Transmission, Distribution & Storage

The NEWGASMET project has the overall objective to increase knowledge about the accuracy and durability of commercially available gas meters after exposure to renewable gases. This should lead to the improvement of existing meter designs and flow calibration standards. One of the recently released results is a proposal for a set of test gases to represent the range of non-conventional gases in the scope of the revision of the gas meter standards. In details these were proposed to be used in the CEN/TC237 standards and the OIML-R137:2014. During the project meetings concerns have been raised regarding the applicability of such test gases to EMC tests for static meters. Today such tests are performed in air but there is a clear agreement that the behaviour of the meter during EMC tests can be influenced by the renewable gas type. At least this agreement exists for the ultrasonic measurement technology while further discussion might be needed for the mass flow. However it is not simply possible to redesign the current EMC tests by replacing air with the defined gas mixtures as this would be quite impractical especially considering the explosive nature of the test gases.

In this podcast David Ledesma talks with Rahmat Poudineh Senior Research Fellow and Aliaksei Patonia Research Fellow on issues and options with respect to long distance transportation of the hydrogen.

Hydrogen currently is mainly a local or regional commodity. If hydrogen is to become a truly global-traded commodity it needs to be transported over long transoceanic distances in an economical way. However unlike natural gas shipping compressed or liquefied hydrogen over long distances is very inefficient and expensive. At the same time hydrogen can be converted into multiple carriers with a higher energy density and higher transport capacity such as liquid ammonia toluene/methylcyclohexane (MCH) or methanol. These chemicals have their own advantages and drawbacks and their techno-economic characteristics in terms of boil-off gas and thermodynamic and conversion losses play a key role in the efficiency of transoceanic transportation of the hydrogen.

On the other hand apart from techno-economic features there are other factors to consider for long distance transportation of the hydrogen via its careers. Here such issues as safety public acceptance as well as legal and regulatory constraints may come into play. Another factor is the availability of the industries and infrastructures already developed around any of possible hydrogen carriers as well as their potential industrial applicability beyond hydrogen. Finally technological progress in other decarbonization applications and most importantly full commercialization of CCUS solutions is likely to dramatically change the approach towards long distance hydrogen transportation.

The podcast can be found on their website. 

Replacement of fossil fuels with clean hydrogen has been recognized as the most feasible approach of implementing CO2-free hydrogen economy globally. However large-scale storage of hydrogen is a critical component of hydrogen economy value chain because hydrogen is the lightest molecule and has moderately low volumetric energy content. To achieve successful storage of buoyant hydrogen at the subsurface and convenient withdrawal during the period of critical energy demand the integrity of the underground storage rock and overlying seal (caprock) must be assured. Presently there is paucity of information on hydrogen wettability of shale and the interfacial properties of H2/brine system. In this research contact angles of shale/H2/brine system and hydrogen/brine interfacial tension (IFT) were measured using Krüss drop shape analyzer (DSA 100) at 50 ◦C and varying pressure (14.7–1000 psi). A modified form of sessile drop approach was used for the contact angles measurement whereas the H2- brine IFT was measured through the pendant drop method. H2-brine IFT values decreased slightly with increasing pressure ranging between 63.68◦ at 14.7 psia and 51.29◦ at 1000 psia. The Eagle-ford shale with moderate total organic carbon (TOC) of 3.83% attained fully hydrogen-wet (contact angle of 99.9◦ ) and intermediate-wet condition (contact angle of 89.7◦ ) at 14.7 psi and 200 psi respectively. Likewise the Wolf-camp shale with low TOC (0.30%) attained weakly water-wet conditions with contact angles of 58.8◦ and 62.9◦ at 14.7 psi and 200 psi respectively. The maximum height of hydrogen that can be securely trapped by the Wolf-camp shale was approximately 325 meters whereas the value was merely 100 meters for the Eagle-ford shale. Results of this study will aid in assessment of hydrogen storage capacity of organic-rich shale (adsorption trapping) as well as evaluation of the sealing potentials of low TOC shale (caprock) during underground hydrogen storage.

Although electricity storage plays a decisive role for the German “Energiewende” and it has become evident that the successful diffusion of technologies is not only a question of technical feasibility but also of social acceptance research on electricity storage technologies from a social science point of view is still scarce. This study therefore empirically explores laypersons’ mindsets and knowledge related to storage technologies focusing on hydrogen. While the results indicate overall supportive attitudes and trust in hydrogen storage some misconceptions a lack of information as well as concerns were identified which should be addressed in future communication concepts.

Hydrogen uptake and embrittlement characteristics of a cold-drawn austenitic stainless steel wire were investigated. Slow strain rate testing and fracture surface analysis were applied to determine the hydrogen embrittlement resistance providing an apparent decrease in resistance to hydrogen embrittlement for a 50% degree of cold deformation. The hydrogen content was assessed by thermal desorption and laser-induced breakdown spectroscopy establishing a correlation between the total absorbed hydrogen and the intensity of near-surface hydrogen. The sub-surface hydrogen content of the hot-rolled specimen was determined to be 791 wt.ppm.

The share of electrical energy from renewable sources has increased considerably in recent years in an attempt to reduce greenhouse gas emissions. To mitigate the uncertainties of these sources and to balance energy production with consumption an energy storage system (ESS) based on water electrolysis to produce hydrogen is studied. It can be applied to AC microgrids where several renewable energy sources and several loads may be connected which is the focus of the study. When excess electricity production is converted into hydrogen via water electrolysis low DC voltages and high currents are applied which needs specific power converters. The use of a three-phase buck-type current source converter in a single conversion stage allows for an adjustable DC voltage to be obtained at the terminals of the electrolyzer from a three-phase AC microgrid. The voltage control is preferred to the current control in order to improve the durability of the system. The classical control of the buck-type rectifier is generally done using two loops that correspond only to the control of its output variables. The lack of control of the input variables may generate oscillations of the grid current. Our contribution in this article is to propose a new control for the buck-type rectifier that controls both the input and output variables of the converter to avoid these grid current oscillations without the use of active damping methods. The suggested control method is based on an approach using the flatness properties of differential systems: it ensures the large-signal stability of the converter. The proposed control shows better results than the classical control especially in oscillation mitigation and dynamic performances with respect to the rejection of disturbances caused by a load step.

Underground hydrogen storage (UHS) has attracted increasing attention as a promising technology for the largescale storage of renewable energy resources and the decarbonization of energy systems. This study aimed to identify critical parameters influencing UHS performance particularly the role of hydrogen conversion via in situ methanation and hydrogen recovery during production cycles. The main focus is the Lehen field in Upper Austria where a pilot hydrogen storage project was conducted under the leadership of RAG Austria AG. A layered reservoir model was developed on the basis of well-log data to simulate the field trials that occurred in 2016. A sensitivity analysis was performed with the one-parameter-at-a-time (OPAAT) method and the response surface methodology (RSM) to evaluate the impacts of different parameters on hydrogen methanation and hydrogen recovery. The RSM results indicate the activation energy as the most influential factor on methanation that accounts for ~20000 moles variation in generated methane significantly higher than the 6000 moles variance observed in OPAAT. However initial CO2 content contributes up to 15000 moles of methane gener ation as per RSM whereas OPAAT results in a larger impact of up to 32000 moles. These discrepancies demonstrate the limitations of isolated parameter analyses like OPAAT which may not accurately capture the complex interactions between factors influencing the methanation process. This research provides valuable in sights for optimizing UHS performance by emphasizing the influence of reservoir parameters on storage effi ciency. In addition a robust workflow for conducting comprehensive sensitivity analyses of UHS systems is established. By understanding these key factors the potential and predictability of large-scale UHS systems can be significantly improved.

Energy storage is essential to address the intermittent issues of renewable energy systems thereby enhancing system stability and reliability. This paper presents the design and operation optimisation of hydrogen/battery/ hybrid energy storage systems considering component degradation and energy cost volatility. The study ex amines a real-world case study which is a grid-connected warehouse located in a tropical climate zone with a photovoltaic solar system. An accurate and robust Multi-Objective Modified Firefly Algorithm (MOMFA) is proposed for the optimal design and operation of the energy storage systems of the case study. To further demonstrate the robustness and versatility of the optimisation method another synthetic case is tested for a location in a temperate climate zone that has a high seasonal mismatch. The modelling results show that the system in the tropical zone always provides a superior return when compared to a similar system in the temperate zone due to abundant solar resources. When comparing battery-only and hydrogen-only systems battery systems perform better than hydrogen systems in many situations with a higher self-sufficient ratio and net present value. However if there is high seasonal variation and a high requirement for using renewable energy (the penetration of renewable energy is >80 %) using hydrogen for energy storage is more beneficial. Furthermore the hybrid system (i.e. combining battery and hydrogen) outperforms battery-only and hydrogenonly systems. This is attributed to the complementary combination of hydrogen which can be used as a longterm energy storage option and battery which is utilised as a short-term option. This study also shows that storing hydrogen in a long-term strategy can lower component degradation enhance efficiency and increase the total economic performance of hydrogen and hybrid storage systems. The developed optimisation method and findings of this study can support the implementation of energy storage systems for renewable energy.

Underground Hydrogen Storage (UHS) as an emerging large-scale energy storage technology has shown great promise to ensure energy security with minimized carbon emission. A set of comprehensive UHS site evaluation criteria based on important factors that affect UHS performances is needed for its potential commercialization. This study focuses on the UHS site evaluation of gas mixing. The economic implications of gas mixing between injected hydrogen gas and the residual or cushion gas in a porous storage reservoir is an emerging problem for Underground Hydrogen Storage (UHS). It is already clear that reservoir scale heterogeneity such as formation structure (e.g. formation dip angle) and facies heterogeneity of the sedimentary rock may considerably affect the reservoir-scale mechanical dispersion-induced gas mixing during UHS in high permeability braided-fluvial systems (a common depleted reservoir type for UHS). Following this finding the current study uses the processmimicking modeling software to build synthetic meandering-fluvial reservoir models. Channel dimensions and the presence of abandoned channel facies are set as testing parameters resulting in 4 simulation cases with 200 realizations. Numerical flow simulations are performed on these models to investigate and compare the effects of reservoir and metre-scale heterogeneity on UHS gas mixing. Through simulation channel dimensions (reservoir-scale heterogeneity) are found to affect the uncertainty of produced gas composition due to mixing (represented by the P10-P90 difference of hydrogen fraction in a produced stream) by up to 42%. The presence of abandoned channel facies (metre-scale heterogeneity) depending on their architectural relationship with meander belts could also influence the gas mixing process to a comparable extent (up to 40%). Moreover we show that there is no clear statistical correlation between gas mixing and typical reservoir characterization parameters such as original gas in place (OGIP) average reservoir permeability and the Dykstra-Parsons coefficient. Instead the average time of travel of all reservoir cells calculated from flow diagnostics shows a negative correlation with the level of gas mixing. These results reveal the importance of 3D reservoir architecture analysis (integration of multiple levels of heterogeneity) to UHS site evaluation on gas mixing in depleted gas reservoirs. This study herein provides valuable insights into UHS site evaluation regarding gas mixing.

This paper focuses on the critical role of long-duration energy storage (LDES) technologies in facilitating renewable energy integration and achieving carbon neutrality. It presents a systematic review of four primary categories: mechanical energy storage chemical energy storage electrochemical energy storage and thermal energy storage. The study begins by analyzing the technical advantages and geographical constraints of pumped hydro energy storage (PHES) and compressed air energy storage (CAES) in high-capacity applications. It then explores the potential of hydrogen and synthetic fuels for long-duration clean energy storage. The section on electrochemical energy storage highlights the high energy density and flexible scalability of lithium-ion batteries and redox flow batteries. Finally the paper evaluates innovative advancements in large-scale thermal energy storage technologies including sensible heat storage latent heat storage and thermochemical heat storage. By comparing the performance metrics application scenarios and development prospects of various energy storage technologies this work provides theoretical support and practical insights for maximizing renewable energy utilization and driving the sustainable transformation of global energy systems.