Abstract: The present study aims to evaluating the effect of
rotor solidity - in terms of chord length for a given rotor diameter - on
the performances of a small vertical axis Darrieus wind turbine. The
proposed work focuses on both power production and rotor power
coefficient, considering also the structural constraints deriving from
the centrifugal forces due to rotor angular velocity. Also the
smoothness of the resulting power curves have been investigated, in
order to evaluate the controllability of the corresponding rotor
architectures.
Abstract: Wind energy has been shown to be one of the most
viable sources of renewable energy. With current technology, the low
cost of wind energy is competitive with more conventional sources of
energy such as coal. Most blades available for commercial grade
wind turbines incorporate a straight span-wise profile and airfoil
shaped cross sections. These blades are found to be very efficient at
lower wind speeds in comparison to the potential energy that can be
extracted. However as the oncoming wind speed increases the
efficiency of the blades decreases as they approach a stall point. This
paper explores the possibility of increasing the efficiency of the
blades at higher wind speeds while maintaining efficiency at the
lower wind speeds. The design intends to maintain efficiency at
lower wind speeds by selecting the appropriate orientation and size
of the airfoil cross sections based on a low oncoming wind speed and
given constant rotation rate. The blades will be made more efficient
at higher wind speeds by implementing a swept blade profile.
Performance was investigated using the computational fluid
dynamics (CFD).
Abstract: This paper focuses on developing an integrated
reliable and sophisticated model for ultra large wind turbines And to
study the performance and analysis of vector control on large wind
turbines. With the advance of power electronics technology, direct
driven multi-pole radial flux PMSG (Permanent Magnet Synchronous
Generator) has proven to be a good choice for wind turbines
manufacturers. To study the wind energy conversion systems, it is
important to develop a wind turbine simulator that is able to produce
realistic and validated conditions that occur in real ultra MW wind
turbines. Three different packages are used to simulate this model,
namely, Turbsim, FAST and Simulink. Turbsim is a Full field wind
simulator developed by National Renewable Energy Laboratory
(NREL). The wind turbine mechanical parts are modeled by FAST
(Fatigue, Aerodynamics, Structures and Turbulence) code which is
also developed by NREL. Simulink is used to model the PMSG, full
scale back to back IGBT converters, and the grid.
Abstract: This paper presents a numerical analysis of the
performance of a three-bladed Darrieus vertical-axis wind turbine
based on the DU91-W2-250 airfoil. A complete campaign of 2-D
simulations, performed for several values of tip speed ratio and based
on RANS unsteady calculations, has been performed to obtain the
rotor torque and power curves. Rotor performances have been
compared with the results of a previous work based on the use of the
NACA 0021 airfoil. Both the power coefficient and the torque
coefficient have been determined as a function of the tip speed ratio.
The flow field around rotor blades has also been analyzed. As a final
result, the performance of the DU airfoil based rotor appears to be
lower than the one based on the NACA 0021 blade section. This
behavior could be due to the higher stall characteristics of the NACA
profile, being the separation zone at the trailing edge more extended
for the DU airfoil.
Abstract: With continuous rise of oil price, how to develop alternative energy source has become a hot topic around the world. This study discussed the dynamic characteristics of an island power system operating under random wind speed lower than nominal wind
speeds of wind turbines. The system primarily consists of three diesel engine power generation systems, three constant-speed variable-pitch wind turbines, a small hydraulic induction generation system, and lumped static loads. Detailed models based on Matlab/Simulink were developed to cater for the dynamic behavior of the system. The results suggested this island power system can operate stably in this operational mode. This study can serve as an important reference for planning, operation, and further expansion of island power systems.
Abstract: The aerodynamic performances of vertical axis wind
turbines are highly affected by tip vortexes. In the present
work, different tip devices are considered and simulated against
a baseline rotor configuration, with the aim of identifying the
best tip architecture. Three different configurations are tested:
winglets, an elliptic termination and an aerodynamic bulkhead.
A comparative analysis on the most promising architectures is
conducted, focusing also on blade torque evolution during a full
revolution of the rotor blade. The most promising technology is
concluded to be a well designed winglet.
Abstract: A multiple-option analytical model for the evaluation of the energy performance and distribution of aerodynamic forces acting on a vertical-axis Darrieus wind turbine depending on both rotor architecture and operating conditions is presented. For this purpose, a numerical algorithm, capable of generating the desired rotor conformation depending on design geometric parameters, is coupled to a Single/Double-Disk Multiple-Streamtube Blade Element – Momentum code. Both single and double-disk configurations are analyzed and model predictions are compared to literature experimental data in order to test the capability of the code for predicting rotor performance. Effective airfoil characteristics based on local blade Reynolds number are obtained through interpolation of literature low-Reynolds airfoil databases. Some corrections are introduced inside the original model with the aim of simulating also the effects of blade dynamic stall, rotor streamtube expansion and blade finite aspect ratio, for which a new empirical relationship to better fit the experimental data is proposed. In order to predict also open field rotor operation, a freestream wind shear profile is implemented, reproducing the effect of atmospheric boundary layer.
Abstract: A preliminary evaluation of the feasibility of installing small wind turbines on offshore oil and gas extraction platforms is presented. Some aerodynamic considerations are developed in order to determine the best rotor architecture to exploit the wind potential on such installations, assuming that wind conditions over the platforms are similar to those registered on the roofs of urban buildings. Economical considerations about both advantages and disadvantages of the exploitation of wind energy on offshore extraction platforms with respect to conventional offshore wind plants, is also presented. Finally, wind charts of European offshore winds are presented together with a map of the major offshore installations.
Abstract: A complete CAD procedure to model a twisted-bladed
vertical-axis wind turbine (VAWT) is presented with the aim of
determining some practical guidelines to be used for the generation
of an easily-meshable CAD geometry to be adopted as the basis of
both CFD and FEM numerical simulations.
Abstract: In this study, aeroelastic response and performance
analyses have been conducted for a 5MW-Class composite wind
turbine blade model. Advanced coupled numerical method based on
computational fluid dynamics (CFD) and computational flexible
multi-body dynamics (CFMBD) has been developed in order to
investigate aeroelastic responses and performance characteristics of
the rotating composite blade. Reynolds-Averaged Navier-Stokes
(RANS) equations with k-ω SST turbulence model were solved for
unsteady flow problems on the rotating turbine blade model. Also,
structural analyses considering rotating effect have been conducted
using the general nonlinear finite element method. A fully implicit
time marching scheme based on the Newmark direct integration
method is applied to solve the coupled aeroelastic governing equations
of the 3D turbine blade for fluid-structure interaction (FSI) problems.
Detailed dynamic responses and instantaneous velocity contour on the
blade surfaces which considering flow-separation effects were
presented to show the multi-physical phenomenon of the huge rotating
wind- turbine blade model.
Abstract: Optimal load shedding (LS) design as an emergency plan is one of the main control challenges posed by emerging new uncertainties and numerous distributed generators including renewable energy sources in a modern power system. This paper presents an overview of the key issues and new challenges on optimal LS synthesis concerning the integration of wind turbine units into the power systems. Following a brief survey on the existing LS methods, the impact of power fluctuation produced by wind powers on system frequency and voltage performance is presented. The most LS schemas proposed so far used voltage or frequency parameter via under-frequency or under-voltage LS schemes. Here, the necessity of considering both voltage and frequency indices to achieve a more effective and comprehensive LS strategy is emphasized. Then it is clarified that this problem will be more dominated in the presence of wind turbines.
Abstract: The three-time-scale plant model of a wind power
generator, including a wind turbine, a flexible vertical shaft, a Variable
Inertia Flywheel (VIF) module, an Active Magnetic Bearing (AMB)
unit and the applied wind sequence, is constructed. In order to make
the wind power generator be still able to operate as the spindle speed
exceeds its rated speed, the VIF is equipped so that the spindle speed
can be appropriately slowed down once any stronger wind field is
exerted. To prevent any potential damage due to collision by shaft
against conventional bearings, the AMB unit is proposed to regulate
the shaft position deviation. By singular perturbation order-reduction
technique, a lower-order plant model can be established for the
synthesis of feedback controller. Two major system parameter
uncertainties, an additive uncertainty and a multiplicative uncertainty,
are constituted by the wind turbine and the VIF respectively.
Frequency Shaping Sliding Mode Control (FSSMC) loop is proposed
to account for these uncertainties and suppress the unmodeled
higher-order plant dynamics. At last, the efficacy of the FSSMC is
verified by intensive computer and experimental simulations for
regulation on position deviation of the shaft and counter-balance of
unpredictable wind disturbance.
Abstract: This paper presents a model for the evaluation of
energy performance and aerodynamic forces acting on a three-bladed
small vertical axis Darrieus wind turbine depending on blade chord
curvature with respect to rotor axis.
The adopted survey methodology is based on an analytical code
coupled to a solid modeling software, capable of generating the
desired blade geometry depending on the blade design geometric
parameters, which is linked to a finite volume CFD code for the
calculation of rotor performance.
After describing and validating the model with experimental data,
the results of numerical simulations are proposed on the bases of two
different blade profile architectures, which are respectively
characterized by a straight chord and by a curved one, having a chord
radius equal to rotor external circumference. A CFD campaign of
analysis is completed for three blade-candidate airfoil sections, that is
the recently-developed DU 06-W-200 cambered blade profile, a
classical symmetrical NACA 0021 and its derived cambered airfoil,
characterized by a curved chord, having a chord radius equal to rotor
external circumference.
The effects of blade chord curvature on angle of attack, blade
tangential and normal forces are first investigated and then the
overall rotor torque and power are analyzed as a function of blade
azimuthal position, achieving a numerical quantification of the
influence of blade camber on overall rotor performance.
Abstract: This paper explores steady-state characteristics of
grid-connected doubly fed induction motor (DFIM) in case of unity
power factor operation. Based on the synchronized mathematical
model, analytic determination of the control laws is presented and
illustrated by various figures to understand the effect of the applied
rotor voltage on the speed and the active power. On other hand,
unlike previous works where the stator resistance was neglected, in
this work, stator resistance is included such that the equations can be
applied to small wind turbine generators which are becoming more
popular. Finally the work is crowned by integration of the studied
induction generator in a wind system where an open loop control is
proposed confers a remarkable simplicity of implementation
compared to the known methods.
Abstract: Nuclear energy sources have been widely used in the
past decades in order to power spacecraft subsystems. Nevertheless,
their use has attracted controversy because of the risk of harmful
material released into the atmosphere if an accident were to occur
during the launch phase of the mission, leading to the general
adoption of photovoltaic systems.
As compared to solar cells, wind turbines have a great advantage
on Mars, as they can continuously produce power both during dust
storms and at night-time: this paper focuses on the potential of a wind
energy conversion system (WECS) considering the atmospheric
conditions on Mars. Wind potential on Martian surface has been
estimated, as well as the average energy requirements of a Martian
probe or surface rover. Finally, the expected daily energy output of
the WECS has been computed on the basis of both the swept area of
the rotor and the equivalent wind speed at the landing site.
Abstract: This paper addresses linear quadratic regulation (LQR)
for variable speed variable pitch wind turbines. Because of the
inherent nonlinearity of wind turbine, a set of operating conditions is
identified and then a LQR controller is designed for each operating
point. The feedback controller gains are then interpolated linearly to
get control law for the entire operating region. Besides, the
aerodynamic torque and effective wind speed are estimated online to
get the gain-scheduling variable for implementing the controller. The
potential of the method is verified through simulation with the help of
MATLAB/Simulink and GH Bladed. The performance and
mechanical load when using LQR are also compared with that when
using PI controller.
Abstract: This paper proposes the study of a robust control of
the doubly fed induction generator (DFIG) used in a wind energy
production. The proposed control is based on the linear active
disturbance rejection control (ADRC) and it is applied to the control
currents rotor of the DFIG, the DC bus voltage and active and
reactive power exchanged between the DFIG and the network. The
system under study and the proposed control are simulated using
MATLAB/SIMULINK.
Abstract: Nowadays, power systems, energy generation by wind
has been very important. Noting that the production of electrical
energy by wind turbines on site to several factors (such as wind speed
and profile site for the turbines, especially off the wind input speed,
wind rated speed and wind output speed disconnect) is dependent. On
the other hand, several different types of turbines in the market there.
Therefore, selecting a turbine that its capacity could also answer the
need for electric consumers the efficiency is high something is
important and necessary. In this context, calculating the amount of
wind power to help optimize overall network, system operation, in
determining the parameters of wind power is very important.
In this article, to help calculate the amount of wind power plant,
connected to the national network in the region Manjil wind,
selecting the best type of turbine and power delivery profile
appropriate to the network using Monte Carlo method has been.
In this paper, wind speed data from the wind site in Manjil, as minute
and during the year has been. Necessary simulations based on
Random Numbers Simulation method and repeat, using the software
MATLAB and Excel has been done.
Abstract: The main aim of this work is to establish the
capabilities of new green buildings to ascertain off-grid electricity
generation based on the integration of wind turbines in the
conceptual model of a rotating tower [2] in Dubai. An in depth
performance analysis of the WinWind 3.0MW [3] wind turbine is
performed. Data based on the Dubai Meteorological Services is
collected and analyzed in conjunction with the performance analysis
of this wind turbine. The mathematical model is compared with
Computational Fluid Dynamics (CFD) results based on a conceptual
rotating tower design model. The comparison results are further
validated and verified for accuracy by conducting experiments on a
scaled prototype of the tower design. The study concluded that
integrating wind turbines inside a rotating tower can generate enough
electricity to meet the required power consumption of the building,
which equates to a wind farm containing 9 horizontal axis wind
turbines located at an approximate area of 3,237,485 m2 [14].
Abstract: This paper presents a model for the evaluation of
energy performance and aerodynamic forces acting on a small
straight-bladed Darrieus-type vertical axis wind turbine depending on
blade geometrical section. It consists of an analytical code coupled to
a solid modeling software, capable of generating the desired blade
geometry based on the desired blade design geometric parameters.
Such module is then linked to a finite volume commercial CFD code
for the calculation of rotor performance by integration of the
aerodynamic forces along the perimeter of each blade for a full period
of revolution.After describing and validating the computational
model with experimental data, the results of numerical simulations
are proposed on the bases of two candidate airfoil sections, that is a
classical symmetrical NACA 0021 blade profile and the recently
developed DU 06-W-200 non-symmetric and laminar blade
profile.Through a full CFD campaign of analysis, the effects of blade
geometrical section on angle of attack are first investigated and then
the overall rotor torque and power are analyzed as a function of blade
azimuthal position, achieving a numerical quantification of the
influence of airfoil geometry on overall rotor performance.