As a part of the new energy development trend, distributed power generation may fully utilize a variety of decentralized energy sources. Buildings close to the installation location, besides, may have a considerable impact on the wind turbines’ operation. Using a combined vertical axis wind turbine with an S-shaped lift outer blade and Φ-shaped drag inner blade, this paper investigates how a novel type of upstream wall interacts with the incident wind at various speeds, the influence region of the turbulent vortex, and performance variation. The results demonstrate that the building’s turbulence affects the wind’s horizontal and vertical direction, as well as its speed, in downstream places. The wall’s effect on wind speed changing in the downstream area is thoroughly investigated. It turns out that while choosing an installation location, disturbing flow areas or low disturbing flow zones should be avoided to have the least impact on wind turbine performance.
The world’s mainstream wind turbines are currently large and medium-sized horizontal axis wind turbines with mature technology and uniform standards; research on vertical axis wind turbines is relatively lagging behind, mainly in the stage of wind tunnel experiments and field tests, with small and medium-sized turbines. A horizontal axis wind turbine has the benefits of a high operating wind speed, stable aerodynamic load, and relatively simple aerodynamics, but it also has the disadvantages of a yaw wind device and high noise, making it unsuitable for use in urban areas with low wind speeds and high turbulence intensity [
Early international scientists used a two-dimensional flow field to simulate and determine the aerodynamic performance of vertical axis wind turbines, and the applicability of sliding mesh in the computation of vertical axis wind turbine blade technology was validated [
Turbulence intensity can increase mechanical stress on turbine components and reduce turbine life. For small wind turbines, obstacles such as buildings and trees may cause high levels of free flow turbulence [
Turbulence formed as the incoming wind comes in from the wall and passes over the wind turbine due to the presence of the wall, and the presence of turbulence will have a substantial impact on the wind turbine’s performance. As a result, more research into the turbulence distribution induced by the flow field through the building is needed.
The research object in this work is a 700 W mixed vertical axis wind turbine. The wind turbine is located in the Jinchuan Development Zone, Hohhot, Inner Mongolia Autonomous Region’s experimental base, which is situated in an open area with sufficient wind resources throughout the year, as shown in
This study focuses solely on the wind turbine’s wind wheel. The characteristics affecting the wind turbine and the wall are depicted in
Calculation parameters | Parameter data |
---|---|
Wind turbine type and rated power [W] | 700 |
Blade type | Φ-shaped drag inner blade, S-shaped lift outer blade |
Rated wind speed [m/s]/rated speed of wind turbine [rpm] | 12/415 |
Blade height of wind turbine internal resistance [m] | 0.446 |
Part height/sweep diameter of wind wheel [m] | 1.547/1.92 |
Cut-out speed [m/s] | 25 |
Endurance wind speed limit [m/s] | 60 |
Wall height [m]/thickness [m] | 3/0.5 |
Distance between wall and wind turbine [m] | 4 |
The 700 W vertical axis wind turbine is simulated and modeled in this work. The vertical axis wind turbine is simplified since some components have little impact on aerodynamics. The diameter of the wind turbine’s internal resistance blade is 0.357 m, the height of the internal resistance vanes is 0.446 m, the height of the wind turbine is 1.547 m, and the sweeping diameter of the wind turbine is 1.92 m after simplification. The dimensions of the model are displayed in
The relative height between the upper edge of the wall and the wind turbine’s wind wheel is ∆
In the computation domain, the method of managing blockage rate Q is used. The calculation domain for this paper is 20D
In this paper, the hexahedral unstructured grid is chosen for a grid division. The wind turbine and its wake area, as well as the wind turbine rotation area and wake area, are subjected to grid densification to better monitor wind speed and turbulence variations surrounding the wall, as shown in
For meshing, a three-layer hexahedral mesh boundary is chosen, and a set of five meshes that converge satisfactorily under rated conditions is collected to validate their independence from one another. According to the calculations shown in
Group | 1 | 2 | 3 | 4 | 5 |
---|---|---|---|---|---|
Grid number [million] | 200 | 300 | 400 | 500 | 600 |
Power [W] | 592.93 | 603.45 | 612.38 | 614.87 | 616.76 |
Wind turbine power is an important metric for determining a wind turbine’s functioning capability.
T——Wind turbine impeller torque, Nm;
n——Wind turbine blade speed, rpm.
In comparison to the standard model, the realizable model uses unique mathematical approaches to confine normal stress and includes a turbulent viscous formula [
In the formula:
Among them,
A realizable model is more accurate in predicting rotational flow, strong adverse pressure gradient boundary layer flow, separated flow, and secondary flow. The treatment of strong bending streamlines, vortices, and rotating flows is superior to other models. The disadvantage of this method is that the effect of average rotation is taken into account when defining turbulent viscosity, so the natural turbulent viscosity cannot be provided when calculating the rotational and static flow regions [
Three-dimensional models, hidden transient solutions, separation solvers, gas, and equations are among the options available. In the Realizable turbulence model, the rotation rate is set to n = 415 rpm, and the vertical axis wind turbine is numerically simulated at five different wind speeds (
Calculating the wind turbine’s speed allows us to determine the time required to rotate n degrees or the time step:
The maximum physical time in this article is 5 s, the time step is 0.001 s, and the internal iteration is 5.
The basic mechanics of a wind turbine is simulated at different incoming wind speeds (
The horizontal speed variation trend under different incoming wind speeds is generally the same, as shown by the variation curve of wind speed variation in
The power using coefficient reaches the decide value when the turbine speed and the wind speed achieve the optimal ratio, according to the Betz theory. Therefore, when the optimal tip speed ratio of the wind turbine is 3.48, as can be observed in
The variation curve of the wind energy utilization coefficient, as shown in
The average wind speed is observed at the upper edge, lower edge, center, and windward blade of a wind turbine under two distinct scenarios to study the influence of building turbulence on wind speed at a wind turbine. The wind speed ratio (the ratio of wind speed under wall-existing conditions to that under the wallless condition,
The power variation and the wind energy utilization coefficient under the two operating conditions are plotted based on the calculation results, as shown in
In both cases, the power and wind energy utilization coefficient curves in
The following results are obtained from a performance study of distributed vertical axis wind turbines under building turbulence:
The evolution of the numerical simulation power curve is compared to the wind turbine manufacturer’s power curve. The growth is consistent, indicating that the numerical simulation is accurate and genuine. In the downstream locations, the building turbulence will impact the wind speed and flow direction horizontally and vertically. As a result, the wind speed in the downstream section exceeds the wind turbine’s cut-out and endurance wind speed limits. At low wind speeds, the wind turbine is placed in the vortex area of a turbulent wall, where the wind speed is higher than the incoming wind speed, resulting in increased wind power and a higher wind energy utilization coefficient. The wind turbine, what’s more, is removed from the turbulent vortex at high wind speeds, resulting in a lower wind speed at the wind turbine position than the incoming speed, as well as a lower power and energy utilization coefficient. The impact of the wall on wind speed fluctuations in the downstream area is thoroughly investigated. It turns out that to have a minimal impact on wind turbine performance, disturbing flow areas or low disturbing flow areas should be avoided while selecting an installation location.
The authors gratefully acknowledge the Provincial, Municipal and Autonomous Region Science and Technology Project Funds of China (2021GG0336 and 2016030331).