Intermittent Energy Sources Research Articles

Two-Stage Locating and Capacity Optimization Model for the Ultra-High-Voltage DC Receiving End Considering Carbon Emission Trading and Renewable Energy Time-Series Output Reconstruction

With the load center’s continuous expansion and development of the AC power grid’s scale and construction, the recipient grid under the multi-feed DC environment is facing severe challenges of DC commutation failure and bipolar blocking due to the high strength of AC-DC coupling and the low level of system inertia, which brings many complexities and uncertainties to economic scheduling. In addition, the large-scale grid integration of wind power, photovoltaic, and other intermittent energy sources makes the ultra-high-voltage (UHV) DC channel operation state randomized. The deterministic scenario-based timing power simulation is no longer suitable for the current complex and changeable grid operation state. In this paper, we first start with the description and analysis of the uncertainty in renewable energy (RE) sources, such as wind and solar, and reconstruct the time-sequence power model by using the stochastic differential equation model. Then, a carbon emission trading cost (CET) model is constructed based on the CET mechanism, and the two-stage locating and capacity optimization model for the UHV DC receiving end is proposed under the constraint of dispatch safety and stability. Among them, the first stage starts with the objective of maximizing the carrying capacity of the UHV DC receiving end grid; the second stage checks its dynamic safety under the basic and fault modes according to the results of the first stage and corrects the drop point and capacity of the UHV DC line with the objective of achieving safe and stable UHV DC operation at the lowest economic investment. In addition, the two-stage model innovatively proposes UHV DC relative inertia constraints, peak adjustment margin constraints, transient voltage support constraints under commutation failure conditions, and frequency support constraints under a DC blocking state. In addition, to address the problem that the probabilistic constraints of the scheduling model are difficult to solve, the discrete step-size transformation and convolution sequence operation methods are proposed to transform the chance-constrained planning into mixed-integer linear planning for solving. Finally, the proposed model is validated with a UHV DC channel in 2023, and the results confirm the feasibility and effectiveness of the model.

Balancing operational efficiency and regulation performance, for guiding pumped-storage day-ahead scheduling

Pumped-storage plants (PSPs) have significant potential to regulate intermittent energy sources. However, achieving coordinated optimization of regulation stability and operational efficiency has been a long-standing challenge. This study proposes a new soft linking model to address the limitation that current scheduling methods fail to account for both efficiency and second-level stability simultaneously, aiming to improve the day-ahead scheduling strategies for PSP. Firstly, a Pumped-Storage Hydroelectric System (PSHS) model is developed to reflect the regulation stability of PSP, considering the transient characteristics of hydraulic, mechanical, and electrical subsystems. Then, by analyzing transient responses under various operating working conditions, the study integrates the transient variation laws of the power plant into a regulation stability dataset (RSD). Finally, using RSD as the coupling interface, with regulation stability and operational efficiency as the objective functions, a Pumped-Storage Power Day-ahead Scheduling (PSPDS) model is established. An actual PSP is used as a case study to evaluate the effects of four operational scenes with varying optimization objectives on operational efficiency and subsystem performance. The results indicate that controlling load change magnitude and increasing the load decrease working conditions effectively enhance the stability of PSP subsystems. In addition, although the proposed scheduling scheme increases water consumption by 0.0213% compared to traditional scheduling method, it improves regulation stability by at least 15.14%. The findings suggest that a minor compromise in operational efficiency can lead to a significant improvement in regulation stability. This study provides new perspectives and methods for the management and optimization of PSPs.

Moisture dynamics during high‐load fluctuations in transformers: Localised accumulation and interfacial transfer within oil/pressboard insulation

AbstractPower systems grapple with the challenges of high load rates and intermittent new energy sources integration. Transformers, as vital equipment, employ oil/pressboard (oil/PB) insulation. Uneven moisture distribution in this insulation can jeopardise safety thresholds, necessitating precise moisture assessment for grid stability. A novel mathematical model, adsorption–desorption and porous media moisture transfer (ADP‐MoT), is presented. This model incorporates adsorption and desorption processes within the porous pressboard, enabling a description of the dynamic moisture transfer between the oil and pressboard. Using this mathematical model, simulations for moisture dynamics were performed on a 750‐kV transformer across four typical days. The results indicate that temperature fluctuations are the primary driving factor for moisture migration at the oil/PB interface. Convection and diffusion contribute to moisture movement towards cooler regions. Fluid properties and structural characteristics induce a distinctive streamline‐shaped moisture flow within horizontal oil channels, with localised moisture accumulation in specific areas. Moreover, the analysis of 96 transient results uncovers potential free‐state moisture formation during severe conditions, underscoring the importance of monitoring the pressboard at winding bases during high load fluctuations. In conclusion, this study significantly contributes to scientifically identifying and addressing risks tied to new energy sources integration in power systems.

Electrical Conductivity of Binary, Ternary, Quaternary and Quinary Molten Salt Mixtures Based on NaCl-CaCl2

As intermittent energy sources like solar energy and wind power emerge, the need for energy storage becomes important, energy availability needs to be ensured also when the Sun is not shining, and the wind is not blowing. Energy storage can also be used for peak shaving purposes during periods of high demand. Energy storage solutions need to be inexpensive and reliable. Novel all-liquid batteries are considered one option for stationary energy storage and the Na-Zn battery is currently being investigated. During charging Na metal is formed on the negative electrode from a NaCl containing electrolyte and ZnCl2 is formed from a Zn pool on the positive electrode. The electrical conductivity of the molten salt is an important factor in the ohmic loss through the electrolyte. The composition of the electrolyte decides the electrical conductivity, and this conductivity also changes during the charge/discharge cycles of the battery as the electrolyte composition changes accordingly. Electrical conductivity has been measured on different compositions of NaCl-CaCl2, NaCl-CaCl2-LiCl, NaCl-CaCl2-BaCl2, NaCl-CaCl2-ZnCl2, NaCl-CaCl2-BaCl2-SrCl2, NaCl-CaCl2-BaCl2-ZnCl2 and NaCl-CaCl2-BaCl2-SrCl2-ZnCl2 molten salts in an in-house built apparatus. The smaller ions (Li and Na) give higher electrical conductivity, while the larger ions (Ba, Sr, and Zn) reduce the electrical conductivity.

Energy Performance of Zeolite-Based Drying Bead Desiccants Used to Dry Paddy Rice.

This study utilizes differential scanning calorimetry and thermogravimetric analysis to assess the total energy required to regenerate saturated zeolite-based drying beads (DBs) used to dry paddy rice. We quantify the required heat energy for DB regeneration by calculating the area under the curve in a heat flow rate versus time graph, with the end of the regeneration process indicated by stabilization of the DB weight. Our findings suggest that at DB regeneration temperatures ranging from 120 to 350 °C, the process varied from 813 to 22 min, demonstrating that higher temperatures lead to faster regeneration speeds. The total energy used for regeneration showed similar values at 250 and 350 °C, averaging around 2032 and 2136 kJ per kg of dried DB, respectively. Additionally, the study showed that DBs can hold water between 28.7% and 54.4% higher than the manufacturer's specifications, suggesting a reduced quantity of DBs required for effective paddy rice drying. The overall required heat energy for the regeneration process was calculated at 4.86 MJ/kg, with a carbon intensity of approximately 275.61 g of CO2-eq per kg of water removed, resulting in lower values compared to conventional drying methods. The study underscores DB's possibility of lower total energy (thermal and electrical) consumption and greenhouse gas emissions, alongside its flexibility to regenerate with intermittent energy sources.

Design and assessment of a concentrating solar thermal system for industrial process heat with a copper slag packed-bed thermal energy storage

Decarbonising the industrial sector is a key part of climate change mitigation targets, and Solar Heat for Industrial Process (SHIP) is a promising technology to achieve this. However, one of the drawbacks of SHIP systems is that they rely on an intermittent energy source. Therefore, sensible energy storage has emerged as a potential solution. In addition, solid byproducts have been proposed as a low-cost but effective material for thermal energy storage (TES). This work presents a SHIP system model coupled with a copper slag-packed-bed TES (PBTES) model using air as heat transfer fluid. The TES has been implemented to preheat the makeup water of the tank where steam is generated. A system design was carried out using a parametric analysis to find a solar field size and a corresponding TES volume. The resulting system was simulated, and the operating variables were analysed in detail. The results show that it is possible to generate 20% more energy due to the storage system. Additionally, a techno-economic analysis indicates that the SHIP with PBTES system results in a payback period of 14 years and a savings of CO2 emissions of 30tCO2.

Predicting power and solar energy using neural networks and PCA with meteorological parameters from Diass and Taïba Ndiaye

The excessive reliance on conventional fossil fuel-based resources poses a significant threat to our environment. To mitigate this impact, it has become increasingly crucial to increase the integration of intermittent and non-polluting energy sources into our electrical grids. However, while this higher penetration rate brings benefits such as improved producer satisfaction and reduced fossil fuel consumption, it also presents challenges for traditional non-smart electrical networks. To promote intermittent energy sources effectively and maintain a balance between consumption and production, accurate forecasting of these energy outputs plays a vital role. This research paper focuses on studying the application of artificial neural networks for predicting the power and energy output of the Diass solar power plant in the short and medium term. The proposed approach utilizes not only the meteorological data from the city where the power plant is located but also data from a nearby city with a data acquisition station. Principal component analysis (PCA) is employed to select the relevant variables for the prediction model. Furthermore, the results obtained from our approach are compared to existing literature that solely uses meteorological data from the power plant's location. The comparison shows that our method achieves more satisfactory results, with mean absolute errors and root mean square errors of 0.0223 KWh and 0.003 KWh, respectively, and a prediction accuracy of 94.57% in terms of energy and power. It is worth noting that the computational resource requirements for our approach are higher, with simulation times ranging between 1788 seconds and 2201 seconds. By utilizing a broader range of data sources and employing advanced techniques like artificial neural networks, this research contributes to improving the accuracy of solar power generation forecasts. The findings highlight the potential of incorporating additional data inputs and advanced modeling techniques to enhance the performance of renewable energy systems, paving the way for a more sustainable and efficient energy future.

Uncovering Reduction Mechanisms of Fluoroethylene Carbonate

Energy storage plays an integral role in climate change mitigation, given that many promising alternatives to fossil fuel-based technologies rely on intermittent energy sources like the sun or wind. Particularly, lithium metal batteries (LMBs) are a promising technology due to lithium’s high theoretical specific capacity and low reduction potential, which can result in batteries with energy densities surpassing current state of the art lithium-ion batteries.1 Electrolyte design is a key strategy to improve the cycling stability and Coulombic efficiency of LMBs, where the highly reductive lithium metal anode reacts with the electrolyte during cycling, resulting in capacity loss. These reactions form a solid electrolyte interphase (SEI), and many successful electrolyte engineering strategies have involved tuning the SEI to be mechanically and chemically stable to prevent further reactions.In this research, we focus on fluoroethylene carbonate (FEC), a highly effective electrolyte solvent in LMBs.2 Although prior research has illuminated key reduction products of FEC2,3, including lithium fluoride (LiF), there remains a gap in understanding regarding the mechanism by which FEC and other similar fluorinated solvents are reduced to form an SEI. Furthermore, recent research has demonstrated that a preformed SEI comprised solely of LiF breaks down during cycling, illustrating that bulk chemical and mechanical properties of SEI components may not translate to their function within the SEI.4 In this work, we employ electron paramagnetic resonance (EPR) spectroscopy to study intermediate generation during FEC reduction. We pursued both a chemical reduction using lithium naphthalenide and an electrochemical approach to reduce FEC. The use of EPR with spin traps enables insight into the radical species formed during FEC reduction, which we hypothesize are precursors to cross-linked polymer networks that are key to a high performing SEI. Here, we employed conventional post-mortem SEI analysis like X-ray Photoelectron Spectroscopy (XPS) in addition to EPR to clarify reduction mechanisms of FEC and form a framework for studying electrolyte reduction intermediates. Ultimately, this approach affords insight into electrolyte breakdown mechanisms to form an effective SEI which can both accommodate volume expansion and inhibit parasitic electrolyte consumption. This will guide electrolyte design for high Coulombic efficiency LMBs in the future.References K. G. Gallagher et al., Energy Environ. Sci., 7, 1555–1563 (2014).X.-Q. Zhang, X.-B. Cheng, X. Chen, C. Yan, and Q. Zhang, Advanced Functional Materials, 27, 1605989 (2017).Y. Jin et al., J. Am. Chem. Soc., 139, 14992–15004 (2017).M. He, R. Guo, G. M. Hobold, H. Gao, and B. M. Gallant, Proceedings of the National Academy of Sciences, 117, 73–79 (2020).

(Invited) Comparison of Catalyst-Coated Electrodes vs. Catalyst-Coated Membranes in PEM Water Electrolysis Cells

The PEM (Proton-Exchange Membrane or Polymer Electrolyte Membrane) cell concept [1] is used in fuel cells and water electrolysis cells. PEM water electrolysis is a compact, efficient and flexible technology for the production of “green-hydrogen” from renewable (intermittent) energy sources. The unit cell (Figure 1) is made of several adjacent functional layers: (i) the proton-conducting polymer membrane (1); (ii) two catalysts layers (CLs) for hydrogen/oxygen evolution containing platinum group metals or PGMs (2;2’); (iii) a porous transport layer used for mass transport of reactants/products and electricity distribution (3;3’); (iv) water flow fields for water circulation (4;4’); bipolar plates (5;5’). From a practical viewpoint, the CLs can be deposited on either side of the interfaces formed between the polymer membrane and the porous transport layer: (i) on the supporting porous transport layers to form catalyst-coated electrodes which are then hot pressed against the bare membrane to form membrane – electrode assemblies; (ii) directly onto the membrane to form catalyst-coated membranes (CCM).The aim of this paper is to evaluate the efficiency and durability of both concepts, drawing on recent advances in manufacturing techniques to reduce the loading of PGM catalysts.[1] W.T. Grubb Jr., Batteries with Solid Ion-Exchange Electrolytes. Journal of the Electrochemical Society. 106 (1959) 275-279.[2] C. Rozain, P. Millet, Electrochemical characterization of Polymer Electrolyte Membrane Water Electrolysis Cells, Electrochimica Acta, 131 (2014) 160-167. Figure 1. Schematic diagram showing the cross-section of a PEM water electrolysis cell [2]. Figure 1

Gran Canaria energy system: Integration of the chira-soria pumped hydroelectric power plant and analysis of weekly daily demand patterns for the year 2023

Due to its insular condition, Gran Canaria operates an isolated energy system that requires high self-sufficiency in energy generation and that covers its energy need, 3,327,872.76 MWh/year. The future integration of the Chira-Soria Pumped Hydroelectric Power Plant, scheduled for 2030, is expected to radically transform the energy dynamics of Gran Canaria's electricity system, facing different challenges and opportunities. Challenges include the need for greater flexibility due to growing renewable energy sources, going from 381,000 MW of renewables today to an increase of more than 750,000 MW, environmental commitments, and the operation must address potential operational constraints related to downstream hydrological effects. On the other hand, the opportunities lie in the ability of the reversible hydropower plant to provide balancing services during off-peak hours, improving the integration of intermittent energy sources such as wind and solar power, in addition, the Pumped Hydroelectric (PHES) technology is recognized as mature and efficient for large-scale energy storage, contributing significantly to the integration of renewable energy sources. Implementing innovative approaches such as integrating Big Data into construction projects can also improve efficiency and decision-making in the project delivery process. This facility will facilitate energy storage through the pumping of water at high levels, allowing it to be subsequently turbined in periods of high demand, which will be essential to improve the management and efficiency of the island's energy system. This energy demand will be studied, which follows certain patterns according to the day of the week and, continuing with the line of research established in previous works, a detailed analysis of the existing system, simulation and algorithmic optimization of the integration of the Chira-Soria Pumped Hydroelectric Power Plant into the energy system of Gran Canaria in the year 2023 will be carried out, providing the expected results of such optimal integration by differentiating the demand patterns of each day of the week, previously establishing these annual representative days.

Extending the operational range of Francis turbines: A case study of a 200 MW prototype

Francis turbines are now widely used to support the integration of renewable and intermittent energy sources such as solar and wind power. Consequently, these turbines often operate away from their best efficiency point (BEP). Such operations cause detrimental pressure fluctuations in the runner and draft tube, leading to early fatigue failures. To address these harmful flow conditions and extend the operating range of Francis turbines, a mitigation system was developed and tested on a large-scale, high-head 200 MW Francis turbine. The system consists of four circular rods placed in the draft tube with variable radial protrusion lengths, adjustable using linear actuators. Pressure, accelerometer, and vibration sensors installed on the turbine allowed quantification of the rod system performance. The results demonstrate the system’s capability to reduce pressure pulsations by up to 80 % in terms of maximum pressure amplitude and 100 % in terms of fatigue cycle in both low and high-frequency ranges, up to ten times the runner frequency, based on pressure analysis. The optimal rod protrusion ranges from 5 to 20 % of the runner outlet diameter function of the operating load. The impact of the rods’ protrusion on the turbine structure appears negligible from the accelerometer measurements performed on the draft tube and spiral casing. The hydraulic efficiency is reduced by up to 1 %. These findings are significant across a wide range of part-load operations, from 40 % to 60 % load, indicating the potential to extend the operational range of existing Francis turbines. The research presented here is a novel attempt to enhance the existing Francis turbines with a new degree of freedom using protruding rods.

Amorphous multimetal based catalyst for oxygen evolution reaction

The development of efficient, low-cost water splitting electrocatalysts is needed to store energy by generating sustainable hydrogen from low power clean but intermittent energy sources such as solar and wind. Here, we report a highly sustained low overpotential for oxygen evolution reached by the unique combination of three metals (NiCoV) prepared from a simple low temperature auto-combustion process. The amorphous multimetal oxygen evolving catalyst could be stably coated on a stainless-steel support using a tribochemical particle blasting method to create an oxygen evolution reaction (OER) electrode with a low overpotential of 230 mV at 10 mA cm−2 and a low Tafel slope of 40 mV dec−1. In addition to their low overpotential, this oxygen evolving electrocatalyst preserved performance demonstrating a stability after 10 h at the technologically relevant current density and without any surface morphology alteration. Given the importance of sustainable hydrogen production, the development of this new OER catalyst points the way to removing a key technical bottleneck for the water splitting reaction and could offer a route to cost reduction and lowering hurdles to more widespread adaptation of electrolyser technologies for hydrogen production.

A robust and highly active bimetallic phosphide/oxide heterostructure electrocatalyst for efficient industrial-scale hydrogen production

Efficient and durable high-current-density bifunctional electrocatalysts are vital for cost-effective production of alkaline water electrolyzers (AWEs) on an industrial scale. However, existing commercial catalysts, such as Raney Ni which requires over 2.5 V for just 500 mA cm−2, fail to achieve high current densities with low cell voltages. In this study, we introduce a bifunctional RuP2/Ni5P4/NiMoO4 heterostructure electrocatalyst, synthesized via a facile hydrothermal method, followed by the controlled addition of ruthenium (Ru) and subsequent phosphorization. This process yielded (Ru, Ni) phosphides and NiMoO4 with a moderate weight percentage and mass loading of Ru content, approximately 1.02 wt% and 61 μg cm−2, respectively. The synergistic effect of these phosphides and bimetallic oxides significantly improves water dissociation, as well as the hydrogen and oxygen evolution reaction (HER and OER) performances. Under industrial conditions (80 °C and 6 M KOH), our catalyst achieves low overpotentials of 273 mV for HER and 390 mV for OER at 2000 mA cm−2, outperforming commercial Pt/C and RuO2 catalysts. Additionally, in an AWE, our catalyst maintains a low operating voltage of 1.76 V for 1 A cm−2, with consistent performance over 100 h at 500 mA cm−2. It records an electricity consumption of 3.97 kW h Nm−³ and an electrolyzer efficiency of 89.1%, underscoring its potential for cost-effective industrial applications. Furthermore, accelerated degradation tests under variable current loads show no significant change in cell voltage and high-frequency resistance (HFR), demonstrating robustness for intermittent energy sources. This work proposes a novel design principle for high-performance electrocatalysts, significantly reducing reliance on noble metals and offering a robust, efficient solution for industrial-scale hydrogen production.

Promoting Water Oxidation by Proton Acceptable Groups Surrounding Catalyst on Electrode Surface.

Large-scale hydrogen production through water splitting represents an optimal approach for storing sustainable but intermittent energy sources. However, water oxidation, a complex and sluggish reaction, poses a significant bottleneck for water splitting efficiency. The impact of outer chemical environments on the reaction kinetics of water oxidation catalytic centers remains unexplored. Herein, chemical environment impacts were integrated by featuring methylpyridinium cation group (Py+) around the classic Ru(bpy)(tpy) (bpy = 2,2'-bipyridine, tpy = 2,2':6',2''-terpyridine) water oxidation catalyst on the electrode surface via electrochemical co-polymerization. The presence of Py+ groups could significantly enhance the turnover frequencies of Ru(bpy)(tpy), surpassing the performance of typical proton acceptors such as pyridine and benzoic acid anchored around the catalyst. Mechanistic investigations reveal that the flexible internal proton acceptor anions induced by Py+ around Ru(bpy)(tpy) are more effective than conventionally anchored proton acceptors, which promoted the rate-determining proton transfer process and enhanced the rate of water nucleophilic attack during O-O bond formation. This study may provide a novel perspective on achieving efficient water oxidation systems by integrating cations into the outer chemical environments of catalytic centers.

Techno-economic assessment of renewable hydrogen production for mobility: A case study

Renewable hydrogen produced by water electrolysis from intermittent energy sources (i.e. sun and wind) is considered one of the most promising energy carriers for the decarbonisation of the so-called “hard-to-abate” sectors, especially heavy-duty transport and industry. To this reason, several new projects are currently under development and public fundings are widely available to boost the renewable hydrogen market. In this fast-changing scenario, this paper presents the techno-economic analysis of an integrated system where renewable power generation, electrolytic hydrogen production and final hydrogen use are closely integrated within a specific site, allowing higher efficiency as well as a containment of hydrogen production and handling cost. The analysis here presented considers a specific case study that includes a 12.5 MWP photovoltaic plant, a 5 MW electrolyser capable to produce nearly 300 t/yr. of renewable hydrogen, and a compression and storage system, all located in Sardinia (Italy). Differently from previous studies, this work faces the analysis from two opposite perspectives: on the one hand, it allows the assessment of the levelized cost of hydrogen during the whole project’s life, making the results comparable to those from other similar analyses; on the other hand, it presents the calculation of project’s profitability in terms of net present value, internal rate of return and payback time from the perspective of a potential investor. The analysis shows that a whole investment of about 20.3 M€ is required, which allows to achieve a levelised cost of hydrogen of 4.09 €/kg, which can decrease to 2.97 €/kg considering the revenues from selling oxygen and the overproduction of electricity. The potential use of renewable hydrogen in urban public transport (by means of fuel cell electric vehicles) has been considered as well, in comparison with conventional diesel buses. Despite the lower cost for fuel (0.41 €/km for hydrogen buses vs. 0.72 €/km for diesel buses) and maintenance and repair (0.20 €/km vs. 0.27 €/km), as well as the lower CO2 emission (some 76 t/yr. saved per bus), the very high investment cost for hydrogen-fuelled buses (up to 720,000 €) makes hydrogen still not competitive with diesel for urban transport, being hydrogen buses characterised by a whole specific transport cost of 1.45 €/km, to be compared with 1.04 €/km for diesel buses.

Assessment of the potential of salt mines for renewable energy peaking in China

Renewable energy sources, such as wind and solar, can reduce environmental pollution and promote the transformation of the energy structure. However, the intermittency and uncertainty of new energy sources such as wind and photovoltaics pose challenges to large-scale grid integration. Effective utilization of intermittent energy sources requires large-scale energy storage facilities. Salt rock is recognized as an excellent medium for underground large-scale energy storage with a wide range of applications. This paper identifies the potential of salt caverns to be used for large-scale energy storage by analyzing the distribution of wind and solar energy resources in China, taking into account the grid-connected infrastructure of the Chinese power grid and the geographic location of salt mines. The overlapping areas are identified for utilization in compressed air energy storage and hydrogen storage. Through meticulous categorization and analysis of the factors influencing salt cavern underground storage site selection, the AHP-EWM method is introduced to establish an objective hierarchy model for a comprehensive evaluation system of salt cavern underground storage site selection. The comprehensive planning of China's 20 major salt mines is conducted, and the research findings hold significant reference value for facilitating the low-carbon energy transition in China.

Ancillary services from wind and solar energy in modern power grids: A comprehensive review and simulation study

Renewable energy sources like wind and solar have increased demand for surplus power capacity. The demand is primarily fueled by the growing impact of forecasting errors associated with these intermittent energy sources. Implementing advanced control methods for automatic generation control (AGC) is essential to integrate wind and solar power with conventional generation sources to balance the power system and reduce reliance on traditional reserves. Therefore, this paper comprehensively overviews solar and wind energy integration in the AGC framework to provide optimal grid ancillary services. Initially, the paper presents an overview of the basic equations used to integrate reserve power from the photovoltaic (PV) system by employing the de-loading strategy. Subsequently, a comprehensive review is conducted on integrating the PV system in AGC strategies to provide grid ancillary services. The study also analyzes the contribution of wind power in AGC services using relevant equations and past practices. The paper presents a real-time dynamic control strategy to optimize the dispatch of the AGC unit by integrating the operating reserves from wind energy systems in conjunction with thermal power systems. The study simulates an 8-bus, 5-machine model using the Dig-SILENT Power Factory. The findings reveal that utilizing operating reserves from wind power can significantly reduce large-scale forecasting errors in massively renewable energy resources (RES) integrated power systems, thereby ensuring the necessary system operational security and reducing the reliance on traditional generating units.

Magnetic field based finite element method for magneto-static problems with discontinuous electric potential distributions

We introduce two finite element formulations to approximate magneto-static problems with discontinuous electric potential based respectively on the electrical scalar potential and the magnetic field. This work is motivated by our interest in Liquid Metal Batteries (LMBs), a promising technology for storing intermittent renewable sources of energy in large scale energy storage devices. LMBs consist of three liquid layers stably stratified and immiscible, with a light liquid metal on top (negative electrode), a molten salt in the middle (electrolyte) and a heavier liquid metal on bottom (positive electrode). Energy is stored in electrical potential differences that can be modeled as jumps at each electrode-electrolyte interface. This paper focuses on introducing new finite element methods for computing current and potential distributions, which account for internal voltage jumps in liquid metal batteries. Two different formulations that use as primary unknowns the electrical potential and magnetic field, respectively, are presented. We validate them using various manufactured test cases, and discuss their applications for simulating the current distribution during the discharge phase in a liquid metal battery.

Smarter, greener extractivism: digital infrastructures and the harnessing of new resources

ABSTRACT The past several years have seen increased scholarly attention to the concept of ‘extraction’ and ‘extractivism’ as critical frameworks in the humanities and social sciences. These are not only concepts and processes through which to understand material extraction but also expanded formations of extraction as requiring an assemblage of interlocking activities united under an umbrella of exploitative, material economic practices. This article demonstrates that digital data infrastructures, especially data centres, are acting as tools in which to manage the compounding contradictions of paired ‘green,’ digital growth in constrained electricity systems like Ireland. Building on theories of ‘green extractivism’ in the digital sphere and drawing upon fieldwork and policy analysis in data centre industry settings, this article argues that in the form of interconnected climate and digital infrastructures, tech capital is shoring up its role in green transformations, including in the grid systems that will need to adapt away from fossil fuel supply to intermittent energy sources and increasing demand from data centres. In this way, data centres are becoming technologies of green extractivism for overlapping projects of digital grid transformations and climate-friendly capitalism.

Enhancing frequency regulation in multi‐area interconnected MPS with virtual inertia using MPC + PIDN controller

AbstractThe challenge of controlling frequency deviation becomes more difficult as the complexity of a power network increases. The robustness of the controller has a major impact on the stability of a Modern Power system (MPS). Due to the hybridization of MPS basic AGC controllers (PID, FOPID, and TID) are insufficient to give optimal performance of a plant. This requires a robust controller. So, a novel MPC + PIDN controller has been proposed and evaluated by comparing it with several existing controllers, which gives optimal performance in terms of overshoot, undershoot, and settling time. A new modified Opposition‐based Sea‐horse Optimization (OSHO) method has been suggested to optimize the various controller settings. To demonstrate the OSHO's superiority, it is compared with a few popular, existing meta‐heuristic optimizations. The higher penetration levels of RESs reduced system inertia which further deteriorate frequency response in MPS. To overcome these challenges virtual inertia (VI) is implemented with MPC. VI is applied to improve the performance of the AGC of the interconnected MPS along with emphasizing the nature of intermittent renewable energy sources (RESs) of PV and wind energy. To determine the reliability and flexibility of the proposed controller, analysis has been done under a different situation, including step, random disturbances, and modified IEEE‐39 bus. Finally, the stability analysis is performed on a bode plot and the proposed results are compared with previously published literature. The extensive study demonstrates strong evidence that the suggested control approach is efficient and effective.