Wind turbine provided with a controller for adjusting active annular plane area and the operating method thereof Number:7,436,085 from the United States Patent and Trademark Office (PTO) owispatent A wind turbine which varies an active annular plane area by composing such that blades are attached to a cylindrical rotor movable in the radial direction of the rotor, the blades being reciprocated in the radial direction by means of a blade shifting mechanism connected to the root of each blade, or the blade itself is divided so that the outer one of the divided blade is movable in the radial direction. With the construction, the wind turbine can be operated with a maximum output within the range of evading fatigue failure of the blades and rotor by adjusting the active annular plane area in accordance with wind speed.<H controller, operating, Wind, turbine, pr, 7436085.html, Patent, pto, 7436085

Title: Wind turbine provided with a controller for adjusting active annular plane area and the operating method thereof

Abstract: A wind turbine which varies an active annular plane area by composing such that blades are attached to a cylindrical rotor movable in the radial direction of the rotor, the blades being reciprocated in the radial direction by means of a blade shifting mechanism connected to the root of each blade, or the blade itself is divided so that the outer one of the divided blade is movable in the radial direction. With the construction, the wind turbine can be operated with a maximum output within the range of evading fatigue failure of the blades and rotor by adjusting the active annular plane area in accordance with wind speed.

Patent Number: 7,436,085 Issued on 10/14/2008 to Shibata, et al.

Inventors: Shibata; Masaaki (Nagasaki, JP), Hayashi; Yoshiyuki (Nagasaki, JP), Furukawa; Toyoaki (Nagasaki, JP), Yatomi; Yuuji (Nagasaki, JP), Kato; Eiji (Nagasaki, JP), Teramoto; Yoshinari (Nagasaki, JP), Miyake; Hisao (Nagasaki, JP), Hayakawa; Koshi (Nagasaki, JP)
Assignee: Mitsubishi Heavy Industries Ltd. (Tokyo, JP)

Appl. No.: 11/123,135

Filed: May 6, 2005

Related U.S. Patent Documents


Application Number	Filing Date	Patent Number	Issue Date
10338888	Jan., 2003	7071578

Foreign Application Priority Data


Jan 10, 2002 [JP]			2002-003396
Jan 11, 2002 [JP]			2002-004332
Feb 22, 2002 [JP]			2002-046193
Sep 13, 2002 [JP]			2002-268240
Sep 13, 2002 [JP]			2002-268241

Current U.S. Class: 290/55 ; 290/44

Current International Class: H02P 9/04 (20060101); F03D 9/00 (20060101)

Field of Search: 290/55,54,44,43 416/1,132B,11,32,122 415/7,2.1,4.2,907,4.1 60/398

References Cited [Referenced By]

U.S. Patent Documents


252835	January 1882	Chamberlain
2094941	October 1937	Burkhartsmeier
2360791	October 1944	Putnam
4083651	April 1978	Cheney et al.
4084921	April 1978	Norz
4189648	February 1980	Harner
4366386	December 1982	Hanson
4426192	January 1984	Chertok et al.
4431375	February 1984	Carter et al.
4522561	June 1985	Carter et al.
4533297	August 1985	Bassett
4545728	October 1985	Cheney, Jr.
4710101	December 1987	Jamieson
6441507	August 2002	Deering et al.
6726439	April 2004	Mikhail et al.
6752595	June 2004	Murakami
2003/0044274	March 2003	Deane et al.
2003/0223868	December 2003	Dawson et al.
2003/0230898	December 2003	Jamieson et al.

Foreign Patent Documents


07-42664	Feb., 1995	JP
07042664	Feb., 1995	JP
9-79127	Mar., 1997	JP

Primary Examiner: Gonzalez; Julio C.
Attorney, Agent or Firm: Edwards Angell Palmer & Dodge LLP

Parent Case Text

This application is a Divisional application of U.S. patent application Ser. No. 10/338,888, now U.S. Pat. No. 7,071,578 filed Jan. 9, 2003.

Claims

What is claimed is:

1. A wind turbine with an active annular plane area control mechanism comprising a plurality of blades attached to a rotor head via a plurality of connecting elbows corresponding to said plurality of blades for transmitting the wind force acting on the blades to the output shaft of the wind turbine connected to the rotor head, wherein each blade is attached to an end side of said corresponding connecting elbow having a fixed bend angle, the other end side is attached to the periphery of the rotor head for rotation, a connecting elbow driving device is provided for rotating each of said connecting elbows, and the blades can be tilted in the direction of the axis of the rotor head to adjust an active annular plane area.

2. The wind turbine with an active annular plane area control mechanism according to claim 1, further comprising a wind speed detector for detecting the speed of the wind acting on the blades, and a controller which calculates average wind speed during a certain period of time from the wind speed detected continuously by said wind speed detector and the tilt angle of the blades optimal for the average wind speed and controls said connecting elbow driving device so that the blades are tilted to the calculated angle.

3. The wind turbine with an active annular plane area control mechanism according to claim 1, wherein said connecting elbow driving device comprises a ring gear fixed to said other end of the connecting elbow concentric with the axis of rotation thereof, a pinion meshing with the ring gear, a reversible motor for rotating the pinion, and a motor control device for controlling the rotation of the motor according to the output signal from said controller.

4. An operating method of the wind turbine with an active annular plane area control mechanism comprising a plurality of blades attached to a rotor head via a plurality of connecting elbows corresponding to said plurality of blades for transmitting the wind force acting on said plurality of blades to the output shaft of the wind turbine connected to the rotor head, wherein the speed of the wind acting on the blades is detected, average wind speed during a certain period of time is calculated from the wind speed detected continuously by said wind speed detector, the active annular plane area optimal for the average wind speed is calculated, and the rotation angle of said connecting elbows is adjusted so that the active annular plane area becomes equal to said calculated value through composing such that each blade is attached to each of a said plurality of connecting elbows attached to the rotor head for rotation so that the blade is capable of being tilted in the direction of the axis of rotation of the rotor head by rotating said connecting elbow.

5. An operating method of the wind turbine with an active annular plane area control mechanism comprising a plurality of blades attached to a rotor head via a plurality of connecting elbows corresponding to said plurality of blades for transmitting the wind force acting on the blades to the output shaft of the wind turbine connected to the rotor head, wherein the speed of the wind acting on said plurality of blades is detected, average wind speed during a certain period of time is calculated from the wind speed detected continuously by said wind speed detector, the active annular plane area optimal for the average wind speed is calculated, and the rotation angle of said connecting elbows is adjusted so that the active annular plane area becomes equal to said calculated value through composing such that each blade is capable of being tilted in the direction of the axis of rotation of the rotor head.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is a wind turbine generator and relates to a wind turbine having a plurality of blades attached to a rotor, the rotating force generated by allowing wind force to act on the blades being transmitted to the output shaft of the rotor, wherein a controller of an active annular plane area is provided for making it possible to change the active annular plane area of the wind turbine by reciprocating each of the blades in a radial direction or by slanting the rotor and the operating method thereof.

2. Description of the Related Art

A wind turbine power plant having high capacity of generating electric power by installing a plurality of wind turbine electric power generator units, each of which utilizes the rotating force generated by applying wind force to a plurality of blades attached to a rotor to drive a generator via the wind turbine shaft, is constructed at high elevation such as the top of a hill or mountain or at a place where high wind velocity can be received, such as above the sea.

The wind turbine apparatus used for driving an electric generator or other purposes is constructed, as shown in FIG. 1 of patent document 1 (Japanese Patent Application Publication No. 5-60053) and In FIG. 1 of patent document 2 (Japanese Patent Application Publication No. 5-60053)), such that a plurality of blades are attached to the periphery of a rotor head and the rotating force generated by wind force is transmitted to the turbine shaft via the rotor head. Desired or determined electric power generation is maintained by changing the pitch angle of the blades attached to the rotor in accordance with the wind speed and required electric power while controlling to adjust the blade pitch angle to the angle optimal for the wind speed blowing when the apparatus is in operation.

In the wind turbine of FIG. 1 of patent document 3 (Japanese Patent Application Publication No. 2001-99045), blades are attached to a rotor head such that the blades are supported for rotation via bearings fixed to the rotor head, bevel gear mechanism is provided inside the rotor head to be driven by a servomotor. The pitch angle of the blades is changeable by rotating the blades relative to the rotor head by the servomotor via the bevel gear mechanism.

The output power of the wind turbine generated by the action of wind is about proportional to active annular plane area, i.e., the area of the annular plane formed between the circumscribed circle of the blade tips and the inscribed circle of the blade roots. S=.pi.(L.sup.2-I.sup.2) (1) where S is active annular plane area, L is radius of the circumscribed circle, and I is radius of the inscribed circle.

In order to increase the output power of a wind turbine, it is required that radius L is increased or the difference between L and I, that means the length of the blade is increased.

The power P.sub.w that the wind passing through active annular plane area S has, is P.sub.w=kSV.sup.3 (2) where V is wind speed, and k is air density divided by 2.

As wind speed depends on weather conditions at the location of the wind turbine, the output of the wind turbine, that is the electric power generated in the case of wind turbine electric generator, can be increased by increasing the active annular plane area.

However, in the case where the active annular plane area is increased for increasing output power, the rotating components such as the blades and rotor are more likely to be broken by fatigue failure resulting from being subjected to repeated excessively fast wind speed V of a gust of wind, etc., which sometimes occurs according to weather conditions, although the output is increased.

With the prior art disclosed in patent documents 1 and 2, because the blades are fixed to the rotor head of a somewhat larger diameter than the rotor shaft, it is difficult to design a longer blade, that is, to increase radius L, so that there is a limit for increasing the output of a wind turbine. Further, when blade length is increased to the maximum to increase active annular plane area for increasing the output of the wind turbine, the rotating components such as the blades and rotor tend to be broken by fatigue failure due to repeated occurrence of a gust of wind, etc., of excessively increased speed.

The wind turbine of patent document 3 has a means for changing blade pitch angle by rotating the blades relative to the rotor head, however, the active annular plane area is not variable but constant, and there remains also the problem that the rotating components such as the blades and rotor tend to be broken by fatigue failure resulting from being subjected to repeated excessively increased speed of a gust of wind, etc.

SUMMARY OF THE INVENTION

The first objective of the present invention is to provide a wind turbine with which an active annular plane area of the blades is variable corresponding to wind speed by changing the radial positioning of the blades and the output of the wind turbine can be maintained at a maximum while avoiding the occurrence of fatigue failure.

The second objective of the present invention is to provide a wind turbine with which an active annular plane area of the blades is variable corresponding to wind speed by changing the effective length of blades and the output of the wind turbine can be maintained at a maximum while avoiding the occurrence of fatigue failure.

The third objective of the present invention is to provide a wind turbine with which an active annular plane area of the blades is variable corresponding to operating conditions, such as wind speed, etc., and at the same time corresponding to the stress of the rotating components of the wind turbine by changing the effective length of blades and the output of the wind turbine can be maintained at a maximum while avoiding the occurrence of fatigue failure.

The fourth objective of the present invention is to provide a wind turbine which is provided with an active annular plane area adjusting device which makes it possible to change an active annular plane area corresponding to the speed of the wind in the direction of the axis of rotation of the rotor head of the wind turbine by connecting the blades to the rotor head by means of rotatable connecting elbows and the output of the wind turbine can be maintained at a maximum while avoiding the occurrence of fatigue failure.

The fifth objective of the present invention is to provide a wind turbine with which an active annular plane area of the blades is variable corresponding to wind speed by tilting the blades toward the axis of rotation and the output of the wind turbine can be maintained at a maximum while avoiding the occurrence of fatigue failure.

To attain the objectives, the wind turbine is composed as follows.

The first means of the present invention is a wind turbine with an active annular plane area control mechanism comprising a plurality of blades attached to a rotor for transmitting the wind force acting on the blades to the output shaft of the wind turbine connected to the rotor, wherein said rotor is formed in a cylindrical shape, said blades are attached to said rotor movable in a radial direction of the rotor, a blade shifting mechanism is connected to the roots of said blades for reciprocating said blades in the radial direction, and an active annular plane area is changeable by moving said blades in the radial direction through said blade shifting mechanism.

The rotor of said wind turbine has preferably radial fit holes located at an equal spacing in the circumferential direction, said blades are received in said radial fit holes for reciprocation, and said blade shifting mechanism is provided in the hollow of said rotor.

Said wind turbine is preferably provided with a wind speed detector for detecting the speed of the wind acting on said blades and a control device which receives the detected wind speed from said wind speed detector, calculates a desired active annular plane area and the radial position corresponding to said active annular plane area on the basis of said detected wind speed, and outputs the result to said blade shifting mechanism.

Said blade shifting mechanism preferably comprises a plurality of screw bars received for rotation in radial holes provided in the cylindrical wall of said rotor, sleeves each of which is engaged with each of the screw bars, links each of which connects each of said links and said blades, pinions each of which is fixed to each of said screw bars at the inner side part thereof, and a driving gear meshing with said pinions and driven by a driving device such as a motor; and said blades are reciprocated in the radial direction through the expansion or contraction of said links resulting from the shifting of said sleeves by the rotation of said screw bars when said driving gear is rotated by said driving device.

Further, said blade shifting mechanism preferably comprises a supporting element located in the center part of said rotor; pairs of links capable of being expanded or contracted, each pair connecting the root of each blade to said supporting element, screw bars each connecting one side of each of said pairs of links, and driving devices such as motors for rotating said screw bars; and the radial position of said blades is changeable by expanding or contracting said pairs of links through rotating said screw bars by said driving devices.

Yet further, said blade shifting mechanism preferably comprises two rings, an outer ring and an inner ring, provided concentrically with the center axis of said rotor rotatable in the direction contrary to each other, pairs of links capable of being expanded or contracted, each pair connecting the root of each blade to the outer ring with one of the pair and to the inner ring with the other of the pair, a driving device for rotating said two rings in the direction contrary to each other, and a supporting element located in the center part of said rotor and supports one of said rings; and said blades can be reciprocated in the radial direction by expanding or contracting said pairs of links through rotating said rings in the direction contrary to each other.

Still further, said blade shifting mechanism preferably comprises a slider received in a slider receiver fixed to the rotor 2 for sliding in the radial direction of the rotor, the slider having a screw thread hole directed in the radial direction, links each of which has a curved convex surface at an end thereof to be engaged in a convex of curved surface formed in said slider receiver to be supported for swinging, the other end having an elongated hole through which the link is connected to the lower end part of the blade via a pin fixed to said lower part, a screw bar engaged with said screw thread hole of said slider, and a driving device such as a motor for rotating said screw bar; and the blades can be reciprocated in the radial direction via said elongated hole and said pin engaging in said hole by moving said slider in the radial direction in said slider receiver through rotating said screw bar by the rotation of said driving device.

The second means of the present invention is an operating method of the wind turbine with an active annular plane area control mechanism comprising a plurality of blades attached to a rotor for transmitting the wind force acting on the blades to the output shaft of the wind turbine connected to the rotor, wherein the speed of the wind acting on the wind turbine is detected, and the blades attached to the rotor capable of being moved in the radial direction of the rotor are moved in radial outward directions to increase an active annular plane area as the detected wind speed decreases and the blades are moved in radial inward directions to decrease the active annular plane area as the detected wind speed increases.

The third means of the present invention is a wind turbine with an active annular plane area control mechanism of a darrieus type wind turbine which has supporting elements provided along a vertical wind turbine shaft and a stage or a plurality stages of a plurality of sets of blades, each of which is supported by said supporting elements at both ends thereof and located along said vertical wind turbine shaft, said wind turbine shaft being rotated by the aerodynamic lift effected by the wind acting on said blades, wherein said supporting elements are capable of being shifted in the radial direction perpendicular to said wind turbine shaft, a blade shifting mechanism is provided for changing the radial position of said set of blades by shifting said supporting elements in the radial direction, by which the radius of rotation of said blades can be changed.

Said wind turbine of the third means is preferably provided with a wind speed detector for detecting the speed of the wind acting on said wind turbine and a control device which calculates the desired active annular plane area and the shift amount to realize said desired active annular plane area and allows the blades to be shifted in radial outward directions by shifting said supporting elements through said blade shifting mechanism in order to increase the active annular plane area as said detected wind speed decreases, allows the blades to be shifted in radial inward directions in order to decrease the active annular plane area as said detected wind speed increases.

Said blade shifting mechanism in the third means preferably comprises screw bars erected upright parallel to said vertical wind turbine shaft, each screw bar having right-hand and left-hand screw thread parts cut by turns along the bar, one or a plurality of pairs of shifting elements, one of the pair being engaged with the right-hand or left-hand threads of the two screw bars and the other being engaged on the contrary with the left-hand or right-hand threads of the two screw bars so that the pair of the shifting elements move in the direction contrary to each other by the rotation of said screw bars in the same direction, pairs of links each for connecting each supporting element to each of the pair of shifting elements, and a driving device for rotating said screw bars; and the blades can be shifted in the radial direction by shifting said supporting elements in the radial direction through allowing the pair of shifting elements to move in the direction contrary to each other by rotating said screw bars in the same direction by said driving device, said supporting elements being shifted in the radial direction by means of said pair of links connecting itself to the pair of shifting elements.

It is preferable in the third means that a driving device is connected to an end side of one of said screw bars and said shifting elements engaging with said screw bars are moved simultaneously.

The fourth means of the present invention is an operating method of the wind turbine with an active annular plane area control mechanism of a darrieus type wind turbine which has supporting elements provided along a vertical wind turbine shaft and a stage or a plurality stages of a plurality of sets of blades each of which is supported by said supporting elements at both ends thereof and located along said vertical wind turbine shaft, said wind turbine shaft being rotated by the aerodynamic lift effected by the wind acting on said blades, wherein the wind turbine is constructed so that the radial position of the blades is changeable by shifting the supporting elements in the radial direction perpendicular to the vertical turbine shaft, the speed of the wind acting on the blades is detected, and the blades are moved in radial outward directions by means of said supporting elements to increase the active annular plane area as the detected wind speed decreases and the blades are moved in radial inward directions to decrease the active annular plane area as the detected wind speed increases.

According to the first to fourth means, wind speed is detected by the wind speed detector and inputted to the controller. In the controller, relations between wind turbine output P, wind speed V, and active annular plane area S are set beforehand, and a relation between the limit wind speed with which fatigue failure occurs in the rotating components such as the blades and rotor and active annular plane area. The controller calculates an optimal active annular plane area corresponding to the detected wind speed when the detected wind speed is inputted, and the result is outputted to the driving device of the blade shifting mechanism.

Each blade is moved in the radial direction through the blade shifting mechanism guided by radial holes provided in the cylindrical wall of the rotor or in the darrieus type wind turbine the radial position of each blade can be changed by moving the supporting elements supporting each blade in the radial direction and the blades are kept in the position with which the active annular plane area is equal to said calculated optimal active annular plane area.

By this, it is possible that the blades are shifted in radial outward directions by shifting said supporting elements through said blade shifting mechanism in order to increase the active annular plane area as said detected wind speed decreases, and they are shifted in radial inward directions in order to decrease the active annular plane area as said detected wind speed increases. Therefore, the wind turbine can be operated with the radial position of the blades, with which the output as high as possible is obtainable while evading the occurrence of fatigue failure of the rotating components such as the blades and rotor under the present wind speed.

Accordingly, by the means mentioned above, the wind turbine can be operated while always automatically controlling blade length so that the occurrence of fatigue failure of the rotating components, such as the blades and rotor, is reduced, and at the same time the wind turbine is operated with the optimal active annular plane area which ensures the maximum output of the wind turbine in the range capable of evading the fatigue failure. Accordingly, the operation of the wind turbine is possible with the optimal maximum output with elongated fatigue life of the rotating elements such as the blades and rotor.

The fifth means of the present invention is a wind turbine with an active annular plane area control mechanism comprising a plurality of blades attached to a rotor for transmitting the wind force acting on the blades to the output shaft of the wind turbine connected to the rotor, wherein each of said blades is configured so that blade length can be changed in the total length of the blade or in a certain length from the middle up to the tip of the blade, a blade length adjusting mechanism is provided for adjusting the blade length of each of the blades, and the active annular plane area is changeable by changing the radial position of the blades relative to the rotor by said blade length adjusting mechanism.

Each of said blades is preferably formed in a bellows shape expandable and contractible in the radial direction of the rotor, a plurality of air chambers to which air is supplied or from which air is exhausted being formed inside said bellows-shaped blade continuously in the direction of blade length, and said blade length adjusting mechanism is composed of an air supply device for producing pressurized air and an air tube for supplying the pressurized air to each of said air chambers, the tube connecting said air supply device to each air chamber and being movable in the blade length direction as said bellows-shaped blade expands or contracts.

It is preferable in the fifth means that there are provided air valves attached to said air tube for opening or closing outlets of the air into each of said air chambers and an air control device for controlling the opening and closing of said air valves and the operation of said air supply device.

It is also preferable that there are provided a flexible string, such as wire connected to the top of the blade, and a flexible string driving device for expanding or contracting the blade by drawing out or in the flexible string in the blade length direction to change the blade tip diameter.

Further, it is preferable that each of said blades is divided into a variable length blade part and a blade body fixed to the rotor and connecting to the root of said variable length blade part, said variable length blade part is supported by said blade body capable of being tilted around the supporting shaft of the variable length blade part, and said blade length adjusting mechanism is composed as a blade tilting mechanism for tilting said variable length blade part around said supporting shaft by a driving device by means of a link mechanism.

Yet further, it is preferable that each of said blades is divided into a variable length blade part and a blade body fixed to the rotor and connecting to the root of said variable length blade part, said variable length blade part is received in the guide hole of said blade body capable of being moved in the direction of blade length, and said blade length adjusting mechanism is composed as a blade reciprocating device for reciprocating the variable length blade part guided along said guide hole by a reversible driving device, such as a reversible motor, in order to change the blade tip diameter.

Still further, each of said variable length blade parts has preferably a rack fixed to the lower end thereof, and said blade reciprocating device is composed such that a pinion which meshes with said rack is fixed to the output shaft of said reversible driving device to convert the rotating motion of the reversible driving device to the reciprocating motion of the variable length blade part.

Yet still further, each of said variable length blade parts has preferably a shaft with female screw thread fixed to the lower end thereof, and said blade reciprocating device is composed such that a screw bar which engages in the female screw thread of said shaft is fixed to the output shaft of said reversible driving device to convert the rotating motion of the reversible driving device to the reciprocating motion of the variable length blade part.

Further in the fifth means, each of said blades is divided into a variable length blade part and a blade body fixed to the rotor and connecting to the root of said variable length blade part, said variable length blade part is composed of a front core made of hard material such as a metal pipe extended downward in the direction of blade length to form an actuating shaft part, a rear core made of wire of soft material, and a blade shell made of flexible material defining a blade profile between said front core and rear core, said actuating shaft part of the front core is received for sliding in the direction of blade length in a bearing hole provided in the blade body, and said blade reciprocating device is composed as a blade reciprocating device for reciprocating said variable length blade part through reciprocating said actuating shaft part of the front core by means of a reversible driving device such as a reversible motor.

According to the fifth means, an active annular plane area can be adjusted to an optimal area corresponding to wind speed even during the operation of the wind turbine by varying the tip diameter of blades by changing the effective blade length through shifting the blades in the radial direction of the rotor by means of the blade length adjusting mechanism, or by extending or contracting the blade itself in the blade length direction.

By this, it is possible to operate the wind turbine so that an output as high as possible is obtained while evading the occurrence of fatigue failure of the rotating components, such as the blades and rotor, under the present wind speed by adjusting the effective length of each of the blade itself so that the blade tip diameter is increased by increasing the effective blade length to increase active annular plane area as wind speed decreases, on the other hand the blade tip diameter is decreased by decreasing the effective length to decrease active annular plane area as wind speed increases.

Therefore, by the fifth means, the wind turbine can be operated while always automatically controlling blade length so that the occurrence of fatigue failure of the rotating components such as the blades and rotor, and at the same time the wind turbine is operated with the optimal active annular plane area which insures a maximum of the wind turbine output while avoiding fatigue failure.

Accordingly, the operation of wind turbine is possible with an optimal maximum output with elongated fatigue life of the rotating elements such as the blades and rotor.

Further, the blade length varying mechanism is constructed light in weight and can be provided inside the blade, so an active annular plane area is variable without accompanying the increase in the weight of blade.

Further, according to the fifth means, active annular plane area can be changed by changing the effective blade length by supplying or exhausting air to or from each of the independent air chamber formed continuously in the direction of the length the blade formed in a bellows shape by opening or closing air valves through an air control device.

The blade tip diameter can be varied by extending or contracting said blade through drawing out or in the flexible string such as wire connected to the top of the blade by the flexible string driving device.

According to the fifth means, the projected area of the surface of revolution of the blade in the direction of the axis of rotation of the rotor, i.e., active annular plane area is changeable by changing the tilt angle of each of the variable blade length parts through swinging each variable blade length part which is supported at the root part thereof for rotation by the supporting shaft fixed to the blade body via the link mechanism.

Further, according to the fifth means, an active annular plane area is changeable by changing the blade tip diameter by reciprocating each variable length blade part fit for sliding in the guide hole of each blade body via a rotation-reciprocation converting mechanism such as pinion-rack mechanism or screw bar-nut mechanism through the rotation of the reversible driving device such as a reversible motor.

Further, according to the fifth means, the active blade tip diameter is changeable by reciprocating each variable length blade part by sliding the actuating shaft which is the extended part of the front core of the variable length blade part and fit for sliding in the guide hole of each blade body via a rotation-reciprocation converting mechanism, such as pinion-rack mechanism, through the rotation of the reversible driving device, such as a reversible motor.

Further, according to the present invention, each of the variable length blade parts composed of a front core made of wire, a rear core made of soft wire, and a blade shell made of flexible material defining blade profile between the front core and rear core, so that the variable length blade part is made to be light in weight, and in addition to that, as the blade shell is made of flexible material, the variable length blade part can be folded, which results in ease of transportation.

The sixth means of the present invention is a wind turbine with an active annular plane area control mechanism comprising a plurality of blades attached to a rotor for transmitting the wind force acting on the blades to the output shaft of the wind turbine connected to the rotor, wherein each of said blades is divided into a variable length blade part and a blade body fixed to the rotor and connecting to the root of said variable length blade part, and there are provided operating conditions detectors for detecting the operating conditions of the wind turbine, a blade length controller for comparing each of the detected signals of the operating conditions inputted from said operating conditions detectors with each of the predetermined permissible values of operating conditions and calculating the amounts of active annular plane area and blade length to be adjusted for optimal operation based on the result of comparisons, and a blade length adjusting mechanism for changing blade length based on the calculated blade length inputted from said blade length controller.

It is preferable that said operating condition detectors include at least one among a wind speed detector for detecting the speed of the wind acting on the wind turbine, a rotation speed detector for detecting the rotation speed of a rotating component of the wind turbine including the rotor, and a load detector for detecting the load of the wind turbine, and said blade length controller compares the signal of detected wind speed from said wind speed detector with a predetermined permissible value of wind speed, or compares the signal of detected rotation speed from said rotation speed detector with a predetermined permissible value of rotation speed, or compares the signal of detected load from said load detector with a predetermined permissible value of load, calculates the amounts of active annular plane area and blade length to be adjusted for optimal operation concerning at least one among wind speed, rotation speed, and load, and outputs the result to said blade length adjusting mechanism.

It is also preferable that a blade stress detector is provided for detecting the stress occurred in the blade, and said blade length controller is composed so that the amounts of active annular plane area and blade length to be adjusted for optimal operation are calculated based on both the result of comparison of the signal of detected blade stress with a predetermined permissible value of blade stress and the result of comparisons of the detected signals of the operating conditions with predetermined values of operating conditions and the calculation result is outputted to said blade length adjusting mechanism.

Further, it is preferable that said operating condition detectors include at least one among a wind speed detector for detecting the speed of the wind acting on the wind turbine, a rotation speed detector for detecting the rotation speed of a rotating component of the wind turbine including the rotor, and a load detector for detecting the load of the wind turbine, a blade stress detector is provided for detecting the stress occurred in the blade, and said blade length controller compares the signal of detected blade stress inputted from said blade stress detector with a predetermined permissible stress, and compares the signal of detected wind speed from said wind speed detector with a predetermined permissible value of wind speed, or compares the signal of detected rotation speed from said rotation speed detector with a predetermined permissible value of rotation speed, or compares the signal of detected load from said load detector with a predetermined permissible value of load, calculates the amounts of active annular plane area and blade length to be adjusted for optimal operation concerning at least one among wind speed, rotation speed, and load while maintaining the blade stress at or near the predetermined permissible stress, based on the result of said comparisons and outputs the result to said blade length adjusting mechanism.

The seventh means of the present invention is an operating method of the wind turbine with an active annular plane area control mechanism comprising a plurality of blades attached to a rotor for transmitting the wind force acting on the blades to the output shaft of the wind turbine connected to the rotor, each of said blades being configured so that blade length can be changed in the total length of the blade or in a certain length from the middle up to the tip of the blade, wherein the operating condition of the wind turbine is detected, the detected operating condition signals are compared with predetermined permissible values, the amounts of active annular plane area and blade length to be adjusted for optimal operation concerning the operation condition are calculated, and the blade length is changed according to the calculation result.

It is preferable in the seventh means that the blade stress is detected, the detected signal of the blade stress is compared with a predetermined permissible blade stress, the amounts of active annular plane area and blade length to be adjusted for optimal operation concerning both said operation condition and said blade stress are calculated, and the blade length is changed according to the calculation result.

According to the sixth and seventh means, each of said blades is composed such that a certain length of the blade from the middle to the tip thereof is variable and active annular plane area is changeable by changing the length of the variable length blade part by means of the blade length adjusting mechanism, the speed of the wind acting on the wind turbine is detected by the wind speed detector, the rotation speed of a rotating component including the rotor is detected by the rotation speed detector, the load(output)of the wind turbine is detected by the load detector, further the stress of the blade is detected by the blade stress detector, and the detected values are inputted to the blade length controller.

The blade length controller compares said detected wind speed with the predetermined permissible wind speed, or compares the detected rotation speed with the predetermined permissible rotation speed, or compares the detected load with the predetermined permissible load, and further compares the detected blade stress with the predetermined permissible blade stress, and calculates the active annular plane area and blade length to be adjusted based o the result of the comparisons.

Further, the blade length controller controls the blade length adjusting mechanism based on the calculated active annular plane area and blade length as follows.

When the detected wind speed is higher than the permissible wind speed, the active annular plane area is decreased by decreasing the blade length, and when the detected wind speed is lower than the permissible wind speed, the active annular plane area is increased by increasing the blade length. When the detected rotation speed is higher than the permissible rotation speed, the active annular plane area is decreased by decreasing the blade length, and when the detected rotation speed is lower than the permissible rotation speed, the active annular plane area is increased by increasing the blade length. When the detected load is higher than the permissible load, the active annular plane area is decreased by decreasing the blade length, and when the detected load is lower than the permissible load, the active annular plane area is increased by increasing the blade length. Further, when the detected blade stress is higher than the permissible blade stress, the active annular plane area is decreased by decreasing the blade length, and when the detected blade stress is lower than the permissible blade stress, the active annular plane area is increased by increasing the blade length.

By controlling the blade length through the blade length controller mentioned above, the lengths of the blades are adjusted so that the active annular plane area is optimal corresponding to the operating conditions such as wind speed, rotation speed and load of the wind turbine, and the output of the wind turbine can be always maintained at a maximum output level.

Further, according to the sixth and seventh means, as an active annular plane area can be controlled so that it is optimal for both the operating conditions such as wind speed, rotation speed and load of the wind turbine and for blade stress, the occurrence of excess blade stress of the rotating component due to sudden increase in wind speed or load is suppressed, and the occurrence of fatigue failure of said rotating components can be prevented.

Therefore, according to the sixth and seventh means, the wind turbine can be operated while always automatically controlling blade length so that the occurrence of fatigue failure of the rotating components such as the blades and rotor, and at the same time the wind turbine is operated with the optimal active annular plane area which insures a maximum of the wind turbine output while avoiding the fatigue failure. Accordingly, the operation of the wind turbine is possible with an optimal maximum output with elongated fatigue life of the rotating elements such as the blades and rotor.

The eighth means of the present invention is a wind turbine with an active annular plane area control mechanism comprising a plurality of blades attached to a rotor head for transmitting the wind force acting on the blades to the output shaft of the wind turbine connected to the rotor head, wherein each blade is attached to an end side of a connecting elbow of a certain bent angle, the other end side is attached to the periphery of the rotor head for rotation, a connecting elbow driving device is provided for rotating each of said connecting elbows, and the blades can be tilted in the direction of the axis of the rotor head to adjust active annular plane area.

It is preferable that there are provided a wind speed detector for detecting the speed of the wind acting on the blades, and a controller which calculates average wind speed during a certain period of time from the wind speed detected continuously by said wind speed detector and the tilt angle of the blades optimal for the average wind speed and controls said connecting elbow driving device so that the blades are tilted to the calculated angle.

As the operating method of the wind turbine with an active annular plane area control mechanism comprising a plurality of blades attached to a rotor head for transmitting the wind force acting on the blades to the output shaft of the wind turbine connected to the rotor head, it is preferable that the speed of the wind acting on the blades is detected, average wind speed during a certain period of time is calculated from the wind speed detected continuously by said wind speed detector, the active annular plane area optimal for the average wind speed is calculated, and the rotation angle of said connecting elbows is adjusted so that active annular plane area becomes equal to said calculated value through composing such that each blade is attached to each of a plurality of connecting elbows attached to the rotor head for rotation so that the blade is capable of being tilted in the direction of the axis of rotation of the rotor head by rotating said connecting elbow.

In the eighth means, it is preferable that said connecting elbow driving device comprises a ring gear fixed to said other end of the connecting elbow concentric with the axis of rotation thereof, a pinion meshing with the ring gear, a reversible motor for rotating the pinion, and a motor control device for controlling the rotation of the motor according to the output signal from said controller.

According to the eighth means, the speed of the wind acting on the blades is detected by the wind speed detector and inputted to the controller, and the controller calculates the average wind speed during a certain time period from the wind speed detected continuously by said wind speed detector and also calculates an active annular plane area the optimal wind turbine output for the average wind velocity from the predetermined relation between average wind speed and wind turbine output, and determines the active annular plane area based on said output.

The wind turbine is provided with the blade tilting mechanism which comprises connecting elbows to each of which is attached the blade and each of which is attached rotatably to the periphery part of the rotor head such that each blade is tilted by the rotation of each connecting elbow to change the tilt angle of the blade in order to change active annular plane area, and said controller calculates the rotation angle to realize said calculated active annular plane area and output it to the connecting elbow driving device of said blade tilting mechanism.

The connecting elbow driving device rotates the connecting elbow to change the tilt angle of the blade so that the tilt angle is equal to said calculated angle and keeps the blade at the position.

Thus, according to the eighth means, said controller allows said connecting elbow to be rotated to the position with which the blades are at right angle to the axis of rotation of the rotor head, accordingly active annular plane area is at maximum when average wind speed is lower than the predetermined lower limit value so that a maximum power is taken-in from wind. In this case, as wind speed is low, fatigue failure of the rotating components such as the blades and rotor does not occur by increasing the active annular plane area to the maximum.

When average wind speed is higher than the predetermined higher limit value, the connecting elbow is rotated to the position where the blades are tilted toward the axis of rotation of the rotor to decrease the active annular plane area in order to avoid occurrence of fatigue failure of the rotating components.

When average wind speed is between said lower limit and higher limit, the output of the wind turbine is determined according to the average wind speed and the blades are tilted to a position with which said determined power is obtained, and the wind turbine is operated with an optimal output taking into consideration fatigue failure of the rotating components.

By this, the wind turbine can be operated with the tilt angle of the blades adjusted and fixed at the position so that the output is a maximum while avoiding the occurrence of fatigue failure of the rotating components such as the blades and rotor.

Further, by changing the distance from the axis of rotation of the connecting elbow to the end face thereof for attaching the blade, the tip diameter of the blade can be changed. Therefore, the active annular plane area can be changed by preparing several connecting elbows different in said distance and only changing the connecting elbow without preparing blades of different blade length.

Further, according to the eighth means, the connecting elbow driving device can be composed so that the connecting elbows are controlled to be rotated to the rotational position determined by the controller by rotating them by the driving motor via the motor control device. Therefore, a simple and low-cost connecting elbow driving device can be obtained without using hydraulic devices operated by oil hydraulic pressure or air pressure.

Further, according to the eighth means, the adjustment of active annular plane area is possible by providing the blade tilting mechanism composed of said connecting elbow driving device and connecting elbow independently for each blade for adjusting the active annular plane area by changing the tilt angle of each blade by rotating the connecting elbow through the connecting elbow driving mechanism, and it is possible to adjust the tilt angle of each blade to an optimal position taking into consideration the output power of the wind turbine and fatigue limit of the rotating components.

As has been described above, according to the eighth means, the problem that may occur with conventional wind turbines having no adjusting means for adjusting the active annular plane area, i.e., the occurrence of fatigue failure of the rotating components such as the blade and rotor due to excessive high speed wind sometimes experienced by a gust of wind is prevented, and the wind turbine can be operated with a maximum output while avoiding the occurrence of fatigue failure of the rotating components such as the blades and rotor by adjusting active annular plane area by changing the tilt angle of the blades through changing the rotation angle of each connecting elbow according to the speed of the wind acting on the blades.

Therefore, according to the eighth means, the wind turbine can be operated while always automatically controlling blade length so that the occurrence of fatigue failure of the rotating components such as the blades and rotor and at the same time with the optimal active annular plane area which insures a maximum of the wind turbine output within the range capable of evading the fatigue failure. Accordingly, the operation of wind turbine is possible with an optimal maximum output with elongated fatigue life of the rotating elements such as the blades and rotor.

The ninth means of the present invention is a wind turbine with an active annular plane area control mechanism comprising a plurality of blades attached to a rotor head for transmitting the wind force acting on the blades to the output shaft of the wind turbine connected to the rotor head, wherein a blade tilting mechanism is provided for tilting the blades in the direction of the axis of rotation of the rotor head to change the active annular plane angle.

It is preferable that there are provided a wind speed detector for detecting the speed of the wind acting on the blades, and a controller which calculates average wind speed during a certain period of time from the wind speed detected continuously by said wind speed detector and the tilt angle of the blades optimal for the average wind speed and controls said blade tilting mechanism so that the blades are tilted to the calculated angle.

It is also preferable that said blade tilting mechanism comprises a fluid pressure actuator which is fixed to the rotor head so that the output shaft thereof moves in the direction of the axis of rotation of the rotor head, and a plurality of blade link each of which is supported via the supporting shaft fixed to the rotor head for swinging, an end part of each link being connected to the output shaft of said fluid pressure actuator and the other end being connected to each blade, and the tilt angle of the blades can be changed by swinging said blade link around said supporting shaft through the reciprocation of the output shaft of said fluid pressure actuator.

Further, it is preferable that said blade tilting mechanism comprises a servomotor fixed to the rotor head and having an output shaft having a male screw thread part, and a plurality of blade links each of which is supported via the supporting shaft fixed to the rotor head for swinging, an end part of each link being connected to a blade link guide engaged with the male screw thread of the output shaft of said servomotor, the other end being connected to each blade, and the tilt angle of the blades can be changed by swinging said blade link around said supporting shaft through the rotation of the output shaft of said servomotor.

Yet further, it is preferable that said blade tilting mechanism comprises a plurality of blade links each of which is supported via the supporting shaft fixed to the rotor head for swinging, and fluid pressure actuators each bridging between the protrusion extending from the center of the end of the rotor head and each blade link for changing the blade tilt angle in the direction of the axis of rotation of the rotor head by the extension and contraction of said actuator.

The tenth means of the present invention is an operating method of the wind turbine with an active annular plane area control mechanism comprising a plurality of blades attached to a rotor head for transmitting the wind force acting on the blades to the output shaft of the wind turbine connected to the rotor head, wherein the speed of the wind acting on the blades is detected, average wind speed during a certain period of time is calculated from the wind speed detected continuously by said wind speed detector, the active annular plane area optimal for the average wind speed is calculated, and the rotation angle of said connecting elbow is adjusted so that active annular plane area becomes equal to said calculated value through composing such that each blade is capable of being tilted in the direction of the axis of rotation of the rotor head.

According to the ninth and tenth means, the speed of the wind acting on the blades is detected by the wind speed detector and inputted to the controller, and the controller calculates the average wind speed during a certain time period from the wind speed detected continuously by said wind speed detector and also calculates the active annular plane area the optimal wind turbine output for the average wind velocity from the predetermined relation between average wind speed and wind turbine output, and determines the active annular plane area based on said output.

The wind turbine is provided with the blade tilting mechanism for changing the active annular plane area by tilting the blades toward the axis of rotation of the rotor head, and said controller calculates the tilt angle of the blades to realize said calculated active annular plane area and output it to the actuator of said blade tilting mechanism.

The blade tilting mechanism tilts the blades so that said calculated active annular plane area is realized by the tilting and keeps the blade at the position.

Thus, said controller allows the blades to be at right angle to the axis of rotation of the rotor head, accordingly active annular plane area is at maximum when average wind speed is lower than the predetermined lower limit value so that a maximum power is taken-in from wind. In this case, as wind speed is low, fatigue failure of the rotating components such as the blades and rotor does not occur by increasing the active annular plane area to the maximum.

When average wind speed is higher than the predetermined higher limit value, the blades are tilted toward the axis of rotation of the rotor to decrease active annular plane area in order to evade the occurrence of fatigue failure of the rotating components.

When average wind speed is between said lower limit and higher limit, the output of the wind turbine is determined according to the average wind speed and the