Note: Descriptions are shown in the official language in which they were submitted.
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Method for de-icing a rotor blade of a wind turbine
Description
The invention relates to a method for de-icing a rotor
blade of a wind turbine, wherein an air stream is
conducted through the rotor blade by way of a fan,
wherein the air stream is conducted in a circuit by way
of an air-guiding system and, furthermore, the air
stream is heated by way of a heating device.
Rotor blade de-icing devices of wind turbines, and
methods for de-icing a rotor blade of a wind turbine,
are basically known. In this regard, reference is made
to the applicant's EP 2 585 713 Bl.
In the case of the known method for de-icing a rotor
blade of a wind turbine, the rotor blade has a first
and a second duct within the rotor blade for conducting
an air stream, wherein the air stream comprises a
heated air stream which is introduced into the first
duct and which flows at least in sections in a
direction from the rotor blade root to the rotor blade
tip in a predefinable flow guide and which, for the
purposes of de-icing at least a section of the rotor
blade, flows along at least a part of an outer wall of
the rotor blade.
It is an object of the present invention to provide an
improved and efficient method for de-icing a rotor
blade of a wind turbine, or for de-icing the rotor
blades of a wind turbine.
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Said object is achieved by means of a method for de-
icing a rotor blade of a wind turbine, wherein an air
stream is conducted through the rotor blade by way of a
fan, wherein the air stream is conducted in a circuit
by way of an air-guiding system and, furthermore, the
air stream is heated by way of a heating device, which
method is refined in that a fraction of the air stream
that is conducted in the circuit is removed from the
circuit.
By means of the method according to the invention, it
is ensured, in an efficient manner, that the
corresponding rotor blade is de-iced, wherein
preferably, the air stream is conducted by way of an
air-guiding system in the rotor blade to the locations
which are to be preferentially de-iced. For this
purpose, a rotor blade de-icing device of a wind
turbine is preferably provided, wherein the wind
turbine has a rotor with at least one rotor blade
attached to a hub, wherein the rotor blade de-icing
device has a heating device, a fan and an air-guiding
system.
The air-guiding system preferably has a first duct,
which conducts an air stream in the direction of a
rotor blade tip, and a second duct, which conducts the
air stream in the direction of the hub. The air stream
that is conducted in the direction of the rotor blade
tip is preferably an air stream that has been heated by
the heating device. The air stream that is then
conducted back is preferably a cooled air stream. The
cooling arises in particular as a result of a release
of heat to the rotor blade external material, in order
to melt ice adhering thereto. Here, the ducts may
preferably be of insulated form in sections in order
that the least possible heat losses arise at locations
at which the rotor blade does not necessarily have to
be de-iced. It is preferable for the in particular
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heated air stream to flow along the inner wall of a
rotor blade nose, specifically preferably in the front
third of the rotor blade length, specifically in the
region of the rotor blade tip.
A substantially closed air-guiding system is preferably
provided. The air-guiding system ensures that the air
situated in the system is conducted in the circuit such
that cooled but still slightly heated recirculated air
is heated again, whereby less heating power is
required.
The air-guiding system has, in particular, the smallest
possible volume in order to also keep the heating power
as low as possible. For this purpose, provision is
preferably made for those regions of the rotor blade
which are at greater risk of icing to be heated in
targeted fashion. These are in particular the nose
region of the outer half or outer third of the rotor
blade toward the rotor blade tip. It is preferable for
substantially 40% of the outer part of the rotor blade
toward the rotor blade tip to be heated. Furthermore,
provision is preferably made for at least the warm-air
supply, or a part of the warm-air supply, to be of
insulated form.
It is preferable for an opening, which is in particular
of predefinable size, to be provided on a pressure side
of the fan, in particular for the continuous discharge
of air out of the rotor blade de-icing device.
Through the provision of the opening, it is possible
for a fraction of the air stream that is conducted in
the circuit to be removed from the circuit. It is
preferable for less than 10%, in particular less than
6%, in particular less than 4%, in particular less than
2%, of the amount of air conducted in the circuit to be
removed from the circuit.
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By means of this measure, a part of the air, including
any gas released from the rotor blade, air moisture and
any dust from the rotor blade, is blown out of the
circuit. This firstly gives rise to a pressure
reduction in the air circuit, and secondly, ice is also
prevented from being able to accumulate within the
rotor blade, for example at the rotary leadthrough.
The above measure is preferably enhanced in that, in a
suction region of the air-guiding system in a rotor
blade interior, there is provided an opening for the
introduction of air from the rotor blade interior into
the air-guiding system. Continuous purging of the rotor
blade interior is made possible in this way.
In the context of the invention, a circuit is to be
understood in particular to mean that air is conveyed
from the rotor blade hub in the direction of the rotor
blade tip and from the rotor blade tip back to the
rotor blade hub again, before then being conducted to
the rotor blade tip again, etc. In the case of such a
substantially closed system, the residual heat of the
air stream recirculated to the rotor blade hub, which
preferably still has residual heat greater than the
ambient heat, can be utilized further, such that highly
efficient de-icing is possible. It is thus possible,
for example, for air in a first duct, or an air stream
in a first duct, to be conducted from a rotor blade
root or rotor blade hub to the rotor blade tip, and, in
the region of the rotor blade tip, proceeding for
example from the middle of the rotor blade length, to
be split up, in accordance with the air stream, into a
component which is conducted further along the
longitudinal axis toward the rotor blade tip and a
component which is conducted transversely with respect
thereto in order to conduct a warm air stream to the
rotor blade nose. In the region of the rotor blade
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nose, where most ice accumulates, the warm air stream
is cooled, and is correspondingly conveyed in cooled
form from the rotor blade tip, or the region toward the
rotor blade tip of the rotor blade, through a second
duct in the direction of the rotor blade root again.
The conveyed air stream is thus conducted in the
circuit in an air-guiding system. Said circuit also
includes a fan and a heating device, for example in the
form of a heating register.
In the context of the invention, a rotor blade nose is
to be understood in particular to mean a blade leading
edge.
It is preferable for fresh air to be added to the
circuit. This also means in particular that fresh air
is introduced into the circuit. The fresh air may be
introduced for example from outside the rotor blade, in
particular via the hub, or from the interior of the
rotor blade. Provision may furthermore be made for the
air supplied to the circuit to be filtered. In the
context of the invention, fresh air is to be understood
to mean fresh air added, from outside the air stream
conducted in the circuit, to the air stream. Fresh air
is preferably introduced into the rotor blade from
outside the rotor blades, in particular via the hub.
It is preferable for an opening through which fresh air
can be introduced into the rotor blade interior to be
provided in a partition of the rotor blade. A
corresponding filter is preferably provided in order to
filter the fresh air before it is introduced into the
rotor blade.
Some of the provided openings, or all of the provided
openings, may preferably be closable and/or adjustable
in terms of their diameter. This is preferably realized
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during the operation of the method for de-icing the
rotor blade.
Through the provision of a further opening in a
partition of the rotor blade and the introduction of
fresh air, the concentration of gases that are harmful
to health in the blade interior can be continuously
reduced.
It is preferable for a first air filter to be provided
in the first duct and/or for a second air filter to be
provided in the second duct. This prevents dust
particles in the interior of the rotor blade, which
dust particles were created during the production of
the rotor blade or during operation or are possibly
still being created, from being deposited on heating
elements of the heating device, whereby the risk of
fire or explosion upon activation of the heating device
is eliminated. Furthermore, mechanical protection for
the heating elements, for example, can be realized in
this way. The heating device is preferably a heating
register.
The amount of fresh air introduced into the circuit, in
particular during the method for de-icing a rotor
blade, is preferably adjustable.
A refinement of the method is particularly preferable
in which, before and/or after the heating of the air
stream by means of the heating device, the air stream
is conducted in the circuit in particular for a
predefinable time. This means in particular that the
air stream is conducted in the circuit without the
supply of further heating energy. Efficient
dehumidification of the system is realized in this way.
Said method step is preferably performed with
corresponding partial deaeration, that is to say a
discharge of a fraction of the air stream conducted in
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the circuit out of the circuit, and possibly
additional, in particular active, aeration or addition
of fresh air to the circuit. A dehumidification is
efficient in particular if the air stream continues to
be conducted in the circuit after heating of the air
stream. This is because heated air can absorb a greater
amount of air moisture, and furthermore, water or
molten ice deposits can be removed from the air-guiding
system.
It is preferable if, before the heating of the air
stream, temperature sensors arranged in the air stream
are checked with regard to functionality. Here, it is
assumed in particular that the air stream, before the
heating of the air stream, leads to a constant uniform
temperature in the entire air-guiding system, in
particular if the air stream has been conducted through
the circuit multiple times. In this way, it is then
possible for the temperature sensors to be checked with
regard to plausibility. Said temperature sensors should
specifically measure substantially the same temperature
if the sensors are working correctly. The check of the
functionality of the temperature sensors is thus
preferably performed after the non-heated air stream
has been conducted through the circuit for a
predefinable time.
The method for de-icing the rotor blade is preferably
performed while the rotor blade is arranged leeward of
a tower of the wind turbine. In this way, damage to the
wind turbine as a result of falling ice is prevented.
This is performed in particular in the presence of a
corresponding wind strength, which is predefinable. The
method for de-icing the rotor blade is preferably
performed only above a predefinable wind strength.
The rotor blade position during the de-icing process is
preferably such that the blade leading edge is arranged
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leeward. In this way, the heated blade leading edge is
turned out of the wind, which leads to more efficient
and faster de-icing.
It is preferable for the rotor blade or the rotor with
the corresponding rotor blades to track the wind
direction, such that, during the de-icing process, the
rotor blade is in any case arranged leeward of the
tower of the wind turbine.
A rotor of the wind turbine, comprising at least three
rotor blades, is preferably positioned such that at
least two rotor blades point downward or are arranged
below the horizontal, wherein an angular adjustment of
at least one rotor blade is performed in order to
substantially maintain the position of the rotor. It is
ensured in this way that the two rotor blades which are
to be de-iced possibly simultaneously or at least
partially in succession also continue to point downward
during the de-icing process, such that ice which falls
off does not damage the wind turbine. In the case of a
wind turbine having two blades, a rotor blade that is
to be de-iced can point downward, or alternatively, it
is possible for the rotor blades to be arranged in the
horizontal and for one or both rotor blades to be de-
iced. Correspondingly, in the case of wind turbines
having more than three rotor blades, the rotor blades
to be de-iced should, during the de-icing process, be
arranged in the horizontal or below the horizontal.
The method is highly efficient if two rotor blades are
de-iced such that, after the de-icing of a first rotor
blade, a heated air stream is conducted out of the
first rotor blade into a second rotor blade.
It is preferably the case that, before the introduction
of the heated air stream into the second rotor blade, a
non-heated air stream is conducted in the second rotor
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blade in the circuit via a further air-guiding system,
and a fraction of the air stream that is conducted in
the circuit is removed from the circuit. This
preferably also serves for the calibration or checking
of the functionality of the temperature sensors in the
second rotor blade and/or for the dehumidification of
the air contained in the rotor blade. The corresponding
measures that have been performed in the first rotor
blade or in the rotor blade as described above may also
be performed in the second rotor blade for de-icing
said rotor blade.
The duration of the de-icing process and/or the amount
of heat supplied are/is preferably predefined in a
manner dependent on at least one detected starting
condition. In the context of the invention, a starting
condition is to be understood in particular to mean a
temperature of the air stream in the interior of the
rotor blade, in particular in the air-guiding system.
The temperature during the conducting of the air stream
in the circuit preferably means the temperature without
the air stream being heated, wherein the air stream is
conducted in the circuit for a predefinable time.
Furthermore, a wind speed, a wind direction, an ambient
temperature and/or an air humidity may be understood as
starting conditions. The duration of the de-icing
process and/or the supplied amount of heat are/is
preferably predefined in a manner dependent on multiple
detected starting conditions.
It is preferably the case that, during the heating of
the air stream, closed-loop control of the temperature
in the feed line, in particular in the heating device,
is performed. In this way, for a system-limited maximum
power, highly efficient and fast de-icing can be
performed.
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The air stream is preferably dehumidified by way of an
additional dehumidification device. For example, for
this purpose, a cooled surface may be provided on which
air moisture condenses, which air moisture is then
correspondingly discharged from the system and from the
wind turbine.
To be able to thaw and shed ice adhering to rotor
blades, those surfaces of the rotor blades which are to
be de-iced are heated to a temperature higher than 0 C.
The heat energy required for this purpose, and the air
stream required, are provided by preferably in each
case one rotor blade de-icing device per rotor blade.
Here, a heating device and a fan are provided,
preferably in the form of a fan-heater unit, which is
arranged within a blade root of the rotor blade and
fastened to the rotor hub.
In particular, the fan-heater unit comprises a fan, a
heating device, for example a heating register, and a
concentric double pipe in the form of a first and a
second duct for the feed and return of the air in the
air-guiding system. A counterpart to the concentric
double pipe is preferably provided, which counterpart
co-rotates with the rotor blade during the pitch
adjustment. The counterpart of the rotor blade and the
concentric double pipe of the fan-heater unit are
preferably connected to one another by way of a rotary
leadthrough.
By way of an open-loop and closed-loop controller,
which is preferably provided externally with respect to
the fan-heater unit, the heating device and the fan are
actuated and preferably also monitored. The air-guiding
system or the ventilation system in each rotor blade
is, in terms of basic principle, a closed system,
wherein provision may be made for small amounts of air
to be exchanged or replaced. In this way, the residual
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heat in the return line during the rotor blade de-icing
process is substantially maintained.
The air-guiding system preferably has a first duct,
which is designed to conduct an air stream from the
fan-heater unit in the region of the rotor blade root
to the rotor blade tip, and a second duct, by means of
which the air stream is conducted back from the rotor
blade tip to the rotor blade root.
The air volume conducted in the circuit in the air-
guiding system is preferably 6 m3 20 m3. A volume of 8
m3 to 12 m3 is particularly preferred. Said values
apply preferably in the case of blade lengths of 50 m.
In one exemplary embodiment of the rotor blade de-icing
device, between 800 m3/h and 2000 m3/h of air is
conveyed in the circuit. It is preferable for
approximately 20 m3/h to 100 m3/h of fresh air to be
added. However, the invention is not restricted to
these ranges. The stated ranges represent preferred
embodiments.
The ratio of air conveyed in the circuit to freshly
added air or fresh air is preferably between 20 and 40,
particular preferably 25 to 30.
Owing to the fixed installation of the heating device
and also of the fan or of the fan-heater unit on the
hub, the electrical energy supply does not need to be
led into the rotating part of the rotor blade, and
furthermore, in this way, adequate lightning protection
for the electrical energy supply and also for the open-
loop control device can be ensured.
By means of the concentric double pipe, which is
preferably positioned in the axis of rotation of the
rotor blade, the warm feed air is blown via an
appropriate counterpart into the duct system or the
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air-guiding system of the rotor blade, and the cooled
return line is led to the suction side of the fan
again. By means of this circuit, the heating and fan
power that is available can be utilized in an efficient
manner.
The components of the air guide or of the air-guiding
system are preferably partially of thermally insulated
form. Furthermore, in the air circuit, that is to say
in the air-guiding system, there may also be
incorporated at least one further component which, for
example, mechanically prevents a reversal of the
defined air flow. Said component may be a non-return
flap or a non-return valve.
The front blade chamber is preferably used at least
partially as a return line in order to simplify the
air-guiding system. Material can be saved in this way.
Nevertheless, in this case, the air volume that flows
through is greater. Furthermore, then, the pressure
losses in the circuit system or in the air-guiding
system are reduced, whereby the volume flow increases
and the return line temperature increases, specifically
in the case of an unchanged feed line temperature. This
can improve the heat transfer conditions.
By means of an in particular passive admixing of
ambient air, different method implementations are
possible. Here, local releases of gas in the system or
from the rotor blade material can be homogenized and
diluted with ambient air. It is preferably possible for
active ambient air admixing to be performed, wherein
here, flap open-loop control is provided actively and
in accordance with demand, by means of which the amount
of ambient air that is admixed can be adjusted.
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Furthermore, dust accumulations can be supplied to
corresponding filters, or partially released to the
ambient air.
Furthermore, it is preferable for thermal
homogenization of the air stream to take place in the
circuit in particular before the heating of the air
stream, such that sensors can be checked for
plausibility, in particular temperature sensors can be
checked for plausibility.
Furthermore, it is preferably the case that, after the
ending of the de-icing process and a deactivation of a
heating device, that is to say when there is no further
supply of heat energy into the air stream, the air
stream is preferably maintained in order to allow the
heating device to cool to substantially homogenized
system temperatures. In this way, it is preferably
possible for the system, in particular the air-guiding
system, to be correspondingly purged in order for any
contained moisture to be discharged from the system. In
this way, condensing of water in the air-guiding
system, and in particular for example at a rotary
leadthrough, is prevented, thus preventing the
possibility of condensate freezing there and causing
damage to components, for example during rotor blade
adjustment processes.
The first rotor blade to be de-iced is preferably
selected such that, after the ice has fallen off, an
imbalance of the rotor that arises assists a rotation
of the rotor in the desired manner.
An inclination sensor is preferably provided in order
to permit rotor position detection. The inclination
sensor is preferably arranged in a switchgear cabinet
for the supply to and/or open-loop control of a rotor
blade de-icing device.
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The heating time and the amount of heat imparted are
preferably defined in a manner dependent on a starting
condition, such as for example the temperature of the
air stream during the first purging process, the wind
speed, the ambient temperature or the like. The heating
time and the amount of heat imparted are preferably
adapted in a manner dependent on a present return line
temperature during the de-icing process. The heating
time may vary for example between two and five hours.
Here, the amount of heat required for the de-icing
process is preferably predefined, specifically on the
basis of calculations or estimations based on the
starting conditions. Furthermore, in this way, it is
possible to set the minimum amount of supplied heating
energy that should be used during the heating time.
It is preferable, for the adjustment of the rotor, for
rotor position detection to he performed by way of an
inclination sensor or multiple inclination sensors.
Said inclination sensor(s) may be installed in an open-
loop control device which performs open-loop control of
the de-icing process or of the de-icing method, and may
thus be positionally fixed in relation to a rotor
blade. It is preferable for a single open-loop control
device to be provided, which is fixed relative to a
rotor blade hub within a rotor blade. Said open-loop
control device preferably serves for the open-loop
control of the de-icing processes of all of the rotor
blades.
A temperature measurement is preferably performed at
different locations in the air stream. The temperature
measurement values are made available to the open-loop
control device, and open-loop control of the de-icing
process is performed with the aid of the temperature
measurement values. There are preferably further
temperature measurement sensors for example in the
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heating device and/or in the first duct, that is to say
in the feed line, which further temperature measurement
sensors ensure redundant load circuit deactivation.
Here, it may be provided that the temperature threshold
value above which redundant load circuit deactivation
is performed is higher than the temperature measurement
value which, by way of the open-loop control device,
leads for example to a deactivation of the heating
device.
It is furthermore preferable for monitoring to be
performed. In particular, it is checked whether the
electrically supplied heating energy corresponds at
least to the expected or pre-calculated amount of heat.
If this is not the case, it can for example be inferred
that the air stream has not been conducted over the
region in which it was intended to perform de-icing. In
this case, a pipe fracture, for example, may exist.
Furthermore, it is preferable for plausibility
monitoring of a return line temperature with regard to
a maximum possible temperature and a minimum expected
temperature after a heating phase to be performed. It
is preferably possible for the power demand for the de-
icing to be determined through the formation of a
difference between feed line temperature and return
line temperature, and for the determined power to be
compared with the supplied power. It can also be
checked in this way whether the de-icing method is
functioning correctly.
Redundant load circuit deactivation is preferably
provided. In the event of a corresponding fault, which
may for example be an excessively high feed line
temperature of over 65 C or over 50 C, wherein said
temperature may be predefined, it is possible for the
heating device to be deactivated by way of a redundant
temperature sensor. The excessively high feed line
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temperature preferably lies between 70 C and 85 C. The
deactivation of the heating device is preferably
performed in the event of a defect of the temperature
sensor, which measures a feed line temperature of an
open-loop control device for the open-loop control of
the heating device and/or of the fan. The redundant
sensor is a further temperature sensor which shuts off
the heating device directly in the presence of an
excessively high measurement value. For this purpose, a
main switch can be correspondingly triggered. It is
preferable, for this purpose, for the temperature
threshold above which a direct shut-off of the heating
device is provided to be higher than the temperature
threshold set by way of the open-loop control device.
Furthermore, triggering of the main switch may be
provided if a malfunction of the load circuit
deactivation is identified. This is performed for
example by way of a protective switch.
It is preferable for electronic load circuit relays to
be used for optimum assistance of the feed line
temperature closed-loop control and/or of the power
splitting between a first rotor blade to be de-iced and
a second rotor blade to be de-iced.
It is preferably provided that, during the heating or
during the heating process, the feed line temperature
is simulated and compared with the measured feed line
temperature. The feed line temperature preferably has a
PT1 characteristic.
Through the parallel or simultaneous simulation of the
feed line temperature during the heating process and
the comparison of the simulated and measured feed line
temperatures, it is possible to identify different
hardware or software faults, such as for example
whether a filter is blocked or an air path is
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constricted. Furthermore, it can be identified whether
the fan power is too low or too high, or whether the
air path or the ducts exhibit, for example, a pressure
difference loss owing to a broken line. It is also
possible to identify whether an excessive amount of
heating energy has been introduced, for example as a
result of a short circuit of an electrical load relay,
or whether heating elements of the heating device are
defective. The possible faults listed are mentioned
merely by way of example.
With the supplied electrical power, in particular the
measured inlet temperature and/or return line
temperature into the fan-heater unit, and the system
characteristics, which are determined substantially by
the energy storage behaviour and thus by the transfer
function, for example by way of the mass of the heating
register or the heating device, a simulation of the
feed line temperature is possible. With correspondingly
accurately simulatable heating devices or fan-heater
units, it may be possible to dispense with plausibility
monitoring of the feed line temperature compared with
the measured heating device temperature and/or to
dispense with a determination of the power demand by
forming the difference between feed line and return
line temperature for a comparison of the determined
powers with the supplied power.
It is preferable for the return line temperature to be
measured and to monitor whether the latter lies within
predefinable limits.
It is preferable for that fraction of the air stream
which is removed from the circuit to be discharged
between a fan and a heating device, wherein an opening
or a purging air outlet is preferably provided.
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It is preferable for the air flow rate at the purging
air outlet to be measured, wherein this is performed in
particular during maintenance, preferably without
heating of the air stream. The measurement value may
then be compared with a predefined value, and rotor
blade damage or air-guiding system damage can be
inferred in the event of an excessively large
deviation. Alternatively, a continuous air flow rate
measurement at the purging air outlet may be provided
in order to automatically detect faults.
Fault monitoring is furthermore possible by way of a
differential pressure measurement, wherein expected
pressure differences are dependent on the
configurations of openings that are used and on the
power of the fan.
It is preferably identified, on the basis of a pressure
measurement in the rotor blade, whether the rotor blade
is air-tight or whether those parts of the rotor blade
which are supposed to be air-tight are in fact so. It
is also possible, during times in which there is no
risk of icing, for example when ambient temperatures
are above freezing, for an air stream to be generated
in order to check for damage, for example leaks, of the
rotor blade.
It is preferable for the pressure of the air in the
air-guiding system to be subject to open-loop control.
This may be realized by way of the fan power and/or the
size of the openings for the inlet and outlet of the
purging air. In the case of a negative pressure being
generated in the rotor blade, no heated air can escape
at undesired locations. This leads to efficient de-
icing. Furthermore, in this way, it is possible to
prevent system-critical rotor blade parts from being
subjected to an excessively high feed line temperature
over an excessively long period of time. Furthermore,
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in this way, it is also possible for the feed line
temperature to be increased, which reduces the de-icing
duration.
Further features of the invention will become clear
from the description of embodiments according to the
invention together with the appended drawings.
Embodiments according to the invention may satisfy
individual features or a combination of multiple
features. The preferred embodiments above and/or below
may be advantageously combined with the above-stated
individual features or solutions according to the
invention.
The invention will be described below, without
restriction of the general concept of the invention, on
the basis of exemplary embodiments and with reference
to the drawings, wherein, with regard to all details of
the invention that are not discussed in any more detail
in the text, reference is made explicitly to the
drawings, in which:
figure 1 shows a schematic view of a wind turbine,
figure 2 is a schematic illustration of a rotor blade
on a hub, and
figure 3 is a schematic illustration of a rotor blade
de-icing device according to the invention.
In the drawings, identical or similar elements and/or
parts are in each case denoted by the same reference
designations, such that a repeated explanation will be
omitted in each case.
Figure 1 schematically shows a wind turbine 1. The wind
turbine 1 comprises a tower 2 on which there is
provided a nacelle 3. Three rotor blades 5 are arranged
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on a hub 4. The wind turbine is of horizontal-axis
type. The horizontal axis simultaneously also
constitutes the axis of rotation of the rotor 10,
formed from the hub 4 and the rotor blades 5, of the
wind turbine 1. In figure 1, the axis of rotation
points substantially perpendicularly out of the plane
of the drawing.
Each rotor blade 5 extends from a rotor blade root 6,
which is arranged on the hub 4, to a rotor blade tip
45.
In the case of wind turbines 1 installed in cold
regions with an atmosphere that gives rise to icing,
accumulations of ice commonly occur on the rotor blade,
specifically with such intensity that the performance
of the installation is considerably reduced, which in
the extreme case can lead to a shut-down of the
installation. To ensure the operation of the wind
turbine, provision is made for the rotor blades 5 to be
de-iced by way of corresponding measures.
For this purpose, a rotor blade de-icing device of a
wind turbine 1 is proposed, which rotor blade de-icing
device, as schematically indicated in figure 2,
conducts air or an air stream 13 substantially in a
circuit in an air-guiding system 9, which air or air
stream is heated in the vicinity of the hub 4 or in the
vicinity of the rotor blade root or in the rotor blade
root 6 and is conducted to the rotor blade tip 45 in a
first duct 11. In the tip region of the rotor blade 5,
the warm air passes into a second duct 12 which is
arranged in the vicinity of the blade leading edge 7.
The first duct 11 is arranged further toward the
trailing edge 8 of the rotor blade 5.
To conduct the heat energy to the locations at which
the icing is most likely or most intense, the first
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duct 11 is equipped with insulation 16 so as to conduct
the air stream 13 in the direction of the rotor blade
tip 45 with the least possible heat losses. In the
region of the rotor blade tip 45, the air stream 13 is,
preferably by way of transverse flows 15, conducted in
the direction of the rotor blade leading edge 7, around
the blade leading edge, which exhibits the greatest
icing tendency, specifically in particular that part of
the rotor blade leading edge which is arranged toward
the rotor blade tip 45. In this way, ice is
correspondingly thawed and can fall off. The somewhat
cooled air is conveyed, as a cooled air stream 14, back
to the heater (not illustrated in figure 2). On the
path to there, the second duct 12 is equipped with
insulation 17 in order that the residual heat in the
cooled air stream is not lost at locations where it
does not need to be released.
Figure 3 schematically shows a rotor blade de-icing
device of a wind turbine 1 according to the invention.
The rotor blade 5 is attached to the hub 4, which is
merely indicated. Also connected positionally fixedly
to the hub is a heating device 21, which may be in the
form of a heating register, and the fan 22.
By means of the heating device 21 and the fan 22, warm
air is conducted through the first duct 11, via the
rotary leadthrough 25, in the direction of the rotor
blade tip 45. The warm air is conducted onward, having
been filtered by way of a filter 27, in the direction
of the rotor blade tip 45. A corresponding air stream
13 is schematically indicated here. The arrows are
intended to illustrate the warm-air flows which are
conducted into a blade heating chamber 20 which is
arranged at the rotor blade nose or rotor blade leading
edge in the region of the rotor blade tip 45.
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Cooled air 14 or a cooled air stream 14 passes back via
an air filter 27' and the second duct 12 in the
direction of the fan 22 via the rotary leadthrough 25.
The air stream that is conducted in the circuit
comprises the air stream 13 and the air stream 14.
For corresponding open-loop or closed-loop control of
the amounts of air and/or the amount of heat, multiple
temperature sensors are provided. For example, the
temperature sensor 32, which measures the temperature
of the returned air, and the temperature sensors 33 and
34. The temperature sensor 34 measures the heating
device temperature or the heating register temperature,
and the temperature sensor 33 measures the feed line
temperature. The feed line temperature is the
temperature prevailing immediately downstream of the
heating device as viewed in the flow direction of the
air stream. The measurement values of the sensors 32,
33 and 34 are provided to an open-loop control unit 44
(not illustrated) for the open-loop and/or closed-loop
control of the heating device 21 and the fan 22.
As a safety measure, there is also provided a
temperature sensor 35 which, for example in the
presence of an excessively high feed line temperature,
can directly shut off the heating device 21.
Correspondingly, the heating device can also be shut
off by way of the temperature sensor 36, by means of
which the heating device temperature is measured.
Furthermore, on the pressure side of the fan 22, there
is provided a small opening 23 via which a small volume
flow of the air that is conducted in the circuit can be
discharged via an air line or a purging air line 24.
Furthermore, an opening 28 may be provided on the
suction side of the air-guiding system 9 or at the
inlet side of the filter 27' in order to draw off air
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from the rotor blade interior and thus permit a removal
of undesired gases from the rotor blade interior.
The system may for example be operated with a negative
pressure overall.
Furthermore, in the partition 26 in which the rotary
leadthrough 25 is arranged, there may be provided an
opening 31 via which fresh air, which passes into the
rotor blade interior for example via the hub 40,
passes, having been filtered by way of a filter 30,
into the rotor blade interior to the left of the
partition 26 in figure 3. Permanent purging is ensured
in this way.
By means of the illustrated features from figure 3, the
method for de-icing a rotor blade of a wind turbine can
be implemented in an efficient manner. It is optionally
also possible for a dehumidifier 50 to be provided in
order to dehumidify the air stream 13 that is conducted
in the circuit in the air-guiding system. Said
dehumidifier may for example be a cooling device which
cools the duct 11 over a certain distance, wherein the
condensate is collected and removed from the rotor
blade, for example by way of a pump or by gravity, via
a hose (not illustrated).
Furthermore, it may be provided that the inlet and
outlet openings by means of which a fraction of the air
stream 13 that is conducted in the circuit is removed
from the circuit, or fresh air can be supplied, is of
variable cross section or even closable. In this way,
it is possible for the flow rate of the air stream 13
conducted out of the circuit, and/or the flow rate of
the fresh air introduced into the circuit, to be
adjusted in targeted fashion during operation.
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It is preferable for warm exit air that is removed from
the circuit to be directed toward a pitching gearbox or
a drive system of the rotor blade.
All of the stated features, even the features that
emerge only from the drawings and also individual
features that are disclosed in combination with other
features, are regarded as being essential to the
invention individually and in combination. Embodiments
according to the invention may be satisfied by
individual features or a combination of multiple
features. In the context of the invention, features
referred to using "in particular" or "preferably" are
to be understood as optional features.
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List of reference designations
Wind turbine
2 Tower
3 Nacelle
4 Hub
5 Rotor blade
6 Rotor blade root
7 Blade leading edge
8 Blade trailing edge
9 Air-guiding system
10 Rotor
11 First duct
12 Second duct
13 Air stream
14 Cooled air stream
15 Transverse flow
16 Insulation
17 Insulation
20 Blade heating chamber
21 Heating device
22 Fan
23 Opening, pressure side
24 Purging air line
25 Rotary leadthrough
26 Partition
27, 27' Filter
28 Opening, suction side
Filter
30 31 Opening, blade partition
32 Temperature sensor
33 Temperature sensor
34 Temperature sensor
Temperature sensor with hardware deactivation
35 36 Temperature sensor with hardware deactivation
37 Bracket
38 Rotor blade interior
Hub connection
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45 Rotor blade tip
46 Axis of rotation
50 Dehumidifier
