced components and interim storages. This study also evaluates three different power sources which differ greatly in their optimal system configuration. Results from time-resolved simulations and sensitivity analyses for different plant designs and electricity sources are discussed with respect to technical and economic implications so as to facilitate a plant design process for decision makers.

The world is facing a challenge in meeting its needs for energy. Global energy consumption in the last half-century has increased very rapidly and is expected to continue to grow over the next 50 years. However it is expected to see significant differences between the last 50 years and the next. This paper aims at introducing a good solution to replace or work with conventional marine power plants. This includes the use of fuel cell power plant operated with hydrogen produced through water electrolysis or hydrogen produced from natural gas gasoline or diesel fuels through steam reforming processes to mitigate air pollution from ships.

The policy module of the FCHO presents an overview of EU and national policies across various hydrogen and fuel cell related sectors. It provides a snapshot of the current state of hydrogen legislation and policy. Scope: While FCHO covers 38 entities around the world due to the completeness of the data at the moment of writing this report covers 29 entities. The report reflects data collected January 2019 – December 2019. Key Findings: Hydrogen policies are relatively commonplace among European countries but with large differences between member states. EU hydrogen leaders do not lag behind global outliers such as South Korea or Japan.

The Hydrogen Incidents and Accidents Database (HIAD) is an international open communication platform collecting systematic data on hydrogen-related undesired incidents which was initially developed in the frame of HySafe an EC co-funded Network of Excellence in the 6th Frame Work Programme by the Joint Research Centre of the European Commission (EC-JRC). It was updated by JRC as HIAD 2.01 in 2016 with the support of the Fuel Cells and Hydrogen 2 Joint Undertaking (FCH 2 JU). Since the launch of the European Hydrogen Safety Panel2 (EHSP) initiative in 2017 by FCH 2 JU the EHSP has worked closely with JRC to upload additional/new incidents to HIAD 2.0 and analyze them to gather statistics lessons learnt and recommendations through Task Force 3. The first report to summarise the findings of the analysis was published by FCH 2 JU in September 2019. Since the publication of the first report the EHSP and JRC have continuously worked together to enlarge HIAD 2.0 by adding newly occurred incidents as well as quality historic incidents which were not previously uploaded to HIAD 2.0. This has facilitated the number of validated incidents in HIAD 2.0 to increase from 272 in 2018 to 593 in March 2021. This number is also dynamic and continues to increase as new incidents are being continuously added by both EHSP and JRC; and validated by JRC. The overall quality of the published incidents has also been improved whenever possible. For example additional information has been added to some existing incidents. Since mid-2020 EHSP Task Force TF3 has further analysed the 485 events which were in the database as of July 2020. For completeness of the statistics these include the events considered in our first report3 as well as the newly added/validated events since then. In this process the EHSP has also re-visited the lessons learnt in the first report to harmonise the approaches of analysis and improve the overall analysis. The analysis has comprehensively covered statistics lessons learnt and recommendations. The increased number of incidents has also made it viable to extract statistics from the available incidents at the time of the analysis including previously available incidents. It should be noted that some incidents reported is of low quality therefore it was not included in the statistical analysis.

Hungary’s National Hydrogen Strategy (hereinafter referred to as: Strategy) is ambitious but provides a realistic vision of the future as it opens the way for the establishment of a hydrogen economy therefore contributing to the achievement of decarbonisation goals and providing an opportunity for Hungary to become an active participant of the European hydrogen sector. On the long term the Strategy focuses on “green” hydrogen but in addition to hydrogen based on electricity generated using renewable resources primarily solar energy Hungary does not ignore opportunities for hydrogen production based on carbon-free energy accessed either through a nuclear basis or from the network. Additionally in the short and medium term a rapid reduction in emissions and the establishment of a viable hydrogen market will also require low-carbon hydrogen.

Fuel cell electric vehicles arise as an alternative to conventional vehicles in the road transport sector. They could contribute to decarbonising the transport system because they have no direct CO₂ emissions during the use phase. In fact the life-cycle environmental performance of hydrogen as a transportation fuel focuses on its production. In this sense through the case study of Spain this article prospectively assesses the techno-economic and environmental performance of a national hydrogen production mix by following a methodological framework based on energy systems modelling enriched with endogenous carbon footprint indicators. Taking into account the need for a hydrogen economy based on clean options alternative scenarios characterised by carbon footprint restrictions with respect to a fossil-based scenario dominated by steam methane reforming are evaluated. In these scenarios the steam reforming of natural gas still arises as the key hydrogen production technology in the short term whereas water electrolysis is the main technology in the medium and long term. Furthermore in scenarios with very restrictive carbon footprint limits biomass gasification also appears as a key hydrogen production technology in the long term. In the alternative scenarios assessed the functional substitution of hydrogen for conventional fossil fuels in the road transport sector could lead to high greenhouse gas emission savings ranging from 36 to 58 Mt CO₂ eq in 2050. Overall these findings and the model structure and characterisation developed for the assessment of hydrogen energy scenarios are expected to be relevant not only to the specific case study of Spain but also to analysts and decision-makers in a large number of countries facing similar concerns.

Ammonia has been proposed as a potential energy storage medium in the transition towards a low-carbon economy. This paper details experimental results and numerical calculations obtained to progress towards optimisation of fuel injection and fluidic stabilisation in swirl burners with ammonia as the primary fuel. A generic tangential swirl burner has been employed to determine flame stability and emissions produced at different equivalence ratios using ammonia–methane blends. Experiments were performed under atmospheric and medium pressurised conditions using gas analysis and chemiluminescence to quantify emission concentrations and OH production zones respectively. Numerical calculations using GASEQ and CHEMKIN-PRO were performed to complement compare with and extend experimental findings hence improving understanding concerning the evolution of species when fuelling on ammonia blends. It is concluded that a fully premixed injection strategy is not appropriate for optimised ammonia combustion and that high flame instabilities can be produced at medium swirl numbers hence necessitating lower swirl and a different injection strategy for optimised power generation utilising ammonia fuel blends.