Search Results (187)

Modern power systems increasingly depend on energy storage devices to manage fluctuations in renewable generation and load demand. Coordinating multiple heterogeneous storage units in a grid-level system while enforcing individual state-of-charge (SoC) limits constitutes a complex, high-dimensional control problem that cannot be resolved by conventional proportional-sharing schemes. This work formulates the Distributed Optimal Energy Management (DOEM) problem for a grid comprising n parallel storage units with power-dependent efficiency and heterogeneous capacities. Optimality conditions are derived using Pontryagin’s Minimum Principle (PMP) and a smooth penalty function is introduced to handle hard SoC constraints without state-space discretisation. For the practically important class of lossless storage devices, an explicit closed-form control law is obtained, in which each unit is dispatched proportionally to its storage capacity. Numerical validation is performed on the Israeli power grid, modelling three pumped-hydro systems with a combined capacity of 8.0 GWh, using MATLAB/Simulink R2018b. Across the base net-load scenario and four additional load profiles, the cost achieved by the proposed method matches the dynamic programming (DP) benchmark within 1.1%, while the maximum state-of-charge violation is limited to 0.64% of total capacity at the default penalty setting. Computationally, the proposed update requires only 2.21 s for nine storage units compared to 59.30 s for DP, a 26.8-fold speedup, and scales with $O\left(n\right)$ arithmetic operations per time step. The results confirm a clear pathway to optimal, safe, and scalable real-time control of large-scale heterogeneous energy storage ensembles. Full article

As Cuba advances toward ambitious renewable energy targets, large-scale energy storage is essential to ensure grid stability and operational flexibility. Pumped Hydro Energy Storage (PHES) is the most mature technology for providing long-duration storage. This study proposes an integrated GIS-based screening and engineering validation methodology for PHES site selection and presents the first academic application of the Australian National University (ANU) Global Pumped Hydro Atlas to the Cuban context. Rather than replacing historical engineering studies, the proposed methodology complements them through automated geospatial analysis, local infrastructure assessment, environmental screening, and engineering validation. The GIS analysis identified 92 potential off-river closed-loop PHES sites across Cuba, including 14 sites in the 500 GWh storage class and 78 sites in the 150 GWh storage class, substantially expanding the national inventory. Comparison between the GIS-derived candidates and historical investigations demonstrates strong agreement between both approaches, while the Mayarí project serves as a representative case study for local validation. The results confirm significant PHES potential distributed across Cuba’s three main mountainous regions, with several sites exhibiting favourable hydraulic heads and cost classifications. The proposed methodology provides a transferable framework for integrating legacy engineering knowledge with modern GIS-based planning tools in islanded and developing power systems while highlighting the need for supportive regulatory frameworks to accelerate future PHES deployment. Full article

Renewable-powered agricultural water systems are often assessed as solar-pumping devices, but their sustainability depends on a service chain linking crop-water demand, hydraulic duty point, power electronics, storage, water quality, governance, operation and end-of-life management. This structured integrative review synthesizes peer-reviewed and practice-oriented evidence on photovoltaic pumping, hybrid renewable irrigation, grid-interactive pumps, micro-hydro assistance and renewable-powered brackish-water reverse osmosis (PV-RO). Evidence was screened across four source families and coded by service function, energy architecture, hydraulic duty and dominant sustainability pathway; recurring combinations were consolidated using explicit separation and merge rules. It develops an archetype-based screening framework for ex ante appraisal of irrigation, desalination and circularity risks. Seven technology-service archetypes are identified: direct PV pumping, PV-to-tank pumping, PV with electrical buffering, grid-interactive PV pumping, PV–wind hybrid irrigation, micro-hydro-assisted irrigation and PV-RO water making. The framework links each archetype to its operating envelope, evidence maturity, enabling subsystems, sustainability pathways, minimum indicators and ordinal triggers for deeper due diligence. Hydraulic storage is usually the lowest-regret reliability buffer for open-field irrigation, whereas batteries are justified mainly when pressure stability, fertigation timing or night-time operation has high agronomic value. PV-RO is a distinct water-making archetype and is environmentally defensible only where feed-water characterization, energy recovery, pretreatment, product-water agronomy, membrane management and permitted concentrate disposal are embedded in design. Two synthetic applications demonstrate archetype selection and due-diligence escalation. Responsible deployment requires service-oriented screening that integrates hydraulic design, groundwater governance, procurement quality assurance, circularity obligations and social inclusion before field implementation. Full article

Microgrids are emerging as a promising solution to enhance renewable energy integration, energy reliability, electricity access, and sustainability in Morocco. This paper reviews the development of sustainable microgrids in the Moroccan context by analyzing existing projects, system configurations, control approaches, and energy management strategies. In line with Morocco’s objective of reaching 52% renewable electricity capacity by 2030, the reviewed studies show that hybrid microgrids combining photovoltaic, wind, battery storage, diesel backup, and pumped hydro storage can improve energy autonomy, reduce dependence on fossil fuels, and support a more sustainable energy transition. Across the reviewed case studies, reported performance indicators include renewable energy penetration of up to 97%, a Loss of Power Supply Probability (LPSP) of 0.0489, Levelized Cost of Energy (LCOE) values ranging from 0.038 to 0.17 USD/kWh, and energy cost reductions of up to 20.7% in building-integrated photovoltaic applications. These values are study-specific and should be interpreted as indicative performance outcomes rather than directly comparable benchmarks, since they depend on system size, load profile, storage technology, tariff structure, and optimization assumptions. The review also highlights the role of advanced control and optimization techniques, such as particle swarm optimization, model predictive control, equilibrium optimizer, and adaptive energy management systems, in improving power balance, reliability, cost-effectiveness, and sustainability. Finally, this paper identifies the main technical, economic, regulatory, and institutional barriers limiting large-scale sustainable microgrid deployment in Morocco and proposes recommendations to support decentralized, resilient, and environmentally sustainable renewable energy systems. Full article

This study presents an integrated multidisciplinary framework for evaluating the reuse of abandoned underground mining infrastructure in Bosnia and Herzegovina as sustainable underground energy storage systems that support the energy transition and decarbonization. The research focuses on the Central Bosnia and Tuzla coal basins, using case studies from the Zenica and Tuzla mining regions to assess Underground Pumped Hydroelectric Energy Storage (UPHES), Compressed Air Energy Storage (CAES), and gravity-based energy storage technologies. The methodology integrates geological and geotechnical characterization, thermo-hydro-mechanical (THM) analysis, thermodynamic calculations, and Multi-Criteria Decision Analysis (MCDA) to evaluate technical, operational, and safety performance. Methane mitigation, smart ventilation, thermal stability, and geomechanical behavior under cyclic loading were also considered. The results indicate that sedimentary coal basins are well suited for UPHES and gravity-based storage systems, with UPHES capacities reaching 1.75 GWh per cycle under optimized conditions, while the separately evaluated solid-mass gravity storage system provides a capacity of 6.15 MWh. Evaporite formations in the Tuzla Basin offer favorable conditions for CAES because of the low permeability and plasticity of halite, enabling storage capacities exceeding several GWh. THM analysis confirmed acceptable geomechanical stability during cyclic operation, while the economic assessment based on the Levelized Cost of Storage (LCOS) demonstrated the long-term competitiveness of Abandoned Mine Energy Storage (AMES) compared with battery technologies. Overall, the findings highlight abandoned mines as strategic low-carbon assets for renewable energy integration and regional post-mining transition. 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

Water scarcity and increasing energy demand are critical challenges that often characterize Mediterranean regions, especially islands such as Crete. A sustainable solution for a combined water and energy supply lies in the domain of hybrid renewable energy systems. This research study evaluates a large-scale wind-driven desalination system with pumped-hydro energy storage for the Regional Unit of Rethymno, Crete, focusing on climate-driven demand and air temperature variation. The proposed system integrates wind energy production, seawater desalination, pumped-hydro storage, and water supply both for domestic and for irrigation purposes. Four scenarios, each with increasing air temperature, are examined in order to assess their effect on water demand and system performance. The analysis evaluates electricity allocation, the production of desalinated water, domestic and irrigation coverage, as well as the economic performance of the system. The results indicate that domestic water demand is almost fully covered in all four scenarios, reaching nearly 99.9%, while irrigation water coverage decreases from 82% under present conditions to 67% under higher-temperature scenarios. Wind-generated electricity is mainly used for water-related processes, with a constant share supplied to the grid. The economic assessment indicates that the system can operate under break-even conditions using realistic water and electricity prices. Full article

Pumped hydro storage (PHS) systems, increasingly deployed in power systems with large shares of wind and solar generation, can play a key role in managing power system frequency. Variable-speed pumped hydro storage (VS-PHS) systems, in particular, have potential for rapid primary frequency response by enabling the quick release of machine rotor kinetic energy. However, using conventional proportional–integral (PI) control for converters and governors can result in large speed deviations and torque imbalance during fast system transients. This issue is intensified in PHS plants with slow hydraulic response, such as those with long penstocks or slow guide-vane adjustments, potentially violating mechanical operating constraints. This paper develops a model predictive control (MPC) strategy for coordinated governor and converter control, accounting for operational constraints. The proposed approach improves coordination of hydraulic and electrical systems, utilising DC-link storage and proactive guide-vane action for rapid power adjustments. Dynamic simulations using a complex nonlinear plant demonstrate that MPC redistributes energy extraction between the DC-link storage and the rotating mass while respecting their imposed limits. Furthermore, robustness tests indicate that MPC performance is sustained under plant nonlinearities and measurement noise. These results highlight the advantages of predictive control for supporting frequency response in VS-PHS systems. Full article

The large-scale integration of renewable energy has significantly improved the low-carbon performance of power systems, but has also increased operational uncertainty. Under extreme weather conditions, wind and solar power may experience consecutive days of simultaneous output shortfalls—referred to as “renewable energy drought”—leading to persistently high net load and severe challenges to supply guarantee. To address this issue, this paper proposes a multi-source coordinated supply-guarantee dispatch strategy for consecutive-day renewable energy drought scenarios. First, net load is defined as the total system load minus the available wind and solar output. Based on magnitude and duration thresholds, renewable energy drought events are extracted from historical data to generate representative scarcity scenarios. Second, a multi-source coordinated optimization dispatch model is constructed, incorporating wind power, solar power, thermal units, battery energy storage, and pumped-storage hydro. The objective is to minimize the total system operating cost, which includes thermal fuel cost, start-up/shut-down costs, storage cycling cost, wind/solar curtailment penalty cost, and load shedding penalty cost. The load shedding penalty coefficient is set to a magnitude much higher than conventional costs to highlight the priority of supply guarantee. The model accounts for operational constraints such as minimum up/down times, deep regulation capability, ramping limits of thermal units, and charge/discharge power limits of storage. Taking a provincial power system in China for the year 2030 as a case study, a dispatch case covering four consecutive days (96 time periods) is designed. Based on a baseline scenario, eight groups of sensitivity analyses are conducted to comprehensively investigate the impacts of key factors on the supply-guarantee strategy, including: the minimum up/down time of thermal units, deep regulation capability, load shedding penalty cost, load level, rated energy capacity and charge/discharge efficiency of battery energy storage, rated energy capacity and pumping/generating efficiency of pumped-storage hydro, thermal fuel cost coefficient, and renewable energy capacity. Simulation results show that the proposed strategy can effectively coordinate multiple resources under consecutive-day drought conditions; reducing the minimum up/down time of thermal units improves supply flexibility but increases start-up/shut-down costs; enhancing deep regulation capability optimizes storage utilization and reduces total system cost; the load shedding penalty cost directly determines the trade-off between supply guarantee and economic efficiency; and as load level decreases by 5%, 10%, and 15%, the total system operating cost reduces by approximately 6.3%, 12.5%, and 18.8%, respectively. This study provides a quantitative method and technical support for supply-guarantee dispatch decisions and resource allocation in high-renewable power systems under persistent drought conditions. Full article

Pumped hydro storage remains one of the most established technologies for balancing supply and demand in electricity markets with high shares of renewable energy. This paper investigates the short-term economic optimization of a pumped hydro storage plant operating under real day-ahead market conditions. A Mixed-Integer Linear Programming model is used to optimize hourly dispatch decisions based on actual day-ahead electricity prices in Slovenia for the year 2024. The model accounts for technical constraints, including turbine and pump capacities, round-trip efficiency, energy storage limits, and restricted startup frequencies. The simulation results show that pumped hydro storage can achieve a positive market-based operating result by responding effectively to price volatility and frequent negative pricing events. Seasonal variations reveal higher revenues during summer months due to solar overproduction. The findings confirm the potential of pumped hydro storage to enhance grid flexibility and support the implementation of national energy transition objectives. By linking large-scale energy storage operations with renewable energy integration, grid flexibility, and market-based dispatch, the study also contributes to the technical and economic dimensions of sustainable energy system development. Full article

The integration of high-penetration renewable energy creates new requirements for cross-timescale peak shaving and for system robustness under extreme meteorological conditions. This study develops a dual-timescale capacity allocation method for pumped hydro storage (PHS), combining 8760 h chronological production simulation with monthly typical-day retrospective analysis. The model represents the operating limits of conventional units, nuclear power, hydropower, wind power, photovoltaic generation, tie-line exchange, and PHS energy shifting. On this basis, a stepwise capacity-sensitivity framework is established to minimize annualized comprehensive system cost while controlling renewable energy curtailment within a predefined planning threshold, rather than treating zero curtailment as an unconditional monthly hard constraint. Using long-term planning data from a coastal provincial power grid in southeastern China, the study compares the 2035 and 2040 planning scenarios. The results show that isolated typical-day models tend to overestimate PHS requirements because they disconnect chronological continuity and cross-day reservoir buffering. In 2035, the system presents a two-level seasonal capacity structure: 15,000 MW can support normalized operation in stable months, whereas the rigid boundary rises to 19,000 MW under extreme autumn high-wind conditions. In 2040, wind and photovoltaic capacity increase by approximately 20.01 GW compared with 2035, deepening low-net-load valleys and compressing seasonal regulation margins. Under the assumed planning boundary, the recommended PHS capacity converges to 23,000 MW. The proposed framework provides a practical reference for flexible resource planning in coastal power grids with deep renewable energy integration. Full article

With the large-scale development of renewable energy such as wind, solar and ocean energy, the demand for energy storage is more urgent. Pumped hydro energy storage (PHES) is one of the fundamental solutions to the problem of intermittent supply of renewable energy. The large-capacity/low-head pumped hydro energy storage (LL-PHES) system with the use of tubular pump turbine is a beneficial extension of traditional PHES systems owing to large flow rate and cheaper civil structures. However, the continuous competition between the “static water pressure difference caused by gravity” and the “pressure increase caused by accelerated impeller rotation” leads to prominent instability in the start-up process of the LL-PHES system under pump conditions. An explicit coupling algorithm is proposed for analyzing the transient characteristics in the start-up process of the LL-PHES system under pump conditions. This algorithm is based on the idea of dimensional transformation, and performs 3D flow calculations and 2D rigid body dynamics equation solution in the pump domain and the flap gate domain, respectively. This algorithm avoids the problems of high computational cost and poor convergence that exist in existing fully three-dimensional coupling algorithms and ensures the efficiency of transient hydraulic characteristic calculation. A comprehensive analysis of the transient characteristics of the LL-PHES system during pump start-up process is conducted using the proposed new algorithm. The entire process of the increase in rotational speed, valve opening, flow rate, and the continuous evolution of blade surface pressure during the start-up process is quantitatively described. The amplitude and spectral characteristics of the alternating pressure on multiple blades are clarified. The evolution law of blade load during the stage of severe pressure fluctuations during the start-up process is explained. The load distribution characteristics of “high in the leading and trailing edge areas and low in the middle” in the blade stream direction is presented. The research results have a direct guiding role in improving the hydraulic design and enhancing the operational stability of LL-PHES systems. Full article

The Dynamic Economic Dispatch (DED) problem underpins the cost-efficient and reliable operation of modern power systems, yet valve-point loading, ramp-rate coupling, and the growing share of intermittent wind, photovoltaic, and pumped-storage hydro (PSH) resources render it highly non-convex. Metaheuristic methods typically require large computational budgets and hand-crafted constraint-handling rules, whereas deep reinforcement learning agents rarely guarantee the feasibility of the schedules they produce. To address both limitations, this paper proposes a Two-Stage PPO–RLMPA framework that couples data-driven policy learning with a biomimetic metaheuristic search inspired by marine predator–prey dynamics. In the first stage, a Proximal Policy Optimization (PPO) agent is trained on a Markov Decision Process reformulation of DED in which a deterministic Safety Layer projects every raw action onto the feasible set defined by capacity, ramp-rate, and power-balance constraints, so the policy only observes physically viable transitions. In the second stage, the PPO dispatch is refined by the RLMPA module, a Marine Predators Algorithm (MPA) whose exploration–exploitation balance, Lévy-flight foraging, and Fish Aggregating Devices (FADs) attraction mechanisms emulate strategies documented in marine ecosystems; its step-size factor and FADs probability are further adapted online by a Deep Q-Network. This biomimetics-informed refinement translates predator–prey foraging intelligence into economically efficient thermal dispatch under valve-point non-convexity. Across 30 independent runs on ten- and twenty-unit benchmark systems with wind, PV, and PSH integration, the framework attains best costs of USD 368,763 and USD 737,348 on Test Systems 1 and 2, corresponding to reductions of approximately $1.1\%$ and $4.4\%$ over the CFCEP baseline, with zero post-repair constraint violations in every run. Full article

Reversible pump turbines (RPTs) play a key role in pumped hydro energy storage systems, where increasing grid flexibility requires frequent operation under off-design conditions. In turbine mode, deep partial load and no-load operation are often associated with severe flow instabilities, rotating stall, and strong rotor–stator interactions, which can limit operational flexibility and increase mechanical stress. Previous studies have shown that blade lean can influence hydrodynamic stability; however, its effect under no-load conditions remains insufficiently understood. In this work, the influence of runner blade lean on flow instabilities and rotor–stator interaction in a reversible pump turbine is numerically investigated. Two runner configurations, featuring a 0° and a $-15°$ blade lean angle, are analyzed through unsteady CFD simulations during the transition from deep partial load to no-load operation. The analysis focuses on flow field characteristics, blade loading, and the spectral content of pressure, torque, and radial forces. The results show that the negatively leaned runner significantly mitigates flow recirculation near the hub, reduces pressure and torque fluctuations, and strongly suppresses higher-order harmonic components associated with rotor–stator interaction. In particular, radial force amplitudes at blade-passing harmonics are substantially reduced under no-load conditions. These findings demonstrate that a negative blade lean improves hydrodynamic stability and reduces vibratory loads, contributing to the enhanced operational reliability of reversible pump turbines. Full article