WO2004011801A1 - Wind turbine with blades of variable inertia - Google Patents

Wind turbine with blades of variable inertia Download PDF

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Publication number
WO2004011801A1
WO2004011801A1 PCT/HU2003/000064 HU0300064W WO2004011801A1 WO 2004011801 A1 WO2004011801 A1 WO 2004011801A1 HU 0300064 W HU0300064 W HU 0300064W WO 2004011801 A1 WO2004011801 A1 WO 2004011801A1
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WO
WIPO (PCT)
Prior art keywords
rotor blades
inertia
masses
moment
disposed
Prior art date
Application number
PCT/HU2003/000064
Other languages
French (fr)
Inventor
Attila BÁNKUTI
Original Assignee
Bankuti Attila
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Bankuti Attila filed Critical Bankuti Attila
Priority to AU2003249103A priority Critical patent/AU2003249103A1/en
Publication of WO2004011801A1 publication Critical patent/WO2004011801A1/en

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D7/00—Controlling wind motors 
    • F03D7/02—Controlling wind motors  the wind motors having rotation axis substantially parallel to the air flow entering the rotor
    • F03D7/028—Controlling wind motors  the wind motors having rotation axis substantially parallel to the air flow entering the rotor controlling wind motor output power
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D1/00—Wind motors with rotation axis substantially parallel to the air flow entering the rotor 
    • F03D1/06—Rotors
    • F03D1/065—Rotors characterised by their construction elements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D7/00—Controlling wind motors 
    • F03D7/02—Controlling wind motors  the wind motors having rotation axis substantially parallel to the air flow entering the rotor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D7/00—Controlling wind motors 
    • F03D7/02—Controlling wind motors  the wind motors having rotation axis substantially parallel to the air flow entering the rotor
    • F03D7/04—Automatic control; Regulation
    • F03D7/042—Automatic control; Regulation by means of an electrical or electronic controller
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D9/00—Adaptations of wind motors for special use; Combinations of wind motors with apparatus driven thereby; Wind motors specially adapted for installation in particular locations
    • F03D9/10—Combinations of wind motors with apparatus storing energy
    • F03D9/12—Combinations of wind motors with apparatus storing energy storing kinetic energy, e.g. using flywheels
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2240/00—Components
    • F05B2240/20—Rotors
    • F05B2240/30—Characteristics of rotor blades, i.e. of any element transforming dynamic fluid energy to or from rotational energy and being attached to a rotor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2270/00—Control
    • F05B2270/30—Control parameters, e.g. input parameters
    • F05B2270/32—Wind speeds
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/70—Wind energy
    • Y02E10/72—Wind turbines with rotation axis in wind direction
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/16—Mechanical energy storage, e.g. flywheels or pressurised fluids
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E70/00—Other energy conversion or management systems reducing GHG emissions
    • Y02E70/30—Systems combining energy storage with energy generation of non-fossil origin

Definitions

  • the object of the invention is a method and an apparatus for increasing the efficiency of electric generating windwheels by means of adjusting the combined moment of inertia.
  • a frequently occurring problem of windwheel design is the requirement of regular and even operation. Forces exerted on the windwheel are continuously changing because of changes of wind speed. Although the windwheel is to some extent able to compensate for momentary changes of wind speed due to its inertia, that is less than enough for the efficient capturing of wind energy.
  • the development of wind power technology brought forth a number of solutions that point toward the more regular and even operation of windwheels.
  • One group of those solutions includes variable combined moment-of-inertia windwheel systems.
  • combined moment of inertia we mean the combined moment of inertia of the whole system that consists of the windwheel and the transmission. According to known methods of changing the combined moment of inertia, the moment of inertia of either part of the windwheel-transmission system can be adjusted.
  • the document DE 41 14 870 discloses a method for changing the combined moment of inertia of vertical-axis windwheels, essentially characterised by adjusting the moment of inertia of the windwheel by swinging out weights disposed at the axis of the windwheel.
  • a problem with this method is that for an effective increase of the moment inertia either large weights are needed or the weights should be swung out to a great distance from the axis of the windwheel.
  • the moment of inertia of the windwheel can be adjusted effectively and economically by means of moving masses disposed in chambers inside the rotor blades, which makes it possible to devise a method for increasing the efficiency of the windwheel.
  • Efficiency can be improved by a method that provides for a fuller capturing of the energy of the wind blowing through the windwheel by means of adjusting the moment of inertia of the rotor blades, at weak and strong winds and at varying power loads.
  • the wind is called “weak” if the windwheel is rotating under it but is not capable of generating electric power.
  • the wind is called “strong” if it partially has to be let through the windwheel without capturing its energy, while the windwheel has to be braked or the rotor blades have to be pitched out of the wind.
  • rapidly changing wind speed and “rapidly changing load” or “rapidly changing power consumption” we refer to changes that cause measurable variation in the angular velocity of the windwheel but the energy carried by them does not exceed the amount of kinetic energy that can be accumulated in the windwheel.
  • the object of our invention is therefore a method for increasing the efficiency of electric generating windwheels by adjusting the combined moment of inertia.
  • the combined moment of inertia is adjusted by changing the moment of inertia of the rotor blades of the windwheel.
  • the moment of inertia of the rotor blades is gradually raised to accumulate kinetic energy, with the generator driven by the windwheel being subsequently connected to the power grid in order to generate electricity using the kinetic energy accumulated in the moving rotor blades.
  • the moment of inertia of the rotor blades is raised prior to a change in the wind speed and/or in power consumption to accumulate kinetic energy in the rotor blades with the accumulated energy- being utilised during rapid decreases of the wind speed and/or during rapid increases of power consumption.
  • the moment of inertia of the rotor blades is changed by displacing masses disposed in chambers inside said rotor blades.
  • the individual masses disposed in the chambers of the rotor blades are moved together, in a coordinated way.
  • Another object of our invention is an apparatus for carrying out the method according to the invention, comprising hollow rotor blades and rotary masses disposed at shorter or longer radii.
  • the rotary masses are movably disposed in chambers inside the rotor blades.
  • a preferred embodiment of the apparatus is characterised by that the rotary masses are movably disposed in a tubular shaft, with the tubular shaft being disposed in chambers inside the rotor blades and with said tubular shaft being rigidly fixed to the rotor hub.
  • Another preferred embodiment of the apparatus is characterised by that mechanical motive elements are connected to masses disposed in chambers inside the rotor blades, where said masses are moved by said motive elements.
  • Yet another preferred embodiment of the apparatus is characterised by that electronic motive elements are connected to masses disposed in chambers inside the rotor blades, where said masses are moved by said motive elements.
  • Still another preferred embodiment of the apparatus is characterised by that pneumatic motive elements are connected to masses disposed in chambers inside the rotor blades, where said masses are moved by said motive elements.
  • Another preferred embodiment of the apparatus is characterised by that hydraulic motive elements are connected to masses disposed in chambers inside the rotor blades, where said masses are moved by said motive elements.
  • Still another preferred embodiment of the apparatus can be characterised by that the motive elements applied for moving the masses that are disposed in the chambers formed inside the rotor blades are connected to a rotary distributor.
  • Fig. 1 shows the kinetic energy and angular velocity of a windwheel with fixed moment of inertia as a function of time
  • Fig. 2 shows possible curves for time-kinetic energy and time-angular velocity functions of a variable moment-of-inertia windwheel
  • Fig. 3 is a flow diagram of a simple control system for the windwheel of the invention
  • Fig. 4 shows a flow diagram of a complex control system applicable with the inventive windwheel
  • Fig. 5 shows the configuration of a movably disposed, mass inside the rotor blade of the windwheel
  • Fig. 6 shows the coordinated hydraulic displacement of the masses disposed inside the rotor blades of the windwheel
  • Fig. 7 shows a variable-pitch windwheel configuration with a mass movably disposed inside the rotor blade.
  • Fig. 1 shows the kinetic energy and angular velocity of a fixed moment-of-inertia windwheel as a function of time.
  • the kinetic energy of the windwheel is determined by the angular velocity thereof, so sapping energy from the windwheel is only possible by means of lowering the rotational speed, which at the same time may impair the operating efficiency of the windwheel.
  • the speed of a variable moment-of-inertia windwheel does not determine the amount of kinetic energy accumulated in the rotor. Energy can be accumulated in or recovered from the windwheel either at constant or varying speeds.
  • Fig. 3 shows the flow diagram of a simple windwheel control system, which consists of a wind direction sensor 1, a voltmeter 9, a controller 2, a yaw control unit 3, a mass displacer unit 4, a wmdwheel 5, a transmission 6, a generator 7, and a contactor 8.
  • the controller 2 adjusts the excitation of the generator 7 with respect to voltage values measured by the voltmeter 9 and, with the help of the mass displacer unit 8, adjusts the moment of inertia of the rotor blades of the windwheel according to a programmed algorithm.
  • Fig. 4 shows the flow diagram of a complex control system for windhweels, which consists of an anemometer 10, a voltmeter 18, a controller 11, a blade pitch adjuster 12, a yaw control unit 13, a mass displacer unit 14, a windwheel 5, transmission 15, a generator 16, and a contactor 17.
  • the controller 11 uses the wind speed, wind direction and voltage values measured by the anemometer 10 and the voltmeter 18 to control the operation of the windwheel according to a pre-programmed algorithm by changing the excitation level of the generator 16, by regulating the pitch of the rotor blades by means of the blade pitch adjuster 12, and by adjusting the moment of inertia of the rotor blades through the mass displacer unit 14.
  • the moment of inertia of the rotor blades is also increased to accumulate kinetic energy in the rotating blades, with the accumulated energy being used for electricity generation in case of a rapid decrease of wind speed and/or a rapid increase of power consumption.
  • the possibility of further increasing the moment of inertia of the rotor blades should preferably be sustained to enable the apparatus to capture the energy of stronger gusts of wind and accumulate it as rotational energy of the windwheel.
  • the moment of inertia of the rotor blades is raised, as well as in case of rapidly decreasing wind speed or rapidly increasing power consumption the moment of inertia of said blades is lowered.
  • the inventive method can ensure that the windwheel speed continuously exceeds the minimum rpm that is necessary for generating electricity (determined by the utility frequency and by the electric system of the power plant).
  • the application of the method can shorten the duration and diminish the number of battery charging periods. So, apart from prolonging battery life (which in itself is advantageous for environmental protection), because a considerable amount of energy is wasted during battery charging cycles, with the method it is possible to increase the overall efficiency of the system.
  • a fraction of the rotor blade 19 of one of the embodiments of the inventive windwheel can be seen.
  • the figure shows that a chamber 22 is formed inside the blade 19, with a mass 21 being movably disposed in the chamber 22, where said mass 21 can be moved by means of a mechanical, electric, pneumatic, or hydraulic motive element 20.
  • the cross section of the chamber 22 corresponds to the cross section of the moving mass 21, or, alternatively, in case the motive element (e.g. a screw spindle) exerts torque on the mass, the walls of the chamber 22 act as guiding surfaces and therefore grooves or projections are machined into the chamber walls.
  • Fig. 6 shows the coordinated hydraulic driving mechanism of the masses 28 disposed inside the rotor blades 26 of the inventive windwheel.
  • the embodiment shown in Fig. 7 has a variable-pitch rotor.
  • the rotor blades 33 of the windwheel can be swung around a tubular shaft 31 that is firmly attached to the rotor hub and is bedded in chamber 32 of the rotor blade 33, the pitch of the rotor blades can be adjusted.
  • a mass 34 is disposed inside the tubular shaft 31 in such a way that it can be moved by the motive element 30 (as shown in Fig. 5).
  • the mechanism was spun up to three different rotational speeds, and subsequently the time that elapsed from the switching off of the motor until the stopping of the mechanism was measured both with retracted and with extended weights. For comparison, we carried out the measurements with the weights retracted only after the motor had already been switched off. Results are shown in the table below:
  • the free rotation time of the mechanism was 20-25% longer with the weights extended than with retracted weights. Free rotation time did not decrease considerably in the case when the weights were retracted after switching off the motor.
  • 1/min we measured a free rotation time of 8.8 s in case the retraction of the weights started 5 seconds after the motor had been switched off, and 8.4 s with the weights retracted immediately after switching off the motor. If the windwheel' s own inertia is taken into account the rapid changes of the wind speed or power load within the duration of 0.5-1 s can be balanced by moving the weights radially inward or outward.
  • Advantageous way of balancing the effects of changing wind speed with fixed-pitch windwheels can be the following:

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  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Sustainable Energy (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Wind Motors (AREA)

Abstract

Method for increasing efficiency of electric generating windwheels by adjusting the combined moment of inertia. The method is characterised by adjusting the combined moment of inertia by changing the moment of inertia of the rotor blades. Apparatus for carrying out the inventive method, comprising hollow rotor blades and rotary masses disposed at shorter or longer radii. The apparatus is characterised by that the rotary masses (21) are movably disposed in chambers (22) inside the rotor blades (19).

Description

WIND TURBINE WITH BLADES OF VARIABLE INERTIA
The object of the invention is a method and an apparatus for increasing the efficiency of electric generating windwheels by means of adjusting the combined moment of inertia.
A frequently occurring problem of windwheel design is the requirement of regular and even operation. Forces exerted on the windwheel are continuously changing because of changes of wind speed. Although the windwheel is to some extent able to compensate for momentary changes of wind speed due to its inertia, that is less than enough for the efficient capturing of wind energy. The development of wind power technology brought forth a number of solutions that point toward the more regular and even operation of windwheels. One group of those solutions includes variable combined moment-of-inertia windwheel systems. By combined moment of inertia we mean the combined moment of inertia of the whole system that consists of the windwheel and the transmission. According to known methods of changing the combined moment of inertia, the moment of inertia of either part of the windwheel-transmission system can be adjusted.
The document DE 41 14 870 discloses a method for changing the combined moment of inertia of vertical-axis windwheels, essentially characterised by adjusting the moment of inertia of the windwheel by swinging out weights disposed at the axis of the windwheel. A problem with this method is that for an effective increase of the moment inertia either large weights are needed or the weights should be swung out to a great distance from the axis of the windwheel.
According to the basic insight of our invention the moment of inertia of the windwheel can be adjusted effectively and economically by means of moving masses disposed in chambers inside the rotor blades, which makes it possible to devise a method for increasing the efficiency of the windwheel. Efficiency can be improved by a method that provides for a fuller capturing of the energy of the wind blowing through the windwheel by means of adjusting the moment of inertia of the rotor blades, at weak and strong winds and at varying power loads.
The wind is called "weak" if the windwheel is rotating under it but is not capable of generating electric power. The wind is called "strong" if it partially has to be let through the windwheel without capturing its energy, while the windwheel has to be braked or the rotor blades have to be pitched out of the wind.
When using the terms "rapidly changing wind speed" and "rapidly changing load" or "rapidly changing power consumption" we refer to changes that cause measurable variation in the angular velocity of the windwheel but the energy carried by them does not exceed the amount of kinetic energy that can be accumulated in the windwheel.
The object of our invention is therefore a method for increasing the efficiency of electric generating windwheels by adjusting the combined moment of inertia. The combined moment of inertia is adjusted by changing the moment of inertia of the rotor blades of the windwheel.
According to a preferred way of carrying out the inventive method, at weaker winds the moment of inertia of the rotor blades is gradually raised to accumulate kinetic energy, with the generator driven by the windwheel being subsequently connected to the power grid in order to generate electricity using the kinetic energy accumulated in the moving rotor blades.
According to another preferred way of carrying out the inventive method, the moment of inertia of the rotor blades is raised prior to a change in the wind speed and/or in power consumption to accumulate kinetic energy in the rotor blades with the accumulated energy- being utilised during rapid decreases of the wind speed and/or during rapid increases of power consumption.
According to a further preferred way of carrying out the method of the invention, during strong winds the moment of inertia of the rotor blades is raised to accumulate kinetic energy, with the accumulated energy being utilised for generating electric power in case of a decrease of the wind speed.
According to a still further preferred way of carrying out the inventive method, in case of rapidly increasing wind speed and/or rapidly decreasing power consumption the moment of inertia of the rotor blades is increased, with the moment of inertia of said rotor blades being decreased during rapid decreases of wind speed and/or rapid increases of power consumption.
According to another preferred way of carrying out the method of the invention, in case of an abrupt increase of wind speed the moment of inertia of the rotor blades is lowered, while in case of an abrupt decrease of wind speed the moment of inertia of the rotor blades is raised so that the rotational speed of the windwheel is adjusted as soon as possible to a value that corresponds to the wind speed and provides higher efficiency operation, thereby lengthening the duration of higher efficiency operation of the windwheel.
According to yet another preferred way of carrying out the inventive method the moment of inertia of the rotor blades is changed by displacing masses disposed in chambers inside said rotor blades.
According to still another preferred way of carrying out the invention the individual masses disposed in the chambers of the rotor blades are moved together, in a coordinated way.
Another object of our invention is an apparatus for carrying out the method according to the invention, comprising hollow rotor blades and rotary masses disposed at shorter or longer radii. The rotary masses are movably disposed in chambers inside the rotor blades.
A preferred embodiment of the apparatus is characterised by that the rotary masses are movably disposed in a tubular shaft, with the tubular shaft being disposed in chambers inside the rotor blades and with said tubular shaft being rigidly fixed to the rotor hub.
Another preferred embodiment of the apparatus is characterised by that mechanical motive elements are connected to masses disposed in chambers inside the rotor blades, where said masses are moved by said motive elements.
Yet another preferred embodiment of the apparatus is characterised by that electronic motive elements are connected to masses disposed in chambers inside the rotor blades, where said masses are moved by said motive elements.
Still another preferred embodiment of the apparatus is characterised by that pneumatic motive elements are connected to masses disposed in chambers inside the rotor blades, where said masses are moved by said motive elements.
Another preferred embodiment of the apparatus is characterised by that hydraulic motive elements are connected to masses disposed in chambers inside the rotor blades, where said masses are moved by said motive elements.
Still another preferred embodiment of the apparatus can be characterised by that the motive elements applied for moving the masses that are disposed in the chambers formed inside the rotor blades are connected to a rotary distributor.
The invention is now exemplified in more detail with reference to drawings where
Fig. 1 shows the kinetic energy and angular velocity of a windwheel with fixed moment of inertia as a function of time, Fig. 2 shows possible curves for time-kinetic energy and time-angular velocity functions of a variable moment-of-inertia windwheel,
Fig. 3 is a flow diagram of a simple control system for the windwheel of the invention,
Fig. 4 shows a flow diagram of a complex control system applicable with the inventive windwheel,
Fig. 5 shows the configuration of a movably disposed, mass inside the rotor blade of the windwheel,
Fig. 6 shows the coordinated hydraulic displacement of the masses disposed inside the rotor blades of the windwheel, and
Fig. 7 shows a variable-pitch windwheel configuration with a mass movably disposed inside the rotor blade.
Fig. 1 shows the kinetic energy and angular velocity of a fixed moment-of-inertia windwheel as a function of time. In this case the kinetic energy of the windwheel is determined by the angular velocity thereof, so sapping energy from the windwheel is only possible by means of lowering the rotational speed, which at the same time may impair the operating efficiency of the windwheel. As it can be seen in Fig. 2, the speed of a variable moment-of-inertia windwheel does not determine the amount of kinetic energy accumulated in the rotor. Energy can be accumulated in or recovered from the windwheel either at constant or varying speeds.
Fig. 3 shows the flow diagram of a simple windwheel control system, which consists of a wind direction sensor 1, a voltmeter 9, a controller 2, a yaw control unit 3, a mass displacer unit 4, a wmdwheel 5, a transmission 6, a generator 7, and a contactor 8. The controller 2 adjusts the excitation of the generator 7 with respect to voltage values measured by the voltmeter 9 and, with the help of the mass displacer unit 8, adjusts the moment of inertia of the rotor blades of the windwheel according to a programmed algorithm.
Fig. 4 shows the flow diagram of a complex control system for windhweels, which consists of an anemometer 10, a voltmeter 18, a controller 11, a blade pitch adjuster 12, a yaw control unit 13, a mass displacer unit 14, a windwheel 5, transmission 15, a generator 16, and a contactor 17. The controller 11 uses the wind speed, wind direction and voltage values measured by the anemometer 10 and the voltmeter 18 to control the operation of the windwheel according to a pre-programmed algorithm by changing the excitation level of the generator 16, by regulating the pitch of the rotor blades by means of the blade pitch adjuster 12, and by adjusting the moment of inertia of the rotor blades through the mass displacer unit 14.
It is widely known that wind turbines operate during a considerable part of their working time under wind conditions that permit the rotation of the windwheels but do not allow for power generation. According to the inventive method under such conditions the moment of inertia of the rotor blades is gradually raised to accumulate kinetic energy which is later used up for producing electricity by means of connecting the generator driven by the windwheel to the power grid. If the above mentioned wind conditions persist, the described steps of the method are repeated for cyclical generation of electricity.
If the wind speed exceeds the threshold of continuous power generation, the moment of inertia of the rotor blades is also increased to accumulate kinetic energy in the rotating blades, with the accumulated energy being used for electricity generation in case of a rapid decrease of wind speed and/or a rapid increase of power consumption. The possibility of further increasing the moment of inertia of the rotor blades should preferably be sustained to enable the apparatus to capture the energy of stronger gusts of wind and accumulate it as rotational energy of the windwheel.
In case the wind speed rises to such an extent that it would become necessary to waste part of the energy of the wind, the moment of inertia of the rotor blades is raised to the maximum to accumulate rotational energy that can be used for power generation during subsequent lower wind speed periods.
During periods of rapidly changing wind speed or changing power consumption, or in case of rapidly increasing wind speed or rapidly decreasing power consumption the moment of inertia of the rotor blades is raised, as well as in case of rapidly decreasing wind speed or rapidly increasing power consumption the moment of inertia of said blades is lowered. With these steps of the inventive method it is possible to provide for a more even and more regular operation that can better approximate the optimum rotational speed of the windwheel. Within a specific wind speed range the method can ensure that the windwheel speed continuously exceeds the minimum rpm that is necessary for generating electricity (determined by the utility frequency and by the electric system of the power plant). For domestic windwheel systems using batteries the application of the method can shorten the duration and diminish the number of battery charging periods. So, apart from prolonging battery life (which in itself is advantageous for environmental protection), because a considerable amount of energy is wasted during battery charging cycles, with the method it is possible to increase the overall efficiency of the system.
In Fig. 5 a fraction of the rotor blade 19 of one of the embodiments of the inventive windwheel can be seen. The figure shows that a chamber 22 is formed inside the blade 19, with a mass 21 being movably disposed in the chamber 22, where said mass 21 can be moved by means of a mechanical, electric, pneumatic, or hydraulic motive element 20. The cross section of the chamber 22 corresponds to the cross section of the moving mass 21, or, alternatively, in case the motive element (e.g. a screw spindle) exerts torque on the mass, the walls of the chamber 22 act as guiding surfaces and therefore grooves or projections are machined into the chamber walls.
Fig. 6 shows the coordinated hydraulic driving mechanism of the masses 28 disposed inside the rotor blades 26 of the inventive windwheel. A rotary distributor 24, disposed in a coaxial configuration with the rotor hub, pumps equal amounts of hydraulic fluid into the hydraulic conduits 25, by means of which the hydraulic cylinders (capable of two-way operation) move the masses 28 radially inward or outward inside the chambers 27 in a coordinated way.
The embodiment shown in Fig. 7 has a variable-pitch rotor. As the rotor blades 33 of the windwheel can be swung around a tubular shaft 31 that is firmly attached to the rotor hub and is bedded in chamber 32 of the rotor blade 33, the pitch of the rotor blades can be adjusted. A mass 34 is disposed inside the tubular shaft 31 in such a way that it can be moved by the motive element 30 (as shown in Fig. 5).
We have carried out a series of measurements on a variable moment-of-inertia rotating mechanism developed for two-bladed windwheels with power ratings of 0.3-0.7 kW. The mechamsm was driven by a three-phase electric motor having a nominal voltage of 180 V and a rated speed of 1470 rpm at 50 Hz, applying 070 mm and 0280 mm V-belt discs and a reducer. The rotational speed was adjusted using a variable frequency drive unit. The inner diameter of the tubular shaft of the mechanism was 36 mm. Movable weights of 0.35 kg each were mounted inside the tubular shaft using a wire rope. The weights could move symmetrically with respect to the axis of rotation, in the range of 160-900 mm. The mechanism was spun up to three different rotational speeds, and subsequently the time that elapsed from the switching off of the motor until the stopping of the mechanism was measured both with retracted and with extended weights. For comparison, we carried out the measurements with the weights retracted only after the motor had already been switched off. Results are shown in the table below:
Figure imgf000008_0002
As it can be seen from the results, the free rotation time of the mechanism was 20-25% longer with the weights extended than with retracted weights. Free rotation time did not decrease considerably in the case when the weights were retracted after switching off the motor. At 294 1/min we measured a free rotation time of 8.8 s in case the retraction of the weights started 5 seconds after the motor had been switched off, and 8.4 s with the weights retracted immediately after switching off the motor. If the windwheel' s own inertia is taken into account the rapid changes of the wind speed or power load within the duration of 0.5-1 s can be balanced by moving the weights radially inward or outward. Advantageous way of balancing the effects of changing wind speed with fixed-pitch windwheels can be the following:
• In case an abrupt increase occurs in the wind speed, the weights are moved radially inward in order to rapidly increase the speed of the windwheel and reach the rpm dictated by the wind speed as soon as possible, thereby increasing the duration of increased-efficiency operation.
• In case the wind speed falls back abruptly, the weights are moved radially outward in order to reach the lower rpm dictated by the wind speed as soon as possible, so that way the windwheel will move the air for a shorter time and also the braking loss can be reduced, with the duration of increased-efficiency operation being extended at the same time.
The change of the angular velocity ω of the windwheel can be estimated (disregarding losses) as a function of the combined moment of inertia Θ using the equation
Figure imgf000008_0001
l/2Θ ω2 , by the expression co2 /ω1=(Θ1/ Θ2)1/2.

Claims

Claims
Method for increasing efficiency of electric generating windwheels by adjusting the combined moment of inertia, characterised by that the combined moment of inertia is adjusted by changing the moment of inertia of the rotor blades. The method according to Claim 1, characterised by that at weaker winds the moment of inertia of the rotor blades is gradually raised to accumulate kinetic energy, with the generator driven by the windwheel being subsequently connected to the power grid in order to generate electricity using the kinetic energy accumulated in the moving rotor blades. The method according to Claim 1, characterised by that the moment of inertia of the rotor blades is raised prior to a change in the wind speed and/or in power consumption to accumulate kinetic energy in the rotor blades with the accumulated energy being utilised during rapid decreases of the wind speed and/or during rapid increases of power consumption. The method according to Claim 1, characterised by that during strong winds the moment of inertia of the rotor blades is raised to accumulate kinetic energy, with the accumulated energy being utilised for generating electric power in case of a decrease of the wind speed. The method according to Claim 1, characterised by that in case of rapidly increasing wind speed and/or rapidly decreasing power consumption the moment of inertia of the rotor blades is increased, with the moment of inertia of said rotor blades being decreased during rapid decreases of wind speed and/or rapid increases of power consumption. The method according to Claim 1, characterised by that in case of an abrupt increase of wind speed the moment of inertia of the rotor blades is lowered, while in case of an abrupt decrease of wind speed the moment of inertia of the rotor blades is raised so that the rotational speed of the windwheel is adjusted as soon as possible to a value that corresponds to the wind speed and provides higher efficiency operation, thereby lengthening the duration of higher efficiency operation of the wmdwheel. The method according to any one of the preceding Claims, characterised by that the moment of inertia of the rotor blades is changed by displacing masses disposed in chambers inside said rotor blades. The method according to Claim 7, characterised by that the individual masses disposed in the chambers of the rotor blades are moved together, in a coordinated way. Apparatus for carrying out the method according to Claim 1, comprising hollow rotor blades and rotary masses disposed at shorter or longer radii, characterised by that the rotary masses (21, 34) are movably disposed in chambers (22, 32) inside the rotor blades (19, 33). The apparatus according to Claim 9, characterised by that the rotary masses (34) are movably disposed in a tubular shaft (31), with the tubular shaft (31) being disposed in chambers (32) inside the rotor blades (33) and with said tubular shaft (31) being rigidly fixed to the rotor hub. The apparatus according to Claims 9 and 10, characterised by that mechanical motive elements (20, 30) are connected to the masses (21, 34), where said masses (21, 34) are disposed in chambers (22, 32) inside the rotor blades (19, 33). The apparatus according to Claims 9 and 10, characterised by that electronic motive elements (20, 30) are connected to the masses (21, 34), where said masses (21, 34) are disposed in chambers (22, 32) inside the rotor blades (19, 33). The apparatus according to Claims 9 and 10, characterised by that pneumatic motive elements (20, 30) are connected to the masses (21, 34), where said masses (21, 34) are disposed in chambers (22, 32) inside the rotor blades (19, 33). The apparatus according to Claims 9 and 10, characterised by that hydraulic motive elements (20, 30) are connected to the masses (21, 34), where said masses (21, 34) are disposed in chambers (22, 32) inside the rotor blades (19, 33). The apparatus according to any one of Claims 12-14, characterised by that the motive elements (20, 30) applied for moving the masses (21, 34) that are disposed in the chambers (22, 32) formed inside the rotor blades (19, 33) are connected to a rotary distributor.
PCT/HU2003/000064 2002-07-31 2003-07-31 Wind turbine with blades of variable inertia WO2004011801A1 (en)

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KR100913133B1 (en) * 2008-07-23 2009-08-19 우주엘엔티(주) Rotor blade of a wind energy facility
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WO2012111913A2 (en) * 2011-02-16 2012-08-23 Lee Seung Geun Rotary body for a wind power generating apparatus
WO2013014463A2 (en) 2011-07-26 2013-01-31 JELJALANE, Laila Leena Turbine Blade
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US20130195636A1 (en) * 2012-01-31 2013-08-01 Thomas Bertram Poole Wind turbine
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WO2012111913A2 (en) * 2011-02-16 2012-08-23 Lee Seung Geun Rotary body for a wind power generating apparatus
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US20130195636A1 (en) * 2012-01-31 2013-08-01 Thomas Bertram Poole Wind turbine
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