EOLIENNE

WIND ENERGY INSTALLATION

Abrégé anglais

The invention relates to a wind energy installation
(10) having a rotor (18) which can be driven by wind
and has at least one rotor blade (22), having a
generator for conversion of the mechanical energy of
the rotor (18) to electrical energy, and having a tower
(14) on which the rotor (18) is arranged, in which the
rotor blade (22) has one or more additional masses (36,
40) and/or active and/or passive oscillation dampers
(24), which are designed in such a manner that
movements of the rotor blade (22), in particular
oscillations, which are initiated by external
influences and are directed towards the tower or away
from it are prevented and/or damped. The invention also
relates to a method for operation of a wind energy
installation, preferably of an off-shore wind energy
installation, in which one or more components of the
wind energy installation, preferably the tower (14),
have opposing vibration applied to them in order to
reduce/prevent sound waves which result from component
vibration and disturb animals and/or people, which
opposing vibration counteracts vibration (which
produces sound) of the component (14), and reduces or
prevents this component vibration.

Revendications

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Claims:
1. Wind energy installation having a rotor (18) which
can be driven by wind and has at least one rotor blade
(22), having a generator for conversion of the
mechanical energy of the rotor (18) to electrical
energy, and having a tower (14) on which the rotor (18)
is arranged, characterized in that the rotor blade (22)
has one or more additional masses (42) and/or active
and/or passive oscillation dampers, which are designed
in such a manner that movements of the rotor blade
(22), in particular oscillations, which are initiated
by external influences and are directed towards the
tower (14) and/or away from it are prevented and/or
damped.
2. Wind energy installation according to Claim 1,
characterized in that the additional mass or masses
(42) is or are arranged and/or designed to vary the
natural oscillation frequency of the rotor (16) or of
the rotor blade (22) in such a manner that the
resultant natural oscillation frequency of the system

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comprising additional masses (42) and the rotor blade
(22) is outside the value range of the excitation
frequencies to be expected for the installation in the
predetermined conditions.
3. Wind energy installation according to Claim 1 or
2, characterized in that the additional masses (42)
and/or the active and/or the passive oscillation
dampers are arranged in the interior of the rotor
blades (22).
4. Wind energy installation according to one or more
of the preceding claims, characterized in that the
active and/or passive oscillation dampers can be used
to initiate movement impulses of the rotor blade (22)
which counteract the movements of the rotor blade (22)
which are directed towards and/or away from the tower
(14), and at least partially compensate for them.
5. Wind energy installation according to one or more
of the preceding claims, at least according to Claim 4,
characterized in that the movement impulses which
compensate for the movements which are directed towards
the tower (14) can be initiated as soon as the movement
which is directed towards the tower (14) starts, or at
a time immediately before or after this.
6. Wind energy installation having a rotor (18) which
can be driven by wind and has at least one rotor blade
(22), having a generator for conversion of the
mechanical energy of the rotor (18) to electrical
energy, and having a tower (14) on which the rotor (18)
is arranged, characterized in that the wind energy
installation (10) has an active oscillation damper (24)
for production of movement impulses which counteract
any movement of the tower (14) of the wind energy
installation which is initiated by external influences.
7. Wind energy installation according to Claim 6,

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characterized in that the tower (14) of the wind energy
installation (10) and/or the pod (16) have/has the
active oscillation damper (24).
8. Wind energy installation according to Claim 7,
characterized in that the active oscillation damper
(24) is arranged in the interior of the tower (14)
and/or in the interior of the pod (16).
9. Wind energy installation according to one or more
of the preceding claims, at least according to Claim 6,
characterized in that the active oscillation damper
(24) is designed in such a manner that the movement
impulse which can be initiated by it counteracts a
tower movement which is produced by each rotor blade
(22) passing the tower.
10. Wind energy installation according to one or more
of the preceding claims, at least according to Claim 6,
characterized in that the active oscillation damper
(24) has at least two masses (36, 40) which
contrarotate about, in particular, a common rotation
axis, with each mass (36, 40) being unbalanced about
the rotation axis.
11. Wind energy installation according to Claim 10,
characterized in that the rotation axis runs
vertically.
12. Wind energy installation according to Claim 10 or
11, characterized in that the rotating masses (36, 40)
are arranged in such a manner, and the rotation
frequencies of the rotating masses (36, 40) are matched
to one another, in such a manner that an opposing
impulse, in the opposite direction to the movement
which is initiated by external influences, can be
initiated.
13. Wind energy installation according to Claim 10, 11

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or 12, characterized in that the rotation frequency of
the masses (36, 40) is matched to the number of rotor
blades (22) in accordance with the following formula:
<IMG>
14. Wind energy installation according to one or more
of the preceding claims, characterized in that the wind
energy installation (10) has sensors by means of which
it is possible to detect movements of the rotor blade
(22) which are directed away from or towards the tower
(14), and/or movements of the tower (14).
15. Wind energy installation according to one or more
of the preceding claims, characterized in that, after
detection of movements of the rotor blade (22) which
are directed towards the tower (14) and/or movements of
the tower (14), suitable opposing impulses, which at
least partially compensate for these movements, of the
active oscillation dampers can be initiated.
16. Wind energy installation according to one or more
of the preceding claims, characterized in that the
instantaneous speed of revolution of the rotor blade
(22) can be determined by means of a suitable sensor
unit, in which case the time at which the rotor blade
(22) subequently passes the tower can be determined in
advance from the speed of revolution by means of a
suitable computer unit, and in which case impulses of
the active oscillation dampers can be initiated at a
calculated time of passing the tower.
17. Method for operation of a wind energy installation
according to one or more of the preceding claims,
characterized in that, after detection of any movement,
which is initiated by external influences, of
components of the wind energy installation, in
particular rotor blade and/or tower movements, and/or

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at times at which such movements are expected, movement
impulses which counteract the movements are initiated
by means of one or more active oscillation dampers.
18. Method according to Claim 17, characterized by one
or more features from Claims 1-16.
19. Method for operation of a wind energy
installation, preferably of an off-shore wind energy
installation, in particular according to one or more of
the preceding claims, with the wind energy installation
(10) having a rotor (18) with at least one rotor blade
(22), a generator for conversion of the mechanical
energy of the rotor (18) to electrical energy, as well
as a tower (14) on which the rotor (18) is arranged,
characterized in that one or more components (14) of
the wind energy installation (10), preferably the tower
(14), have opposing vibration applied to them in order
to reduce/prevent sound waves which result from
component vibration and disturb animals and/or people,
which opposing vibration counteracts vibration (which
produces sound) of the component (14), and reduces or
prevents this component vibration.
20. Method according to Claim 19, characterized in
that the wind energy installation is in the form of an
off-shore wind energy installation, with opposing
vibration being applied at least to that tower section
which is covered by water, such that vibration (which
produces sound and disturbs marine animals) of this
tower section is reduced or prevented.
21. Method according to Claim 19 or 20, characterized
in that one or more sensors detect or detects component
vibration which causes sound waves, and in that the
opposing vibration is applied as a function of the
detected component vibration, in particular as a
function of the frequency and the amplitude of the
detected component vibration.

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22. Method according to one or more of Claims 19-21,
characterized in that the component has opposing
vibration applied to it, whose amplitude and/or
frequency at least approximately match/matches the
amplitude of the detected component vibration, and
preferably are/is identical to it.
23. Method according to one or more of Claims 19-22,
characterized in that the frequency or frequencies of
the opposing vibration originates or originate from the
frequency range which is audible by animals and/or
people.
24. Wind energy installation, in particular according
to one or more of the preceding Claims 1-16, having a
rotor (18) which can be driven by wind and has at least
one rotor blade (22), having a generator for conversion
of the mechanical energy of the rotor (18) to
electrical energy, and having a tower (14) on which the
rotor (18) is arranged, characterized in that the wind
energy installation (10) has at least one vibration
generator, via which one or more components (14) of the
wind energy installation, preferably the tower (14),
can have opposing vibration applied to it or them in
order to reduce/prevent sound waves which result from
component vibration and are disturbing to animals
and/or people, which opposing vibration counteracts
vibration (which produces sound) of the component (14),
and reduces or prevents this component vibration.
25. Wind energy installation according to Claim 24,
characterized in that the vibration generator has
masses or mass bodies (52) which can be moved
controllably, are directly or indirectly connected to
the component (14) and can be moved relative to the
component (14) in order to produce the vibration, and
in particular can be accelerated and/or braked.

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26. Wind energy installation according to Claim 24 or
25, characterized in that the vibration generator has
one or more mass bodies (52) in the interior of the
tower (14), which mass body or bodies (52) can be moved
relative to the tower (14) and can be moved
controllably on a plane which runs at least
approximately horizontally.
27. Wind energy installation according to one or more
of Claims 24-26, characterized in that each mass body
(52) which can be moved controllably is guided along a
guidance direction, preferably a guide straight line,
which runs at least approximately from the tower centre
to the tower edge area, preferably along a radial
direction with respect to a circular tower cross
section.
28. Wind energy installation according to one or more
of Claims 23-27, characterized in that the movable mass
bodies (52) are distributed approximately in the form
of a star over the tower cross section.
29. Wind energy installation according to at least
Claim 27, characterized in that at least two mass
bodies (52) which can be moved controllably
independently of one another are arranged along a
specific guidance direction, namely a specific guide
straight line, preferably along a specific radial
direction with respect to a circular tower cross
section.
30. Wind energy installation according to one or more
of Claims 23-29, characterized in that one or more
sensors for detection of component vibration is or are
arranged on the component (14), in particular on the
tower (14) .

Description

CA 02566376 2006-11-01
15 Wind energy installation
Description:
The present invention relates to a wind energy
installation having a rotor which can be driven by wind
and has at least one rotor blade, having a generator
for conversion of the mechanical energy of the rotor to
electrical energy, and having a tower on which the
rotor is arranged. The present invention also relates
to a method for operation of a wind energy installation
such as this.
Various components in wind energy installations such as
these, in particular the rotor blades as well as the
.tower, have a tendency to start to oscillate, in
particular as a result of external influences. Both the
rotor blades and the tower are excited, for example, by
impulses which are caused whenever each rotor blade
passes the tower. The forces which are exerted by the
wind on the respective rotor blade are less while
passing the tower than in the other phases of its
rotational movement. This is because the tower, which
is arranged behind the rotor blade with respect to the

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wind direction, represents an obstruction for the wind.
Because the forces which act on the rotor blade while
it is passing the tower are less than in the other
phases of rotational movement, the rotor blade and the
tower receive a forwards movement impulse, that is to
say in the direction of the side of the wind energy
installation facing the wind. The certain amount of
elasticity which all of the components originally have
leads to the rotor blade and the tower swinging
backwards again from this forwards-deflected position
initiated by the movement impulse, as soon as the rotor
blade has ceased to pass the tower.
These processes take place whenever each rotor blade
passes the tower. Even with the normal dimensions of
the individual components, in particular of the rotor
blades, nowadays, oscillations such as these have a
negative effect on the life of the components. This
problem is becoming more serious because of the trend
to design wind energy installations with ever larger
dimensions.
A further reason for inadvertent movements, in
particular oscillations, of individual components
during operation of wind energy installations is, for
example, changes in the wind incidence angle of the
individual rotor blades, as well as wind turbulence.
The component oscillations which are based on the
external influences described above become more
critical, of course, the greater the extent to which
the excitation frequency of the movement impulses
acting on them matches the natural frequency of the
components being used. In the worst case, this can lead
to catastrophic resonance (as is known in systems which
can oscillate), resulting in destruction of the
components.

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Furthermore, internal and external influences can
excite various components in the wind energy
installation to oscillate in a particular manner, whose
frequencies are in the range which is audible by people
and/or animals. These oscillations, which are referred
to in the following text as vibration, lead to acoustic
signals, that is to say noise which is disturbing or
even dangerous to people and/or animals. Component
vibration such as this is frequently caused by natural
oscillations of the generator or of other components in
the wind energy installation. Component vibration can
be extremely problematic, particularly in the case of
off-shore wind energy installations. Vibration of the
tower, in particular of that tower section which is
located in the water, can lead to noise which disturbs
or even drives away animals in the sea, for example all
types of fish.
One object of the present invention is to specify a
wind energy installation in which the abovementioned
damaging movements/oscillations, in particular
vibration, of the rotor blade and/or of other
components, in particular of the tower, of the wind
energy installation are prevented, reduced and/or
damped. A further object of the present invention is to
specify a method for operation of the wind energy
installation such as this.
This object is achieved by the features of Claim 1.
The rotor blade accordingly and advantageously has
additional masses and/or active and/or passive
oscillation dampers, which are designed in such a manner
that movements or movement components of the rotor blade,
in particular oscillations, which are initiated by
external influences and are directed towards the tower
and/or away from it are prevented and/or damped or
reduced. Thus, according to the invention, the aim is to
restrict or prevent those movement components of the

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movements of the rotor blade which run out of the rotor
plane or rotor blade blade plane which runs at right
angles to the rotor shaft.
The rotor blade mass or masses which is or are
additional to the normal rotor blade design lead, with
suitable positioning and design, to the overall system
comprising the rotor blade and the additional mass or
masses having a different natural oscillation frequency
to that of the rotor blade. In this case, the
additional mass or masses is or are preferably arranged
and/or designed, in order to vary the natural
oscillation frequency of the rotor blade, in such a
manner that the resultant natural oscillation frequency
of the system comprising the additional mass and the
rotor blade is outside the excitation frequency value
range to be expected for the installation in the given
conditions. The theoretically feasible excitation
frequencies, that is to say those frequencies at which,
in principle, the movements or movement components of
the rotor blade which are directed towards or away from
the tower can be initiated, can be determined for
respective theoretically predictable wind speeds, for
the given dimensions of the installation, for every
wind energy installation. If, as a result of suitable
adaptation of the additional masses of the rotor blade,
the natural oscillation frequencies are well outside
the value range of the excitation frequencies to be
expected, then this, in particular, effectively
prevents so-called catastrophic resonances.
The additional masses are preferably mounted in the
interior of the rotor blades. Alternatively, of course,
it is also possible to arrange them partially or
completely outside the rotor blades. In order not to
interfere with the aerodynamics, the additional masses
should preferably be arranged on the side of the rotor
blade facing away from the wind. The masses may, of
course, have any shape identified by a person skilled

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in the art in this field. Depending on the arrangement
and weight of the masses, the natural oscillation
behaviour of the rotor blade, preferably of all of the
rotor blades in the wind energy installation, can be
varied as desired.
As an alternative to the masses which vary the natural
oscillation behaviour, the active and/or passive
oscillation dampers are provided according to the
invention, and can likewise be part of the rotor
blades. These oscillation dampers make it possible to
initiate movement impulses for the rotor blade, which
counteract those movements of the correspondingly
equipped rotor blade which are directed towards or away
from the tower, and at least partially, and preferably
completely, compensate for these movements. The above
statements relating to the arrangement of the
additional masses apply to the arrangement and design
of the active and/or passive oscillation dampers.
The movement impulses which compensate for the
movements which are directed towards or away from the
tower can preferably be initiated as soon as the
movement which is directed towards or away from the
tower starts, or at a time immediately before or after
this. If, by way of example, a movement which is
directed away from the tower is initiated by a rotor
blade passing the tower, a movement impulse which
directs the rotor blade towards the tower can be
initiated whenever the rotor blade passes the tower,
counteracting that impulse which is initiated
externally by passing the tower. In short, a movement
impulse which runs in the opposite direction is used to
counteract the movement impulse of the rotor blade,
which is caused by an external influence and moves it
away from the tower.
The object of the present invention is also achieved by
the features of Claim 6.

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According to this claim, the wind energy installation
has one or more active oscillation dampers for
production of movement impulses, which specifically
counteract any movement of the tower of the wind energy
installation which is initiated by external influences.
In this case, the tower and/or the pod of the wind
energy installation preferably has the active
oscillation damper. This active oscillation damper can
be arranged in the interior of the tower, and/or in the
interior of the pod. Alternatively, of course, it is
feasible for it also to be arranged at least partially
externally on the components.
In one preferred embodiment, the active oscillation
damper is designed in such a manner that the movement
impulse which can be initiated by it counteracts a
tower movement which is produced as each rotor blade
passes the tower. In this case, the active oscillation
damper may have at least two masses which contrarotate
about, in particular, a common rotation axis, with each
mass being unbalanced about the rotation axis. In this
case, the rotating masses can be arranged, and the
rotation frequencies of the rotating masses can be
matched to one another, in such a manner that an
opposing impulse, in the opposite direction to the
movement which is initiated by external influences, can
be initiated.
The frequency at which the masses rotate about the
preferably vertical rotation axis is in this case
matched to the number of rotor blades. The majority of
conventional wind energy installations nowadays have
three rotor blades. Rotor blades accordingly pass the
tower three times during one complete revolution of the
rotor. These three passes by the tower can be
compensated for, for example, by the frequency of the
masses with which they rotate about the rotation axis
corresponding to three times the frequency of the rotor

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blades, since each complete rotation of the masses
results in one and only one opposing impulse.
It is particularly preferable for the wind energy
installation to have sensors by means of which it is
possible to detect movements of the rotor blade which
are directed away from or towards the tower, and/or
movements of the tower. The at least partially
compensating opposing pulses from the active
oscillation dampers can then be initiated as a function
of movements detected in this way.
Furthermore, a sensor can be provided which in each
case detects the instantaneous speed of revolution of
the rotor blade or blades during operation, and/or a
defined null-point position of the rotor blades, so
that it is possible to predict each rotor blade passing
the tower. The sensor can accordingly determine the
instantaneous speed of revolution of the rotor blade,
in which case the time at which the rotor blade
subequently passes the tower can be determined in
advance from the speed of revolution by means of a
suitable computer unit, and in which case impulses (in
the opposite direction to the expected movements of the
rotor blade) from the active oscillation dampers can be
initiated at a time of passing the tower that is
calculated by the computation unit.
The present invention also relates to a method for
operation of a wind energy installation, as mentioned
above, according to Claims 17 and 18.
The object of the present invention is also achieved by
a method according to Claim 19.
This claim specifies a method for operation of a wind
energy installation, preferably of an off-shore wind
energy installation, in which one or more components of
the wind energy installation, preferably the tower,

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have opposing vibration applied to them in order to
reduce/prevent sound waves which result from component
vibration and disturb animals and/or people, which
opposing vibration is in the opposite direction to the
component vibration which produces the sound, and
reduces or prevents this component vibration. One or
more components of the wind energy installation
accordingly also have corresponding opposing movements,
specifically opposing vibration, applied to them in the
oscillation range which is audible by animals and/or
people.
If the wind energy installation is in the form of an
off-shore wind energy installation, at least that tower
section which is covered with water preferably has
opposing vibration applied to it, so that vibration of
this tower section which produces sound and disturbs
marine animals is reduced or prevented. Component
vibration may be extremely problematic, particularly in
the case of off-shore wind energy installations such as
these. This is because vibration of the tower, in
particular of that tower section which is in the water,
can lead to noise which disturbs or even drives away
marine animals, such as all types of fish.
In one particularly advantageous embodiment, one or
more sensors detects or detect component vibration
which causes sound waves. The opposing vibration is
preferably applied as a function of the component
vibration detected in this way, in a particular as a
function of the frequency and the amplitude of the
detected component vibration.
The component, such as the tower, can have opposing
vibration applied to it, whose amplitude and/or
frequency at least approximately match/matches the
amplitude of the detected component vibration, and
are/is preferably identical to it.

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One or more components of the wind energy installation,
preferably the tower, may have a vibration generator
via which the component can have opposing vibration
applied to it in order to reduce/prevent sound waves
which result from component vibration and are
disturbing to animals and/or people, which opposing
vibration is in the opposite direction to the component
vibration which produces the sound, and reduces or
prevents this component vibration.
A further wind energy installation in order to achieve
the object according to the invention has the features
of Claim 23.
According to this claim, the wind energy installation,
in particular one or more components of the wind energy
installation and preferably the tower, has or have a
vibration generator, via which the component can have
opposing vibration applied to it in order to
reduce/prevent sound waves which result from component
vibration and are disturbing to animals and/or people,
which opposing vibration is in the opposite direction
to the vibration of the component which produces the
sound, and produces or prevents this component
vibration.
In a further embodiment of the invention, the wind
energy installation has a vibration generator with
masses or mass bodies which can be moved controllably,
are directly or indirectly connected to the component
and can be moved controllably relative to the component
in order to produce the vibration.
The vibration generator may have a plurality of mass
bodies in the interior of the tower, which mass bodies
can be moved controllably relative to the tower and can
be moved on a plane which runs at least approximately
horizontally.

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Each movable mass body is advantageously guided along a
straight line which runs at least approximately from
the tower centre to the tower edge area.
In one particular embodiment, the movable mass bodies
are distributed approximately in the form of a star
over the tower cross section.
In order to detect component vibration, one or more
sensors are arranged on the component, in particular on
the tower, in order to detect this vibration.
Those components of the present wind energy
installation, in particular the active oscillation
damper and/or the vibration generator and/or the
sensors for detection of oscillations and/or vibration,
which can be controlled and/or regulated, can be
controlled and/or regulated via one or more suitable
control and/or regulation devices. Furthermore, the
methods which have been described in the context of
this application can be implemented by means of
suitable control and/or regulation devices.
Finally, in a further embodiment, the wind energy
installation may have a standby power supply set. In
this case, the standby power supply set is used to
supply one or more, and preferably all, of the
electrical power components in the present wind energy
installation with electrical power and energy in the
event of a power supply system failure, in particular
one or more control and/or regulation devices and/or
sensors, for example the sensors for detection of
oscillations and/or vibration, and/or the vibration
generator and/or the active oscillation damper.
Further features of the present invention are specified
in the attached dependent claims, in the following
description of specific exemplary embodiments of the
present invention, and in the attached drawings, in

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which:
Figure 1 shows a side view of a wind energy
installation according to the invention, with
an active oscillation damper,
Figure 2 shows a side view of a rotor of a wind energy
installation with an additional mass,
Figure 3 shows a side view of a further embodiment of
a wind energy installation according to the
invention, specifically an off-shore wind
energy installation with a vibration
generator arranged in the tower interior, and
Figure 4 shows a horizontal cross section through the
tower of the wind energy installation shown
in Figure 3.
Figure 1 illustrates a wind energy installation 10
which has a pod 16, which is arranged at the top of the
tower, at the upper end of a vertical tower 14 which is
arranged on a horizontal foundation 12. As those
skilled in the art in this field will know, a wide
range of embodiments are feasible for the detailed
design of a tower for a wind energy installation. The
invention is not, of course, restricted to the
truncated-conical form of the tower 14 described in the
drawing.
A rotor 18 is arranged at an end of the pod 16 facing
the wind and has a hub 20. Three rotor blades 22 are
connected to the hub 20, with the rotor blade roots of
the rotor blades 22 being inserted into corresponding
openings in the hub 20, and being connected to the hub
20 in a known manner.
The rotor 18 rotates about an axis which is inclined
slightly upwards with respect to the horizontal. As

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soon as wind strikes the rotor blades 22, the rotor 18
is caused to rotate together with the rotor blades 22
about the rotor axis. The movement of the rotor axis is
converted to electrical power by a generator which is
arranged within the pod. The rotor blades 22 cover a
circular area during rotation. The positions of the
rotor blades 22 with respect to the wind can be varied
individually, that is to say the incidence angles of
the rotor blades 22 with respect to the wind can be
adjusted, by means of an adjustment device which is not
illustrated but is known to those skilled in the art in
this field.
The basic design of the wind energy installation 10
with an at least approximately horizontal rotor axis is
known from the prior art, and it will therefore not be
described in detail.
The reference symbol 1 in Figure 1 in each case denotes
a detail of the wind energy installation 10, which is
illustrated enlarged in the right-hand upper section of
Figure 1. This shows an active oscillation damper 24,
as is arranged in the interior of the tower 14 and of
the pod 16. The active oscillation damper 24 has two
coaxial shafts 26, 28, which are arranged vertically
one above the other. The upper shaft 26 is caused to
rotate by a motor 30. The lower shaft 28 is caused to
rotate by a motor 32. One end of a rigid arm 34 is
connected to the upper shaft 26 such that they rotate
together. A mass or a weight 36 is arranged at the
opposite end of the rigid arm 34.
A rigid arm 38 with a corresponding weight or mass 40
at the end is arranged in a mirror-image form with
respect to the rigid arm 34 and the weight 36 on the
lower shaft 28.
The upper shaft 26 and the lower shaft 28 contrarotate,
so that the weights 36 and 40 are each arranged once on

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one and the same vertical plane per complete
revolution, that is to say they point in the same
direction. In this position, the impulses of the
weights 36, 40 are added so that, overall, a
corresponding movement impulse is exerted on the tower
14, which is connected to the active oscillation
damper, or on the pod 16, which is connected to the
oscillation damper 24.
The rotation frequency of the individual weights 36, 40
is matched to the frequency at which the rotor blades
22 rotate. As can be seen in the drawing, a rotor blade
22 which is pointing downwards is passing the tower,
that is to say the rotor blade is passing the tower 14
at the instant shown in the drawing. In a front view of
the wind energy installation 10, which is not
illustrated, this rotor blade 22 will at least
partially cover the upper area of the tower 14. During
this coverage phase, the forces which act on this rotor
blade 22 are less than during the rest of its rotation
phase. A forward impulse which is represented by the
arrows, that is to say to the left in the drawing, is
exerted in a corresponding manner on the rotor blade
22, and thus on the pod 16 and the tower 14.
In order to compensate for this movement impulse, the
rotation frequencies of the weights 36, 40 of the
active oscillation damper 24 are matched such that they
are located on the common vertical plane when the rotor
blade 22 completes its pass by the tower. In a
corresponding manner, while passing by the tower,
opposing impulses are initiated by the active
oscillation dampers 24, as illustrated by the arrows
pointing to the right in the drawing. This provides
compensation for the movements.
Since the compensation must be carried out for each
rotor blade whenever it passes the tower, the frequency
at which the weights 36, 40 rotate is three times as

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high as the rotation frequency of the rotor blades 22.
As those skilled in the art will be aware, widely
differing types of other active oscillation dampers are
feasible within the scope of the invention, and can be
arranged in or on the tower 14, the pod 16 or the rotor
18, or the rotor blades 22. The same applies to passive
oscillation dampers, which can be positioned in or on
the rotor blades 22.
By way of example, Figure 2 shows two different
positions at which additional masses or weights 42 can
be arranged in the rotor blade 22. These masses 42
result in a change to the natural oscillation behaviour
of the rotor blade 22, that is to say the natural
frequency, with respect to the natural frequency that
is predetermined by the given physical shape. This
change in the natural frequency or in the natural
oscillation behaviour is used to ensure that the
resultant natural oscillation frequency and the
resultant natural oscillation behaviour of the system
comprising the additional mass 42 and the rotor blade
22 is away from the excitation frequencies to be
expected for the installation in the predetermined
conditions. This prevents the rotor blades 22 from
starting to oscillate in a damaging manner.
Figure 3 illustrates an off-shore wind energy
installation 10. Components having the same function
are provided with the same reference symbols as in the
case of the wind energy installation shown in Figure 1.
A pod 16 is arranged at the top of the tower, at the
upper end of a vertical tower 14. The tower 14 is
anchored in the sea bed in a manner that will not be
described in any more detail, and water 13 flows around
it. As in the case of the wind energy installation 10
in Figure 1, a rotor 18, which has a hub 20, is
arranged at the end of the pod 16 facing the wind.

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Three rotor blades 22 are connected to the hub 20, with
the rotor blade roots of the rotor blades 22 being
inserted in corresponding openings in the hub 20, and
being connected to it in a manner known per se. The
rotor 18 rotates about an axis which is inclined
slightly upwards with respect to the horizontal. As
soon as wind strikes the rotor blades 22, the rotor 18
together with the rotor blades 22 is caused to rotate
about the rotor axis. The movement of the rotor axis is
converted to electrical power by a generator which is
arranged within the pod 16. The position of the rotor
blades 22 with respect to the wind can be varied
individually, that is to say the incidence angle of the
rotors blades 22 with respect to the wind can be
adjusted, by means of an adjustment device.
A horizontally running helicopter landing platform 44
is arranged at the top of the pod 16. A further
helicopter landing platform 46 is arranged in the same
manner in the lower area of the tower 14. The platforms
44, 46 are attached to the wind energy installation 10
via suitable connecting and supporting structures. A
helicopter, which is not illustrated, can land both on
the platform 44 and on the platform 46. Once the
helicopter has landed on one of the platforms 44 or 46,
any required maintenance or repair measures can be
carried out on the lower and/or upper parts of the wind
energy installation 10.
The basic design of the off-shore wind energy
installation 10 with an at least approximately
horizontal rotor axis is known from the prior art, so
that this will not be described in detail.
A vibration generator 48, which is illustrated only
schematically in Figure 3, is arranged in the interior
of the tower 14. The vibration generator 48 makes it
possible to compensate for oscillations, specifically
vibration of the tower, at a frequency which is within

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the range that is audible for marine animals. Without
the compensation according to the invention, vibration
such as this can lead to the production and propagation
of sound waves which are damaging to marine animals.
Structure-borne sound sensors and/or vibration sensors,
which are not illustrated, in this case detect that
vibration of the tower or of other components of the
wind energy installation 10 which is within the
frequency range that is audible for marine animals,
such as dolphins 50. This vibration, and/or the
parameters which characterize this vibration, is or are
measured, such as the frequency and the amplitude of
the vibration. The measured vibration may, of course,
comprise vibration at different frequencies being
superimposed. The individual frequencies can in this
case be filtered out by means of suitable analysis
methods, such as Fourier analysis.
Opposing vibration is applied to the tower by means of
the vibration generator 48, as a function of the
measured vibration. The relative parameters for the
opposing vibration are in this case selected and
controlled such that the opposing vibration counteracts
the component vibration producing the sound and cancels
it out, or at least reduces it.
Figure 4 shows a horizontal cross section through the
tower 14. One particular embodiment of a vibration
generator 48 arranged in the interior of the tower can
be seen well.
The vibration generator 48 has mass bodies 52 which are
distributed in the form of a star over the tower cross
section. Each mass body 52 is guided in each case along
an approximately radially running guide, specifically a
guide rod 54, such that it can be moved controllably
along the horizontal plane, to be precise in the form
of a carriage which can be moved along the guide rod

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54.
In this case, each of the guide rods 54 is connected at
one end at the tower centre to a central holding ring
56, specifically by being attached to it. In a
corresponding manner, the ends of the guide rods 54 are
arranged distributed around the holding ring 56 in the
circumferential direction. At the respective other end,
each guide rod 54 is connected to an outer connecting
ring 58, and is attached to it.
The central holding ring 56 has a considerably smaller
diameter than the connecting ring 58. Both the outer
connecting ring 58 and the central holding ring 56 are
arranged concentrically with respect to the tower wall
60, which has a circular cross section. In this case,
the connecting ring 58 runs at a small radial distance
from the tower wall 60, that is to say its diameter is
only slightly smaller than the diameter of the tower
wall 60. The connecting ring 58 is firmly connected to
the tower wall, in particular by means of screws, via
connecting webs 62. The central holding ring 56 may be
supported in the ground, in particular the tower
foundation, for example by means of suitable supporting
structures.
Two guide rods 54, and thus two mass bodies 52 in each
case, are each arranged in the same radial direction.
These guide rods 54, which are located opposite with
respect to their arrangement on the holding ring 56,
accordingly include an angle a of 180 with one
another. All of the guide rods 54 include identical
angles with respectively adjacent guide rods, with the
sum of all the individual angles being 360 .
The individual mass bodies 52 can be moved along the
respective guide rods 54 in the direction of the tower
centre, that is to say as far as the holding ring 56,
and in the opposite direction as far as the connecting

CA 02566376 2006-11-01
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ring 58, by means of drive means, which are not
illustrated explicitly, for example electric motors as
well as corresponding transmission means. When these
linear movements of the mass bodies 52 are carried out
with positive or negative acceleration, that is to say
the mass bodies 52 are accelerated or braked, forces
are transmitted to the tower 14. Vibration can be
applied to the tower 14 by an appropriate time sequence
of suitable forward and backward movements of the mass
bodies 52, that is to say with the acceleration and
braking processes being controlled in a suitable
manner.
During an accelerated movement of one of the mass
bodies 52 towards the holding ring 56, or in the case
of a braking process during a movement towards the
connecting ring 58, forces are transmitted to the tower
wall 60, which are directed radially outward, that is
to say away from the tower centre. During the opposite
acceleration and braking processes, forces are likewise
transmitted to the tower wall 60, but in the direction
towards the tower centre.
In the simplest case, the braking processes take place
directly adjacent to the holding ring 56 or the
connecting ring 58, by the mass bodies 52 being stopped
there by coming into contact with appropriate stops 64.
Dampers, for example oil-pressure dampers, can be
provided on the holding ring 56, and brake a movement
of the mass bodies towards the holding ring 56 or the
tower centre.
However, alternatively or additionally, it is also
feasible to provide controllable braking means, which
can also be used to brake the mass bodies 52 during the
course of their movements along the guide rods 54.
All of the mass bodies 52 are controlled independently
of one another by an appropriate control device, in

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particular being accelerated and/or braked at
adjustable times, for time periods which are likewise
adjustable. The control device processes the signals
which originate from the sensors, and controls the mass
bodies 52 as a function of these signals. In addition
to other parameters, it is possible to adjust the
magnitudes of the acceleration and/or braking
characteristic values as well as the frequency at which
the respective acceleration and braking processes are
carried out.
Superimposed vibration movements at an adjustable
frequency and with an adjustable deflection, and which
counteract the component-dependent measured vibration,
can be applied to the tower by suitable superimposition
and control of the individual acceleration and braking
movements of the mass bodies 52. It is thus even
possible to generate complex vibration movements.
As those skilled in the art will know, there are a wide
range of options for the physical form of a vibration
generator according to the invention. The invention is
accordingly not restricted to the exemplary embodiments
mentioned above.

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List of reference symbols:
10 Wind energy installation 60 Tower wall
12 Foundation 62 Connecting web
13 Water 64 Stop
14 Tower
16 Pod
18 Rotor
Hub
22 Rotor blade
24 Active oscillation damper
26 Upper shaft
28 Lower shaft
Motor
32 Motor
34 Rigid arm
36 Weight
38 Rigid arm
Weight
42 Mass
44 Landing platform
46 Landing platform
48 Vibration generator
Dolphins
52 Mass body
54 Guide rod
56 Holding ring
58 Connecting ring

Dessin représentatif