scholarly journals Optimum Solidity on Downwind Thai Sail Windmill

2021 ◽  
Vol 18 (22) ◽  
pp. 42
Author(s):  
Teerawat Klabklay ◽  
Wikanda Sridech
Keyword(s):  
Wind Turbines ◽  
Maximum Efficiency ◽  
Horizontal Axis Wind Turbine ◽  
Testing Method ◽  
Wide Range ◽  
Blade Area ◽  
Low Efficiency ◽  
Enhance Efficiency ◽  
Swept Area ◽  
Cord Length

Solidity was a significant parameter affecting the efficiency of wind turbines. It is defined as the ratio between the projected area of all blades and the swept area of the rotor. The solidity could be improved by modifying the shape, cord length, or the number of blades. Research studies mentioned that higher solidity seemed to provide more power due to more blade area. However, it can be argued that if the solidity was too high, it would cause the airflow to be more obstructed and disrupted, causing the gained power to drop down instead. Thus, the optimum solidity, which made the wind turbines maximum effective, must be existent in itself and must be in the range between 0 - 100 %. Thai sail windmill is a kind of horizontal axis wind turbine currently used to pump seawater in salt farms in Thailand, where the general solidity is in the quite wide range of about 15 - 60 %. Mostly, the Thai sail windmill was designed by a rule of thumb. Hence, it has quite a low efficiency, which is only about 10 %. This study aims to investigate the optimum solidity of Thai sail windmill in the downwind type to enhance efficiency. The 4-blade and 6-blade rotors of 1-m radii were used as the prototypes for experiments using the tow testing method. The results showed that the optimum solidity of 4-blade and 6-blade rotors was 28 %, respectively, whereby the maximum efficiency of the 2 rotors was 17 and 25 %.

Aerodynamic Performance of a Small Horizontal Axis Wind Turbine

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
Maryam Refan ◽  
Horia Hangan
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
High Speed ◽  
Aerodynamic Performance ◽  
Horizontal Axis ◽  
Power Prediction ◽  
Horizontal Axis Wind Turbine ◽  
Wind Speeds ◽  
Wide Range ◽  
Bem Theory

The aerodynamic performance of an upwind, three-bladed, small horizontal axis wind turbine (HAWT) rotor of 2.2 m in diameter was investigated experimentally and theoretically in order to assess the applicability of the blade element momentum (BEM) theory for modeling the rotor performance for the case of small HAWTs. The wind turbine has been tested in the low and high speed sections of the Boundary Layer Wind Tunnel 2 (BLWT2) at the University of Western Ontario (UWO) in order to determine the power curve over a wide range of wind speeds. Afterward, the BEM theory has been implemented to evaluate the rotor performance and to investigate three-dimensionality effects on power prediction by the theory. Comparison between the theoretical and experimental results shows that the overall prediction of the theory is within an acceptable range of accuracy. However, the BEM theory prediction for the case of small wind turbines is not as accurate as the prediction for larger wind turbines.

scholarly journals Efficient Direct-Drive Small-Scale Low-Speed Wind Turbine

2014 ◽  
Vol 1 (1-2) ◽  
Author(s):  
Ravi Anant Kishore ◽  
Anthony Marin ◽  
Shashank Priya
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Electrical Power ◽  
Ground Level ◽  
Maximum Efficiency ◽  
Small Scale ◽  
Portable Devices ◽  
Direct Drive ◽  
Horizontal Axis Wind Turbine ◽  
Wide Range

AbstractThere is growing need for the green, reliable, and cost-effective power solution for the expanding wireless microelectronic devices. In many scenarios, these needs can be met through a small-scale wind energy portable turbine (SWEPT) that operates near ground level where wind speed is of the order of few meters per second. SWEPT is a three-bladed, 40 cm rotor diameter, direct-drive, horizontal-axis wind turbine that has very low cut-in wind speed of 1.7 m/s. It operates in a wide range of wind speeds between 1.7 m/s and 10 m/s and produces rated power output of 1 W at wind speed of 4.0 m/s. The wind turbine is capable of producing electrical power up to 9.8 W at wind speed of 10 m/s. The maximum efficiency of SWEPT was found to be around 21% which makes it one of the most efficient wind turbines reported at the small scale and low wind speed. These advancements open many new opportunities for embedding and utilizing wireless and portable devices.

Automatic Identification of Closed-Loop Wind Turbine Dynamics via Genetic Programming

2015 ◽  
Author(s):  
William La Cava ◽  
Kourosh Danai ◽  
Matthew Lackner ◽  
Lee Spector ◽  
Paul Fleming ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Dynamic Models ◽  
A Priori ◽  
Operating Conditions ◽  
Automatic Identification ◽  
Horizontal Axis Wind Turbine ◽  
Symbolic Form ◽  
Turbulent Environments ◽  
Wide Range

Wind turbines are nonlinear systems that operate in turbulent environments. As such, their behavior is difficult to characterize accurately across a wide range of operating conditions by physically meaningful models. Customarily, data-based models of wind turbines are defined in ‘black box’ format, lacking in both conciseness and physical intelligibility. To address this deficiency, we identify models of a modern horizontal-axis wind turbine in symbolic form using a recently developed symbolic regression method. The method used relies on evolutionary multi-objective optimization to produce succinct dynamic models from operational data without ‘a priori’ knowledge of the system. We compare the produced models with models derived by other methods for their estimation capacity and evaluate the tradeoff between model intelligibility and accuracy. Several succinct models are found that predict wind turbine behavior as well as or better than more complex alternatives derived by other methods.

Study on the Modes of Operation of a Multi-Machine Installations with Mechanical Reduction

2019 ◽  
pp. 12-22
Author(s):  
A. M. Oleynikov ◽  
L. N. Kanov
Keyword(s):  
Mathematical Description ◽  
Reactive Power ◽  
Maximum Efficiency ◽  
Wind Flow ◽  
System Of Equations ◽  
Mechanical Equilibrium ◽  
Synchronous Generators ◽  
Electromagnetic Excitation ◽  
Number Of Generators ◽  
Wide Range

The paper gives the description of the original wind electrical installation with mechanical reduction in which the output of vertical axis wind turbine with rather low rotation speed over multiplicator is distributed to a certain number of generators. The number of acting generators is determined by the output of actual operating wind stream at each moment. According to this constructive scheme, it is possible to provide effective and with maximum efficiency installation work in a wide range of wind speeds and under any schedule issued to the consumer of electricity. As there are no any experience in using such complexes, mathematical description of its main elements is given, namely windwheels, generators with electromagnetic excitation of magnetic electrical type, then their interaction with windwheel, and also the results of mathematical modeling of work system regimes under using the offered system of equations. The basis for the mathematical description of the main elements of the installation – synchronous generators – are the system of equations of electrical and mechanical equilibrium in relative units in rotating coordinates without considering saturation of the magnetic circuit. The equation of mechanical equilibrium systems includes torque and brake windwheel electromagnetic moments of generators with taking into account the reduction coefficients and friction. In addition, we specify the alternator rotor dynamics resulting from continuous torque of windwheel fluctuations under the influence of unsteady wind flow and wind speed serving as the original variable is modeled by a set of sinusoids. Model simplification is achieved by equivalization of similar generators and by disregarding these transitions with a small time constant. Calculation the installation with synchronous generators of two types of small and medium capacity taking into account the operational factors allowed us to demonstrate the logic of interactions in the main elements of the reported complex in the process of converting wind flow into the generated active and reactive power. We have shown the possibility of stable system work under changeable wind stream condition by regulating of the plant blade angle and with simultaneous varying of generator number of different types. All these are in great interest for project organizations and power producers.

scholarly journals Hybrid ZnO/MoS2 Core/Sheath Heterostructures for Photoelectrochemical Water Splitting

Applied Nano ◽  
2021 ◽  
Vol 2 (3) ◽  
pp. 148-161
Author(s):  
Katerina Govatsi ◽  
Aspasia Antonelou ◽  
Labrini Sygellou ◽  
Stylianos G. Neophytides ◽  
Spyros N. Yannopoulos
Keyword(s):  
Visible Light ◽  
Wide Band ◽  
Nanowire Arrays ◽  
Maximum Efficiency ◽  
Light Illumination ◽  
Wide Band Gap ◽  
Long Term Stability ◽  
Visible Light Illumination ◽  
Nanowire Surface ◽  
Wide Range

The rational synthesis of semiconducting materials with enhanced photoelectrocatalytic efficiency under visible light illumination is a long-standing issue. ZnO has been systematically explored in this field, as it offers the feasibility to grow a wide range of nanocrystal morphology; however, its wide band gap precludes visible light absorption. We report on a novel method for the controlled growth of semiconductor heterostructures and, in particular, core/sheath ZnO/MoS2 nanowire arrays and the evaluation of their photoelectrochemical efficiency in oxygen evolution reaction. ZnO nanowire arrays, with a narrow distribution of nanowire diameters, were grown on FTO substrates by chemical bath deposition. Layers of Mo metal at various thicknesses were sputtered on the nanowire surface, and the Mo layers were sulfurized at low temperature, providing in a controlled way few layers of MoS2, in the range from one to three monolayers. The heterostructures were characterized by electron microscopy (SEM, TEM) and spectroscopy (XPS, Raman, PL). The photoelectrochemical properties of the heterostructures were found to depend on the thickness of the pre-deposited Mo film, exhibiting maximum efficiency for moderate values of Mo film thickness. Long-term stability, in relation to similar heterostructures in the literature, has been observed.

Synthesis and characterization of a new series of thiadiazole derivatives as potential anticancer agents

2020 ◽  
Vol 26 (1) ◽  
pp. 6-13 ◽  
Author(s):  
Ulviye Acar Çevik ◽  
Derya Osmaniye ◽  
Serkan Levent ◽  
Begüm Nurpelin Sağlik ◽  
Betül Kaya Çavuşoğlu ◽  
...  
Keyword(s):  
Anticancer Agents ◽  
Biological Activities ◽  
Cancer Cell Line ◽  
Chemotherapeutic Agents ◽  
Anticancer Activities ◽  
Normal Tissues ◽  
H Nmr ◽  
Wide Range ◽  
Thiadiazole Derivatives ◽  
Low Efficiency

AbstractCancer is one of the most common causes of death in the world. Despite the importance of combating cancer in healthcare systems and research centers, toxicity in normal tissues and the low efficiency of anticancer drugs are major problems in chemotherapy. Nowadays the aim of many medical research projects is to discover new safer and more effective anticancer agents. 1,3,4-Thiadiazole compounds are important fragments in medicinal chemistry because of their wide range of biological activities, including anticancer activities. The aim of this study was to determine the capacity of newly synthesized 1,3,4-thiadiazole compounds as chemotherapeutic agents. The structures of the obtained compounds were elucidated using 1H-NMR, 13C-NMR and mass spectrometry. Although the thiadiazole derivatives did not prove to be significantly cytotoxic to the tumour tissue cultures, compound 4i showed activity against the C6 rat brain cancer cell line (IC50 0.097 mM) at the tested concentrations.

An Experimental and Numerical Assessment of Airfoil Polars for Use in Darrieus Wind Turbines: Part 2 — Post-Stall Data Extrapolation Methods

2015 ◽  
Author(s):  
Alessandro Bianchini ◽  
Francesco Balduzzi ◽  
John M. Rainbird ◽  
Joaquim Peiro ◽  
J. Michael R. Graham ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Wind Turbines ◽  
Full Range ◽  
Vertical Axis ◽  
Wind Tunnel Tests ◽  
Numerical Assessment ◽  
Wide Range ◽  
Naca0018 Airfoil ◽  
Lift And Drag ◽  
Data Extrapolation

Accurate post-stall airfoil data extending to a full range of incidences between −180° to +180° is important to the analysis of Darrieus vertical-axis wind turbines (VAWTs) since the blades experience a wide range of angles of attack, particularly at the low tip-speed ratios encountered during startup. Due to the scarcity of existing data extending much past stall, and the difficulties associated with obtaining post-stall data by experimental or numerical means, wide use is made of simple models of post-stall lift and drag coefficients in wind turbine modeling (through, for example, BEM codes). Most of these models assume post-stall performance to be virtually independent of profile shape. In this study, wind tunnel tests were carried out on a standard NACA0018 airfoil and a NACA 0018 conformally transformed to mimic the “virtual camber” effect imparted on a blade in a VAWT with a chord-to-radius ratio c/R of 0.25. Unsteady CFD results were taken for the same airfoils both at stationary angles of attack and at angles of attack resulting from a slow VAWT-like motion in an oncoming flow, the latter to better replicate the transient conditions experienced by VAWT blades. Excellent agreement was obtained between the wind tunnel tests and the CFD computations for both the symmetrical and cambered airfoils. Results for both airfoils also compare favorably to earlier studies of similar profiles. Finally, the suitability of different models for post-stall airfoil performance extrapolation, including those of Viterna-Corrigan, Montgomerie and Kirke, was analyzed and discussed.

Applying Hollow Blades for Small Wind Turbines Operating at High Altitudes

2015 ◽  
Author(s):  
Abolfazl Pourrajabian ◽  
Reza Ebrahimi ◽  
Masoud Mirzaei ◽  
Mehdi Ahmadizadeh ◽  
David Wood
Keyword(s):  
Objective Function ◽  
Output Power ◽  
Wind Turbines ◽  
Speed Ratio ◽  
High Altitudes ◽  
Horizontal Axis Wind Turbine ◽  
Lower Altitude ◽  
Starting Time ◽  
Design Variables ◽  
Small Wind Turbines

Since the air density reduces as the altitude increases, operation of Small Wind Turbines (SWTs) which usually have no pitch mechanism, remains as a challengeable task at high altitudes due largely to the reduction of starting aerodynamic torque. By reducing the blades moment of inertia through the use of hollow blades, the study aims to mitigate that issue and speed up the starting. A three-bladed, 2 m diameter small horizontal axis wind turbine with hollow cross-section was designed for operating at two sites with altitude of 500 and 3,000 m. The design variables consist of distribution of the chord, twist and shell thickness along the blade. The blade-element momentum theory was employed to calculate the output power and starting time and, the beam theory was used for the structural analysis to investigate whether the hollow blades could withstand the aerodynamic and centrifugal forces. A combination of the starting time and the output power was included in an objective function and then, the genetic algorithm was used to find a blade for which the output power and the starting performance, the goals of the objective function, are high while the stress limitation, the objective function constraint, is also met. While the resultant stresses remain below the allowable stress, results show that the performance of the hollow blades is far better than the solid ones such that their starting time is shorter than the solid blades by approximately 70%. However, in the presence of the generator resistive torque, the algorithm could not find the blade for the altitude near to 3000 m. To solve that problem, the tip speed ratio of the turbine was added to other design variables and another optimization process was done which led to the optimal blades not only for the lower altitude but also for the higher one.

Gain-phase margins-based delay-dependent stability analysis of pitch control system of large wind turbines

2019 ◽  
Vol 41 (13) ◽  
pp. 3626-3636 ◽  
Author(s):  
Omer Turksoy ◽  
Saffet Ayasun ◽  
Yakup Hames ◽  
Sahin Sonmez
Keyword(s):  
Control System ◽  
Stability Analysis ◽  
Wind Turbines ◽  
Time Domain ◽  
Dynamic Performance ◽  
Pitch Control ◽  
Wide Range ◽  
Delay Dependent ◽  
Delay Dependent Stability ◽  
Large Wind

This paper investigates the effect of gain and phase margins (GPMs) on the delay-dependent stability analysis of the pitch control system (PCS) of large wind turbines (LWTs) with time delays. A frequency-domain based exact method that takes into account both GPMs is utilized to determine stability delay margins in terms of system and controller parameters. A gain-phase margin tester (GPMT) is introduced to the PCS to take into GPMs in delay margin computation. For a wide range of proportional–integral controller gains, time delay values at which the PCS is both stable and have desired stability margin measured by GPMs are computed. The accuracy of stability delay margins is verified by an independent algorithm, Quasi-Polynomial Mapping Based Rootfinder (QPmR) and time-domain simulations. The time-domain simulation studies also indicate that delay margins must be determined considering GPMs to have a better dynamic performance in term of fast damping of oscillations, less overshoot and settling time.

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