Load Shape Research Articles

Common Noctule Bats Are Sexually Dimorphic in Migratory Behaviour and Body Size but Not Wing Shape.

Within the large order of bats, sexual size dimorphism measured by forearm length and body mass is often female-biased. Several studies have explained this through the effects on load carrying during pregnancy, intrasexual competition, as well as the fecundity and thermoregulation advantages of increased female body size. We hypothesized that wing shape should differ along with size and be under variable selection pressure in a species where there are large differences in flight behaviour. We tested whether load carrying, sex differential migration, or reproductive advantages of large females affect size and wing shape dimorphism in the common noctule (Nyctalus noctula), in which females are typically larger than males and only females migrate long distances each year. We tested for univariate and multivariate size and shape dimorphism using data sets derived from wing photos and biometric data collected during pre-migratory spring captures in Switzerland. Females had forearms that are on average 1% longer than males and are 1% heavier than males after emerging from hibernation, but we found no sex differences in other size, shape, or other functional characters in any wing parameters during this pre-migratory period. Female-biased size dimorphism without wing shape differences indicates that reproductive advantages of big mothers are most likely responsible for sexual dimorphism in this species, not load compensation or shape differences favouring aerodynamic efficiency during pregnancy or migration. Despite large behavioural and ecological sex differences, morphology associated with a specialized feeding niche may limit potential dimorphism in narrow-winged bats such as common noctules and the dramatic differences in migratory behaviour may then be accomplished through plasticity in wing kinematics.

Dynamic failure of dry and fully saturated limestone samples based on incubation time concept

This paper outlines the results of experimental study of the dynamic rock failure based on the comparison of dry and saturated limestone samples obtained during the dynamic compression and split tests. The tests were performed using the Kolsky method and its modifications for dynamic splitting. The mechanical data (e.g. strength, time and energy characteristics) of this material at high strain rates are obtained. It is shown that these characteristics are sensitive to the strain rate. A unified interpretation of these rate effects, based on the structural–temporal approach, is hereby presented. It is demonstrated that the temporal dependence of the dynamic compressive and split tensile strengths of dry and saturated limestone samples can be predicted by the incubation time criterion. Previously discovered possibilities to optimize (minimize) the energy input for the failure process is discussed in connection with industrial rock failure processes. It is shown that the optimal energy input value associated with critical load, which is required to initialize failure in the rock media, strongly depends on the incubation time and the impact duration. The optimal load shapes, which minimize the momentum for a single failure impact, are demonstrated. Through this investigation, a possible approach to reduce the specific energy required for rock cutting by means of high-frequency vibrations is also discussed.

A multi-objective hybrid GA and TOPSIS approach for sizing and siting of DG and RTU in smart distribution grids

Installing remote terminal units (RTUs) in smart distribution grids enables the distribution system operator (DSO) and end-side customers to properly execute demand response programs (DRPs). Direct load control (DLC) refers to an incentive-based DRP, in which, DSO contracts with customers to control a specific percentage of their consumptions. In initial stages, the limited budget and technical hurdles avert the widespread deployment of RTUs in all buses. This issue instigates the need for an optimal placement of RTUs. Moreover, the existence of RTUs definitely affects the load shape of the network. Thus, the optimal placement strategy for distributed generations (DGs) should be revisited. To involve these issues together, an optimal two-stage multi-objective procedure is proposed which takes into account the simultaneous placement of DGs and RTUs. Different scenarios including variations in the number of DG units, DGs’ adaptive power factor (APF) for reactive power processes, and individual or simultaneous placement of DGs and RTUs are established and interrogated in depth. In numerical validations, both of the power losses minimization and voltage profile improvement are explored based on an AC power flow fashion optimized with genetic algorithm (GA). The extracted results are then transferred to the second stage which applies a multi-attribute decision making approach based on technique for order preference by similarity to ideal solution (TOPSIS). This stage considers the importance degrees or so-called weights for both of the objectives. In this way, the worth of each objective is suitably determined and involved in decision making process. Thus, the optimal placement strategy for simultaneous allocation of DGs and RTUs is determined.

Quantifying electric vehicle battery degradation from driving vs. vehicle-to-grid services

Abstract The risk of accelerated electric vehicle battery degradation is commonly cited as a concern inhibiting the implementation of vehicle-to-grid (V2G) technology. However, little quantitative evidence exists in prior literature to refute or substantiate these concerns for different grid services that vehicles may offer. In this paper, a methodology is proposed to quantify electric vehicle (EV) battery degradation from driving only vs. driving and several vehicle-grid services, based on a semi-empirical lithium-ion battery capacity fade model. A detailed EV battery pack thermal model and EV powertrain model are utilized to capture the time-varying battery temperature and working parameters including current, internal resistance and state-of-charge (SOC), while an EV is driving and offering various grid services. We use the proposed method to simulate the battery degradation impacts from multiple vehicle-grid services including peak load shaving, frequency regulation and net load shaping. The degradation impact of these grid services is compared against baseline cases for driving and uncontrolled charging only, for several different cases of vehicle itineraries, driving distances, and climate conditions. Over the lifetime of a vehicle, our results show that battery wear is indeed increased when vehicles offer V2G grid services. However, the increased wear from V2G is inconsequential compared with naturally occurring battery wear (i.e. from driving and calendar ageing) when V2G services are offered only on days of the greatest grid need (20 days/year in our study). In the case of frequency regulation and peak load shaving V2G grid services offered 2 hours each day, battery wear remains minimal even if this grid service is offered every day over the vehicle lifetime. Our results suggest that an attractive tradeoff exists where vehicles can offer grid services on the highest value days for the grid with minimal impact on vehicle battery life.

Predictive control of residential HVAC and its impact on the grid. Part II: simulation studies of residential HVAC as a supply following resource

This paper introduces a methodology, using model predictive control, for shaping the electric demand of residential distribution feeder. The methods are designed to result in a paradigm shift from generation that follows load to load that follows supply. First, a reference demand curve, obtained from “smoothing” a base case demand profile, is proposed. Then, in order to better match the availability of renewable energy resources, the reference demand curve is modified to consider residential rooftop photovoltaic systems and utility scale wind generation. A simulation framework introduced in a companion paper is employed. Simulation results suggest that the active load shaping methodology is very effective at providing demand flexibility at time scales shorter than two or three hours. At longer time scales, flexibility is limited by the thermal storage effectiveness of the residential building envelope, and to a large extent, the amount of load being shifted relative to total active cooling demand.

Estimating Power Generation of Invisible Solar Sites Using Publicly Available Data

Large-scale integration of invisible solar photovoltaic generation into power systems could significantly affect the system net load and pose new challenges in the operation of power systems. Invisible solar photovoltaic refers mainly to small-scale roof-top solar sites that are not monitored, and thus are invisible to utilities and system operators. Invisible solar generation affects the shape of system net electrical load and could make net load forecasting more challenging. In this paper, a methodology is proposed to estimate the power generation of invisible solar photovoltaic sites. The proposed method only uses the measured power generation data of publicly available sites. It uses real time data of a small subset of sites to estimate the aggregated power generation from known sites within a region. The proposed model is validated using actual invisible solar generation data of the California power system.

Blast characterization using a ballistic pendulum with a centrally mounted Hopkinson bar

A series of laboratory-scale blast characterization experiments are presented to show the degree to which two alternative configurations of an instrumented ballistic pendulum can provide an ideal impulsive load. Both the total impulses and blast pressure histories were captured, the latter using a centrally mounted Hopkinson bar. Repeatable and consistent total impulse values were achieved, while the Hopkinson bar technique was sufficient to capture the essential shape of the blast loads, although the fine detail of the peak pressure could not be resolved due to higher mode dispersion. A short stand-off configuration produced short duration blast loads that approached an ideal impulsive load condition with near uniform impulse distributions, although the blast pressure distributions were non-uniform. Conversely, a blast tube configuration produced blast loads with near uniform pressure and impulse distributions but did not approach an ideal impulsive load condition, that is, the pressure history must be accounted for in subsequent analytical work.

Analyzing Big Smart Metering Data Towards Differentiated User Services: A Sublinear Approach

With the advances of the information and communications technology, and smart meters in particular, fine grained user electricity usage of households is available for analyzing electricity usage behaviors. The information makes it possible for utility companies to provide differentiated user services from the time-of-use perspective, i.e., different pricing for users based upon when and how users consume power. In this paper, we present a methodology on differentiated user services based on extracted characteristic consumer load shapes (usage profiles as a function of time) from a large smart meter data set. We identify distinct user subgroups based upon their actual historic usage patterns, which are represented by the proposed electricity usage distributions. Since the big electricity user data cover millions of users and for each user the data are multi-dimensional and in fine-time granularity, we thus propose a sublinear algorithm to make the computation of the differentiated user service model efficient. The algorithm requests an input of only a small portion of users, and a sublinear amount of the electricity data from each of these selected users. We prove that the algorithm provides performance guarantees. Our simulated evaluation demonstrates the effectiveness of our algorithm and the differentiating user service model.

Multiphase Numerical Study of Ice Accretion on Circular Cylinders in Duplex Configuration

Numerical study of atmospheric ice accretion on circular cylinders in duplex configuration has been carried out at different operating and geometric conditions. Analyses showed a difference in ice accretion on both cylinders, as streamline accumulated ice shapes were observed along front cylinder and irregular ice shapes were found along rear cylinder. Results also showed a change in accreted ice load and ice shape along rear cylinder with the change in distance between both cylinders. Parametric study at different droplet sizes and temperatures showed a variation in ice accretion. This prelimenary research work provides a useful base for better understanding and further investigation of atmospheric ice accretion on circular overhead conductors in duplex configuration, installed in cold climate of high north regions.

Effects of facing, reinforcement stiffness, toe resistance, and height on reinforced walls

This study numerically investigated the combined effect of reinforcement and facing stiffness, wall height, and toe resistance on the behavior of reinforced soil (RS) walls under working stress conditions. For RS walls with vertical segmental block facing, parametric analyses showed that the combined effect of the facing stiffness, wall height, and toe resistance on the distribution of the maximum reinforcement load with depth may be limited to approximately 4 m above the base of the wall. Furthermore, the shape of the distribution of the reinforcement load may be a function of the combined effect of the wall height, reinforcement stiffness, toe resistance, and facing stiffness. For a given facing stiffness and fixed-base conditions, increasing the height of the wall and reinforcement stiffness may change the distribution shape of the reinforcement load from trapezoidal to the triangular. Additionally, the maximum reinforcement loads calculated using finite element analyses were compared to the values predicted by design methods found in the literature. Some limitations of those design procedures are presented and discussed.

Long-term deconditioning of gas-filled surge arresters

ABSTRACTThe aim of this paper is to identify parameters that influence the long-term deconditioning effect of gas-filled surge arrester (GFSA) and to provide practical recommendations for mitigating this effect. Namely, after some period of time, on order of hours or days, during which there is no activation due to overvoltage, the deconditioning of GFSA occurs. This effect was observed experimentally within the paper. The observed parameters that could influence the long-term deconditioning effect were the following: shape of voltage load, gas type, gas pressure, interelectrode distance, electrode material, electrode surface topography as well as GFSA design such as two- or three-electrode configuration. According to the results obtained, it has been shown that the occurrence of long-term deconditioning in an insulating system, insulated by a noble gas at a subpressure and with small interelectrode distances, is a phenomenon that always occurs when the insulating system is at rest for about an hour. It has been found that the type of noble gas does not influence the long-term deconditioning. Analysis of such insulating systems' parameters, with a prospect of being used as GFSAs, has demonstrated that this phenomenon is less pronounced at higher pressures (for the same value of the pressure (p) and interelectrode distance (d) product) and for electrodes with microscopically embossed surfaces. According to the results that were obtained by noble gases and their mixtures, as well as the results that were obtained by mixtures of SF6 gas with noble gasses, it can be claimed with confidence that the effect of the long-term deconditioning is an electrode effect. It has also been established that the deconditioning effect does not depend on the electrode material except in the case of electrodes made out of noble metals, which reduce the effect. Based on these results, it can be recommended that the working point of GFSAs be set (according to the DC breakdown voltage value) at a pressure that is as high as possible (with pd = const), and that the electrode active surface should have a marked microscopic topography. In addition to this, an essential conclusion for GFSA manufacturers is that long-term system deconditioning is caused by impurities and adsorbed gases that appear at electrode during the state of rest. Out of these two causes, the influence of impurities is probably the dominant one, which is proved by considerably reduced long-term deconditioning in the case of noble metal electrodes, not susceptible to corrosion. This has also been confirmed by a less distinct effect of long-term deconditioning in the case of sandblasted electrodes that have a stronger tendency towards gas adsorption and a weaker tendency towards corrosion. However, it has been shown that adding of the third electrode (that is concentric to the main electrode system) on a free floating potential along with usage of sandblasted electrodes and with smaller interelectrode distance significantly reduces the effects of the long-term deconditioning.

Day-ahead economic optimization of energy use in an olive mill

This article presents an economic case study on biomass and power dispatch focused on the olive oil extraction industry. A method is proposed to minimize the energy cost associated to olive oil production. This is realized through load shaping and optimal selection of the destination of subproducts and wastes. The mill and the loads linked to the extraction process are modeled using the energy hub concept, and an Economic Model Predictive Control (EMPC) based power and biomass dispatcher is introduced. The control strategy has been simulated over different scenarios to validate the optimization scheme.

Active demand response with electric heating systems: Impact of market penetration

Active demand response (ADR) is a powerful instrument among electric demand side management strategies to influence the customers’ load shape. Assessing the real potential of ADR programmes in improving the performance of the electric power system is a complex task, due to the strict interaction between supply and demand for electricity, which requires integrated modelling tools. In this paper an analysis is performed aimed at evaluating the benefits of ADR programmes in terms of electricity consumption and operational costs, both from the final user’s and the overall system’s perspective. The demand side technologies considered are electric heating systems (i.e. heat pumps and electric resistance heaters) coupled with thermal energy storage (i.e. the thermal mass of the building envelope and the domestic hot water tank). In particular, the effect of the penetration rate of ADR programmes among consumers with electric heating systems is studied. Results clearly show that increasing the number of participating consumers increases the flexibility of the system and, therefore, reduces the overall operational costs. On the other hand, the benefit per individual participant decreases in the presence of more ADR-adherent consumers since a reduced effort from each consumer is needed. Total cost saving ranges at most between about 400€ and 200€ per participant per year for a 5% and 100% ADR penetration rate respectively.

Achieving very high PV penetration – The need for an effective electricity remuneration framework and a central role for grid operators

This article proposes that optimally deployed solutions to the intermittency introduced by high penetration solar – e. g., electrical storage, optimized curtailment and demand response – could affordably transform solar power generation into the firm power delivery system modern energy economies require, thereby enabling very high solar penetration and the displacement of conventional power generation. The optimal deployment of these high-penetration-enabling solutions imply the existence of a healthy power grid, and therefore imply a central role for utilities and grid operators.This article also proposes that a value-based electricity compensation mechanism (based on e.g., Value of Solar (VOS) and load shaping tariffs), recognizing the multi-facetted, penetration-dependent value and cost of solar energy, and capable of shaping consumption patterns to optimally match resource and demand, could be an effective vehicle to enable high solar penetration and deliver affordable firm power generation.

Laser-generated shock wave attenuation aimed at microscale pyrotechnic device design

To meet the rising demand for miniaturizing the pyrotechnic device that consists of donor/acceptor pair separated by a bulkhead or a thin gap, the shock initiation sensitivity in the microscale gap test configuration is investigated. For understanding the shock attenuation within a gap sample (304 stainless steel) thickness of 10∼800 μm, the laser-generated shock wave in water confinement is adopted. The shock properties are obtained from the free surface velocity by making use of a velocity interferometer system for any reflector (VISAR). Analytical models for plasma generation in a confined geometry and for evolution and decay of shock waves during the propagation are considered. The shape and amplitude of the laser-driven initial pressure load and its attenuation pattern in the gap are effectively controlled for targeting the microscale propagation distance and subsequent triggering pressure for the acceptor charge. The reported results are important in the precise controlling of the shock strength during the laser initiation of microscale pyrotechnic devices.

Finite element analysis and die design of heading processes of magnesium alloy screws

This study is to develop related manufacturing technologies of LZ91 magnesium alloy M6 screws. Firstly, a warm heading process composed of three stages is proposed. The material flow pattern of the billet inside the die is analyzed using the finite element analyses. The effects of the friction factor, die speed and forming temperature on the heading load are discussed. The effects of the stroke at the first stage on the formability at the second stage are also discussed. Finally, warm heading experiments are conducted using a self-designed die set and a lubricant of MoS2. The experimental values of heading load and product shapes and dimensions are compared with the simulation results to verify the validity of the finite element models and the proposed warm heading procedures.

Giants of the Sky.

The article focuses on research into pelagornithid species of birds and how the species were able to fly while being larger than modern avians. It comments on paleontologist Edouard Lartet's discovery in 1857 of the first pelagornithid, dubbed Pelagornis (P.) micaenus, which had a humerus that measured nearly two feet long. It mentions the discovery of P. sandersi in 2014 with a humerus three feet in length and talks about the bird's aspect ratio, wing load, and wing shape like an albatross.

A fuzzy clustering approach to a demand response model

This paper proposes a novel demand response model using a fuzzy subtractive cluster approach. The model development provides support to domestic consumer decisions on controllable loads management, considering consumers’ consumption needs and the appropriate load shape or rescheduling in order to achieve possible economic benefits. The model based on fuzzy subtractive clustering method considers clusters of domestic consumption covering an adequate consumption range. Analysis of different scenarios is presented considering available electric power and electric energy prices. Simulation results are presented and conclusions of the proposed demand response model are discussed.

3D modelling of tyre-pavement contact pressure

Pavement design assumes uniform contact loading because of bottom-up traditional cracking (far from loading), but nowadays more and more surface damage (top-down cracking and rut) due to new technology in pavement and tyre design is observed. Then, a more realistic tyre–pavement contact modelling has to be considered. In order to go towards more realistic tyre–pavement contact, finite element method consumes a lot of calculation time; so in this article, we propose a semi-analytical model developed for the calculation of ball bearings. The contact is considered as a Hertzian contact, and the surface of the road is flat and that the tyre is smooth. Calculation of contact pressure is compared and validated with experimental data using a device called Stress-In-Motion, which allows contact pressure measurement. Different parameters are assumed in the modelling such as tyre pressure, axle loading and tyre shape. We have now a successful tool to analyse the tyre–pavement contact, more accurate and realistic and especially faster than those used at the moment.

Subspace Frequency Analysis--Based Field Indices Extraction for Electricity Customer Classification

In electricity customer classification, the most important task is to avoid the curse of dimensionality problem, as the consumption diagrams have a large number of dimensions. To avoid the curse of dimensionality problem, field indices (load shape factor) are often used instead of consumption diagrams. Field indices are directly extracted from consumption diagrams according to a predefined formula. Previous studies show that the most important thing for defining such a formula is to find meaningful time intervals from consumption diagrams. However, the inconvenient thing is that there are still a lack of details to explain how to define such time intervals. In our study, we propose a data mining--based method named SFATIE to support the extraction of field indices. The performance of the proposed method is evaluated by comparing it with other dimensionality reduction methods during the classification. For the classification, most often we have used classification methods like C5.0, SVM, Neural Net, Bayes Net, and Logistic. The experimental results show that our method is better or close to other dimensionality reduction methods. In addition, the experimental results show that our proposed method can produce the good quality of field indices and that these indices can improve the performance of electricity customer classification.