Effect of blade installation angle on power efficiency of resistance type VAWT by CFD study
Int J Energy Environ Eng
Effect of blade installation angle on power efficiency of resistance type VAWT by CFD study
Maosheng Zheng 0 1
Yusheng Li 0 1
Yangyang Tian 0 1
Jun Hu 0 1
Yuan Zhao 0 1
Lijun Yu 0 1
0 M. Zheng Y. Zhao Institute of Shaanxi Energy Resource and Chemical Engineering , Xi'an 710069 , China
1 M. Zheng (&) Y. Li Y. Tian J. Hu Y. Zhao L. Yu Institute for Energy Transmission Technology and Application, School of Chemical Engineering, Northwest University , Xi'an 710069 , China
Renewable energy is an inevitable choice to meet the demands of energy resource. In the 21st century, one of the serious problems facings us is the energy resources that restrict the social progress and sustainable development. Environmental pollution and fossil energy resources shortage force people to explore and use new energy resources. The aim of this paper is to study the effect of blade installation angle on power coefficient of a five-blade resistance type vertical axis wind turbine using CFD simulations. The computation is conducted for the turbine with the blade diameter of 0.76-0.86 m and the turbine radius R = 2 m. The results show that the maximum value of power efficiency of 28.48 % can be obtained when the installation angle is 19 for the five-blade resistance type vertical axis wind turbine with the blade diameter of 0.78 m and the turbine radius R = 2 m.
CFD; VAWT angle; Power coefficient; Resistance type; Installation
List of symbols
R Wind turbine maximum radius (m)
r Radius of the blade (m)
d Diameter of blade (m)
L The length of the computation region (m)
H The width of the computation region (m)
Constant equal to 0.6125
Power coefficient
Power produced by the turbine (w)
Torque coefficient
Inlet wind speed (m/s)
Rotor rotational rate of turbine (rpm)
Rotor swept area (m2)
Air density (kg/m3)
Installation angle of the blade ( )
Introduction
In the 21st century, one of the serious problems facing us is
the energy resources that restrict the social progress and
sustainable development. Environmental pollution and
fossil energy resources shortage force people to explore
and use new energy resource. Renewable energy and
sustainable development is a common concerned subject of
the whole world. Wind energy is one of the most promising
resources of renewable energy, many countries have grant
plan to explore and use it due to its great advantage of
pollution free, abundant availability and conversion
locally, etc. It can thus help us to reduce environmental
pollution and the dependency on fossil fuels [
1
].
The most application of wind energy is to generate
electrical power through various types of wind turbines.
Wind turbines can be classified into two families generally,
i.e., the horizontal axial wind turbine (HAWT) and the
vertical axial wind turbine (VAWT) [
2
]. A lot of study has
been focused on HAWT till now, while the study of
VAWT is relatively rare. However, VAWT has its greatest
advantage of ‘‘omnidirection’’. Although the propeller-type
windmill could provide a larger power output, it needs
greater wind velocity that is almost impossible in city.
Besides, HAWT induces low frequency noise that is
harmful to animals. It also has a weak response to temporal
changes of wind velocity and direction. However, VAWT
escapes these environmental problems, resulting in their
use in urban environments.
Savonius type is one of the oldest types of the VAWT. It
has been studied since the pioneer work of Savonius.
Although the Darrieus type Vertical Axis Wind Turbine is
more efficient than the Savonius type, the several
advantages of Savonius type are still attractive, such as good
starting torque, simple mechanism, lower rotation speed,
and omnidirectional characteristics [
3
]. Unlike the Darrieus
type of wind turbines, the Savonius type wind turbine is
commonly considered as a drag-driven type of wind
turbine. The general theory of the Savonius turbine is simple.
The wind exerts a force on a surface and this surface is then
moved around an axis.
Mahmoud et al. [
4
] studied the Savonius rotor
performance experimentally, it was found that, the two-blade
rotor is more efficient than three and four ones. The rotor
with end plates gives higher efficiency than those of
without end plates. Double stage rotors have higher
performance compared to single stage rotors. The rotors
without overlap ratio are better in operation than those with
overlap. Zhao et al. [
5
] also studied the influence of blade
number on power efficiency of Savonius turbine
numerically, it was found that, the two-blade rotor is more
efficient than three ones as well, and they clarified that the
actual reason for the blade number influence is induced by
the ‘‘shading effect’’. From flowing field analysis, it is
found that the effective concave winding area of the blade
decreases due to the shading of the nearby blade for the
three-blade Savonius turbine, while the effective convex
winding area of the blade increases du (...truncated)