Transmission, Distribution & Storage

Liquid organic hydrogen carriers (LOHC) are a technology that allows storing hy-drogen in a safe and dense manner by reversible chemical conversion. They consti-tute a very promising option for energy storage transport and release combined withelectric power generation by fuel cells in large-scale applications like trains. In orderto establish trains running on LOHC it is mandatory to ensure the reliability of thesystem. This study evaluates various system configurations concerning reliabilityand resilience. The fault tree analysis method has been used to quantify the prob-ability of failure. The S-P matrix was applied to assess the different failure modes incontext of severity as well as their probability. The MTTF of the system can be morethan doubled by introducing single redundancy for the fuel cell and the reactor whilemore than two redundant components diminish the positive effect on reliability dueto higher complexity. It is estimated that the systems full functionality is available formore than 97% of its operating time.

Pipelines during their service life subjected to operational degradation i.e. their mechanical characteristics worsened with time. Pronounced texture of pipe steels associated with their manufacturing process revealed itself in an essential difference in impact toughness determined for specimens cut in mutually perpendicular directions with respect to the pipe axis. Higher KCV values for longitudinal specimens as compared with transverse ones were explained by the difference in a length of perlite grain strips separated by ferrite grains in specimens of different orientation. A role of hydrogen absorbed my metal during its operation in steel degradation was discussed.<br/>The main fractographic peculiarity for the operated steels comparing to the steels in the initial state is the appearance of delamination on the fracture surfaces which are oriented in the rolling direction. Correlation was found for the tested steels between fractographic sings of their embrittlement due to operational degradation and their loss of brittle fracture resistance. It is concluded that a decrease of impact toughness caused by long term operation of pipeline steels is definitely concerned with the amount of delamination on the fracture surfaces.

In the present work the effect of artificial ageing of AA2024-T3 on the tensile mechanical properties and fracture toughness degradation due to corrosion exposure will be investigated. Tensile and fracture toughness specimens were artificially aged to tempers that correspond to Under-Ageing (UA) Peak-Ageing (PA) and Over-Ageing (OA) conditions and then were subsequently exposed to exfoliation corrosion environment. The corrosion exposure time was selected to be the least possible according to the experimental work of Alexopoulos et al. (2016) so as to avoid the formation of large surface pits trying to simulate the hydrogen embrittlement degradation only. The mechanical test results show that minimum corrosion-induced decrease in elongation at fracture was achieved for the peak-ageing condition while maximum was noticed at the under-ageing and over-ageing conditions. Yield stress decrease due to corrosion is less sensitive to tempering; fracture toughness decrease was sensitive to ageing heat treatment thus proving that the S΄ particles play a significant role on the corrosion-induced degradation.

Microalloyed steels have evolved in terms of their chemical composition processing and metallurgical characteristics since the beginning of the 20th century in the function of fabrication costs and mechanical properties required to obtain high-performance materials needed to accommodate for the growing demands of gas and hydrocarbons transport. As a result of this microalloyed steels present a good combination of high strength and ductility obtained through the addition of microalloying elements thermomechanical processing and controlled cooling processes capable of producing complex microstructures that improve the mechanical properties of steels. These controlled microstructures can be severely affected and result in catastrophic failures due to the atomic hydrogen diffusion that occurs during the corrosion process of pipeline steel. Recently a martensite–bainite microstructure with acicular ferrite has been chosen as a viable candidate to be used in environments with the presence of hydrogen. The aim of this review is to summarize the main changes of chemical composition processing techniques and the evolution of the mechanical properties throughout recent history on the use of microalloying in high strength low alloy steels as well as the effects of hydrogen in newly created pipelines examining the causes behind the mechanisms of hydrogen embrittlement in these steels.

The cost of the hydrogen value chain needs to be reduced to allow the widespread development of hydrogen applications. Mechanical compressors widely used for compressing hydrogen to date account for more than 50% of the CAPEX (capital expenditure) in a hydrogen refuelling station. Moreover mechanical compressors have several disadvantages such as the presence of many moving parts hydrogen embrittlement and high consumption of energy. Non-mechanical hydrogen compressors have proven to be a valid alternative to mechanical compressors. Among these electrochemical compressors allow isothermal and therefore highly efficient compression of hydrogen. On the other hand adsorption-desorption compressors allow hydrogen to be compressed through cooling/heating cycles using highly microporous materials as hydrogen adsorbents. A non-mechanical hybrid hydrogen compressor consisting of a first electrochemical stage followed by a second stage driven by adsorption-desorption of hydrogen on activated carbons allows hydrogen to be produced at 70 MPa a value currently required for the development of hydrogen automotive applications. This system has several advantages over mechanical compressors such as the absence of moving parts and high compactness. Its use in decentralized hydrogen facilities such as hydrogen refuelling stations can be considered

Compact-tension (CT) specimens made of low alloy 30CrMo steels were hydrogen-charged and then subjected to the fracture toughness test. The experimental results revealed that the higher crack propagation and the lower crack growth resistance (CTOD-R curve) are significantly noticeable with increasing hydrogen embrittlement (HE) indexes. Moreover the transition in the microstructural fracture mechanism from ductile (microvoid coalescence (MVC)) without hydrogen to a mixed quasi-cleavage (QC) fracture and QC + intergranular (IG) fracture with hydrogen was observed. The hydrogen-enhanced decohesion (HEDE) mechanism was characterized as the dominant HE mechanism. According to the experimental testing the coupled problem of stress field and hydrogen diffusion field with cohesive zone stress analysis was employed to simulate hydrogen-assisted brittle fracture behavior by using ABAQUS software. The trapezoidal traction-separation law (TSL) was adopted and the initial TSL parameters from the best fit to the load-displacement and J-integral experimental curves without hydrogen were calibrated for the critical separation of 0.0393 mm and the cohesive strength of 2100 MPa. The HEDE was implemented through hydrogen influence in the TSL and to estimate the initial hydrogen concentration based on matching numerical and experimental load-line displacement curves with hydrogen. The simulation results show that the general trend of the computational CTOD-R curves corresponding to initial hydrogen concentration is almost the same as that obtained from the experimental data but in full agreement the computational CTOD values being slightly higher. Comparative analysis of numerical and experimental results shows that the coupled model can provide design and prediction to calculate hydrogen-assisted fracture behavior prior to extensive laboratory testing provided that the material properties and properly calibrated TSL parameters are known.

Hydrogen energy with environment amicable renewable efficiency and cost-effective advantages is the future mainstream substitution of fossil-based fuel. However the extremely low volumetric density gives rise to the main challenge in hydrogen storage and therefore exploring effective storage techniques is key hurdles that need to be crossed to accomplish the sustainable hydrogen economy. Hydrogen physically or chemically stored into nanomaterials in the solid-state is a desirable prospect for effective large-scale hydrogen storage which has exhibited great potentials for applications in both reversible onboard storage and regenerable off-board storage applications. Its attractive points include safe compact light reversibility and efficiently produce sufficient pure hydrogen fuel under the mild condition. This review comprehensively gathers the state-of-art solid-state hydrogen storage technologies using nanostructured materials involving nanoporous carbon materials metal-organic frameworks covalent organic frameworks porous aromatic frameworks nanoporous organic polymers and nanoscale hydrides. It describes significant advances achieved so far and main barriers need to be surmounted to approach practical applications as well as offers a perspective for sustainable energy research.

The growth of the world’s energy demand over recent decades in relation to energy intensity and demography is clear. At the same time the use of renewable energy sources is pursued to address decarbonization targets but the stochasticity of renewable energy systems produces an increasing need for management systems to supply such energy volume while guaranteeing at the same time the security and reliability of the microgrids. Locally distributed energy storage systems (ESS) may provide the capacity to temporarily decouple production and demand. In this sense the most implemented ESS in local energy districts are small–medium-scale electrochemical batteries. However hydrogen systems are viable for storing larger energy quantities thanks to its intrinsic high mass-energy density. To match generation demand and storage energy management systems (EMSs) become crucial. This paper compares two strategies for an energy management system based on hydrogen-priority vs. battery-priority for the operation of a hybrid renewable microgrid. The overall performance of the two mentioned strategies is compared in the long-term operation via a set of evaluation parameters defined by the unmet load storage efficiency operating hours and cumulative energy. The results show that the hydrogen-priority strategy allows the microgrid to be led towards island operation because it saves a higher amount of energy while the battery-priority strategy reduces the energy efficiency in the storage round trip. The main contribution of this work lies in the demonstration that conventional EMS for microgrids’ operation based on battery-priority strategy should turn into hydrogen-priority to keep the reliability and independence of the microgrid in the long-term operation.

A sustainability assessment regarding the manufacturing process and the use of a new proton exchange membrane fuel cell (PEMFC) specially designed for portable hydrogen applications is presented. The initial fuel cell prototype has been configured by taking into account exclusively technical issues. However a life cycle analysis considering environmental and socioeconomic impacts is crucial to improve the model to develop a more sustainable product. From the environ‐ mental perspective the durability of the system and its efficiency are key elements required to de‐ crease the potential overall impacts. High electricity consumption for manufacturing requires a commitment to the use of renewable energies due to the high current value of the projected impact of climate change (42.5 tonnes of CO2 eq). From the socioeconomic point of view the dependence of imported components required for the synthesis of some materials displaces the effects of value added and employment in Spain potentially concentrating the largest impact on countries such as Singapore Japan and the UK whereas the cell assembly would have a greater benefit for the country of fabrication. These results provide a basis for new research strategies since they can be considered standard values for improving future upgrades of the fuel cell in terms of sustainability.

Hydrogen as an energy carrier is very versatile in energy storage applications. Developments in novel sustainable technologies towards a CO2-free society are needed and the exploration of all-solid-state batteries (ASSBs) as well as solid-state hydrogen storage applications based on metal hydrides can provide solutions for such technologies. However there are still many technical challenges for both hydrogen storage material and ASSBs related to designing low-cost materials with low-environmental impact. The current materials considered for all-solid-state batteries should have high conductivities for Na+ Mg2+ and Ca2+ while Al3+-based compounds are often marginalised due to the lack of suitable electrode and electrolyte materials. In hydrogen storage materials the sluggish kinetic behaviour of solid-state hydride materials is one of the key constraints that limit their practical uses. Therefore it is necessary to overcome the kinetic issues of hydride materials before discussing and considering them on the system level. This review summarizes the achievements of the Marie Skłodowska-Curie Actions (MSCA) innovative training network (ITN) ECOSTORE the aim of which was the investigation of different aspects of (complex) metal hydride materials. Advances in battery and hydrogen storage materials for the efficient and compact storage of renewable energy production are discussed.