Nowadays, the importance of the coordinated operation of power system assets has caused severe challenges that can be addressed through some recently emerged concepts, such as microgrids (MGs) and ...virtual power plants (VPPs). In this paper, a hierarchical model is proposed for simultaneous modeling of an MG scheduling and VPP energy management problems. Given the stochastic nature of the scheduling inputs, power production and also, load demand uncertainties are modeled using a scenario-based method. Therefore, the final model is presented as a stochastic mixed-integer linear programming (MILP) model. It is possible to cover the fluctuations at the minimum cost using demand response (DR) programs and electric vehicles (EVs). In addition, the possibility of power transaction between the adjacent MGs is analyzed in scheduling model, preventing unreal power exchanges. The simulation results indicate that the coordinated operation of MGs can improve load restoration, and reduce the load supply costs in each MG. It is also observed that the profit of the VPP would be higher in the case with the time-of-use (TOU) tariff compared to the cases with the real-time pricing (RTP) and critical peak pricing (CPP) mechanisms.
•Developing a stochastic model for the joint planning and operation of energy hub.•Dividing the solution space into two stages to increase the solution speed.•Tackling the problem by using continuous ...and discrete methods.•Reducing planning cost by employing RCGA.•Investigating the effect of continuous and discrete methods on the hub planning.•Assessing the impacts of various DR and IDR programs on the hub planning.
Energy hub systems improve energy efficiency and reduce emissions due to the coordinated operation of different infrastructures. Given that these systems meet the needs of customers for different energies, their optimal design and operation is one of the main challenges in the field of energy supply. Hence, this paper presents a two-stage stochastic model for the integrated design and operation of an energy hub in the presence of electrical and thermal energy storage systems. As the electrical, heating, and cooling loads, besides the wind turbine’s (WT’s) output power, are associated with severe uncertainties, their impacts are addressed in the proposed model. Besides, demand response (DR) and integrated demand response (IDR) programs have been incorporated in the model. Furthermore, the real-coded genetic algorithm (RCGA), and binary-coded genetic algorithm (BCGA) are deployed to tackle the problem through continuous and discrete methods, respectively. The simulation results show that considering the uncertainties leads to the installation of larger capacities for assets and thus a 8.07% increase in investment cost. The results also indicate that the implementation of shiftable IDR program modifies the demand curve of electrical, cooling and heating loads, thereby reducing operating cost by 15.1%. Finally, the results substantiate that storage systems with discharge during peak hours not only increase system flexibility but also reduce operating cost.
Data from a small air shower array were used to examine the cosmic ray shadow of the Moon at energies more than 100
TeV. A simple technique has been used for the analysis of this data. In this ...technique the number of EAS events with arrival directions falling in error circles centered about the moving moon is compared to the mean number of events falling in error circles with centers randomly chosen in the sky. For any assumed angular radius of the error circle the deficit in EAS event count in the direction of moon which is a moon-related effect is interpreted as the shadow of the moon. A simple theoretical model has been developed to relate the mean number of EAS events,
N
sky
, to the angular radius of the error circle and has been applied to the counts from the moon’s direction in order to extract the physical parameters of the shadow of the moon. The technique and the theoretical model has been used on
1.7
×
10
5
EAS events recorded by a small air shower array.
A large portion of electricity demand in the world is delivered by microgrids (MGs). Operation of MGs under the uncertainty of demands and renewable power is a hot research area. As per the ...literature, in operation of MGs under uncertainty, the coordinated operation of MGs, with consideration of both day-ahead (DA) and real-time (RT) stages has not been investigated in details. In this paper, the operation of an MG with dispatchable generators and wind turbine has been formulated as a two-stage stochastic optimisation problem, wherein DA and RT stages are seen in one shot and DA and RT decision variables are determined in a way that the expected MG operation cost is minimised. In this research, the flexibility resources including fast responsive demands and fast-start distributed generators are used to increase the flexibility of MG and decrease its operation cost. The effect of the flexibility resources on MG operation has been investigated. Fast responsive demands accept scenario-dependent schedule, but slow responsive demands do not. Slow-start generators cannot be started up in any RT scenario, if they are OFF at DA stage, but fast-start generators can.
•Two-stage stochastic optimisation has been used for scheduling microgrids.•Both day-ahead and real-time stages are seen in a single shot.•Fast responsive demands and fast-start generators are used as flexibility resources.•The effect of flexibility resources on MG operation has been investigated.•The uncertainties of demands and wind power have been considered.
A new small array of Cherenkov detectors has been deployed in Tehran, 1200 m above sea level. This array contains four tanks of distilled water with a diameter of 64 cm and a height of 130 cm. The ...effective area of each tank is about 1382 cm2. They are used to detect air showers and to record the arrival time of the secondary particles. We have collected about 640 000 extensive air showers (EAS) in 8298 h of observation time from November 2006 to October 2007. The distribution of air showers in zenith and azimuth angles has been studied and a cosntheta distribution with n = 6.02 +/- 0.01 was obtained for the zenith angle distribution. An asymmetry has been observed in the azimuthal distribution of EAS of cosmic rays due to geomagnetic field. The first and second amplitudes of the asymmetry are AI = 0.183 +/- 0.001 and AII = 0.038 +/- 0.001. Since the recent results are in good agreement with our previous results of scintillation detectors, and tanks of distilled water are cheaper, we prefer to use them instead of scintillators in a future larger array. By simulation, we have improved the size of the detectors to yield the highest efficiency. The best dimensions for each tank with a photomultiplier tube in the center of its lid are 40 cm in diameter and 60 cm in height.
•Providing a multi-objective optimization framework for determining the optimal topology.•Analyzing the effect of objective functions on the operating costs, losses and reliability.•Considering ...different uncertainties to make the simulation conditions more realistically.•Analyzing the effect of the DR program on the system LMP and the load demand curve.
In this paper, a multi-objective optimization framework is proposed to solve the distribution feeder reconfiguration (DFR) problem and its operation considering the demand response (DR) program, renewable energy sources (RES's), and electrical energy storages (EES's). The proposed model is implemented on 33-bus and 118-bus radial distribution systems while the uncertainties of RES's output power, load demand and electricity price are taken into account. The Monte Carlo simulation approach is used to generate scenarios while the backward scenario reduction approach is used to reduce the number of scenarios. The studied problem is modeled using the Epsilon-constrained method as a two objective problem and it is solved in the form of five case studies using the GUROBI solver in GAMS software. Our analysis of the results shows that reducing losses and increasing system reliability increases the production of local generation units, thereby increasing the operating costs. In addition, simulation results demonstrate that considering the dynamic topology reduced losses by 9.73% and increased reliability by 4.7%. The results also show that using the DR program reduces LMP by about 20% during peak hour.
Gamma-ray line signatures can be expected in the very-high-energy (E(γ)>100 GeV) domain due to self-annihilation or decay of dark matter (DM) particles in space. Such a signal would be readily ...distinguishable from astrophysical γ-ray sources that in most cases produce continuous spectra that span over several orders of magnitude in energy. Using data collected with the H.E.S.S. γ-ray instrument, upper limits on linelike emission are obtained in the energy range between ∼ 500 GeV and ∼ 25 TeV for the central part of the Milky Way halo and for extragalactic observations, complementing recent limits obtained with the Fermi-LAT instrument at lower energies. No statistically significant signal could be found. For monochromatic γ-ray line emission, flux limits of (2 × 10(-7) -2 × 10(-5)) m(-2) s(-1) sr(-1) and (1 × 10(-8) -2 × 10(-6)) m(-2) s(-1)sr(-1) are obtained for the central part of the Milky Way halo and extragalactic observations, respectively. For a DM particle mass of 1 TeV, limits on the velocity-averaged DM annihilation cross section ⟨σv⟩(χχ → γγ) reach ∼ 10(-27) cm(3)s(-1), based on the Einasto parametrization of the Galactic DM halo density profile.
An experiment has been developed for the measurement of the muon charge ratio (ratio of positive to negative muons) in the cosmic ray flux in energy range 0.236–0.242
GeV. The muon charge ratio is ...found to be 1.35
±
0.10 with a mean zenith angle of 32°
±
5°. Meanwhile, the distributions of muons in zenith (
θ) and azimuth angles have been studied. A
cos
n
θ
distribution with
n
=
1.95
±
0.13 has been obtained. An asymmetry has been observed in East–West directions because of geomagnetic field.
We report on deep observations of the extended TeV gamma-ray source MGRO J1908+06 made with the VERITAS very high energy gamma-ray observatory. Previously, the TeV emission has been attributed to the ...pulsar wind nebula (PWN) of the Fermi-LAT pulsar PSR J1907+0602. We detect MGRO J1908+06 at a significance level of 14 standard deviations (14sigma) and measure a photon index of 2.20 + or - 0.10 sub(stat) + or - 0.20 sub(sys). The TeV emission is extended, covering the region near PSR J1907+0602 and also extending toward SNR G40.5-0.5. When fitted with a two-dimensional Gaussian, the intrinsic extension has a standard deviation of sigma sub(src) = 0.degrees44 + or - 0.degrees02. In contrast to other TeV PWNe of similar age in which the TeV spectrum softens with distance from the pulsar, the TeV spectrum measured near the pulsar location is consistent with that measured at a position near the rim of G40.5-0.5, 0.degrees33 away.
We summarize broadband observations of the TeV-emitting blazar 1ES 1959+650, including optical R-band observations by the robotic telescopes Super-LOTIS and iTelescope, UV observations by Swift ...Ultraviolet and Optical Telescope, X-ray observations by the Swift X-ray Telescope, high-energy gamma-ray observations with the Fermi Large Area Telescope, and very-high-energy (VHE) gamma-ray observations by VERITAS above 315 GeV, all taken between 2012 April 17 and 2012 June 1 (MJD 56034 and 56079). The contemporaneous variability of the broadband spectral energy distribution is explored in the context of a simple synchrotron self Compton (SSC) model. In the SSC emission scenario, we find that the parameters required to represent the high state are significantly different than those in the low state. Motivated by possible evidence of gas in the vicinity of the blazar, we also investigate a reflected emission model to describe the observed variability pattern. This model assumes that the non-thermal emission from the jet is reflected by a nearby cloud of gas, allowing the reflected emission to re-enter the blob and produce an elevated gamma-ray state with no simultaneous elevated synchrotron flux. The model applied here, although not required to explain the observed variability pattern, represents one possible scenario which can describe the observations. As applied to an elevated VHE state of 66% of the Crab Nebula flux, observed on a single night during the observation period, the reflected emission scenario does not support a purely leptonic non-thermal emission mechanism. The reflected emission model does, however, predict a reflected photon field with sufficient energy to enable elevated gamma-ray emission via pion production with protons of energies between 10 and 100 TeV.
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