Search Results (182)

Park-level integrated energy systems with high shares of wind and photovoltaic power face pronounced seasonal source–load mismatches, renewable energy curtailment, and low-carbon operation challenges. This paper proposes a capacity planning method considering seasonal salt-cavern hydrogen storage and adaptive representative days. An electricity–heat–cooling–hydrogen coupled system is established by integrating renewable generation, conventional conversion units, short-term storage, electrolyzers, fuel cells, and salt-cavern hydrogen storage, together with waste-heat recovery and tiered carbon trading. To represent interseasonal hydrogen transfer under representative-day modeling, a seasonal hydrogen inventory formulation based on weighted net hydrogen changes is developed, considering cushion gas, storage bounds, injection and withdrawal efficiencies, and flow-rate limits. A season-specific adaptive K-medoids method based on CRITIC evaluation is further proposed to determine the number of representative days, while zero-weight extreme days are introduced to verify capacity feasibility under boundary conditions. The optimization objective is to minimize annualized total cost. Case studies show that removing seasonal hydrogen storage increases total system cost by 23.63%, raises wind and photovoltaic curtailment from 1.81% to 13.09%, and increases carbon emissions by 13.74%. The proposed method improves economic, renewable-energy-utilization, and low-carbon performance. Full article

As critical infrastructure for carbon capture, utilization, and storage (CCUS) and large-scale energy storage, subsurface salt caverns are seriously challenged by fluid-induced sediment mobilization during the supplementary debrining. Conventional bulk resin consolidation often causes severe viscous fingering, uneven consolidation, and pore clogging under hypersaline conditions. Here, we develop a foam-templated hybrid polymer gel co-stabilized by silica nanoparticles, polyvinyl alcohol, and the zwitterionic surfactant. The key novelty is the use of foam as a transient transport template that redistributes the resin phase and promotes selective cementation at grain-contact points instead of indiscriminate pore filling. This nano-reinforced gel system remained stable under hypersaline conditions (24% NaCl), and temperatures ranging from 20–80 °C. Micro-CT analysis showed that this selective templating preserved an interconnected pore network with a porosity above 45% and a CT-derived permeability of approximately 1.18 D, while reducing binder consumption by 55.6% relative to bulk resin injection. Crucially, a 1:200 geometrically scaled, velocity-matched pilot model demonstrated that this gel strategy limited sediment entrainment below 0.5% and reduced fluid discharge by 45.9%. These results establish a material-efficient consolidation strategy that combines sediment stabilization with permeability preservation, providing a promising solution for safer supplementary debrining in salt-cavern CCUS and energy-storage operations. Full article

Underground storage of green hydrogen is a strategic enabler of large-scale renewable deployment, but its feasibility rests on a hard problem: keeping a small, highly mobile molecule confined underground for decades without safety or environmental risk. This critical review examines the containment mechanisms of hydrogen across underground storage types, focusing on geological barriers, well integrity and sealing materials. We evaluate the containment capabilities of salt cavities, deep aquifers and depleted reservoirs, with particular attention to the viscoplastic, self-healing properties of salt that promote confinement, and to the vulnerabilities of well infrastructure and salt–cement interfaces. Emerging alternatives, including lined rock caverns and repurposed abandoned mines, are assessed alongside their distinct operating configurations and use cases. Leakage mechanisms including diffusion, advection, microcracking, cement degradation and hydrogen–material interactions are analysed alongside geomechanical modelling, microbial activity, monitoring strategies, regulatory frameworks, and techno-economic and environmental considerations, including the integration of carbon capture, utilisation and storage (CCUS) with underground hydrogen storage. Well integrity emerges as the dominant risk factor across storage types. The review concludes with design criteria, monitoring priorities and research needs to guide the safe, sustainable deployment of underground hydrogen storage, providing a scientific foundation for future numerical and experimental work on storage tightness. Full article

Lined rock caverns offer a promising option for underground hydrogen, helping to mitigate renewable intermittency and enhance system stability. Considering the geological characteristics of hard rock formations in Southern Ontario, Canada, this study establishes a thermo–gas–mechanical coupled framework that incorporates hydrogen mass and energy evolution in the cavern, gas–wall convective heat exchange, dynamic cavern-volume feedback, and the deformation behaviour of the sealing layer, concrete lining, and surrounding rock. The influences of cavern geometry, sealing material, and in situ stress on the short–term thermodynamic and mechanical responses are further examined. The results show that hydrogen temperature and pressure exhibit clear stage–dependent evolution during the charging–storage–discharging cycle. The comparison between the first and 20th operating cycles indicates that repeated operation mainly causes a moderate adjustment of the cyclic thermal state and temperature–pressure baseline, without changing the overall stage–dependent response pattern. During charging, temperature and pressure increase simultaneously; during storage, both gradually decrease as thermal energy is transferred to the cavern wall; and during discharging, expansion causes pronounced cooling and depressurization, followed by gradual recovery driven by heat transfer from the surrounding rock. Cavern geometry significantly affects stress redistribution around the cavern. The circular cavern shows a relatively uniform stress distribution, whereas the arched cavern is more prone to local stress concentration near the sidewall–floor transition zone. The sealing material mainly influences gas temperature fluctuations through its thermal conductivity. The fibre–reinforced plastic (FRP) sealing layer amplifies thermal fluctuations during cyclic operation, whereas the steel sealing layer promotes heat dissipation through the lining and surrounding rock, thereby moderating cavern–gas temperature variations. In situ stress difference further controls the directional distribution of stresses around the cavern. As the minimum horizontal principal stress increases, compressive stress concentration at the crown and invert becomes stronger, while relative stress release occurs near the sidewalls. These findings provide a thermo–mechanical basis for preliminary cavern–geometry design, comparison of sealing–layer thermal performance, and assessment of in situ stress adaptability for lined rock cavern hydrogen storage in Southern Ontario. Full article

Pumped hydro storage is a well-established and reliable form of energy storage, with construction scale expanding steadily in recent years. Underground cavern excavation is an indispensable part of pumped storage construction, while sustained cavern inflow poses potential threats to engineering and regional water security. This study first summarizes the hydrochemical characteristics of cavern inflow from 62 pumped-storage projects in China. Combining field investigations, water pressure tests, hydrochemical analyses, and multi-method inflow forecasting, the study further discusses the cavern inflow features of two typical projects under different climatic environments. The results indicate that across the 62 projects, total dissolved solids (TDS) in inflow water range from 21.0 to 4270.7 mg/L, with pH values of 6.7–8.3, and are dominated by HCO₃-Ca type. Moving from humid toward arid regions, TDS shows a continuous increase, while pH exhibits no significant variation. At the Shanshan site, controlled by evaporation, silicates weathering and evaporite dissolution, cavern inflows are dominated by high-salinity SO₄-Mg type water with pronounced SO₄²⁻ enrichment. Predicted inflows of the underground powerhouse and water conveyance tunnels are 1247.96–5542.97 m³/d and 105.85–211.69 m³/d, respectively. The Ningshanbei site, located in the humid area, is characterized by low-salinity HCO₃-Ca freshwater controlled by carbonate dissolution, with a high conveyance system inflow of 2914.71–3413.91 m³/d. The two sites differ markedly in recharge conditions, inflow characteristics, and water quality, requiring site-specific water management. This study provides engineering references for inflow hazard control, groundwater resource management, and ecological protection in pumped-storage projects across different climatic zones. Full article

In salt cavern compressed air energy storage (CAES) systems, slag particles entrained by high-pressure airflow can cause pipeline wear and flow instability, posing challenges to long-term operational safety. However, direct experimental studies are constrained by high-pressure, large-scale conditions and transient multiphase flow complexities. This study uses Fluent, a numerical simulation method based on gas–solid two-phase flow theory, to investigate the flow characteristics, particle dynamics, and erosion behavior in the above-ground pipeline of CAES system. Results reveal uneven gas velocity distribution, with the lowest flow (≤2.3 (m/s)) in the main pipeline favoring particle deposition, and complex vortex structures at branch connections. Particles accumulate on the outer wall of 90° elbows due to centrifugal effects, leading to localized erosion, with severe wear occurring at impact angles of 20–30°. Over a 30-year operational cycle, the predicted maximum wear depth is 0.38 mm, which remains below the existing protective cladding thickness of 0.5 mm. The findings not only provide a theoretical basis and design insights for optimizing wear protection strategies, but also hold positive implications for enhancing the economic sustainability and environmental benefits of large-scale energy storage systems. Full article

Reliable prediction of final cavern responses is required for rapid screening of solution-mined salt caverns used in large-scale underground energy storage. Final cavern volume and maximum radius jointly control storage performance and geometric safety, but their simultaneous and physically consistent prediction remains challenging. In this study, a lightweight physics-guided neural network (LPGNN) was proposed for dual-target prediction of these two design-critical responses. The 25 recorded stage-wise construction variables were screened to retain 13 varying independent variables and are supplemented by five nonredundant process–geometric features describing leaching-time allocation, mean depth configuration, and staged depth adjustment. A shared residual encoder and two target-specific heads were trained using Huber loss and original-scale relative error for data fitting and a soft constraint related to source-defined cavern volume-coefficient consistency. The framework was evaluated using 1253 simulated five-stage solution-mining cases. On the independent test set, the LPGNN achieved mean absolute percentage error (MAPE) of 1.4779% for cavern volume and 2.8746% for maximum radius, with corresponding R² values of 0.9506 and 0.8602, respectively. Correlation, Mantel-test, and feature-response analyses indicate that cavern volume is mainly associated with the overall leaching scale and vertical-control configuration, whereas maximum radius is more sensitive to staged depth adjustment and localized radial development. These results suggest that the proposed LPGNN can serve as an accurate and physically constrained surrogate for preliminary comparison and rapid screening of solution-mined salt-cavern construction schemes. Full article

The sealing performance of compressed air energy storage (CAES) caverns represents a multi-physics challenge involving coupled thermal–hydraulic–mechanical processes, characterized by complex interacting factors. As a critical determinant of the long-term operational efficiency of CAES facilities, this study developed a fiber-reinforced cement-based composite sealing material through systematic orthogonal experiments investigating four key parameters: water–cement ratio, sand ratio, fly ash–silica fume content, and basalt fiber content. An optimized mixture was formulated with a water–cement ratio (0.36), sand ratio (42%), fly ash–silica fume content (22%), and basalt fiber content (1.0%). Under this optimal mix proportion, the measured permeability coefficient of the sealing layer is 1.92 × 10⁻¹³ cm/s, and the uniaxial compressive strength and tensile strength are 37 MPa and 3.9 MPa, respectively, with a corresponding elastic modulus of 18 GPa. Meanwhile, the P-wave velocity is approximately 2823 m/s, and the porosity is 0.15, achieving balanced performance in permeability, strength, and porosity. The material was validated in a CAES physical model through gas charge–discharge tests under various operational scenarios for the composite sealing layer-lining-surrounding rock system. Full article

Sandstone–marble waste powder concrete composite structures serve as common load-bearing systems in tunnels, underground caverns, and similar engineering projects, where the interface roughness characteristics directly govern their overall stability and service safety. To investigate the influence of interface roughness on the failure behavior of the composite, four groups of sandstone–concrete composite specimens made with marble waste powder concrete were prefabricated with different joint roughness coefficients (JRC = 0, 7.84, 17.99, 20.79). The concrete matrix was prepared with marble waste powder incorporated at 25 wt% of the total binder, corresponding to 20.45 wt% of the total mixture, and the water-to-binder ratio was 0.20. Uniaxial compression tests were conducted with synchronous acoustic emission (AE) and digital image correlation (DIC) monitoring to examine the roughness-dependent mechanical response, energy evolution, damage activity, and strain localization of the composites. The results show that the peak stress and elastic modulus of the composite increase continuously with increasing JRC. When JRC increases from 0 to 20.79, the peak stress increases by 170.3% and the elastic modulus increases by 201.1%. The energy evolution mechanism transitions from progressive damage with gradual energy dissipation at low roughness to a three-stage mode at high roughness, characterized by initial frictional energy dissipation, intermediate energy storage, and rapid elastic energy release and dissipated energy increase near failure. DIC results further reveal that increasing interface roughness suppresses interfacial shear slip and promotes tensile-dominated strain localization, whereas excessive roughness may induce local stress concentration around asperities and increase the tendency toward abrupt post-peak instability, the failure mode changes from mixed tensile–shear failure with obvious interfacial slip to tensile-dominated failure. Full article

At present, research on the long-term stability of multi-cavern coordinated injection–production operations for salt cavern compressed air energy storage (CAES) remains limited. Large-capacity energy storage utilizing multiple interconnected salt caverns has become an inevitable development trend for modern CAES power stations, highlighting the necessity and importance of stability evaluation and design optimization for underground salt cavern storage clusters. Based on the Anning 350 MW CAES demonstration project, this paper takes the abandoned salt caverns of the project as research objects. A three-dimensional geological and cavern model is established using the FLAC3D numerical simulation method, and stability analysis is carried out under static conditions and three long-term gas injection and production scenarios (the pressure conditions are provided by ground-based equipment). The characteristics of the plastic zone, displacement, stress distribution, and volume shrinkage of the caverns are systematically investigated. The results show that under static conditions, the internal pressure significantly controls the development of the plastic zone, and the caverns are generally stable at pressures above 4 MPa. During long-term operation, the plastic zones of each cavern gradually expand, displacements accumulate continuously, and stresses tend to stabilize after an initial accumulation period. After 30 years of operation, no through-going plastic zones appear in any cavern, and all volume shrinkage rates are below 30%. Among the three cases, Case 1 exhibits the best stability, while enhanced monitoring is required for local high-stress regions in Case 3. This study verifies that the salt cavern development for the Anning CAES project is safe and controllable during long-term operation. The layout spacing of caverns is reasonably designed and fully satisfies the stability requirements of salt cavern CAES power stations. The research results can provide a technical guarantee for the construction of the first CAES power station in Yunnan Province and also offer a reliable reference for the design and construction of similar multi-cavity salt cavern CAES projects. Full article

Hydrogen (H₂) is becoming a meaningful way to store energy for long-term use and support thorough decarbonization in systems that use renewable energy. Underground hydrogen storage (UHS) has strategic benefits over above-ground systems because it can hold large volumes, is contained by geology, and is cheap to operate in cycles. This review compares four key geological formations for underground hydrogen storage (UHS): salt caverns, lined rock caverns, depleted hydrocarbon reservoirs, and saline aquifers. Each system is evaluated based on storage mechanisms, efficiency, safety, technological maturity, and economic feasibility. This review also introduces a unified cross-media evaluation framework, a TRL-risk matrix, a technology development roadmap, and novel insights into AI-based monitoring, offering prescriptive guidance for large-scale UHS implementation. Salt caverns have high injectivity, maintain their purity, and undergo 6 to 12 cycles per year at pressures of 60 to 180 bar; however, they are only found in certain places. Lined rock caverns can be built anywhere, but sealing and economic issues make them difficult to use. Depleted hydrocarbon reservoirs with TWh-scale capacity and already built infrastructure. Saline aquifers, on the other hand, have the most potential in the world but need enhanced management of microbiological responses and cushion gas optimization. A synthesis of current studies highlights key research gaps in cyclic geomechanics, hydrogen–rock–microbe interactions, and liner performance for high-pressure storage. The review concludes with techno-economic and safety considerations and identifies future directions for deploying geological UHS as a critical component of a net-zero hydrogen economy. Full article

The underground caverns of pumped-storage power stations generally feature large inclination angles. During the bottom-up oblique excavation by hard-rock Tunnel Boring Machines (TBMs), the Anti-Back-Slip (ABS) support system is the core device ensuring safe operations. Specifically, the synchronization of the multiple hydraulic cylinders within the ABS system is a critical factor determining the stability and safety of the TBM. Therefore, this paper designs a hydraulic control system for the ABS device and proposes an adjacent cross-coupling synergistic control strategy based on adaptive backstepping. This strategy innovatively integrates an adaptive backstepping control law into the adjacent cross-coupling topology to achieve high-precision multi-cylinder control. Utilizing the AMESim-Simulink platform, high-fidelity co-simulations are conducted under both uniform and eccentric load conditions. The results demonstrate that under nominal conditions, the proposed algorithm exhibits asymptotic convergence at the mathematical level. The system maintains robust stability under dynamic excitations. When subjected to sudden asymmetric eccentric loads of 1.0–2.0 times, the system prevents tracking divergence and limits the maximum multi-cylinder synchronization error to within 1.82 mm. This research satisfies the requirements for synchronous control and provides a theoretical and engineering reference for the disturbance-rejection synergy of inclined shaft TBM support systems. Full article

Against the background of global carbon reduction initiatives and ongoing energy transition, this study addresses the technical challenges of constructing salt cavern storage facilities in bedded salt formations. Typical bedded salt rocks in Southwest China were taken as the research object, and systematic core sampling and multi-dimensional laboratory tests were conducted to investigate their geomechanical and petrophysical properties. The tests included mechanical experiments such as direct shear, uniaxial and triaxial compression, as well as physical property measurements including permeability, porosity, SEM, XRD, and mercury intrusion porosimetry (MIP). The results show that halite exhibits excellent plasticity and tight sealing performance, interlayers have high compressive strength, and mudstone is characterized by significant brittleness. All lithologies possess low permeability and dense internal structures. For this reason, they are well suited for salt cavern energy storage utilization. Furthermore, the research findings provide key basic data and a solid scientific basis. This study supports the construction of salt cavern gas storage and compressed air energy storage (CAES) plants in bedded salt rock areas. Full article

Building underground water-sealed oil storage (UWSOS) caverns on islands poses a potential risk of seawater intrusion. As UWSOS is mostly constructed within rock masses, research on seawater intrusion through rock fractures holds important engineering value. This study combines single-fracture model tests with numerical simulations to investigate patterns of seawater intrusion in fractured rocks. Results show that, due to the density difference between seawater and freshwater, a saltwater wedge forms in coastal zones. Under tidal action, an upper saltwater plume forms in the intertidal zone, with its scale positively correlated with tidal range. After cavern excavation, the saltwater–freshwater transition zone widens, and seawater gradually intrudes from the cavern bottom. The upper saltwater plume evolves into a “saltwater tongue” during intrusion, with a growth rate ranging from 921.89% to 5691.52%, while the lower saltwater wedge moves landward by 37.86% to 82.65%. The saltwater tongue scale increases with tidal amplitude, but the lower wedge scale shrinks. With the horizontal water curtain installed, the saltwater wedge area decreases by 45.42% to 57.33%; in contrast, installing a vertical water curtain can effectively block seawater intrusion. These results provide an important experimental foundation for seawater intrusion research in island UWSOS caverns. Full article

Salt cavern Compressed Air Energy Storage (CAES) is one of the critical technologies for energy storage and an important infrastructure supporting the construction of new power systems and facilitating the achievement of the dual carbon goals. The salt rock resources in China are primarily composed of continental strata salt rocks, characterized by high heterogeneity, well-developed thin-layer interbedding, dissolution resistance among different lithologies, and significant creep variations. These features, to some extent, limit the improvement of wellbore construction accuracy, the reliability of abandoned well sealing, the safety of natural gas storage operations, and enhancements in gas injection–brine displacement efficiency. This study takes the continental bedded salt rock in the Dawenkou Basin as the research object and adopts a method combining theoretical analysis and field engineering verification to improve the systematic construction technology system, covering the whole process of drilling engineering, abandoned well plugging, the design of an injection and brine extraction device, and gas injection and brine drainage. The research results optimize four key technologies, including precise wellbore trajectory control, dual-section milling, and multi-stage redundant plugging of abandoned wells and long-term anti-corrosion completion with laser cladding, and dual-mode adaptive gas injection and brine drainage, and improve the technical system from wellbore construction to salt cavity formation. This study can provide valuable theoretical references and engineering demonstration guidance for underground space development projects in similar salt basins in China. Full article