Patent Application
20220056885
The following is related to a foundation for a wind turbine, especially for an onshore wind turbine. Furthermore, the following is related to a wind turbine, especially an onshore wind turbine.
Foundations for wind turbines, especially for onshore wind turbines, are used to provide a base for a tower of the wind turbine. Usually, such foundations are made of concrete, especially reinforced concrete, or the like. These foundations comprise different zones that contribute differently to the support of the tower. Basically, such foundations comprise an outer zone and a center zone, wherein all or at least most of the load of the tower is conducted into the outer zone. Therefore, the center zone is also denoted as “non-loaded area”.
Generally, center zones just exist due to simplify the design of the foundation and installation but have no particular function due to the lack of loads present. Therefore, the center zones essentially contribute to the environmental footprint as well as the costs of the wind turbine project.
Moreover, wind turbines have the disadvantage that in windy situations a surplus of electricity may be produced wherein in windless situations no electricity can be generated. This means a special challenge for the electric grid to transport and store electricity produced by wind turbines.
To relieve the grid and to provide a more constant electricity supply, there are approaches for storing electricity locally at the wind turbine. Documents U.S. Pat. No. 7,608,937 B1 and U.S. Pat. No. 7,265,456 B2 relate to power generation systems with wind turbine generators and batteries for storing excess electricity and providing that electricity in windless or low wind speed situations.
Batteries have the disadvantage of relatively high costs and low lifetime due to constant capacity loss. Used batteries are hazardous waste and, as a consequence, recycling of batteries is very expensive as well. Moreover, such batteries often require cooling means to prevent overheat and have to be protected from environmental influences, especially from water.
Therefore, it is an aspect of the present invention to provide a device that does not have these drawbacks or at least partially does not have these drawbacks. In particular, it is the aspect of the present invention to provide a foundation for a wind turbine and a wind turbine that provides an improved storage of energy produced by the wind turbine.
According to a first aspect of the present invention, the problem is solved by a foundation for a wind turbine, comprising base means with a center zone and an outer zone, wherein the outer zone is configured for carrying most of the weight of the wind turbine. According to the embodiment of the present invention, in the center zone, the base means comprises a chamber, wherein the foundation further comprises energy storage means. The energy storage means comprise a flywheel pivotally arranged within the chamber for storing rotational energy and transmission means for transforming energy of a wind turbine into rotational energy of the flywheel and for transforming rotational energy of the flywheel into electrical energy.
The foundation is configured as a base for a wind turbine, especially a wind turbine with a rotor comprising rotor blades for converting wind energy into rotational energy of the rotor, a generator for converting rotational energy of the rotor into electrical energy and a tower for carrying the rotor and the generator. Therefore, the foundation is configured as a base for the tower. The foundation comprises fixation means, such as screw holes or the like, for fixing the tower to the foundation.
The outer zone of the base means constitutes the part of the foundation that is configured for carrying all or at least most of the weight of the wind turbine. The base means or at least the outer zone of the base means is made or at least essentially made of steel-concrete or the like. According to the embodiment of the present invention, the base means and/or the foundation has a cylindrical or cubical outer geometrical shape. Basically, the outer shape and size of the foundation can be identical or at least similar to foundations known from the prior art.
The chamber is provided in the center zone of the base means. The center zone is within a non-loaded area of the foundation. Therefore, due to the chamber there are no structural disadvantages compared with foundations that do not have such chamber. The chamber is sealed to the environment to prevent moisture from entering the chamber. Inner walls of the chamber have a smooth surface, e. g. to avoid air turbulences.
The flywheel of the energy storage means is located within the chamber and pivoted against the walls, e. g. sidewalls, floor or the like, of the chamber, especially by bearings. Thus, the flywheel can rotate freely inside the chamber. The bearings are configured for minimized friction to minimize a loss of rotational energy of the rotating flywheel. An axis of rotation of the flywheel is vertical or horizontal. Alternatively, the axis of rotation of the flywheel can be transversal. The flywheel comprises a material with relatively high density, such as lead, iron, steel or the like. It is preferred that the flywheel is configured as a massive body. An outer surface of the flywheel is relatively smooth to avoid or at least reduce turbulences. Moreover, the flywheel is of a rotationally symmetrical shape. The chamber and the flywheel are configured such that a constant or at least essentially constant gap is provided between the outer surface of the flywheel and the inner walls of the chamber.
The transmission means of the energy storage means are configured for transforming energy, electrical energy, of the wind turbine into rotational energy of the flywheel and for transforming rotational energy of the flywheel into electrical energy.
The foundation according to the embodiment of the present invention has the advantage that with cost-efficient means and in a safe way, energy of a wind turbine can be temporarily stored and provided on demand. With the present invention, e. g. the scenarios smoothing power output, improving black start, enhancing performance and providing backup power can be managed.
Smoothing power output is advantageous since wind tends to blow at different wind speeds and, therefore, the amount of electrical energy that can be generated by the generator of the wind turbine is not constant. By means of the present invention, a smoothened power output of the wind turbine can be provided. Smoothing e. g. relates to meeting a certain power setpoint. This means absorbing the power above the setpoint when generation is above the setpoint, or injecting power from the storage when generation is below the setpoint. This applies to all wind speeds. This can be achieved by storing excess energy of the wind turbine in the flywheel or transforming the rotational energy of the flywheel into electrical energy on demand.
Furthermore, by means of the present invention, black start of the wind turbine can be improved. For starting the rotor of the wind turbine, inertia, friction and stiction have to be overcome. Moreover, a main application for black start is to provide the current that magnetises the generator coils in order to create the magnetic field necessary for induction. Present wind turbines need to draw electrical energy from the grid for startup. With the present invention, start-up of the rotor is even possible in situations when there is not enough electrical energy available in the grid, e. g. right after a grid outage.
Beyond that, by means of the present invention, backup power for the wind turbine can be provided. Thus, batteries are not needed anymore.
It is preferred that the transmission means comprise a flywheel electric motor for transforming electrical energy into rotational energy of the flywheel. According to the embodiment of the present invention, the transmission means can comprise more than one flywheel electric motor for driving the flywheel, e.g. for redundancy and/or boost operation, when quick transformation of the electrical energy into rotational energy is required. It is further preferred that at least one flywheel electric motor of the plurality of flywheel electric motors is mechanically separable from the flywheel and/or the plurality of electric motor by means of a clutch. By means of the flywheel electric motor, the flywheel can be rotated. Therefore, it is preferred that a motor rotor of the flywheel electric motor is mechanically coupled or at least can be mechanically coupled to the flywheel. In an alternative embodiment of the present invention, the flywheel electric motor can be a part of the flywheel. A flywheel electric motor has the advantage that, by ordinary means and in a cost-effective way, transformation of electrical energy into rotational energy of the flywheel can be provided.
Advantageously, the transmission means comprise electric control means for providing electrical energy produced by a generator of the wind turbine and/or electrical energy from the grid to the flywheel electric motor. Further preferred, the electric control means is configured for providing electrical energy from a flywheel generator to the grid. Receiving the electrical energy for driving the flywheel electric motor from the generator of the wind turbine has the advantage that excess electrical energy generated by the generator can be stored as rotational energy. Receiving the electrical energy for driving the flywheel electric motor from the grid has the advantage that, by ordinary means and in a cost-effective way, excess electrical energy of the grid can be stored as rotational energy. Even in cases that a particular wind turbine is not operating, the foundation of that wind turbine still can be used for storing energy.
According to an exemplary embodiment of the present invention, the transmission means comprise a flywheel generator for transforming rotational energy of the flywheel into electrical energy. The flywheel generator and the flywheel electric motor are the same device. This has the advantage that investment costs and operating space can be reduced. Alternatively, flywheel generator and flywheel electric motor can be configured as different devices. This has the advantage that, by ordinary means and in a cost-effective way, technical characteristics of the flywheel generator and the flywheel electric motor can be optimized with respect to the prospective operating parameters. Thus, flywheel generator and flywheel electric motor can have different sizes.
The energy storage means comprise a clutch for mechanically separating the flywheel from transmission means of the energy storage means. It is preferred that the clutch is located between the flywheel and the flywheel electric motor and/or flywheel generator to mechanically separate the flywheel electric motor and/or flywheel generator from the flywheel. It is further preferred that the clutch is configured as magnetic clutch. A clutch has the advantage that, by ordinary means and in a cost-effective way, the flywheel can rotate freely without being mechanically coupled to the flywheel electric motor and/or the flywheel generator. Thus, mechanical losses of the rotation of the flywheel are reduced and rotational energy can be stored within the flywheel for a longer time.
It is preferred that the energy storage means comprise magnetic bearings for pivoting the flywheel with respect to the chamber. The magnetic bearings comprise permanent magnets and/or magnetic coils. The energy storage means are configured for providing the magnetic coils with electrical energy generated from the generator of the wind turbine and/or the flywheel generator and/or provided from the grid. It is further preferred that the energy storage means comprise a safety bearing to substitute the magnetic bearing in case of a technical defect, outages or the like. The magnetic bearings are supported at the walls and/or the bottom of the chamber. The usage of magnetic bearings has the advantage that, by ordinary means and in a cost-effective way, friction within the energy storage means can be reduced and rotational energy can be stored within the flywheel for a longer time.
Advantageously, the chamber is configured as a vacuum chamber. This means that the chamber is configured for being sealingly closed to an environment of the foundation. It is further preferred that the foundation comprises a vacuum pump for evacuating the chamber. The foundation comprises a pressure sensor for measuring the pressure inside the vacuum chamber. The pressure sensor is connected to a pump control unit of the vacuum pump for automatically operating the pump in dependence of the measured pressure. A vacuum chamber has the advantage that, by ordinary means and in a cost-effective way, air resistance and turbulences within the chamber can be reduced and rotational energy can be stored within the flywheel for a longer time.
In an exemplary embodiment of the present invention, the energy storage means comprise a plurality of flywheels. The flywheels are pivotally arranged within the chamber. The flywheels are distributed equally or symmetrically over the chamber. The flywheels are mechanically separated from each other and can be operated independently from each other. By these means, sizes of the flywheels can be significantly smaller than the size of only one flywheel. Therefore, sizes of the flywheel electric motors and the flywheel generators can be smaller as well. A plurality of flywheels has the advantage that, by ordinary means and in a cost-effective way, storage of energy can be improved.
It is preferred that each flywheel has a cylindrical or at least substantially cylindrical shape. A substantially cylindrical shape is a cylindrical shape with one or more different areas, e. g. for coupling with the bearings. This has the advantage that, by ordinary means and in a cost-effective way, a flywheel is provided that has especially good rotating properties and can be easily fit into the chamber of the foundation.
According to a second aspect of the embodiment of the present invention, the problem is solved by a wind turbine, comprising a rotor with rotor blades for converting wind energy into rotational energy of the rotor, a generator for converting rotational energy of the rotor into electrical energy, a tower for carrying the rotor and the generator and a foundation for carrying the tower. According to the present invention, the foundation is a foundation according to the first aspect of the present invention.
The rotor and the generator are arranged within a rotor chamber, which is pivotally arranged at a top end of the tower. The rotor is pivotally arranged within the rotor chamber. The rotor blades are attached to the rotor and, are pivotally arranged at the rotor for adjusting a rotor blade setting angle of the rotor blades with respect to the rotor.
The tower is configured as a hollow construction with a substantially cylindrical or conical shape. A lower part of the tower has a larger diameter than a higher part of the tower. The tower can consist of more tower sections, which are connectable to each other by fasteners, such as screws, nuts and bolts, welds or the like. The tower is constructed for carrying the rotor and the generator, especially for carrying the rotor chamber.
The wind turbine according to the embodiment of the present invention has the same advantages as the foundation according to the first aspect of the present invention. Therefore, the wind turbine has the advantage that with cost-efficient means and in a safe way, electrical energy generated by the generator can be temporarily stored and provided on demand by the energy storage means. With the present invention, e. g. the scenarios smoothing power output, improving black start, enhancing performance and providing backup power can be managed.
According to a third aspect of the present invention, the problem is solved by a method for storing and using energy generated by a wind turbine, especially a wind turbine according to the second aspect of the present invention. The Method comprising the following steps:
In an initial step, the clutch, especially a magnetic clutch, is closed. By closing the clutch, the flywheel of the foundation of the wind turbine is mechanically coupled with the motor rotor of the flywheel electric motor of the foundation. With a closed clutch, rotational speed of the flywheel electric motor and the flywheel are within a predetermined flexibility ratio.
Wind blows with a certain wind speed or various wind speeds against the rotor blades of the rotor of the wind turbine. This causes the rotor to rotate. Since the rotor and the generator are mechanically coupled with each other, this causes the generator to generate electrical energy. At least part of this electrical energy, especially when the capacity of the grid is at its limit, is provided to the flywheel electric motor.
By providing the electrical energy the flywheel electric motor, the motor rotor of the flywheel electric motors starts rotating. Since the clutch is closed, this will drive the flywheel to rotate. Thus, the electrical energy is converted into rotational energy.
In case it is intended to store the rotational energy of the flywheel for a longer period, it is preferred that the clutch is opened. Thus, there the flywheel can rotate freely with minimized energy loss. For converting the rotational energy back into electrical energy, the clutch has to be closed again.
Finally, the flywheel is coupled with the flywheel generator such that the flywheel and the flywheel generator are within a predetermined flexibility ratio. This is implemented by the clutch, especially the same clutch that has been closed in the initial method step. By these means, rotational energy of the flywheel is converted by the flywheel generator into electrical energy.
The method according to the embodiment of the present invention has the same advantages as the foundation according to the first aspect of the present invention and the wind turbine according to the second step of the present invention. Therefore, the inventive method for storing and using energy generated by a wind turbine has the advantage that with cost-efficient means and in a safe way, electrical energy generated by the generator can be temporarily stored and provided on demand by the energy storage means. With the present invention, e. g. the scenarios smoothing power output, improving black start, enhancing performance and providing backup power can be managed.
It is preferred that in a further step, the electrical energy produced by the flywheel generator is used for driving an electric motor for supporting rotation of a rotor of the wind turbine. The electric motor can be the generator of the wind turbine. This step is especially performed in a situation when the rotor of the wind turbine is not rotating and has to be accelerated to an operating rotational speed. This operation is also called “black start”. However, this step can be performed to support an already rotating rotor, e. g. when there are gusty or intermittent winds in order to prevent an unintentional stopping of the rotor. This has the advantage that, by ordinary means and in a cost-effective way, the efficiency of the wind turbine can be enhanced.
Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein:
Elements with the same function and effectiveness are denoted each in
In
In
In
In
In
Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention.
For the sake of clarity, it is to be understood that the use of “a” or “an” throughout this application does not exclude a plurality, and “comprising” does not exclude other steps or elements.
| Number | Date | Country | Kind |
|---|---|---|---|
| 19160605.2 | Mar 2019 | EP | regional |
This application is a national stage entry of PCT Application No. PCT/EP2020/055433 having a filing date of Mar. 2, 2020, which claims priority to European Patent Application No. 19160605.2, having a filing date of Mar. 4, 2019, the entire contents of which are hereby incorporated by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2020/055433 | 3/2/2020 | WO | 00 |
