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Turbine performance and wind energy potential using probability distribution in Africa
Abstract
The energy requirement in the world is increasing day by day. The non-renewable energy production is one of the reasons for climate change. The present study explores the selection of possible locations to establish a wind power plant in Ethiopia. The possible locations from Ethiopia that were considered in this study are Weraelu, Enewari and Mekdela. The wind speed characterization, wind direction and wind power densities were analyzed at Waraelu, Enewari and Mekdela. The results of this study reveals that Enewari is the best suitable place to establish the wind power plants among Waraelu, Enewari and Mekdela. In Enewari site the maximum wind speed at 10m height is 6.11 m/s. 75% of wind direction at Enewari site is from North to North West and North to North East. Weibull distribution analysis was incorporated to find average wind speed and probability density among five years of wind speed data. The average wind speed and probability density over five years of Enewari site is 5 m/s and 18.5%. The wind power densities were determined by Weibull method and the maximum wind power obtained from Enewari site is 495.33 w/m^2.
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Among renewable sources of energy, wind is the most widely used resource due to its commercial acceptance, low cost and ease of operation and maintenance, relatively much less time for its realization from concept till operation, creation of new jobs, and least adverse effect on the environment. The fast technological development in the wind industry and availability of multi megawatt sized horizontal axis wind turbines has further led the promotion of wind power utilization globally. It is a well-known fact that the wind speed increases with height and hence the energy output. However, one cannot go above a certain height due to structural and other issues. Hence other attempts need to be made to increase the efficiency of the wind turbines, maintaining the hub heights to acceptable and controllable limits. The efficiency of the wind turbines or the energy output can be increased by reducing the cut-in-speed and/or the rated-speed by modifying and redesigning the blades. The problem is tackled by identifying the optimization parameters such as annual energy yield, power coefficient, energy cost, blade mass, and blade design constraints such as physical, geometric, and aerodynamic. The present paper provides an overview of the commonly used models, techniques, tools and experimental approaches applied to increase the efficiency of the wind turbines. In the present review work, particular emphasis is made on approaches used to design wind turbine blades both experimental and numerical, methodologies used to study the performance of wind turbines both experimentally and analytically, active and passive techniques used to enhance the power output from wind turbines, reduction in cut-in-speed for improved wind turbine performance, and lastly the research and development work related to new and efficient materials for the wind turbines.
The present study deals with wind energy analysis and the selection of an optimum type of wind turbine in terms of the feasibility of installing wind power system at three locations in South Korea: Deokjeok-do, Baengnyeong-do and Seo-San. The wind data measurements were conducted during 2005–2015 at Deokjeok-do, 2001–2016 at Baengnyeong-do and 1997–2016 at Seo-San. In the first part of this paper wind conditions, like mean wind speed, wind rose diagrams and Weibull shape and scale parameters are presented, so that the wind potential of all the locations could be assessed. It was found that the prevailing wind directions at all locations was either southeast or southwest in which the latter one being more dominant. After analyzing the wind conditions, 50-year and 1-year extreme wind speeds (EWS) were estimated using the graphical method of Gumbel distribution. Finally, according to the wind conditions at each site and international electro-technical commission (IEC) guidelines, a set of five different wind turbines best suited for each location were shortlisted. Each wind turbine was evaluated on the basis of technical parameters like monthly energy production, annual energy production (AEP) and capacity factors (CF). Similarly, economical parameters including net present value (NPV), internal rate of return (IRR), payback period (PBP) and levelized cost of electricity (LCOE) were considered. The analysis shows that a Doosan model WinDS134/3000 wind turbine is the most suitable for Deokjeok-do and Baengnyeong-do, whereas a Hanjin model HJWT 87/2000 is the most suitable wind turbine for Seo-San. Economic sensitivity analysis is also included and discussed in detail to analyze the impact on economics of wind power by varying turbine’s hub height.
The operation of modern horizontal axis wind turbine (HAWT) includes a number of important factors, such as wind power (P), power coefficient (CP), axial flow induction factor (a), rotational speed (Ω), tip speed ratio (λ), and thrust force (T). The aerodynamic qualities of these aspects are evaluated and discussed in this study. For this aim, the measured data are obtained from the Sebenoba Wind Energy Power Plant (WEPP) which is located in the Sebenoba region in Hatay, Turkey, and a wind turbine with a capacity of 2 MW is selected for evaluation. According to the results obtained, the maximum turbine power output, maximum power coefficient, maximum axial flow induction factor, maximum thrust force, optimum rotational speed, probability density of optimum rotational speed and optimum tip speed ratio are found to be 2 MW, 30%, 0.091, 140 kN, 16.11 rpm, 46.76 % and 7, respectively. This study has revealed that wind turbines must work under optimum conditions in order to extract as much energy as possible for approaching the ideal limit.
In this study, a horizontal-axis wind turbine (HAWT) blade with 10,000 Watt power output has been designed by the blade element momentum (BEM) theory and the modified stall model, and the blade aerodynamics are also simulated to investigate its flow structures and aerodynamic characteristics. The design conditions of the turbine blade in order to display the linear distributions of pitch angle in each section include the rated wind speed, design tip speed ratio and design angle of attack that have been set to 10 m/s, 6 and 6°, respectively. The turbine blade geometry was laid out using S822 airfoils and the blade aspect ratio is 8.02 divided into radius of 3 m and chord length of 0.374 m. Next, the improved BEM theory including Viterna- Corrigan stall model, tip-loss factor and stall delay model has been developed for predicting the performance of the designed turbine blade. Finally, the investigations of aerodynamic characteristics for the turbine blade were performed by the numerical simulation. The Reynolds averaged Navier-Stokes (RANS) equatios combined with the Spalart-Allmaras turbulence model that describes the three dimensional steady state flow on the wind turbine blade were solved with the aid of a commerical Computational Fluid Dynamic (CFD) code. A structured grid of approximately 2.4 million cells formulates the computational domain. The simulation results are compared with the improvd BEM theory at rated wind speed of 10 m/s and show that the CFD is a good method on aerodynamic invesigation of a HAWT blade.
The energy assurance and electricity supply are significant factors for progress and development of all countries. Low investment costs, reducing greenhouse emission, and high output efficiency for good performance of power plants are key factors in evaluating energy parameters for governments. This study is intended on determining and proving the compatibility of existing power plants in the country of Iran by applying observational data through the application of Multi-Criteria Decision-Making Analysis (MCDA). The obtained compromise solutions applied through a MATLAB code that helped in specifying which power plants are particularly suitable for establishment in the future work. Furthermore, it supports the generalization and validation of applying VIKOR method for thorough evaluation of power systems by comparing the results with real condition. The different types of power plants have been considered as alternatives. Multi-criteria evaluations of these diverse power plants were also carried out with respect to the environmental, technological, and economic criteria. It was concluded that hydropower plant is the best possible case for establishment, and the VIKOR method is a reliable technique for evaluating energy systems which can help to rank alternatives and determines the solution named compromise that is the closest to the ideal case.
Wind energy resource assessments at two locations in Kiribati are carried out. The wind resource on the main
atoll of Tarawa is analysed along with a nearby atoll Abaiang. Measurements of wind speed, direction, ambient
temperature and pressure were performed and analysed. The Tarawa site has an average wind speed of 5.355 m/s at 34 m above ground level (AGL) and the Abaiang site has an average wind speed of 5.4575 m/s at 34 m AGL. The wind direction for both the sites is predominantly East-North-East. Average diurnal wind shear coefficient correlated well with the variation in temperature. The overall average turbulence intensity was about 10% at 34 m and about 13% at 20 m AGL for both the sites. The Weibull parameters were obtained for both the sites using seven methods and the most accurate method, which was found to be the Moments method, was used to find the Weibull parameters and the wind power density. The Weibull parameters were also obtained for the two seasons of Kiribati – the dry and the wet seasons. A high resolution wind resource map of both the sites is obtained using Wind Atlas Analysis and Application Program (WAsP). The WAsP analysis indicates reasonably good wind power development potential for the Tarawa and Abaiang atolls. Annual energy production with five Vergnet 275 kW turbines for both the locations is estimated and an economic analysis is performed, which showed a payback period of 5.42 years to 8.74 years.
Rated wind speed is recognized as one of the key design factors affecting the overall power production of a wind turbine. No formulation is found in literature to relate the rated wind speed to the wind turbine power curves and the annual energy production (AEP). This paper aims to formulate the suitable rated wind speed for variable speed wind turbines continuously operating at maximum power coefficient for maximizing AEP. A capacity value is introduced which relates AEP to an integral function of the rated wind speed using Weibull distribution of wind speeds and the constant power coefficient of variable speed wind turbines. The capacity values are calculated and presented versus rated wind speeds at different wind classes and Weibull parameters. From the results, the suitable values for the rated wind speeds for maximizing AEP are found which are considerably higher than normally used values and varied from 2 to 5 times of the annual mean wind speed. For instance, for the mean annual wind speed of 4 m/s and the shape factors of k = 1.2, 1.6, 2.0, 2.4, 2.8, 3.2, and 3.6, the converged rated wind speeds are V rate = 20, 19, 14, 12, 10, 10, and 9 m/s, respectively. On this basis, new charts for rated wind speeds are introduced for selecting suitable wind turbines for maximizing AEP. It is concluded that for some selected wind turbines operating at lower rated wind speeds, the AEP may fall below about 43% of actual achievable AEP when employing higher recommended rated wind speeds. Hence, it is shown that selecting the right rated wind speed wind turbines has great impact on overall energy production of a wind site.
This paper presents a multi-criteria selection approach for offshore wind sites assessment. The proposed site selection framework takes into consideration the electricity network’s operating security aspects, economic investment, operation costs and capacity performances relative to each potential site. The selection decision is made through Analytic Hierarchy Process (AHP), with an inherited flexibility that aims to allow end users to adjust the expected benefits accordingly to their respective and global priorities. The proposed site selection framework is implemented as an interactive case study for three Baltic States in the 2020 time horizon, based on real data and exhaustive power network models, taking into consideration the foreseen upgrades and network reinforcements. For each country the optimal offshore wind sites are assessed under multiple weight contribution scenarios, reflecting the characteristics of market design, regulatory aspects or renewable integration targets.
In this paper, we propose a novel technique to determine the optimal placement of wind farms, thereby taking into account wind characteristics and electrical grid constraints. We model the long-term variability of wind speed using a Weibull distribution according to wind direction intervals, and formulate the metrics that capture wind speed characteristics at a specific location, namely the arithmetic mean of wind speed, the theoretical wind power density and the capacity factor of a prospective wind power plant, to determine the feasibility of a wind power plant establishment. Furthermore, a linear optimization formulation is provided to determine the geographical locations and the installed capacities of wind farms, in order to maximize the expected annual wind power generation, while obeying the constraints from the electrical power grid and the transmission system operator. As a case study, the proposed wind speed model and the linear optimization formulation are used to evaluate the wind characteristics and the potential wind farm sites in Turkey.
