PRIORITY CLAIM:

This application claims priority from India Non-Provisional Patent application number 202041052385, filed on 01 December 2020, entitled “APPARATUS AND METHOD FOR WIND TURBINES OPERATING IN HIGH WINDS AND HURRICANES”, naming as inventor Sunit Tyagi, and is incorporated it its entirety herewith, to the extent not inconsistent with the disclosure of the instant application.

TECHNICAL FIELD:

The present invention relates to an apparatus and system for generating power from wind under high wind conditions. The invention further relates to wind turbine that safely survives severe weather conditions such as tropical storms and hurricanes. The invention further relates to method of operation of the wind turbine to ensure survivability through extreme storms.

BACKGROUND OF THE INVENTION:

Anthropogenic emissions have increased the atmospheric concentration of Green House Gases (GHG) such as Carbon Dioxide, Methane, which have changed the energy balance of Earth; with net incoming energy estimated to now be in the range of 0.8 to 1 .2 W/m ² , leading to higher accumulation of heat. The increased accumulation of heat on Earth’s surface is predicted to inexorably change the climate, with average temperatures already increasing and the runaway process will cause cataclysmic changes that cannot be averted, such as stronger storms and more extreme weather.

A large body of research has gone in to address the global challenge of climate change; and much of it has focused on reducing the GHG emissions, so as to slow down the process, by encouraging renewable energy generation, higher efficiency devices as well clean carbon technologies. However, since concentrations of GHGs in Earth’s atmosphere have already increased due to past emissions, that have led to irrevocable changes in energy balance, to counter these baked-in emissions, research is ongoing on technologies to decarbonize, or reducing the GHG in atmosphere by capturing and sequestering carbon and other compounds. However, these technologies for clean generation, cleaning the air and efficient consumption are all expensive - increasing the cost of energy by 25% to 50%, making their adoption slow and difficult.

In this invention, we present technology for wide spread deployment of wind energy in areas that are prone to extreme weather such as storms with strong winds, including those areas frequented by hurricanes of highest categories. Our invention further extends deployment of wind generational technologies to areas prone to storms and hurricanes such as coastal and offshore ocean areas, where it is necessary to ensure longevity and minimizing cost. The goal is to deliver a renewable energy generation system that will not only counter the ill effects of climate change, but also survive the expected extreme events on account of it.

The atmospheric concentration of green house gases (GHG) such as CO2 has increased steadily over past century and is now over 50% higher than that of the pre- industrial age. Higher GHG concentration in the atmosphere gives higher downward infrared radiation from the green house gases that act like a blanket for the atmosphere and this gives higher energy imbalance, and accumulation of heat on Earth’s surface. With the higher GHG concentration, energy imbalance on planet surface has steadily increased and the current estimates range from 0.8 W/m ² to 1.2 W/m ² . The higher energy imbalance has led to increasing surface temperature of the Earth over the past century, where the increase in surface temperature is clearly observable in the recent decades, and has emerged from the background of decadal natural variations, and rising roughly 0.7 degrees Centigrade in last 50 years, for an average rise of 0.14 degrees/decade.

The higher average temperature across the globe is potentially causing stronger longer lasting storms with higher wind velocities and heavier rainfalls. These stronger storms and hurricanes pose special challenge to use of renewable energy sources such as windmills and solar power generation. This is because a hurricane with dense cloud cover and lasting for days can block sunlight and limit the generation from solar plants that are increasingly important source of electric generation. In addition due to the high wind speeds today’s design of windmills cannot operate beyond a cutoff wind speeds, the generation from windmills are typically limited for wind speeds below 20 to 45 meters/second. Windmills blades are airfoils designs with variable pitch to control the angle of attack with respect to incident wind. For very high wind speeds, the pitch is varied to cause stalling and reducing the lift force to limit any potential damage due to the heavy winds, and this loss of lifts leads to no motion of the blades, stopping generation. The weakest hurricanes (typhoons) of Category 1 usually have wind speeds that can exceed these critical speeds, thus even generation from windmills may not be possible during a hurricane. Thus both solar photovoltaic plants and windmills may have limited generation during hurricanes and heavy wind season, potentially limiting their usefulness in many areas across the globe.

Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, a generator, a gearbox, a nacelle, and a rotor having one or more rotor blades. The rotor blades transform wind energy into a mechanical rotational torque that drives one or more generators via the rotor. The generators are sometimes, rotationally coupled to the rotor through the gearbox. The gearbox steps up the inherently low rotational speed of the rotor for the generator to efficiently convert the rotational mechanical energy to electrical energy, which is fed into a utility grid via at least one electrical connection. Such configurations may also include power converters that are used to convert a frequency of generated electric power to a frequency substantially similar to a utility grid frequency.

Industry requirements for more efficient and economical windmills are pushing engineering towards higher towers with larger blade diameters, unfortunately these larger structures are much more prone to damages by high winds. Also, it is important to recognize that, most windmills depend on a self limiting design of airfoil, that depends on the boundary layer separating and the lift which moves the blades as the forces are reduced steeply due to stall at high wind speeds. Yet, there is a great risk of damage to large windmills due to turbulent and gusty high winds during hurricanes and this limits use of windmills in areas prone to hurricanes and typhoons, a concern which will increase further now due to higher likelihood of hurricanes with Category 3 and above (super-typhoons) which is caused by global warming.

We present in this invention a robust design for windmills that can survive extremely high winds expected even in a Category 5 hurricane, with system designed to reduce the risk of damage due to heavy turbulent winds. In addition, the windmills are engineered to operate in high wind conditions and can be also generating electrical energy during a hurricane. Such renewable energy designs are particularly important for areas affected by Hurricanes such as Andaman and Lakshadweep Islands, Eastern Coast of India and United States extending South to Florida and Gulf coast, Caribbean Islands, Eastern coast of Japan, Philippines, Taiwan, etc.

SUMMARY OF THE INVENTION

Increasing Green House Gases concentration in atmosphere due to anthropogenic emissions is leading to an additional energy accumulation of roughly 0.6 to 1 W/m ² , and today this is causing an increase in global temperatures by roughly 0.17 °C per decade. The common suggested approach to address this trend, and to avert worst-case cataclysmic impact, has been to reduce the emissions by not using fossil fuels and using renewable energy instead. There are several issues with this approach firstly the adoption of renewable energy is still slow and thus today it provides only a minor fraction of the total generation sources. The low adoption is mainly due to their high cost, also since the renewable sources are affected by incoming natural sources, the variability in generation is very high and less predictable, this impacts adoption and this concern is being addressed by using energy storage such as batteries but that adds to the expense. Secondly another concern with adopting only the strategy of reducing fossil fuel consumption is that the accumulated amount of GHG already emitted and in the atmosphere today, this will continue heating the planet and increasing the temperatures, so even stopping the emissions today will not reverse the trends underway. So with the currently adopted approaches the planet warming trends cannot be reversed. One very important impact of the GHG driven global warming and climate change is the increasing strengths of tropical storms, these are gathering higher amount of moisture and building in wind speeds. The impact of the warmer weather is going to be stronger storms and hurricanes that are going to be longer lasting with thicker cloud cover, heavier rains over wider expanse leading to flooding, and with very strong winds at a site for multiple days. If renewable energy sources are the predominant source of energy, as is required in order to reduce the fossil fuel consumption, it is imperative that these energy generation sources continue to operate despite the storms or hurricane impacting an area for days altogether.

Electricity generation from solar photovoltaic plants depend on the intensity and duration of incoming sunlight, and during stormy days and hurricane weather the irradiation drops significantly due to the clouds and rains. This lower amount of radiation, will greatly reduce the energy output, in addition, it is conceivable that plants have to shutdown due to safety concerns due to heavy winds and any flooding of the plant. In short, energy generation from solar plants can be very low due to the rainy and cloudy weather during tropical storms, gravely impacting grid stability.

Similarly, conventional windmill are designed to cut off motion of blades and electricity generation if the wind speeds are greater than some critical value, typically ranging from 25 to 40 m/s. This means that during strong tropical storms and hurricanes the energy generation from windmills will be significantly curtailed and even completely removed from the grid. This again leads to significant impact on the grid stability and ability to provide power to the community, especially areas such as islands supported fully by renewables. Such conditions are especially important for island communities that increasingly rely on renewable energy sources in forms of micro-grids with solar, wind and other sources. Many of these islands, unfortunately also suffer due to direct traversal of tropical storms and hurricanes underlining the above listed concerns.

The shortcomings of the prior art are overcome and additional advantages are provided by this invention that consists of three main constituent groups of apparatus and methods.

In one aspect a design for a system with apparatus, sensors and actuators are described herein, with a main airfoil blade along with a cross brace for each blade of the wind turbine, angling from the nacelle root point to join the main blade at a support point or vertex, this allows the system to not only survive but also operate in extremely high wind conditions. The invention with a cross brace strut from root to vertex adds rigidity to the structure and reduces the effective cantilever length for the main blade, by doing so, it reduces the stress and deflections thus improving the robustness of the design. The shorter cantilever length means less material and better reliability of the system. Considering the cantilever main blade as a simple beam, since the deflection of a beam varies as the cube power of the length, if the length of main blade is effectively reduced to 2/3 ^rd its original value its deflection reduces to 8/27 ^nd i.e. nearly down to 29% of the original value. If instead the effective length was halved ( ¹ ?) the deflection will reduce to 1/8 ^th i.e. only 16% of the value for the original length. The reduced deflections are very important to limit the likelihood of failure of the blade, and conversely reduce the material required to make the main blade, improving the weight and the cost of the blade. In one aspect, the inventions consists of apparatus for generating electricity from wind by using novel wind turbines that compared to prior art have extra structural elements and made with requisite strength to be able to reliably survive storms with greatest wind speeds. This design can be installed in areas that are prone to strong tropical storms and hurricanes, for example the islands of Caribbean, Andaman, or Philippines, and thereby considered not suitable for siting of conventional wind generation units.

In another aspect, the system design leverages the aerodynamic factors of wind and blade motion and changes the shape of the main blade and that of the cross bracing, so as to control the lift and drag along the length of the blade and under various dynamic conditions. These changes are done so as to maximize efficiency and robustness and allow operation over wider range of wind conditions. In normal operations, starting at the center or root of the blade and moving outwards towards the tips, the initial length or inner radius has wind interacting with both the blade and the angled cross bracing. This composite structure of blade and cross bracing essentially forms a staggered biplane configuration of airfoils with the main blade on the leading edge, which gives higher rigidity and strength for a given structure weight and better performance at lower effective wind speed. Beyond the vertex, i.e. the point of blade to which the brace extends to and joins at, the outer radius structure is that of typical single airfoil wind turbine blade that is optimally designed to works at the higher relative speed. The combined wind turbine operation is affected by the biplane structures along the inners radius and a conventional airfoil blade for outer length, operable and changeable to improve the overall efficiency and structural weight and cost, while improving reliability. In another aspect, the novel design for a wind turbine system, with an arrangement of apparatus that adjusts aerodynamic profile for the system according to the wind speed, so as to operate the wind turbines safely and even stow the wind turbine with low area of cross section when critical speed is exceeded. The system uses embedded sensors that provide real time feedback and adjusts profile by operating specifically located actuators, so as to ensure that the windmills survive in extremely high wind conditions.

Under very high wind speeds - those exceeding the critical speed, the cross brace and the main blade are folded over and the nacelle yaw mechanism activated and the whole nacelle rotated so as to reverse the direction of machine with respect to the wind flow. The changed geometry gives an overall shape like that of a badminton shuttlecock, which is aerodynamically stable and lowest drag. The arrangement can be considered to be an airfoil with a canard wing formed by the cross brace and the main wing which is a swept back main blade. This arrangement decreases both the lift and drag forces acting on the wind turbine; mainly by reducing the cross section area presented to the wind and also deflecting the winds away from the blades. Another way to analyze this case is that the cross brace and main blade form a staggered biplane structure, with the brace now on the leading edge and the shape is changed to reduce the drag and keeping the structure safe from large forces to be expected in a storm. This combined complex aerodynamic design is used to drive the turbine at controlled speeds to generate power even during a storm while keeping safety as prime concern.

Under extremely high wind conditions, or when extreme turbulence prevails and presence of strong gusts, the blades that are folded over onto the nacelle and are latched down by a controllable mechanism to the body of the nacelle. These latch down further reduce the free movements and vibrations of the blades and decrease the aerodynamic cross section, thus improving reliability of the structures that is critical in order to avoid catastrophic damage even during hurricanes.

In another aspect of the invention, a method is described to control the wind turbine system with active sensing, controllable actuators and machine learning based feedback mechanism to provide dynamic correction as required to ensure stable operation under high wind and rough sea and high wave conditions if the wind turbine is offshore. To achieve this the wind turbine has multiple embedded meteorological monitors measuring the temperature, wind speed, wind direction, barometric pressure, and air density measurements. In addition there are sensors embedded in the structure to measure the stress and strain at various critical points of the structure. The combination of meteorological and strain data with the measured power output allows the empirical determination of strain, and useable power characteristics for the wind turbine under different wind conditions.

In one aspect, the invention describes a method that uses the collected data for generating a model-based mechanical stress and strain prediction along with potential operational power output predicted based on measured wind information and refining and adjusting this model using machine learning algorithms based on the actual operational data. In addition, the method includes measuring real-time operational data from the wind farm and adjusting the power output forecast based on the measured real-time operational data.

In another embodiment, the actual operational data may include any one of or a combination of the following: time of day, month of year, wind temperature, wind pressures, wind speed, wind direction, wind shear, wake, wind turbulence, wind acceleration, wind gusts, wind veer, distribution of mechanical strain across multiple parts, mechanical shear, torsion on each structural element, with measured torque output, power output of generator, blade and cross brace pitch angle, tip speed ratio, nacelle yaw angle, or any other suitable operational data.

In further embodiments, the method may also include predicting the forecast the wind speeds for a future time period. In yet another embodiment, the future time period may include from few minutes or up to several days in the future. In yet another embodiment, the step of generating the model based wind speed forecast may include using a physics based model. In another aspect, the present disclosure is directed to a method for forecasting the wind speeds and turbulences around the wind turbine. The method includes collecting actual operational wind data and site information for the wind turbine. The method also includes generating a machine learning or deep learning model based wind output forecast based on actual measured wind data, the weather information at the site or locations upwind. In addition, the method includes measuring real time operational data from the wind turbine and adjusting the power output forecast based on the measured real-time operational data. Thus, the method also includes forecasting the power output of the wind turbine based on the adjusted power output forecast. It should be understood that the method may further include any of the additional steps and / or features as described herein.

In another aspect of the invention, a method is described to control an apparatus that adjusts aerodynamic profile for the system according to the wind speed, so as to operate the wind turbines safely and even stow the wind turbine with low area of cross section when critical speed is exceeded. The method takes data collected from embedded sensors that provide real time feedback and adjusts profile by operating specifically located actuators, so as to ensure that the windmills survive in extremely high wind conditions. In addition the method uses combination of all renewable energy sources to ensure the overall system is stabilized, ruggedized and operable offshore under stormy conditions of high wind, rough seas and heavy waves. The method is used to control the offshore system with active sensing, controllable actuators and machine learning based feedback mechanism to provide dynamic correction as required to ensure stable operation under high wind and wave conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter that is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

Fig. 1 A conventional wind turbine design: an example of prior art.

Fig. 2. An embodiment of a wind turbine with a cross bracing joined to the main blades; shown in operating position. Fig. 3. An embodiment of a wind turbine with a cross bracing joined to the main blades; shown in stow position under high winds.

Fig. 4. Details of an embodiment of invention: a wind turbine with a cross bracing joined to the main blades shown in operating position.

Fig. 5.A. Details of an embodiment of invention: a wind turbine with cross bracing joined to the main blades shown in operating position and stow position.

Fig. 5.B Details of an embodiment of invention: a wind turbine with cross bracing joined to the main blades with mechanism for moving from operating position to stow position.

Fig. 6. An embodiment of jointing of blades onto solid mounting block with slots for changing angles from operating to stow position and twisting to change pitch.

Fig. 7. An embodiment of jointing of blades onto mounting block with projections for changing angles from operating to stow position and twisting to change pitch.

Fig. 8. An embodiment with details of joining the cross bracing of blades allowing for rotation for smart blade shape and pitch control.

Fig. 9. An embodiment of joining the cross bracing of blades with airfoils allowing for rotation making of the biplane smart blade shape change and pitch control.

Fig. 10. An embodiment of cross bracing of blades as biplane airfoils and changing the biplane smart blade shape and pitch control.

Fig. 11. An embodiment of invention: wind flow and aerodynamics wind turbine with cross bracing of blades shown in stow position under high winds.

Fig. 12. An embodiment of invention: a wind turbine with latches used for further tying down to the nose the cross bracing and main blades shown here in stow position under extremely high winds.

Fig. 13. A method for control of stow of the wind turbine under high wind

Fig. 14. Method for control of high speed resilient wind turbine during operation and stowing of blades expanding novel algorithms of artificial intelligence.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the terms “turbine”, “wind turbine”, and "wind mill” are used interchangeably.

Fig. 1 depicts a conventional design for wind turbine, with elevation 100 and side view 101. The wind turbine is mounted on a tower 102, that typically rages in height from 10s of meter to 200 meters for newer designs. The higher tower help gather greater speed of winds, as wind speed decreases at ground or surface level because of the friction between moving wind and the stationary surface or ground features. The wind turbine has generator 103 mounted on top of the tower 102, and connected to this generator is a shaft that is turned by wind power turning the turbine blades 104 and 105. A three blades arrangement that is shown here is common, although there are designs with blade counting ranging from 1 to 6 or more. The blades are mounted on a nose cone 107 that is connected to the shaft and in turn rotating the generator 103 housed in the Nacelle 106. The windmill operates when the wind speed is high enough to move the blades at high enough rotational speed to generate electricity at the right frequency, a gear box in the nacelle 106, changes the mechanical speed to match to the right rotational speed for the generator. Below a minimum threshold of wind speed, sufficient energy cannot be generated and control of frequency is not possible, so there is a cutoff wind speed below which the blades are stopped physically using a brake or blades are furled, pitch changed to reduce the angle of attack to zero. Similarly, when the wind speed is very high the gearbox cannot ensure the generation will be at right frequency, and again safety mechanisms decouple the generator and stop the blade movements to stop the generation. Another reason for stopping the blade movement with high wind speed is the high magnitude of potentially dangerous forces (centrifugal in combination with gravity and high frequency deflections and vibrations) acting on the blades that can lead to damage and breakage. However, as high wind speed increases the forces on the blades are much higher and therefore brakes alone cannot restrain the movement. In such a case the pitch of the blades are adjusted to increase the angle of attack of the wind to the aerofoil. At the high angle of attacks and high wind speed, the wind going around the leading edge moves so the boundary layer separates from the leeward surface and the air behind the blades becomes turbulent. This high angle of attack at high speed drastically reduces the lift and a significant increases the drag, a condition referred to as stalling of the aerofoil. After the blades stall, the rotational forces on the turbines are reduced to nearly zero and the rotation is stopped, thus at high wind speeds the turbine does not move due to designed aerodynamic stall and is safe from the high forces from heavy winds. To ensure safe and reliable operation of the wind turbines a smart adjustment of the pitch of blades is therefore a requirement and this is done with pitch control mechanism with a joint that allows rotation of the blades along their long axis. Another approach is to adjust the nacelle direction so as to face away from the wind. Various techniques are used to ensure that when the winds exceed some critical value the turbine does not rotate and large forces associated with high winds does not cause any significant damage to the equipment. As a result, wind turbines typically cut off generation between 15 to 25 m/s (50 to 90 kmph) and the turbines stop moving. This means that the wind generators do not work under stormy conditions when the wind speeds are high, thus potential to generate power is lost. Since storms such as hurricanes can last for few days at a time, and if wind is the primary source of power at the location, as would be the case in areas such as islands and coastal habitats, this would be adding to the plight of the populace suffering through the storms.

The shortcomings of the prior art are overcome and additional advantages are provided by this invention that consists of three main constituent groups of apparatus and methods. Firstly, a design for a system with apparatus, sensors and actuators are described herein, for windmills that can survive and operate in extremely high wind conditions. Secondly, a system is described with a wider operating window working at very low and high wind speeds by changing the aerodynamic profile of the turbine blades and arrangement depending on the wind speed. Thirdly, a method to control the wind turbines system with active sensing, controllable actuators and machine learning based feedback mechanism to provide dynamic correction as required to ensure stable operation under very low and high wind conditions.

Fig. 2 depicts an embodiment of the present invention; here panel 200 is a elevation of the novel wind turbine and 201 is the side view of the turbine. The wind turbine is mounted on a tower 202 and consists of the nacelle 203 that houses gearbox and generator with blades 204 and 205 connected to the shaft on a mounting cone that is connected to the nose cone and rotating shaft as in the prior art shown in Fig. 1. The novel elements of invention are shown as cross brace arms 206 and 207 that are connected to the nacelle 203 with mounting ring 208 that is the root of the bracing support, which is connected with a free rotation joint to the generator 209 and gear mechanism 210. The wind rotor cone 211 is the main structure element to joint the blades to the rotor shaft. The wind turbine nacelle mechanism yaws during operation to turn and face the wind 212 and maximize the operating diameter 213, to get optimal generation, the blades when perpendicular to the rotating shaft, sweep a cylinder of diameter 213 and capture the energy from the wind in that cross sectional area. The wind turbine operates in this mode for a range of wind speeds determined to be safe and below a critical value.

For wind speeds exceeding a critical value, the wind turbine changes the shape as shown in Fig. 3, here panel 300 shows the elevation and 301 is the side view of the system. The mechanism is mounted on tower 302, and consists of nacelle 303 that houses the gearbox and generator with blades 304 and 305, similar to that in Fig. 2, in this case these are blades are pushed to form an acute angle to the shaft and when these blades rotate they form a conical volume albeit of lower cross sectional area. The blades are pushed to form acute angles to horizontal are shown as cross brace arms 306 and 307 that are connected to the nacelle 303 with mounting ring 308 which is the root of the bracing support and is the main mechanism to generate force to angle the blades 304 and 305 forward, and this ring is connected with a free rotation joint to the generator 309 and gear mechanism 310. The wind rotor cone 311 is the structural design that allows the hinged jointing the blades to the rotor shaft to angle the blades to the shaft. The wind turbine nacelle mechanism yaws during operation to turn and face opposite to the wind 312 and minimize the operating diameter 314, which is much smaller than the diameter 313 if the blades were perpendicular to the shaft, as would be during operating position 200 & 201. The angled blades sweep a cylinder to capture only the energy from the wind in the much smaller cross sectional area. The wind turbine goes into this stow position and stays in this mode for a wind speeds above a critical value and returns to operating condition only when it is determined to be safe for operations.

Fig. 4 shows the details for the wind nose cone mechanism that is used to change the angle of the blades depending on the wind speed and change the aerodynamic shape of the wind turbine, here panel 400 shows the side view and 401 is the detailed zoomed in side view of the system. The mechanism is mounted on tower 402, and consists of nacelle with a yawing mechanism 403 allowing the assembly to change directions by turning on a vertical axis, the nacelle further houses the gearbox and generator with blades 404 and 405, in this particular case shown these blades are perpendicular to the shaft and when these blades rotate they form a cylindrical volume of maximum cross sectional area, capturing the most wind energy required. The blades are connected to the cross brace arms 406 and 407 that are connected to the nacelle assembly 403, 409 with mounting ring 410, which forms the root of the bracing support and is the main mechanism to take the backward thrust force on the blades 404 and 405, and this ring is connected with a free rotation joint to the generator 409 and gear mechanism 408 which is also the aft nose. The mounting ring 410 slides on the shaft 411 to change position and change the blade angles and shape of wind turbine.

The cross brace 407 connects to the blade 405 at the vertex which is at a radial distance of Base Length B from the center. By using these cross braces the cantilever length of the blades 404 and 405 is determined only by the length extending beyond the joint and is reduced to Blade Length L down from the total blade length of B + L. Blade cantilever length is significantly reduced with this arrangement, as in the total blade length B + L maybe in the range of 40 to 200 meters and base length B can be in the range of 10 to 50 meters. The effective cantilever length thus is reduced by fraction of 10% to 80%. Since the cantilever main blade is a simple beam, and the deflection of a beam varies as the cube power of the length, if the length of main blade is effectively reduced to 2/3 ^rd its original value its deflection reduces to 8/27 ^nd i.e. nearly down to 29% of the original value, if instead the effective length was halved ( ¹ /s) the deflection will reduce to 1/8 ^th i.e. only 16% of the value seen for the original length. Thus with cantilever reduced by amounts of 10% to 80%, the deflections of the beam are reduced by 30% to as much as 90% of the original values. These reduced deflections are very important as higher deflection increase the likelihood of failure of the blade, which is significant when the stress in the material strains is beyond a critical value or when stressing is repeatedly cycle forming dislocations, micro-cracks and cracks in the materials which develop fractures, voids and weak spots that eventually fail. Therefore with lower cantilever the deflection of beam is reduced to improve the reliability and life of the main blade, while using much lower amount of high strength material, thereby reducing the cost of the system.

The wind rotor nose cone 412 besides providing forward aerodynamic role of maintaining smooth flow of air also provides the structural strength to handle the forces at the bottom of the main blades. This is done here in this invention despite a design that allows the hinged jointing of the blades to the rotor shaft so as to adjust the angle the blades to the shaft.

Another significant advantage of the cross bracing is the sharing of the forces between base of the blade and the vertex that transmits to the cross brace 406 & 407, which in turn transfer it to the root mounting ring 410. The reduction of forces on the nose is important to further improve reliability of the system. The reduction of forces and deflections in turn allow use of lesser material to make the main blade, nose cone and other parts of the turbine improving the weight and the cost of the overall system.

The side view panel 401 shows the details of the jointing requirements of the system here the nose cone 413 is connected to the shaft 414 on which the mounting ring 415 can slide and which is connected to the rest of nacelle housing 416. The hinge joint 417 with hinging pin 418 is used to connect the cross brace 419 to the mounting ring 415 at one end, at the other end the cross brace 419 is similarly connected via hinging joint 420 and hinging pin 421 to the bracing joint 422, which connects to the main blade 423, which in turns connects to the nose cone 413 with hinging joint 424 and pin 425.

The overall geometry of arrangement of the main shaft, blade and cross brace is defined by the Shaft length A, the Base length B, and the cross Brace length C, and angle a. This is used to ensure that the main blades are perpendicular to the main shaft, when the mounting ring 415 is fully against the nacelle body 416. This truss structure is designed with requisite strength for the required forces and strength during operation of the wind turbine.

Fig. 5.A shows the details of how this truss arrangement changes from the operating position to that in case of stowing due to high winds. The side view panel 500 shows the details of the windmill in operating condition, with tower 501 onto which is mounted the nacelle 502, with generator 503 and stopping cone 504, which is connected to the shaft 506 on which the mounting ring 505 can slide and connected to the mounting cone mechanism 507 and the nose cone 508. The Mounting Ring 505 has a hinge joint 509 for connecting to the cross brace 514, that is joined at the other end with hinging joint 513 to blade mechanism 512 and blade 511 is connected to the mounting cone mechanism 507 with a hinge joint.

The side view panel 515 shows the details of the windmill in stow position under high wind condition, with tower 516 onto which is mounted the nacelle 517, with generator 518 and stopping cone 519, which is connected to the shaft 520 on which the Mounting Ring 521 can slide and connected to the mounting cone mechanism 523 and the nose cone 524. The mounting ring 521 has a hinge joint 529 for connecting to the cross brace 528, that is joined at the other end with hinging joint 527 to blade mechanism 525 and blade 526 is connected to the mounting cone mechanism 523 with a hinge joint. The length of the shaft 522 connects the nose cone to the main shaft 520. The side views 500 and 515 highlight the difference and similarity of truss arrangement in the two positions, namely the operating position as shown in 500 and stow position shown in 515. The main difference in the arrangement are in the magnitude of Shaft Length A and A’, where in the stow position 515 the Shaft length A’ is significantly smaller than A as in operating position 500. As the Base Length is fixed value of B, and the Brace Length is shown to be nearly the same, or can change slightly from C in 500 to C’ in 515. This builds compressive forces in the cross brace 528 that in turn pushes on the main blade 526, which are thus pushed forward to form an acute angle to the shaft.

Fig. 5.B shows the mechanism to move the Mounting Ring 505 or 521 from Operating position shown in panel 530 to the Stow position in panel 550. The arrangement is same as what was shown in Fig.5.A with the addition of the fixed actuator housing 531 and fully retracted piston 532 in operating condition and that can be fully extended piston as shown in 533. The stator actuator, that in one embodiment can be either a hydraulic cylinder, or can be a linear actuator motor, or an electromagnetic coil housing or other such actuator stators such as a fixed nut for a lead screw or a worm screw, and the piston arrangement, as can be understood to mean any such motive arrangement used to move the Mounting Ring 505 or 521 and through that ring moves the cross brace 514 or 528 which in turn moves the main blades from perpendicular 511 to angled positions 526, when the structure goes from operating 530 to stowed position 550.

Fig. 6 shows an embodiment of jointing of the main blades to the mounting cone mechanism, where the mounting cone is essentially a solid block with hinges for jointing the blades and slots to allow motion due to changing angle and using cylindrical mounts that rotate to provide required pitch of the blade, where the panel 600 shows the arrangement for Operating Position, with the blades 601 and 602 in perpendicular position, and a substantially solid mounting cone mechanism 603 with the slots 604 allowing the blades to be moved while fully supported in position. The elevation of mounting cone 603 is shown where the main blades are marked 605 and 606 with slots 604 allowing the required movement of the blades. The sections A-A of mounting cone mechanism 618 shows that the blades marked 616 & 617 are hinged onto cylinders 619 that are embedded in solid mounting cone 618, these are shown in side view section B- B’ where the mounting cone is 620 and the blade 622 is mounted on cylinder 623 aligned to move inside a slot 621 . The cylinders marked 619 and 623 are used to rotate inside the mounting mechanism 618 and 620 respectively and so as to change the pitch of the blades while allowing them to be hinged and moving to change the angle as well. The conditions for stow position for the solid mounting cone is shown where cone 607 has the slots 609 for blades 608 and 610. The section B-B for stow position shows the side view of the solid block 611 with slots 612, while the section C-C elevation shows the elevation of the solid block 614 with blades 613 and slots to allow motion for change of angle and rotatable cylinders 615 that allow rotation to change the pitch.

Fig. 7 shows an embodiment of jointing of the main blades to the mounting cone mechanism where the mounting cone is essentially a solid block with projections with hinges for jointing the blades and accommodates motion to change angle and the hinge projections are mounted on cylindrical that rotate to provide required pitch of the blade. The panel 700 shows the arrangement for Operating Position, with side view showing the nose cone 701 , solid mounting cone 705, with projections 702 and 706 that are connected to the rotating cylinders 710. The projections 702 and 706 connect to the blades 703 and 707, with hinging pins 704. The elevation shows nose cone 708, with blades 713 mounted on projections 711 and 712 with hinge pins 709. Further as seen in section A-A, the solid block 719 has the embedded cylindrical projections 715 that can rotate but are connected with a pin joint to provide a hinge joint for the blades 716 and 717. The arrangement for stow position is shown in panel 740 with nose cone 720, connected to the mounting cone 724, which has cylinders 727 holding the projections 723 and 725 with hinge joints for blades 722 and 726. The elevation shows the nose cone 728, projections 730, hinging pin joints 729 for connecting to blades 731 , 732 and 733 that are operable to change the angles from perpendicular to another acute angle.

The jointing of the cross brace to the main blade has to be hinged as well to allow the truss arrangement to change angles between operating and stow positions, in addition it has to allow the pitch of the blade to be changed thus allow free rotation along the long axis. An embodiment of the joint between the cross brace and the main blade is shown in Fig. 8, here panel 800 shows the elevation, while side view is shown in panel 801 and finally panel 802 shows the isometric view of the arrangement. The cross brace 803, 819 is shown here coming at an angle to the main shaft of the blade marked as 808, 816 and 822. The elevation shows one end of the brace 803, connected to single eye head 804 that inserted into a fork or double eye head 806, to form a hinged joint to with pin 805 joining them. The fork head 806 is connected to the cylinder 811 that is mounted on axial load bearings 810 and 812 so as to freely rotate on the shaft 808, while transferring axial and perpendicular forces to the cylinder. The airfoil section of the main blade is shown built with shaping ribs 809 and 814 where the upper surface is covered with covering sheet 813 made out of fabric, glass or carbon fiber composite with matrix layered together to provide a light weight surface with requisite strength. Similarly the lower surface is covered with covering sheets 807 and 815, note that the bottom covering has the required gap to allow passage and movement of the cross brace rod 803 that is jointed from below to the main shaft 808. The side view 801 shows the airfoil shape of rib 817 and main shaft 816. The arrangement can be better seen in the isometric view 802, where the cross brace 818, is connected to the single eye head 819, which joins to the double eye head 820, connected via the pin 821. The double eye head 820 connects to the jointing cylinder 826 that connects via axial load rotating bearings to the main shaft 822. The airfoil shape is formed with structural shaping ribs 824 and 825, with top surface covered with 823 and bottom surface opened near the joining mechanism to allow free movement of structural elements.

In another embodiment using the cross brace, the brace is an airfoil shape, this allows the mechanism to extract and affect maximal control on the lift and drag forces from the structure in order to optimize performance under operating and stow conditions. An embodiment of the joint between the airfoil cross brace and the main blade is shown in Fig. 9, here panel 900 shows the elevation, while side view is shown in panel 901 and finally panel 902 shows the isometric view of the arrangement. The cross brace 903, 918 is shown here coming at an angle to the main shaft of the blade marked as 908, 916 and 922. The elevation shows one end of the brace 903, connected to single eye head 904 that is inserted into a hinged joint to a fork or double eye head 906, with pin 905 joining them. The fork head 906 is connected to the cylinder 911 that is mounted on axial load bearings 910 and 912 so as to freely rotate on the shaft 908, while transferring axial and perpendicular forces to the cylinder. The airfoil section of the main blade is shown built with shaping ribs 909 and 914 where the upper surface is covered with covering sheet 913 made out of fabric, glass or carbon fiber composite with matrix layered together to provide a light weight surface with requisite strength. Similarly the lower surface is covered with covering sheets 907 and 915, note that the bottom covering has the required gap to allow passage and movement of the cross brace rod 903 that is jointed from below to the main shaft 908. The side view 901 shows the airfoil shape of rib 917 and main shaft 916. In addition the airfoil shape of the brace is shown with similar airfoil 919 wrapped around the cross brace shaft 918. The arrangement can be better seen in the isometric view 902, where the cross brace 918, is connected to the single eye head 919, which joins to the double eye head 920, connected via the pin 921. The double eye head 920 connects to the jointing cylinder 926 that connects via axial load rotating bearings to the main shaft 922. The airfoil shape is formed with structural shaping ribs 924 and 925, with top surface covered with 923 and bottom surface opened near the joining mechanism to allow free movement of structural elements. The cross brace airfoil shape is formed around the shaft 918 by using ribs 927 and covering fabric 928.

The use of airfoil section of the cross brace can be understood and better appreciated when seen as a collection of biplane cross section. This is shown in Fig. 10 where the Elevation is shown in panel 1001 , while panel 1002, 1003 and 1004 shows sectional side views at different points, highlighting the varying nature of the biplane airfoils. The elevation 1001 shows the main shaft 1010 is jointed to the cross brace 1008 which is connected to single eye head 1009, that is inserted in double eye head 1006, hinging around the pin 1005. The double eye head 1006 is connected to the cylinder 1013 that in turn is mounted on the main shaft 1010 with axial rotational bearings 1012 and 1014. The main blade airfoil shape is formed around main shaft 1010, with ribs 1011 , 1015, 1017 and 1018, with upper surface covered with 1016 and lower surface covered with covering 1007 and 1019. There are three sections shown here namely section A-A in panel 1002, section B-B in panel 1003, section C-C in panel 1004. Section A-A shows the cross section closest to the joint therefore has the main joining cylinder 1013 and brace head 1009 along with airfoil covering 1016, showing opening at the bottom surface to allow free movement of joining structures. Section B-B shows the cross section some distance away from the joint cutting across an airfoil rib structure, showing main shaft 1010 airfoil rib 1017, upper covering 1016 and lower covering 1019, also shown are the cross brace shaft 1008 along with airfoil covering 1020. This forms a staggered biplane arrangement between the airfoils 1017 and 1020. Section C-C shows the cross section a further distance away from the joint cutting across an airfoil rib structure, showing main shaft 1010 airfoil rib 1018, upper covering 1016 and lower covering 1019, also shown are the cross brace shaft 1008 along with airfoil covering 1020. This forms another staggered biplane arrangement between the airfoils 1018 and 1020. The biplane arrangements in sections B-B and C-C differ in the arrangement between the two airfoils in terms of the distance, the relative alignment of the shapes and overall shape, the two airfoils are further apart in section C-C as compared to that in section B-B. The staggered biplane arrangement is used to control the airflow around the main blade and the cross brace in order to control the wind wake and turbulence behind the main turbine blade, in addition this can be modified by independently changing the pitch of the two airfoil sections so as to deliver optimal combined airfoil depending on the varying wind conditions and power requirements.

The wind turbine described herein is designed to safely operate and survive high winds and extreme weather conditions such as found in hurricanes. One embodiment of this is shown in Fig. 11 , where under high window scenarios the wind turbine yaws so as to present the aft of the turbine to the windward side and have the blades angled out to form an acute angle with the shaft. 1100 is the elevation of the wind turbine and 1101 gives the side view. The turbine is mounted on the tower 1102, with nacelle 1103, blades 1104 and 1105, sweeping a diameter 1113 as opposed to fully extended diameter shown as 1111. The side view shows angling of the blades 1104 and 1105 pushed into place with braces 1106 and 1107 with nacelle housing the generator 1109 and linear actuator stator 1108. The cross section area swept by the main blades is significantly reduced when in stow as the diameter is 1113 is much smaller than 1111 when the blades are perpendicular, this greatly reduces the forces acting on the blades. The cross brace arms 1106 and 1107 are staggered ahead in this case, as the wind hits them first, here the airfoil shape of these structural beam will be used to generate the required amount of lift under high wind conditions without stalling, the wake created by these airfoils reduces the lift on the main blades and reduces the forces acting on the blades significantly. The wind streamlines are shown in 1112 and 1113 to highlight the aerodynamic impact of the structural design. The aft nose cone 1108 and nacelle is designed to deflect the high speed winds away from the blades as shown in 1113, this wake created by the aft nose cone further reduces the forces acting on the blades 1104 and 1105 also on the cross brace structure 1106 and 1107. With this appropriate aerodynamic design the wind turbine will have significantly lower forces acting on it under high wind conditions and this will enable controllable operation even for very high winds and ensure resilience and reliability of the composite structure even in case of extreme winds experienced during hurricanes. There are multiple sensors embedded into the various structural elements of the wind turbine, these sensors include anemometers, pressure gauges, LiDARs, vanes and Venturi tubes for measuring wind speed, strain gauges, thermometers that are placed on tower 1102, main blades 1104 & 1105, cross braces 1106 & 1107, aft nose cone 1108, nacelle body 1109, nose cone 1110 and even placed in the field aft and forward of the operating wind turbine.

Despite the reduction of forces on the blades achieved by stowing of blades as described earlier, it is possible that under extreme wind conditions as seen during hurricanes, turbulence in wake can be unpredictable and lead to excessive vibrations of the structures. These uncontrolled motion and vibrations can be a cause for concern impacting the robustness and life of the wind turbine. These concerns about vibrations can be mitigated significantly by temporarily joining the mobile parts to the stronger structural elements. An embodiment to address this is shown in Fig. 12, where the side view 1201 shows the tower 1202, with main blades 1204 and 1205, cross brace 1203 and 1206 and brace mounting ring 1207 with aft nose cone 1208 and generator and nacelle housing 1209, and forward nose cone 1210. The normal stowing operation is illustrated in the zoomed side view 1211 , where the blades 1213 are angled outward from the nacelle, pushed into the position by braces 1212 and 1214, with brace mounting ring 1215 pushed forward on the shaft 1216. In case of extreme wind conditions the arrangement is modified as shown in the zoomed side view 1221 , where the blades 1223 are angled outward from the nacelle, pushed into the position by braces 1222 and 1224, with brace mounting ring 1225 pushed forward on the shaft 1226, the main modification is extension of retractable latch 1227 that tightly join the main blades 1223 to braces 1224, similarly latch 1228 joins the main blade 1223 to brace 1222. The latches can be solid, or chain link or metal ropes, which are used to create a rigid joint between the various structure elements. These latches make the whole arrangement rigid and reduce the motion significantly enough so as to increase the robustness, reduce the vibrations and improve the operational life of the wind turbine.

An embodiment of method to control the change of position from operational to stow position is shown in Fig. 13. The weather forecast 1301 is used to anticipate the expected conditions at the site and atmospheric measurements 1302 made with local instruments to validate the forecast and modify expectations accordingly, the main parameter of wind speed is measured with multiple sensors 1303, and depending on the magnitude of the wind speed 1304, the turbine is operated. If the wind is in the allowed operation range as per 1304, a physics based simulation model 1305 is run to simulate the interaction of the system with the wind and predict stresses and forces in the structure and to optimize efficiency of energy conversion, the blade and brace pitch are adjusted 1306 to optimize generating efficiency. The impact of the wind on the structure is measured using strain sensors embedded in the blades, brace, nacelle and tower, these forces are monitored 1307, also measured is the airflow around the structure using sensors of varying accuracy 1308 especially to measure turbulence 1309, of incoming wind with instruments such as Aeroprobe, Laser Doppler Anemometry, Constant Temperature Anemometer and the Particle Image Velocimetry. This information is combined with model 1305, measured data on shape 1306, forces 1307, and air flow 1308 to modify the airfoil shape 1310 and this loop of 1304, 1305, 1306, 1307, 1308, 1309 and 1310 is repeated continually during the operations. If the measured wind exceeds the critical value the wind turbine is moved into stow position, if high winds are forecasted 1301 and atmospheric measurements 1302 match forecast, the weather forecast for high winds is considered validated 1311 , and the wind speed and characteristics monitored appropriately with increase in the frequency of data collection 1312 to allow timely response. When the wind speed exceeds critical value 1313, the blades are moved to stow position. The interaction of high wind speed with aerodynamics is modeled with a phsyics based model 1314 with rapid monitoring of speed, and changing of shape 1315 and measurement of forces 1316 is done with focus on impact of high wind speed on forces, torques and stresses to ensure structural integrity and safety, and the shape adjusted according to 1314 and 1315. If the wind exceeds extreme threshold value the blades and braces are latched down together 1317. The continual monitoring of wind speeds 1312, along with weather forecast 1311 is used to predict the relaxation of high wind conditions which are compared to the thresholds and only when it is predicted that low winds are expected to be consistently seen 1318 does the system move from latched and stowed positions back to operational regime 1319.

The control of fast moving, complex and dynamic machinery used in extreme environment requires sophisticated, fast and robust control methods. Methods that can work consistently in ever evolving unpredictable environment and are robust enough to deliver assured reliability. Expanding upon artificial intelligence methods, in particular machine learning and deep learning methods provides the right tools for use here. An embodiment for method of control is used in this invention using available data, control features and methodology to deliver desire results. Fig. 14 shows the methods used for control of the wind turbine structure described here in that can operate in high wind conditions and is robust and resilient even in hurricanes. These methods using artificial intelligence techniques are used during operation, stowing of blades and ensuring survival in most extreme conditions. The methods use Weather Data 1401 , which is processed along with measurements to develop and refine a machine learning model 1402 that evolves with every iteration. The model predictions 1403 are used to quantify the errors and further enhance the model to be used for future predictions along with Deep Learning and Control methods 1404 to ensure efficient performance, adjust control features to deliver expected conditions and ensure structural and environmental interactions are bounded to ensure system integrity and safe, secure and resilient performance under the highest wind speeds. The data 1401 consists of measurements of atmospheric parameters 1410 such as pressure, relative humidity, temperature, wind speed, direction, wind shear amongst others. This is combined with recent meteorological data and local weather history 1411 to build a synoptic data story 1412 along with Numerical weather prediction 1413 to anticipate the expected evolution of the local weather. This combined dataset provides rich information for evaluating the state of accuracy of the learning models by using past predictions 1414, then calculating the errors in predictions by comparing to the actual measurements 1415, this error can then be minimized using Machine Learning methods 1416 such as supervised and unsupervised learning to identify the trends or time series and forecast expected data in near future, in addition using specific reinforcement learning methods 1417 to choose the parameter settings by rewarding correct predictions from past and finally use deep learning neural networks 1418 and image processing driven by convolutional neural network to identify large area or global trends from past similar episodes and recognize the characteristic that can be leveraged to predict the evolution from current state of the weather to next few minutes, hours and days. Such models are used to predict variety of characteristics including local wind behavior 1419, turbulences and eddies formed by the wind 1420, time evolution of these characteristics 1421 , and impact of the wind turbine structure in its immediate neighborhood and the wake it and its components such as blade, braces, nacelle and tower create 1422. In addition, there are important complex interactions between various factors such as structure and wind 1423 and spatial and temporal distribution of forces for stress predictions 1424 which are then used to predict deflections of various structure parts 1425 and vibrations in the overall arrangement that has significant impact on the strength of the materials and reliability of the structure 1426. These complex predictions are necessarily done using specially designed deep learning models, where the models are refined to predict the environmental factors such as weather, wind distributions 1427 and used to predict the structural forces 1428 which in turn modify the shape of the airfoil with pitch control 1429, that then impact the statics, kinematics and aerodynamic aspects of the structure 1430 to predict a complex wind and structure interaction 1431 . All together these deep learning methods provide a method to solve for complex control needed to ensure the longevity and robust operation of the wind turbine in harsh environmental conditions.

The present invention described herein for wind turbine safely operable in hurricane prone areas consists of novel structural design with ability to change the shape using aerodynamic principles and finally using novel advanced artificial intelligence methods to provide sophisticated control despite the complex aspects of the problem. Further, the data processing functions disclosed herein may be performed by one or more program instructions stored in or executed by such memory, and further may be performed by one or more computing modules configured to carry out those program instructions. Computing modules are intended to refer to any known or later developed hardware, software, firmware, machine learning, artificial intelligence, fuzzy logic, expert system or combination of hardware and software that is capable of performing the data processing functionality described herein.

The foregoing descriptions of embodiments of the present invention have been presented for the purposes of illustration and description and not intended to be exhaustive or to limit the invention to the precise forms disclosed. Accordingly, many alterations, modifications and variations are possible in light of the above teachings, may be made by those having ordinary skill in the art without departing from the spirit and scope of the invention. For example, notwithstanding the fact that the elements of a claim are set forth below in a certain combination, it must be expressly understood that the invention includes other combinations of fewer, more or different elements, which are disclosed in above even when not initially claimed in such combinations. The words used in this specification to describe the invention and its various embodiments are to be understood not only in the sense of their commonly defined meanings, but to include by special definition in this specification structure, material or acts beyond the scope of the commonly defined meanings. Thus if an element can be understood in the context of this specification as including more than one meaning, then its use in a claim must be understood as being generic to all possible meanings supported by the specification and by the word itself. The definitions of the words or elements of the following claims are, therefore, defined in this specification to include not only the combination of elements which are literally set forth, but all equivalent structure, material or acts for performing substantially the same function in substantially the same way to obtain substantially the same result. In this sense it is therefore contemplated that an equivalent substitution of two or more elements may be made for any one of the elements in the claims below or that a single element may be substituted for two or more elements in a claim. Although elements may be described above as acting certain combinations and even initially claimed as such, it to be expressly understood that one or more elements from a claimed combination can in some cases be excised from the combination and that the claimed combination may be directed to a sub-combination or variation of a sub- combination. Insubstantial changes from the claimed subject matter viewed by a person with ordinary skill in the art, now known or later devised, are expressly contemplated as being equivalently within the scope of the claims. Therefore, obvious substitutions now or later known to one with ordinary skill in the art are defined to be within the scope of the defined elements.

The claims are thus to be understood to include what specifically illustrated and described above, what is conceptually equivalent, what can be obviously substituted and also what essentially incorporates the essential idea of the invention.

While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.