Технические науки/5.Энергетика
Doctor of
technical sciences Kirpichnikova I.M.
Post Graduate
Kozin A.A.
South Ural State
University, Russia
The comparative analysis of wind farms built on the basis of
vertical-axis and horizontal-axis wind turbines
Modern wind turbines are used most frequently in the
wind farms have found horizontal-axis wind turbines. It is because of the unit
capacity to generate electricity on an industrial scale. However, the trend of the industry
shows an increasing demand on the vertical centerline of the installation. Nowadays they are used mainly as
individual, autonomous power supply for consumers.
We have investigated the main parameters that
characterize the work of wind turbines in the wind farms, and compared with
this point of view between the main types of wind turbine designs -
horizontal-axis wind turbine and vertical-axis wind turbine. As an example, considered in the wind
turbine (Darrieus-type straight blades), created in the SRC
"Vertical", Miass, Chelyabinsk region.
A comparative
analysis is based on the following parameters:
1.
The location of wind
turbines in the wind farm.
The obvious positive feature in vertical-axis wind
turbine is that they take up less space than a similar capacity horizontal-axis
wind turbine, as well as a number of advantages when placed in an urban
environment [1]. Furthermore, an
additional advantage of vertical-axis design is the possibility of increasing
the swept area of a height that it is impossible for horizontal-axis wind
turbine.
2.
Connections of wind
turbines in the stations.
For connecting the vertical-axis wind turbines in the
wind power plants may be applied connection scheme, similar to schemes used in
wind turbines using the horizontal-axis wind turbine in the wind power plants. However, it should be noted that each
scheme has its own scope, which depends on the conditions of a specific
customer [2]. Thus, using vertical-axis design in wind farms according
to this indicator is a good reason.
3.
The dependence of the
efficiency of wind turbines on the wind direction
It is known that the maximum efficiency of horizontal-axis
wind turbine can only be achieved provided that the constant collinearity axis
rotor and the wind direction, which complicates the design, reduces reliability
and increases the cost of wind turbines.
The effectiveness of the same vertical-axis wind
turbines essentially does not depend on wind direction, and therefore
eliminates the need for mechanisms and systems of orientation to the wind. Inequality of characteristics of wind
flow adjustment leads only to a certain alignment of the moments of rotation,
removed from the blades.
4.
The coefficient of wind
energy with CP.
The coefficient of wind energy is a key indicator of
any wind turbine. For an ideal
rotor horizontal, propeller and vertical-axis turbines it is equal to 0.593. This value is theoretically obtained
from the condition that
v1/v = 1/3,
where v - speed of flow of the wind; v1 - wind speed in the plane of the
wheel.
So, the wind wheel should work so that the loss of
wind speed in the plane of rotation is 1/3 of the incoming values. In fact, the coefficient of wind
energy CP. significantly
less for high-speed wind turbines is 0,45 ... 0,48; for slow - 0,35…0,38 (Fig. 1).
Figure 1
- Dependence of wind energy CP on the coefficient
of rapidity (1 - a perfect wind-wheel; 2,3 and 4 - two - three and a
multi-bladed horizontal-axis wind turbine 5 - Daria rotor 6 - Savonius rotor, 7
- a four wind wheel Danish windmill, 8 - wind turbine 3 kW produced by
"SRC-Vertical")
For modern wind turbines produced by
"SRC-Vertical", this ratio is 0,38. Experimental
data obtained during testing of such installations have shown that obtaining
the coefficient CP, equal
to 0,4-0,45 is within reach. Therefore,
to consider setting a horizontal-axis and vertical-axis wind turbines are
close, which also provides a basis for investigating the possibility of work in
wind turbines in the wind farms.
5.
Design features of wind
turbine blades and wind turbines
Comparative characteristics of wind turbine design
features are presented in Table 1.
Table 1.
Comparative characteristics of wind power
on design features
|
Key
Features |
Horizontal-axis |
Vertical-axis |
|
|
1 |
Orientation
to the wind |
Availability of parts and systems
orientation |
Not
required |
|
2 |
Removal
of wind rotor |
The maximum removal of energy in a
narrow range of wind |
The maximum removal of energy
throughout the range of winds |
|
3 |
Placement of the generator and the
multiplier |
In the nacelle on the tower |
On the foundations of the tower |
|
|
Wheel hub and bearing assembly of
support |
Compact
and small-sized |
The
large size |
|
4 |
Automatic starting of pumping
jacks |
Yes |
Yes |
|
|
The load on the blade |
The
minimum |
The
maximum |
|
5 |
Rotating
blades |
Yes |
No |
|
6 |
The design of the blades |
Twist and narrowing of the blade |
The blade profile with a constant |
Availability of parts and systems focus on wind in
horizontal-axis wind turbine considerably complicates the design and the need
for continuous tracking of the wind direction reduces the efficiency of wind
turbines.
An important feature of wind turbines,
"SRC-Vertical" is the independence of its work on the wind direction,
and power generation is a wide range of winds, from the minimum.
The ability to place the generator and the multiplier
on the base installation is also a great advantage vertical-axis wind turbine
in front of horizontal-axis wind turbine. When
placing the equipment in the basement of his condition dramatically improved
installation and operation easier transmission of electricity generated, which
is a positive factor in the placement of wind turbines in wind farms.
As for the inertial loads on the blade, then
horizontal-axis wind turbines are directed along the blade that is the most advantageous manner as
compared with vertical-axis turbines. For
this indicator, vertical-axis wind turbines a lesser degree satisfies the
requirement of rationality of power circuit than the horizontal-axis wind
turbines and requires scientific and practical work to improve the design.
6. Specific
speed
For horizontal-axis wind turbines with turbines large
diameter increases the effect of wind speed acoplanarity height and the impact
of gravitational forces causing the pulsating load in the material the blade,
in the supporting device transmissions and transmissions in themselves. These effects and the impact of the
more tangible, the higher the specific speed, predetermining attention to the
dynamic stability of all rotating parts, increased requirements for structural
strength and accuracy of its production, the build quality, lubrication and
balancing of rotating parts and assemblies.
From this point of view of vertical-axis scheme,
essentially providing the low-speed wind turbines work, is the best. It is important that with all the
energy characteristics (including the utilization of wind energy) vertical-axis
wind turbines remain at similar characteristics horizontal-axis wind turbines.
7.
Reliability
Vertical-axis wind turbines, particularly units of
high power, offer higher reliability. The
basis for such assertions is significantly simplified design (lower level
requirements to manufacture transmissions, simplification of installation and
operation, etc.). This is due to
the following features of such systems: the lack of mechanisms and control
systems by turning the nacelle to the wind, the location of the generator and
the multiplier on the base, the lack of necessary devices and control systems,
angle the blade, no problems with the transfer of electricity from the
generator.
8.
Comparison of adverse
effects on the environment.
Horizontal-axis wind turbines, which operating in high-power
wind farms, have an undoubted advantage in terms of energy, but it also have
some significant drawbacks. When
their work is a very high noise level, the presence of infrasound, ultrasound
and vibration, for their installation requires a large area.
It is worth noting the negative effects caused by
vibration, horizontal-axis wind turbines: reducing the strength of buildings,
destruction of underground utility systems, migration of animals, birds,
insects, soil erosion, deterioration of health of people [3].
Current trends in wind power related development
vertical-axis wind turbines are explained in the absence of this type of wind
turbines of the above deficiencies, as evidenced by a number of studies [4].
Comparison of horizontal-axis wind turbines and
vertical-axis wind turbines equal power turbines at a cost not recommended as
they are currently more in demand horizontal-axis wind turbines in the world
and are produced in much larger quantities than vertical-axis wind turbines. However, at this moment vertical-axis
wind turbines have a niche for the application.
Analyzing the data by comparing the characteristics of
wind turbines in terms of their use in the wind farm to the following
conclusions:
1. Traditionally
used by horizontal-axis wind turbines wind turbines for some time yet will have
a preferential use of vertical-axis wind turbines before wind turbines due to
the large installed capacity of each wind turbine, comprising the wind farm.
2. The
trend of development of renewable energy in the direction of the local energy
supply facilities allows us to predict the development of wind farms with a
vertical-axis design.
3.
Vertical-axis wind
turbine manufacturing SRC-Vertical best match the characteristics of horizontal-axis
wind turbines operating in the wind farm and, with appropriate structural
refinement can operate in the electricity system objects, uniting several such
facilities.
Literature
1. Kozin,
A.A. Designing of power sports
complex "Nepryakhino" SUSU using wind turbines. // Energy and resources. Energy supply. Alternative and Renewable Energy:
Proceedings of the All-Russian Scientific Conference 22-26 November 2010
Ekaterinburg: UrFU, 2010, pages 359-361.
2. Kozin,
A.A. Pair of wind turbines of
small capacity in the wind power station // Scientific Search. Materials of the third conference
post-graduate and doctoral students.Engineering. Vol 2. Chelyabinsk, South Urals State
University Publishing Center, 2011, pages 203-206.
3. Kirpichnikova,
I., Kozin, A.A. Vibration in the
wind turbine. // Energy and resources. Energy supply. Alternative and Renewable Energy:
Proceedings of the All-Russian Scientific Conference 14-18 December 2009
Ekaterinburg: UrFU, 2010, pages 476-478.
4. Solomin,
E.V. Providing vibrosafety
vertical-axis wind turbines. //
Abstract. Chelyabinsk, 2009, page
23.