Showing papers in "International Journal of Renewable Energy Research in 2018"

Power Flow Control of PV-Wind-Battery Hybrid Renewable Energy Systems for Stand-Alone Application

Abstract: The main problem in renewable energy system is the variation in power generation from time to time due to the intermittent nature of the renewable sources. Miss matching between power generation and load power causes a deviation from the desired voltage and frequency in power supply. A power flow control of a standalone photovoltaic-wind-battery Hybrid Renewable Energy System (HRES) for stand-alone application is presented here to balance the power generation and load power. Photovoltaic (PV) and wind are the primary power sources and battery acts as backup source to balance the power generation and load power. In spite of sudden load changes and changes in the power generation from PV power and wind power the power balance between the supply and demand effectively maintained by the proposed fuzzy logic controller (FLC). All the renewable sources and backup source are linked to a DC bus through dc-dc converter and the DC bus is connected to AC load through a voltage source inverter. A control strategy is implemented with fuzzy logic controller for smoothing of the power fluctuation and at the same time to maintain the battery state of charge (SOC) with in allowable limits. The various components are modeled and simulated in MATLAB/Simulink. Simulation results justify the ability of proposed controller to balance the power generation and load power.

A Review on Optimal Allocation and Sizing Techniques for DG in Distribution Systems

Abstract: Distributed Generation (DG) offers the reliable and economic source of electricity to consumers. These are connected directly to the distribution system at consumer load points. Integration of DG units into an existing system has significantly high importance due to its innumerable advantages. However, Optimal DG (ODG) allocation and sizing is always a challenging task for utilities as well as consumers. The major objective of ODG allocation and sizing is to improve system overall efficiency with minimum power loss, maximum system security, voltage stability, and reliability. Analytical techniques are performing well for small and simple systems, not suitable for a system with large and complex networks. However, various meta-heuristic techniques are performing better in terms of accuracy and convergence for extensively large and complex networks. A hybrid optimization is a combination of two or more optimization techniques. This technique offers efficient and reliable global optimum solutions for complex multi-objective problems. In this context, a comprehensive literature review of DG fundamentals and the different technical approaches for DG integration into the distribution system are analyzed here. Furthermore, an attempt has been made for comparison of analytical, classical (non-heuristic), meta-heuristic and hybrid optimization techniques with respect to objective function, test system, advantages, and disadvantages. This present study will give in-depth knowledge and acts as a forthright reference for imminent investigators and investors for ODG allocation and sizing in a distribution system.Â

Optimal Economic Operation of Microgrids Integrating Wind Farms and Advanced Rail Energy Storage System

Abstract: In this study, an economic model is proposed to simulate the optimal operation of a grid-connected microgrid regard to the uncertainties of microgrids’ components. In this study, the wind farms are considered as renewable resources and an innovative technology of advanced rail energy storage (ARES) is deployed as a storage unit. In the optimization model, the stochastic nature of wind energy and the intermittency of loads are contemplated in the model by employing scenario-based Monte Carlo approach to simulate the implication of uncertainties. The objective function of the optimization problem is defined subject to maximize the profit of microgrid’s components, and the problem is solved by employing crow search algorithm (CSA). Ultimately, the results of the numerical study are presented and discussed which confirm the effectiveness of the model and appropriate performance of the selected storage technology.

Feasibility analysis of PV/wind/battery hybrid power generation: A case study

Abstract: Depletion of fossil fuel reserves, unpredictable fluctuation of diesel prices, and global warming issue have motivated numerous countries to produce new policies for energy that engorge the utilizing of alternative energy sources. Renewable energy resources like solar, hydro, and wind are clean and have potency to be more widely used. Integration of these sources together with back-up units can produce a better clean, economic, and reliable power for all loads conditions as compared to single source systems. The feasibility study of using integrated energy system to supply electric energy for remote rustic school in the southern part of Iraq is investigated in this research paper. In order to carry out the feasibility study of the hybrid system, HOMER software has been employed as a tool for the technical, economic, and environmental assessments. The analyses of the optimal energy systems are explained in details to find the most feasible off-grid system and compared with the options of extension to the grid and diesel generator system.

Diffuser Augmented Wind Turbine (DAWT) Technologies: A Review

Abstract: Diffuser Augmented Wind Turbines (DAWT) are an optimised class of wind turbines that use the theory of a Diffuser to accelerate and direct air flow onto a wind turbine rotor to drive it for higher rotations-per-minute and power output. This power output is typically measured and rated in terms of the power augmentation. Diffuser theory was pioneered in the 1970’s and has re-emerged in recent years with a range of new technological approaches to achieving laminar wind profiles, low exit pressures, improved pressure recovery, reduced blade tip losses, improved torque generation and adaptability to wind directional and speed changes. Research has been pivotal in the advancement of design and performance of DAWT’s with CFD remaining a critical analysis tool. Power augmentations have been realistically achieved within the range of 2-3 for small-medium scale turbines. In this review, ground-based Diffuser technologies have been presented primarily according to rotor type. Large-scale on-shore and off-shore concepts have been presented along with airborne technologies. Building-integrated DAWT’s are then presented with a description of some of the influential economic and technical factors that currently affect and will continue to affect the development of the DAWT industry. DAWT’s prove to have a realisable significant potential even when considered in applications across the wind turbine sector. The current DAWT industry is mostly research-based with very little commercialisation as the majority of technologies presented here are in their early developmental stages. It is expected that subsequent research and innovation in this field will be able to advance this issue to allow DAWT’s a credible chance as a key player in the wind technology sector.

Simulation and Feasibility Studies of Rooftop PV System for University Campus Buildings in Surabaya, Indonesia

Abstract: Present work simulates and analyzes the rooftop photovoltaic (PV) system on buildings roofs of the University of Surabaya, Indonesia for electricity power generation. The work also to calculate greenhouse gas (GHG) emission reduction that can be obtained by PV system mounted on the building roofs. The surface area of the roofs was determined using Polygon feature of Google Earth TM . The energy output of the system was simulated with SolarGIS pvPlanner software program. The grid-connected PV system type was chosen in the simulation. Greenhouse gas (GHG) emission reduction analysis was carried out using RETScreen program simulation. It was found that about 10,353 m 2 of the rooftop of the university buildings could be used for panel installation. The total capacity of the panels is found about 2,070 kWp with total electricity production is about 3,180 MWh per year and could supply up to 80% of the campus energy demand. The system would serve as a means of reducing 3,367.6; 2,477.2, or 1,195.7 tons of CO 2 to the atmosphere in comparison to the same amount of electricity produced by burning coal, oil, or natural gas respectively. The unit cost of PV electricity was found ranging from 0.10 – 0.20 USD/kWh. From economic aspects, the rooftops PV system has the potential to provide power at a competitive cost in comparison to other alternative options of power generation.

Optimization of Size and Cost of Static VAR Compensator using Dragonfly Algorithm for Voltage Profile Improvement in Power Transmission Systems

Abstract: Voltage stability is a major concern in power transmission systems due to mismatch between power generation and demand. Hence maintenance of voltage profile within the acceptable limit becomes a challenging task. In this paper the weakest buses for implementing the reactive power compensators are identified by eigenvalue decomposition technique on partitioned Y-admittance matrix. The size and cost of the SVC are optimized using dragonfly algorithm. The algorithm is implemented on IEEE 14 and 30 bus systems and the results obtained with and without the placement of Static VAR Compensators are compared with the results of other algorithms to show its effectiveness. The further scope of this work is to extend this to renewable energy by implementing the wind generators at the weakest buses there by reducing the electrical distance between the generators and the farthest load buses and securing the system from voltage collapse.

Control of Bidirectional DC-DC Converter in Renewable based DC Microgrid with Improved Voltage Stability

Abstract: Providing stable voltage at nominal level according to universally accepted standards is a primary concern of any public electricity network. In a renewable energy fed power electronic based DC microgrid system, renewable sources can have fluctuating power characteristics due to various environmental factors. In such an environment, chances of voltage instability are highly probable due to varying power nature of renewable sources and loads connected. In this paper, a bidirectional converter connected with battery storage is controlled based on the voltage of the micro grid in order to tackle the aforementioned problem. A selector based control algorithm in conjunction with proportional integral controller is used to trigger the bidirectional converter. Proposed control technique is simulated and implemented in a 60V DC microgrid and results are analysed.

Optimal sizing and placement of DG units in radial distribution system

Abstract: The continuous growth of electricity demand has presented a new challenge for power system utilities in preserving the system efficiency. Thus, Distributed Generation (DG) has attracted a lot of interest since it provides clean, reliable and cost-effective power supply. However, DG type, location and size should be properly chosen. To this end, this paper presents a DG placement and sizing method regarding system losses reduction, voltage magnitude and stability enhancement. The system weakest buses were selected for DG allocation in the basis of sensitivity methods and optimal DG size of a single DG unit has been determined by means of the quadratic curve-fitting technique. Multiple DG units’ placement has been performed using loss improvement and loss reduction indices. Proposed approach has been applied to the 33- bus distribution system. Power system modeling and simulations have been performed using MATLAB\PSAT toolbox. Simulation results have shown accurate and satisfactory results in enhancing the steady-state voltage profile and decreasing total power losses.

Optimal Placement of Distributed Generators with Regard to Reliability Assessment using Virus Colony Search Algorithm

Abstract: The integration of distributed generation (DG) resources is growing day by day in electricity grids. There are many reasons which persuade the operators to utilize DGs such as restrictions on the construction and development of transmission lines and distribution network, transition of traditional power systems to restructured electricity markets, the competitive conditions in wholesale and retail markets, the implication of economic and environmental issues in the production of electrical energy, increasing the system reliability and customer satisfactory level. The reliability improvement capability of power systems by utilization of these units has attracted the attention of many electrical engineering experts and power system planners and operators. Reliability plays a prominent role in the satisfaction of all power industry participants, especially the consumers of the electricity. In this paper, the effect of distributed generation units on the power system reliability has been investigated. Therefore, the virus colony search (VCS) algorithm is employed to determine the optimal placement and size of distributed generators subject to improve the reliability indices. The simulation is carried out on a 34-bus IEEE test network. The optimization results are also compared with the results of both genetic algorithm (GA), particle swarm optimization (PSO) algorithm, differential evolution (DE) algorithm, multi-objective particle swarm optimization (MOPSO) algorithm, modified shuffled frog leaping algorithm (MSFLA), gravitational search algorithm (GSA), biogeography-based optimization (BBO) algorithm, hybrid big bang-big crunch (HBB-BC) algorithm and glowworm swarm optimization (GSO) algorithm.

Assessment and mapping of solar energy potential using artificial neural network and GIS technology in the southern part of India

Abstract: Prediction and assessment of solar radiation are necessary pre-requisites in developing solar technology. Here, an artificial neural network (ANN) model has been developed to predict solar energy potential in the Southern part of India: Andhra Pradesh (AP) and Telangana State (TS), lie between 12°41' and 22°N latitude and 77° and 84°40'E longitude. Generalized feed-forward with back-propagation neural networks were considered using MATLAB. Three layered neural network with different architectures are designed and evaluated. For training and testing the network, geographical and meteorological data of 28 sites over a period of recent 22 years from the NASA geo-satellite database were taken. Geographical parameters (latitude, longitude and altitude), meteorological data (temperature, sunshine duration, relative humidity and precipitation) were used as input data, whereas the mean solar radiation was used as the output of the network. All the parameters taken here are in the form of monthly mean. The ANN model has been evaluated for test locations by calculating mean absolute percentage error (MAPE). The correlation coefficients (R-value) between the output of model and the measured value of solar radiation is calculated.  The R-value were more than 0.95, which show high reliability of the model for prediction of solar radiation anywhere within AP and TS. Solar radiation of major cities was predicted using developed model. Predicted solar radiation is analyzed and used to create monthly mean maps using GIS technology. These maps can be useful to estimate solar energy potential at any locations within AP and TS.

What are the Current Status and Future Prospects in Solar Irradiance and Solar Power Forecasting

Abstract: In the most countries around the world, solar photovoltaic power plants have a cost-competitive structure for providing energy access and for increasing electricity production. However, solar photovoltaic power integration requires the handling of power quality and stability problems due to its non-controllable and intermittent characteristics. At this point, the need for reliable solar irradiance and solar power forecasting is emerged for the optimal modeling and scheduling of solar photovoltaic power plants. For this purpose, this study conducts an exhaustive and up-to-date review of solar irradiance and solar power forecasting methods used in the literature. Although there are a plenty of review papers in the literature, differently, we have created the extensive and comparative literature tables considering very-short term, short-term, medium-term and long-term forecasting periods in this study. Furthermore, we have examined each paper in terms of its input data, forecasting interval, forecasting model, forecasting accuracy and forecasting results. As a result of overall assessments, this study provides complete and considerable information about the current status and future prospects in solar irradiance and solar power forecasting.

Implementation of an improved Coulomb-Counting Algorithm Based on a Piecewise SOC-OCV Relationship for SOC Estimation of Li-Ion Battery

Abstract: Considering the expanding use of mobile devices equipped with rechargeable batteries, especially Li-ion batteries that have higher power and energy density, the battery management function becomes increasingly important. In fact, the accuracy of the amount of remaining charges estimation is critical as it affects the device autonomy. Therefore, the battery State-Of-Charge (SOC) is defined to indicate its estimated available capacity. In this paper, a method for Li-ion battery SOC estimation based on an enhanced Coulomb-counting is proposed to be implemented for multimedia applications. Assuming that Coulomb-counting suffers from cumulative errors due to the initial SOC and the measurements uncertainties errors, we used a piece-wise linear SOC-OCV relationship and periodic re-calibration to overcome these limitations. This solution has been implemented and validated on a hardware platform based on PIC18F MCU Family. The measurement results were correlated with theoretical ones and the method has shown a reliable estimation since accuracy is less than 2%.

Assessment of Photovoltaic Energy Production at Different Locations in Jordan

Abstract: Jordan is considered one of the sun-belt countries, which possesses high solar radiation on its horizontal surface. This work presents the energy output of photovoltaic (PV) module for three sites in Jordan; these three sites are Irbid (32° N and 35° E) in the northern Jordan, Amman (32° N and 36° E) in the central Jordan, and Aqaba (29° N and 35° E) in southern Jordan. The paper analyses the solar radiation data and ambient temperature to compare the PV energy output at these sites. The analysis showed that the Aqaba is the optimum location in term of PV energy production compared to the selected study locations. It is found that the annual energy production for a module with 340 W capacities is 502 kWh.

Economic Analysis of Integrated Renewable Energy System for Electrification of Remote Rural Area Having Scattered Population

Abstract: The renewable energy sources (RES) are globally recognized as a suitable option for sustainable development in many off-grid applications. Recently, the integrated systems with two or more RES are being paid great attention for electrification of isolated areas and found to be an acceptable solution rather than uneconomical grid extension. In the present study, the integrated renewable energy system (IRES) model is developed using solar, wind, biomass and biogas energy sources to meet the electricity demand of the isolated rural community of Khatisitara village of Gujarat state in India. The operational strategy of IRES model is developed considering the distribution network losses as a system design parameter. The developed IRES model is optimized for minimum net present cost of the system using particle swarm optimization (PSO) algorithm in MATLAB environment. The well-established genetic algorithm (GA) was used to validate the optimization results obtained from PSO. Further, the effects of distribution losses (DL) on the system sizing, reliability and economy have been evaluated. The sensitivity analysis was performed to assess the effect of economically influencing parameters on the developed model. Finally, the break-even analysis was performed for the grid extension distance to examine the economic feasibility of IRES against grid extension. The simulation result shows that the impacts of DL on IRES reliability and economy are significant. Further analysis shows that the IRES using locally available renewable energy sources is a feasible option for rural electrification in considered study area rather than grid extension.

Dynamic Reconfiguration of Electrical Connections for partially shaded PV Modules: Technical and Economical Performances of an Arduino-based Prototype

Abstract: The solar energy is an ever-growing power source among all the renewable ones. Several issues shall be faced by power engineers as far as the design of photovoltaic (PV) plants is concerned. One of these consists in the “partial shading”, that is the non-uniform irradiation on different cells of the same PV module or different modules of the same PV plant. The partial shading leads to undesired effects, such as the electrical mismatch, with possible generation of hot spots, and generally to a decreased production of electric energy. To mitigate the partial shading effects, different methods are feasible. Among them, the dynamic reconfiguration of the electrical connections between modules represents an effective solution. In this paper, an algorithm of reconfiguration for a small-scale PV plant is proposed and the experimental results showing the related benefits in terms of energy recovery are reported.

A Review: Control Strategies for Power Quality Improvement in Microgrid

Abstract: Power generation through the renewable energy sources has become more viable and economical than the fossil fuel based power plants. By integrating small scale distributed energy resources, microgrids are being introduced as an alternative approach in generating electrical power at distribution voltage level. The power electronic interface provides the necessary flexibility, security and reliability of operation between micro-sources and the distribution system. The presence of non-linear and the unbalanced loads in the distribution system causes power quality issues in the Microgrid system. This paper explores and reviews different control strategies developed in the literature for the power quality enhancement in microgrids. Also comparisons of different control methods are presented with suggestions for future research.

A Review on Energy Harvesting Potential from Living Plants: Future Energy Resource

Abstract: Renewable energies (RES) has been discussed and explored by researchers in the past decades, has proved that it can decline the capital cost of electricity generated. Such sources such as solar energy and wind energy continue to take advantage in development, securing long-term sustainable energy for the future. Demand for these renewable enrgy leads to a reduction of pollution and leaning towards green energy environment. Hence, as the live tree has been discovered to be able to generate a weak source of electricity, it cannot be overlooked as those potential can be used as power source for low-powered devices. Thus, this paper reviews the concept of living plant energy harvest and the real-life prectice of the technique. Living plant energy overview is also done together for future challenges.

An Efficient Passive Islanding Detection Method for Integrated DG System with Zero NDZ

Abstract: In this paper an efficient passive islanding detection scheme is presented for renewable distributed generation (DG). Islanding is caused if DG supplies power to load after disconnecting from the grid due to system failure or an act of nature. As per the DG interconnection standards, it is required to detect the islanding within 2 seconds after islanding with the equipments connected to it. In this paper, the islanding is detected with the combined changes of rate of change of positive sequence voltage (ROCOPSV) and rate of change of positive sequence current (ROCOPSC). The islanding is detected if both the values of ROCOPSV and ROCOPSC are more than a predefined threshold value. The test system results carried on MATLAB shows the performance of the proposed method for various islanding and non islanding events with different power imbalances. Various non islanding cases like capacitor switching, load swithching are also clearly differentiated with islanding events. Islanding detction is posible at balanced islanding with zero non detection zone (NDZ) by proposed technique.

Probabilistic SCUC Considering Implication of Compressed Air Energy Storage on Redressing Intermittent Load and Stochastic Wind Generation

Abstract: There are various sources of uncertainty in power systems. Solar and wind forecasting inaccuracies, price forecasting errors, load and demand response forecasting volatilities are some types of uncertainty. In addition, the possibility of outage of power system components such as lines, generating units, and loads can deteriorate the operation condition and compromise the security of power system. Hence, in order to reach a more secure operation, the uncertainties must be included in the scheduling to enhance the robustness and resiliency of power system against possible imbalances and contingencies. The inclusion of probabilistic concepts into the security-constrained unit commitment (SCUC) makes the solution of this problem more complex. However, incorporation of them into the SCUC ensures the secure operation of the power system and inhibits drastic detriments. Furthermore, the compressed air energy storage (CAES) technology is utilized to mitigate the intermittencies and uncertainties. The uncertainties are modeled by using scenario generation techniques. The simulation of a large number of stochastic scenarios considering a variety of uncertainties inclines the results to the most probable condition of realization. The results show that even though the stochastic approaches have higher operational cost but it maintains the security of the system for withstanding against plausible uncertainties and contingencies, which may occur due to whether inaccurate forecasting and consequently inappropriate scheduling or maintaining inadequate generation reserve or transmission capacity. In addition, the integration of CAES units has diminished the total cost of operation and has improved the penetration of renewable resources regard to the congestion of the system, especially at peak hours.

Optimal Sizing and Management of Hybrid Renewable Energy System for Highways Lighting

Abstract: The energy consumption for the purpose of lighting has comprised about 30% of energy consumption and around 45% to 50% of peak load in Iran. Based on the statistics of the road maintenance and transportation organization of Iran (RMTO), the quantity of installed lighting equipment had significant growth in recent years. An appropriate combination of renewable energy resources leads to reliable, green and economic generation system. Using hybrid solar-wind systems to supply street lightings' required energy with low-power lamps is an impressive method to decrease energy consumption. In this paper, a comprehensive study is carried out to achieve an optimal design for a hybrid solar-wind system that supplies electricity to the roads and highways lights in Iran. In the proposed approach, to achieve an optimum design for the hybrid system, suitable options for each part of the system is selected according to its technical specifications, and then the capacity and the number of components is determined in order to minimize an objective function comprised of a cost function, loss of power supply probability (LPSP) and subject to satisfy prevailing technical constraints. Bat algorithm (BA) is employed to solve the proposed optimization problem. Simulation results show the effectiveness of the proposed method in various situations of operation for the case study of Tabriz city regard to pertaining load profile and weather data. The case study is categorized into three scenarios in which the hybrid system has different schemes, and the results show that the proposed hybrid system is notably practical and cost-effective to supply electrical energy of highway and street lightings.

LFC for Autonomous Hybrid Micro Grid System of 3 Unequal Renewable Areas using Mine Blast Algorithm

Abstract: This paper ensures the feasibility of the proposed 3-area hybrid micro grid system (3A-HµGS) comprising of highly intermittent energy sources like wind turbine generator (WTG), parabolic trough collector (PTC), and PV arrays. Renewable energy sources (RES) inherently set in power and frequency oscillations as these sources (RES) are extremely influenced by climatic behavior that’s why the erection of 3A-HµGS as a controlled dispatch able unit is in fact very difficult to be realized but this proposed system has considered diesel engine generator (DEG) as a back-up source and the energy storage system (ESS) like battery, ultra-capacitor and fuel cell as the dynamic devices to make it controllable and reliable. Unwanted frequency deviation has been restricted to a satisfactory limit through GA, PSO and MBA based proportional integral derivative (PID), proportional integral derivative with filter (PIDN) and 2 degree of freedom PID (2DOF-PID) controllers. MBA based 2DOF-PID controllers provide the best coordination among RES, ESS, and DEG to maintain the power quality of 3A-HµGS. A qualitative and quantitative analysis of the dynamic responses under all the controlling actions clearly exhibits the efficacy of the proposed system. Moreover, the system remains stable even after incorporation of natural disturbances like change in wind velocity and solar irradiances which ensure the feasibility and practicality of the proposed 3A-HµGS.

Enhanced Hybrid Global MPPT Algorithm for PV Systems operating under Fast-Changing Partial Shading Conditions

Abstract: A global maximum power point tracking algorithm including an artificial neural network and a hill climbing method is combined. The proposed solution is suitably designed for handling fast changing partial shading conditions in photovoltaic systems. Through only a limited number of preselected current measurements, the proposed algorithm is capable to automatically detect the global maximum power point of the photovoltaic array, also minimizing the time intervals required to identify the new optimal operating condition. The method does not require any information on the environmental operating conditions and it is cost-effective, with no additional hardware requirements. The analysis of different artificial neural network structures has pointed out that a simple network can be used when the not-uniform shading conditions change slowly. On the other hand, in the case of solar electric vehicles moving in a city it is necessary the use of more complex structures to reach satisfactory performance.

Integrated Demand Side Management and Generation Control for Frequency Control of a Microgrid Using PSO and FA based Controller

Abstract: This paper applies demand side management (DSM) method as a new control strategy for frequency control in a microgrid powered by the diesel driven generator (DDG), wind and solar photovoltaic (PV) power sources. In order to level the frequency fluctuation due to intermittent power generation, the power consumption of the non-critical loads (i.e., heat pump, freezer) and power charging-discharging of plug-in hybrid vehicles (PHEV) are controlled through the controllers (PI/PID). The parameters of the controllers are optimized using Particle Swarm Optimization (PSO) and Firefly Algorithm (FA). Different disturbance conditions such as step perturbation and random variations of load, solar PV and wind output power has been considered to investigate the performance of the microgrid. Simulation studies confirmed that the performance of the FA optimized PID controller is better than the PSO optimized PI/PID controllers and FA optimized PI controller in terms of frequency deviation and setting time.

Optimal Planning of a Multi-Carrier Microgrid (MCMG) Considering Demand-Side Management

Abstract: The multi-carrier microgrid (MCMG) is a restricted district comprising convertors and energy storage systems (ESSs) that are used to fulfill various energy demands. The structure and optimal operation of these MCMGs with regard to fulfilling multi-carrier demands are presented in relation to their rapid spread. In this paper, a two-stage optimum planning and design method for an MCMG is presented in the planning horizon. The investment and operation (fuel and maintenance) costs are considered concurrently to find the optimal type and size of components over the planning horizon. At the first stage, the genetic algorithm (GA) is applied to determine the optimal type and size of components, such as combined heat and power (CHP), boiler, transformer, and solar panels. At the second stage, the mixed-integer nonlinear programming (MINLP) technique is used and simulated by the GAMS software to solve the operational problem with regard to the forecasted energy demands. This method is examined on a typical MCMG and the effectiveness of the proposed method is proven.

A State of Art Review on Offshore Wind Power Transmission Using Low Frequency AC System

Abstract: Offshore wind power generation, transmission and integration around the world are becoming higher, and it provides technical and economic challenges for future practitioners and industries to make an alternative transmission system to an existing system in reduction of cost. In most of countries, e.g. The German government planned to install 25000MW of offshore wind farms by 2030. The greater part of offshore wind farms are integrated with High Voltage AC (HVAC) transmission to the onshore grid. Offshore wind farms are integrated with High Voltage DC (HVDC) transmission for long distances (>50km) to the grid because of capacitive cable current in HVAC. The major challenge in HVDC transmission is the installation, operation and maintenance (O&M) of the Voltage Sourced Converter (VSC) HVDC substation in the offshore climate. Currently, in case offshore wind farm the research have been fastened to reduce the complexity with increasing reliability and minimizing cost. This paper gives a comprehensive review of integration of offshore wind farm via Low Frequency AC or Fractional Frequency AC (LFAC or FFAC) transmission. LFAC transmission is adopted from HVAC and it is operated at one third of nominal frequency (16.67 Hz). As compared to HVDC the main advantage of LFAC is an absence of the offshore converter station, hence system complexity and cost reduced. In design considerations, especially the offshore transformer is one of the challenges. This paper presents a comprehensive review on components and its design considerations of offshore novel LFAC transmission. The offshore wind turbine considerations, collector network and different types of onshore frequency converters explained in detail.

Performance Analysis of Grid connected PV/Wind Hybrid Power System during Variations of Environmental Conditions and Load

Abstract: This survey investigates a dynamic modeling, simulation and control of Photovoltaic (PV)-wind hybrid system connected to electrical grid, considering changes of environmental conditions. In addition, the daily variations of critical load power are considered. The studied hybrid system consists of two Photovoltaic (PV) stations placed at different locations and one wind farm are integrated into main AC bus to enhance the system effectiveness. The PV/wind hybrid system feeds large plant with critical variable loads and electrical utility grid. The technique of extracting maximum power point is applied for both photovoltaic stations and wind farm to capture maximum power under varying climatic conditions. Modeling and simulation of the studied hybrid system is performed using matlab-Simulink software. The reliability of the studied hybrid system is analyzed under various operating conditions such as changes of solar irradiation and wind speed. Control strategy for power flow is proposed to supply critical load demand of plant. The simulation results show that when the injected power from hybrid system is larger than critical load power, the excess power will be injected to electrical grid. Otherwise, when injected power is lower than critical power demand, electrical utility grid in cooperated with hybrid power system will supply the critical load power. In addition, when the injected power from hybrid system is unavailable, load demand is entirely fed by electrical utility.

Numerical Analysis of Different Blade Shapes of a Savonius Style Vertical Axis Wind Turbine

Abstract: The objective of this present numerical work is to evaluate and compare the performance of the proposed outer overlap Bach type rotor with conventional simple Savonius rotor and modified Bach type rotor In order to improve the performance of the modified Bach type rotor at low wind speed regimes, the outer overlap Bach rotor is proposed Modeling and discretization of the computational domain with mesh is carried out using GAMBIT 24 and the analysis is performed using ANSYS FLUENT 145 SST k-I‰ turbulence model is used to achieve the closure for the governing equations All the different blade shapes of the rotors are tested at same free stream conditions and the performance characteristics curves are plotted along with contours to visualize the flow physics over the rotor The proposed outer overlap Bach type rotor showed an improved performance by 15% in terms of coefficient of power over the existing modified Bach type rotor A C p(max) of about 048 is obtained at a tip speed ratio of 060 by the proposed outer overlap Bach rotor

Effect of Alkalis pretreatment on Lignocellulosic Waste Biomass for Biogas Production

Abstract: Converting lignocellulosic waste biomass into biogas is a multi-step process; the rate limiting reaction is lignin removal The objective of the current study was to evaluate alkali treatment for lignin removal and potential of biogas yield of pretreated waste biomass compare to untreated one Three alkali reagents at various dosages: NaOH (1,2,3, and 5%), KOH (1,2,3, and 5%), and Ca(OH) 2 (05%) were tested at three different heating processes, water bath, autoclave and short time microwave NaOH with short time microwave heating process had the highest delignification of 70-86% compare to other alkalies and heating processes However, an opposite effect of high alkali dosage was observed on holocellulose The highest cumulative biogas of 560 mL/gVS was obtained from 2% NaOH pretreated wheat straw, which was 2-times higher than the cumulative biogas produced from the same untreated substrates In the present study 2% NaOH alkali and microwave heating is determined optimum for lignin removal from waste biomass and enhancement in biogas production Keywords Anaerobic digestion; alkaline pre-treatment; biogas; delignification; lignocellulosic waste

Designing and Optimization of Stand-alone Hybrid Renewable Energy System for Rural Areas of Punjab, Pakistan

Abstract: Increasing energy demand accompanied by diminishing of natural resources is the prime reason behind the growing popularity of renewable energy resources. Hence to develop a power system model for sustainable and efficient power deliverance is inevitable. To serve the purpose, we proposed in this paper a hybrid renewable energy system (HRES) that consists of run-off canal micro hydro/PV/wind integrated with a diesel generator. Main purpose is the electrification of remote areas of province Punjab, Pakistan. The authors selected the BS link canal-I located at 300 52’ N and 730 55’ E in Punjab, Pakistan, for the proposed HRES. Beforehand, load and resource profile of selected site was evaluated to present an economically optimized model of the proposed energy system. Moreover, Hybrid Optimization Model for Electric Renewables (HOMER) was used as an optimization tool to perform techno-economic feasibility of the micro hydro/PV/wind energy system to entertain the evaluated load of the location. Mainly three strategies are employed due to scarcity of hydro resources and based on the availability of the energy resources. First strategy suggests to use diesel generator integrated with solar and wind power systems, HOMER declares this strategy most expensive with total Net Present Cost (NPC) of $ 670,121 and Cost of Energy (COE) of $ 0.0936/kWh. The recovery period of the hybrid energy system under this strategy is 13 years. The second strategy focuses on the water management strategy using 100 % renewable energy. NPC diminishes to $ 479,835 and the COE reduces to $ 0.0670/kWh. The system recovers all the incurred cost in 5.5 years. The last one enacts renewable energy systems with capacity shortage scheme. NPC and the COE reduces to $ 284,877 and $ 0.0437/kWh respectively from the previously discussed strategy. The system recovers all the incurred cost in 1.7 years. Based on the NPC, the COE and the minimum payback period, HOMER executes the optimization analysis on all the proposed strategies and found 1 st strategy to be the least feasible and 3 rd strategy the most feasible respectively.