System Electrical Efficiency Research Articles

Improving Efficiency of Electric Energy System and Grid Operating Modes: Review of Optimization Techniques

Continuously growing tariff rates for energy carriers required to generate electrical and thermal energy bring about the need to search for alternatives. Such alternatives are intended for the reduction in the electricity and heat net costs as well as the expenses for the operation and maintenance of system elements and damage from power outages or deteriorated power quality. A way to reduce electricity and heat costs is the introduction of distributed energy resources capable of operating on both conventional (natural gas) and alternative (solar and wind energy, biomass, etc.) fuels. The problem of reducing electricity and, in some cases, heat costs are solved by applying mathematical optimization techniques adapted to a specific element or system of the industry in question. When it comes to power industry facilities, optimization, as a rule, includes reducing active power losses by controlling the system mode or specific power unit parameters; planning generating equipment operating modes; defining the optimal equipment composition; improving the regime and structural reliability of grids; scheduling preventive maintenance of equipment; searching for effective power unit operating modes. Many of the problems listed are solved using direct enumeration techniques; modern technical tools allow quickly solving such local problems with a large number of source data. However, in the case of integrated control over the power system or its individual elements, optimization techniques are used that allow considering a lot of operating limitations and the target function multicriteriality. This paper provides an analytical review of optimization techniques adapted to solving problems of improving the efficiency of the power facility operating modes. The article is made on the basis of the research conducted by the authors in the area of optimization of operating modes for electric energy systems and grids. The authors drew conclusions on the applicability of mathematical optimization methods in the power energy area. While conducting the research, the authors relied on their expertise in the development and introduction of the method to optimize the operation modes of energy supply systems with heterogeneous energy sources.

Research on cost analysis of new power system under dual carbon target

Under the influence of the concept of sustainable development, how to build a clean, low-carbon, safe and efficient modern electric power energy system is the focus of innovative development of new electric power enterprises. Especially after the proposed dual carbon target, new energy in various countries shows an explosive growth trend, and the traditional fossil energy power system begins to transform to a high proportion of new energy power system. Therefore, After integrating previous accumulated experience, China's electric power enterprises study the development path of new energy themed new power system from multiple perspectives. In this paper, based on the understanding of the current development status of new energy in China, according to the framework of new power system planning and development, the actual system cost expenditure is deeply discussed, and the future development trend is clarified based on the dual carbon development goal.

Research on cost analysis of new power system under dual carbon target

Under the influence of the concept of sustainable development, how to build a clean, low-carbon, safe and efficient modern electric power energy system is the focus of innovative development of new electric power enterprises. Especially after the proposed dual carbon target, new energy in various countries shows an explosive growth trend, and the traditional fossil energy power system begins to transform to a high proportion of new energy power system. Therefore, After integrating previous accumulated experience, China's electric power enterprises study the development path of new energy themed new power system from multiple perspectives. In this paper, based on the understanding of the current development status of new energy in China, according to the framework of new power system planning and development, the actual system cost expenditure is deeply discussed, and the future development trend is clarified based on the dual carbon development goal.

Solar PV Panels-Self-Cleaning Coating Material for Egyptian Climatic Conditions

The electrical efficiency of photovoltaic panels is affected by many environmental parameters, which have a negative impact on system electrical efficiency and cost of energy, dust and increased panel temperatures being the most serious in the MENA region. In this work, a few organic-based self-cleaning coatings are developed, and their effects on PVs’ electrical efficiency re assessed for polycrystalline panels exposed to natural soiling conditions outdoors at El-Sherouk City. The results show that monolithic hydrophobic-based coatings using paraffine and dimethyl-siloxane show up to 14.3% improvement in the electrical efficiency of the PV panels, but the role of nanoparticles TiO2 and Al2O3 addition needs further investigation. Hydrophobic-based coatings using dimethyl-siloxane reduce the coated panels’ surface temperature compared with the uncoated panel.

A Review of AC and DC Collection Grids for Offshore Renewable Energy with a Qualitative Evaluation for Marine Energy Resources

Marine energy resources could be crucial in meeting the increased demand for clean electricity. To enable the use of marine energy resources, developing efficient and durable offshore electrical systems is vital. Currently, there are no large-scale commercial projects with marine energy resources, and the question of how to design such electrical systems is still not settled. A natural starting point in investigating this is to draw on experiences and research from offshore wind power. This article reviews different collection grid topologies and key components for AC and DC grid structures. The review covers aspects such as the type of components, operation and estimated costs of commercially available components. A DC collection grid can be especially suitable for offshore marine energy resources, since the transmission losses are expected to be lower, and the electrical components could possibly be made smaller. Therefore, five DC collection grid topologies are proposed and qualitatively evaluated for marine energy resources using submerged and non-submerged marine energy converters. The properties, advantages and disadvantages of the proposed topologies are discussed, and it is concluded that a suitable electrical system for a marine energy farm will most surely be based on a site-specific techno-economic analysis.

Dynamic simulation modelling of reversible solid oxide fuel cells for energy storage purpose

The necessary integration of renewable based technologies in the current energy systems is leading to a faster development of energy storage technologies. As widely known, renewables suffer for unpredictability, and their massive utilization is significantly affecting grid stability and management. In this framework, the development of efficient and large electrical storage systems is becoming a pivotal point to achieve a stable electrical network based on renewables. This paper proposes a novel approach to reduce the energy excesses exported to the grid by a residential user equipped with a100 kW solar photovoltaic field. In particular, the electricity is stored as hydrogen by means of a 50 kW reversible solid oxide fuel cell. A comprehensive energy and economic simulation model of the system is proposed. In particular, a model of the reversible solid oxide fuel cell is developed in MatLab® and then integrated in TRNSYS17 for dynamic simulation purpose. Results showed that using the plant waste heat is crucial for improving fuel cell efficiency and plant energy performance. The proposed system achieves a reduction of the primary energy consumption by 74%. However, the proposed plant exhibits a poor economic profitability, with a payback period of 15 years.

Design and Performance of Armature Surface Coating for Electromagnetic Launcher

Armature is the key component of electromagnetic launcher (EML), but in the process of launching, its working environment is bad and the surface is seriously worn. Excessive wear will seriously weaken the mechanical properties of armature and affect the launching safety. Therefore, it is necessary to deal with the surface state of armature to reduce wear and improve the performance of armature. First, the properties of the candidate materials are analyzed. According to the principle of maximum current carrying capacity per unit mass, aluminum is the most suitable material for armature manufacturing. At the same time, the defects of material selection in single material system are pointed out. Second, based on the above problems, the surface coating design scheme is proposed. From the point of view of material melting point and hardness, it is proposed that tungsten can be used as the coating material for armature surface. According to the wear amount of armature tail under launch condition, the coating shape and thickness are designed. The best coating forming process is determined by calculating the shear force between coating and substrate; finally, the effect of the coating on the electric contact performance, system efficiency, and projectile gouging threshold velocity is analyzed. The results show that the maximum shear force between the coating and the substrate is above 171 MPa under the launching condition, and the laser cladding technology can meet the process requirements. After coating treatment, the contact resistance between the armature and rail (AR) increases by 6%, which has little effect on the system efficiency. Although it will affect the projectile gouging threshold velocity, it can be improved by modifying the tungsten coating or rail surface treatment. The analysis results are of great significance to reduce the armature wear, improve the contact performance between the AR, and improve the launch safety.

Photovoltaic/Thermal Module Integrated with Nano-Enhanced Phase Change Material: A Numerical Analysis

Solar photovoltaic-thermal (PV/T) technology is the main strategy for harvesting solar energy due to its non-polluting, stability, good visibility and security features. The aim of the project is to develop a mathematical model of a PV/T module integrated with optical filtration and MXene-enhanced PCM. In this system, a single MXene-enhanced PCM layer is attached between the PV panel and absorber pipe with solid MXene-PCM for storage and cooling purposes. Additionally, the thermal fluid is utilized in the copper absorber pipe and connected to the heat pump system for enhancing system thermal and electrical efficiency. Furthermore, the influences of the optical filtration channel height, concentration of the nanoparticles on PV surface temperature and overall system efficiency are also discussed. This study demonstrates that the annual thermal and electrical energy output can reach 5370 kWh per annum with 74.92% of thermal efficiency and 5620 kWh with 14.65% of electrical efficiency, respectively, compared to the traditional PV/T module. Meanwhile, when the optical filtration channel height and volume concentration are enhanced, they exert a negative influence on the PV surface temperature, but the overall thermal efficiency is enhanced due to low thermal resistance to heat losses and low radiation-shielding layers.

Solid oxide fuel cell systems in hydrogen-based energy storage applications: Performance assessment in case of anode recirculation

The application of solid oxide technology as a reversible system to renewable energy storage puts the attention on its operation and optimization under hydrogen feeding. To this aim, the effect of the anodic off-gas recirculation on the performance of a solid oxide fuel cell (SOFC) system fuelled with hydrogen is investigated. The layout presented includes the recirculation of anodic exhausts according to a variable rate, the condensation of the steam in the recirculated flow and the regeneration of the feeding flows. The operating parameters set in the 0-D developed model came from a test campaign aimed at determining SOFC performances varying the fuel utilization factor (Uf) and current density. In order to find the highest efficiency values, both fuel utilization factor and anode recirculation flow rate have been varied. Simulations results show the favorable effect on the system electrical efficiency for low utilization factor when operating with high anodic recirculate rates. With recirculation rates over 80 %, set the produced power, higher system energy conversion efficiencies up to 68.6 % are exhibited with lower cell Uf (down to 0.2). This design allows SOFC to overperform the best PEM performance recorded in literature.

Calculation of instantaneous line current of a three-phase network with an isolated neutral

The article focuses on the study of methods for calculating instantaneous line currents in a three-phase network with an isolated neutral, which is critical for improving the reliability, efficiency, and accuracy of monitoring and diagnostics of electrical systems. The developed method extends the capabilities of standard approaches to diagnostics and analysis, and it allows for more accurate analysis of instantaneous parameters in electrical networks and detection of faults in the operation of high-voltage electrical installations. The study used an integrated approach to analyzing and modeling the operating and emergency modes of a subway traction substation using a three-phase rectifier. Detailed power supply modeling and analysis of the harmonic components of line currents and voltages in the high-voltage network were performed. Various operating scenarios are modeled, including normal and emergency conditions when one of the diodes in the rectifier fails. It was found that the harmonic composition has significant changes in the event of a diode failure, which can be used to diagnose the condition of the equipment. The results can be used to optimize the design, operation, and maintenance processes in the urban electric transport sector and other industrial systems, reduce the risk of unforeseen accidents, and ensure the stability of electricity supply. Modeling has shown the effectiveness of the proposed method for detecting emergencies and improving the efficiency of traction substation maintenance. The proposed recommendations will help to improve the efficiency, energy efficiency, and reliability of electrical systems, in particular in the industrial sector and large infrastructure projects, providing a more stable and secure power supply.

Investigation on the thermal management of solar photo voltaic cells cooled by phase change material

Photovoltaic (PV) cells are used to convert solar energy into usable direct current as an output power source. Temperatures of PV module exceeding 25 °C reduce conversion rates by 0.4 to 0.65%/0C. In order to keep PV cells working at their optimal operating temperature, a variety of heat extraction systems have been developed. Another method that may be utilized for both heat absorption and temperature management is phase change material (PCM), which has a high thermal energy absorption capacity while also maintaining a constant temperature range throughout phase transition. One of the most efficient ways to absorb extra heat off the backside of solar panels is using PCM, which allows for improved energy efficiency. This article presents the findings of an experimental work of a PV system that includes a normal PV system, a PV system cooled with PCM, and a PV system cooled using nano phase change material (NPCM) for thermal management of the cell. Polyethylene glycol (PEG) 1000 with a melting temperature of 33-39 °C was employed as the PCM, while alumina and silica nanomaterial were used as the insertion materials in PCM. The findings indicate that adopting a PV-PCM, PV- Alumina nano phase change material (ANPCM), and PV-Silica nano phase change material (SNPCM) cooled system increases the system's electrical efficiency by 4.82, 8.1, and 7.17%, respectively, and increases power output by 5.12, 8.4, and 7.29%, respectively. In comparison to uncooled PV system, the panel temperature is lowered by 17.15%. Based on the findings, it seems that PCM and NPCM are effective means of controlling the temperature of PV solar cells.

Stability tool for electric power systems with a high penetration of electronic power converters

The increasing use of electronic converters is making possible the development of more sustainable, efficient, and reliable electric power systems, but it is also introducing new challenges that need to be addressed. Power system stability is one of them since the converter multiscale coupling between control loops and the mutual effects of multiple converters make the traditional approaches and specialized software available not fully adequate. In this context, this paper presents a software tool called CSTEP capable of carrying out small- and large-signal stability analysis for electric power systems strongly dominated by electronic converters. By utilizing the tool description, the paper provides the reader with a systematic methodology to obtain the system dynamic representation, and with some software tools for the analysis of the large and small-signal stability. Finally, the validity and functionality of CSTEP have been tested with the implementation of three use cases: a simple ac use case to illustrate the application of the system algorithm step by step, an IEEE 5-bus use case to validate the tool with already established commercial software and a more realistic system based on a medium voltage CIGRÉ benchmark to highlight the potential applications of the tool. The results show that, unlike existing tools that simplify or neglect the electric part of the grid (filters, line impedances, etc.), CSTEP can predict power system instabilities caused by the interactions of fast control loops of electronic converters with the electric part.

A very low charge potential for zinc-air battery promoted by photochemical effect of triazine-based conjugated polymer nanolayer coated TiO2

Photochemical-assisted rechargeable batteries are suffering from a high charge potential due to unfavorable surface charge kinetics of photochemical electrodes, that is surface defects induced energy loss. In this work, in-situ growing thickness-controlled polymer nanolayer on TiO2 nanorods electrode by a facile solvothermal reaction optimizes surface states conditions via mitigating oxygen vacancy induced hole trapping agents, while polymer nanolayer creates abundant active surface states that efficiently extract holes for photooxidation reaction. For modified photoelectrodes, 8 times improvement in interfacial charge transfer/recombination ratio (Kt/Kr) at a low applied bias contributes to a low onset potential (0.2 V vs. RHE) for photooxidation and shows 12 times improvement in photocurrent density at 0.4 V vs. RHE under simulated sunlight irradiation (AM 1.5 G, 100 mW cm−2) than that of r-TiO2, which contributes to the superior performance of a photochemical-assisted rechargeable Zn-air battery (PZAB). Equipping such a photoelectrode can photo-charge the battery at 10 mA cm−2 with a record-low potential of 0.8 V, saving 76.5% electrical energy. The electrode shows excellent stability for a 10-h cycling test. This work provides scientific thoughts and synthetic strategies for a highly efficient solar-rechargeable electric energy storage system and expands the scope of application for conjugated polymers.

Advanced metering infrastructure smart metering based on cloud architecture for low voltage distribution networks in application of smart grid monitoring

In most circumstances, accessing measurements from entire smart metres set in less-voltage grid area for distribution monitoring is not practicable because of less bandwidth as well as excessive delays in accessing Smart Meter monitoring. Estimating the condition of a distribution system can be done using voltage, active and reactive power measurements from smart metres subset. On one hand, increasing number of selected smart metres improves distribution state assessment accuracy, it degrades monitoring data time. It improves the electrical system's dependability and efficiency while also providing security to the system. Smart grid infrastructure is a modified form of smart grid. Smart grid infrastructure is a modified form of the smart grid. It has high-capacity converters, sensing and metering technologies, and automated control to improve efficiency and dependability. The goal of this article is to use smart metering technology to improve the observer of low-voltage distribution grids. The use of a distribution network-based state estimation technique employing smart metre readings for near-real-time monitoring of low-voltage distribution grids is the focus of this research. This paper propose smart metering based on cloud architecture for low voltage distribution networks with distribution network based state estimation algorithm in application of monitoring. The article will discuss the critical role of cloud solution in achieving interoperability, scalability and flexibility as well as enabling integration of various services for distribution system automation. As an example of coordinated operation of diverse distribution grid services by cloud, distributed state estimation technique as well as autonomous network reconfiguration will be demonstrated.

Performance of Bi-fluid PV/thermal collector integrated with phase change material: Experimental assessment

The main disadvantage of photovoltaic panels is their low efficiency at high temperatures which engages the researchers to cool the solar panels and store the excess heat for use in times of need. One of the techniques used is the storage of excess heat from photovoltaic panels using phase change materials. This study investigates the performance of a bi-fluid PV/thermal collector integrated with paraffin wax, air and water were used to cool the photovoltaic panels.Two systems were built to achieve this purpose: the first system is cooled using air and water, and the second system is similar to the first model with a phase change material behind the photovoltaic panel. Study results reveal that the photovoltaic panel temperature in the system containing a phase change substance is significantly lower than the temperature of the photovoltaic panel in the second system. Furthermore, the results showed that using the phase change material improves electricity production in all operating conditions and increases the overall system efficiency. For all cooling conditions, the system's total efficiency which using two coolants with and without phase change material were 80.29% and 59.01%, respectively. Moreover, the results proved that the use of the phase change material led to a significant increase in the system's electrical efficiency. The design with a phase change material had an electrical efficiency of about 11.06%. In contrast, the system without a phase change material had an electrical efficiency of about 9.96%.

Investigation of a DC voltage boost converter based on a multifunctional integrated electromagnetic component

The methods of functional integration of discrete electrical and electromagnetic components allow to increase the reliability and efficiency of electrical energy conversion systems, to reduce their weight and dimensions. The authors proposed a solution based on replacing some individual discrete components of a DC voltage boost converter with a multifunctional integrated electromagnetic component (MIEC). The component acts as an inductor and filter capacitor. A computer model of a DC voltage boost converter based on MIEC in the MatLab software package has been developed. The graphs of the output voltage are obtained. The circuits of step-up converters of constant voltage are analyzed. The optimal for the implementation of the replacement of the inductor and the filter capacitor with a multifunctional integrated electromagnetic component has been chosen. A circuit of a DC voltage boost converter based on MIEC is assembled. Oscillograms of the output voltage were taken. The analysis of the computer model and laboratory test sample was carried out.

Graphene Technology for Design Efficiency of the Solar Hybrid Electrical Cryoplane and Airships

The problems of introducing graphene technologies into the design studies of complex aviation solutions of minimal weight are relevant for the development of high-strength and lightweight composite structures with surface solar nano film energy storage for hybrid electric cryogenic aircraft (hydrogen cryoplanes LH2) and airships (disk-shaped Thermoplane MAI). The optimal design is directly related to the higher specific characteristics of liquid hydrogen fuel systems together with cryocooling systems, taking into account the use of new graphene-based materials and thin flexible solar cells, which is considered for SOLARSTRATOS and MAI projects or for any projects of hybrid electric aircraft/airships and their engines. A design analysis has been carried out to improve the design capabilities when introducing graphene technologies with their unique strength, electrical superconductivity, gas tightness and low mass in the component modification of a hybrid electric propulsion (HEP) and aero elastic energy-recoverable aircraft structures. The choice of rational design solutions using combined graphene composites, quartz dampers-vibration accumulators of structures and film solar energy cells allows you to reduce the weight of larger fuel tanks with liquefied hydrogen at high and low internal pressures and at the same time include electric motors in the cryocooling system – generators, power cables and batteries with additional solar energy charging, which increases the efficiency of on-board electrical systems and reduces the initial energy level and allows to increase energy efficiency and reduce weight costs during design studies.

Performance evaluation of a solid oxide fuel cell multi-stack combined heat and power system with two power distribution strategies

Solid oxide fuel cell (SOFC) combined heat and power (CHP) system is a promising candidate for future energy conversion systems. Large power SOFC-CHP system needs multi-stack fuel cell (MFC) to solve the problems of thermal stress and system stability because MFC systems can achieve better performances for maximum power output and average efficiency than single stack fuel cell systems. This study develops an energy management strategy (EMS) for a SOFC multi-stack CHP system coupled with a methane reformer. SOFC multi-stacks are connected in parallel and verified by the published results. The effect of pressure and temperature on the overall multi-stack CHP system electrical efficiency and heat power is investigated with chain and adaptive EMS. The results show that as temperature and pressure increase, the system power increases. The temperature is more effective for the multi-stack system peak efficiency. Up to 11% of electrical system efficiency can be improved when the temperature rises from 700 °C (973 K) to 900 °C (1173 K). However, higher pressure reduces the peak efficiency by 1.5%. Both temperature and pressure can enlarge the output power range. The proposed model can serve as an effective solution for optimizing the SOFC multi-stack CHP system running on methane.

Harmonic Analysis of Electric Transmission System of New Energy Vehicle

In order to improve the cruising range of new energy electric vehicles and solve the low efficiency of electric transmission system in low-speed driving stage, a space vector pulse width modulation algorithm is proposed. The simulation model is established by Matlab/Simulink software, and the test parameters of electric transmission system in the actual driving process of new energy electric vehicle are analyzed, and the harmonic distribution of line voltage of electric transmission system and the influence of battery bus voltage on harmonic content are explored. The actual test results show that reducing the difference between the bus voltage and the fundamental line voltage under actual electric transmission can reduce the harmonic content and improve the system efficiency. According to the characteristics of power generation system, a reliable motor optimization scheme is proposed to reduce harmonic content to improve the efficiency of electric transmission system of new energy vehicles.

Heat transfer and pressure drop through mono and hybrid nanofluid‐based photovoltaic‐thermal systems

AbstractUsing nanofluids in photovoltaic‐thermal systems enhances the overall efficiency; however, increasing the pressure drop and pumping power, because of the higher viscosity of nanofluids, is a challenging factor for the nanofluid‐based systems. In the present study, the thermohydraulic performance of the photovoltaic‐thermal system is compared using two water‐based nanofluids including hybrid Ag‐MgO and carbon nanotubes (CNT) nanofluids, as the working fluids. The effect of type and flow rate of the working fluid, nanoparticle concentration, and channel height on the friction factor and Nusselt number is studied using the numerical model. The model is validated using the experimental and numerical results and found that the relative errors of the results are less than 3.8% and 5.2%, respectively, which confirmed the model accuracy. The results showed that at a flow rate of 8 L/h, the volume fraction of 2%, and channel height of 10 mm, the system electrical efficiency, thermal efficiency, and friction factor using CNT nanofluid are, respectively, 0.04%, 1.31%, and 62% higher than those using base fluid and 0.03%, 0.89%, and 53% higher than those using Ag‐MgO nanofluid. It is also found that although increasing the nanoparticle concentration and decreasing the channel height improves the system efficiency, it increases the friction factor and pressure drop. Comparing the results using the mono and hybrid nanofluids showed that the thermal performance of the photovoltaic‐thermal system using CNT nanofluid is slightly better; however, the hydraulic system performance using hybrid Ag‐MgO nanofluid is improved.