A quantitative assessment of the hydrogen storage capacity of the UK continental shelf

Increased penetration of renewable energy sources and decarbonisation of the UK's gas supply will require large-scale energy storage. Using hydrogen as an energy storage vector, we estimate that 150 TWh of seasonal storage is required to replace seasonal variations in natural gas production. Large-scale storage is best suited to porous rock reservoirs. We present a method to quantify the hydrogen storage capacity of gas fields and saline aquifers using data previously used to assess CO₂ storage potential. We calculate a P50 value of 6900 TWh of working gas capacity in gas fields and 2200 TWh in saline aquifers on the UK continental shelf, assuming a cushion gas requirement of 50%. Sensitivity analysis reveals low temperature storage sites with sealing rocks that can withstand high pressures are ideal sites. Gas fields in the Southern North Sea could utilise existing infrastructure and large offshore wind developments to develop large-scale offshore hydrogen production.     

A review on worldwide underground hydrogen storage operating and potential fields

Overreliance on fossil fuels for human energy needs, combined with the associated negative environmental consequences in terms of greenhouse gas emissions, has shifted our focus to renewable energy sources. Hydrogen has been identified by researchers as an energy source. Hydrogen is a non-carbon-based energy resource that has the potential to replace fossil fuels. This resource is seen as an alternative fuel since it may be produced using environmentally friendly methods.Hydrogen storage is a critical component of the hydrogen economy, particularly when hydrogen utilization on a large scale is required. This paper presents a review of worldwide underground operating and potential sites to provide a clear understanding of the current status of hydrogen storage in the world.The literature survey indicated that underground geological structures have been used to successfully store hydrogen. Some of the criteria used to select these sites for underground hydrogen storage include but are not limited to geological conditions, storage location, availability of brine, presence of insoluble impurities such as dolostone, limestone, or shale, and socio-economic characteristics.The key issues with the hydrogen storage in the subsurface geological structures include but are not limited to microbial, hydrogeological, hydrodynamics, geomechanics, and geochemical facilitated by injected hydrogen which significantly impact the success and operational efficiency of the projects.     

The accuracy of hydrogen sorption measurements on potential storage materials

The most common gas phase hydrogen sorption measurement techniques used for the characterisation of potential hydrogen storage materials are the volumetric, or manometric, and gravimetric methods and temperature-programmed desorption (TPD), also known as thermal desorption spectroscopy (TDS). In this article previous work relating to the accuracy of these measurements, including some comparative studies, is reviewed, together with some relevant standards and related guidelines. The potential sources of error in hydrogen sorption measurements performed volumetrically and gravimetrically are also discussed, together with some of those related to TPD. The issues covered include sample degassing procedures, hydrogen compressibility, gas purity and differences in helium and hydrogen leak rates.     

Cavern integrity for underground hydrogen storage in the Brazilian pre-salt fields

Over the years, energy has depended on petroleum-based fuels. However, global warming and the energy crisis have drastically impacted the markets. It urges investing in renewable energy resources, such as hydrogen. Therefore, this work focuses on the hydrogen storage process in salt caverns, as these rocks have relevant properties, such as low permeability, relevant creep, and self-healing. A workflow for cavity integrity analysis is proposed. Hydrogen storage provokes variations in temperature and pressure inside the cavern. The gas thermodynamics is represented through a diabatic solution, which updates the gas pressure and temperature at each time step. The thermomechanical formulation is implemented into an in-house framework GeMA, which couples different physics. Four case studies are analyzed, and the discussions compared mechanical and thermomechanical models. Results demonstrate the importance of thermal effects, as temperature amplitudes may compromise rock integrity, for instance, inducing tensile stresses and affecting permeability.     

Technical potential of salt caverns for hydrogen storage in Europe

The role of hydrogen in a future energy system with a high share of variable renewable energy sources (VRES) is regarded as crucial in order to balance fluctuations in electricity generation. These fluctuations can be compensated for by flexibility measures such as the expansion of transmission, flexible generation, larger back-up capacity and storage. Salt cavern storage is the most promising technology due to its large storage capacity, followed by pumped hydro storage. For the underground storage of chemical energy carriers such as hydrogen, salt caverns offer the most promising option owing to their low investment cost, high sealing potential and low cushion gas requirement. This paper provides a suitability assessment of European subsurface salt structures in terms of size, land eligibility and storage capacity. Two distinct cavern volumes of 500,000 m³ and 750,000 m³ are considered, with preference being given for salt caverns over bedded salt deposits and salt domes. The storage capacities of individual caverns are estimated on the basis of thermodynamic considerations based on site-specific data. The results are analyzed using three different scenarios: onshore and offshore salt caverns, only onshore salt caverns and only onshore caverns within 50 km of the shore. The overall technical storage potential across Europe is estimated at 84.8 PWh_H2, 27% of which constitutes only onshore locations. Furthermore, this capacity decreases to 7.3 PWh_H2 with a limitation of 50 km distance from shore. In all cases, Germany has the highest technical storage potential, with a value of 9.4 PWh_H2, located onshore only in salt domes in the north of the country. Moreover, Norway has 7.5 PWh_H2 of storage potential for offshore caverns, which are all located in the subsurface of the North Sea Basin.     

The potential of hydrogen storage in depleted unconventional gas reservoirs: A multiscale modeling study

Subsurface energy storage in depleted petroleum reservoirs is a promising technique to balance and optimize the utilization of energy resources. In this work, we numerically explore the possibility of storing excessive hydrogen gas in depleted unconventional gas reservoirs. Our study is a multiscale analysis. From the molecular (pore) scale, we investigate the thermodynamics and transport mechanism of the hydrogen gas in the nanopores of the unconventional reservoirs. Then based on the results of the pore scale, we conduct reservoir-scale simulations to quantitatively investigate the preferred cycling pressure, the effective fraction of cushion gas and the amount of storage capacity of unconventional reservoirs. We have discovered that, compared to conventional gas reservoirs, hydrogen stored in unconventional reservoirs maintains higher purity because of the differential adsorption effect of the nanopores. This feature makes depleted unconventional gas reservoirs appealing candidates for underground storage of the hydrogen gas.     

Modeling phase equilibrium of hydrogen and natural gas in brines: Application to storage in salt caverns

In this work, the e-PPC-SAFT equation of state has been parameterized to predict phase equilibrium of the system H₂ + CH₄ + H₂O + Na⁺Cl^? in conditions of temperature, pressure and salinities of interest for gas storage in salt caverns. The ions parameters have been adjusted to match salted water properties such as mean ionic coefficient activities, vapor pressures and molar densities. Furthermore, binary interaction parameters between hydrogen, methane, water, Na⁺ and Cl^? have been adjusted to match gas solubility data through Henry constant data. The validity ranges of this model are 0–200 °C for temperatures, 0–300 bar for pressures, and 0 to 8 mol_NaCl/kg_H2O for salinities. The e-PPC-SAFT equation of state has then been used to model gas storage in salt caverns. The performance of a storage of pure methane, pure hydrogen and a mixture methane + hydrogen have been compared. The simulations of the storage cycles show that integrating up to 20% of hydrogen in caverns does not have a major influence on temperature, pressure and water content compared to pure methane storage. They also allowed to estimate the thermodynamic properties of the system during the storage operations, like the water content in the gaseous phase. The developed model constitutes thus an interesting tool to help size surface installations and to operate caverns.     

Seasonal hydrogen storage in a depleted oil and gas field

Hydrogen storage is essential in hydrogen value chains and subsurface storage may be the most suitable large-scale option. This paper reports numerical simulations of seasonal hydrogen storage in the Norne hydrocarbon field, offshore Norway. Three different storage schemes are examined by injecting pure hydrogen into the gas-, oil-, and water zones. Implementation of four annual withdrawal-injection cycles followed by one prolonged withdrawal period show that the thin gas zone is a preferred target with a final hydrogen recovery factor of 87%. The hydrogen distribution in the subsurface follow the geological structures and is restricted by fluid saturation and displacement efficiencies. Case studies show that the pre-injection of formation gas as a cushion gas efficiently increases the ultimate hydrogen recovery, but at the cost of hydrogen purity. The injection of 30% hydrogen-formation gas mixture results in a varying hydrogen fraction in the withdrawn gas. An alternative well placement down the dipping structure shows lower storage efficiency.     

Exporting the “Norwegian Model”: The effect of administrative design on oil sector performance

Norway has administered its petroleum resources using three distinct government bodies: a national oil company engaged in commercial hydrocarbon operations; a government ministry to direct policy; and a regulatory body to provide oversight and technical expertise. Norway's relative success in managing its hydrocarbons has prompted development institutions to consider whether this “Norwegian Model” of separated government functions should be recommended to other oil-producing countries. By studying ten countries that have used widely different approaches in administering their hydrocarbon sectors, we conclude that separation of functions is not a prerequisite to successful oil sector development. Countries where separation of functions has worked are characterized by the combination of high institutional capacity and robust political competition. Unchallenged leaders often appear able to adequately discharge commercial and policy/regulatory functions using the same entity, although this approach may not be robust against political changes. Where institutional capacity is lacking, better outcomes may result from consolidating commercial, policy, and regulatory functions until such capacity has further developed. Countries with vibrant political competition but limited institutional capacity pose the most significant challenge for oil sector reform: Unitary control over the sector is impossible but separation of functions is often difficult to implement.     

The effect of ball-milling gas environment on the sorption kinetics of MgH2 with/without additives for hydrogen storage

A study of the effect of the ball-milling gas environment on the kinetic enhancement of MgH₂ with different additives was conducted using argon and hydrogen. The as-sourced MgH₂ was milled for 20 h and then milled for a further 2 h after adding 1–2 mol% of one of the additives titanium isopropoxide, niobium oxide or carbon buckyballs, varying the gas environment for both ball-milling stages. The milling environment had little or no effect on the desorption kinetics in most cases. However, in some cases, the absorption uptake differed by up to 2 wt%, depending on the gas used_. This effect was not consistent among the composite samples surveyed, demonstrating the importance of reporting all information about the ball-milling processes used, including the gas environment.     

Algorithm for optimal pairing of res and hydrogen energy storage systems

The global climate and environmental crisis dictate the need for the development and implementation of environmentally friendly and efficient technical solutions, for example, generation based on renewable energy sources. However, the annually increasing demand for electricity (according to the forecasts of the U.S. Energy Information Administration, the amount of energy consumed for the period 2006–2030 will increase by 44 %) cannot be fully provided by alternative energy. The main reason is not so much the high cost of these technologies, like unstable power generation, which determines the need for an additional reserve of regulated power.The solution to this problem can be the combined use of generation based on renewable energy sources with energy storage units of large capacity. Currently, a promising direction is the use of excess electricity for the production of hydrogen and its further accumulation in hydrogen storage. In this case an additional energy can be generated using industrial fuel cells (electrochemical generators) to compensate for the power shortage.At the same time, the distinctive advantage of hydrogen energy storage systems lies in the ability to accumulate a large amount of energy for long periods of time. This fact makes it possible to increase the reliability of the functioning of the electric power system, to provide power supply with a sufficiently long interruption (in case of faults) or allocation for isolated operation.With an increase in the unit capacity and the share of renewable generation in the total installed capacity, researches that aimed to systematic analysis of the impact of the implemented generation unit and the energy storage system on the parameters of the mode of the electric power system become more relevant. There are a number of tasks can be noted related to determining the optimal location and size of the generation unit and energy storage systems being implemented in terms of reducing power losses and maintaining an appropriate voltage level in the nodes of the electric power system. In this article, a variant of solving the optimization task for a typical 15-bus IEEE scheme is presented by means of software calculation using the bubble sorting method. To achieve this goal, the following tasks were solved: the objective function, which indicates the optimal location and size of the generation unit, and constraints, for example, the available deviation of voltage level, were formed; the software implementation of the algorithm for calculating power flows and power losses using the bubble sorting method was carried out. The results of the work of the program code for two scenarios are presented: for instance, installation of one renewable generation unit with a different range of possible capacities, and are compared with the data obtained in the MATLAB/Simulink software package.     

Thermodynamics analysis of hydrogen storage based on compressed gaseous hydrogen,liquid hydrogen and cryo-compressed hydrogen

Safe, reliable, and economic hydrogen storage is a bottleneck for large-scale hydrogen utilization. In this paper, hydrogen storage methods based on the ambient temperature compressed gaseous hydrogen (CGH₂), liquid hydrogen (LH₂) and cryo-compressed hydrogen (CcH₂) are analyzed. There exists the optimal states, defined by temperature and pressure, for hydrogen storage in CcH₂ method. The ratio of the hydrogen density obtained to the electrical energy consumed exhibits a maximum value at the pressures above 15 MPa. The electrical energy consumed consists of compression and cooling down processes from 0.1 MPa at 300 K to the optimal states. The recommended parameters for hydrogen storage are at 35–110 K and 5–70 MPa regardless of ortho-to parahydrogen conversion. The corresponding hydrogen density at the optimal states range from 60.0 to 71.5 kg m⁻³ and the ratio of the hydrogen density obtained to the electrical energy consumed ranges from 1.50 to 2.30 kg m⁻³ kW⁻¹. While the ortho-to para-hydrogen conversion is considered, the optimal states move to a slightly higher temperatures comparing to calculations without ortho-to para-hydrogen conversion.     

Impacts of the subsurface storage of natural gas and hydrogen mixtures

The subsurface storage of hydrogen (H₂) provides a potential solution for load-balancing of the intermittent electricity production from renewable energy sources. In such technical concept, surplus electricity is used to power electrolyzers that produce H₂, which is then stored in subsurface formations to be used at times when renewable electricity is not available. Blending H₂ with natural gas (NG) for injection into depleted gas/oil reservoirs, which are already used for NG storage, is considered a good option due to the lower initial capital cost and investment needed, and potential lower operating costs. In this study, the potential impact of storing a mixture of H₂ and NG in an existing NG storage field was investigated. Relevant reservoir, caprock and cement samples from a NG storage formation in California were characterized with respect to their permeability, porosity, surface area, mineralogy and other structural characteristics, before and after undergoing 3-month incubation experiments with H₂/NG gas mixtures at relevant temperature and pressure conditions. The results indicated relatively small changes in porosity and mineralogy due to incubation. However, the observed changes in permeability were more dramatic. In addition, polymeric materials, similar to those used in NG storage operations were also incubated, and their dimensions were measured before and after incubation. These measurements indicated swelling due to the exposure to H₂. However, direct evidence of geochemical reactions involving H₂ was not observed.     

Ammonia and related chemicals as potential indirect hydrogen storage materials

Energy production and combating climate change are among some of the most significant challenges we are facing today. Whilst the introduction of a hydrogen economy has its merits, the associated problems with on-board hydrogen storage are still a barrier to implementation. Ammonia and related chemicals may provide an alternative energy vector. Besides ammonia and metal amine salts, some other ammonia related materials such as hydrazine, ammonia borane, ammonia carbonate and urea also have the potential for use as alternative fuels. These materials conform to many of the US DOE targets for hydrogen storage materials.     

Liquid hydrogen,methylcyclohexane, and ammonia as potential hydrogen storage: Comparison review

Among the several candidates of hydrogen (H₂) storage, liquid H₂, methylcyclohexane (MCH), and ammonia (NH₃) are considered as potential hydrogen carriers, especially in Japan, in terms of their characteristics, application feasibility, and economic performance. In addition, as the main mover in the introduction of H₂, Japan has focused on the storage of H₂, which can be categorized into these three methods. Each of them has advantages and disadvantages compared to the other. Liquid H₂ faces challenges in the huge energy consumption that occurs during liquefaction and in the loss of H₂ through boil-off during storage. MCH has its main obstacles in requiring a large amount of energy in dehydrogenation. Finally, NH₃ encounters high energy demand in both synthesis and decomposition (if required). In terms of energy efficiency, NH₃ is predicted to have the highest total energy efficiency, followed by liquid H₂, and MCH. In addition, from the calculation of cost, NH₃ with direct utilization (without decomposition) is considered to have the highest feasibility for massive adoption, as it shows the lowest cost (20–22 JPY·Nm³-H₂ in 2050), which is close to the government target of H₂ cost (20 JPY·Nm³-H₂ in 2050). However, in the case that highly pure H₂ (such as for fuel cell) is needed, liquid H₂ looks to be promising (24–25 JPY·Nm³-H₂ in 2050), compared with MCH and NH₃ with decomposition and purification.     

Energy budget of the thermal gradient in the Southern Brazilian continental shelf

Various forms of energy conversion have been examined over the years and the energy of thermal gradients currently operating in some regions of the world has been studied. The Southern Brazilian Continental Shelf has high spatial and temporal temperature variability, indicating the need for a climatological analysis to identify the regions with the largest energy budgets. This region was shown to have a large energy budget through the analysis of sea surface temperature modelling data over 14 years. Based on the seasonality, the most suitable area for using an OTEC facility was identified. A numerical module forced with the monthly averaged modelling data was developed in order to estimates the thermal energy conversion from the ocean. The results show that there is a low sensitivity of the thermocline and thermal gradient associated with the change of seasons and oceanic features observed in this region. The theoretical maximum power produced can reach up to 121.9 MW and the average over the studied period was approximately 94.3 MW considering a punctual extraction spot. A simulated conversion site placed where there was greatest viability revealed that the average standard thermal gradient is 0.17 °C/m along the vertical column (545 m) from the sea.     

Three-dimensional modeling and simulation of hydrogen absorption in metal hydride hydrogen storage vessels

In this paper, a three-dimensional hydrogen absorption model is developed to precisely study the hydrogen absorption reaction and resultant heat and mass transport phenomena in metal hydride hydrogen storage vessels. The 3D model is first experimentally validated against the temperature evolution data available in the literature. In addition to model validation, the detailed 3D simulation results show that at the initial absorption stage, the vessel temperature and H/M ratio distributions are uniform throughout the entire vessel, indicating that hydrogen absorption is very efficient early during the hydriding process; thus, the local cooling effect is not influential. On the other hand, non-uniform distributions are predicted at the subsequent absorption stage, which is mainly due to differential degrees of cooling between the vessel wall and core regions. In addition, a parametric study is carried out for various designs and hydrogen feed pressures. This numerical study provides a fundamental understanding of the detailed heat and mass transfer phenomena during the hydrogen absorption process and further indicates that efficient design of the storage vessel and cooling system is critical to achieve rapid hydrogen charging performance.     

Cesium hydrazinidoborane,the last of the alkali hydrazinidoboranes,studied as potential hydrogen storage material

Alkali hydrazinidoboranes MN₂H₃BH₃ (M = Li, Na, K, Rb) have been developed for hydrogen storage. To complete the family of MN₂H₃BH₃, we focused on cesium hydrazinidoborane CsN₂H₃BH₃ (CsHB). It has been synthesized by reaction of cesium with hydrazine borane (N₂H₄BH₃) at −20 °C under inert atmosphere, and it has been characterized. A crystalline solid (monoclinic, s.g. P2₁ (No. 4)) has been obtained. Its potential for hydrogen storage has been studied by combining different techniques. It was found that, under heating at constant heating rate (5 °C min⁻¹) or at constant temperature (e.g. 120 °C), CsHB decomposes rather than it dehydrogenates. It releases several unwanted gaseous products (e.g. NH₃, B₂H₆) together with H₂, and transforms into a residue that poses safety issues because of shock-sensitivity and reactivity towards O₂/H₂O. Though the destabilization brought by Cs⁺ onto the anion [N₂H₃BH₃]⁻ has been confirmed, the effect is not efficient enough to avoid the aforementioned drawbacks. All of our results are presented herein and discussed within the context of solid-state hydrogen storage.