WO2003058063A1 - Rotor blade heating system - Google Patents

Abstract

The invention relates to a rotor blade heating system which can be used particularly for wind power stations, whereby the rotor blades (2) thereof are embodied with a cavity (1) and consist of an electrically non-conductive material. According to the invention, the cavity (1) of each rotor blade (2) has a rotor blade heating system in the form of an electrically conductive heating layer (3) which is adapted at least occasionally and/or at least periodically to the geometry of the cavity (1).

Description

 Rotor blade heating

description

The invention relates to a rotor blade heater according to the preamble of claim 1.

Rotor blades, such as those used in particular in wind turbines, are generally hollow. The rotor blades are usually made of an electrically non-conductive material, for example to avoid lightning strikes and to enable weight-reduced production. Particularly at temperatures around freezing point and a high degree of air humidity, weather phenomena can occur, which are critical for the rotor blades in several respects.

On the one hand, it is possible for the rotor blades to freeze, with even the slightest freezing leading to considerable imbalances, which can damage the wind turbine.

On the other hand, lightning strikes pose a particular danger to the rotor blades. Thunderstorms can develop even at temperatures around freezing, whereby there is always a risk of severe damage or failure of the entire system due to a crash. One measure already mentioned to counteract such failures of a wind power plant is the manufacture of the rotor blades from electrically non-conductive materials.

To avoid icing on the rotor blades, for example from DE 198 02 574 AI, DE 196 21 485 AI or DE 195 28 862 AI air blower heaters are known in which air is heated and the rotor blade is protected from icing or by this heated air is cleared of icing. The technical outlay for such air heating of the rotor blades is relatively high, with some designs even requiring the system to be stopped until the rotor blades have been de-iced. Due to the resulting breakdown, it is not possible to generate electrical energy for this time.

The invention is based on the object of providing a rotor blade heater which is simple in structure, has a high degree of efficiency and, if possible, can also be activated at least temporarily and / or at least in the critical areas of a rotor blade during operation of the wind turbine. The avoidance of the risk of lightning strikes should be taken into account.

This task is solved by the technical characteristics of the

Claim 1.

Further embodiments of the invention are the subject of the dependent claims.

A rotor blade heater according to the invention, the rotor blades of which have a cavity and are made of an electrically non-conductive material, has an electrically conductive heating layer which at least temporarily and / or at least in sections adapts to the geometry of the cavity in the cavity of each rotor blade. This rotor blade heating, as it can be used not only for wind turbines, but also for all types of propellers, is very simple, can be manufactured inexpensively and enables flexible use depending on the weather conditions, without the system operated with it Must be brought to a standstill.

First, the rotor blade heater serves the purpose of protecting the rotor blades equipped therewith against ice infestation or of freeing infected areas from ice without requiring complex mechanics. Secondly, the heat energy generated generates measurable infrared radiation, so that an additional safety aspect can be guaranteed. The heat energy emitted can be recorded by infrared measuring devices, such as those found in aircraft. This means that these wind turbines are visible to aircraft with appropriate security technology, even if the weather conditions would not normally make this possible. A rotor blade heater according to the invention consequently emits far infrared radiation (FIR).

However, it is also within the scope of the invention to provide only parts of the cavity of each rotor blade with a heating layer. Partly equipping the rotor blade with a heating layer enables energy savings on the one hand, and on the other hand only the critical areas of the rotor blade can be protected from ice attack.

The temporary use of the rotor blade heater according to the invention enables the removal of layers of ice only when it is really necessary. This measure also leads to energy savings, since the rotor blade heating only has to be operated when there is actually a risk of ice infestation or if there is already one. A sensible embodiment of a rotor blade heater according to the invention can be seen, for example, in the fact that the heating layer consists of a film, a fabric or a fleece which is loosely inserted into the cavity of the rotor blade or attached to the inner surface of the cavity or integrated into the inner surface. The materials for the heating layer are only mentioned here as examples:

- carbon fibers

- carbon-glass fibers

- carbon felts

- Carbon-glass fiber fleece or carbon fleece.

All designs can be designed as self-supporting, solidified or else as elastic, flexible, preferably band-shaped materials. Such band-shaped strips can be produced very economically, are easy to process and have a low volume and weight. The carbon or carbon fibers have an electrical conductivity with a resistance, so that this provides an effective heating element with high efficiency. For reinforcement, these carbon fibers can be supported by polyester threads or can also be integrated into a film. This allows fabric or fabric-like structures to be produced which, after their use in the cavity of the rotor blade, are provided with electrodes for the power supply and can thus be used without major assembly work. It is particularly advantageous to design the rotor blade heater as a thin-layer, flexible material, it being possible for the heating layer to be accommodated within an elastic or also in a rigid film. It is important that the materials can be easily adapted to the geometry of the inner surface of the cavity of the rotor blade.

The connection of different materials with each other is within the scope of the inventive concept. For example, a fabric made of mentioned materials can be provided in connection with a plastic fiber.

As already mentioned, the heating layer can consist of carbon fibers or carbon fiber composite materials or only have these materials, which in turn can be designed as a woven or non-woven fabric or as a graphite emulsion.

To reduce the risk of lightning strikes in the rotor blades, it makes sense to arrange as few metallic elements as possible in or on the rotor blades. It is therefore advisable to attach the electrodes to the heating layer in such a way that they are predominantly in the area of the hub of the wind turbine.

According to a development of the invention, the electrodes can also be used as a holder for the heating layer.

Depending on the heating power and the desired intensity of the rotor blade heating, one heating layer can be sufficient to enable an effective removal of ice or to prevent ice infestation. However, it is also conceivable to arrange a plurality of heating layers one above the other, which, for example, can also be switched on or off at different times.

The execution of the heating layer in perforated or slotted form has proven to be a further, very sensible embodiment. A perforated or slotted heating layer of this type can be applied to a carrier material and then made into an integral part of the rotor blade, for example by casting with a liquid plastic. The liquid plastic penetrates the heating layer in the sections of its perforation or slit and unites then with the carrier material so that the heating layer can be completely integrated into the material of the rotor blade.

To improve the efficiency of the heating layer of a rotor blade heater according to the invention, it is also possible to provide it with an insulating layer. The insulating layer, which should preferably be on the inside of the cavity, allows the heat generated by the heating layer to escape to the outer surface of the component equipped with it almost without loss and in the shortest possible time, so that a very rapid removal of ice is possible.

According to a further useful embodiment of the invention, the heating layer can be used not only in the area of the rotor blade, but also as a component of the rotor head and / or the rotor hub of a wind power plant or of a drive unit coupled to the wind power plant. The rotor head, the rotor hub and the drive unit are provided with an insulating layer towards the core and insulated in such a way that the heat emitted by the heating layer penetrates to the outside almost without loss and in the shortest possible time. This means that the heating layer can be used not only to clear ice in the area of the critical zones of the rotor blades, but also in the area of the rotor head, the rotor hub and possibly other units on the wind turbine. Known plastics or other materials can be used as insulation materials.

A heating layer that only temporarily adapts to the inner surface of the cavity of the rotor blade can also be realized by an embodiment in which the heating layer is loosely inserted into the cavity. A volume-expandable hose element that can be inserted into the cavity of the rotor blade enables a direct contact between the heating layer and the inner surface of the cavity of the rotor blade.

However, the variant of loosely inserting the heating layer into the interior of the cavity is only one possible embodiment in which the expanded hose element presses the heating layer against the inner wall of the cavity. Another solution can be seen in that the hose element is provided with the heating layer at least on a part of its outer surface or is enveloped by it as a whole. The hose element inserted into the cavity of the rotor blade is inflated, for example, by means of compressed air and thus presses against the inner surface of the cavity of the rotor blade. After the corresponding heating layer has heated the rotor blade heating and the rotor blade has been freed of ice, the volume of the tube element can be reduced again and can be removed from the cavity.

Since the hose element does not have to cover the entire inner surface of the cavity, a rotor blade heater that adapts to the geometry of the cavity is also hereby guaranteed. For example, a balloon or an inflatable tube can be used as the tube element.

In order to be able to direct the hose element in a targeted and targeted manner into the critical areas of the rotor blade, it is also proposed to make it movable along a guide present in the cavity of the rotor blade. According to the invention, at least one traction means is used to introduce the hose element into the cavity of the rotor blade or for the opposite movement of the hose element. However, two traction means are preferably used which, for example, enable the hose element to be wound up and unwound by means of a drive unit. An electric motor can advantageously be used as the drive unit Bring use, the volume increase of the hose element can be made possible by means of a compressor.

There is no need to mention that the entire rotor blade heater according to the invention can be operated by means of temperature sensors and thermometers and with the help of electronic controls and is therefore controllable or regulatable. Of course, there is also remote control in the sense of the invention, which is particularly useful in offshore wind turbines.

Some exemplary embodiments of a rotor blade heater according to the invention are explained in more detail below with reference to the accompanying drawings. Show it:

Figure 1: sections of a first embodiment of a

Rotor blade heating,

FIG. 2: a second embodiment of a rotor blade heater in a partially cut rotor blade,

3 shows the section profile HI - in from FIG. 2, FIG. 4 shows the section profile IV-IV from FIG. 2, FIG. 5 shows a schematically greatly simplified illustration of a

Rotor blade heating with a hose element and FIG. 6: a section of a heating layer for the rotor hub of a wind turbine.

FIG. 1 shows a section of a first variant of a rotor blade heater according to the invention. The end region of a rotor blade 2 is shown here, which overall consists of an electrically non-conductive material. The rotor blade 2 has a cavity 1, on the inner surface 4 of which one Heating layer 3 is attached. This heating layer 3 is supplied with an electrical voltage by means of two electrodes 5 and can thus be heated. To reduce the risk of lightning strikes in the rotor blades, it makes sense to arrange as few metallic elements as possible in or on the rotor blades. The electrodes 5 are therefore attached to the heating layer 3 in such a way that they are predominantly located in the area of the hub of the wind power plant. Adhesive tapes 6, which are provided with an adhesive layer, are used here to hold the heating layer 3 on the inner surface 4 of the cavity 1. As can be seen from the illustration, the heating layer 3 is only applied in the critical areas of the rotor blade 2. These are especially the leading edges and the tips. The direction of rotation of the rotor blade 2 is illustrated by the arrow A in the right part of the figure in FIG. The activated heating layer 3 heats the outer surface 7 of the rotor blade in the shortest possible time and thus an infestation with an ice layer can be prevented or existing ice can be defrosted. The use of the rotor blade heater shown is also possible during the operation of the wind turbine. A shutdown is not necessary.

FIG. 2 shows a further embodiment of a rotor blade heater according to the invention. The rotor blade 2 is also moved in the direction of arrow A in this variant. It has a cavity 1, in which a guide 10 is integrated. A hose element 9 that can be wound up or unwound is inserted between the inner surface 4 of the cavity 1 and the guide 10. This hose element 9 is coupled at its two ends to a traction means 11 and 13, respectively. The hose element 9 can be wound up or unwound by means of these traction means, wherein the guide 10 enables the movement of the hose element along the inner surface 4 of the cavity 1 of the rotor blade 2. As can be seen from the illustration in FIG. 2, the hose element 9 does not become effective over the entire inner surface of the cavity 1, but only the critical areas of the Rotor blade 2 is acted upon by the tubular element 9. A heating layer 3 is attached to the outer surface of the hose element 9. This is wound up or unwound with the hose element 9. The hose element 9 is in turn designed to be volume-expandable, so that it can be inflated, for example, by means of a compressed air compressor. After unrolling the tube element 9, it is initially loosely between the guide 10 and the inner surface 4 of the rotor blade. After the compressor has been activated and the tube element 9 has been expanded to its final volume, the heating layer 3 is in direct contact with the inner surface 4 of the cavity 1 of the rotor blade 2. The heating layer 3 is now activated, so that the heating of the outer surface 7 of the rotor blade 2 increases liberation from the ice layer that may be present there. The arrows D and E symbolically represent the possible directions of movement of the traction means 11 and 13, respectively.

In Figures 3 and 4 are the sectional views corresponding to the

Section profiles in - HI and IV - IV shown in Figure 2.

FIG. 3 shows a section through the tube element 9, which can be moved into or out of the cavity 1 of the rotor blade 2 above the guide 10. After the volume expansion of the tubular element 9 to its maximum size, this is due to the

Inner surface 4 of the cavity 1.

FIG. 4 shows the traction means 13, as can also be moved back and forth between the guide 10 and the inner surface 4 of the cavity 1 of the rotor blade 2.

5 shows, in a highly simplified manner, a possible variant of the operation of a rotor blade heater according to the invention. Here, the hose element 9 is in the manner described above along a guide 10 in the cavity 1 of the Rotor blade 2 movably guided. It can be wound up or unwound because there is a coupling with the drive shaft of a drive unit 12 via the traction means 11. If we are talking here of a simplified representation, it is of course meant that the interposition of gear elements between the traction means 11 and the drive unit 12 is also possible. For reasons of simplification, however, these are not shown in FIG. 5. The drive shaft of the drive unit 12 is rotatable in both directions of movement. The possible directions of rotation are illustrated by arrow B in FIG. 5. The surface of the tubular element is provided with the heating layer 3. Its volume is expandable until it comes to rest on the inner surface 4 of the cavity 1 of the rotor blade 2. The volume expansion is made possible by a compressor 14 which can be coupled to the hose element 9 via a valve coupling 15. The direction of movement C in FIG. 5 illustrates the coupling movement between the hose element 9 and the compressor 14 in the region of the valve coupling 15.

In order to provide the most effective rotor blade heating available, as shown in FIG. 6, an insulation layer 8 can be provided below a heating layer 3 connected to the inner surface 4 of the cavity 1. This insulation layer 8 enables the heat generated in the heating layer 3 to escape in the shortest possible time. The heat can thus escape in the direction of the outer surface 7 with almost no loss. Such an insulation layer combination is also possible for the area of the rotor head or the rotor hub or a drive unit attached to the wind turbine. Related list;

1 cavity

2 rotor blade

3 heating layer

4 inner surface

5 electrodes

6 tape

7 outer surface

8 insulation layer

9 hose element

10 leadership

11 traction means

12 drive unit

13 traction means

14 compressor

15 valve coupling

A, B, C, D, E direction of movement or rotation

Claims

Rotor blade heating patent claims 1. Rotor blade heating, in particular for wind turbines whose rotor blades (2) formed with a cavity (1) consist of an electrically non-conductive material, characterized in that in the cavity (1) of each rotor blade (2) the geometry of the cavity is different (1) at least temporarily and / or at least partially adapting rotor blade heating from an electrically conductive heating layer (3) is present. 2. Rotor blade heater according to claim 1, characterized in that the heating layer (3) consists of a film, a fabric or a fleece, which is loosely inserted into the cavity (1) of the rotor blade (2) or on the inner surface (4) of the cavity (1) attached or integrated into the inner surface (4). 3. Rotor blade heater according to claim 1 or 2, characterized in that the heating layer (3) is an integral part of an elastic or rigid film. 4. Rotor blade heater according to one of the preceding claims, characterized in that the heating layer (3) is integrated in a dielectric, heat and far infrared radiation (FIR) reflecting film carrier or an electrically conductive layer material. 5. Rotor blade heater according to one of the preceding claims, characterized in that the heating layer (3) has an electrically conductive heating resistor and electrodes (5) for supplying current. 6. rotor blade heater according to claim 5, characterized in that the heating layer (3) by the electrodes (5) is attached. 7. rotor blade heater according to claim 5 or 6, characterized in that the electrodes (5) have electrically conductive, metallic strips such as copper strips, silver strips or aluminum strips. 8. rotor blade heater according to one of claims 5 to 7, characterized in that the electrodes (5) are coated with a conductive adhesive. 9. Rotor blade heater according to one of the preceding claims, characterized in that at least the heating layer (3) has metal, electrically conductive carbon, plastic, carbon composite material, glass fibers or a glass fiber composite material, ceramic materials, semiconductor materials, resins or metal oxides. 10. Rotor blade heater according to one of the preceding claims, characterized in that the heating layer (3) is designed as a self-supporting solidified fabric, fleece or as a self-supporting film. 11. Rotor blade heater according to one of the preceding claims, characterized in that the materials of the heating layer (3) have a fiber or powder form or are designed as a graphite emulsion or granular structure. 12. Rotor blade heater according to claim 11, characterized in that the heating layer (3) is mixed with a binder. 13. Rotor blade heater according to one of the preceding claims, characterized in that the heating layer (3) consists of at least one band-shaped strip. 14. Rotor blade heater according to one of the preceding claims, characterized in that the heating layer (3) with an adhesive tape (6) is attached directly to the inner surface (4) of the cavity (1) of the rotor blade (2). 15. Rotor blade heater according to claim 14, characterized in that the adhesive tape (6) has an electrically conductive adhesive. 16. Rotor blade heater according to one of the preceding claims, characterized in that a plurality of heating layers (3) are arranged running parallel to one another. 17. Rotor blade heater according to one of the preceding claims, characterized in that the material of the heating layer (3) is perforated or slotted at least in sections. 18. Rotor blade heater according to one of the preceding claims, characterized in that the heating layer (3) to the inside of the cavity (1) of the rotor blade (2) has an insulating layer (8) and is insulated such that the heat given off by the heating layer (3 ) almost lossless, leaks out in the shortest possible time. 19. Rotor blade heating according to one of the preceding claims, characterized in that the heating layer (3) is also part of the rotor head and / or the rotor hub of a wind turbine or a drive unit coupled to the wind turbine, the rotor head, the rotor hub or the drive unit being the core has an insulation layer (8) and is insulated in such a way that the heat emitted by the heating layer (3) penetrates to the outside in the shortest possible time with almost no loss. 20. Rotor blade heater according to one of claims 18 or 19, characterized in that the insulating material of the insulating layer (8) is a plastic. 21. The rotor blade heater according to claim 1, characterized in that the rotor blade heater has a volume-expandable hose element (9) that can be inserted into the cavity (1) of the rotor blade (2), so that when the hose element (9) is expanded, there is direct contact between the heating layer (3). and the inner surface (4) of the cavity (1) of the rotor blade (2) is present. 22. Rotor blade heater according to claim 21, characterized in that the hose element (9) is a balloon or a hose. 23. The rotor blade heater according to claim 21 or 22, characterized in that the hose element (9) can be moved along a guide (10) present in the cavity (1) of the rotor blade (2) within the rotor blade (2). 24. Rotor blade heating according to one of claims 21 to 23, characterized in that the hose element (9) by at least one traction means (11) within the cavity (1) of the rotor blade (2) is movable. 25. Rotor blade heater according to claim 24, characterized in that the at least one traction means (11) can be moved by a drive unit (12). 26. Rotor blade heater according to claim 25, characterized in that a winding device consisting of two traction means (11, 13) receives the hose element (9) on both sides and the winding device is coupled to the drive unit (12) designed as an electric motor, the hose element (9) is expandable by means of a compressor (14). 27. Rotor blade heater according to one of the preceding claims, characterized in that the operation of the rotor blade heater can be controlled or regulated depending on the temperature.