Load Growth Research Articles

Pumped Hydroelectric Energy Storage as a Facilitator of Renewable Energy in Liberalized Electricity Market

Besides many benefits deriving from the energy transition process, it is not uncommon for modern power systems to be faced with difficulties in their operation. The issues are dominantly related to the non-dispatchable nature of renewable energy sources (RES) and the mismatching between electricity generation and load demand. As a consequence of a constant peak load growth, this problem is particularly pronounced during the daily peak hours. Therefore, it is of great importance to conduct all necessary activities within the system in order to preserve the system stability and continuity of operation. Energy storage systems have been recognized as a major facilitator of renewable energy, by providing additional operational flexibility. Since pumped hydroelectric energy storage (PHES) accounts for almost 97% of the world’s storage capacity, in this paper, we have investigated the benefits of using pumped-storage hydropower in modern power systems characterized by high penetration of RES and the liberalized electricity market. A novel operation algorithm has been developed which finds the balance between providing additional flexibility by alleviating the peak load and obtaining financial revenue to justify the high investment costs associated with PHES. The algorithm has been tested for the daily and monthly operation of the Tonstad PHES in the dynamic environment of the Norwegian power system.

Infrastructure Investment Alternatives: Competitive and Nontraditional

As the penetration of distributed energy resources (DERs) proliferates, regulatory authorities across the country are viewing DERs as viable alternatives to utility investment in generation and transmission and distribution (T&D) infrastructure. Solar, wind, geothermal, demand response, battery storage, and other technologies are being shown to relieve local load constraints and to meet growing demands at competitive prices. Consideration of such market alternatives provides opportunities for both energy service companies and developers to compete to meet traditional utility needs. While most market opportunities being considered are to meet electricity needs, market alternatives are also being considered for gas utilities where gas infrastructure is constrained or new pipeline moratoriums are in place limiting load growth.

The Challenges and Opportunities of Renewable Energy Source (RES) Penetration in Indonesia: Case Study of Java-Bali Power System

Nowadays, the integration of renewable energy sources, especially grid-connected photovoltaic, into electrical power systems, is increasing dramatically. There are several stimulants especially in the Java-Bali power system, including huge solar potential, a national renewable energy (RE) target, regulation support for prosumers, photovoltaic technology development, and multi-year power system planning. However, significant annual photovoltaic penetration can lead to critical issues, including a drop of netload during the day, ramping capability, and minimal load operation for thermal power plants. This study analyses the duck curve phenomenon in the Java-Bali power system that considers high shares of the baseload power plant and specific scenarios in photovoltaic (PV) penetration and electricity demand growth. This study also analyses future netload, need for fast ramping rate capability, and oversupply issues in the Java-Bali power system. The results showed that the duck curve phenomenon appears with a significant netload drop in the middle of the day because of high power generation from grid-connected PV. Furthermore, the need for fast ramp rate capability is critical for a higher peak load combined with the lowest netload valley. Moreover, the significant load growth with high grid-connected PV penetration level caused unit commitment issues for thermal power plants as baseload operators.

Voltage Regulation and Loss Minimization in Reconfigured Distribution Systems with Capacitors and OLTC in the Presence of PV Penetration

Optimal reactive power management is one of the key operational aspects for efficient planning of distribution system. This study has become more challenging with renewable energy sources integration into the system. Objective of this paper is to address optimal reactive power planning in distribution system using hybrid optimization. This paper presents a comprehensive model for solving capacitor allocation, PV penetration and feeder reconfiguration simultaneously. The objective function considered in this paper includes cost of capacitor, PV and energy loss. The proposed work includes: (i) capacitor allocation using ant lion optimization, (ii) capacitor rating determination using general algebraic modeling system, (iii) reconfiguration of distribution system using genetic algorithm, (iv) investigated different case studies to realize the impact of various load models and load growth factors on reactive power compensation and network reconfiguration, (v) real-time procedure to determine rating of capacitor banks for practical distribution systems, (vi) reactive power dispatch for realistic time-varying load model considering coordination among capacitors, on-load tap changer and photo-voltaic (PV) penetration. The analysis is carried out considering uncertainty of load demand and PV power generation. The proposed methodology is implemented on IEEE 33-bus distribution system and real-time existing Indian distribution network to demonstrate effectiveness of the proposed methodology. It is observed that voltage-dependent load models have a significant impact on system performance and rating of capacitor banks. The proposed strategy ensures optimal solution compared to other existing techniques.

Effective heat transfer surfaces of tubes and plates with spiral vortex generators – inclined oval-trench dimples

Numerical simulation of laminar heat transfer enhancement at the hydrodynamic stabilization length of the tube with 8 inclined longitudinal oval-trench dimples (OTDs) in the transformer oil flow has revealed an optimal inclination angle of dimples, at which a value of thermal and hydraulic performance (THP) is achieved. Heat transfer of a dimpled tube increases by a factor of 28 in comparison with a smooth tube at practically invariable hydraulic losses. Heat transfer enhancement is calculated in turbulent air flow around a flat plate with a package of 16 one-row dimples inclined at an angle of 60° on the longitudinal section of 40 in length and 4 in width under the symmetry conditions at the side boundaries of the plate section and at a dimple step of 2.4. The dimple is 1 in width, 4.5 in length, and 0.2 in depth. Its rounding radius is 0.3. The boundary layer thickness at the section inlet is 0.175. The effect of abnormal separated flow intensification and heat transfer enhancement in dimples has been confirmed. (f/f pl )min=-3, (Nu/Nu pl )max = 4. Relative heat transfer grows by a factor of 1.43 in comparison with the smooth plate and the drag coefficient increases by a factor of 2.08. However the thermal and hydraulic performance defined in terms of heat load growth is 1.12.

Optimal integration of multi-type DG in RDS based on novel voltage stability index with future load growth

In this article, a novel voltage stability index is proposed for the optimal placement and an analytical as well as particle swarm optimization method is implemented for optimal sizing of different types of distributed generation (DG) in a radial distribution system. The three types of DG considered are Type I, Type II and Type IV model. The methods account for changes in long-term system load profile in the planning phase to enhance power system performance. The load model chosen is composite. The optimal power factor and the cost of the DG are also considered. The efficiency of the proposed technique is tested and validated on IEEE 33-bus and 69-bus systems. The significant savings in annual energy loss, reduction in system power losses with upgraded voltage profile is observed for Type IV DG at optimal PF over other types. The results attained are further compared to other analytical and nature-inspired methods to exemplify the dominance of the proposed methodology. The statistical analysis has also been carried out for both bus systems without and with considering all types of DG.

BASIC STAGES OF ENERGY DEVELOPMENT PROGRAM IMPLEMENTATION IN THE CHECHEN REPUBLIC

The article discusses the issues of energy complex development of the Chechen Republic, which requires the creation of a stable multi-vector energy that can satisfy the growing needs of the population and economy of the region. The main emphasis is made on the development of the renewable energy sources, which need to be paid close attention, drawing on the experience of other entities and countries developing innovative technologies in this direction. The analysis of the energy development program implementation in the Chechen Republic (2011-2030) over the past eight years has been carried out, which includes four subprograms describing the potential of resources and the prospects for the energy development in the Chechen Republic,. The estimation of power consumption indicators and maximum loads in the Chechen Republic until 2018 and for the long term (“calculated”, “optimistic” and “actual” options) is given. The analysis of the state and potential for the water energy development in the Chechen Republic is carried out. The analysis of natural resources potential of the republic is carried out in order to implement effectively and develop each of the considered renewable energy sources, taking into account the development of modern innovative technologies to reduce electrical energy consumption. The state estimation of the existing integrated power grid of the Chechen Republic is given, where the initial tasks of work coordination to improve the efficiency of the republic’s energy system are outlined. The results of total indicators of electric grid construction and facilities reconstruction for 2011-2019 are derived. Possible directions (calculated and optimistic options) of the electrical energy industry development are considered. In order to develop successfully the energy sector of the Chechen Republic, taking into account the electrical energy load growth, the development of modern program for the of alternative and renewable energy sources development was proposed that will allow to create additional electrical energy sources in combination with traditional ones. At the same time, the implementation of fundamental and applied research in the field of renewable energy was proposed.

Residual stress distribution in built-in beams

Metallic hyperstatic structures, like beams, submitted to excessive loads, do not fail completely before fully yielding in more than one cross section. Indeed, for built-in beams, three cross sections must be fully yielded before the final failure can occur. So, modeling the evolution of the cross-section residual stress distribution is an important subject that should be addressed to guarantee the stress analysis modeling correctness. This paper analyses the residual stress distribution evolution, in critical cross sections, of built-in beams during a transversal concentrated load growth, until the final failure through hinges formation. A finite element model is also presented. The results show good matches with the numerical model, used as a reference.

Models of SIV rebound after treatment interruption that involve multiple reactivation events.

In order to assess the efficacy of novel HIV-1 treatments leading to a functional cure, the time to viral rebound is frequently used as a surrogate endpoint. The longer the time to viral rebound, the more efficacious the therapy. In support of such an approach, mathematical models serve as a connection between the size of the latent reservoir and the time to HIV-1 rebound after treatment interruption. The simplest of such models assumes that a single successful latent cell reactivation event leads to observable viremia after a period of exponential viral growth. Here we consider a generalization developed by Pinkevych et al. and Hill et al. of this simple model in which multiple reactivation events can occur, each contributing to the exponential growth of the viral load. We formalize and improve the previous derivation of the dynamics predicted by this model, and use the model to estimate relevant biological parameters from SIV rebound data. We confirm a previously described effect of very early antiretroviral therapy (ART) initiation on the rate of recrudescence and the viral load growth rate after treatment interruption. We find that every day ART initiation is delayed results in a 39% increase in the recrudescence rate (95% credible interval: [18%, 62%]), and a 11% decrease of the viral growth rate (95% credible interval: [4%, 20%]). We show that when viral rebound occurs early relative to the viral load doubling time, a model with multiple successful reactivation events fits the data better than a model with only a single successful reactivation event.

Mechanism design of a small mobile robot for inspection of underground cables-in-pipe

With the rapid growth of urban power load, underground cables-in-pipe is increasingly used in urban power transmission. The operation status inspection of underground cables-in-pipe is very important to guarantee the safety of power transmission. At present, mostly, the inspection of the underground cables-in-pipe is implemented by workers after cutting the power supply. Cutting power supply will cause economic loss. In addition, the workers cannot step into the narrow pipes, which lead to low inspection efficiency and the high omission factor. In order to solve the above problems, this paper proposes a novel mechanism of a small mobile robot for underground cables-in-pipe inspection. In the pipes where cables have been laid, the remaining space is narrow and irregular. Through the unique compact design of the robot mechanism, we make the robot able to run smoothly in the pipes. In this paper, we firstly establish the remaining space model of the cable-laid pipes. Then design the mechanism model of each part of the robot. After that, we determine the specific structural parameters. Finally, we carry out the feasibility analysis of the whole robot mechanism. The results of the analysis indicate that, the designed robot mechanism can move smoothly in underground cable pipes.

Coordination of Distribution Network Reinforcement and DER Planning in Competitive Market

Since distributed energy resources (DERs) can provide capacity in distribution system, distribution network reinforcement interacts with DER planning (DERP) for meeting load growth. This article proposes the coordination of distribution network reinforcement and DER planning in competitive market. The model is formulated as a multi-stage programming. In first stage, distribution companies (DISCOs) and DER aggregators (DERAs) make bidding plans for network reinforcements and DERP. In second stage, DSO checks the network security. If the check fails, DSO sends capacity signals to DISCOs and DERAs for more capacities. In third stage, the distributed market is cleared by DSO’s optimal operation problem and distribution locational marginal price (DLMP) is returned to DERAs as price signal. An iterative algorithm is proposed to solve the multi-stage model. The algorithm embodies the process of information interaction among DISCOs, DERAs, and DSO, where DISCOs and DERAs compete in capacity market under DSO’s supervision. Numerical results on IEEE 33-system and an actual 141-bus system demonstrate that the proposed model coordinates distribution network reinforcement and DERP in competitive market.

Calculation of the overhead transmission line conductor temperature in real operating conditions

The integration of fluctuating renewable sources, load growth and aging of the current power system is the major reasons for the development of the electric power engineering. Transmission lines are recently facing new technical and economic challenges. The immediate utilization of advanced technologies and modern methods could solve these issues. This study deals with the transmission and distribution of electrical energy with orientation on the calculation of operating temperature on the conductor of transmission line, which is under actual current load. The load of the transmission line is limited with allowable operating temperature. The operating temperature should not exceed the allowable operating temperature because the conductors of the transmission line have mechanical limit from the standpoint of deflection of conductors. The operating temperature as well as operating conditions of the conductor is determined by the type and material of the ACSR conductor. This article aims to propose the suitable calculation methods of the operating temperature of the overhead transmission line conductor in real operating conditions (external weather influences, current loading and corona effect). The originality of this proposed method (by differential equation) lies in considering corona effect. This improves the accuracy of the calculation of the operating temperature of the conductor under real conditions. In this article, the calculations are compared according to methodology of differential equation and methodology described in CIGRE Technical Brochure 601—guide for thermal rating calculations of overhead lines. The methodology of differential equation counts with or without losses by corona. The article also compares these methods of operating temperature during days in various different weather conditions like environment temperature, solar irradiance, wind speed and direction. It was found that under the action of the corona, the temperature of the conductor increases to a small extent.

Ɛ‐constraint multiobjective approach for optimal network reconfiguration and optimal allocation of DGs in radial distribution systems using the butterfly optimizer

In recent days, the optimal allocation of distributed generators (DGs) problem in the distribution system caught several reader's attention to improve the system efficiency, to meet the future load growth. In this article, a multiobjective approach is proposed to determine the optimal locations for DGs, optimal DGs sizes, optimal power factors of DGs in the presence of optimal network reconfiguration to maximize the maximum loadability (λmax), minimize the active power loss and maximize the loading margin factor (λv) of the system. Butterfly Optimization (BO) algorithm is implemented to optimize the desired objectives. The Ɛ-constraint method is used for multiobjective optimization, spanning tree technique is used for checking the radiality of the system and modified repetitive power flow using radial load flow algorithm is developed for finding theλmax, λv.The proposed approach is tested on 33 bus and 69 bus radial distribution test systems. Four scenarios are considered to achieve the desired objectives and each scenario consists of two cases: optimal allocation of DGs in the initial configured network, optimal allocation of DGs in the optimal reconfigured network. Results suggest that optimal allocation of DGs in scenario 4 gives a better improvement in maximum system loadability, loading margin factor, and active power loss reduction of the system. Obtained results compared with the suitable methods and algorithms that are available in the literature.

Central Asian Rodents as Model Animals for Leishmania major and Leishmania donovani Research.

The clinical manifestation of leishmaniases depends on parasite species, host genetic background, and immune response. Manifestations of human leishmaniases are highly variable, ranging from self-healing skin lesions to fatal visceral disease. The scope of standard model hosts is insufficient to mimic well the wide disease spectrum, which compels the introduction of new model animals for leishmaniasis research. In this article, we study the susceptibility of three Asian rodent species (Cricetulus griseus, Lagurus lagurus, and Phodopus sungorus) to Leishmania major and L. donovani. The external manifestation of the disease, distribution, as well as load of parasites and infectiousness to natural sand fly vectors, were compared with standard models, BALB/c mice and Mesocricetus auratus. No significant differences were found in disease outcomes in animals inoculated with sand fly- or culture-derived parasites. All Asian rodent species were highly susceptible to L. major. Phodopus sungorus showed the non-healing phenotype with the progressive growth of ulcerative lesions and massive parasite loads. Lagurus lagurus and C. griseus represented the healing phenotype, the latter with high infectiousness to vectors, mimicking best the character of natural reservoir hosts. Both, L. lagurus and C. griseus were also highly susceptible to L. donovani, having wider parasite distribution and higher parasite loads and infectiousness than standard model animals.

Multi-year load growth-based optimal planning of grid-connected microgrid considering long-term load demand forecasting: A case study of Tehran, Iran

Although much efforts have been devoted to the optimal design of the energy systems, there is a research gap about the multi-year load growth-based optimal planning of microgrids. This paper tries to fill such a research gap by developing a novel method for the optimal design of the grid-connected microgrids based on the long-term load demand forecasting. The multilayer perceptron artificial neural network is used for time-series load prediction. The impacts of the annual load growth are analyzed under various cases based on the consideration and determination methods of yearly load growth. The proposed method is applied to an actual microgrid in Tehran, Iran, using HOMER (Hybrid Optimization of Multiple Energy Resources) software. The load modeling’s capabilities of HOMER software, as a well-known software for the optimal design of energy systems, are used, which have received less attention. Since most existing research works in Iran focused on the off-grid operating mode, the study of an actual microgrid under grid-connected operating mode is one of the most contributions of this paper. The comparison of the obtained results and other available methods illustrate the impacts of the adequately precise estimation of annual load growth in the design of energy systems.

An Agent-Based Approach for the Planning of Distribution Grids as a Socio-Technical System

Recent developments, such as smart metering, distributed energy resources, microgrids, and energy storage, have led to an exponential increase in system complexity and have emphasized the need to include customer behavior and social and cultural backgrounds in planning activities. This paper analyzes how emergent behavior in electricity consumption can affect the planning of distribution grids with a smart grid vision. For this, an agent-based model that uses insights from the field of behavioral economics to differentiate four consumer categories (high income, low income, middle class, and early adopters) was used. The model was coupled with a real distribution feeder and customer load curve data, and the results showed that heterogeneity of customer’s preferences, values, and behavior led to very distinct load growth patterns. The results emphasize the relevance of modeling customer’s behavioral aspects in planning increasingly complex power systems.

Planning and reliability assessment to integrate distributed automation system into distribution networks utilizing binary hybrid PSO and GSA algorithms considering uncertainties

Around the world, automation is transforming work, business, and the economy as one of the Pillars of a smart grid. The vital role behind utilizing the automation system into distribution networks is to achieve grid self-healing and improve the reliability level. Distributed Automation (DA) can be achieved via Smart secondary substations at each load point with installed automatic sectionalize switches that need a large investment. Therefore, this paper provides a long-term plan based on a cost/benefit study to define the optimal automation level of Distribution networks constrained with system reliability indices limits. DA planning is categorized as a non-linear Mixed Integer optimization problem with multi-dimensions. Hence, it is not possible to apply numerical algorithms to directly search for all possible automation scenarios. To solve that problem; Hybrid Particle Swarm Optimization and Gravitational Search Algorithm (HPSO-GSA) technique provides a binary-coded procedure to handle all the controlled variables to provide the best solution within the permissible limits. The effectiveness of the proposed methodology is demonstrated by applying it to RBTS-Bus 4 standard reliability test system considering uncertainty in Cost Damage Function (CDF), Investment Cost (IC), and Failure Rate (FR). Also, this paper study the effect of change in Depreciation ratio (DR), Load Growth (LG) rate besides; peak Load Change (LC). Finally, a reliability assessment using NEPLAN software is done for the optimal decision to enhance the technical analysis. Moreover, Distributed Generations (DG) has a significant impact on the reliability of distribution networks. Simulation results indicate that the system reliability cost is significantly reduced with adequate system reliability level, with comparative results to those in literary studies.

Impact of replacing overhead lines with aerial bundled cable, and installation of new transformers to reduce losses and improve distribution network voltage profiles, technical and economic analysis

AbstractToday, reducing distribution system losses is a top priority in the design and operation of electricity grids. In an electricity grid, a significant percentage of the power and energy generated in power stations is wasted on the way to the transmission system. Losses can occur at all levels of the system's power, namely, production, transmission, and distribution system. The low voltage level, high current level, and radial distribution system structure leads to an increase in the percentage of losses in the distribution sector. For example, in 2018, about 80% of power system losses occurred in distribution systems in Iran. Several methods have been proposed to reduce the losses such as placing capacitors at medium and low voltage levels, reconfiguring the grids, increasing the cross‐section in conductors, and so on in recent years. In this article, two practical and effective solutions to reduce losses in the distribution system are studied and analyzed. The first solution is to install transformers in overload points of the network to reduce technical losses and increase the reliability and stability of the grid and improve voltage profiles, and the second solution is the plan to replace the overhead lines with the aerial bundled cable to reduce nontechnical losses. Sheet 13 of Qom distribution system is considered as a study network in order to investigate and analyze the impact of implementing these two proposed solutions in reducing losses and it also uses the data of data logger device installed in the distribution system as well as the simulation data obtained in the CYMDIST software. In order to more accurately and comprehensively analyze the impact of the proposed solutions on loss reduction, based on the annual load growth in the Qom distribution system, studies are presented for 5 years. Finally, based on two suggested solutions, three scenarios are presented and the effective scenario is identified and the economic justification and duration of return on the effective scenario are presented.

Heat Waves: A New Danger for the Russian Power System

In this study, changes in temperature extremes in Russia are considered and the impact of these changes on the balance sheets of Russian power systems is analyzed. On the basis of the current meteorological observations and energy statistics, the change observed in extreme climatic characteristics over the past seventy years is calculated and its impact on power-grid regimes is estimated. It is established that the climate changes in Russia manifesting themselves in increasing air temperature in all regions and all seasons lead to a slowdown in the growth of winter and an increase in the growth of summer peak loads in almost all power grids, thereby contributing to an increase in the reliability of the energy supply. At the same time, disruptions of the electricity supply may arise in the southern energy-deficient regions in the summer as a result of violating the intersystem links and operation modes of generating facilities due to weather and climatic factors.

Techno-economic feasibility of a photovoltaic-equipped plug-in electric vehicle public parking lot with coordinated charging

Electrification of transport and the deployment of plug-in electric vehicles (PEVs) shift emissions from tail-pipes to bulk power systems (BPSs). Coordinated distributed energy resources and PEV charging can mitigate the impact of this shift. This study presents an analysis of photovoltaic (PV) solar parking lots that address this benefit. Real-world charging data, solar data, and electricity tariffs are used to determine the microgrid system that minimises the cost of retrofitting an existing parking lot with PV and PEV infrastructure coupled. The result is a load scheduling algorithm that takes into account tariffs and insolation to reduce costs while ensuring customer satisfaction. The techno-economic feasibility of PV infrastructure in the microgrid is determined by minimising the net present cost (NPC) in two case studies: Victoria, BC, and Los Angeles, CA. Relatively low solar irradiation and electricity prices make it economically infeasible to install solar panels in Victoria even though the operational costs are reduced by 11%. In Los Angeles, high time-of-use prices, together with abundant solar radiation, make PV retrofitting economically feasible with any array capacity. At the current solar infrastructure price, coordinated charging in this region yields 8–16% savings on NPC and smaller feeder size requirements with greater load growth opportunities.