CA2914727A1

CA2914727A1 - Rotor blade deicing

Info

Publication number: CA2914727A1
Application number: CA2914727A
Authority: CA
Inventors: Sascha Erbsloh
Original assignee: Individual
Current assignee: Senvion GmbH
Priority date: 2013-06-19
Filing date: 2014-03-17
Publication date: 2014-12-24
Anticipated expiration: 2034-03-17
Also published as: DK3011172T3; CA2914727C; CN105683566B; CN105683566A; ES2821788T3; DE102013211520A1; EP3011172B1; WO2014202164A1; EP3011172A1

Abstract

The invention relates to a rotor blade (10) of a wind turbine, the rotor blade (10) extending from a blade root (11) to a blade tip (12) and having a cavity (31), in which a web (13)is arranged in the longitudinal extent of the rotor blade (10), separating a first region (19) of the rotor blade (10), comprising a rotor blade nose (15), from a second region (20) of the rotor blade (10), comprising a trailing edge (16). The invention also relates to a method for deicing a rotor blade (10) of a wind turbine.
The invention is distinguished by the fact that a thermally insulated channel (18) is arranged in the first region (19) of the rotor blade (10) on the web (13), in order to conduct hot air (24) in the direction of the blade tip (12), openings (26), which are formed in such a way as to direct the hot air (24) to the rotor blade nose (15), being provided in the channel (18), with a return of the hot air to the blade root (11) taking place in the first region (19) of the rotor blade (10).

Description

1 , Rotor blade deicing Description The invention relates a rotor blade of a wind turbine, the rotor blade extending from a blade root to a blade tip and having a cavity, in which a web is arranged in the longitudinal extent of the rotor blade, separating a first region of the rotor blade comprising a rotor blade nose from a second region of the rotor blade comprising a rotor blade trailing edge.
The invention also relates to a deicing system for a wind turbine. Moreover, the invention relates to a method for deicing a rotor blade of a wind turbine.
During the operation of wind turbines, there is the problem at cold sites that the rotor blades ice up, which leads on the one hand to a deterioration in the aerodynamics, and with that the efficiency, of the rotor blades and on the other hand to undesired loading problems.
For this reason, systems by means of which the rotor blades can be heated in order to provide deicing have been developed.
DE 10 2010 030 472 Al discloses a rotor blade of a wind turbine with a first and a second channel running inside the rotor blade for directing an air stream through. Also provided is a method for deicing a rotor blade of a wind turbine. The rotor blade according to DE 10 2010 030 472 Al has a separating device, which separates the channels from one another, so that the first channel is arranged on a first side of the separating device, toward the pressure side of the rotor blade, and the second channel is arranged on a second side of the separating device, toward the suction side of the rotor blade. The method described 1 %

- 2 -provides that, at least in portions of the rotor blade, the flow velocity of the air stream provided in the first channel and the second channel is prescribed.
The fundamental problem with hot air systems is that a significant proportion of the thermal energy is lost in the region near the blade root and, as a result, deicing in the outer region of the blade, in particular in the region of the blade tip, is only made possible with great expenditure of energy and mass flows. Since the material of rotor blades, that is usually glass-fiber reinforced plastic, does not withstand all that high a temperature, and consequently the temperature of the heating air is limited, and moreover pressure losses increase disproportionately with the mass flow, some electrical systems have been developed. These however have problems with respect to the lightning protection concept of a rotor blade. Moreover, they involve greater maintenance expenditure, since corresponding heating foils are typically adhesively attached to the outside of the rotor blades and are correspondingly exposed to the effects of the weather.
The object of the present invention is to provide an effective and low-maintenance deicing system, the intention being in particular to provide a rotor blade of a wind turbine and a method for deicing a rotor blade of a wind turbine that makes more efficient deicing of the rotor blade possible.
This object is achieved by a rotor blade of a wind turbine, the rotor blade extending from a blade root to a blade tip and having a cavity, in which a web is arranged in the longitudinal extent of the rotor blade, the web separating a first region of the rotor blade, comprising a rotor blade nose, from a second region of the rotor blade, comprising a rotor blade trailing edge, which rotor blade is developed in such a way that a thermally insulated channel is arranged in the first

- 3 -region of the rotor blade on the web, in order to conduct hot air in the direction of the blade tip in an air stream, openings, which are formed in such a way as to direct hot air to the rotor blade nose, being provided in the channel, with a return of the hot air to the blade root taking place in the first region of the rotor blade. By providing a thermally insulated channel, the hot air can be transported very far in the direction of the blade tip without great heat losses.
Moreover, an arrangement of the thermally insulated channel on the web, in particular the web that is arranged toward the rotor blade nose, is conducive to achieving short paths for the air stream from the channel to the inner wall of the rotor blade nose. Also as a result of this, very efficient and effective deicing is made possible. In particular, the first region of the rotor blade and the second region of the rotor blade are to be understood as meaning a first region of the cavity or interior space and a second region of the cavity or interior space of the rotor blade.
A closed air stream is preferably provided. The components of the rotor blade are consequently redesigned in such a way that a closed air stream is made possible. By providing a closed air stream, very effective deicing is possible, since no air is lost and in particular the air may possibly contain residual heat, which does not have to be re-heated to be re-admitted into the rotor blade as hot air. This ensures high energy efficiency.
The openings in the channel are preferably formed as nozzles, whereby an increase in the velocity of the hot air as it leaves the openings is achieved, and consequently a corresponding air stream directly onto the inner wall of the rotor blade nose is made possible.

- 4 -The thermally insulated channel preferably tapers in the direction of the blade tip. As a result, an increase in the velocity is achieved or a loss of velocity caused by hot air being discharged via the

5 openings in the channel is compensated. The tapering of the channel preferably takes place continuously, at least in certain portions, or alternatively in the form of stages, at least in certain portions.
The thermally insulated channel preferably has at its end toward the blade tip an opening, which points toward the blade tip and is formed in particular as a nozzle. As a result, the inner wall of the blade tip can be very efficiently subjected to hot air, and the blade tip consequently deiced.
The first region is preferably formed as a front box.
The front box then comprises the web, which is arranged toward the rotor blade nose, and also the parts of the rotor blade shell, which comprise the rotor blade nose and reach up to the web.
It is particularly preferred if an air-stream directing device, which directs the heated air stream along the rotor blade nose in the direction of the blade root, is provided in the first region. The air-stream directing device may comprise directing plates or directing angles. These are preferably arranged on the inner side or the inner wall of the rotor blade nose. The channel is preferably formed as a tube.
The channel or the tube is formed in a thermally insulating or thermally insulated manner in order to avoid great heat losses. Being formed in a thermally insulated manner or a thermally insulated channel or tube should be understood as meaning a channel or a tube on the wall of which there is a corresponding thermal insulation, which has a low thermal conductivity. The thermal conductivity is preferably below 1 W/(m*K), in particular below 0.8 W/(m*K), in particular below 0.4 W/(m*K). It is particularly preferred for the thermal conductivity to be below 0.11 W/(m*K), in particular below 0.1 W/(m*K). The thickness of the wall of the thermally insulated channel is preferably between 1 cm and 10 cm, in particular between 3 cm and 8 cm, in particular between 4 cm and 6 cm. At least in certain portions, the wall of the thermally insulated channel is preferably made of an insulating material and a stabilizing material, such as for example glass-fiber reinforced plastic. A sandwich structure is preferably provided for the wall, a stabilizing material respectively enclosing an insulating material. The following structure is consequently obtained from the inside to the outside:
stabilizing material insulating material stabilizing material. Further plies or layers may also be provided, for example as follows: stabilizing material / insulating material / stabilizing material /
insulating material/stabilizing material. Polyurethane, mineral wool, glass wool and/or PVC foam preferably come into consideration as insulating material.
The channel or the tube is preferably adhesively attached to the web. This is particularly efficient during production, since the tube or the channel can be mounted on the web outside the main mold of the rotor blade during production, and consequently the mold occupancy time is preferably not increased and the mold also does not have to be modified.
As an additional measure, it may preferably be envisaged to provide a device for sealing off a leak in the thermally insulated channel. This device may be designed in the manner of a lance, in particular in the form of a tube, and serve the purpose of introducing an adhesive or a resin into the region of a leakage location of the thermally insulated channel.
Particularly preferably, an injection head may be . t

- 6 -provided, by means of which injection of the adhesive or the resin into the leakage location is provided. The injection head may be designed in the form of a brush, the bristles of the brush touching the inner wall of the thermally insulated channel and bringing about a transport of the adhesive or the resin to the leakage.
It may in particular be envisaged to provide hollow bristles, through which the adhesive or the resin can then be conducted from the device formed as a lance or from the interior of this device through the bristles to the inner surface of the thermally insulated channel. As a result, corresponding material can be introduced quite specifically only in the region of a leakage, in order to eliminate the leakage.
Other methods of repair may also be used, such as for example the feeding of glass-fiber reinforced plastic mats into the region of the leakage, these preferably being plastic mats that have already been provided or impregnated with resin or adhesive, which are then stuck onto the leakage location. Adhesive tapes may also be correspondingly applied, or particularly preferably thermally insulating materials that are provided with adhesive at least on one side.
The object is also achieved by a deicing system for a wind turbine with a rotor blade that is described above, according to the invention or preferred. The deicing system provides a hot air stream or a heated air stream, in order to make deicing possible.
In the deicing system, an air-heating device is preferably provided in the region of a nacelle, a rotor hub or the blade root. The air-heating device preferably also comprises an air-stream generating device. Particularly preferably, the air-heating device is formed as a heating fan.

- 7 -The object is also achieved by a method for deicing a rotor blade of a wind turbine that has the following method steps:
- conducting a heated air stream from a blade root of the rotor blade in the direction of a blade tip, - the heated air stream being conducted in a thermally insulated channel, which is arranged on a web, the web delimiting a first region of the rotor blade, comprising a rotor blade nose, from a second region, comprising a rotor blade trailing edge, - the heated air stream being at least partially branched off from the channel on the way to the blade tip and conducted in the direction of the rotor blade nose, and - the branched-off air stream subsequently being conducted in a cavity, which is provided between the rotor blade nose and the web and also the channel, back to the blade root.
The term or the feature in the direction of the rotor blade nose comprises the meaning in the direction of the inner wall of the rotor blade nose. Part of the air stream is consequently directed directly onto the inner wall of the rotor blade nose.
The branched-off air stream is preferably returned to the blade root on the inner wall of the rotor blade nose. As a result, residual heat can also be put to further use, in order to deice the rotor blade correspondingly at the rotor blade nose.
The variant that the velocity of the air stream is increased during the branching off from the channel is

- 8 -particularly preferred. This involves exploiting a nozzle effect or the Bernoulli effect, in order to direct the air stream directly onto the inner wall of the rotor blade nose.
Part of the heated air stream is preferably directed onto the inner wall of the blade tip and subsequently returned to the blade root in the cavity, in particular at the rotor blade nose. As a result, the blade tip of the rotor blade can also be heated very efficiently.
It is particularly preferred for a closed air-stream circulation to be provided.
It is also preferred to direct the air stream onto the inner wall of the rotor blade nose and/or the inner wall of the rotor blade tip by means of an air-stream directing device. This involves preferably exploiting a Coanda effect. The directing device may for example be formed in such a curved manner that the hot air stream remains in close contact with the air-stream directing device and subsequently remains in close contact with the inner wall of the rotor blade nose and/or the inner wall of the rotor blade tip. A directing wall or a directing angle, which extends in the longitudinal extent of the rotor blade and confines a significant part of the hot air stream to an intended region of the inner wall of the rotor blade nose or the rotor blade tip, may also be provided as the air-stream directing device.
Preferably only a region of 40% to 100%, in particular 50% to 95%, of the length of the rotor blade, measured from the blade root to the blade tip, is subjected to the heated air stream directly from the channel.
Consequently, it is preferably only from 40%, measured from the blade root, preferably only from 50%, measured from the blade root, that the channel is provided with openings from which hot air then flows out and subjects =

- 9 -the inner wall of the rotor blade nose to hot air. A
preferred way of carrying out the method according to the invention envisages using additional measures of the operating control system to assist the deicing here. Turning the rotor out of the wind, for example by moving the nacelle on the tower, changing the position of the rotor, for example setting the blade horizontally with the nose downward or the blade axis perpendicularly downward, changing the blade angle (pitch) by 180 and/or additional vibrational excitation for shaking off ice that has begun to thaw are preferred here.
The method for deicing is preferably only carried out in the case of one rotor blade, which is arranged on the rotor in such a way that no other rotor blade is arranged under the rotor blade that is to be deiced. In the case of wind turbines with rotors that have three rotor blades, this is usually always the case when the rotor blade to be deiced is arranged in the lower half of the circle traced by the rotor. This avoids damage to another rotor blade being caused by ice falling off.
Furthermore, for deicing, a rotor blade trailing edge is preferably positioned in or adjusted into the direction of the incident wind. The rotor blade trailing edge of the rotor blade that is adjusted into the direction of the incident wind, i.e. on which the wind first acts, has the effect that no convection is produced at the rotor blade nose. The rotor blade nose is then on the downwind side and the rotor blade trailing edge is on the upwind side. The wind flow consequently breaks away before the nose, so that no further ice can form there, which makes the deicing of the rotor blade nose easier.
In the event of a defect of the thermally insulated channel, the channel is preferably repaired by means of an injection of a resin or an adhesive at the defective

- 10 -location or at a leakage location. This involves using for example a lance-like device, which may in particular be configured in the form of a tube and has an injection head. The injection head is brought into the region of a leakage location or damaged location, so that adhesive or resin can be specifically introduced there.
It is particularly preferred if a brush-like injection head is provided, particularly preferably in operative connection with the entire circumference of the inner surface of the thermally insulated channel. By means of the brush-like injection head, adhesive can then be brought to the leakage location very efficiently.
It may also be envisaged to provide on the injection head a brush that is only provided to one side, so that only a small region of the inner side of the thermally insulated channel can be provided with an adhesive or a resin at a time, so that the leakage location can be sealed off in a specific manner with little material consumption.
Alternatively, a thermally insulating material that is provided with an adhesive or layer of adhesive on one side may also be stuck onto the leakage location.
Moreover, a monitoring may also take place, for example by means of a camera robot, which is brought into the region of the leakage location in order to check the precise nature of the leakage location and which repair measure appears to be most appropriate.
Further features of the invention are evident from the description of embodiments according to the invention together with the claims and the accompanying drawings.
Embodiments according to the invention may implement single features or a combination of a number of features.

- 11 -The invention is described below on the basis of exemplary embodiments with reference to the drawings, without restricting the general concept of the invention, reference being expressly made to the drawings with respect to all details according to the invention that are not explained more specifically in the text. In the drawings Figure 1 shows a schematic sectional representation in a plan view of a rotor blade, Figure 2 shows a schematic detail 25 from Figure 1 in a plan view, Figure 3 shows a schematic cross section through a part of a rotor blade according to the invention, to be precise transversely in relation to the longitudinal extent and Figure 4 shows a detail of a further rotor blade according to the invention in a schematic representation.
In the drawings, elements and/or parts that are the same or similar are in each case provided with the same reference numerals, and so they are not described from the beginning each time.
Figure 1 schematically shows a rotor blade 10 according to the invention in a sectional representation and in a plan view. The rotor blade 10 has a blade root 11, which is usually attached to a rotor hub. On the side opposite from the blade root 11, a blade tip 12 is provided. The longitudinal extent of a rotor blade 10 may be for example up to 60 or more meters.
A rotor blade nose 15, that is to say a forward region of the rotor blade, i.e. the region that is exposed to , ! t t

- 12 -the flow of air during use of the rotor blade as intended, and a trailing edge 16 are represented.
Arranged in the rotor blade are for example two webs 13 and 14, the web 13 being the forward web or the web that is arranged toward the rotor blade nose 15.
A rotor blade 10 is usually formed as hollow with a cavity 31. According to the invention, the cavity 31 or the rotor blade 10 is divided into a first region 19 and a second region 20, the first region 19 being the region between the forward web 13 and the rotor blade nose 15. According to the invention, provided in this region is a channel or tube 18, which extends substantially from the blade root 11 to substantially the rotor blade tip 12. In this exemplary embodiment, the tube begins at a distance from the blade root 11 and ends at a distance from the blade tip 12. A
connection of the tube 18 to a heating fan 22 exists by way of a connector tube 21, which is preferably configured as flexible, in order to compensate for tolerances and decouple vibrations and noise transmission.
The tube 18 is tapered in stages, to be precise in the longitudinally axial direction of the rotor blade toward the blade tip 12. This may preferably take place by tubes of different diameters pushed into one another with suitable rubber seals, so that at the same time simple thermal expansion compensation or axial movement compensation is made possible. Provided at the blade root 11 is a bulkhead 23, which closes off the cavity 31 from the rotor hub. Provided through the bulkhead 23 is a lead-through, through which the connector tube 21 is led.
By means of the heating fan 22, hot air 24 is conducted through the tube 18. Ice 17 is indicated on the rotor blade nose. The hot air 24 is directed through the tube 18 and from the tube 18 through openings 26, which are

- 13 -not represented in Figure 1 but are represented in Figure 2, onto the inner wall of the rotor blade nose 32 and at the end of the tube 18 in the direction of the inner wall 33 of the blade tip 12. As a result, deicing can be performed efficiently.
Figure 2 schematically shows the region of a detail 25 from Figure 1. Here, the openings 26 and the corresponding hot air stream 24, which may be referred to as a partial hot air stream, are represented. The tube 18 is attached to the web 13. The attachment may take place for example by adhesive bonding, in particular over a surface area or by means of adhesive tabs, or in the case of the tubes that are pushed into one another for length adjustment by means of rubberized clips, which are for their part adhesively bonded. In Figure 2 it is also shown especially that a nozzle 27 is provided at the end of the tube 18 on the blade tip side, in order to make an increased velocity of the hot air stream 24 possible as it leaves the tube 18. Deicing in the region of the blade tip, where the cross section of the front box is very narrow, is thereby made possible in an efficient way.
Figure 3 schematically shows in a cross-sectional representation transversely in relation to the longitudinal axis of the rotor blade 10 a part of the rotor blade 10, that is the front part of the rotor blade 10, and in particular the front box of the rotor blade 10. The rotor blade nose 15, on which ice 17 is located, is represented. The channel 18 has been applied to the web 13 by means of an adhesive bond 28.
Also represented are the first region 19 of the cavity 31 and corresponding directing angles 29, which provide that the air stream forms substantially between the two directing angles 29, so that there substantially the heating of the rotor blade nose 15 takes place from the inner wall 32 of the rotor blade nose 15.

- 14 -Figure 4 shows a further embodiment of a rotor blade 10 according to the invention, in which the connecting tube 21', which ends in the heating fan 22, is also additionally provided for the return of the air stream 24'. Moreover, a closing-off element 30, through which the returned air stream 24' is conducted, is provided for the reliable return of the air stream, and in order that no air stream is lost. The closing-off element may also be configured very simply in the form of a flexible sheet, for example a truck tarpaulin. As a result, a closed air-stream circulation can be achieved particularly efficiently. A mesh or the like should preferably be provided in the region of the return of the air stream 24', in order to prevent dirt or clumps of resin from being sucked in. In Figure 4, the corresponding air mass flows are represented by ni1 and 1'42- For a closed air circulation it holds that Mi = It12.
By providing a corresponding deicing system, which has in a rotor blade a thermally insulated tube which, with decreasing cross section, is fastened on the front box of the rotor blade and to the forward web, a design that is particularly compatible in terms of production is possible, since the tube can be mounted on the web outside the main mold in production. The tube conducts heating air up to the blade tip. Provided in the region of the blade tip are a multiplicity of simply drilled openings, which generate corresponding hot air streams or hot air jets.
Within the scope of the invention, the term blade outer region includes in particular a region of the rotor blade 10 that lies over more than 50% of the radius.
The blade outer region may therefore make up 50% to 100% of the length of the rotor blade, measured from the rotor blade root. Part of the blade outer region is defined within the scope of the invention as the blade tip. The blade tip is defined as 85% to 100% of the length of the rotor blade. The rotor blade tip = ' =

- 15 -preferably comprises a region of 90% to 100% of the rotor blade with respect to the length of the rotor blade, measured from the rotor blade root.
The hot air streams point directly at the leading edge to be deiced and correspondingly transfer the amount of heat optimally to there. Corresponding directing angles direct the mass flow along the leading edge. The tube tapers further toward the blade tip and serves there as a nozzle. This generates an additional hot air stream, which can be transferred with corresponding thermal energy into the last meters of the blade tip, since there is no corresponding installation space left there for a tube.
The deicing system or hot air system is preferably closed, i.e. hot air flows in the blade root region through the insulated tube into the front box and is conducted to the leading edge via the hot air jets.
Then the air flows via the front box back into the blade root, where a heating fan is positioned.
It is moreover preferably envisaged to provide the front box as completely closed. In this case, two openings, in which corresponding flexible pipelines or connecting tubes 21, 20' are provided, serve for the connection to the heating fan. The heating system or the rotor blade and the method for deicing a rotor blade are very low-maintenance and preferably do not have any metal components apart from the rotor hub.
Metal components may of course be provided in the form of lightning arresters and/or be incorporated in the blade shell in order to conduct heat better to the ice.
Consequently, thermal energy is optimally transferred and the ice can preferably deice in the critical blade outer region.
According to the invention, reduced structural expenditure is provided in comparison with DE 10 2010 r

- 16 -030 472 Al, and moreover less frictional losses occur as a result of the more direct conduction of the flow.
In spite of a very simple structure, very efficient functionality and consequently deicing is possible. By providing corresponding arrangements of the openings that can be prescribed, it is possible to provide desired temperature profiles at the specific regions of the rotor blade nose, in particular in the blade outer region. It is possible in particular to make allowance for variations in the structure and thickness of the blade shell in the nose region that have been made on the basis of optimizing the structure from aspects of strength. The deicing system or the rotor blade may be adapted by displacing or adding or omitting openings.
The system or the rotor blade can be optimized such that mainly the critical outer region of the rotor blade, that is 50% to 95% of the length of the blade, i.e. from 50% to 95% of the length of the blade, measured from the blade root, can be deiced.
All of the features mentioned, including the features that can be taken from the drawings alone and also individual features that are disclosed in combination with other features, are regarded as essential to the invention on their own and in combination. Embodiments according to the invention may be implemented by single features or a combination of a number of features.
Within the scope of the invention, features that are characterized by "in particular" or "preferably" are to be understood as optional features.

) ' A

- 17 -List of designations rotor blade 11 blade root 12 blade tip 13 web 14 web rotor blade nose 16 rotor blade trailing edge 17 ice

18 tube

19 first region second region 21, 21' connector tube 22 heating fan 23 bulkhead 24, 24' air stream region of detail 26 opening 27 nozzle 28 adhesive bond 29 directing angle closing-off element 31 cavity 32 inner wall 33 inner wall

Claims

Rotor blade deicing claims

1. A rotor blade (10) of a wind turbine, the rotor blade (10) extending from a blade root (11) to a blade tip (12) and having a cavity (31), in which a web (13) is arranged in the longitudinal extent of the rotor blade (10), the web (13) separating a first region (19) of the rotor blade (10), comprising a rotor blade nose (15), from a second region (20) of the rotor blade (10), comprising a rotor blade trailing edge (16), characterized in that a thermally insulated channel (18) is arranged in the first region (19) of the rotor blade (10) on the web (13), in order to conduct hot air (24) in the direction of the blade tip (12) in an air stream (24, 24'), openings (26), which are formed in such a way as to direct the hot air (24) to the rotor blade nose (15), being provided in the channel (18), with a return of the hot air to the blade root (11) taking place in the first region (19) of the rotor blade (10).

2. The rotor blade (10) as claimed in claim 1, characterized in that a closed air stream (24, 24') is provided.

3. The rotor blade (10) as claimed in claim 1 or 2, characterized in that the openings (26) in the channel (18) are formed as nozzles.

4. The rotor blade (10) as claimed in one of claims 1 to 3, characterized in that the thermally insulated channel (18) tapers in the direction of the blade tip (12).

5. The rotor blade (10) as claimed in one of claims 1 to 4, characterized in that the thermally insulated channel (18) has at its end toward the blade tip (12) an opening (26), which points toward the blade tip (12) and is formed in particular as a nozzle (27).

6. The rotor blade (10) as claimed in one of claims 1 to 5, characterized in that the first region (19) is formed as a front box.

7. The rotor blade (10) as claimed in one of claims 1 to 6, characterized in that an air-stream directing device (29), which directs the air stream (24, 24') along the rotor blade nose (15) in the direction of the blade root (11), is provided in the first region (19).

8. A deicing system for a wind turbine with a rotor blade (10) as claimed in one of claims 1 to 7.

9. The deicing system as claimed in claim 8, characterized in that an air-heating device (22) is provided in the region of a nacelle, a rotor hub or the blade root (11).

10. A method for deicing a rotor blade (10) of a wind turbine with the following method steps:
- conducting a heated air stream (24) from a blade root (11) of the rotor blade (10) in the direction of a blade tip (12), - the heated air stream (24) being conducted in a thermally insulated channel (18), which is arranged on a web (13), the web (13) delimiting a first region (19) of the rotor blade (10), comprising a rotor blade nose (15), from a second region (20), comprising a rotor blade trailing edge (16), - the heated air stream (24) being at least partially branched off from the channel (18) on the way to the blade tip (12) and conducted in the direction of the rotor blade nose (15), and - the branched-off air stream (24) subsequently being conducted in a cavity (31), which is provided between the rotor blade nose (15) and the web (13) and also the channel (18), back to the blade root (11).

11. The method as claimed in claim 10, characterized in that the branched-off air stream (24) is returned to the blade root (11) on the inner wall (32) of the rotor blade nose (15).

12. The method as claimed in claim 10 or 11, characterized in that the velocity of the air stream (24) is increased during the branching off from the channel (18).

13. The method as claimed in one of claims 10 to 12, characterized in that part of the heated air stream (24) is directed onto the inner wall (33) of the blade tip (12) and subsequently returned to the blade root (11) in the cavity (31), in particular at the rotor blade nose (15).

14. The method as claimed in one of claims 10 to 13, characterized in that a closed air-stream circulation is provided.

15. The method as claimed in one of claims 10 to 14, characterized in that only a region of 40% to 100%, in particular 50% to 95%, of the length of the rotor blade, measured from the blade root (11) to the blade tip (12), is subjected to the heated air stream (24) directly from the channel (18).

16. The method as claimed in one of claims 10 to 15, characterized in that the method for deicing is only carried out in the case of one rotor blade (10), which is arranged on the rotor in such a way that no other rotor blade (10) is arranged under the rotor blade (10) that is to be deiced.

17. The method as claimed in one of claims 10 to 16, characterized in that, for deicing, a rotor blade trailing edge (16) is positioned in or adjusted into the direction facing the incident wind.