Hybrid horizontal axis wind turbine

Abstract

Hybrid horizontal axis wind turbine provides supplementary additional gravitational torque and pneumatic torque when the wind speed happens to be less than the speed required for optimum power generation. Every blade 11 of the turbine comprises pneumatic system 51 consisting of a rod less pneumatic cylinder 21. Supplementary torque generated by the pneumatic system 51 reduces the cut-in wind speed at which the wind turbine power generation is started and accelerates turbine rotations for the optimum output power generation. Thus widens the total duration of output power generation that is uptime and stretches the duration of optimum power generation that is pick output time. The wind turbine has considerable higher overall efficiency of the wind turbine. Said wind turbines could be installed in the regions, where there is lower wind speed for a considerable duration. Reference: Fig.1

Description

Description Title of Invention: Hybrid horizontal axis wind turbineTechnical Field:The present invention relates to renewable energy; an efficient horizontal axis wind turbine. Overall operational efficiency of most common present day three blades horizontal axis wind turbines depends on its uptime and duration of optimum power generation; that is duration time of optimum power generation during favourable range of wind speed, drop in power generation during lower wind speed and period for which power generation is stopped. Wherein the power generation is started only after speed of wind goes above cut-in speed and power generation is stopped when speed of wind exceeds cut-out speed. The present invention wind turbine provides supplementary additional gravitational torque and pneumatic thrust torque when it is needed. By virtue of this additional torque the wind turbine starts power generation at lower speed of wind and further accelerates the turbine rotations up to reaching the optimum level for highest power generation. Thus within the total available time, hybrid horizontal axis wind turbine generates output power for longer duration and there is considerable longer duration of optimum power generation, so it provides considerably higher overall operational efficiency. Therefore these wind turbines could be installed in the regions, where there is lower wind speed for a considerable duration.Background Art:The present day widely spread three blades horizontal axis wind turbine starts to generate electrical power after certain cut-in wind speed is reached. Said power generation is lower during low speed of wind because of lower rotational torque. When there is increasing wind speed, accordingly the power generation increases with the increase in the wind turbine rotations per minute and reaches to its designed optimum level at optimum wind speed. Through the internal adjustments of wind turbine like blade pitch angle adjustments, this optimum level power generation is maintained for a certain range of safe wind speed. When the wind speed exceeds “safe working limits”, wind turbines are stopped at this cut-out speed. However very high wind speeds don’t happen that often in a year. While capturing kinetic energy form the wind energy, wind turbine is rotated by the torque generated on blades by the total lift force on airfoils. As known, even at its best due to operational limitations the efficiency of these wind turbines cannot exceed beyond “Betz limit”; 59.3 percent. Therefore the problem is that, as aforesaid overall operational efficiency of most common present day three blades horizontal axis wind turbines is less because of:a) Operational time loss of no power generation, during when the speed of wind is less than cut-in speed and when the speed of wind is greater than cut-out speed, which is the loss happening in the available time.b) Low power generation, during when the wind speed happens to be below optimum level, which is underutilization of installed capacity.c) Optimum output power is generated during only when the wind speed happens to be within favorable range.The present invention solution object: to provide supplementary torque when the kinetic energy of wind is insufficient to produce the torque required to generate output power; which could reduce the cut-in wind speed, at which the wind turbine power generation is started and could accelerate turbine rotations for the optimum output power generation. Thus to widen the total duration of output power generation and to stretch the duration of optimum power generation; which should result into considerable increase in the overall efficiency of the said wind turbine with minimal consumption of additional input energy.Summary of Invention:Intent to provide solution to cited problem the modified hybrid horizontal axiswind turbine comprises independently mounted pneumatic rod less cylinders housed into the hollow space inside each turbine blade and a pneumatic system exhausting compressed air through radial ports on the trailing edges of turbine blades. Each blade has an individual electro-pneumatic system to control its pneumatic cylinder operation and compressed air outflow through the exhaust port.For the easy understanding of the present embodiment system operation it is described with reference to drawings. Hereafter turbine vertical axis top position is considered as 0 and other angular positions are being referred against it.When turbine blade 11 is moving down gravitational torque is in the direction of turbine rotation and when turbine blade 11 is moving up it is in the direction opposite to turbine rotation. As known during circular motion, gravitational torque generated by the radial mass is proportionate to its angular position; torque is zero when mass is at vertical axis and it goes on increasing during angular displacement of the mass towards horizontal axis and it is highest when mass is at horizontal axis; torque is highest when mass is at horizontal axis and it goes on decreasing during angular displacement of the mass towards vertical axis and it is zero when mass is at vertical axis.Pistons 25 of pneumatic cylinders 21 of present embodiment turbine act as a mass which generates additional gravitational torque during turbine rotation. During downward rotation, pneumatic cylinder's piston 25 of every blade 11 is radially placed at end position toward blade tip side cover 41 that is away from hub 18. During upward rotation, piston 25 of every blade 11 is radially placed at end position toward hub side cover 46 that is near centre hub 18. Therefore as the torque generated by the rotating mass is proportionate to its radial distance, when present embodiment turbine blades are rotating down, additional torque generated is higher than the torque produced when they are rotating upward. That is the present embodiment has net positive additional gravitational torque generated in the direction of turbine rotation. During turbine rotation, when every blade 11 is passing through vertical axis top side having minimum gravitational torque component, at that time the piston 25 in the pneumatic cylinder 21 is moved upward by the regulated inflow of compressed air in to the hub side cylinder chamber 31. Compressed air in the blade tip side cylinder chamber 39 is vented out through exhaust port 22. Said exhaust out flow is controlled by the proportionate solenoid valve 44.When every blade 11 is passing through vertical axis bottom side having minimum gravitational torque component, at that time the piston 25 in the pneumatic cylinder 21 is moved upward by the regulated inflow of compressed air in to the blade tip side cylinder chamber 39. Compressed air in the hub side cylinder chamber 31 is vented out through exhaust port 22. Said exhaust out flow is controlled by the proportionate solenoid valve 45. Some operational time that is some amount of angular displacement is needed for pneumatic operations.The present embodiment prefers angular displacement of 40 degrees bisected by vertical axis during which said piston displacements are carried, during which there is minimum component of gravitational torque. That is when every blade 11 passes through from 340 degree to 20 degree, its piston 25 is moved up toward blade tip side cover 41 and when every blade passes through from 160 degree to 200 degree its piston 25 is moved up toward hub side cover 46.When the compressed air is vented out from either of pneumatic cylinder 21 chambers, it passes out tangentially through the exhaust port 22 on the trailing edge of the blade 11 produces thrust force on the blades that is pneumatic torque. As described above during every rotational cycle each blade 11 generates said pneumatic torque twice; while passing through an angle of 40 degrees at top side and while passing through an angle of 40 degrees at bottom side. Therefore total combined angular distance covered by three blades is 240 degrees, when there is pneumatic torque is generation, mince there is gap of 120 degrees having no pneumatic torque, this will lead to vibrations on the turbine structure.Therefore to solve said problem and avoid vibrations, the present embodiment pneumatic system passes out fresh compressed air trough exhaust ports 22 during angular displacement of 10 degrees each preceding and succeeding every pneumatic cylinder activity. That is every time when the each blade 11 passes through vertical axis [twice], compressed air is passed out through exhaust port 22 during circular displacement of an angle of 60 degrees. By virtue of angular spacing of blades, each time when the compressed air discharge from the blade 11 is stopped, at the same time compressed air discharge gets started from the preceding blade 11. Thus the compressed air discharge through blades covers all 360 degreedisplacement of the turbine and there is continuous generation of pneumatic torque. Said fresh air is discharged bypassing pneumatic cylinders with flow rate same as of outflow from the pneumatic cylinders. The radial distance of exhaust port 22 is so as, the arc length for the displacement angle of 40 degrees at this radius is same as linear displacement length of piston 25. Said angle of 40 degrees is the preferred angle for pneumatic cylinders operations.The compressed air inflow to the system is regulated according to the instantaneous speed of wind turbine and the optimum wind turbine speed. To avoid vibrations, outflow from pneumatic cylinders is regulated by the proportionate solenoid valve.When the wind speed reaches near favourable speed range, compressed air inflow to the pneumatic system is reduced according to the wind speed at that time, so as the upward piston 25 displacements are shortened. When the wind speed reaches the favourable range the operation of said pneumatic system is stopped, pistons 25 in pneumatic cylinders 21 are locked at their end positions toward hub side cover 46 by using any of suitable locking means like pneumatic wedges or electromagnetic locking. Then the present operational procedures of turbine controlling are continued.Novel feature of the present embodiment is that; the potential energy in the form of compressed air is utilized to move up pistons 25 of pneumatic cylinders 21, pistons 25 by virtue of its radial position generates gravitational torque and again potential energy conserved in the pneumatic cylinders 21 is explicitly reutilized to generate pneumatic torque; when compressed air is discharged through exhaust ports 22 it generates torque. Thus the present embodiment provides additional supplementary torque to the wind turbine with minimal consumption of input energy.Thus present embodiment wind turbine provides additional supplementary torque when the kinetic energy of wind is insufficient to generate the torque required to generate output power; reduces the cut-in wind speed at which the wind turbine power generation is started and accelerates turbine rotations for the optimum output power generation. Thus widens the total duration of output power generation that is uptime and stretches the duration of optimum power generation that is pick output time; results into considerably higher overall efficiency of the wind turbine with minimal consumption of additional input energy.Brief Description of Drawings:Fig.1 is schematic drawing of the present embodiment wind turbine,illustrating partial cut sections of all three blades 11.Fig.2 is schematic front view diagram illustrates cams and proximity sensorsinside the hub 18. Destination positions of blade mounting flanges 26 andproximity sensors 19 after angular displacement of 60 degree are shown withdashed line style. Out of four only one proximity sensor 19 appears in saidfront view. In order to provide clearer vision of four proximity sensors on oneof the blades and four cams on cam ring 33, the side view is included in thisfigure. Said side view perceptively displays four proximity sensors on blade atthe 0 position and four cams on cam ring 33.Fig.3 illustrates the incorporated preferred pneumatic system circuit. Everyblade 11 of the wind turbine essentially consists of parts encompassed by therectangle 51; that is the part of pneumatic system after adjustable flow controlvalve 52.Fig.4 is the graph that illustrates the radial distance of added mass that isradial distance of the piston 25. Angles shown are in degrees.Fig.5 is the graph of estimated additional gravitational torque generated bythe additional mass on individual blades. Fig. 6 is the graph of estimated combined additional gravitational torque generated by the additional mass on blades.Fig.7 is the graph of estimated total additional torque generated; sum of gravitational torque and combined pneumatic torque generated by the said pneumatic system.In above figures: 11, Blade [3 nos.]; 12, Upper 60o cam; 14, Nacelle; 15, lower 60o cam; 16, Upper 40o cam; 17, lower 40o cam; 18, Hub; 13, 19, 43 and 47, Proximity sensors; 21, Pneumatic cylinder; 22, Exhaust port; 23, Compressed air reservoir; 24, Dehumidifier; 25, Piston; 26, Blade mounting flange; 27, FRL; 28, 32, 37 and 38 , Solenoid valves; 29, Tower; 31, Hub side cylinder chamber; 33, Cam ring; 35, 36 and 52, adjustable flow control valves; 39, Blade tip side cylinder chamber; 41, Blade tip side cylinder cover; 42 and 48, Spring loaded NRV; 44 and 45, Proportionate solenoid valves; 46, hub side cylinder cover.Description of Embodiments:A preferred embodiment of the present invention will be described below withreference to drawings. To avoid complexness and clumsiness of thedrawings, all parts are not shown in the drawings. The drawings are notnecessarily to scale and in some instances, proportions may have beenexaggerated.The present embodiment provides supplementary additional gravitationaltorque and pneumatic torque, so the content of the generator comingthereafter is beyond the scope of this description.The present embodiment air compressor [not shown in drawing], reservoir23, dehumidifier 24 and FRL unit 27 are installed at on the foundation of thewind turbine base. Through the pipe line fastened into the tower 29 saidcompressor through its peripherals supplies the compressed air to thepneumatic system incorporated in the present embodiment. Said pipecommunicates with every blades individual pneumatic system through rotaryswivel joint at the hub 18 centre. Electrical power is supplied through the slipring. As illustrated in the fig.1, every blade 11 of present embodiment comprises pneumatic cylinder 21, which has only piston 25 without piston rod. The length of said cylinder 21 is less than the length of that blade section, which could have minimum deflection at the instance of high wind gust. Pneumatic cylinders 21 are independently fixed on the mounting flanges 26 and leave sufficient hollow space inside the blade 11. Said cylinders 21 do not cause any constraint to the blade 11 for its any kind of movement. Pneumatic parts and pipes are suitably fitted inside hollow space. Every blade 11 has exhaust port 22 on its trailing edge. The radial distance of said exhaust port 22 is so that the arc length for the displacement angle of 40 degrees at this radius is same as linear displacement length of piston 25. Said angle of 40 degrees is the preferred angle for pneumatic cylinders operations. All outflow lines of the pneumatic system are connected to the said exhaust port 22 through a manifold. Said manifold is connected exhaust port 22 by a flexible hose. Cross section of said exhaust port 22 is rectangular, directing the out flown air in the plane nearly parallel to turbine rotation plane so as to produce optimum torque, when the pitch has been adjusted for low wind speed. Pistons 25 of pneumatic cylinders 21 of present embodiment turbine act as a mass, which generates additional gravitational torque during turbine rotation. The amount of mass of the piston 25 and its linear displacement length is proportionate to other parameters of the said wind turbine.As illustrated in fig.3, every blade has its individual electro-pneumatic circuit 51 to control the movements of its piston 25 and discharge of compressed air through it. Said electro pneumatic circuit is the preferred but not limited, several alternate electro-pneumatic circuits are possible for the intent of the present embodiment. The solenoid valves contained in the circuit 51 are set on or off by the signals obtained by the proximity sensors of that blade 11. As illustrated in the fig.2, every blade 11 has set of four proximity sensors. There are four arc cams mounted on the stationary ring 33 fitted on cover of main bearing of centre shaft. The turbine shaft freely passes through the said cam ring 33. There are two cams each on upper half and lower half; a sixty degree cam and a forty degree cam. Hereafter the sequential process of the preferred embodiment pneumatic system is described.The compressed air [fluid] first passes through the adjustable flow control valve 52 and then supplied to every blade’s pneumatic system 51 through rotary swivel joint at hub 18.When a rotating wind turbine blade 11 reaches to 330 degree position, the proximity sensor 13 senses upper 60 degree cam 12 and communicates to pneumatic system. This actuates solenoid valve 28 and starts fresh compressed air flow, which passes through normally open solenoid valve 37 and further passes through adjustable flow control valve 35 and outflows through exhaust port 22. Said event starts to generate pneumatic torque by the thrust of compressed air exhaust.When the said blade 11 rotates further to 340 degree position, the proximity sensor 19 senses upper 40 degree cam 16 and communicates to pneumatic system and solenoid valve 37 and proportionate solenoid valve 44 are actuated, this shifts the fluid inflow into the hub side cylinder chamber 31. This fluid inflow displaces the piston 25 up toward blade tip side cover 41 and fluid in blade tip side cylinder chamber 39 is flown out through proportionate solenoid valve 44 and then the exhaust port 22 exhausts it out. This compressed air exhaust generates pneumatic torque. The displacement speed of piston 25 is controlled by the proportionate solenoid valve 44, which is meter-out control. Said speed is so as the piston 25 is moved up to end position toward blade tip side cover 41 at that time when the blade 11 reaches to 20 degree position. When said blade 11 rotates to 20 degree position proximity sensor 19 stops sensing upper 40 degree cam 16 and solenoid valve 37 and proportionate solenoid valve 44 are deactivated, pneumatic cylinder’s 21 both ports are closed and fluid flow through solenoid valve 28 is redirected to exhaust port 22 and continues the fluid exhaust. A pressure transducer [not shown in figure] is connected to exhaust pipe leading to the exhaust port 22, communicates to pneumatic system and accordingly adjustable flow control valve 35 is adjusted to have fresh compressed air flow nearly same as out flow from pneumatic cylinder 21. Thus as illustrated in the fig.4, when a turbine blade 11 moves from 340 degree to 20 degree, the piston 25 is displaced from its end position at hub side cover 46 to its end position at blade tip side cover 41; at that time the piston 25 is radially positioned away from centre hub 18.When said blade 11 rotates further to 30 degree position proximity sensor 13 stops sensing upper 60 degree cam 12 and solenoid valve 28 is deactivated and pushed back to its normally closed position. This stops fluid flow through it and this stops the compressed air exhaust through said blade's pneumatic system 51.This stops generation of pneumatic torque.Thus the pneumatic torque is generated when said blade 11 rotates from 330 position degree to 30 degree position.As illustrated in the fig.2; when a turbine blade 11 is 30 degree the blade preceding has been at 150 degree. When the said blade 11 is at 150 degree rotational position, proximity sensor 43 senses lower 60 degree cam 15 and communicates to pneumatic system and solenoid valve 32 is actuated; this starts fresh compressed air flow through it which passes through normally open solenoid valve 38 and further passes through adjustable flow control valve 36 and then out flown through exhaust port 22, and starts to generate pneumatic torque by the thrust of compressed air exhaust.When the said blade 11 rotates further to 160 degree position, the proximity sensor 47 senses lower 40 degree cam 17 and communicates to pneumatic system and solenoid valve 38 and proportionate solenoid valve 45 are actuated, this shifts the fluid inflow into the blade tip side cylinder chamber 39 and said fluid displaces the piston 25 up toward hub side cover 46 and fluid in hub side cylinder chamber 31 is flown out through proportionate solenoid valve 45 and then the exhaust port 22 exhausts it out. Said compressed air exhaust generates pneumatic torque. The displacement speed of piston 25 is controlled by the proportionate solenoid valve 45, which is meter-out control. Said speed is so as the piston 25 is moved up to end position at hub side cover 46, at the time when the blade 11 reaches to 200 degree position. When said blade 11 rotates to 200 degree position proximity sensor 47 stops sensing lower 40 degree cam 17 and solenoid valve 38 and proportionate solenoid valve 45 are deactivated, pneumatic cylinder’s 21 both ports are closed and fluid flow through solenoid valve 32 is redirected towards exhaust port 22 and the outflow through it is continued. A pressure transducer [not shown in figure] is connected to exhaust pipe leading to the exhaust port 22, communicates to pneumatic system and accordingly adjustable flow control valve 36 is adjusted to have fresh compressed air flow nearly same as the out flow from pneumatic cylinder 21.Thus as illustrated in the fig.4, when a turbine blade 11 moves from 160 degree to 200 degree, the piston 25 is displaced from its end position at blade tip side cover 41 to its end position at hub side cover 46 position; at that time the piston 25 is radially positioned near centre hub 18. When said blade 11 rotates further to 210 degree position proximity sensor 43 stops sensing lower 60 degree cam 15 and solenoid valve 32 is deactivated and pushed back to its normally closed position. This stops fluid flow through it and this stops the compressed air exhaust through said blade's pneumatic system 51.This stops generation of pneumatic torque. Thus said pneumatic torque is generated when said blade 11 rotates from 150 position degree to 210 degree position.As illustrated in the fig.2; likewise when a turbine blade 11 is 210 degree the blade preceding has been at 330 degree, so its pneumatic system gets activated and starts generation of pneumatic torque, which stops when it rotates to 30 degree position. During its angular displacement from 340 degree to 20 degree its piston is moved up from its end position at hub side cover 46 to its end position at blade tip side cover 41, which is radially positioned away from centre hub 18.This sequential cycle is continuous; therefore the compressed air discharge through blades covers all 360 degree displacement of the turbine and there is continuous generation of the pneumatic torque; and when every blade 11 passes through from 340 degree to 20 degree, its piston 25 is moved up toward blade tip side cover 41 and when every blade passes through from 160 degree to 200 degree its piston 25 is moved up toward hub side cover 46. Therefore since the torque produced by the rotating mass is proportionate toits radial distance, when present embodiment turbine blades are rotatingdown, additional torque generated is higher than the torque generated whileit is moving upward.As illustrated in the fig.5 graph, during a turbine rotation cycle every blade 11generates an additional gravitational torque. Said positive torque componentin the direction of rotation is much higher than the negative torquecomponent in the direction opposite to rotation.That is the present embodiment has net positive additional gravitationaltorque generated in the direction of turbine rotation.Fig. 6 graph curve illustrates the combined additional gravitational torquegenerated by the additional mass on blades.Fig.7 graph curve illustrates the total additional torque generated; sum ofgravitational torque and combined pneumatic torque generated by the saidpneumatic system.As aforesaid the present embodiment pneumatic system is used when thewind speed happens to be lower than the optimum speed required foroptimum power generation.When the wind speed reaches near favourable speed range, compressed airinflow to the pneumatic system is reduced according to the wind speed atthat time, so as the upward displacements of piston 25 are shortened. Whenthe wind speed reaches the favourable range the operation of said pneumaticsystem is stopped, pistons 25 in pneumatic cylinders 21 are locked at endpositions toward hub side cover 46 by using any of suitable locking meanslike pneumatic wedges or electromagnetic locking. Then the existingoperational procedures of turbine controlling are continued.Thus present embodiment wind turbine provides additional supplementarytorque when the kinetic energy of wind is insufficient to produce the torquerequired to generate output power; reduces the cut-in wind speed at whichthe wind turbine power generation is started and accelerates turbinerotations for the optimum output power generation. Thus widens the totalduration of output power generation that is uptime and stretches the duration of optimum power generation that is pick output time; results into considerably higher overall efficiency of the wind turbine with minimal consumption of additional input energy.

Claims

AMENDED CLAIMS1. The present invention wind turbine is characterized in that; every blade 11of turbine comprises a pneumatic system 51 consisting of pneumaticcylinder 21 which has only piston 25 without piston rod and exhaust port 22on its trailing edge;wherein said pneumatic system 51 provides additional supplementary torque combined of gravitational torque and pneumatic torque when the kinetic energy of wind is insufficient to produce the torque required to generate output power; said supplementary torque reduces the cut-in wind speed, at which the wind turbine power generation is started and accelerates turbine rotations for the optimum output power generation; hence said wind turbine has lower cut-in wind speed at which power generation is started and longer duration of optimum power generation.

2. The wind turbine as claimed in the claim 1 wherein:The piston 25 of the pneumatic cylinder 21 of every blade 11 acts as a mass, which provides additional gravitational torque during turbine rotation; during turbine rotation, when every blade 11 passes through vertical axis top side having minimum gravitational torque component, at that time the piston 25 in the pneumatic cylinder 21 is radially displaced away from the turbine centre and when every blade 11 passes through vertical axis bottom side having minimum gravitational torque component, at that time piston 25 in the pneumatic cylinder 21 is radially displaced toward turbine centre; during the said displacement of the piston 25, the compressed air discharged from the pneumatic cylinder 21 is expelled out through the exhaust port 22 on the trailing edge of blade 11, which produces the pneumatic thrust torque;during downward rotation of the turbine when the gravitational torque is in the direction of turbine rotation, the piston 25 of every blade 11 is radially at its end position away from turbine centre and during upward rotation when the gravitational torque direction is opposite to turbine rotation, pneumatic cylinder's piston 25 of every blade 11 is radially at its end position near to tower centre;as known the torque produced by the rotating mass is proportionate to its radial distance, when the present invention turbine blades are rotating down additional torque generated is higher than the torque generated when they are rotating upward, hence the said turbine has net positive additional gravitational torque produced in the direction of its rotation.

3. The wind turbine as claimed in the claim 1 wherein:During turbine rotation, every blade 11 passes through vertical axis twice in a rotation cycle, once on top side and once on bottom side; when every blade 11 passes through an angle of 60 degrees bisecting vertical axis, pneumatic system 51 expels out the compressed air through the exhaust port 22 on the trailing edge of said blade 11 produces thrust force on the blades that is pneumatic torque;by virtue of angular spacing of blades, when the proximity sensor on a blade 11 stops sensing 60 degree cam at the same time the proximity sensor on preceding blade 11 starts to sense other 60 degree cam; each time when the compressed air discharge from the blade 11 is stopped, at the same time compressed air discharge gets started from the preceding blade 11; Thus the compressed air discharge through blades covers all 360 degree displacement of the turbine and there is continuous pneumatic torque;4. The wind turbine as claimed in the claim 1 wherein:the radial distance of said exhaust port 22 is so that the arch length for the displacement angle of 40 degrees at this radius is same as piston 25 displacement length, said angle of 40 degrees is the preferred angle for pneumatic cylinders operations; to generate optimum torque, cross section of said exhaust port 22 is rectangular with the baffle directing the expelling fluid in the plane nearly parallel to turbine rotation plane, when the pitch has been adjusted for low speed of wind;5. The wind turbine as claimed in the claim 1 wherein:During compressed air discharge from the exhaust port, the outflow from the pneumatic cylinder’s chambers and speed of piston 25 displacements is controlled by the proportionate solenoid valves; during fresh compressed airdischarge, adjustable flow control valves are adjusted to have nearly same out flow as of from pneumatic cylinder 21.

6. The wind turbine as claimed in the claim 1 wherein:The potential energy in the form of compressed air is utilized to move up pistons 25 of pneumatic cylinders 21, potential energy by virtue of position of pistons 25 is utilized to produce gravitational torque and again potential energy conserved in the pneumatic cylinders 21 is explicitly reutilized to generate pneumatic torque; When fresh energy is discharged through exhaust ports 22 it generates torque; thus the present embodiment provides additional supplementary torque to the wind turbine with minimal consumption of input energy.

7. The wind turbine as claimed in the claim 1 wherein:When the wind speed reaches near favourable speed range, compressed air inflow to the pneumatic system is reduced according to the wind speed at that time, so as the upward piston 25 displacements are shortened; when the wind speed reaches the favourable range the operation of said pneumatic system is stopped, pistons 25 in pneumatic cylinders 21 are locked at end positions toward hub side cover 46; This stops the generation of additional torque.

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