Local Grid Research Articles

Patient-Specific Three-Dimensional-Printed and Bolus Material-Based Localization Grids for Magnetic Resonance Imaging-Guided Interventional Procedures

Abstract In view of the lack of commercially available localization grids for magnetic resonance imaging (MRI)-guided interventional procedures, two customizable and easily fabricable grids are proposed. The first one is a patient-specific three-dimensional-printed localization grid that incorporates MRI markers while the second one is a grid constructed with Superflex Transparent Bolus material. MRI scans were performed with the grids attached on an abdominal phantom. The patient-specific three-dimensional-printed grid is visible in T1-weighted, T2-weighted, proton density (PD) and fluid attenuated inversion recovery MR images, whereas the Superflex grid is visible only in T1-weighted and PD images. However, the Superflex grid offers the advantage of a simpler fabrication process and is more cost-effective. Both proposed localization grids can facilitate the determination of the optimal needle entry positions for MRI-guided interventional procedures, leading to reduced overall procedure time and improved efficiency.

Критерии теплосетевых организаций: проблемы правоспособности

Amendments to the heat supply laws came into force over a year ago, providing criteria for acquiring the status of a heat network company. The purpose of these innovations was to bring order to the heat market and maintain competent professional players. It aimed at consolidating network assets in the last resort heat supplier, the unified heat distribution company, and depriving enterprises that lack the necessary material, labor, and technical resources for proper maintenance and repair of heat networks of the status of a heat network company. The intermediate results of the reform suggest now that the legislator’s expectations were not fully met. While disclosing the historical peculiarities of heat industry development in the pre-reform period, this article examines the factors that first led to the emergence of multiple heat network companies in the heat supply market and then prompted the legislator to take measures to optimize the number of regulated organizations. To simulate the potential effects of legal regulation, the author examines the electric power industry, which is related to heat supply. The legislator had already established criteria for local grid organizations in this industry several years before the reform of heat network companies. However, the legal position of the Constitutional Court of the Russian Federation prevented the legislator’s efforts from being fully implemented. To address the problem at hand, the author suggests transitioning from quantitative to qualitative criteria for evaluating an entity’s compliance with the status of a heat network company. This approach will prioritize the reliability of heat supply over using compliance as a formal basis for depriving bona fide enterprises of the status of a professional player in the heat market.

Experimental analysis of a photovoltaic self-consumption system for the offices of a local company

The article analyzes the prospect of a solution for the mutual interaction of a photovoltaic generator and the local electrical grid, within the context of electrifying the offices of a hydrocarbon storage facility. The idea is to examine the operational performance of a system that enables the maximum self-consumption of energy generated by a small-scale photovoltaic system installed on the facility's site. Such a system could prove beneficial for multiple consumers operating in a complex energy environment. The issue is scrutinized based on experimental data from a real case in Dakar, Senegal. An installation with a photovoltaic system of approximately 17 kWp peak power is monitored for a year to assess the reliability of the self-consumption photovoltaic system for a broader application. The data encompasses both the functioning of the photovoltaic system and its interaction with the electrical grid. The potential use of this solution in the context of promoting self-consumption policies to reduce electricity consumption expenses is discussed and analyzed, revealing a relatively high level of interaction with the electrical grid. Despite maintenance costs, the photovoltaic system proves to be cost-effective.

Low voltage grid resilience: Evaluating electric vehicle charging strategies in the context of the grid development plan Germany

The ongoing transition to decentralized renewable energy sources and sector-coupled consumers is reshaping the energy system. Changes at lower grid levels can stress lines and transformers. Crucial for a successful local energy transition are grid relief measures. Battery electric vehicles contribute to higher loads on grid equipment but also offer flexibility. This paper assesses the influence of four different charging strategies for battery electric vehicles across five representative low-voltage grids based on the grid development plan in Germany for the years 2021, 2037, and 2045. Results indicate that grid stress, specifically capacity stress, will emerge by 2037 and 2045. Decentralized photovoltaic systems are the primary contributors to this stress due to high simultaneous generation. Up to nearly 20% of photovoltaic power may need to be curtailed in 2045, especially in rural grids during the summer, to prevent overloads.Charging strategies linked to wholesale power market prices can inadvertently lead to higher consumption-induced grid overloads, necessitating the consideration of local grid restrictions. Implementing grid-friendly charging strategies, such as reduced charging power or alignment with local photovoltaic production, can mitigate those grid overloads from almost 8% down to 0.11%. However, these charging strategies have limited impact on photovoltaic-induced overloads due to the low number of connected battery electric vehicles during the day.In summary, appropriate charging strategies can ease low-voltage grid stress and are suitable measures to manage the challenges of decentralized energy transition and battery-electric vehicle adoption.

A three-dimensional evaluation method for building energy systems to guide power grid-friendly interactions during the planning and operational stages

Under the premise of on-site demand satisfaction and improving the efficiency of energy utilization, grid-friendly buildings can achieve stable power consumption without increasing dispatch pressure on local power grids. They can even actively respond to the grid's demand. The existing methods for evaluating grid-friendly building energy systems are based on a single perspective and scenario. There is no multidimensional evaluation system that takes into account the requirements that exist in the planning and operational stages of buildings. Thus, building designers do not know the short- and long-term response effect or grid-friendly potential of alternative schemes. To address this issue, three evaluation dimensions of grid-friendly building energy systems have been determined based on the requirements that exist in the planning and operational stages, and a comprehensive evaluation system has been developed. First, the three evaluation dimensions were defined by analyzing the evaluation needs. Second, indexes for the three dimensions were developed. Third, the optimal grid-friendly building energy system origin was calibrated with the index extremum analysis. The integrated score calculation approach was developed with the spatial Euclidean distance. Finally, the correctness and rationality of the proposed method have been verified via comparison with the traditional method and dimensional reciprocity. The results show that energy storage can significantly increase the grid-friendly capacity of a building's energy system and enhance the long-term and short-term response effects. It is anticipated that building designers will be better equipped to select alternative schemes if they use the proposed method and that using this method will support the optimization of building-side scheduling and grid-side management strategy formulation.

General structures of control area cooperation for variable renewable energy integration in electric power systems

To integrate large-scale variable renewable energy resources (RESs) in modern power grids, the coordinating control area (CA) operation is the most cost-effective method. This article reviews the technical aspects of CA cooperation. Firstly, a brief overview of the active balancing control within each CA is discussed. Secondly, three general control structures for CA cooperation are innovatively proposed, the corresponding implementation details are analyzed, and some representative technologies are also provided in the systematic analysis. Then, some future research directions such as large-scale power sharing by DC, active power control of RES bases, and the new structure for distributed energy resources in local power grids are prospected. Finally, the changes in power systems brought about by their evolution and importance for further promoting cooperation between CAs are summarized.

Economic feasibility of integrating solar energy into water utility operations in Ciudad Juárez, Mexico

We perform an economic feasibility analysis for installing grid-connected solar arrays with batteries to power ten water supply, distribution, and treatment stations in Ciudad Juárez in tandem with the existing local grid. This article covers detailed results from the four stations that represent the topographical and geographical variability of the city and the variable electricity demand across sites. Using data from the city’s water utility and calculations from the HOMER and RETScreen models, we find contrasting results. The HOMER model finds that solar arrays with or without batteries are economically viable while RETScreen reaches the opposite conclusion. One key reason for this is the two models’ differing predictions on the amount of electricity the proposed solar arrays would supply. Further, having reliable battery storage is paramount to overcoming grid outages and the intermittent availability of solar power to ensure the success of solar projects. Global scientific consensus recognizes the need for more renewable energy. With a sunny-climate and its status as a manufacturing hub on the US-Mexico border, Ciudad Juárez has the potential to lead the way forward in promoting solar energy. The comparative results of the HOMER and RETScreen models provide a more complete understanding of the feasibility of solar power for Ciudad Juárez’s water infrastructure as well as vital insight into the factors that shape the success of solar projects.

Modeling fluid flow in fractured porous media: a comparative analysis between Darcy–Darcy model and Stokes–Brinkman model

AbstractThere are limited comparative studies on modeling fluid transport in fractured porous media. Hence, this paper systematically compares the steady-state creeping flow Stokes–Brinkman and Darcy–Darcy models for computational efficiency and accuracy. Sensitivity analyses were also conducted on the effect of fracture orientations, fracture sizes, mesh resolution, and fractures with Local Grid Refinement (LGR) under the FEniCS computational framework. Both models were validated numerically, and the accuracy of their solution is compared using the R-squared metric and L2 norm estimates. Key results showed that both models have similar pressure and velocity field solutions for a given fracture orientation. The computational time required for solving the Stokes–Brinkman models for a single fracture case was unusually lower than that of the Darcy–Darcy model when the pressure and velocity terms in the Darcy–Darcy model were solved simultaneously using two equations, contrary to where only one equation solves for the pressure and the velocity is obtained by projecting the gradient of pressure onto a vector space. The Stokes–Brinkman model is more sensitive to mesh resolution, and as a result, the Darcy–Darcy model tends to be more accurate than the Stokes–Brinkman model at low resolutions. Local Grid Refinement (LGR) can improve the Stokes–Brinkman model's accuracy at low mesh resolution. Furthermore, both models showed similar results when compared for complex fracture systems such as multiple fracture cases: interconnecting and isolated fractured porous media systems under low-velocity and steady-state creeping flow conditions. The FEniCS code in this paper is shared for future researchers to reproduce results or extend the research work.

Floating PV Systems as an Alternative Power Source: Case Study on Three Representative Islands of Indonesia

Floating solar renewable energy is of enormous potential in Indonesia. This paper presents a comprehensive study of the design of Floating Photovoltaic (FPV) systems with Battery Energy Storage Systems (BESS) for three islands in Indonesia. These islands represent three typical scenarios in Indonesia (a) using a national grid powered by fossil fuel generators, (b) using a local grid powered by diesel generators, and (c) no grid at all. In-person surveys were conducted at these islands to collect data, and then FPV and BESS were designed to meet the demands of each island. Subsequently, the systems’ energy simulations were conducted using the System Advisor Model, demonstrating daily energy demand and supply in hour variation. Based on the results, a series of sustainability analyses were created from the aspects of economics, society, and the environment. The economic analysis demonstrated cost savings by using FPV to replace contemporary energy methods. The social analysis provides valuable insights into the local community, forming a demographic profile and obtaining perceptions and opinions regarding the new energy approach. The environmental analysis quantifies the potential CO2 emissions. Overall, the work provides valuable insights into the roadmap for implementing floating solar technologies in Indonesia which can also inform global ocean-based solar energy developments.

An Adaptive Local Grid Nesting-based Genetic Algorithm for Multi-earth Observation Satellites’ Area Target Observation

An Adaptive Local Grid Nesting-based Genetic Algorithm for Multi-earth Observation Satellites’ Area Target Observation

A New Cost-Effective Wind Farm Structure with HVDC Link Preserving Technical Advantages of Advanced offshore Wind Farms

In this paper a review of common wind turbine systems and wind farm configurations with AC and DC links is presented first, and then a new structure based on HVDC local grid is proposed and compared to the existing structures to show its effectiveness with respect to the older ones. The most important feature of the new structure is its lower cost, while it preserves controllability of the most flexible configurations like DFIG-based wind farms or wind farms with PMSG generators and back-to-back converters. The other feature of the proposed structure is its high efficiency, which is due to the use of direct driven multi-pole synchronous generators.

Heat transfer analysis in particle-laden flows using the immersed boundary method

This paper investigates an efficient immersed boundary method (IBM) for multiple-core CPU machines with local grid refinement for the calculation of heat transfer between fluids and finite-sized particles. The fluid momentum equations are solved by using the fractional step method, while the energy equation is solved by employing the second-order Adams-Bashforth method. For efficient load balancing between the CPU cores, the coupling between particles and fluid is obtained by applying the body force in the fluid equations, which depends on the solid volume fraction of particles contained in each grid cell, and then by linearly interpolating the particle temperature and velocity on the fluid grid cell (in place of the delta function commonly used in literature). Several test cases from the literature are studied, and good agreement is observed between the simulation results and the literature. Finally, a scaling study on multiple core machines is performed, demonstrating the proposed IBM's capabilities for a significant reduction in processing time.

Implementation and Adaptability Analysis of Numerical Simulation for Shale Oil CO2 Huff and Puff

Carbon dioxide (CO2) is being considered for use to enhance oil recovery and resource utilization and storage, with wide technical adaptability. In this paper, a numerical simulation method is used to study the adaptability of CO2 huff and puff in shale reservoirs. A fluid model introduces the nanoconfinement effect and reflects the nanoconfinement effect using the fluid p–T phase diagram. This method uses local grid refinement and changes the permeability near the grid to characterize the reservoir reconstruction volume (SRV) fracture network while considering the CO2 diffusion effect. The results indicate that by using the incremental recovery rate and oil change rate as references, adaptive charts can be obtained for different Kf/Km and oil saturation. When Kf/Km is 1000 and the increase in the CO2 recovery rate reaches 1.5%, the lower limit of oil saturation is 0.54. When Kf/Km is 1000 and the increase in the CO2 recovery rate reaches 2%, the lower limit of oil saturation is 0.57. When the oil saturation is 0.5 and the CO2 huff and puff oil change rate reaches 0.3, the lower limit of Kf/Km is 700. Finally, when the oil saturation is 0.548 and the CO2 huff and puff oil change rate reaches 0.6, the lower limit of Kf/Km is 10. The research results are significant and can guide the design and application of on-site CO2 throughput test plans.

A Practical Way to Balance Single Phase Loads in a Three Phase System at Distribution and Unit Level

The crucial worry in the production of electricity is to be certain that the supplied electricity meets international standards. The growing environmental alerts and the advancement in technology led to the integration of eco-friendly energy sources such as photovoltaic cells and wind turbines to local power grids. Although they provide additional power, the hazardous distribution of these sources in the grid does not benefit power quality measures. This, in addition to the un-linearity in consumption curves, make load balancing at distribution level a must to apply. To achieve the sought balance, load reconfiguration is the solution to be applied. This paper focuses on a practical way that rearranges the loads over the three phases at the unit itself. These changes guarantee electric bills drop and environmental benefits that result from fuel consumption reduction. Practical balancing (PB) is a switching mechanism that guarantees the loads are balanced according to constraints. The main difference between PB and previously proposed techniques such as the Phase commitment (PC) algorithm, The Heuristic (HE) method and the Modified Leap Frog optimization technique is that PB is implementable on real device while others are not. Using the practical balancing algorithm, the percentage of unbalance dropped to 0.38% and 0.43% for the same 15 and 150 loads testing systems used for the phase commitment algorithm. In addition, the average unbalance dropped to 1.6 A and 1.26 A, respectively and the neutral current dropped to 2.08 A and 1.9 A, respectively. The study was conducted on real data for different types of loads.

The Application of Deep Learning Methods in the Forecasting and Imputation of Solar Irradiance Data

Accurate solar radiation forecasts are necessary for solar power plants and local energy grids. Precise solar predictions can optimise plant operations and assist in managing power generation fluctuations. High-quality solar data are required to perform solar forecasting and may be accessed through open databases such as the Baseline Surface Radiation Network. Due to maintenance and malfunctioning equipment, these databases may have missing data. Deep learning methods can extract relevant features and non-linearities in data, which make them suitable for forecasting and imputation tasks. The development of the transformer architecture in 2017 marked an improvement from recurrent sequence processing using RNN (recurrent neural net) architectures to parallel sequence handling using self-attention mechanisms. Previous deep learning irradiance forecasting models utilised a RNN or RNN extension architecture. This paper presents novel applications of Transformer models to solar imputation and forecasting. Two deep learning architectures – Transformer and SAITS (Self-Attention-based Imputation for Time Series) – were trained to impute time series of global horizontal irradiance. Additionally, a Temporal Fusion Transformer (TFT) deep learning architecture was trained to forecast future values of global horizontal irradiance time series. Feature concatenation allows for the combination of differing exogenous variables into a single input vector for a deep learning solar forecasting model. Previous solar forecasting models do not incorporate cloud data or otherwise utilise an exogenous simple categorical mask to indicate cloud cover. In this paper, GOES-16 cloud optical depth and particle size datasets provide an improved representation of cloud properties. Classical imputation and forecasting models were also developed and used as baselines for comparison with deep learning models. The models were evaluated using standard statistical metrics for time series. It was found that the deep learning TFT forecasting model produced better forecasts than the classical regression model. However, the classical KNN imputer performed better than the two deep learning imputation models.

Fault Current Unified Calculation Method for Whole Process Fault Ride-Through of DFIG-Based Wind Farms

The present inaccurate fault current calculation, due to the incomplete consideration of whole process operation stages of fault ride-through (FRT) of DFIG-based wind farms (WFs), has a distinct impact on the safe operation of local power grid. To tackle this challenge, a fault current unified calculation (FCUC) method is proposed to achieve high-accuracy and high-speed mathematical analytical calculations of DFIGs output fault current during FRT. The proposed FCUC method mainly includes: 1) Whole process unified state space model, which contains transition stage, crowbar protection stage, demagnetization stage, reactive current compensation stage, and dc-chopper protection stage, is established to thoroughly consider FRTs different internal protection circuits and control strategies; 2) Stator output fault current is conducted by the unified state space model based on the stator residual voltage and the stator flux linkage; 3) Grid side converter (GSC) output fault current, which considers both injection mode and absorption mode, is developed based on the grid residual voltage and the unified state space model; 4) Fault current contribution mechanism, which is aggregated from both stator and grid side converter, is revealed based on Laplace transform from time-frequency-time domain, and is first expressed as an unified fault current expression. Extensive simulation/experimental/calculation results under different voltage sags have validated the correctness and effectiveness of the proposed FCUC method.

Examining the northern region of Iraq and the imperative for establishing photovoltaic power stations

The construction of a photovoltaic (PV) plant in the Iraqi province of Salah al-Din marks a significant step towards enhancing the region's energy infrastructure and transitioning towards sustainable, renewable energy sources. The project aims to harness the abundant solar resources in the area to generate clean and reliable electricity, contributing to both environmental sustainability and energy security. The chosen location, Salah al-Din province, is strategically positioned to receive ample sunlight, making it an ideal site for a photovoltaic installation. This solar plant is expected to have a considerable impact on the local energy landscape by diversifying the energy mix and reducing reliance on conventional, non-renewable sources. The construction process involves the installation of photovoltaic panels designed to capture and convert solar radiation into electricity. These panels, often mounted on support structures, form an array that maximizes exposure to sunlight. The energy generated by the PV plant is then fed into the local power grid, supplementing the existing energy supply. The benefits of this solar initiative extend beyond environmental considerations. The project is likely to create employment opportunities during the construction phase, boosting the local economy. Additionally, the operation of the photovoltaic plant will contribute to reducing greenhouse gas emissions, aligning with global efforts to combat climate change. Furthermore, the PV plant in Salah al-Din exemplifies Iraq's commitment to embracing renewable energy solutions as part of its sustainable development agenda. As the world transitions towards cleaner energy sources, projects like these play a crucial role in meeting the growing energy demand while mitigating the environmental impact associated with traditional energy generation. In conclusion, the construction of a photovoltaic plant in Salah al-Din energy a represents infrastructure, environmental sustainability, and energy resilience for the Iraqi province and contributing to the broader global shift towards clean and sustainable energy systems.

Optimal Dynamic Ancillary Services Provision Based on Local Power Grid Perception

Optimal Dynamic Ancillary Services Provision Based on Local Power Grid Perception

Operational characteristics of the combined heat and power plant in the district heating system of Belgrade

The combined production of electricity and thermal energy (combined heat and power or co-generation) is the most efficient and convenient approach to reduce costs for energy at industrial power plants and district heating plants that use natural gas as fuel to produce thermal energy for various needs. This paper analyses the operational characteristics of the combined heat and power plant, which has been operating since January 1, 2021, at the Vozdovac Heating Plant as part of the Belgrade district heating system. The combined heat and power plant consists of three gas engine units with a total nominal electric power of 10 MW and thermal power of 10.1 MW, which use natural gas as fuel. The combined heat and power plant is used for district heating and preparing domestic hot water while electricity is sold to the local electric grid. The analysis in this paper focuses on the plant?s operational characteristics: the number of working hours, the total energy consumption and energy production, the efficiency as well as the operational and maintenance costs. Also, the impact of the drastic changes in the prices of natural gas, electricity, and maintenance costs in the last year on the financial profitability of the combined heat and power plant was analysed in particular.

Integrated wellbore-reservoir-geomechanics modeling for enhanced interpretation of distributed fiber-optic strain sensing data in hydraulic-fracture analysis

Fiber-optic distributed strain sensing (FO-DSS) has been successful in monitoring strain changes along horizontal wellbores in hydraulically fractured reservoirs. However, the mechanism driving the various FO-DSS responses associated with near-wellbore hydraulic fracture properties is still unclear. To address this knowledge gap, we use coupled wellbore-reservoir-geomechanics simulations to study measured strain-change behavior and infer hydraulic fracture characteristics. The crossflow among fractures is captured through explicit modeling of the transient wellbore flow. In addition, local grid refinement is applied to accurately capture strain changes along the fiber. A Base Case model was designed with four fractures of varying properties, simulating strain change signals when the production well is shut-in for 10 d after 240 d of production and reopened for 2 d. Strain-pressure plots for different fracture clusters were used to gain insights into inferring fracture properties using DSS data. When comparing the model with and without the wellbore, distinct strain change signals were observed, emphasizing the importance of incorporating the wellbore in FO-DSS modeling. The effects of fracture spacing and matrix permeability on strain change signals were thoroughly investigated. The results of our numerical study can improve the understanding of the relation between DSS signals and fracture hydraulic properties, thus maximizing the value of the dataset for fracture diagnostics and characterization.