kW In Order Research Articles

Systematic Evaluation of Possible Maximum Loads Caused by Electric Vehicle Charging and Heat Pumps and Their Effects on Common Structures of German Low-Voltage Grids

In this paper, we present a comprehensive assessment of the effects of residential loads, electric vehicles (EVs), and electric heat pumps (HPs) on low-voltage (LV) grids in urban, suburban, and rural areas of Germany. Firstly, real data are used to determine the typical structures for each LV grid region. Secondly, nine scenarios are defined with different levels of EV and HP penetration. Thirdly, the Low Voltage Load Flow Calculation in the DIgSILENT PowerFactory is performed for all scenarios while taking the simultaneity factor (SF) for each load type into consideration to calculate the minimum voltage and maximum loadings of transformer and lines in each grid; this allows for the grid’s potential bottlenecks to be identified. The network simulations are carried out with the consideration of charging powers of 11 kW and 22 kW in order to evaluate how an increasing EV load in the future may affect the grid’s parameters. To the best of our knowledge, no study in the literature has simultaneously addressed all of the aforementioned topics. The results of this study provide a useful framework that distribution system operators (DSOs) may apply to anticipate the forthcoming challenges and figure out when grid reinforcement will be required.

A hybrid IMFO-fuzzy algorithm for performance enhancement of microgrid under uncertainty via DGs integration and reconfiguration

Microgrids (MGs) are distributed generation and distribution systems that include distributed generation (DG) units, energy storage systems (ESSs), distributed reactive sources (DRSs), and resilient loads that can operate in either connected or isolated modes. When dealing with uncontrolled DGs such as Wind Energy Systems (WES) and Photovoltaic Energy Systems (PVES), MGs planners have a difficult time making decisions. The work proposed in this paper addresses three interconnected works: (i) the implementation of a rigorous hybrid optimization approach for reconfiguration and DGs placement; (ii) the performance investigation under uncertain behavior of RES-based DGs and demand; and (iii) performance enhancement realization through the replacement of hybrid DGs for RES-based DGs. An Improved Moth Flame Optimization (IMFO), which is a multi-objective optimization method, has been linked with fuzzy logic in order to handle multiple objectives in an efficient manner. These objectives include the minimization of voltage deviation, the reduction of generation cost, and the reduction of loss. The quality of the power, the amount of money saved by consumers, and the benefits to the Distribution System Operator (DSO) might all be improved with the help of a hybrid algorithm. This research is also extended to address the uncertainties of RES-based DGs by replacing hybrid DGs in the most optimal locations. IEEE 33 bus RDS is used to test radial distribution system (RDS) microgrids. For validation purposes, uses 24-hour load patterns to mimic WES and PVES’ 24-hour load dispatching behavior. The research findings clearly demonstrate the advantages of microgrids over traditional architectures. The hybrid DG requires an average generating cost of 185.33 $/kW in order to produce 100 kW of power throughout the day with significantly reduced emissions.

Optimizing a microgrid photovoltaic-fuel cell energy system at the highest renewable fraction

The current research examined the usage of fuel cells as an energy storage unit to increase renewable energy self-consumption in microgrid energy system applications. The studied model is comprised of photovoltaic modules and a fuel cell that serves as the energy storage unit. The study was conducted in 2020, utilizing real-time weather and electrical load data with a one-minute temporal resolution. The daily average energy consumption for the analyzed household was 10.1 kWh, with a peak power output of 5.3 kW, and the yearly energy consumption was 3755 kWh. The investigated photovoltaic system has a capacity of 2.7 kWp (6 modules at 0.45 kWp/module), and the fuel cell capacity is in the range of 0–3 kW in order to obtain optimal integration with the photovoltaic system to get maximum renewable energy fraction utilization. The findings indicate that using fuel cells powered by hydrogen generated by renewable energy systems can significantly increase self-consumption and self-sufficiency. The annual results showed that the use of 2.5 kW fuel cells can increase renewable fraction utilization from 0.622 to 0.918 with a 2.5 kW fuel cell, and energy self-consumption can reach 3338.2 kWh/year, an increase of 98.4%, and energy self-sufficiency can reach 3218.8 kWh/year, an increase of 94.41%. The results obtained demonstrate that the proposed photovoltaic fuel cell energy system provides a viable option to run semi-autonomous or fully autonomous applications in a self-sustaining medium at a percentage of 95%. Furthermore, the economic aspect is analysed for the optimal system configuration. • For greenhouse applications, a hybrid energy system with a robust storage unit is used. • Optimizing the storage system capacity at the highest renewable fraction. • In conjunction, fuel cells with photovoltaics can improve energy self-consumption and self-sufficiency. • Shared photovoltaic energy generation with fuel cell energy can add customer value to the improvement of the grid. • The levelized cost of energy was calculated to be about $0.23/kWh for the proposed system.

A Study of Multi-Pass Laser-Cladding 2205 Duplex Stainless Steel Coating: Microstructure, Electrochemical Corrosion Behavior, and Wear-Resistance Properties

By applying 2205 duplex stainless steel powders to repair and improve carbon steel, multi-pass laser-cladding tests were conducted on Q235 carbon steel surfaces with different laser powers in the range of 1.9~2.5 kW in order to evaluate the performance of the laser-cladding layers. The phase composition, macro- and microstructure, electrochemical corrosion resistance, friction, and wear resistance of the laser-cladding layers were investigated. Macroscopic observation identified no obvious cracks. The phases that made up the multi-pass laser-cladding layers were γ-Fe and α-Fe. Owing to the optimal laser power at 2.3 kW, a large number of equiaxed crystals and a small number of cellular crystals made up the microstructure of the prepared laser-cladding layer, which contributed to its good corrosion resistance. The wear resistance of the multi-pass laser-cladding layer and the carbon steel was also studied. A combined action of adhesive wear and abrasive wear, accompanied by oxidative wear, was determined through observation of pits and furrows on the friction surface of the multi-pass laser-cladding layer, while a typical mechanism of abrasive wear was confirmed by checking the friction surface of the carbon steel.

Diagnostics of RF coupling in H- ion sources as a tool for optimizing source design and operational parameters.

Radio frequency (RF) driven H- ion sources are operated at very high power levels of up 100 kW in order to achieve the desired performance. For the experimental setup, these are demanding conditions possibly limiting the source reliability. Therefore, assessing the optimization potential in terms of RF power losses and the RF power transfer efficiency η to the plasma has moved to the focus of both experimental and numerical modeling investigations at particle accelerator and neutral beam heating sources for fusion plasmas. It has been demonstrated that, e.g., at typical neutral beam injection ion source setups, about half of the RF power provided by the generator is lost in the RF coil and the Faraday shield due to Joule heating or via eddy currents. In a best practice approach, it is exemplarily demonstrated at the ITER RF prototype ion source how experimental evaluation accompanied by numerical modeling of the ion source can be used to improve η. Individual optimization measures regarding the Faraday shield, the RF coil, the discharge geometry, the RF driving frequency, and the application of ferrites are discussed, which could reduce the losses by a factor of two. The provided examples are intended as exemplary guidelines, which can be applied at other setups in order to achieve with low-risk effort an optimized ion source design in terms of reduced losses and hence increased reliability.

Investigative study of the radiation damage on fuel clad of miniature neutron source reactor using computational tools

Core conversion requires some evaluation of the reactor safety. Changes to the reactivity worth, shutdown margin, power density and material properties are crucial to the proper functioning of the reactor. The focus of this article is to study the neutron flux distribution in the reactor core and radiation damage on candidate clads. The Ghana Research Reactor-1 (GHARR-1) operates at maximum power of 30 kW in order to attain a flux of 1.0× 1012 n·cm–2·s for the high enriched uranium core. Using the GHARR-1 core geometry, considering 348 fuel pins, the multiplication factor (Keff) is calculated at enrichments of 10%, 12.5%, 16%, 20%, 30% and 90.2%. The spectrum of neutron flux generated in the 26 group is also calculated at the specified enrichments. The ion/particle interactions with the targets (clad) were studied in the Stopping and Range of Ion in Matter code to establish the best clad material based on recorded defects and vacancies generated. From the calculations and simulations, the best choice from the candidate clads based on the assessment is SiC. The calculation of the fuel campaign length gives 7.5 years. The defects sustained by the prospective clad showed low susceptibility to swelling and other forms of deformation.

AC Loss Effect of High-Order Harmonic Currents in a Single-Phase 6.5 MVA HTS Traction Transformer

Traction transformer is one of the critical electrical devices in high-speed trains. To increase transformer efficiency up to 99% and reduce weight and fire risks, we are currently building a 6.5 MVA superconducting traction transformer. Assuming 15 as a realistic cooling penalty, thermal loss from the transformer windings cannot exceed 4 kW in order to meet 99% of efficiency. There are non-ignorable high frequency harmonics in the traction side of the transformer, so it is important to investigate the effect of harmonic current on ac loss in transformer windings. We explored the dependency of ac loss in transformer on the amount of the 13th harmonic in traction side, by means of numerical calculation in a 2-D axisymmetric model using the H formulation. Simulations were also carried out to study the influence of the phase state of the 13th harmonic, either in phase or out of phase compared to the fundamental current, and multiple harmonics together in traction winding. Results show that the 13th harmonic must be limited under 1.5% of the rated current to fulfill the aim of 99% efficiency. AC loss in transformer increases when maximum amplitude of distorted currents carrying the same order in-phase harmonic but different amount increases. With various harmonic components in the LV winding, it is important to consider both the maximum current and waveforms to have a clear idea of loss behavior in the transformer.

Stochastic energy investment in off‐grid renewable energy hub for autonomous building

This study forms and optimises the renewable energy hub to supply load demand in the autonomous building disconnected from electrical grid (i.e. net-zero energy building). The proposed energy hub is made of hybrid wind-solar-hydro generation systems and it is also strengthened by pumped-storage hydroelectricity and hydrogen storage systems. The hydro system includes two water reservoirs in cascade connection and one pumped-storage hydroelectricity. The introduced optimisation programming designs proper capacity for cascade water reservoirs and energy storage system as well as optimises their operation. The uncertainties of parameters are included to make the stochastic programming. It is demonstrated that increasing the flow-in of reservoir 1 by 25% decreases the planning cost by ∼2.5% and decreasing the flow-in of reservoir 2 by 50% increases the planning cost by ∼16%. When the hydro system does not operate, the wind power must be increased to 10 kW in order to supply the load. When the wind and solar powers are not integrated, the hydro energy must be increased by 50%.

Performance Analysis and Optimization of an Organic Rankine Cycle Coupled to a Fresnel Linear Concentrator for Various Working Fluids

The aim of this study is to model, optimize and analyze the performance of a micro power solar of 3 kW in order to meet the priority needs of Mauritania rural people in electric power and contribute to the reduction of greenhouse gases. The proposed system is composed of a Fresnellinear concentrator which is coupled to an Organic Rankine cycle with a regenerator. Several working fluids (R134a, R152a, R290 and R717) were used for better optimizing the system. Thus, many thermodynamic and physical parameters which are influent on the performance of the overall system were analyzed. This analysis shows that the R152a and R134a fluids are the best candidates for the applications of ORC solar at low temperatures. Indeed, a 5°C superheating, the overall system efficiency, the energy and exergy efficiency of the ORC cycle has been respectively improved to 7.7%, 16.1% and 14.4%. The Optimization made on the overall system allowed a 26% and 12% reduction of the surface of the concentrator and the volume flow out of the micro-turbine respectively. The minimum surface and volumetric flow rate required to produce 3 kW is respectively 21.25 m² and 21.421 m³/h, this last result is achieved from the operating conditions: working fluid R152a, evaporation temperature which is 90°C and the direct normal radiation 1800 W/m².

Dynamic Simulation of a Reactive Distillation Process for n-Butyl Acetate Production Using CHEMCAD

The dynamic simulation of a reactive distillation process developed with the aid of CHEMCAD for the production of n-butyl acetate has been carried out in this research work. Originally, the by-product of the process was water. The developed model of the system was first simulated for steady state using a reflux ratio of 3 and a reboiler duty of 1.4 kW in order to have initial values for the mole fractions of the components involved. The model was converted to a dynamic type by activating the “Dynamics” in the “Convergence” tab of the “Run” menu of CHEMCAD. The dynamic model of the system was run using different (positive and negative) step changes applied to the input variables, which were reflux ratio and reboiler duty, of the process. The results obtained from the steady-state simulation showed that only n-butyl acetate and unconverted acetic acid were existing in the reboiler section of the column initially. The dynamic simulation of the process showed that the system was a stable one because it could get settled after some running time of its dynamic model for all the step changes in the two input variables considered. It was also discovered from the simulations carried out that the dynamic responses of the system to negative step changes in reflux ratio were smoother than those obtained when positive step changes were applied to the same input variable. Moreover, the applications of negative step changes to the reboiler duty resulted in decreases in the mole fractions of n-butyl acetate present in the bottom section of the column while the applications of positive changes to the same reboiler duty gave rise to increases in the mole fraction values of the desired product that was collected through the reboiler section of the column. It was discovered from the results obtained that the higher the reboiler duty of the system that was applied in the production of n-butyl acetate from the esterification reaction involving acetic acid and n-butanol, the faster the system was approaching its dynamic steady state.

Customised application of exergy analysis method to PW120A turboprop engine for performance evaluation

In this paper, first and second laws of thermodynamics are applied on a turboprop engine of a regional aircraft. Performance parameters of the engine are assessed under take-off conditions and maximum power settings. Energy and exergy rates, exergy destruction rate, improvement potential, fuel depletion rate and productivity rate are proven by using component-based analysis method. Exergy destruction rates are found to be 337.12 kW, 1461.87 kW, 69.74 kW and 269.22 kW in order of air compressor, combustion chamber, gas turbine and free turbine. In addition, exergy efficiencies of the air compressor, combustion chamber, gas turbine and free turbine are calculated to be 86.95%, 82.16%, 97.86% and 85.52%, respectively, whilst energy and exergy efficiencies of the engine are found to be with the values of 27.89% and 26.74%. Obtained results from this study can be useful to improve performance of a turboprop engine still in service.

Detection and Diagnosis of Faults in Induction Motor Using an Improved Artificial Ant Clustering Technique

The presence of electrical and mechanical faults in the induction motors (IMs) can be detected by analysis of the stator current spectrum. However, when an IM is fed by a frequency converter, the spectral analysis of stator current signal becomes difficult. For this reason, the monitoring must depend on multiple signatures in order to reduce the effect of harmonic disturbance on the motor-phase current. The aim of this paper is the description of a new approach for fault detection and diagnosis of IMs using signal-based method. It is based on signal processing and an unsupervised classification technique called the artificial ant clustering. The proposed approach is tested on a squirrel-cage IM of 5.5 kW in order to detect broken rotor bars and bearing failure at different load levels. The experimental results prove the efficiency of our approach compared with supervised classification methods in condition monitoring of electrical machines.

Fusion for Space Propulsion

The possible role of a controlled thermonuclear reactor in space missions is discussed. Although such a reactor is many years from reality, some of its properties are understood well enough to indicate problems which will appear and which are peculiar to space flight. It appears that it will have to deliver electric power or thrust at a weight of about one pound per kw in order to represent significant improvement over other systems, notably the fission-electric one. One attractive feature of a fusion reactor, as now envisioned, is that it may lend itself to the direct production of electricity or even thrust, without an intermediate heat cycle. It is essential to avoid such a cycle if the weight is to be kept low.