Publications

The realization of a carbon-neutral civilization which has been set as a goal for the coming decades goes directly hand-in-hand with the need for an energy system based on renewable energies (REs). Due to the strong weather-related daily and seasonal fluctuations in supply of REs suitable energy storage devices must be included for such energy systems. For this purpose an energy system model featuring hybrid energy storage consisting of a hydrogen unit (for long-term storage) and a lithium-ion storage device (for short-term storage) was developed. With a proper design such a system can ensure a year-round energy supply by using electricity generated by photovoltaics (PVs). In the energy system that was investigated hydrogen (H2) was produced by using an electrolyser (ELY) with a PV surplus during the summer months and then stored in an H2 tank. During the winter due to the lack of PV power the H2 is converted back into electricity and heat by a fuel cell (FC). While the components of such a system are expensive a resource- and cost-efficient layout is important. For this purpose a Matlab/Simulink model that enabled an energy balance analysis and a component lifetime forecast was developed. With this model the results of extensive parameter studies allowed an optimized system layout to be created for specific applications. The parameter studies covered different focal points. Several ELY and FC layouts different load characteristics different system scales different weather conditions and different load levels—especially in winter with variations in heating demand—were investigated.

The absence of contaminants in the hydrogen delivered at the hydrogen refuelling station is critical to ensure the length life of FCEV. Hydrogen quality has to be ensured according to the two international standards ISO 14687–2:2012 and ISO/DIS 19880-8. Amount fraction of contaminants from the two hydrogen production processes steam methane reforming and PEM water electrolyser is not clearly documented. Twenty five different hydrogen samples were taken and analysed for all contaminants listed in ISO 14687-2. The first results of hydrogen quality from production processes: PEM water electrolysis with TSA and SMR with PSA are presented. The results on more than 16 different plants or occasions demonstrated that in all cases the 13 compounds listed in ISO 14687 were below the threshold of the international standards. Several contaminated hydrogen samples demonstrated the needs for validated and standardised sampling system and procedure. The results validated the probability of contaminants presence proposed in ISO/DIS 19880-8. It will support the implementation of ISO/ DIS 19880-8 and the development of hydrogen quality control monitoring plan. It is recommended to extend the study to other production method (i.e. alkaline electrolysis) the HRS supply chain (i.e. compressor) to support the technology growth.

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

Hydrogen has received substantial attention because of its diverse application in the energy sector. Steam methane reforming (SMR) dominates the current hydrogen production and is the least expensive endothermic reaction to produce grey hydrogen. This technology provides the advantages of low cost and high energy efficiency; however it emits an enormous amount of CO2. Carbon capture storage (CCS) technology helps reduce these emissions by 47% to 53% producing blue hydrogen. Methane pyrolysis is an alternative to SMR that produces (ideally) CO2-free turquoise hydrogen. In practice methane pyrolysis reduces CO2 emissions by 71% compared to grey hydrogen and 46% compared to blue hydrogen. While carbon dioxide emissions decrease with CCS fugitive methane emissions (FMEs) for blue and turquoise hydrogen are higher than those for grey hydrogen because of the increased use of natural gas to power carbon capture. We undertake FMEs of 3.6% of natural gas consumption for individual processes. In this study we also explore the utilization of biogas as a feedstock and additional Boudouard reactions for efficient utilization of solid carbon from methane pyrolysis and carbon dioxide from biogas. The present study focuses on possible ways to reduce overall emissions from turquoise hydrogen to provide solutions for a sustainable low-CO2 energy source.

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

Hydrogen energy storage (HES) systems have recently received attention due to their potential to support real-time power balancing in a power grid. This paper proposes a data-driven model predictive control (MPC) strategy for HES systems in coordination with distributed generators (DGs) in an islanded microgrid (MG). In the proposed strategy a data-driven model of the HES system is developed to reflect interactive operations of an electrolyzer hydrogen tank and fuel cell and hence the optimal power sharing with DGs is achieved to support real-time grid frequency regulation (FR). The MG-level controller cooperates with a device-level controller of the HES system that overrides the FR support based on the level of hydrogen. Small-signal analysis is used to evaluate the contribution of FR support. Simulation case studies are also carried out to verify the accuracy of the data-driven model and the proposed strategy is effective for improving the real-time MG frequency regulation compared with the conventional PI-based strategy.

This study presents a comprehensive methodology to evaluate plants that integrate renewable energy sources and hydrogen generation devices. The paper focuses on presenting the methods for devices’ operation assessment taking into account the annual operation. Multiple effectiveness indices have been presented. On the basis of experimental investigation with the hydrogen generator the methods for assessing its operation during start-up phase and sudden change in the supply current were proposed. The results of the experiments and the provided mathematical models show that dynamics of the hydrogen generator should be taken into account when selecting the suitable device for cooperation with variable renewable energy. It is especially important for multiple start-ups throughout the day due to significant differences in the amount of hydrogen produced by devices characterized by the same efficiency yet various time constants. Methodology for selecting the optimal nominal power for hydrogen generator to cooperate with given renewable sources was developed. It was proven the optimal power depends on the type of the renewable source and minimal load of the hydrogen generator. Several case studies including the integration of wind and solar energy farms to yield a 10 MW renewable energy farm were considered and the minimal load of the hydrogen generator impacts the annual operation of the device has been presented. The paper provides a set of tools to contribute to the development of sustainable energy plants. The methods proposed in this paper are universal and can be used for various renewable energy sources.

The EU’s hydrogen strategy consists of studying the potential for renewable hydrogen to help decarbonize the EU in a cost-effective way. Today hydrogen accounts for less than 2% of Europe’s energy consumption. It is primarily used to produce chemical products. However 96% of this hydrogen production is through natural gas leading to significant amounts of CO2 emissions. In this paper we investigated PV electrolysis H2 gas (noted H2(g)) production for mapping this resource at Europe’s scale. The Cordex/Copernicus RCPs scenarios allow for evaluating the impact of climate changes on the H2 -produced mass and the equivalent energy according to both extreme RCPs scenarios. New linear regressions are investigated to study the great dependence in H2(g) produced masses (kg·yr−1 ) and equivalent energies (MWh·yr−1 ) for European countries. Computational scenarios are investigated from a reference year (2005) to the end of the century (2100) by steps of 5 years. According to RCPs 2.6 (favorable)/8.5 (extreme) 31.7% and 77.4% of Europe’s area presents a decrease of H2(g)-produced masses between 2005 and 2100. For the unfavorable scenario (8.5) only a few regions located in the northeast of France Germany Austria Romania Bulgaria and Greece present a positive balance in H2(g) production for supplying remote houses or smart grids in electricity and heat energy.

This study analyzes the optimal sizing design of a stand-alone solar hydrogen hybrid energy system for a house in Afyon Turkey. The house is not connected to the grid and the proposed hybrid system meets all its energy demands; therefore it is considered a zero-energy building. The designed system guarantees uninterrupted and reliable power throughout the year. Since the reliability of the power supply is crucial for the house optimal sizing of the components photovoltaic (PV) panels electrolyzer storage tank and fuel cell stack is critical. Determining the sufficient number of PV panels suitable electrolyzer model and size number of fuel cell stacks and the minimum storage tank volume to use in the proposed system can guarantee an uninterrupted energy supply to the house. In this study a stand-alone hybrid energy system is proposed. The system consists of PV panels a proton exchange membrane (PEM) electrolyzer a storage tank and a PEM fuel cell stack. It can meet the continuous energy demand of the house is sized by using 10 min of averaged solar irradiation and temperature data of the site and consumption data of the house. Present results show that the size of each component in a solar hydrogen hybrid energy system in terms of power depends on the size of each other components to meet the efficiency requirement of the whole system. Choosing the nominal electrolyzer power is critical in such energy systems

Carbon neutrality (or climate neutrality) has been a global consensus and international experience exchange is essential. Given the differences in the degree of social development resource endowment and technological level each country should build a carbon-neutral plan based on its national conditions. Compared with other major developed countries (e.g. Germany the United States and Japan) China's carbon neutrality has much bigger challenges including a heavy and time-pressured carbon reduction task and the current energy structure that is over-dependent on fossil fuels. Here we provide a comprehensive review of the status and prospects of the key technologies for low-carbon near-zero carbon and negative carbon emissions. Technological innovations associated with coal oil-gas and hydrogen industries and their future potential in reducing carbon emissions are particularly explained and assessed. Based on integrated analysis of international experience from the world's major developed countries in-depth knowledge of the current and future technologies and China's energy and ecological resources potential five lessons for the implementation of China's carbon neutrality are proposed: (1) transformation of energy production pattern from a coal-dominated pattern to a diversified renewable energy pattern; (2) renewable power-to-X and large-scale underground energy storage; (3) integration of green hydrogen production storage transport and utilization; (4) construction of clean energy systems based on smart sector coupling (ENSYSCO); (5) improvement of ecosystem carbon sinks both in nationwide forest land and potential desert in Northwest China. This paper provides an international perspective for a better understanding of the challenges and opportunities of carbon neutrality in China and can serve as a theoretical foundation for medium-long term carbon neutral policy formulation.

The use of hydrogen exists in various sectors in Poland and Germany. Hydrogen can be used in industry transport decarbonisation of the Polish steel industry and as one of the low-emission alternatives to the existing coal applications in this sector. Limiting climate change requires efforts on a global scale from all countries of the world. Significant economic benefits will be realized by stimulating the development of new technologies to deal with climate change. The scenarios show an increasing demand for industrial hydrogen in the future. The key is to replace gray hydrogen with green and to convert industrial processes which will create additional hydrogen demand. The condition for the development of a green hydrogen economy is access to adequate installed capacity in renewable energy. Germany will become the leading market in the era of energy transformation in the coming years. The implementation of the hydrogen assumptions in Poland is possible to a greater extent by the efforts of entrepreneurs

To reduce greenhouse gases and air pollutants new technologies are emerging to reduce fossil fuel usage and to adopt more renewable energy sources. As the major aspects of fuel consumption power generation transportation and industrial applications have been given significant attention. The past few decades witnessed astonishing technological advancement in these energy sectors. In contrast the residential sector has had relatively little attention despite its significant utilization of fuels for a much longer period. However almost every energy transition in human history was initiated by the residential sector. For example the transition from fuelwood to cheap coal in the 1700s first took place in residential houses due to urbanization and industrialization. The present review demonstrates the energy transitions in the residential sector during the past two centuries while portending an upcoming energy transition and future energy structure for the residential sector. The feasibility of the 100% electrification of residential buildings is discussed based on current residential appliance adoption and the analysis indicates a hybrid residential energy structure is preferred over depending on a single energy source. Technical considerations and suggestions are given to help incorporate more renewable energy into the residential fuel supply system. Finally it is observed that compared to the numerous regulations on large energy-consumption aspects standards for residential appliances are scarce. Therefore it is concluded that establishing appropriate testing methods is a critical enabling step to facilitate the adoption of renewable fuels in future appliances.

Due to its high efficiency and reduced emissions new zero-emission hybrid electric vehicles have been selected as an attractive challenge for future transport applications. New zero -emission hybrid electric on the other hand has some major drawbacks from the complicated charging process. The hybrid electrical fuel cell system is introduced as the main source to intelligently control multi-source activities. An ultra-capacitor system is selected as the energy recovery assistance to monitor the fuel cell’s fast transient and peak power during critical periods. To regulate energy demand and supply an intelligent energy management system is proposed and tested through several constraints. The proposed approach system aims to act quickly against sudden circumstances related to hydrogen depletion in the prediction of the required fuel consumption basis. The proposed strategy tends to define the proper operating system according to energy demand and supply. The obtained results show that the designed system meets the targets set for the energy management unit by referring to an experimental velocity database.

In this work the performance of anion exchange membrane (AEM) electrolysis is evaluated. A parametric study is conducted focusing on the effects of various operating parameters on the AEM efficiency. The following parameters—potassium hydroxide (KOH electrolyte concentration (0.5–2.0 M) electrolyte flow rate (1–9 mL/min) and operating temperature (30–60 ◦C)—were varied to understand their relationship to AEM performance. The performance of the electrolysis unit is measured by its hydrogen production and energy efficiency using the AEM electrolysis unit. Based on the findings the operating parameters greatly influence the performance of AEM electrolysis. The highest hydrogen production was achieved with the operational parameters of 2.0 M electrolyte concentration 60 ◦C operating temperature and 9 mL/min electrolyte flow at 2.38 V applied voltage. Hydrogen production of 61.13 mL/min was achieved with an energy consumption of 48.25 kW·h/kg and an energy efficiency of 69.64%.

Hydrogen (H2) is expected to play a crucial role in reducing greenhouse gas emissions. However hydrogen losses to the atmosphere impact atmospheric chemistry including positive feedback on methane (CH4) the second most important greenhouse gas. Here we investigate through a minimalist model the response of atmospheric methane to fossil fuel displacement by hydrogen. We find that CH4 concentration may increase or decrease depending on the amount of hydrogen lost to the atmosphere and the methane emissions associated with hydrogen production. Green H2 can mitigate atmospheric methane if hydrogen losses throughout the value chain are below 9 ± 3%. Blue H2 can reduce methane emissions only if methane losses are below 1%. We address and discuss the main uncertainties in our results and the implications for the decarbonization of the energy sector.

The establishment of near-autonomous micro-grids in commercial or public building complexes is gaining increasing popularity. Short-term storage capacity is provided by means of large battery installations or more often by the employees’ increasing use of electric vehicle batteries which are allowed to operate in bi-directional charging mode. In addition to the above short-term storage means a long-term storage medium is considered essential to the optimal operation of the building’s micro-grid. The most promising long-term energy storage carrier is hydrogen which is produced by standard electrolyzer units by exploiting the surplus electricity produced by photovoltaic installation due to the seasonal or weekly variation in a building’s electricity consumption. To this end a novel concept is studied in this paper. The details of the proposed concept are described in the context of a nearly Zero Energy Building (nZEB) and the associated micro-grid. The hydrogen produced is stored in a high-pressure tank to be used occasionally as fuel in an advanced technology hydrogen spark ignition engine which moves a synchronous generator. A size optimization study is carried out to determine the genset’s rating the electrolyzer units’ capacity and the tilt angle of the rooftop’s photovoltaic panels which minimize the building’s interaction with the external grid. The hydrogen-fueled genset engine is optimally sized to 40 kW (0.18 kW/kWp PV). The optimal tilt angle of the rooftop PV panels is 39◦ . The maximum capacity of the electrolyzer units is optimized to 72 kW (0.33 kWmax/kWp PV). The resulting system is tacitly assumed to integrate to an external hydrogen network to make up for the expected mismatches between hydrogen production and consumption. The significance of technology in addressing the current challenges in the field of energy storage and micro-grid optimization is discussed with an emphasis on its potential benefits. Moreover areas for further research are highlighted aiming to further advance sustainable energy solutions.

The water-gas shift reaction (WGSR) is an intermediate reaction in hydrocarbon reforming processes considered one of the most important reactions for hydrogen production. Here water and carbon monoxide molecules react to generate hydrogen and carbon dioxide. From the thermodynamics aspect pressure does not have an impact whereas low-temperature conditions are suitable for high hydrogen selectivity because of the exothermic nature of the WGSR reaction. The performance of this reaction can be greatly enhanced in the presence of suitable catalysts. The WGSR has been widely studied due do the industrial significance resulting in a good volume of open literature on reactor design and catalyst development. A number of review articles are also available on the fundamental aspects of the reaction including thermodynamic analysis reaction condition optimization catalyst design and deactivation studies. Over the past few decades there has been an exceptional development of the catalyst characterization techniques such as near-ambient x-ray photoelectron spectroscopy (NA-XPS) and in situ transmission electron microscopy (in situ TEM) providing atomic level information in presence of gases at elevated temperatures. These tools have been crucial in providing nanoscale structural details and the dynamic changes during reaction conditions which were not available before. The present review is an attempt to gather the recent progress particularly in the past decade on the catalysts for low-temperature WGSR and their structural properties leading to new insights that can be used in the future for effective catalyst design. For the ease of reading the article is divided into subsections based on metals (noble and transition metal) oxide supports and carbon-based supports. It also aims at providing a brief overview of the reaction conditions by including a table of catalysts with synthesis methods reaction conditions and key observations for a quick reference. Based on our study of literature on noble metal catalysts atomic Pt substituted Mn3O4 shows almost full CO conversion at 260 °C itself with zero methane formation. In the case of transition metals group the inclusion of Cu in catalytic system seems to influence the CO conversion significantly and in some cases with CO conversion improvement by 65% at 280 °C. Moreover mesoporous ceria as a catalyst support shows great potential with reports of full CO conversion at a low temperature of 175 °C.

The steel industry is among the highest carbon-emitting industrial sectors. Since the steel production process is already exhaustively optimized alternative routes are sought in order to increase carbon efficiency and reduce these emissions. During steel production three main carbon-containing off-gases are generated: blast furnace gas coke oven gas and basic oxygen furnace gas. In the present work the addition of renewable hydrogen by electrolysis to those steelworks off-gases is studied for the production of methane and methanol. Different case scenarios are investigated using AspenPlusTM flowsheet simulations which differ on the end-product the feedstock flowrates and on the production of power. Each case study is evaluated in terms of hydrogen and electrolysis requirements carbon conversion hydrogen consumption and product yields. The findings of this study showed that the electrolysis requirements surpass the energy content of the steelwork’s feedstock. However for the methanol synthesis cases substantial improvements can be achieved if recycling a significant amount of the residual hydrogen.

Among the many potential future energy sources hydrogen stands out as particularly promising. Because it is a green and renewable chemical process water electrolysis has earned much interest among the different hydrogen production techniques. Seawater is the most abundant source of water and the ideal and cheapest electrolyte. The first part of this review includes the description of the general theoretical concepts: chemical physical and electrochemical that stands on the basis of water electrolysis. Due to the rapid development of new electrode materials and cell technology research has focused on specific seawater electrolysis parameters: the cathodic evolution of hydrogen; the concurrent anodic evolution of oxygen and chlorine; specific seawater catalyst electrodes; and analytical methods to describe their catalytic activity and seawater electrolyzer efficiency. Once the specific objectives of seawater electrolysis have been established through the design and energy performance of the electrolyzer the study further describes the newest challenges that an accessible facility for the electrochemical production of hydrogen as fuel from seawater must respond to for sustainable development: capitalizing on known and emerging technologies; protecting the environment; utilizing green renewable energies as sources of electricity; and above all economic efficiency as a whole.

Especially the electrification of the industry sector is highly complex and challenging mainly due to process-specific requirements. In this context there are several industrial processes where the direct and indirect use of electricity is subject to technical restrictions. In order to achieve the national climate goals the fossil energy consumption remaining after the implementation of efficiency and sufficiency measures as well as direct electrification has to be substituted through hydrogen and synthetic gaseous liquid and solid hydrocarbons. As the main research object the role of synthetic fuels in industrial transformation paths is investigated and analyzed by combining individual greenhouse gas abatement measures within the Sector Model Industry. Sector Model Industry is an energy consumption model that performs discrete deterministic energy and emission dynamic calculations with a time horizon up to 2050 at macroeconomic level. The results indicate that the use of synthetic fuels can be expected with a high level of climate protection. The industrial CO2 target in the model makes it necessary to replace CO2 -intensive fossil with renewable fuels. The model uses a total of 163 TWh of synthetic fuels in the climate protection scenario and thus achieves an 88% decrease in CO2 emissions in 2050 compared to 1990. This means that the GHG abatement achieved in industry is within the range of the targeted CO2 mitigation of the overall system in Germany of between 80 and 95% in 2050 compared to 1990. Due to technical restrictions the model mainly uses synthetic methane instead of hydrogen (134 TWh). The results show that despite high costs synthetic fuels are crucial for defossilization as a fall back option in the industrial scenario considering high climate ambition. The scenario does not include hydrogen technologies for heat supply. Accordingly the climate protection scenario uses hydrogen only in the steel industry for the direct reduction of iron (21 TWh). 8 TWh of synthetic oil substitute the same amount of fossil oil in the climate protection scenario. A further analysis conducted on the basis of the model results shows that transformation in the energy system and the use of smart ideas concepts and technologies are a basic prerequisite for enabling the holistic defossilisation of industry. The findings in the research can contribute to the cost-efficient use of synthetic fuels in industry and thus serve as a basis for political decision making. Moreover the results may have a practical relevance not only serving as a solid comparison base for the outcome of other studies but also as input data for further simulation of energy system transformation paths.

The hydrogen compression cycle system recycles hydrogen compressed by a compressor at high pressure and stores it in a high-pressure container. Thermal stress is generated due to increase in the pressure and temperature of hydrogen in the hydrogen storage tank during the fast filing process. For the sake of safety it is of great practical significance to predict and control the temperature change in the tank. The hydrogen charging process in the storage tank of the hydrogen charging station was studied by experimentation and simulation. In this paper a Computational Fluid Dynamics (CFD) model for non-adiabatic real filling of a 50 MPa hydrogen cylinder was presented. In addition a shear stress transport (k-ω) model and real gas model were used in order to account for thermo-fluid dynamics during the filling of hydrogen storage tanks (50 MPa 343 L). Compared to the simulation results with the experimental data carried out under the same conditions the temperatures calculated from the simulated non-adiabatic condition results were lower (by 5.3%) than those from the theoretical adiabatic condition calculation. The theoretical calculation was based on the experimentally measured pressure value. The calculated simulation mass was 8.23% higher than the theoretical result. The results of this study will be very useful in future hydrogen energy research and hydrogen charging station developments.

Hydrogen energy leads us in an important direction in the development of clean energy and the comprehensive utilization of hydrogen energy is crucial for the low-carbon transformation of the power sector. In this paper the demand for hydrogen energy in various fields is predicted based on the support vector regression algorithm which can be converted into an equivalent electrical load when it is all produced from water electrolysis. Then the investment costs of power generators and hydrogen energy equipment are forecast considering uncertainty. Furthermore a planning model is established with the forecast data initial installed capacity and targets for carbon emission reduction as inputs and the installed capacity as well as share of various power supply and annual carbon emissions as outputs. Taking Gansu Province of China as an example the changes of power supply structure and carbon emissions under different scenarios are analysed. It can be found that hydrogen production through water electrolysis powered by renewable energy can reduce carbon emissions but will increase the demand for renewable energy generators. Appropriate planning of hydrogen storage can reduce the overall investment cost and promote a low carbon transition of the power system

At the heart of most Power-to-X (PtX) concepts is the utilization of renewable electricity to produce hydrogen through the electrolysis of water. This hydrogen can be used directly as a final energy carrier or it can be converted into for example methane synthesis gas liquid fuels electricity or chemicals. Technical demonstration and systems integration are of major importance for integrating PtX into energy systems. As of June 2020 a total of 220 PtX research and demonstration projects in Europe have either been realized completed or are currently being planned. The central aim of this review is to identify and assess relevant projects in terms of their year of commissioning location electricity and carbon dioxide sources applied technologies for electrolysis capacity type of hydrogen post-processing and the targeted field of application. The latter aspect has changed over the years. At first the targeted field of application was fuel production for example for hydrogen buses combined heat and power generation and subsequent injection into the natural gas grid. Today alongside fuel production industrial applications are also important. Synthetic gaseous fuels are the focus of fuel production while liquid fuel production is severely under-represented. Solid oxide electrolyzer cells (SOECs) represent a very small proportion of projects compared to polymer electrolyte membranes (PEMs) and alkaline electrolyzers. This is also reflected by the difference in installed capacities. While alkaline electrolyzers are installed with capacities between 50 and 5000 kW (2019/20) and PEM electrolyzers between 100 and 6000 kW SOECs have a capacity of 150 kW. France and Germany are undertaking the biggest efforts to develop PtX technologies compared to other European countries. On the whole however activities have progressed at a considerably faster rate than had been predicted just a couple of years ago.

Colombia a privileged country in terms of diversity availability of natural resources and geographical location has set a roadmap for hydrogen as part of the energy transition plan proposed in 2021. To reduce its emissions in the mid-term and foster its economy hydrogen production should be green and blue with specific targets set for 2030 for the hydrogen costs and produced quantities. This work compares the state-of-the-art production of blue and green hydrogen and how Colombia is doing in each pathway. A deeper analysis considers the advantages of Colombia’s natural resources the possible paths the government could follow and the feedstock’s geographical location for hydrogen production and transportation. Then one discusses what may be the next steps in terms of policies and developments to succeed in implementing the plan. Overall it is concluded that green hydrogen could be the faster more sustainable and more efficient method to implement in Colombia. However blue hydrogen could play an essential role if oil and gas companies assess the advantages of carbon dioxide utilization and promote its deployment.

In this Podcast David Ledesma discusses with Stephen Craen Visiting Research Fellow OIES the challenges facing the financing of future hydrogen projects as it is expected that a substantial amount of capital will need to be invested in green hydrogen production to meet the 2050 net zero targets. Based around an ‘Archetype’ world scale hydrogen export project where 1 GW solar power is used to make green hydrogen which is converted to 250000 tpa green ammonia for export with a capital cost in the region of USD 2 billion the podcast discusses how ‘efficient financing’ can make an important contribution to minimising cost and making projects cost competitive. Stephen Craen argues that lenders and investors will look to precedents when assessing the nascent green hydrogen sector and the foremost will be LNG and offshore wind which both represent large-scale technically complex projects. Commercial structures of the green hydrogen business are expected to borrow concepts from offshore wind projects particularly in relation to price but also from LNG where this is relevant such as take-or-pay contracts. In this podcast we discuss the key issues that will need to be addressed to make a green hydrogen export project bankable concluding that commercial debt from either commercial banks or project bonds can help create competition.

The podcast can be found on their website.

Renewable energy (solar and wind) sources have evolved dramatically in recent years around the globe primarily because they have the potential to generate environmentally friendly energy. However operating systems with high renewable energy penetration remain challenging due to the stochastic nature of these energy sources. To tackle these problems the authors propose a state machine-based energy management strategy combined with a hysteresis band control strategy for renewable energy hybrid microgrids that integrates hydrogen storage systems. By considering the power difference between the renewable energy source and the demand the battery’s state of charge and the hydrogen storage level the proposed energy management strategy can control the power of fuel cells electrolyzers and batteries in a microgrid and the power imported into/exported from the main grid. The results showed that the energy management strategy provides the following advantages: (1) the power supply and demand balance in the microgrid was balanced (2) the lifespans of the electrolyzer and fuel cell were extended and (3) the state of charge of the battery and the stored level of the hydrogen were appropriately ensured.

Authored by the Hydrogen Council in collaboration with McKinsey and Company Global Hydrogen Flows addresses the midstream challenge of aligning and optimizing global supply and demand. It finds that trade can reduce overall system costs.

In doing so it provides a perspective on how the global trade of hydrogen and derivatives including hydrogen carriers ammonia methanol synthetic kerosene and green steel (which uses hydrogen in its production) can develop as well as the investments needed to unlock the full potential of global hydrogen and derivatives trade.

Our hope is that this report offers stakeholders – suppliers buyers original equipment manufacturers (OEMs) investors and governments – a thorough and quantitative perspective that will help them make the decisions required to accelerate the uptake of hydrogen.

Key messages from the report:

Hydrogen and its derivatives will become heavily traded: 400 out of the 660 million tons (MT) of hydrogen needed for carbon neutrality by 2050 will be transported over long distances with 190 MT crossing international borders.

In a cost-optimal world around 50% of trade uses pipelines while synthetic fuels ammonia and sponge iron transported on ships account for approximately 45%. Europe and countries in the Far East will rely on imports while North America and China are mostly self-reliant.

Trade has huge benefits: It can lower the cost of hydrogen supply by 25% or as much as US$6 trillion of investments from now until 2050. This will accelerate the hydrogen transition which can abate 80 gigatons of CO2 until 2050.

The paper can be found on their website.

Hydrogen as a suitable and clean energy carrier has been long considered a primary fuel or in combination with other conventional fuels such as gasoline and diesel. Since the density of hydrogen is very low in port fuel-injection configuration the engine’s volumetric efficiency reduces due to the replacement of hydrogen by intake air. Therefore hydrogen direct in-cylinder injection (injection after the intake valve closes) can be a suitable solution for hydrogen utilization in spark ignition (SI) engines. In this study the effects of hydrogen direct injection with different hydrogen energy shares (HES) on the performance and emissions characteristics of a gasoline port-injection SI engine are investigated based on reactive computational fluid dynamics. Three different injection timings of hydrogen together with five different HES are applied at low and full load on a hydrogen– gasoline dual-fuel SI engine. The results show that retarded hydrogen injection timing increases the concentration of hydrogen near the spark plug resulting in areas with higher average temperatures which led to NOX emission deterioration at −120 Crank angle degree After Top Dead Center (CAD aTDC) start of injection (SOI) compared to the other modes. At −120 CAD aTDC SOI for 50% HES the amount of NOX was 26% higher than −140 CAD aTDC SOI. In the meanwhile an advanced hydrogen injection timing formed a homogeneous mixture of hydrogen which decreased the HC and soot concentration so that −140 CAD aTDC SOI implied the lowest amount of HC and soot. Moreover with the increase in the amount of HES the concentrations of CO CO2 and soot were reduced. Having the HES by 50% at −140 CAD aTDC SOI the concentrations of particulate matter (PM) CO and CO2 were reduced by 96.3% 90% and 46% respectively. However due to more complete combustion and an elevated combustion average temperature the amount of NOX emission increased drastically.

Dynamically-operated water electrolyzers enable the production of green hydrogen for cross-sector applications while simultaneously stabilizing power grids. In this study the start-up phase of polymer electrolyte membrane (PEM) water electrolyzers is investigated in the context of intermittent renewable energy sources. During the start-up of the electrolysis system the temperature increases which directly influences hydrogen production efficiency. Experiments on a 100 kWel electrolyzer combined with simulations of electrolyzers with up to 1 MWel were used to analyze the start-up phase and assess its implications for operators and system designers. It is shown that part-load start-up at intermediate cell voltages of 1.80 V yields the highest efficiencies of 74.0 %LHV compared to heat-up using resistive electrical heating elements which reaches maximum efficiencies of 60.9 %LHV. The results further indicate that large-scale electrolyzers with electrical heaters may serve as flexible sinks in electrical grids for durations of up to 15 min.

The development of hydropower industry is progressing rapidly in China and the installed capacity and power generation are increasing year by year. However due to factors such as transmission channels and power grid peaking capacity hydropower consumption in some areas is facing greater pressure. As an excellent medium for energy interconnection hydrogen energy can play an important role in promoting hydropower consumption. This paper introduces the current status and trends of hydrogen energy development in major developed countries and China and analyzes the current status of China’s hydropower abandoned water. Based on the production of hydrogen using surplus hydropower in the Dadu River Basin in Sichuan an integrated energy network research plan including hydropower electrolytic hydrogen production storage and transportation hydrogen refueling and hydrogen-powered vehicles is proposed. At the same time the development concept of hydrogen energy industry including hydrogen energy source economy hydrogen energy industry ecosphere and hydrogen energy sky road in western Sichuan is also proposed.

The freight sector is expected to keep or even increase its fundamental role for the major modern economies and therefore actions to limit the growing pressure on the environment are urgent. The use of electricity is a major option for the decarbonization of transports; in the heavy-duty segment it can be implemented in different ways: besides full electric-battery powertrains electricity can be used to supply catenary roads or can be chemically stored in liquid or gaseous fuels (e-fuels). While the current EU legislation adopts a tailpipe Tank-To-Wheels approach which results in zero emissions for all direct uses of electricity a Well-To-Wheels (WTW) method would allow accounting for the potential benefits of using sustainable fuels such as e-fuels. In this article we have performed a WTW-based comparison and modelling of the options for using electricity to supply heavy-duty vehicles: e-fuels eLNG eDiesel and liquid Hydrogen. Results showed that the direct use of electricity can provide high Greenhouse Gas (GHG) savings and also in the case of the e-fuels when low-carbonintensity electricity is used for their production. While most studies exclusively focus on absolute GHG savings potential considerations of the need for new infrastructures and the technological maturity of some options are fundamental to compare the different technologies. In this paper an assessment of such technological and non-technological barriers has been conducted in order to compare alternative pathways for the heavy-duty sector. Among the available options the flexibility of using drop-in energy-dense liquid fuels represents a clear and substantial immediate advantage for decarbonization. Additionally the novel approach adopted in this paper allows us to quantify the potential benefits of using e-fuels as chemical storage able to accumulate electricity from the production peaks of variable renewable energies which would otherwise be wasted due to grid limitations.

The increasing penetration of renewable and distributed resources signals a global boom in energy transition but traditional grid utilities have yet to share in much of the triumph at the current stage. Higher grid management costs lower electricity prices fewer customers and other challenges have emerged along the path toward renewable energy but many more opportunities await to be seized. Most importantly there are insufficient studies on how grid utilities can thrive within the hydrogen economy. Through a case study on the State Grid Corporation of China we identify the strengths weaknesses opportunities and threats (SWOT) of grid utilities within the hydrogen economy. Based on these factors we recommend that grids integrate hydrogen into the energy-as-a-service model and deliver it to industrial customers who are under decarbonization pressure. We also recommend that grid utilities fund a joint venture with pipeline companies to optimize electricity and hydrogen transmissions simultaneously.

Ammonia can be stored as a liquid under relatively easy conditions (Ambient temperature by applying 10 bar or Ambient pressure with the temperature of 239 K). At the same time liquid ammonia has a high hydrogen storage density and is therefore a particularly promising carrier for hydrogen storage. At the same time the current large-scale industrial synthesis of ammonia has long been mature and in the future it will be possible to achieve a zero-emission ammonia regeneration cycle system by replacing existing energy sources with renewable ones. Ammonia does not contain carbon and its use in fuel cells can avoid NOx production during energy release. high temperature solid oxide fuel cells can be directly fueled by ammonia and obtain good output characteristics but the challenges inherent in high temperature solid oxide fuel cells greatly limit the implementation of this option. Whereas PEMFC has gained initial commercial use however for PEMFC ammonia is a toxic gas so the general practice is to convert ammonia to pure hydrogen. Ammonia to hydrogen requires decomposition under high temperature and purification which increases the complexity of the fuel system. In contrast PEMFC that can use ammonia decomposition gas directly can simplify the fuel system and this option has already obtained preliminary experimental validation studies. The energy efficiency of the system obtained from the preliminary validation experiments is only 34–36% which is much lower than expected. Therefore this paper establishes a simulation model of PEMFC directly using ammonia decomposition gas as fuel to study the maximum efficiency of the system and the effect of the change of system parameters on the efficiency and the results show that the system efficiency can reach up to 45% under the condition of considering certain heat loss. Increasing the ammonia decomposition reaction temperature decreases the system efficiency but the effect is small and the system efficiency can reach 44% even at a temperature of 850°C. The results of the study can provide a reference for a more scientific and quantitative assessment of the potential value of direct ammonia decomposition gas-fueled PEMFC.

Simultaneous and interactive combustion of three fuels with differing reactivities is investigated by numerical simulations. In the present study conventional dual-fuel (DF) ignition phenomena relevant to DF compression ignition (CI) engines are extended and explored in tri-fuel (TF) context. In the present TF setup a low reactivity fuel (LRF) methane or methanol is perfectly mixed with hydrogen and air to form the primary fuel blend at the lean equivalence ratio of 0.5. Further such primary fuel blends are ignited by a high-reactivity fuel (HRF) here n-dodecane under conditions similar to HRF spray assisted ignition. Here ignition is relevant to the HRF containing parts of the tri-fuel mixtures while flame propagation is assumed to occur in the premixed LRF/ containing end gas regions. The role of hydrogen as TF mixture reactivity modulator is explored. Mixing is characterized by n-dodecane mixture fraction ξ and molar ratio . When x < 0.6 minor changes are observed for the first- and second-stage ignition delay time (IDT) of tri-fuel compared to dual-fuel blends (x = 0). For methane when x > 0.6 first- and second-stage IDT increase by factor 1.4–2. For methanol a respective decrease by factor 1.2–2 is reported. Such contrasting trends for the two LRFs are explained by reaction sensitivity analysis indicating the importance of OH radical production/consumption in the ignition process. Observations on LRF/ end gas laminar flame speed () indicate that  increases with x due to the highly diffusive features of . For methane  increase with x is more significant than for methanol.

In this fifth episode  Steffan Eldred and Neelam Mughal from Innovate UK KTN discuss how the glass industry is driving new hydrogen developments and research and explore the hydrogen transition opportunities and challenges in this sector alongside their special guest Rob Ireson Innovation and Partnerships Manager at Glass Futures Ltd.

The podcast can be found on their website

Ammonia plays a vital role in feeding the world through fertilizer production as well as having other industrial uses. However current ammonia production processes rely heavily on fossil fuels mostly natural gas to generate hydrogen as a feedstock. There is an urgent need to re-design and decarbonise the production process to reduce greenhouse emissions and avoid dependence on volatile gas markets and a depleting resource base. Renewable energy driven electrolysis to generate hydrogen provides a viable pathway for producing carbon-free or green ammonia. However a key challenge associated with producing green ammonia is managing low cost but highly variable wind and solar renewable energy generation for hydrogen electrolysis while maintaining reliable operation of the less flexible ammonia synthesis unit. To date green ammonia production has only been demonstrated at pilot scale and optimising plant configurations and scaling up production facilities is an urgent task. Existing feasibility studies have demonstrated the ability to model and cost green ammonia production pathways that can overcome the technical and economic challenges. However these existing approaches are context specific demonstrating the ability to model and cost green ammonia production for defined locations with set configurations. In this paper we present a modelling framework that consolidates the array of configurations previously studied into a single framework that can be tailored to the location of interest. Our open-source green ammonia modelling and costing tool dynamically simulates the integration of renewable energy with a wide range of balancing power and storage options to meet the flexible demands of the green ammonia production process at hourly time resolution over a year or more. Unlike existing models the open-source implementation of our tool allows it to be used by a potentially wide range of stakeholders to explore their own projects and help guide the upscaling of green ammonia as a pathway for decarbonisation. Using Gladstone in Australia as a case study a 1 million tonne per annum (MMTPA) green ammonia plant is modelled and costed using price assumptions for major equipment in 2030 provided by the Australian Energy Market Operator (AEMO). Using a hybrid (solar PV and wind) renewable energy source and Battery Energy Storage System as balancing technology we estimate a levelized cost of ammonia (LCOA) between 0.69 and 0.92 USD kgNH3 -1 . While greater than historical ammonia production costs from natural gas falling renewables costs and emission reduction imperatives suggest a major future role for green ammonia.

Under the requirements of China's strategic goal of "carbon peaking and carbon neutrality" as a renewable clean and efficient secondary energy source hydrogen benefits from abundant resources a wide variety of sources a high combustion calorific value clean and non-polluting various forms of utilization energy storage mediums and good security etc. It will become a realistic way to help energy transportation petrochemical and other fields to achieve deep decarbonization and will turn into an important replacement energy source for China to build a modern clean energy system. It is clear that accelerating the development of hydrogen energy has become a global consensus. In order to provide a theoretical support for the accelerated transformation of hydrogen-related industries and energy companies and provide a basis and reference for the construction of "Hydrogen Energy China" this paper describes main key technological progresses in the hydrogen industry chain such as hydrogen production storage transportation and application. The status and development trends of hydrogen industrialization are analyzed and then the challenges faced by the development of the hydrogen industry are discussed. At last the development and future of the hydrogen industry are prospected. The following conclusions are achieved. (1) Hydrogen technologies of our country will become mature and enter the road of industrialization. The whole industry chain system of the hydrogen industry is gradually being formed and will realize the leap-forward development from gray hydrogen blue hydrogen to green hydrogen. (2) The overall development of the entire hydrogen industry chain such as hydrogen production storage and transportation fuel cells hydrogen refueling stations and other scenarios should be accelerated. Besides in-depth integration and coordination with the oil and gas industry needs more attention which will rapidly promote the high-quality development of the hydrogen industry system. (3) The promotion and implementation of major projects such as "north-east hydrogen transmission" "west-east hydrogen transmission" "sea hydrogen landing" and utilization of infrastructures such as gas filling stations can give full play to the innate advantages of oil and gas companies in industrial chain nodes such as hydrogen production and refueling etc. which can help to achieve the application of "oil gas hydrogen and electricity" four-station joint construction form a nationwide hydrogen resource guarantee system and accelerate the planning and promotion of the "Hydrogen Energy China" strategy.

In Spain the institutional framework for photovoltaic energy production has experienced distinct stages. From 2007 to 2012 the feed-in-tariff system led to high annual growth rates of this renewable energy but after the suppression of the policy of public subsidies the sector stagnated. In recent years green hydrogen an innocuous gas in the atmosphere has become a driving force that stimulates photovoltaic energy production. Since 2020 encouraged by the European energy strategies and corresponding funds Spain has established a regulation to promote green hydrogen as a form of energy resource. Adopting the new institutional economics (NIE) approach this article investigates the process of changing incentives for the energy business sector and its impact on photovoltaic energy production. The results show an increase in the number of both projects approved or on approval and companies involved in green hydrogen that are planning to use photovoltaic energy in Spain thus engendering the creation of a new photovoltaic business environment based on innovation and sustainability.

In the future green hydrogen—hydrogen produced with renewable energy resources—could provide developing countries with a zero-carbon energy carrier to support national sustainable energy objectives and it needs further consideration by policy makers and investors. Developing countries with good renewable energy resources could produce green hydrogen locally generating economic opportunities and increasing energy security by reducing exposure to oil price volatility and supply disruptions. Support from development finance institutions and concessional funds could play an important role in deploying first-of-a-kind green hydrogen projects accelerating the uptake of green hydrogen in developing countries and increasing capacity and creating the necessary policy and regulatory enabling environment.

This paper compares six (6) alternatives for green hydrogen transport at sea. Two (2) alternatives of liquid hydrogen (LH2) by ship two (2) alternatives of compressed hydrogen (cH2) by ship and two (2) alternatives of hydrogen by pipeline. The ship alternatives study having hydrogen storage media at both end terminals to reduce the ships’ time at port or prescinding of them and reduce the immobilized capital. In the case of the pipeline new models are proposed by considering pressure costs. One scenario considers that there are compression stations every 500 km and the other one considers that there are none along the way. These alternatives are assessed under nine different scenarios that combine three distances: 100 km 2500 km and 5000 km; and three export rates of hydrogen 100 kt/y 1 Mt/y and 10 Mt/y. The results show including uncertainty bands that for the 100 km of distance the best alternative is the pipeline. For 2500 km and 100 kt/y the top alternative is cH2 shipping without storage facilities at the port terminals. For 2500 km and 1 Mt/y and for 5000 km and 100 kt/y the best alternatives are cH2 or LH2 shipping. For the remaining scenarios the best alternative is LH2 shipping.

This paper delves into the critical role of tax credits specifically Sections 45Q and 45V in the financing and economic feasibility of low-carbon-intensity hydrogen projects with a focus on natural-gas-based hydrogen production plants integrated with carbon capture and storage (CCS). This study covers the current clean energy landscape underscoring the importance of low-carbon hydrogen as a key component in the transition to a sustainable energy future and then explicates the mechanics of the 45Q and 45V tax credits illustrating their direct impact on enhancing the economic attractiveness of such projects through a detailed net present value (NPV) model analysis. Our analysis reveals that the application of 45Q and 45V tax credits significantly reduces the levelized cost of hydrogen production with scenarios indicating a reduction in cost ranging from USD 0.41/kg to USD 0.81/kg of hydrogen. Specifically the 45Q tax credit demonstrates a slightly more advantageous impact on reducing costs compared to the 45V tax credit underpinning the critical role of these fiscal measures in enhancing project returns and feasibility. Furthermore this paper addresses the inherent limitations of utilizing tax credits primarily the challenge posed by the mismatch between the scale of tax credits and the tax liability of the project developers. The concept and role of tax equity investments are discussed in response to this challenge. These findings contribute to the broader dialogue on the financing of sustainable energy projects providing valuable insights for policymakers investors and developers in the hydrogen energy sector. By quantifying the economic benefits of tax credits and elucidating the role of tax equity investments our research supports informed decision-making and strategic planning in the pursuit of a sustainable energy future.

A thermodynamic model was developed for combustion performance and emissions with a reference diesel fuel a 10 vol% methanol blend with 90 vol% diesel a 10 vol% ethanol with 90 vol% diesel and a 4% hydrogen fumigating in the inlet port along with diesel direct injection. The diesel and two alcohol blends (10% methanol–90% diesel and 10% ethanol–90% diesel) was directly injected into the cylinder while hydrogen was fumigated at the inlet port. The model was developed by commercial GT-Suite software. Besides engine performance exergy and energy rates were estimated for the four fuels. Among the four fuels/fuel blends hydrogen fuel (4% fumigated hydrogen) shows the best performance in terms of exergy energy rates specific fuel consumption power and greenhouse gas emissions. Regarding greenhouse gases carbon dioxide was only considered in this investigation as it contributes to a significant detrimental effect on environmental pollution.

This is a time of enormous change for the gas industry as the UK and the world at large attempts to meet the challenges of decarbonisation in the face of climate change. Hydrogen is expected to play a vital role in achieving the government’s commitment of eliminating the UK’s contribution to climate change by 2050 with the industry creating up to 8000 jobs by 2030 and potentially unlocking up to 100000 jobs by the middle of the century. But despite the UK government’s huge ambitions hydrogen is just one piece of the puzzle and it will be necessary to seek solutions that bring the whole energy system together – including not just heat for buildings but hard-to decarbonise areas such as manufacturing road transport aviation and shipping. Here we bring you just a taste of some of the amazing work taking place across the energy sector to understand this fuel more clearly to comprehend its strengths and limitations and to integrate it into our current energy infrastructure. We hope you enjoy this special publication.

DNV has carried out an investigation into potential uses for smart gas meter data as part of Phase 1 of the Modernising Energy Data Applications competition as funded by UK Research & Innovation. In particular a series of calculations have been carried out to investigate the possibility of differentiating accidental gas leaks from normal appliance use in domestic properties. This is primarily with the aim of preventing explosions but the detection of leaks also has environmental and financial benefits.

Three gases have been considered in this study:

• A representative UK natural gas composition.
• A blend of 80% natural gas and 20% hydrogen.
• Pure hydrogen.

An established method was used to calculate the gas outflow rate from leaks into buildings downstream of the meter regulator. These gas leak rates were compared with the gas use by typical domestic appliances and these leaks were considered in the context of the smart gas meter data that is currently available in 30-minute periods. A representative set of gas accumulation calculations was performed. It was found that the following three general cases apply to all three gases:

• Small holes of up to 1 mm rarely reach flammable gas/air concentrations for any gas except under the most unfavourable conditions such as small volumes combined with low ventilation rates. These releases would likely be detected within 6 to 12 hours.
• Medium holes between 1 mm and 6 mm give outflow rates equivalent to a moderate to high level of gas use by appliances. The ability to detect these leaks is highly dependent on the hole size the time at which the leak begins and the normal gas use profile in the building. The larger leaks in this category would be detected within 30 to 60 minutes while the smaller leaks could take several hours to be clearly differentiated from appliance use. This is quick enough to prevent some explosions.
• Large holes of over 6 mm give leak rates greater than any gas use by appliances. These releases rapidly reach a flammable gas/air mixture in most cases but would typically be detected within the first 30-minute meter output period. Again some explosions could be prevented in this timescale.

An event tree has been used to quantify the approximate success rate of detecting and preventing explosion events. Using the currently available 30-minute smart meter data and functionality it is estimated that around 7% of explosions could be prevented with a slight variation depending on the gas type in use. Additional functionality could be included in the meter to improve this performance. Typically one of the risk mitigation measures in isolation increases the explosion prevention rate to around 15%. If multiple improvements are made then the detection rate is predicted to increase to around 30%.

An examination of detailed historical incident information suggests that the explosions that lead to fatalities or significant damage to houses are typically of the type that would be more likely to be detected and prevented. It is estimated that between 25% and 75% of the more severe explosions could be prevented depending on which potential improvements are implemented.

Based on the conservative estimates of explosion prevention a cost benefit analysis suggests that it is justifiable to spend between around £1 and £10 per meter installed to implement the proposed technology. This is based purely on lives saved and does not take account of other benefits.

The present study seeks to select the most important articles and reviews from the Web of Science database that approached alternative fuels towards the decarbonization of the maritime sector. Through a systematic review methodology a combination of keywords and manual refining found a contribution of 103 works worldwide the European continent accounting for 57% of all publications. Twenty-two types of fuels were cited by the authors liquefied natural gas (LNG) hydrogen and biodiesel contributing to 49% of the mentions. Greenhouse gases sulfur oxide nitrogen oxide and particulate matter reductions are some of the main advantages of cleaner sources if used by the vessels. Nevertheless there is a lack of practical research on new standards engine performance cost and regulations from the academy to direct more stakeholders towards low carbon intensity in the shipping sector.

A series of more than 100 experiments with hydrogen-air mixtures at cryogenic temperatures have been performed in a shock tube in the frame of the PRESLHY project. A wide range of hydrogen concentrations from 8 to 60%H2 in the shock tube of the length of 5 m and 50 mm id was tested at cryogenic temperatures from 80 to 130K at ambient pressure. Flame propagation regimes were investigated for all hydrogen compositions in the shock tube at three different blockage ratios (BR) 0 0.3 and 0.6 as a function of initial temperature. Pressure sensors and InGaAs-photodiodes have been applied to monitor the flame and shock propagation velocity of the process. The experiments at ambient pressure and temperature were conducted as the reference data for cryogenic experiments. A critical expansion ratio for an effective flame acceleration to the speed of sound was experimentally found at cryogenic temperatures. The detonability criterion for smooth and obstructed channels was used to evaluate the detonation cell sizes at cryogenic temperatures as well. The main peculiarities of cryogenic combustion with respect to the safety assessment were that the maximum combustion pressure was several times higher compared to ambient temperature and the run-up-distance to detonation was several times shorter independent of lower chemical reactivity at cryogenic conditions.

A combined ultra-short-term wind power prediction strategy with high robustness based on least squares support vector machine (LSSVM) has been proposed in order to solve the wind abandonment caused by wind power randomness and realize efficient hydrogen production under wide power fluctuation. Firstly the original wind power data is decomposed into sub-modes with different bandwidth by variational modal decomposition (VMD) which reduces the influence of random noise and mode mixing significantly. Then dragonfly algorithm (DA) is introduced to optimize LSSVM kernel function and the combined ultra-short-term wind power prediction strategy which meets the time resolution and accuracy requirements of electrolytic cell control has been established finally. This model is validated by a wind power hydrogen production demonstration project output in the middle east of China. The superior prediction accuracy for high volatility wind power data is verified and the algorithm provides theoretical basis to improve the control of wind power hydrogen production system

With the rising threat of climate change green hydrogen is increasingly seen as the high-capacity energy storage and transport medium of the future. This creates an opportunity for low- and middle-income countries to leverage their high renewable energy potential to produce use and export low-cost green hydrogen creating environmental and economic development benefits. While identifying ideal locations for green hydrogen production is critical for countries when defining their green hydrogen strategies there has been a paucity of adequate geospatial planning approaches suitable to low- and middle-income countries. It is essential for these countries to identify green hydrogen production sites which match demand to expected use cases such that their strategies are economically sustainable. This paper therefore develops a novel geospatial cost modelling method to optimize the location of green hydrogen production across different use cases with a focus on suitability to low- and middle-income countries. This method is applied in Kenya to investigate the potential hydrogen supply chain for three use cases: ammonia-based fertilizer freight transport and export. We find hydrogen production costs of e3.7–9.9/kgH2 are currently achievable across Kenya depending on the production location chosen. The cheapest production locations are identified to the south and south-east of Lake Turkana. We show that ammonia produced in Kenya can be cost-competitive given the current energy crisis and that Kenya could export hydrogen to Rotterdam with costs of e7/kgH2 undercutting current market prices regardless of the carrier medium. With expected techno-economic improvements hydrogen production costs across Kenya could drop to e1.8–3.0/kgH2 by 2030.

Hydrogen addition can improve the performance and extend the lean burn limit of gasoline engines. Different hydrogen injection strategies lead to different types of hydrogen mixture distribution (HMD) which affects the engine performance. Therefore the present study experimentally investigated the effects of hydrogen injection strategy on the combustion and emissions of a hydrogen/gasoline dual-fuel port-injection engine under lean-burn conditions. Four different hydrogen injection strategies were explored: hydrogen direct injection (HDI) forming a stratified hydrogen mixture distribution (SHMD); hydrogen intake port injection forming a premixed hydrogen mixture distribution (PHMD); split hydrogen direct injection (SHDI) forming a partially premixed hydrogen mixture distribution (PPHMD); and no hydrogen addition (NHMD). The results showed that 20% hydrogen addition could extend the lean burn limit from 1.5 to 2.8. With the increase in the excess air ratio the optimum HMD changed from PPHMD to SHMD. The maximum brake thermal efficiency was obtained with an excess air ratio of 1.5 with PPHMD. The coefficient of variation (COV) with NHMD was higher than that with hydrogen addition since the hydrogen enhanced the stability of ignition and combustion. The engine presented the lowest emissions with PHMD. There were almost no carbon monoxide (CO) and nitrogen oxides (NOx) emissions when the excess air ratio was respectively more than 1.4 and 2.0.