Optimal Operation Research Articles

Optimal control strategies for energy storage systems for HUB substation considering multiple distribution networks

With the global consensus to achieve carbon neutral goals, power systems are experiencing a rapid increase in renewable energy sources and energy storage systems (ESS). Especially, recent development of hub substations (HS/S) equipped with ESS, applicable for resolving site constraints if implemented as mobile transformers, is expanding the development of ESS-equipped facilities. However, these units require centralized control strategies considering variability within integrated networks. While studies on electric vehicle charging considering the variability of renewable energy or load are widely studied, ESS management scheme for individual substations requires further optimization, especially considering the state of distributed sources at lower levels and transmission system operators. Thus, in this study, an optimal control approach for ESS located at the connection point of transmission and distribution systems, including further consideration of the loss in distribution lines and the constraints of renewable energy sources is presented. This study attempts to derive proactive control strategies for ESS in HS/S to operate with various distribution networks. By establishing control priorities for each source through optimal operation strategy, a suitable capacity of ESS and its economic benefits for distribution network management can be examined. Validation of the current analysis results is performed by utilizing MATPOWER. By adapting the operational range of design scenarios, diverse distribution systems can be tested against multiple configurations of connected devices.

Globalization of distributed parameter self‐optimizing control

AbstractNumerous nonlinear distributed parameter systems (DPSs) operate within an extensive range due to process uncertainties. Their spatial distribution characteristic, combined with nonlinearity and uncertainty, poses challenges in optimal operation under two‐step real‐time optimization (RTO) and economic model predictive control (EMPC). Both methods necessitate substantial computational power for prompt online reoptimization. Recent local distributed parameter self‐optimizing control (DPSOC) achieves optimality without repetitive optimization. However, its effectiveness is confined to a narrow range around a nominal operation. Here, globalized DPSOC is introduced to surmount the limitation of the local DPSOC. A global loss functional concerning controlled variables (CVs) is formulated using linear operators and Fubini's theorem. Minimizing the loss with a numerical optimization procedure yields CVs exhibiting global optimality. Maintaining these CVs at constants ensures such a process has a minimal average loss in a large operating space. The effectiveness of the proposed method is substantiated through a transport reaction simulation.

Optimal operation of co‐phase traction power supply system with HESS and PV

AbstractThe co‐phase traction power supply system (TPSS) with hybrid energy storage system (HESS) and photovoltaic (PV) is proposed to eliminate the neutral section and improve the regenerative braking energy (RBE) utilization. Although the integration of HESS and PV facilitates the energy saving and cost reduction of the co‐phase TPSS, the high cost and configuration of HESS should be considered, which is the key to affect the optimal operation strategy of co‐phase TPSS. Here, the optimal operation strategy of co‐phase TPSS with HESS and PV is proposed to design the HESS configuration, recycle RBE and improve power quality. The proposed model aims to minimize the total system cost, including HESS investment cost, electricity cost and operation and maintenance cost. Moreover, the proposed model is formulated as a mixed integer linear programming by employing linearization approaches. Finally, case studies verify that the 29.2% cost reduction rate is achieved and the three‐phase voltage unbalance meets the standard requirements.

Electro-nitrification coupled with biological denitrification achieves efficient nitrogen removal from rare earth mine ammonia-nitrate wastewater

Nowadays, ammonia-nitrate wastewater has been posed serious environmental hazards. Electrochemical ammonia oxidation (AOR) technology with environmentally friendly and easy-to-operate features has attracted much attention. In this work, a novel anode catalytic electrode (Ni1Cu1Fe0.5-S/Ti) is prepared by a one-step electrodeposition method for electro-nitrification, and coupled a biological denitrification device for the treatment of real ammonia-nitrate wastewater. The unique three-dimensional layered spherical structure of Ni1Cu1Fe0.5-S/Ti electrode has been verified through physical characterization, and electrochemical tests demonstrated that Ni1Cu1Fe0.5-S/Ti electrode gained an excellent current density of 54.48 mA·cm−2 toward to AOR at 0.65 V vs. Hg/HgO as well as good stability for four times repeated electro-nitrification experiments. The optimal experimental operating conditions were obtained by changing electrode spacing, initial NH4+-N concentration, current density and flow rate. Consequently, 97.7 % total nitrogen (TN) removal efficiency of real wastewater is achieved through electro-nitrification coupled with biological denitrification, providing a new perspective technology for ammonia-nitrate wastewater treatment.

Ultra-sensitive CuAl2O4 Nanoflakes for ppb level detection of Isopropanol

Trace-level detection of isopropanol is important for human health monitoring and air quality surveillance. In this work, we report synthesis of high surface area two-dimensional (2D) nanoflakes of CuAl2O4 using surfactant-assisted hydrothermal process and its application in ppb level detection of isopropanol. X-ray diffraction revealed the polycrystalline nature of the spinel and a nano crystallite size of 42 nm. The 2D morphology of CuAl2O4 was confirmed using field emission scanning electron microscope whereas BET revealed the mesoporous nature and a high surface area of 41.8 m2g-1. The surface oxidation states of the material were found through X-ray photoelectron spectroscopy. The 2D CuAl2O4 demonstrated excellent sensing towards isopropanol with its response varying from 11.8 to 84.5 % (500 ppb–10 ppm) at 300 °C. The limit of detection of the spinel was found to be 56 ppb at its optimum operating temperature of 300 °C. In addition, the sensing layer was found to have response times in range 1101 s for 500 ppb to 168 s for 10 ppm and recovery times in the range 300 s for 500 ppb to 570 s for 10 ppm.

Green approach for fabricating hybrids of food waste-derived biochar/zinc oxide for effective degradation of bromothymol blue dye in a photocatalysis/persulfate activation system

This study presents novel composites of biochar (BC) derived from spinach stalks and zinc oxide (ZnO) synthesized from water hyacinth to be used for the first time in a hybrid system for activating persulfate (PS) with photocatalysis for the degradation of bromothymol blue (BTB) dye. The BC/ZnO composites were characterized using innovative techniques. BC/ZnO (2:1) showed the highest photocatalytic performance and BC/ZnO (2:1)@(PS + light) system attained BTB degradation efficiency of 89.47% within 120 min. The optimum operating parameters were determined as an initial BTB concentration of 17.1 mg/L, a catalyst dosage of 0.7 g/L, and a persulfate initial concentration of 8.878 mM, achieving a BTB removal efficiency of 99.34%. The catalyst showed excellent stability over five consecutive runs. Sulfate radicals were the predominant radicals involved in the degradation of BTB. BC/ZnO (2:1)@(PS + light) system could degrade 88.52%, 84.64%, 81.5%, and 77.53% of methylene blue, methyl red, methyl orange, and Congo red, respectively. Further, the BC/ZnO (2:1)@(PS + light) system effectively activated PS to eliminate 97.49% of BTB and 85.12% of dissolved organic carbon in real industrial effluents from the textile industry. The proposed degradation system has the potential to efficiently purify industrial effluents which facilitates the large-scale application of this technique.

Performance analysis and prediction of a modified precompression transcritical CO2 power generation cycle

The efficient utilization of biomass energy and the optimal operation of integrated renewable energy sources in virtual power plants have become critical issues to achieve carbon neutrality targets in rural areas. In the rural areas of Northeast China, a large amount of electricity can be generated from biomass. It is very important to develop biomass power generation equipment for this rural area. Due to the high thermal efficiency and its compact system without freezing process like water, CO2 thermal cycle is an appropriate option for this kind of power generation equipment. According to whether the flow is separated, CO2 cycles can be divided into the single flow layouts and split flow layouts. Compared to the single flow layouts, split flow layouts have higher efficiency, but more complex structures and lower heat transfer power per unit area. Considering the climatic characteristics of Heilongjiang Province and the seasonality of straw biomass utilization, this study proposes a modified scheme for the precompression transcritical CO2 cycle in the single flow layout to meet the simple structure requirement of the small power plants in cold areas like Northeast China. Through energy analysis, the study calculates the thermal efficiencies of the two cycles when the inlet pressure of the main compressor is 5 MPa, the turbine inlet temperature is 550 °C and the pressure ratios of the main compressor are in the range of 4.5–5.5. The optimal efficiency of the traditional precompression cycle is 43.55 % when the main compressor pressure ratio is 5.5, while the modified precompression cycle is 44.86 % when the pressure ratio is 5.0266. The modified precompression cycle has a higher efficiency than the traditional precompression cycle at a lower pressure ratio of the main compressor.

Enhancement of n-butanol sensing performance of porous ZnO flakes by decorating Ag nanoparticles

This study designs to investigate a high-performance n-butanol gas sensor with a porous morphology. Porous ZnO flakes modified with Ag particles are prepared in two steps using hydrothermal and precipitation methods. Morphological analysis of the samples shows that the ZnO flakes were covered with mesopores with high porosity, and their edge lengths ranged from 3 μm to 6 μm, with a minimum thickness of 11.3 nm. Through rigorous gas sensing testing, we find that the optimal mass percentage Ag-ZnO sensor provided significantly better sensing behavior, with a 100.8 response for 100 ppm n-butanol, compared to 14.5 for the pure ZnO sensor, a 5.95-fold improvement. In addition, the sensor's optimal operating temperature is reduced from 290 °C to 190 °C, increasing its adaptability and versatility in practical applications. In subsequent tests, it is found that this Ag-ZnO sensor not only shows excellent selectivity to n-butanol but also favorable stability, with no significant degradation during 30 days of continuous testing. The experimental analysis shows that the formation of porous flake structure and the modification of Ag particles are effective approaches to improve the ZnO gas sensor.

Performance and biotoxicity of electro-Fenton treatment of bisphenol A: Evaluation of copper recovered from microbial fuel cell cathodes for subsequent catalytic applications

A three-tank microbial fuel cell (MFC) is successfully constructed to achieve electromigration and is used in the electro-Fenton process to treat bisphenol A (BPA). The MFC system exhibits excellent mobility and efficiently aggregates Cu+ to the cathode. Under optimal operating conditions, the MFC achieves a maximum power density of 31.4 mW/m2, which is a 3.4-fold increase over that at 0.5 kΩ. Increasing the external resistance increased the MFC power output (ca 1.5 times) and copper ion migration (ca 4.6 times) while reducing the internal resistance of the system (ca 25.3 %). Surface analysis of the cathode carbon cloth shows a 5.5-fold increase in copper content at 1 kΩ over that at 0.5 kΩ. This also increases the oxygen reduction reaction rate, thereby increasing the H2O2 yield by 1.5 times. The recovered copper cathode at 1 kΩ exhibits the best catalytic degradation of BPA, removing 99.7 % of BPA in 180 min, increasing 1.4 and 1.8 times that obtained at 1.5 and 0.5 kΩ, respectively. The optimal operating conditions significantly increased the abundance of electrochemically active bacteria (Azospirillaceae) (3.2 %−41.7 %), indicating that the optimized MFC is favorable for the rapid acclimatization of electrochemically active bacteria.

Risk-benefit comparative analysis of different control methods for reservoirs under the water to electricity mode

Abstract For some small hydropower stations that are not under the control of power dispatching department, there are many ways to implement the reservoir operation scheme formulated under the premise of determining power by water. This paper respectively selects the output, flow and water level process as the control conditions, explores the risks and benefits of reservoir operation with different control variables, and selects the optimal operation scheme through comprehensive comparative analysis. Simulation results of a hydropower station in the Han River Basin show that when the output is taken as the control condition, the waste water is small, the power generation benefit is high, and the risk of the water level outside boundary is within the acceptable range. Considering the risk and benefit of reservoir operation and taking output as the control condition, it has significant advantages over water level and flow.

A hybrid SATS algorithm based security constrained optimal power flow using FACTS devices

In the realm of power systems, achieving optimal operation while ensuring security remains a paramount challenge. The security constrained optimal power flow (SCOPF) problem deals with optimizing power system operations while taking into account security limitations. Flexible alternating current transmission system (FACTS) is a system consisting of static equipment used for transmitting electrical energy in the form of AC. The static synchronous series compensator (SSSC) is a specific form of series FACTS device. The unified power flow controller (UPFC) is a FACTS device that is connected in parallel and series with a transmission line. In this research, hybrid simulated annealing and tabu search (hybrid SATS) algorithm is designed to solve SCOPF problems that involve use of FACTS devices. The combination of simulated annealing and tabu search is intended to improve algorithm's pace of convergence and the quality of its solutions. Hybrid SATS with FACTS devices are used to investigate line flow limit violations during single line failures and ensure power flows remain within their security limitations. The efficacy of proposed algorithm is demonstrated through case studies utilizing IEEE 30 bus system. These case studies demonstrate algorithm's capabilities to achieve optimal and secure power system functioning to demonstrate its effectiveness.

Fabrication of Laminated Electrospun Fire˗Resistant Phosphorylated Poly(Vinylalcohol) Membrane for Enhanced Firefighter Safety

AbstractThe current study focuses on the creation of breathable and fire˗retardant fibrous membranes using phosphorylated poly(vinylalcohol) (PPVA) via the electrospinning method, with a specific interest in their application for structural firefighter clothing. Poly(vinylalcohol) (PVA) was phosphorylated to enhance its inherent flame resistance. Optimization of reaction conditions, including time and temperature, was conducted to achieve a solution suitable for electrospinning. The flame resistance of PPVA was confirmed through vertical flammability tests, with thermogravimetric analysis indicating a significant increase in carbonaceous char formation during PPVA decomposition compared to unmodified PVA. The limiting oxygen index also exhibited a notable increase from PVA to PPVA. Furthermore, the study established optimal operating conditions for producing uniform fibers, considering parameters such as polymer concentration, feed rate, tip to collector distance, and applied potential difference. The PPVA membrane demonstrated superior water vapor transmission rates compared to PVA, indicating enhanced breathability. The entire fabrication process utilized an environmentally friendly water‐based solvent. Additionally, a moisture‐cum‐thermal barrier layer (MCTB) was developed by laminating the PPVA fibrous membranes with microporous polytetrafluoroethylene and further with needle punch‐spunlaced OPAN fabric. Experimental assessments of the MCTB layer revealed satisfactory breathability and thermal performance, surpassing the standard requirements of 35 cal/cm2 for structural firefighting configuration.

Wire-to-two-drop plasma thruster: Experimental and numerical investigation of electroaerodynamic jet flow for micro aerial vehicle propulsion

Conventional micro aerial vehicles (MAVs) have primarily relied on complex, flapping-wing mechanisms for propulsion, often exhibiting limitations in terms of reliability and efficiency. To overcome these challenges, this study explores the potential of electroaerodynamic (EAD) thrusters as a novel propulsion system. By accelerating air molecules through ion collisions, EAD jet flow generates thrust, offering advantages such as noiseless operation and zero emissions due to its moving-part-free design. This research presents a comprehensive experimental and numerical investigation of a wire-to-two-drop thruster configuration to elucidate its electromechanical performance, plasma flow dynamics, and EAD jet characteristics. Experimental measurements of key parameters, including current, thrust, power, and effectiveness, were correlated with numerical simulations, demonstrating excellent agreement with a maximum error below 5%. These findings align strongly with established theoretical frameworks, revealing an inverse square root relationship between effectiveness and thrust. To optimize thruster performance, optimal operating voltages were identified at approximately 8.2, 9.4, and 11.6 kV for inter-electrode gap distances of 10, 15, and 20 mm, respectively, achieving a balanced trade-off between thrust and effectiveness. Detailed numerical visualizations of the plasma flow field, including velocity distribution, jet morphology, potential distribution, and electric field lines, provided valuable insights into the thruster's operation. Building upon these insights, a proof-of-concept EAD flier was constructed and tested, incorporating a serrated emitter electrode and lightweight materials. This flier achieved a mass of 0.5 g and generated a thrust of 0.77 g at 15 kV, resulting in a thrust-to-weight ratio of 1.54 and successful liftoff. This demonstration highlights the potential of EAD propulsion for practical MAV applications.

Digital Twin-driven Health Operation and Maintenance Strategies for Complex Equipment with Self-healing Capabilities

With the development of the industrial level, the service-oriented transformation of the manufacturing industry has become a new growth point for the interests of the manufacturing industry recognized by all countries, and in this transformation process, the health operation and maintenance (HOM) of equipment has become a crucial link, especially for complex equipment, and its health operation and maintenance level directly affects the overall efficiency of the manufacturing industry. However, with the improvement of intelligence and complexity, a more general and complete set of methods and theories is needed for the healthy operation and maintenance of complex devices with self-healing states. Based on an in-depth analysis of the key issues of complex equipment health operation and maintenance, this paper introduces digital twin technology as a breakthrough. Digital twins provide new ideas for the healthy operation and maintenance of complex equipment. By defining a digital twin-driven PHM (Prediction and Health Management) framework, this paper not only solves the problem of mobility (i.e., virtual and real connection) of the cross-platform health operation and maintenance model, but also focuses on improving the accuracy and evaluation indicators of the model (the consistency between the virtual model and the entity). Addressing issues of strategy development and effectiveness evaluation. Based on the digital twin technology, a general model was established, and the self-healing phenomenon and different maintenance strategies were introduced to explore its impact on reliability. Based on the game idea, the reliability model is used to evaluate different maintenance strategies. So as to develop the optimal operation and maintenance strategy. This not only improves the accuracy and efficiency of O&M, but also provides a solid theoretical foundation and technical support for the intelligent and autonomous health O&M of complex equipment.

Innovative approaches to optimizing Li-Ion battery cooling performance using gas mixtures

This study investigates the critical issue of thermal management in lithium-ion batteries, a vital concern for enhancing battery performance, safety, and longevity. While more complex cooling systems like liquid cooling, phase change materials, and two-phase systems offer superior thermal performance due to their higher heat transfer capabilities, they come with significant drawbacks. These include increased system complexity, higher costs, added weight, and the potential for leaks or other failures that can compromise safety and reliability. Consequently, simpler air-based cooling systems are often preferred in many applications, despite their inherently lower h coefficient. To bridge the performance gap between air and liquid cooling without resorting to complex engineering solutions, this study focuses on enhancing the h coefficient of air-based systems using innovative refrigerant gas mixtures. The use of refrigerant gas mixtures, specifically a blend of R1234ze(E), nitrogen, and neon, as an alternative to traditional cooling methods was explored. The study employed a comprehensive FEM model and experimental validation to evaluate free and forced convection in a slender, vertical cylindrical configuration. To analyze the impact on convective heat transfer, the key parameters CRate, T0 and Tamb were systematically varied. A dimensionless analysis then evaluated how thermodynamic properties influence h coefficient. This analysis led to the derivation of a dimensionless heat transfer function h(ρ, Cp, k, μ). The study aimed to significantly improve the efficiency of h by optimizing the gas mixture properties. The “Mixture Study” identifies the optimal refrigerant composition, where a specific mixture α of 86 % R1234ze(E), and 14 % neon demonstrated the best balance between heat transfer efficiency and enhanced thermal capacity. The heat transfer coefficient increases by around 65 % during natural convection and by around 80 % during forced convection. The percentage reduction of the thermal difference in temperature reaches approximately 10 % with a maximum of 4 K in natural convection conditions and a maximum of 36.5 % and a reduction of approximately 10 K compared to air cooling alone, effectively maintaining the battery within the optimal operating range of 293.15 K to 333.15 K. Notably, this composition increased the thermal power absorbed by the mixture by over 100 % under the same thermal difference. This research therefore provides valuable insights for developing more effective gas cooling strategies that ultimately enhance the performance, safety, and durability of batteries in various applications. By integrating the benefits of both cooling methods, the study paves the way for innovative thermal management solutions in battery technology.

Simulation analysis of low-temperature heat generation of power batteries based on the ECM model

Abstract When the power battery operates in low temperatures, it encounters challenges with charging and discharging, leading to a decline in battery performance, which can prevent electric vehicles from starting and reduce their driving range. To address this, the battery must possess the capability to adapt to both extremely high and low temperatures. This article employs ANSYS software to investigate the heat generation in batteries due to their own charging and discharging processes at different discharge rates under -20°C. When the battery is heated at a 1 C discharge rate for 20 minutes, its temperature rises by approximately 1.1°C; at 2 C, the temperature rises by about 5°C; and at 3 C, it rises by about 11°C. The greater the discharge rate is, the more heat is generated, resulting in a higher temperature rise. Furthermore, prolonged heating at a certain discharge rate can elevate the temperature to a level that is optimal for lithium-iron-phosphate batteries, ultimately reaching their optimal operating range. This research contributes to enabling lithium-ion power batteries to function normally in low-temperature environments, without compromising their lifespan. It is imperative to heat the interior of lithium-ion power batteries to ensure they can start normally after prolonged overnight parking, through preheating.

Effective battery pack cooling by controlling flow patterns with vertical and spiral fins

Battery Thermal Management System (BTMS) is essential for dissipating heat and controlling temperature distribution within the battery pack of an electric vehicle to maintain its optimal operating temperature. This research focuses on the influence of cooling fins in achieving balanced temperature distribution inside the battery pack. Vertical and spiral fins are attached around 21,700 cylindrical cells for this investigation. ANSYS FLUENTsoftwareis employed to conduct the numerical simulations, where a finite volume approach is used to solve the mass conservation, Navier–Stokes, and energy transport equations. The study also uses a set of polynomial functions to calculate the heat generation inside the cells. It assesses the effects of the Reynolds number, fin loop number, and outlet section of BTMS at numerous discharge rates. The findings indicate that the spiral fins significantly impact the thermal performance, reducing Tmax by 21.31 % due to the enhanced flow circulations within the BTMS. A high Reynolds number also positively affects Tmax by reducing the temperature uniformity caused by the shorter time for air-cooling contact with the cell surfaces. More specifically, at a Reynolds number ≥9433, a Z-type BTMS with the spiral fins can maintain the temperature uniformity at a temperature difference of 5 °C. Among the six different BTMSs analysed, a U-type BTMS is reported to have the best performance, reducing Tmax and ΔTmax by 4.11 % and 38.1 %, respectively. The pressure drop in this case is also reduced by 8.46 %, thus lowering the overall power consumption.

Development of Enhanced Computer Vision-based Monitoring Technology to Respond to Fire Accidents at Electric Vehicle Charging Stations

Owing to the recent popularity of electric vehicles (EVs), EV charging facilities have become mandatory, and charging stations that use electricity produced from renewable energy sources are being actively installed in buildings and apartments. As the number of these charging stations increases, the possibility of EV batteries overheating and causing a fire, which may spread and cause damage, also rises. However, current domestic and foreign studies do not suggest new and renewable energy supply or fire reduction measures for the supply of EVs. Therefore, to propose new-renewable energy EV charging stations for urban disaster prevention, in this study, we review EV charger installation cases, eco-friendly new renewable energy-based charging stations, and AI-based fire monitoring systems and analyze their characteristics through optimal operation. Through the fire prevention system developed in this study, we anticipate a novel approach for building a safer and more sustainable green energy supply system.

Outstanding Potential for Treating Wastewater from Office Buildings Using Fixed Activated Sludge with Attached Growth Process

The application of fixed activated sludge with an attached growth process (FASAG) with optimal operating conditions (hydraulic retention time (HRT) of 7 h, dissolved oxygen (DO) of 6 mg/L, and alkalinity dosage of 7.14 mgCaCO3/mgN-NH4+) treats wastewater generated from office buildings to meet discharge requirements (as per the regulation in the nation where the study was conducted) with typical parameters such as pH of 6.87–7.56, chemical oxygen demand (COD) of 32–64 mg/L, suspended solids (SS) of 8–11 mg/L, N-NH4+ of 1–7 mg/L, and denitrification efficiency reaches 53%. In addition, the FASAG is an outstanding integration that makes both economic and environmental sense when applied in local wastewater treatment systems. In particular, this process combines aerobic and anoxic processes in a creation tank. This explains why this approach can save investment and operating costs, energy, and land funds. In office building regions, where land area is frequently limited, saving land funds presents numerous options to enhance the density of green cover. Furthermore, as a new aspect, investing in reusing wastewater after treatment to irrigate plants or flush toilets in office buildings contributes to a decrease in the quantity of wastewater released into the environment, saving water resources and supporting sustainable development.

Enhanced acetone gas sensor via TiO2 nanofiber-NiO nanoparticle heterojunction

We present a high surface area sensor comprising NiO nanoparticles (NPs) incorporated within porous TiO2 nanofibers (NFs), showing a remarkable response to acetone. Initially, we synthesized Polyvinylpyrrolidone (PVP) NFs containing titanium (Ti) and nickel (Ni) salts using a simple electrospinning method. Subsequent calcination of the PVP NFs led to the formation of NiO NPs embedded within the porous TiO2 NFs. The resulting heterostructure material exhibited a significant response to acetone detection, with a ratio of electrical resistance in air (Ra) to that in the presence of gas (Rg) reaching 83 at its optimal operating temperature of 300 °C. Furthermore, it demonstrated stable performance under high relative humidity conditions.