Publications

DNV GL believes that the National Transmission System (NTS) will be central to the future of decarbonised energy in the UK. The future NTS could transmit natural gas hydrogen blends of the two and carbon dioxide. New pipelines will be built however a large cost-saving is available if the existing NTS assets can also be re-purposed. To move towards this future National Grid Gas Transmission wants to develop a project to trial injection hydrogen into the NTS. This is an opportunity to show that National Grid is part of the solution to achieving Net Zero. The trial will demonstrate to the Government and public that re-purposing the NTS is cost-effective safe and involves minimal disruption.

This report sets out a roadmap of projects to provide the knowledge needed for the trial. The roadmap was developed by assessing the knowledge required and how much of it already existed. The knowledge already available is summarised in this report with references to where further details can be found. Gaps in the knowledge are then described. The roadmap consists of projects to conduct work to close the knowledge gaps. The results are summarised in the figures below and in the box to the right.  

This report and any attachment is freely available on the ENA Smarter Networks Portal here. IGEM Members can download the report and any attachment directly by clicking on the pdf icon above.

This paper presents a simple hydrogen fuel cell vehicle (HFCV) energy consumption model. Simple fuel/energy consumption models have been developed and employed to estimate the energy and environmental impacts of various transportation projects for internal combustion engine vehicles (ICEVs) battery electric vehicles (BEVs) and hybrid electric vehicles (HEVs). However there are few published results on HFCV energy models that can be simply implemented in transportation applications. The proposed HFCV energy model computes instantaneous energy consumption utilizing instantaneous vehicle speed acceleration and roadway grade as input variables. The mode accurately estimates energy consumption generating errors of 0.86% and 2.17% relative to laboratory data for the fuel cell estimation and the total energy estimation respectively. Furthermore this work validated the proposed model against independent data and found that the new model accurately estimated the energy consumption producing an error of 1.9% and 1.0% relative to empirical data for the fuel cell and the total energy estimation respectively. The results demonstrate that transportation engineers policy makers automakers and environmental engineers can use the proposed model to evaluate the energy consumption effects of transportation projects and connected and automated vehicle (CAV) transportation applications within microscopic traffic simulation models.

High-pressure GH2 systems are of interest for storage and distribution of hydrogen. The dynamic blow-down process of a high-pressure GH2 reservoir in case of a small leak is a complex process involving a chain of distinct flow regimes and gas states which needs to be understood for safety investigations.<br/>This paper presents models to predict the hydrogen concentration and velocity field in the vicinity of a postulated small leak. An isentropic expansion model with a real gas equation of state for normal hydrogen is used to calculate the time dependent gas state in the reservoir and at the leak position. The subsequent gas expansion to 0.1 MPa is predicted with a zero-dimensional model. The gas conditions after expansion serve as input to a newly developed integral model for a round free turbulent H2-jet into ambient air. The model chain was evaluated by jet experiments with sonic hydrogen releases from different reservoir pressures and temperatures.<br/>Predictions are made for the blow-down of hydrogen reservoirs with 10 30 and 100 MPa initial pressure. The evolution of the pressure in the reservoir and of the H2 mass flux at the orifice are presented in dimensionless form which allows scaling to other system dimensions and initial gas conditions. Computed hydrogen concentrations and masses in the jet are given for the 100 MPa case. A normalized hydrogen concentration field in the free jet is presented which allows for a given leak scenario the prediction of the axial and radial range of burnable H2-air mixtures.

Hydrogen jet flames resulting from ignition of unintended releases can be extensive in length and pose significant radiation and impingement hazards. Depending on the leak diameter and source pressure the resulting consequence distances can be unacceptably large. One possible mitigation strategy to reduce exposure to jet flames is to incorporate barriers around hydrogen storage and delivery equipment. An experimental and modeling program has been performed at Sandia National Laboratories to better characterize the effectiveness of barrier walls to reduce hazards. This paper describes the experimental and modeling program and presents results obtained for various barrier configurations. The experimental measurements include flame deflection using standard and infrared video and high-speed movies (500 fps) to study initial flame propagation from the ignition source. Measurements of the ignition overpressure wall deflection radiative heat flux and wall and gas temperature were also made at strategic locations. The modeling effort includes three-dimensional calculations of jet flame deflection by the barriers computations of the thermal radiation field around barriers predicted overpressure from ignition and the computation of the concentration field from deflected unignited hydrogen releases. The various barrier designs are evaluated in terms of their mitigation effectiveness for the associated hazards present. The results show that barrier walls are effective at deflecting jet flames in a desired direction and can help attenuate the effects of ignition overpressure and flame radiative heat flux.

Low-carbon gases are indispensable to any energy system that is reliable clean affordable safe and is suited to spatial integration and zero-carbon hydrogen is a crucial link in that chain1. The most common element in the universe seems to have a highly bonding effect in the Netherlands – particularly as a result of the unique starting position of our country. This is made clear in the agreements of the National Climate Agreement which includes an ambitious target for hydrogen supported by a large and broad group of stakeholders. Industrial clusters and ports regard hydrogen as an indispensable part of their future and sustainability strategy. For the transport sector hydrogen (in combination with fuel cells) is crucial to achieving zero emissions transport. The agricultural sector has identified opportunities for the production of hydrogen and for its use. Cities regions and provinces are keen to get started on implementing hydrogen.<br/>The government embraces these targets and recognises the power of the framework for action demonstrated by so many parties. The focus on clean hydrogen in the Netherlands will lead to the creation of new jobs improvements to air quality and moreover is crucial to the energy transition.

An accidental hydrogen release in equipment enclosures may result in the presence of a detonable mixture in a confined environment. Numerical simulation is potentially a useful tool for damage assessment in these situations. To assess the value of CFD techniques numerical simulation of detonation was performed for two realistic scenarios. The first scenario starts with a pipe failure in an electrolyzer resulting in a leak of 42 g of hydrogen. The second scenario deals with a failure in a reformer where 84 g of hydrogen is released. In both cases dispersion patterns were first obtained from separate numerical simulation and were then used as initial condition in a detonation simulation based upon the reactive Euler's equations. Energy was artificially added in a narrow region to simulate detonative ignition. In the electrolyzer ignition was assumed to occur 500 ms after beginning of the release. Results show a detonation failing on the top and bottom side but propagating left and right before eventually failing also. Average impulse was 500 Ns/m². For the reformer three cases were simulated with ignition 1.0 1.4 and 2.0 seconds after the beginning of the release. In two cases the detonation wave failed everywhere except in the direction of the release in which it continued propagating until reaching the side wall. In the third the detonation failed everywhere at first but later a deflagration to detonation transition occurred resulting in a strong wave that propagated rapidly toward the side wall. In all three cases the consequences are more serious than in the electrolyzer.

The paper presents an overview of the main results of the EC NOE HySafe activity to estimate an allowable hydrogen permeation rate for automotive legal requirements and standards. The work was undertaken as part of the HySafe internal project InsHyde.<br/>A slow long term hydrogen release such as that due to permeation from a vehicle into an inadequately ventilated enclosed structure is a potential risk associated with the use of hydrogen in automotive applications. Due to its small molecular size hydrogen permeates through the containment materials found in compressed gaseous hydrogen storage systems and is an issue that requires consideration for containers with non-metallic (polymer) liners. Permeation from compressed gaseous hydrogen storage systems is a current hydrogen safety topic relevant to regulatory and standardisation activities at both global and regional levels.<br/>Various rates have been proposed in different draft legal requirements and standards based on different scenarios and the assumption that hydrogen dispenses homogeneously. This paper focuses on the development of a methodology by HySafe Partners (CEA NCSRD. University of Ulster and Volvo Technology) to estimate an allowable upper limit for hydrogen permeation in automotive applications by investigating the behaviour of hydrogen when released at small rates with a focus on European scenario. The background to the activity is explained. reasonable scenarios are identified a methodology proposed and a maximum hydrogen permeation rate from road vehicles into enclosed structures is estimated The work is based on conclusions from the experimental and numerical investigations described by CEA NCSRD and the University of Ulster in related papers.

The properties of hydrogen compared to conventional fuels such as gasoline and diesel are substantially different requiring adaptations to the design and layout of test cells for hydrogen fuelled engines and vehicles. A comparison of hydrogen fuel properties versus conventional fuels in this paper provides identification of requirements that need to be adapted to design a safe test cell. Design examples of actual test cells are provided to showcase the differences in overall layout and ventilation safety features fuel supply and metering and emissions measurements. Details include requirements for ventilation patterns the necessity for engine fume hoods as well as hydrogen specific intake and exhaust design. The unique properties of hydrogen in particular the wide flammability limits and nonvisible flames also require additional safety features such as hydrogen sensors and flame cameras. A properly designed and implemented fuel supply system adds to the safety of the test cell by minimizing the amount of hydrogen that can be released. Apart from this the properties of hydrogen also require different fuel consumption measurement systems pressure levels of the fuel supply system additional ventilation lines strategically placed safety solenoids combined with appropriate operational procedures. The emissions measurement for hydrogen application has to be expanded to include the amount of unburned hydrogen in the exhaust as a measurement of completeness of combustion. This measurement can also be used as a safety feature to avoid creation of ignitable hydrogen-air mixtures in the engine exhaust. The considerations provided in this paper lead to the conclusion that hydrogen IC engines can be safely tested however properly designed test cell and safety features have to be included to mitigate the additional hazards related to the change in fuel characteristics.

The ignition limits of hydrogen/air mixtures in turbulent jets are necessary to establish safety distances based on ignitable hydrogen location for safety codes and standards development. Studies in turbulent natural gas jets have shown that the mean fuel concentration is insufficient to determine the flammable boundaries of the jet. Instead integration of probability density functions (PDFs) of local fuel concentration within the quiescent flammability limits termed the flammability factor (FF) was shown to provide a better representation of ignition probability (PI). Recent studies in turbulent hydrogen jets showed that the envelope of ignitable gas composition (based on the mean hydrogen concentration) did not correspond to the known flammability limits for quiescent hydrogen/air mixtures. The objective of this investigation is to validate the FF approach to the prediction of ignition in hydrogen leak scenarios. The PI within a turbulent hydrogen jet was determined using a pulsed Nd:YAG laser as the ignition source. Laser Rayleigh scattering was used to characterize the fuel concentration throughout the jet. Measurements in methane and hydrogen jets exhibit similar trends in the ignition contour which broadens radially until an axial location is reached after which the contour moves inward to the centerline. Measurements of the mean and fluctuating hydrogen concentration are used to characterize the local composition statistics conditional on whether the laser spark results in a local ignition event or complete light-up of a stable jet flame. The FF is obtained through direct integration of local PDFs. A model was developed to predict the FF using a presumed PDF with parameters obtained from experimental data and computer simulations. Intermittency effects that are important in the shear layer are incorporated in a composite PDF. By comparing the computed FF with the measured PI we have validated the flammability factor approach for application to ignition of hydrogen jets.

There exists an international commitment to increase the utilization of hydrogen as a clean and renewable alternative to carbon-based fuels. The availability of hydrogen safety sensors is critical to assure the safe deployment of hydrogen systems. Already the use of hydrogen safety sensors is required for the indoor fueling of fuel cell powered forklifts (e.g. NFPA 52 Vehicular Fuel Systems Code [1]). Additional Codes and Standards specific to hydrogen detectors are being developed [2 3] which when adopted will impose mandatory analytical performance metrics. There are a large number of commercially available hydrogen safety sensors. Because end-users have a broad range of sensor options for their specific applications the final selection of an appropriate sensor technology can be complicated. Facility engineers and other end-users are expected to select the optimal sensor technology choice. However some sensor technologies may not be a good fit for a given application. Informed decisions require an understanding of the general analytical performance specifications that can be expected by a given sensor technology. Although there are a large number of commercial sensors most can be classified into relatively few specific sensor types (e.g. electrochemical metal oxide catalytic bead and others). Performance metrics of commercial sensors produced on a specific platform may vary between manufacturers but to a significant degree a specific platform has characteristic analytical trends advantages and limitations. Knowledge of these trends facilitates the selection of the optimal technology for a specific application (i.e. indoor vs. outdoor environments). An understanding of the various sensor options and their general analytical performance specifications would be invaluable in guiding the selection of the most appropriate technology for the designated application.

The UK government has committed to reducing greenhouse gas emissions to net zero by 2050. All future energy modelling identifies a key role for hydrogen (linked to CCUS) in providing decarbonised energy for heat transport industry and power generation. Blending hydrogen into the existing natural gas pipeline network has already been proposed as a means of transporting low carbon energy. However the expectation is that a gas blend with maximum hydrogen content of 20 mol% can be used without impacting consumers’ end use applications. Therefore a transitional solution is needed to achieve a 100% hydrogen future network.

Deblending (i.e. separation of the blended gas stream) is a potential solution to allow the existing gas transmission and distribution network infrastructure to transport energy as a blended gas stream. Deblending can provide either hydrogen natural gas or blended gas for space heating transport industry and power generation applications. If proven technically and economically feasible utilising the existing gas transmission and distribution networks in this manner could avoid the need for investment in separate gas and hydrogen pipeline networks during the transition to a future fully decarbonised gas network.

The Energy Network Association (ENA) “Gas Goes Green” programme identifies deblending could play a critical role in the transition to a decarbonised gas network. Gas separation technologies are well-established and mature and have been used and proven in natural gas processing for decades. However these technologies have not been used for bulk gas transportation in a transmission and distribution network setting. Some emerging hydrogen separation technologies are currently under development. The main hydrogen recovery and purification technologies currently deployed globally are:

• Cryogenic separation
• Membrane separation
• Pressure Swing Adsorption (PSA)

The technologies noted above require an energy input to drive the separation of gas components in the form of compression to provide a pressure differential. The configuration of the GB gas transmission and distribution networks provides a possible source of available energy through the pressure let-down in the network pressure tiers which could be used to drive the gas component separation processes. This study evaluated the gas separation technologies noted above against a selection of case studies based on actual network operating conditions to assess the technical andeconomic feasibility of hydrogen deblending in the GB gas network context. This study constitutes the first stage (proof of concept) in a programme of works that should provide the critical evidence for hydrogen deblending as a necessary component to enable the use of GB gas networks to transport and distribute hydrogen.

This report and any attachment is freely available on the ENA Smarter Networks Portal here. IGEM Members can download the report and any attachment directly by clicking on the pdf icon above.

The report makes a recommendation for a minimum hydrogen purity standard to be used by manufacturers developing prototype hydrogen appliances and during their subsequent demonstration as part of the Hy4Heat programme. It makes a recommendation for a hydrogen purity level with the aim that it is reasonable and practicable and considers implications related to hydrogen production the gas network and cost.

This report and any attachment is freely available on the Hy4Heat website here. The report can also be downloaded directly by clicking on the pdf icon above 

Performing research in the interest of providing relevant safety requirements is a valuable and essential endeavor but translating research results into enforceable requirements adopted into codes and standards a process sometimes referred to as codification can be a separate and challenging task. This paper discusses the process utilized to successfully translate research results related to bulk gaseous hydrogen storage separation (or stand-off) distances into code requirements in NFPA 55:Storage Use and Handling of Compressed Gases and Cryogenic Fluids in Portable and StationaryContainers Cylinders and Tanks and NFPA 2: Hydrogen Technologies. The process utilized can besummarized as follows: First the technical committees for the documents to be revised were engaged to confirm that the codification process was endorsed by the committee. Then a sub-committee referred to as a task group was formed. A chair must be elected or appointed. The chair should be a generalist with code enforcement or application experience. The task group was populated with several voting members of each technical committee. By having voting members as part of the task group the group becomes empowered and uniquely different from any other code proposal generating body. The task group was also populated with technical experts as needed but primarily the experts needed are the researchers involved. Once properly populated and empowered the task group must actively engage its members. The researchers must educate the code makers on the methods and limitations of their work and the code makers must take the research results and fill the gaps as needed to build consensus and create enforceable code language and generate a code change proposal that will be accepted. While this process seems simple there are pitfalls along the way that can impede or nullify the desired end result – changes to codes and standards. A few of these pitfalls include: wrong task group membership task group not empowered task group not supported in-person meetings not possible consensus not achieved. This paper focuses on the process used and how pitfalls can be avoided for future efforts.

Discrete Event Simulation (DES) environments are rapidly developing and they appear to be promising tools for developing reliability and risk analysis models of safety-critical systems. DES models are an alternative to the conventional methods such as fault and event trees Bayesian networks and cause-consequence diagrams that could be used to assess the reliability of fuel supply. DES models can rather easily account for the dynamic dimensions and other important features that can hardly be captured by the conventional models. The paper describes a novel approach to estimate gas supply security and the reliability/safety of gas installations and argues that this approach can be transferred to estimate future hydrogen supply reliability. The core of the approach is a DES model of gas or other fuel propulsion through a pipeline to the customers and failures of the components of the pipeline. We will argue in the paper that the experience gained in the modelling of gas supply reliability is very relevant to the security and safety of a future hydrogen supply and worth being employed in this area.

Element One Inc. is developing novel indicators for hydrogen gas for applications as a complement to conventional electronic hydrogen sensors or as a low-cost alternative in situations where an electronic signal is not needed. The indicator consists of a thin film coating or a pigment of a transition metal oxide such as tungsten oxide or molybdenum oxide with a catalyst such as platinum or palladium. The oxide is partially reduced in the presence of hydrogen in concentrations as low as 300 parts per million and changes from transparent to a dark colour. The colour change is fast and easily seen from a distance. In air the colour change reverses quickly when the source of hydrogen gas is removed in the case of tungsten oxide or is nearly irreversible in the case of molybdenum oxide. A number of possible implementations have been successfully demonstrated in the laboratory including hydrogen indicating paints tape cautionary decals and coatings for hydrogen storage tanks. These and other implementations may find use in vehicles stationary appliances piping refuelling stations and in closed spaces such as maintenance and residential garages for hydrogen-fuelled vehicles. The partially reduced transition metal oxide becomes semi conductive and increases its electrical conductivity by several orders of magnitude when exposed to hydrogen. The integration of this electrical resistance sensor with an RFID tag may extend the ability of these sensors to record and transmit a history of the presence or absence of leaked hydrogen over long distances. Over long periods of exposure to the atmosphere the indicator’s response may slow due to catalyst degradation. Our current emphasis is on controlling this degradation. The kinetics of the visual indicators is being investigated along with their durability in collaboration with the NASA Kennedy Space Center.

If the ‘Hydrogen Economy’ is to progress more hydrogen fuelling stations are required. In the short term and in the absence of a hydrogen distribution network these fuelling stations will have to be supplied by liquid hydrogen (LH2) road tankers. Such a development will increase the number of tanker offloading operations significantly and these may need to be performed in close proximity to the general public. LH2 was first investigated experimentally as large-scale spills of LH2 at a rate of 60 litres per minute. Measurements were made on un-ignited releases which included the concentration of hydrogen in air thermal gradients in the concrete substrate liquid pool formation and temperatures within the pool. Computational modelling on the un-ignited spills was also performed. The experimental work on ignited releases of LH2 detailed in this paper is a continuation of the work performed by Royle and Willoughby. The experimental findings presented are split into three phenomena; jet-fires in high and low wind conditions ‘burn-back’ of ignited clouds and secondary explosions post ‘burn-back’. The aim of this work was to determine the hazards and severity of a realistic ignited spill of LH2 focussing on; flammability limits of an LH2 vapour cloud flame speeds through an LH2 vapour cloud and subsequent radiative heat levels after ignition. An attempt was made to estimate the magnitude of an explosion that occurred during one of the releases. The results of these experiments will inform the wider hydrogen community and contribute to the development of more robust modelling tools. The resulting data were used to propose safety distances for LH2 offloading facilities which will help to update and develop guidance for codes and standards.

The facility will be built from a range of decommissioned transmission assets to create a representative whole-network which will be used to trial hydrogen and will allow for accurate results to be analysed. Blends of hydrogen up to 100% will then be tested at transmission pressures to assess how the assets perform.<br/>The hydrogen research facility will remain separate from the main National Transmission System allowing for testing to be undertaken in a controlled environment with no risk to the safety and reliability of the existing gas transmission network.<br/>Ofgem’s Network Innovation Competition will provide £9.07m of funding with the remaining amount coming from the project partners.<br/>The aim is to start construction in 2021 with testing beginning in 2022.

In case of severe accidents in Pressurized Water Reactors a great amount of hydrogen can be released the resulting heterogeneous gaseous mixture (hydrogen-air-steam) can be flammable or inert and the pressure effects could alter the confinement of the reactor. Water spray systems have been designed in order to reduce overpressures in the containment but the presence of water droplets could enhance flame propagation through turbulence or generate flammable mixtures since the steam present in the vessel could condense on the droplets and could not inert the mixture anymore. However beneficial effects would be heat sinks and homogenization of mixtures. On-going work is devoted to the modelling of the interaction between fine water droplets and a hydrogen-air flame. We present in this paper an unsteady Lumped Parameter model in detail with a special focus on hydrogen-air flame propagation in the presence of water droplets. The effects of the initial concentration of droplets steam and hydrogen concentrations on flame propagation are discussed in the paper and a comparison between this model and our previous steady Lumped-Parameter model highlights the features of the unsteady approach. This physical model can serve as a validation tool for a CFD modelling. The results will be further validated against experimental data.

To handle a hydrogen fuel cell vehicle (HFCV) safely after its involvement in an accident it is necessary to provide appropriate emergency response information to the first responder. In the present study a forced wind of 10 m/s or faster with and without a duct was applied to a vehicle leaking hydrogen gas at a rate of 2000 NL/min. Then hydrogen concentrations were measured around the vehicle and an ignition test was conducted to evaluate the effectiveness of forced winds and the safety of emergency response under forced wind conditions. The results: 1) Forced winds of 10 m/s or faster caused the hydrogen concentrations in the vicinity of the vehicle to decline to less than the lower flammability limit and the hydrogen gas in the various sections of the vehicles were so diluted that even if ignition occurred the blast-wave pressure was moderate. 2) When the first responder had located the hydrogen leakage point in the vehicle it was possible to lower the hydrogen concentrations around the vehicle by aiming the wind duct towards the leakage point and blowing winds at 10 m/s from the duct exit.

Green hydrogen has the potential to play a significant role in our energy system and could play an important role in decarbonising parts of our economy.

To assist with the development of the Hydrogen Green Paper MBIE assisted by consultants Arup – held four workshops with key stakeholders in Wellington Auckland Christchurch and New Plymouth. The workshops were well attended with a range of views expressed on the potential for hydrogen in New Zealand. Following the workshops we incorporated these views into a Hydrogen Green Paper which was released for public consultation. We sought feedback from the public and wider stakeholders about the challenges and opportunities of building a hydrogen economy in New Zealand as part of our renewable energy strategy. On 2 September 2019 we released the green paper – “A vision for hydrogen in New Zealand”. Consultation ended on 25 October 2019. The green paper looked at the scope of New Zealand’s hydrogen potential to frame discussions for a national strategy.

The green paper asked 27 questions about the challenges and opportunities and the Government’s role in nine key areas:

1. Hydrogen production
2. Hydrogen electricity nexus
3. Hydrogen for mobility
4. Hydrogen for industrial processes
5. Hydrogen for seasonal power generation
6. Decarbonisation of our gas
7. Hydrogen for export
8. Innovation expands job opportunities
9. Transitioning the job market

We received 78 submissions from the public industry research institutions and public and private sector organisations.

This green paper along with the submissions will feed into a wider renewable energy strategy for New Zealand. This will outline the renewable energy pathway to a clean green carbon neutral for New Zealand by 2050.

Refueling infrastructure for use in gaseous hydrogen powered vehicles requires extensive manifolding for delivering the hydrogen from the stationary fuel storage at the refueling station to the vehicle as well as from the mobile storage on the vehicle to the fuel cell or combustion engine. Manifolds for gas handling often use welded construction (as opposed to compression fittings) to minimize gas leaks. Therefore it is important to understand the effects of hydrogen on tubing and tubing welds. This paper provides a brief overview of on-going studies on the effects of hydrogen precharging on the tensile properties of austenitic stainless tubing and orbital tube welds of several austenitic stainless steels.

This document summarizes current hydrogen technologies and communicates the U.S. Department of Energy (DOE) Office of Fossil Energy's (FE's) strategic plan to accelerate research development and deploymnet of hydrogen technologies in the United States. It also describes ongoing FE hydrogen-related research and development (R&D). Hydrogen from fossil fuels is a versatile energy carrier and can play an important role in the transition to a low-carbon economy.

This paper is an investigation of the spontaneous ignition process of high-pressure hydrogen and hydrogen-methane mixtures injected into air. The experiments were conducted in a closed channel filled with air where the hydrogen or hydrogen–methane mixture depressurised through different tubes (diameters d = 6 10 and 14 mm and lengths L = 10 25 40 50 75 and 100 mm). The methane addition to the mixture was 5% and 10% vol. The results showed that only 5% methane addition may increase even 2.67 times the pressure at which the mixture may ignite in comparison to the pressure of the pure hydrogen flow. The 10% of methane addition did not provide an ignition for burst pressures up to 15.0 MPa in the geometrical configuration with the longest tube (100 mm). Additionally the simulations of the experimental configuration with pure hydrogen were performed with the use of KIVA numerical code with full kinetic reaction mechanism.

Photosynthesis is considered to be one of the promising areas of cheap and environmentally friendly energy. Photosynthesis involves the process of water oxidation with the formation of molecular oxygen and hydrogen as byproducts. The aim of the present article is to review the energy (light) phase of photosynthesis based on the published X-ray studies of photosystems I and II (PS-I and PS-II). Using modern ideas about semiconductors and biological semiconductor structures the mechanisms of H+ O2↑ e− generation from water are described. At the initial stage PS II produces hydrogen peroxide from water as a result of the photoenzymatic reaction which is oxidized in the active center of PS-II on the Mn4CaO5 cluster to form O2↑ H+ e−. Mn4+ is reduced to Mn2+ and then oxidized to Mn4+ with the transfer of reducing the equivalents of PS-I. The electrons formed are transported to PS-I (P 700) where the electrochemical reaction of water decomposition takes place in a two-electrode electrolysis system with the formation of gaseous oxygen and hydrogen. The proposed functioning mechanisms of PS-I and PS-II can be used in the development of environmentally friendly technologies for the production of molecular hydrogen.

Hydrogen is expected to become a key component in the decarbonized energy systems of the future. Its unique chemical characteristics make hydrogen a carbon-free fuel that is suitable to be used as broadly as fossil fuels are used today. Since hydrogen can be produced by splitting water molecules using electricity as the only energy input needed hydrogen offers the opportunity to produce a fully renewable fuel if the electricity input also only stems from renewable sources. Once renewable electricity is converted into hydrogen it can be stored over long periods of time and transported over long even intercontinental distances. Underground hydrogen storage pipelines compressors liquefaction-units and transportation ships are infrastructures and suitable technologies to establish a global hydrogen energy system. Several chemical synthesis routes exist to produce more complex products from green hydrogen to fulfil the demands of various end-users and industries. One exemplary power-to-gas product is methane which can be used as a natural gas substitute. Furthermore ammonia alcohols kerosene and all other important products from hydrocarbon chemistry can be synthesized using green hydrogen.