Transmission, Distribution & Storage

When steel components fail in service due to the intervention of hydrogen assisted cracking discussion of the root cause arises. The failure is frequently blamed on component design working conditions the manufacturing process or the raw material. This work studies the influence of quench and tempering and hot-dip galvanizing on the hydrogen embrittlement behavior of a high strength steel. Slow strain rate tensile testing has been employed to assess this influence. Two sets of specimens have been tested both in air and immersed in synthetic seawater at three process steps: in the delivery condition of the raw material after heat treatment and after heat treatment plus hot-dip galvanizing. One of the specimen sets has been tested without further manipulation and the other set has been tested after applying a hydrogen effusion treatment. The outcome for this case study is that fracture risk issues only arise due to hydrogen re-embrittlement in wet service.

Hydrogen technologies have been rapidly developing in the past few decades pushed by governments’ road maps for sustainability and supported by a widespread need to decarbonize the global energy sector. Recent scientific progress has led to better performances and higher efficiencies of hydrogen-related technologies so much so that their future economic viability is now rarely called into question. This article intends to study the integration of hydrogen systems in both gas and electric distribution networks. A preliminary analysis of hydrogen’s physical storage methods is given considering both the advantages and disadvantages of each one. After examining the preeminent ways of physically storing hydrogen this paper then contemplates two primary means of using it: integrating it in Power-to-Gas networks and utilizing it in Power-to-Power smart grids. In the former the primary objective is the total replacement of natural gas with hydrogen through progressive blending procedures from the transmission pipeline to the domestic burner; in the latter the set goal is the expansion of the implementation of hydrogen systems—namely storage—in multi-microgrid networks thus helping to decarbonize the electricity sector and reducing the impact of renewable energy’s intermittence through Demand Side Management strategies. The study concludes that hydrogen is assumed to be an energy vector that is inextricable from the necessary transition to a cleaner more efficient and sustainable future.

The present work provides an overview of the work on the interaction between hydrogen (H) and the steel’s microstructure. Different techniques are used to evaluate the H-induced damage phenomena. The impact of H charging on multiphase high-strength steels i.e. high-strength low-alloy (HSLA) transformation-induced plasticity (TRIP) and dual phase (DP) is first studied. The highest hydrogen embrittlement resistance is obtained for HSLA steel due to the presence of Ti- and Nb-based precipitates. Generic Fe-C lab-cast alloys consisting of a single phase i.e. ferrite bainite pearlite or martensite and with carbon contents of approximately 0 0.2 and 0.4 wt % are further considered to simplify the microstructure. Finally the addition of carbides is investigated in lab-cast Fe-C-X alloys by adding a ternary carbide forming element to the Fe-C alloys. To understand the H/material interaction a comparison of the available H trapping sites the H pick-up level and the H diffusivity with the H-induced mechanical degradation or H-induced cracking is correlated with a thorough microstructural analysis.

The development of a hydrogen-based economy is the perfect nexus between the need of discontinuing the use of fossil fuels (trying to mitigate climate change) the development of a system based on renewable energy (with the use of hydrogen allowing us to buffer the discontinuities produced in this generation) and the achievement of a local-based robust energy supply system. However extending the use of hydrogen as an energy vector must still overcome challenging issues with the key issues being related to its storage. Cryogenic or pressurized storage is relatively expensive technically complex and presents important safety concerns. As a promising alternative the use of organic hydrogen carriers has been suggested in recent years. The ideal carrier will be an organic compound with a low melting point and low viscosity with a significant number of unsaturated carbon–carbon bonds in addition to being easy to hydrogenate and dehydrogenate. These properties allow us to store and transport hydrogen in infrastructures designed for liquid fuels thus facilitating the replacement of fossil fuels by hydrogen

This study investigated the influence of segregations on hydrogen environment embrittlement (HEE) of AISI 304L type austenitic stainless steels. The microstructure of tensile specimens that were fabricated from commercially available AISI 304L steels and tested by means of small strain-rate tensile tests in air as well as hydrogen gas at room temperature was investigated by means of combined EDS and EBSD measurements. It was shown that two different austenitic stainless steels having the same nominal alloy composition can exhibit different susceptibilities to HEE due to segregation effects resulting from different production routes (continuous casting/electroslag remelting). Local segregation-related variations of the austenite stability were evaluated by thermodynamic and empirical calculations. The alloying element Ni exhibits pronounced segregation bands parallel to the rolling direction of the material which strongly influences the local austenite stability. The latter was revealed by generating and evaluating two-dimensional distribution maps for the austenite stability. The formation of deformation-induced martensite was shown to be restricted to segregation bands with a low Ni content. Furthermore it was shown that the formation of hydrogen induced surface cracks is strongly coupled with the existence of surface regions of low Ni content and accordingly low austenite stability. In addition the growth behavior of hydrogen-induced cracks was linked to the segregation-related local austenite stability.

The Isle of Grain (IoG) presents a technically feasible commercially viable strategic location to build and operate a hydrogen production facility which would be a key enabler to the UK meeting the Net Zero 2050 target.

As highlighted in the ‘Net Zero – The UK’s contribution to stopping global warming’ report published by The Committee on Climate Change in May 2019 hydrogen is set to have a major part to play in reducing UK carbon dioxide emissions. Carbon Capture and Storage (CCS) is also seen as essential to support those supplies.

The report further recognises that this will involve increased investments and that CCS and hydrogen will require both capital funding and revenue support.

For hydrogen to have a part to play in the decarbonisation of London and the south east of England a large-scale hydrogen production facility will be required which will provide a multi vector solution through the decarbonisation of the gas grid.

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The objective of this work was to enable the safe design of hydrogen pressure vessels by measuring the fatigue crack growth rates of ASME code-qualified steels in high-pressure hydrogen gas. While a design framework has recently been established for high-pressure hydrogen vessels a material property database does not exist to support the design calculations. This study addresses such voids in the database by measuring the fatigue crack growth rates of three different heats of ASME SA-372 Grade J steel in 100 MPa hydrogen gas. Results showed that the fatigue crack growth rates were similar for all three steel heats although the highest-strength steel appeared to exhibit the highest growth rates. Hydrogen accelerated the fatigue crack growth rates of the steels by as much as two orders of magnitude relative to anticipated crack growth rates in inert environments. Despite such dramatic effects of hydrogen on the fatigue crack growth rates measurement of these properties enables reliable definition of the design life of steel hydrogen containment vessels.

The liquid organic hydrogen carriers (LOHC) are aromatic molecules which can be considered as an attractive option for the storage and transport of hydrogen. A considerable amount of hydrogen up to 7–8% wt. can be loaded and unloaded with a reversible chemical reaction. Substituted quinolines and pyridines are available from petroleum coal processing and wood preservation or they can be synthesized from aniline. Quinolines and pyridines can be considered as potential LOHC systems provided they have favorable thermodynamic properties which were the focus of this current study. The absolute vapor pressures of methyl-quinolines were measured using the transpiration method. The standard molar enthalpies of vaporization of alkyl-substituted quinolines and pyridines were derived from the vapor pressure temperature dependencies. Thermodynamic data on vaporization and formation enthalpies available in the literature were collected evaluated and combined with our own experimental results. The theoretical standard molar gas-phase enthalpies of formation of quinolines and pyridines calculated using the quantum-chemical G4 methods agreed well with the evaluated experimental data. Reliable standard molar enthalpies of formation in the liquid phase were derived by combining high-level quantum chemistry values of gas-phase enthalpies of formation with experimentally determined enthalpies of vaporization. The liquid-phase hydrogenation/dehydrogenation reaction enthalpies of alkyl-substituted pyridines and quinolines were calculated and compared with the data for other potential liquid organic hydrogen carriers. The comparatively low enthalpies of reaction make these heteroaromatics a seminal LOHC system.

The UK has committed to significantly reduce greenhouse gas emissions by 2050 to help address climate change. Decarbonising heating is a key part of this and using hydrogen (H2) as a replacement to natural gas (NG) can help in achieving this. The objective of current research including HyDeploy is to demonstrate that NG containing levels of H2 beyond those currently allowed of 0.1 vol% (1000 ppm) [1] can be distributed and utilised safely and efficiently. Initial projects such as HyDeploy are studying the effects of introducing up to 20 vol% H2 in NG but later projects are considering using up to 100 vol% H2.

A key element in the safe operation of a modern gas distribution system is gas detection. However the addition of hydrogen to NG will alter the characteristics of the gas and the impact on gas detection must be considered. It is important that sensors remain sufficiently sensitive to the presence of hydrogen natural gas carbon monoxide (CO) and oxygen (O2) deficiency and that they don’t lead to false positive or false negative readings. The aim of this document is to provide a summary of the requirements for gas detection of hydrogen enriched natural gas for the gas distribution industry and other potentially interested parties. As such it is based on gas detectors presently used by the industry with the only major differences being the effects of hydrogen on the sensitivity of flammable gas sensors and the cross sensitivity of carbon monoxide gas sensors to hydrogen.

There is further information of gas detector concepts and technologies in the appendices.

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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.

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