DE202016000658U1 - Piston accumulator with oval cross-section for integration into a rotor blade - Google Patents

Abstract

Piston accumulator (40, 42) having a tube (44, 46) whose interior with a movable piston (48, 50) having a seal against the tube (44, 46), in a gas side gas and in a hydraulic fluid side is divided for a hydraulic fluid, characterized in that the cross section (24) of the tube (26) is oval.

Description

The invention generally relates to the field of wind turbines (also called wind turbines). More specifically, the invention relates to a rotor for a wind turbine (WEA), which also acts as a flywheel storage by the inertia of the rotor can be changed during operation of the WEA.

In particular, the invention relates to rotor blades for such functioning as flywheel storage rotor, are integrated in the hydropneumatic piston accumulator to change by means of which during operation of the WEA, the moment of inertia of the rotor blades and corresponding to the rotor. The invention also relates to a piston accumulator, which is particularly suitable for integration into a rotor blade.

background

The system of a hydropneumatic flywheel accumulator in the rotor of a WEA has been well described in various publications by the inventor of the present invention. C. Jauch, "A flywheel in a wind turbine rotor for inertia control" (Wind Energy, DOI: 10.1002 / we.1784, 2014) contains a general system description of a flywheel accumulator in the rotor of a wind turbine. S. Hippel and C. Jauch describe in "Hydraulic-Pneumatic Energy Storage in a Wind Turbine for Enhancing the Power System Inertia" (13th Wind Integration Workshop 2014, Energynautics GmbH, November 2014, DOI: 10.13140 / 2.1.3731.6160) an embodiment of a flywheel storage system with hydropneumatic piston accumulators. S. Hippel, H. Thiessen and C. Jauch described in "Controllable flywheel in a rotor of a wind turbine to support the grid frequency control" (WETI University of Applied Sciences Flensburg, 13.03.2015, DOI: 10.13140 / 2.1.3076.8166) the context in which a flywheel storage system could be used in the rotor of a WTG.

A rotor of a WEA, whose moment of inertia is variable, represents an integrated flywheel, which can absorb or release energy without speed change, d. H. combines a power generation unit and an energy storage. The kinetic energy of the wind turbine can be controlled by changing the mass moment of inertia of the rotor. Thus, the wind turbine does not have to operate at suboptimal operating points, as would be the case if energy storage or energy output were achieved with a change in rotor speed. Also, no recovery period is necessary. Also, in an acting as flywheel storage rotor of a WEA no additional frequency inverters are necessary, as would be the case with accumulators or external flywheels as energy storage. In addition, the self-discharge of the storage system is zero compared to accumulators and external flywheels. Finally, in addition to the significant utility of the grid, this system can help reduce mechanical loads on the WTG.

In the flywheel storage system known from the publications mentioned above, hydropneumatic piston accumulators are used, which are installed (integrated) in the rotor blades of the rotor of the WEA. Since the aerodynamically effective profile of the rotor blade may not be impaired, the space for the piston accumulator, which should ideally be mounted as close as possible to the blade tip, limited in the rotor blade. 1 illustrates the fact that in the aerodynamically effective part of the rotor blade, the chord 5 of the rotor blade profile 4 much bigger than the thickness 7 of the rotor blade profile 4 , 1 also shows that the space 2 further by bars 3 , which serve to stiffen the rotor blade, is additionally limited. For the integration of a piston accumulator is thus essentially only a predetermined, roughly "cuboid" space 2 to disposal. In leaf constructions without webs, the space has approximately the shape of the leaf profile.

Summary of the invention

It is therefore a possible object of the invention to propose possible improvements for the variable moment of inertia rotor of a WEA described above.

The object is achieved in each case with the features of the independent claims. Further features and details of the invention will become apparent from the respective dependent claims, the description and the drawings. Features and details that are described in connection with the rotor blade according to the invention, of course, also apply in connection with a plurality of such rotor blades having rotor for a WEA (and a WEA with such a rotor) and in each case vice versa, so always with respect to the disclosure of the individual aspects mutual reference is or can be made.

A rotor with the rotor blades according to the invention has a mass moment of inertia which can be varied during operation and can thus be used as flywheel storage. The rotor flywheel can be charged at uncritical times, ie store energy and provide additional energy immediately when needed. For example, in the event of a frequency drop in the supply network to which the wind turbine is connected, the provide required power increase from the energy stored in the rotor of the WEA, without the speed of the rotor of the WEA must be lowered.

At first it was considered, similar to in the 3 shown to combine a plurality of circular piston accumulator but with different large cross-section so that the available cross-sectional area of the space in the rotor blade can be better utilized than the known design with a single circular piston accumulator, as in 2 shown. However, such an arrangement has significantly higher stationary masses, since the total area of the installed cylinder walls is much larger than with only one piston accumulator. In a hydropneumatic flywheel in the rotor of a WT, the fixed masses, ie everything but the hydraulic fluid should be as small as possible, since the stationary masses contribute to the moment of inertia of the rotor, but not to a change in the mass moment of inertia. As already mentioned, the advantage of the flywheel in the rotor of a WT lies in the variability of the mass moment of inertia and not in the largest possible moment of inertia.

A core idea of the present invention now consists in recognizing that the hydropneumatic piston accumulator to be integrated into the rotor blade does not have to be designed with a round cross section as before, but with an oval cross section. Thus, an improvement of the known piston accumulator is achieved by this can make better use of the space available in the rotor blade space and as a result a change in the moment of inertia of the rotor over a larger range is possible.

Accordingly, a first aspect of the present invention initially relates to a piston accumulator having an oval cross section, e.g. B. whose cross section has the shape of an ellipse, preferably a superellipse.

A piston accumulator is first known from the hydraulic pressure device, which consists essentially of a cylindrical tube, wherein a first side (gas side) of the tube with a gas, for. As nitrogen, and a second side (hydraulic fluid side) with a hydraulic fluid, eg. As hydraulic oil is filled and a movable piston is provided with a seal against the inner wall of the pipe for separating the hydraulic fluid and the gas. The hydraulic fluid can be pressed as pressure medium against the gas in the memory.

A second aspect of the invention relates to a rotor blade for the rotor of a WEA. The rotor blade has in the usual way a rotor blade root and a rotor blade tip. According to the invention, two piston accumulators of the first aspect of the invention are integrated into the rotor blade such that an inner piston accumulator is arranged closer to the rotor blade root and an outer accumulator accumulator is closer to the rotor blade tip and if required hydraulic fluid is displaced from one piston accumulator into the other piston accumulators can and vice versa.

The gas side of the inner piston accumulator is preferably directed to the rotor blade root and the gas side of the outer piston accumulator is directed to the rotor blade tip. Thus, the hydraulic fluid sides of the inner and outer piston accumulator are mutually aligned via a hydraulic line communicatively connected.

Since the profile of a rotor blade (rotor blade profile) is usually more long than wide, by means of the oval cross-section proposed here in the piston accumulator, the interior of the rotor blade can be filled much better than with conventional piston accumulators, which have a circular cross-section. Since the pressures which would have to be maintained in the hydropneumatic piston accumulators of the rotor flywheel of a WEA are comparatively low at approximately 20 bar, the sealing of the oval piston poses no problem.

Due to the lightweight design of rotor blades these are exposed in operation strong bends. If now built into the rotor blades piston accumulator, then these should not be bent, as this may not ensure the tightness. Such deflections can be avoided by the rotor blades at the points where the piston accumulators are arranged, in addition z. B. stiffened with carbon fibers.

Another advantage of the oval piston accumulator according to the invention in this context is that for a given fluid volume of the piston accumulator with oval cross section significantly shorter than a piston accumulator with a circular cross section. Accordingly, the rotor blade must be stiffened to a shorter length, which has an advantageous effect on both the masses and the cost of the rotor blade. Overall, the rotor blade must be significantly stiffened only at a maximum of two points, since the entire displaceable mass combines only in the inner or in the outer piston accumulator. Rotor blades of wind turbines are already usually sufficiently rigid at the location where the inner piston accumulator is arranged. Between the inner and the outer piston storage is only a hydraulic line as a hydraulic connection (tubing), whose contribution to the total weight of System is low. Thus, over a majority of the length of the rotor blade no structural changes are necessary.

A third aspect of the invention relates to a rotor for a wind turbine with a rotor hub to which at least one rotor blade according to the second aspect of the invention is attached. By means of the piston accumulator integrated into the rotor blades, the mass moment of inertia of the rotor can be realized by a displacement of masses within the rotor blades of the rotor. By changing the distance to the center of rotation, d. H. the rotor hub, significant amounts of kinetic energy can be stored or released.

A fourth aspect of the invention relates to a wind turbine with a rotor according to the third aspect of the invention.

The WEA may include a controller configured to control the moment of inertia of the rotor. The control device is preferably set up to control the piston accumulators in the rotor blades in such a way that the volume flow of the hydraulic fluid through the hydraulic line is uniform in all rotor blades.

Brief description of the figures

Further advantages, features and details of the invention will become apparent from the following description in which embodiments of the invention are described in detail with reference to the figures. The features mentioned in the claims and in the description may each be essential to the invention individually or in any combination. Likewise, the features mentioned above and the features listed further here can be used individually or in any combination. Functionally similar or identical components or components are partially provided with the same reference numerals. The terms "left", "right", "top", "bottom" used in the description of the embodiments refer to the figures in an orientation with normally legible figure designation, or normal readable reference numerals. The embodiments shown and described are not to be understood as exhaustive enumeration, but rather have exemplary character for the description of the invention.

1 shows a portion of a rotor blade of a WEA to illustrate the space between the webs, which can be used for the integration of a hydropneumatic piston accumulator in the rotor blade.

2 shows a perspective view of a rotor blade section in which a hydropneumatic piston accumulator with circular cross-section of the prior art is housed in the space between stiffening webs.

3 shows a perspective view of a rotor blade section, in which the optimal use of space between the webs a hydropneumatic piston accumulator is housed consisting of several circular piston accumulators.

4 shows a perspective view of a rotor blade section, in which an embodiment of a hydropneumatic piston accumulator according to the invention is accommodated with optimal space utilization between stiffening webs.

5 shows a schematic diagram of a WEA rotor to which a plurality of rotor blades are used, in each of which a hydropneumatic piston accumulator according to the invention is integrated, wherein the integrated into the rotor flywheel accumulator is shown in the discharged state.

6 shows the principle representation of the WEA rotor of 5 , wherein now the integrated into the rotor flywheel storage is shown in the charged state.

Preferred embodiments

The invention will be described in detail below with reference to the figures. The detailed description is for the convenience of those skilled in the art and is not intended to be limiting. In the following description, numerous specific details are set forth. Of course, embodiments of the invention as defined in the claims may also be used without these specific details. Known structures and methods are not unnecessarily shown or explained in detail here in order not to overburden the present description and to make it difficult to understand.

1 shows a section 1 a rotor blade of a wind turbine to illustrate the installation space 2 between stiffening webs 3 of the rotor blade. The installation space 2 should be used for the integration of a hydropneumatic piston accumulator in the rotor blade. 1 further shows the cross section of the rotor blade, which also serves as a rotor blade profile 4 is called and among other things by the tendon 5 that the rotor blade leading edge 11 with the rotor blade trailing edge 13 connects, and the rotor blade thickness 7 characterized. The installation space 2 This is essentially due to the course of the rotor blade suction side 15 , of the Rotor blade pressure side 17 and the location of the walkways 3 certainly.

2 now shows a perspective view of the rotor blade section 1 in which a hydropneumatic piston accumulator 9a with a circular cross-section 10a in the installation space 2 between the stiffening webs 3 is housed. In 2 is good to see that the circular cross-section 10a the installation space 2 not optimal use. D. h., A relatively large area of the installation space 2 remains unused. The size of the cross-section of the piston accumulator 9a determined next to the length of the piston accumulator its volume, which is available for receiving hydraulic fluid. In length, the piston accumulator can hardly be increased, so the moment of inertia of the rotor blade is adjustable only over a small range.

3 shows a perspective view of the rotor blade section 1 , in which for an optimal use of the installation space 2 between the stiffening webs 3 several piston accumulator 9b with a smaller, but also circular cross-section 10b are housed. This is the space 2 better used. As already discussed, this arrangement has much higher stationary masses, since the total area of the installed cylinder walls is much larger than with only one piston accumulator. The stationary masses of the rotor blade should be as small as possible, ie components other than the hydraulic fluid should be as light as possible, since the stationary masses can not contribute to changing the mass moment of inertia.

4 shows a perspective view of the rotor blade section 1 in which an embodiment of a hydropneumatic piston accumulator according to the invention 22 with an oval cross-section 24 is housed, the space 2 between the stiffening webs 3 better uses.

5 shows a schematic diagram of a WEA rotor 30 in which several rotor blades 32 on a rotor hub 34 are used. Every rotor blade 32 has a rotor blade tip 36 standing on one of a rotor blade root 38 opposite end of the rotor blade 32 lies. Into the interior of the rotor blade 32 are two piston accumulator according to the invention 40 . 42 integrated. Compared to each other sits an inner piston accumulator 40 closer to the rotor blade root 38 and an outer piston accumulator 42 closer to the rotor blade tip 36 ,

Each piston accumulator 40 . 42 consists essentially of an oval tube 44 . 46 , whose respective interior by means of a movable piston 48 . 50 , who is also one in the pipe 44 . 46 fitted oval cross-section and a sealant, for. As a seal against his pipe 44 . 46 is divided into a gas side for a gas and a hydraulic fluid side for a hydraulic fluid. As in 4 shown is the cross section of the tubes of the piston accumulator 40 . 42 oval.

The gas side of the inner piston accumulator 40 is to the rotor blade root 38 directed and the gas side of the second piston accumulator 42 is to the rotor blade tip 36 directed. The hydraulic fluid sides of the inner piston accumulator 40 and the outer piston accumulator 42 are via a hydraulic line 52 communicatively connected with each other.

With the help of the gas in the gas sides of the two piston accumulator 40 . 42 can the hydraulic fluid via a corresponding control of the gas pressure by means of corresponding valves (not shown) between the two piston accumulators 40 . 42 over the hydraulic line 52 be shifted back and forth. In the 5 the situation is shown in which all the hydraulic fluid in the inner piston accumulator 40 located. This is the in the rotor 30 integrated flywheel accumulator in discharged condition.

In the 6 are from the rotor 30 of the 5 only the inner piston accumulator 40 and the outer piston accumulators 42 with the respective hydraulic line 52 shown. The contours of the rotor blades are not shown for simplicity. 6 shows the situation in which all the hydraulic fluid in the outer piston accumulator 42 located. This is the in the rotor 30 * integrated flywheel storage in fully charged state.

In the operation of a WEA, with a in the 5 and 6 represented rotor 30 . 30 * is equipped, in operation, ie, with a rotating rotor, a pressure medium, such as a hydraulic fluid between the individual each in a rotor blade 32 integrated piston accumulators 40 . 42 be moved in different distances to the rotor hub. This allows the moment of inertia of the rotor 30 to change.

To illustrate the operation of the variable moment of inertia rotor, a numerical example is given. If ever rotor blade 32 about 500 kg of hydraulic fluid about 20 m from the axis of rotation DR, ie the rotor hub 38 , Towards rotor blade tips 36 sufficient kinetic energy can be stored to support the power frequency control with instantaneous reserve in the event of a frequency dip in the grid. Suppose the internal piston accumulator integrated inside the rotor blade 40 is located about 2 m away from the axis of rotation DR. Then with a shift of the center of mass to a radius of 22 m the Moment of inertia of the rotor 30 be increased by about 720,000 kgm ² with three rotor blades. This change happens by means of the closed system from the two piston accumulators 40 . 42 per rotor blade 32 passing through the hydraulic line 52 and controllable valves (not shown) are interconnected. The outer piston accumulators 42 can by means of the pressurized gas in the gas side, the hydraulic fluid in the inner piston accumulator 40 push back as soon as the stored energy should be needed. The regulation of the mass moment of inertia of the rotor 30 is thus due to a shift of masses within the rotor blades 32 of the rotor 30 realized. By changing the distance to the rotation center DR, ie the rotor hub 38 , significant amounts of kinetic energy can be stored or released in the rotor.

A WEA (not shown) can be equipped with a rotor according to the invention 30 as in the 5 and 6 shown to be equipped. The WEA 60 then has a control device 62 on, the need-based control of the moment of inertia of the rotor 30 is set, ie the displacement of the hydraulic fluid between the inner and the outer piston accumulators 40 . 42 in the individual rotor blades 32 to control. This is the control device 62 equipped, the valves (not shown) for influencing the gas pressure in the gas sides of the piston accumulator 40 . 42 to control that in all rotor blades 32 the volume flow of the hydraulic fluid through the hydraulic line 52 is uniform.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited non-patent literature

• C. Jauch, "A flywheel in a wind turbine rotor for inertia control" (Wind Energy, DOI: 10.1002 / we.1784, 2014) [0003]
• S. Hippel and C. Jauch describe in "Hydraulic-Pneumatic Energy Storage in a Wind Turbine for Enhancing the Power System Inertia" (13th Wind Integration Workshop 2014, Energynautics GmbH, November 2014, DOI: 10.13140 / 2.1.3731.6160) [0003]
• S. Hippel, H. Thiessen and C. Jauch described in "Controllable flywheel in a rotor of a wind turbine to support the grid frequency control" (WETI University of Applied Sciences Flensburg, 13.03.2015, DOI: 10.13140 / 2.1.3076.8166) [0003]

Claims (8)

Piston accumulator ( 40 . 42 ) with a pipe ( 44 . 46 ), whose interior is equipped with a movable piston ( 48 . 50 ), which seals against the pipe ( 44 . 46 ), is divided into a gas side for a gas and a hydraulic fluid side for a hydraulic fluid, characterized in that the cross section ( 24 ) of the pipe ( 26 ) is oval. Piston accumulator ( 40 . 42 ) according to protection claim 1, characterized in that the cross section ( 24 ) has the shape of an ellipse or superellipse. Rotor blade ( 32 ), comprising a rotor blade root ( 38 ) and a rotor blade tip ( 36 ), for a rotor ( 30 ) of a wind turbine, characterized in that in the rotor blade ( 32 ) at least one piston accumulator ( 40 . 42 ) is integrated according to protection claim 1 or 2. Rotor blade ( 32 ) according to protection claim 3, characterized in that in the rotor blade ( 32 ) two piston accumulators ( 40 . 42 ) are integrated according to protection claim 1 or 2 such that in comparison to each other an inner piston accumulator ( 40 ) closer to the rotor blade root ( 38 ) and an outer piston accumulator ( 42 ) closer to the rotor blade tip ( 36 ) is arranged and hydraulic fluid from the inner piston accumulator ( 40 ) in the outer piston accumulators ( 42 ) and vice versa. Rotor blade ( 32 ) according to claim 4, characterized in that the gas side of the inner piston accumulator ( 40 ) to the rotor blade root ( 38 ) and the gas side of the outer piston accumulator ( 42 ) to the rotor blade tip ( 36 ) and the hydraulic fluid sides of the inner and outer piston accumulators ( 42 ) via a hydraulic line ( 52 ) are communicatively connected with each other. Rotor ( 30 ) for a wind energy plant with a rotor hub ( 38 ), with which at least one rotor blade ( 32 ) is connected according to one of the claims 4 or 5 protection. Wind turbine with a rotor ( 30 ) according to protection claim 6. Wind turbine according to claim 7, further comprising a control device for controlling the moment of inertia of the rotor ( 30 ), wherein the control device is arranged, valves for influencing the gas pressure in the gas sides of the piston accumulator ( 40 . 42 ) so that in all rotor blades ( 32 ) the volume flow of the hydraulic fluid through the hydraulic line ( 52 ) is uniform.

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