On the free yaw behaviour of horizontal axis wind turbines

Experimental and numerical investigation of the effect of turbulent inflow on a Horizontal Axis Wind Turbine (part II: Wake characteristics)

Investigation of fatigue life for a medium scale composite wind turbine blade

The effective exploitation of renewable energy sources is one of the most effective solutions to counter the energy, environmental and economic problems associated with the use of fossil fuels. Small-scale wind turbines (converting wind energy into electric energy with a power output lower than 50 kW) have received tremendous attention over the past few decades thanks to their reduced environmental impact, high efficiency, low maintenance cost, high reliability, wide wind operation range, self-starting capability at low wind speed, limited installation space, reduced dependence on grid-connected power and long transmission lines, low capital costs, as well as the possibility to be installed in some urban settings. However, there are significant challenges and drawbacks associated with this technology from many different perspectives, including the significant discrepancy between theoretical performance data provided by the manufacturers and real field operation, that need to be investigated in greater depth in order to enable a more widespread deployment of small-scale wind turbines. In this review, a complete and updated list of more than 200 commercially available small-scale horizontal and vertical wind turbine models is provided and analysed, detailing the corresponding characteristics in terms of the number and material of blades, start-up wind speed, cut-in wind speed, cut-out wind speed, survival wind speed, maximum power, noise level, rotor diameter, turbine length, tower height, and specific capital cost. In addition, several scientific papers focusing on the experimental assessment of field performance of commercially available small-scale horizontal and vertical wind turbines have been reviewed and the corresponding measured data have been compared with the rated performance derived from the manufacturers’ datasheets in order to underline the discrepancies. This review represents an opportunity for the scientific community to have a clear and up-to-date picture of small-scale horizontal as well as vertical wind turbines on the market today, with a precise summary of their geometric, performance, and economic characteristics, which can enable a more accurate and informed choice of the wind turbine to be used depending on the application. It also describes the differences between theoretical and in-situ performance, emphasizing the need for further experimental research and highlighting the direction in which future studies should be directed for more efficient design and use of building-integrated small-scale wind turbines.

Renewable energy is expected to grow in importance over the next few decades, with renewable energy being the primary source of energy. As a result, some wind energy research tends to focus on increasing turbine efficiency by changing the blade design to improve its overall efficiency. Albatross and Stork are migrating birds known for their effortless flight and dynamic soaring that enables them to fly over the open sea for weeks during migration without flapping their wings at low wind velocity. In this paper, the design and aerodynamic performance of Horizontal Axis Wind Turbines (HAWTs) with airfoils inspired by migrating birds (Albatross and Stork) for low wind velocity applications will be presented using CFD multiphysics software - ANSYS Fluent. The proposed wind turbines were analyzed in a wide range of angular velocities at a wind velocity of 5 m/s. The Albatross HAWT produced a power output of 1.71 W, 6.66 W, 17.28 W, 22.68 W, 22.95 W, 21.24 W, 17.85 W at 10 rad/s, 20 rad/s, 30 rad/s, 40 rad/s, 50 rad/s, 60 rad/s, and 70 rad/s, respectively. The Stork HAWT produced a power output of 1.20 W, 4.80 W, 10.26 W, 19.80 W, 21 W, 18 W, and 11.13 W at 10 rad/s, 20 rad/s, 30 rad/s, 40 rad/s, 50 rad/s, 60 rad/s, and 70 rad/s, respectively. The results showed that the optimum power coefficient for Albatross and Stork HAWT was achieved at 40–50 rad/s with values ranging from 0.440-0.445 and 0.384-0.407, respectively. Modern large wind turbines can achieve up to 50% efficiency; this study showed that Albatross and Stork blades could be a viable design for a modern wind turbine as they attain an efficiency close to 50%, considering that the proposed design was carried out on a micro-scale.

This article explores the integration of artificial intelligence (AI) applications into project‐based learning (PBL) education as a means to enhance students' education. Specifically, the implementation of AI in the context of power generation is addressed, focusing on achieving power generation at minimum wind velocity and classifying turbine faults using AI techniques. The researchers have proposed a novel generating unit which is going to generate 1 KW of electric power at a specific flow rate of air and the generated power will be stored in the battery bank through the charge controller and then the load is driven from the battery through an inverter. Iron or core losses (Hysteresis, Eddy Current losses) can be acknowledged as one of the major reasons for the inefficiency of conventional generators, therefore anovel coreless model generator was proposed which also improved efficiency and reduces drag. Wind Turbine prototype was fabricated and deployed for the testing and validation of the proposed novel design. The design produced outstanding power ratings and electrical generation characteristics compared with other existing strategies at minimal air flow. Results proved that the proposed coreless axial flux generator has the capability to produce a better power rating compared with the existing wind turbine generators. Proposed Axial flux achieved 10.73 watt power at wind velocity at around 80 rpm. At a wind velocity of 10 m/s and around 800 rpm 313–330 kwh was produced by the proposed generator while the conventional generator produced around 300 kwh. The proposed generator design performed 35% better in terms of production efficiency under load and no load conditions. Moreover, faults in turbines are very common due to the various temperatures, therefore the faults have been classified using state‐of‐the‐art AI‐based classifiers. A comparison of space vector modulation (SVM) and Naive Bayes classifiers was performed in the study to classify wind turbine faults. It was found that both classifiers performed well in achieving high accuracy. SVM achieved a slightly higher accuracy of 0.9861 compared with Naive Bayes, which achieved an accuracy of 0.967. Based on the results, it can be inferred that SVM may be a more suitable classifier for wind turbine fault classification. The case study results demonstrated the potential of AI applications in PBL education, offering students a multidisciplinary learning experience that enhances their technical knowledge, problem‐solving skills, and teamwork abilities.

Design and analysis of 5 MW horizontal axis wind turbine

This paper proposes a novel machine parameter independent control algorithm that enables wind turbines to quickly and effectively extract maximum power from the wind turbine under changing atmospheric conditions. The energy captured by a wind turbine varies due to variations in wind velocity, air density (influenced by temperature and humidity), turbine aerodynamics, and generator dynamics. Without power electronics and power extraction control techniques, wind systems have low power extraction efficiency. Given that the power from the wind turbine is dependent on generator rotor speed, the proposed algorithm indirectly uses the tip speed ratio (TSR) to assist in the maximum power point search (MPPS). The slope (or indirect TSR) assisted MPPS provides historic system state information and preempts misguided control decisions due to deceptive power readings caused by atmospheric changes. In this paper, the wind energy system, algorithm design framework, performance, and real-time wind speed data is presented.

Offshore wind turbines are subjected to combined static and cyclic loads due to its self weight, wind, current and waves. For the design of support structures, a point of concern is whether the highly varying loads may cause cyclic degradation of the soil leading to a permanent undesired pile settlement and tilting for the wind turbine. In particular during a severe storm, the large cyclic loads are being more critical as the wind and waves are typically from a single direction. The DTU 10MW wind turbine supported by a jacket at 33 m water depth is considered in this study, where the piles are axially loaded in order to bear the moment under wind and wave actions. This paper investigates the cyclic loads using traditional linear irregular waves and fully nonlinear irregular waves realized from the wave solver Ocean-Wave3D previously validated until near-breaking wave conditions. This study shows that the nonlinear irregular waves introduce more extreme cyclic loads, which result in significantly larger pile settlement than using linear wave realizations. For the case in this study, linear wave theory underestimates pile settlement at least 30% compared to nonlinear wave realizations.

The first part of the present study investigated the relationship among the number of yaw gear and motor failures and turbulence intensity (TI) at all the wind turbines under investigation with the use of in situ data. The investigation revealed that wind turbine #7 (T7), which experienced a large number of failures, was affected by terrain-induced turbulence with TI that exceeded the TI presumed for the wind turbine design class to which T7 belongs. Subsequently, a computational fluid dynamics (CFD) simulation was performed to examine if the abovementioned observed wind flow characteristics could be successfully simulated. The CFD software package that was used in the present study was RIAM-COMPACT, which was developed by the first author of the present paper. RIAM-COMPACT is a nonlinear, unsteady wind prediction model that uses large-eddy simulation (LES) for the turbulence model. RIAM-COMPACT is capable of simulating flow collision, separation, and reattachment and also various unsteady turbulence–eddy phenomena that are caused by flow collision, separation, and reattachment. A close examination of computer animations of the streamwise (x) wind velocity revealed the following findings: As we predicted, wind flow that was separated from a micro-topographical feature (micro-scale terrain undulations) upstream of T7 generated large vortices. These vortices were shed downstream in a nearly periodic manner, which in turn generated terrain-induced turbulence, affecting T7 directly. Finally, the temporal change of the streamwise (x) wind velocity (a non-dimensional quantity) at the hub-height of T7 in the period from 600 to 800 in non-dimensional time was re-scaled in such a way that the average value of the streamwise (x) wind velocity for this period was 8.0 m/s, and the results of the analysis of the re-scaled data were discussed. With the re-scaled full-scale streamwise wind velocity (m/s) data (total number of data points: approximately 50,000; time interval: 0.3 s), the time-averaged streamwise (x) wind velocity and TI were evaluated using a common statistical processing procedure adopted for in situ data. Specifically, 10-min moving averaging (number of sample data points: 1932) was performed on the re-scaled data. Comparisons of the evaluated TI values to the TI values from the normal turbulence model in IEC61400-1 Ed.3 (2005) revealed the following: Although the evaluated TI values were not as large as those observed in situ, some of the evaluated TI values exceeded the values for turbulence class A, suggesting that the influence of terrain-induced turbulence on the wind turbine was well simulated.

Monopile foundations for offshore wind turbines are subject to many cycles of large horizontal loads and overturning moments. This paper describes the foundation analysis of a wind turbine foundation typical of 3 to 5 MW units that have already been constructed in the southern North Sea and are being proposed offshore in the northeastern United States. The foundation consists of a 5.1 m diameter monopile driven 26 m below the seafloor into medium dense sand. The environmental loads were highly idealized, represented as a 6 MN vertical force and a 4 MN horizontal force applied 30 m above the seafloor. The effects of one cycle of monotonic loading and up to 107 cycles of long-term cyclic loading were computed. The analyses were performed using a widely available three-dimensional finite element program, incorporating an implicit method to model the soil modulus degradation and increased strain as a function of the number of loading cycles. The computations showed that the monopile displacements and rotations accumulate with additional cycles of loading, almost doubling after 107 cycles. This suggested that a monopile that rotates within tolerances after one cycle of load, approximately 0.25°, may accumulate unacceptably high deflections and rotations over its design life. The paper demonstrated the use of commercially available software as part of a method to model the response of a wind turbine monopile foundation to long-term lateral cyclic loading. Introduction A monopile is a large-diameter, open-ended pipe pile driven into the seafloor, connected to a wind turbine tower by means of a transition piece. The tower supports the turbine nacelle and the rotor. Monopiles must withstand the forces from wind, waves, ice, currents, and vessel impacts over the life of the turbine, which can be up to 50 years. The design of the monopiles must consider the response of the supporting soil to the long-term applied cyclic loadings. As such, an accurate method to calculate the lateral deflection and rotation of the pile due to cyclic loading, including the effects of changes in properties of the supporting soil, is needed. This study is concerned with the effects on offshore wind turbine foundations of high cycle, low amplitude loading that will induce small strains. It is assumed that the cyclic loading has low strain-amplitude, less than 10-3 (Whichtmann et al., 2010), with as many as 107 cycles over the lifetime of the offshore wind turbine (OWT), consistent with the observations by LeBlanc et al. (2010). Monopiles are generally installed in water depths of less than 30 m (Malhotra, 2010). At greater depths, they become excessively large and uneconomical. Critical elements of their design include the loadings and performance requirements or limit states. One of the serviceability limits conditions is that a monopile cannot exceed a permanent rotation typically of 0.5° at the mudline level over its design life (Malhotra, 2010).

The article presents a study conducted to analyze the vulnerable zones of horizontal axis wind turbine (HAWT) wings, the nacelle, and the tower during the rotor revolution. The objective of the study is to establish relations between the extreme values of the investigated variables (wind velocity and pressure, von Mises stresses, displacements, etc. vs. angle of rotation or position of the rotor) in order to explore the vulnerable zone. The numerical model, as a computer-aided design (CAD) model geometry of the turbine assembly, was developed using freeform outline of the blade profile according to a previously designed twisted and tapered blade shape and a simplified outline of the nacelle. The tower was assumed to be made of a pipe and unites pipes of increasing diameter; hence its outline is a conic form. All solid bodies, i.e., blades of fiber glass composite and the tower and nacelle of alloy steel, are meshed using parabolic tetrahedral finite elements. The article demonstrates the used simulation technique and the results that are visualized using diverse graphical tools. Though it is hard to precisely point out the location of the vulnerable zone, the results indicate that the highest stresses appear along the trailing edge when the blade is in vertical direction.

Depleting oil reserves and fossil fuels has changed the aspect of thought in energy sector and led to a strong focus on renewable energy sources. Wind energy sector is a potential area of research as the idea of micro grid and domestic power integration are in place. Wind turbines that can be used to harness the low wind velocities for power generation are of importance. Horizontal Axis Wind Turbines and vertical Axis Wind Turbines are the types of wind turbines used to convert wind energy to electrical energy. Horizontal Axis Wind Turbines provide good wind power conversion efficiency and are used in regions of moderate to high wind speeds and in regions of lower wind speeds, Vertical Axis Wind Turbines performance is satisfactory. In this work, the mathematical modeling of HAWT and different types of VAWTs are presented, followed by analysis of those turbine models under lower air velocities. The performance parameters used in this study are maximum power coefficient and output power which are standard performance metrics for wind power generation. The analysis reinforces the fact that, in domestic conditions, where the wind velocity in low, VAWTs provide superior performance.

An investigation on the performance and viability of a hybrid twisted blade profile for a horizontal axis micro wind turbine

This report presents the study of fluid-structure interaction (FSI) of a 5kW horizontal axis wind turbines (HAWT). The motivation of the current investigation is to address the FSI problem of HAWT in the whole flow field analysis with hybrid turbulence model method which is used to find out the flow and structure characteristics of wind turbine in operation under different tip speed ratio (TSR). The target of current work is to obtain detailed information of flow field and structure response simultaneously using the finite element analysis (FEA) method as well as providing new reliable and accurate approach which could be quickly and economically employed in wind turbine FSI problem analysis. In this report, a detailed and comprehensive literature review related to FSI problem of wind turbine has been presented and includes aerodynamic, wind turbine theory, computational fluid dynamic, fluid structure interaction and aeroelastic stability. A 5kW wind turbine is designed according to blade element momentum (BEM) method and a 3D wind turbine modeling is generated in SolidWorks. The 3D wind turbine modeling is imported into FEA software by coupling with the structure domain and the fluid domain to achieve FSI analysis and different TSR are applied to the computational fluid dynamics (CFD) analysis to gain the wind turbine operation information under different scenarios. The simulation results are investigated to reveal the influence of the FSI phenomenon on wind turbine performance. Analysis of wind turbine aeroelastic stability is conducted to prevent blade from experiencing flutter problem. A multiple objective optimization method for wind turbine design including aerodynamic and structure has been developed to improve wind turbine performance. The flow field analysis results showed that the strength of vortex at the tip and root of the blade increases as wind speed increases when wind turbine is under operating conditions. With wind speed of 10m⁄s, most of the flow over the lower surface remains attached and the wind turbine blade was running under design condition. As the wind speed increases, flow separation emerges. When the wind speed increasing to 16m⁄s, the wind turbine blade works under deep stall condition. The wind turbine power coefficient drops continuously from 0.46 to 0.22, as wind speed increased from 10m⁄s to 20m⁄s. The comparison of wind turbine power and torque coefficient under different CFD configuration shows the advantage of whole flow field analysis with hybrid turbulence model. The structural analysis results demonstrated that most of the pressure force acts at a region around the 1⁄4 chord from the leading edge of the blade under operating condition and the displacement of blade tip in flap direction is bigger than those in the other directions. Modal analysis results deduced that flap is the main type of vibration in first and second modes. The difference of natural frequency between single blade and blade rotor becomes larger as vibration order increases. The dynamic performances of wind turbine blade and rotor are totally different and show the whole flow field method is better than the one third domain method. The wind turbine aeroelastic analysis results illustrate that the bending frequency and torsion frequency are around 23.94Hz and 38.46Hz respectively under TSR=4 and both move towards 30Hz under TSR=1.7. When TSR is smaller than 1.7 the wind turbine will experience flutter due to the overlapping of bending and torsion frequencies. The multiple objectives optimization method takes the aerodynamic performance and blade loading into account to gain better design parameter. The comparison between initial and optimal design shows that optimized method could provide higher electrical energy around 1073kW•h per annum under rated wind speed. The optimized wind turbine critical flutter wind speed will increase from initial design speed of 35m/s to 38m/s under optimization design.

The operation at maximum power in condition of rapid wind velocity modifications poses a challenge for wind power plants. Based on measured data, the authors determine for generator and turbine, the mathematical models. Also, with current measured values for mechanical angular speed, ω, and wind speed, v, the authors determine the mathematical model in a timely manner and, on its basis, compute the optimal mechanical angular speed ωOPTIM, at which the value of the wind turbine power is maximum. We determine the dependence of the optimal / ideal mechanical angular speed, ωOPTIM, to the wind speed, v, and bring the wind turbine into optimal operating area by modification of the generators load. By measuring the wind velocity and monitoring the electric energy flowing from the permanent magnets synchronous generator (PMSG), we compute the wind turbine power. Based on those remarks, to get maximum power out from a wind turbine, it is necessary that between wind velocity and mechanical angular speed should always exist a correlation, according to the wind velocity changes and the inertia moment, J.