Abstract:
A wind turbine system includes a variable blade assembly including adjustable sails and wing shaped masts expanding the wind velocity capture envelope. The blade assembly turns a hydraulic pump, which pressurizes fluid and stores the pressurized fluid in a chamber in the support tower. Pressurized fluid is directed via an electronically controllable proportioning valve to a hydraulic motor which is coupled to an electric generator. A computer control module operates the proportioning valve regulating pressure to the hydraulic motor, maintaining generator rotational speed, and providing consistent output frequency to the power grid. Stored energy in the high pressure tank is used to continue generator operation after the winds cease, allowing early warning notification to the power management system of impending power loss. Residual pressure maintained in the high pressure tank allows restart operations via hydraulic pressure rather than power grid energy drain. On site high energy capacitors store additional energy.

Description:
RELATED APPLICATIONS  
       [0001]     The present application is a continuation of U.S. patent application Ser. No. 11/190,687 which was filed on Jul. 27, 2005 and which is hereby expressly incorporated by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to alternative energy sources, and more particularly, to methods and apparatus for advanced wind turbine design.  
       BACKGROUND  
       [0003]     Current wind turbine designs typically utilize direct drive generators or gear driven generators coupled to the wind turbine shaft. In such designs, there is an inherent problem in that as the wind speed varies the output frequency of the generator will also vary. However, for the generator output to be usable by the power grid, the output signal needs to be converted to match the power grid frequency, which is 60 Hz in the United States and 50 Hz in Europe. Typically, an additional frequency conversion stage is used to convert from the variable wind turbine generator output frequency to the constant grid frequency. Such an additional frequency conversion stage can include invertors and/or other phase correction circuitry. Such conversion stages can be costly and complex to implement and maintain. In addition, there is an inherent inefficiency which results in the frequency conversion process resulting in lost energy. It would be desirable if new methods and apparatus for wind turbine designs resulted in the generator output frequency being controlled to match the power grid frequency without the need for an additional frequency conversion stage.  
         [0004]     Current wind turbines designs which connect to a power grid provide no or very limited warning of the loss of output due to unfavorable wind conditions. Loss of generator output can be due to low wind or no wind conditions resulting in insufficient wind energy to continue to drive the turbine. Loss of generator output can also be due to high wind conditions which could overstress the wind turbine elements if the wind turbine operation was allowed to continue, and thus the wind turbine is typically intentionally taken off-line during the interval of detected high winds to prevent damage to the wind turbine. Inconsistencies of the wind turbine generator output power level and rapid cutoffs result in balancing problems from the perspective of power grid management. Under such conditions, the power grid has a very small amount of time to locate and bring on line alterative sources of power to continue to balance the grid, regulate voltage levels within an acceptable band, prevent line voltage sags/spikes in order to continue to meet customer energy requirements and/or maintain an acceptable quality of service. It would be desirable if new methods and apparatus for wind turbine designs resulted in the wind turbine generator output being controlled to provide a more uniform power output level irrespective of changing wind conditions. It would also be beneficial if new methods and apparatus of wind turbine designs provided for more gradual degradations in energy output levels and/or provided earlier warnings to the power grid of an impending loss of output power.  
         [0005]     Following a shutdown, current wind generator turbines typically need to use electricity/power from the grid to reinitialize themselves and get back in operation. In many cases, a low velocity wind does not provide enough energy to start the rotation of the wind turbine so power from the grid is needed to drive a motor to start the spinning. Wind turbine start-up energy requirements place additional loads on the power grid. In a grid coupled to a larger number of similar or identical wind turbines in the same general area subject to the approximately the same wind conditions, it would not be unusual for many of these wind generator turbines to try to start up at approximately the same time, thus placing a substantial short term additional load on the grid. In view of the above, it would be advantageous if the methods and apparatus were developed which allowed the wind turbine generates to start up under their own power, following an interruption due to wind conditions, thus removing the start-up loading burden placed on the grid, which draws energy from the grid and tends to upset grid power balancing management.  
         [0006]     Another problem facing current wind turbines is that the energy absorption bandwidth is typically rather narrow. Most current wind turbines are shut down at wind velocities which are either too low or too high. A typical wind velocity bandwidth for existing wind turbine systems is approximately 9 mph to 25 mph. It would be beneficial if new methods and apparatus of wind turbine designs expanded the energy absorption bandwidth allowing the wind turbine to continue to absorb wind energy for lower and/or higher wind velocities than current systems, thus capturing more wind energy on average over time.  
         [0007]     Current wind turbines have turbine blades, which are designed to produce energy in a 9 mph to 25 mph band. In order to produce energy in low velocity winds the blades can be variable pitch blades, which allow for the capture of energy at low wind speeds. In order to be able to catch the low velocity wind energy and operate the turbine, the turbine blade area has to be sufficiently large. However, implementing a large turbine blade area designed to accommodate the capture of wind energy at relatively low wind velocities becomes a detriment to the capture of wind energy at relatively high wind velocities, as the larger size blades increase the likelihood of potential structural failure at the high wind velocities. Therefore, with such an implementation using larger size turbine blades to capture energy from low velocity winds, the wind turbine is required to be shutdown at a lower upper wind velocity limit to prevent potential structural damage. In view of the above it would be advantageous if new methods of apparatus of wind turbine design are adaptive to accommodate the unique design requirements at both the low velocity end and high velocity end.  
         [0008]     Current wind turbines have very limited or no energy storage capability. Intervals of high wind energy capture time due to favorable wind conditions within the energy absorption band typically do not correspond to customer power level requirements. The excess energy is typically either wasted, e.g., burned off by a power consuming activity of the wind turbine, or dumped into the grid with the grid power management adjusting energy input from another source, e.g., decreasing energy output at fossil fuel power plant, to accommodate for the increased energy from the wind source. Even small improvements in wind turbines can lead to significant energy efficiencies and corresponding environmental benefits. Accordingly, it would be advantageous if methods and apparatus of wind turbines were developed so that the wind turbines included significant energy storage capability. In addition, it would be highly desirable if the range of wind speeds at which turbines could be used to produce power could be increased.  
       SUMMARY OF THE INVENTION  
       [0009]     The present invention is directed to methods and apparatus of advanced wind turbine design, control, and energy storage. Various features of the present invention may be deployed alone or in combination.  
         [0010]     One feature of various embodiments of the present invention is that the wind turbine system includes a wind turbine blade assembly which is coupled to a hydraulic pump, e.g., directly, thru a gearbox, or thru a transmission assembly. In some such embodiments, the tower upon which the wind turbine blade assembly and/or hydraulic pump is mounted is a hollow tower, e.g. metallic steel chamber, which includes a high pressure vessel into which the wind turbine driven hydraulic pump sends the pressurized hydraulic fluid to the high pressure vessel, e.g., reservoir. The pressure vessel may be an integral part of the tower support structure. The tower can also include a low pressure feed reservoir, e.g., in its base. In some embodiments, the low pressure feed reservoir may be part of a separate structure, e.g., a base structure or an in-ground tank. The low pressure inlet side of the hydraulic pump can be fed from the low pressure tank via a feed tube which is located internal to or adjacent to the tower. The high-pressure fluid output from the hydraulic pump is used to power a hydraulic motor, which is coupled to an electric generator. A hydraulic proportional control valve controls the speed/rpm at which hydraulic motor is turned which in turn controls the speed/rpm at which the generator is turned. Operating under the direction of a computer control module processing input from sensors, the proportioning control valve is computer controlled so that the frequency of the generated electricity will match the grid frequency specifications thus making the generated power directly usable and eliminating the need for invertors or other electronic means to convert the generated power signals to the grid frequency.  
         [0011]     In accordance with some embodiments of the present invention, the volume of high pressure tank is such that the process described above will allow for the storage of energy, e.g., excess capacity energy, in the high pressure tank such that operation of the hydraulic motor, and the generation of electricity can continue for an extended period of time after the wind turbine blades have stopped spinning, e.g., due to insufficient wind speed. The hydraulic motor continues to operate driving the generator and generating electricity while the pressure level in the high pressure tank slowly decreases. This feature of the present invention allows the output of power from the wind turbine system for some time after the wind sensor will have notified the grid of an impending loss of power do to high or low wind velocity. This extended time period of electrical output allows for notification to the grid of a power generation loss in that the wind turbine system, which has now become an energy storage medium which is being depleted. This early notification feature allows for the power grid management system to accommodate for an impending loss of wind source power onto the grid by preparing to adjust other power sources, e.g. fossil fuel power source, output levels. The wind turbine system can, and in various embodiments does, notify the power management system in advance of the point in time when the wind turbine system will cut off the electrical output to the grid. The wind turbine system can, and in various embodiments does, notify the power management system in advance of the point in time when the wind turbine system will reconnect to the grid to deliver energy.  
         [0012]     In accordance with another feature of various embodiments of the present invention, the stored energy in the form of hydraulic pressure is allowed to be reduced to a point, but not beyond such a point, where the sensors indicate that there is enough reserve capacity left in the pressurized hydraulic fluid such that a restart the wind turbine. Then when wind conditions permit restarting of the turbine is implemented by using the remaining hydraulic pressure to restart the hydraulic pump and start the turbine blade assembly spinning. This approach of the present invention of using stored hydraulic pressure to restart the wind turbine removes the load demands typically placed on the power grid to restart a wind turbine system. When wind conditions permit and the computer control system decides to initiate a restart operation, the reserve capacity then be rerouted thru the hydraulic system so that the hydraulic pump is temporarily turned into a motor to bring the turbine up to the minimum required speed, which will restart the energy production cycle. The high pressure fluid or a regulated level thereof can be rerouted to the low pressure feed tube via a computer controlled primer valve. The low pressure feed tube can include a check valve to prevent the high pressure hydraulic fluid from entering the low pressure reservoir.  
         [0013]     In some embodiments, of the wind turbine system described above, the hydraulic system included as part of the wind turbine system does not require any minimum rotor speed to produce or store energy i.e., stored fluid under pressure can be used to produce electric. In some such embodiments, the wind turbine system will pump hydraulic fluid into the reservoir until it is full at high pressure at which point the generator will be activated until it bleeds power/hydraulic fluid pressure down to the restart reserve level. In some embodiments, of the present invention, the computer control system will maintain pressure in the high pressure tank above the minimum restart level, and generator operation may be activated provided the level is above the minimum restart level. In some embodiments, during periods of excess energy generation from wind power, e.g., the power grid does not require the level of generator output energy at present, excess energy may be stored, e.g., by increasing hydraulic pressure in the high pressure tank and/or routing electrical energy to a electrical storage device or devices, e.g., capacitor and/or battery bank. In some embodiments, during periods where the energy level of generation wind power is lower than the level being extracted from the high pressure fluid, e.g., the power grid requires more output energy at present than the wind is producing, energy may be extracted from the pressurized fluid decreasing the pressure level in the high pressure tank.  
         [0014]     In various embodiments, the wind turbine system is implemented using multiple hydraulic motors and/or multiple generators. In some such system, each hydraulic motor can be controlled independently via its own electronically controlled proportioning valve and feedback circuitry. In some such multiple hydraulic motor and/or multiple generator systems, different combination can be activated at different times to accommodate changing load requirements and/or changing wind conditions.  
         [0015]     Another feature of some embodiments of the present invention is the use of adjustable sails in the blade assembly of the wind turbine system. In some such embodiments, the turbine blades have a roller reefing sail system or variation thereof, whereby the area of the blade/sail combination will be variable. In various embodiments including a controllable sail feature, the wind turbine system includes masts, e.g., carbon fiber masts, on a hub with electronically or hydraulically reefed sails. The wind turbine system includes, in various embodiments, a wind speed sensor and/or a wind direction sensor. When the wind speed sensor indicates a lower wind velocity condition the sail area can be controllably increased, when possible, by unfurling the roller reefed sails using hydraulic and/or electric powered motors or other mechanical means. Some embodiments include sensors to determine the position of the sails. When the wind speed rises the sails can be controllably drawn in or reefed. The sails are fully withdrawn into the masts at high wind velocity, where the additional sail area could result in structural damage to the wind turbine blade assembly.  
         [0016]     Another feature of some embodiments of the wind turbine system is that the masts themselves are formed to have a mild wing shape. Some such masts are designed such that they can withstand and collect energy at projected wind velocities at the high end which far exceeds the wind capture high end velocities of typical fixed area blades conventionally used. For example a mast structure, in accordance with the present invention can have a smaller wind collection surface area than typical fixed area blades deployed since it can be used at the high velocity end but need not be relied upon to the be primary wind collection source at the low wind velocity end, where the sail dominates. In some such embodiments including a mild wing shaped mast, the mast structure also includes a twist. The implementation of the wing shaped mast and the adjustable sails would allow for much more energy production over the course of time by allowing for energy production over a much larger wind speed range than current designs. For example at very high wind levels, the wind shaped masts having comparatively small cross sectional area could capture high velocity wind energy, while at very low velocity wind levels the comparatively large cross sectional area provided by the unfurled sails could capture low velocity wind energy. Thus the wind velocity capture envelope, could, with such design features, of the present invention, be larger and expanded at both the low and high ends over convention designs.  
         [0017]     As another feature of some embodiments of the present invention, in addition to the energy storage capacity in the high-pressure hydraulic fluid described above, some hydraulic fluid could be displaced in the tower structure for a high-energy capacitor. For example, in some such embodiments, a carbon nanotube capacitor with energy storage densities of 30 Kilowatt-Hours per kilogram is incorporated into the fluid bath, collocated with the tower or located near the tower, which provides for a much larger onsite energy storage solution. In one such embodiment, including a ten thousand pound capacitor of this type material, the wind turbine system could store energy such that a 4-Megawatt wind generator could continue to operate for 34 hours of extended output after the hydraulic motor drive has been shut off. This approach of the present invention can smooth the energy curve, improve the efficiency of a wind turbine system and/or allow for a larger amount of energy to be sent to the grid over time.  
         [0018]     The above-described systems can include sensors, control systems, software and hardware, which can be modified for requirements based on the size and needs of the system. Some embodiments of the above wind turbine system include a computer control module which includes a processor, e.g., a CPU, memory, and interfaces. The memory includes routines and data/information. The processor executes the routines and uses the data information in memory to control the operation of the wind turbine system and implements the methods of the present invention. Some such functions performed by the computer control module may include, monitoring of wind speed and/or wind direction, monitoring and control of the position, e.g., heading the blade assembly, monitoring of the position of the sails and control of the sail deployment, monitoring and control of the hydraulic pump, monitoring and control of the hydraulic motor, control of the proportioning valve, control of the primer valve, control of restart sequences, monitoring of the pressures in the high and low pressure chambers, regulation of pressure, monitoring of generator output, switching of generator output to the grid and/or to electric storage devices, control of energy transfer from electric storage devices to the grid, communications and notifications to a management network, communications protocol operations, switching control of a plurality of hydraulic motors and/or generators, and/or fault detection monitoring, reporting, and/or shutdown operations.  
         [0019]     The system of the present invention can have a relatively large sail (blade) surface areas even with blades having relatively small diameters, e.g., less than 300 feet and in some cases, e.g., diameters less than 50, 100, 200, or 250 feet, allowing the system to operate with smaller diameter blades compared to some known systems and/or at lower wind velocities. As a result of using smaller diameter blades the velocity of the blade tip as it rotates can be lower than known systems which have larger blade diameters. Since the noise generated by a windmill is in part a function of the velocity of blade tips as they rotate, it is possible to generate less noise using embodiments of the invention with shorter blade diameters than would be generated by existing systems with much larger blade diameters. Since noise is one reason people tend to object to windmills, the methods and apparatus of the present invention can prove beneficial in terms of noise reduction as compared to known systems.  
         [0020]     Numerous additional features benefits and embodiments of the present invention are discussed in the detailed description which follows. 
     
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0021]      FIG. 1  is a drawing of an exemplary wind turbine system implemented in accordance with the present invention and using methods of the present invention.  
         [0022]      FIG. 2  is a functional drawing used to describe operations and flow in an exemplary wind turbine system during conditions where the blade assembly, which is capturing wind energy, is driving the hydraulic pump, and there is sufficient stored energy in the high pressure tank to drive the hydraulic motor in accordance with the present invention.  
         [0023]      FIG. 3  is a functional drawing used to describe operations and flow in an exemplary wind turbine system during conditions where the blade assembly has stopped rotating and is no longer capturing wind energy; however, the high pressure tank has sufficient energy stored above the minimum level needed for a restart such that hydraulic motor operation and generator operation can continue in accordance with the present invention.  
         [0024]      FIG. 4  is a functional drawing used to describe operations and flow in an exemplary wind turbine system during a restart operation of the blade assembly in accordance with the present invention.  
         [0025]      FIG. 5  is a drawing illustrating components in an exemplary blade assembly in accordance with the present invention.  
         [0026]      FIG. 6  is a drawing illustrating the exemplary blade assembly of  FIG. 5  except showing the sails in a partially reefed in position.  
         [0027]      FIG. 7  is a drawing illustrating an exemplary mast or boom/inner shaft/sail structure in accordance with some embodiments of the present invention.  
         [0028]      FIG. 8  is a drawing of a head on view of an exemplary hub assembly in accordance with the present invention.  
         [0029]      FIG. 9  is a drawing illustrating an energy storage feature in accordance with some embodiments of the present invention.  
         [0030]      FIG. 10  is a drawing illustrating an exemplary mast or boom/inner shaft/sail structure in accordance with various embodiments of the present invention.  
         [0031]      FIG. 11  is a drawing showing some components included in the exemplary structure of  FIG. 10  from a different perspective. 
     
    
     DETAILED DESCRIPTION  
       [0032]      FIG. 1  is a drawing of an exemplary wind turbine system  100  implemented in accordance with the present invention and using methods of the present invention. Exemplary wind turbine system  100  includes a blade assembly  102 , a main drive housing  104 , a support tower  106 , a hydraulic motor and generator housing  108 , a low pressure tank  110 , and a computer control module  112 .  
         [0033]     The blade assembly  102  includes a hub  114 , a sail deployment gear set  116 , a plurality of sail shafts/blades  118 , and a plurality of retractable sails  120 . The blade assembly  102  is used to capture wind energy. The blade assembly  102 , in some embodiments includes a rolling reefing sail system, whereby the area of the sails is variably adjustable. The sail shaft/blades  118 , e.g., carbon fiber masts, coupled to hub  114  are attached to the sail deployment gear set  116 , and can be rotated to let out or retract the sails  120  which are attached to the sail shaft/blades  118 . In some embodiments, sensors are employed in the blade assembly  102  to detect sail position. By adjusting the amount of exposed sail  120 , the wind velocity band usable for energy production can be expanded over existing systems. At very low wind speed velocities, the sails  120  can be fully unfurled allowing the wind turbine  100  to capture energy at wind velocities below 9 mph, e.g., 4, 5 or 6 miles per hour. At very high wind velocities, the sails  120  can be fully reefed reducing stresses on the blade assembly  102 . Sail shaft/blades  118  are constructed such that when the sails  120  are fully retracted the sail shaft/blades  118  have a mild wing shape capable of capturing high velocity wind energy and capable of withstanding the high velocity winds without structural damage. By incorporating such design features, in accordance with the present invention, the wind turbine  100  is able of capturing wind energy at wind velocities above 25 mph, 30, 35 or even 40 miles per hour. This variable sail area feature in combination with a wing shaped sail shaft/blades  118  allows for a larger wind speed range over existing designs, thus allowing for more energy production over the course of time by allowing for energy production over a larger wind speed range than current designs.  
         [0034]     The main drive housing  104  includes a main drive tube  122 , a pump drive gear set  124 , a hydraulic pump driveshaft  126 , a hydraulic pump  128 , a main drive housing position motor  130 , a sail deployment motor  132 , and a sail deployment driveshaft  134 . One end of the main drive tube  122  is coupled to the hub  114  of blade assembly  102  while at the other end of the main drive tube  122 , a gear  124   a  attached to the main drive tube  122  meshes with a gear  124   b  attached to the hydraulic pump driveshaft  126 . Main drive gear set  124  includes gears  124   a  and  124   b . The main drive tube  122  is supported in the main drive housing  104  by support bearing assemblies. The hydraulic pump driveshaft  126  is coupled to the hydraulic pump  128 . As wind energy is captured by the blade assembly  102 , the sail shaft/blades  118  rotate about the center axis of the hub  114 . As the hub  114  rotates, the main drive tube  122  rotates resulting in rotation of pump drive gear set  124  and rotation of hydraulic pump driveshaft  126 . As the hydraulic pump driveshaft  126  rotates, the hydraulic pump  128  rotates generating hydraulic pressure.  
         [0035]     The main drive tube  122  includes a hollow center core through which sail deployment driveshaft  134  is located. The sail deployment motor  132  is coupled to one end of the sail deployment driveshaft  134 , while the other end of the sail deployment driveshaft is coupled to the sail deployment gear set  116 . In some embodiments, the sail deployment motor  132  is an electric motor, while in other embodiments, the sail deployment motor is a hydraulic motor. The sail deployment motor  132  when controlled to engage and rotate causes the sail deployment driveshaft  134  to rotate, the controlled rotation being transferred via sail deployment gear set  116  such that the sail shaft/blades  118  are rotated and sail  120  is unfurled or retracted as commanded. In other embodiments, sail deployment motor or motors are mounted in the hub  114 , in the sail/shaft blades  118 , and/or attached to the sail/shaft blades  118 .  
         [0036]     Attached to the main drive housing  104  is a wind sensor  136 . The wind sensor  136  detects and measures wind velocity and, in some embodiments, wind direction. In some embodiments, separate sensors are used to detect wind velocity and wind direction. When, the wind speed sensor  136  detects and indicates a lower wind velocity condition, the sail area can be controlled to be increased, when not fully unfurled, by controlling the sail deployment control motor  132  to increase the sail area by controllable unfurling the roller reefed sails. When, the wind speed sensor  136  detects and indicates a higher wind velocity condition, the sail area can be controlled to be decreased, when not fully retracted, by controlling the sail deployment control motor  132  to decrease the sail area by controllable drawing in or reefing the roller reefed sails.  
         [0037]     The main drive housing  104  is mechanically coupled to support tower  106  via a main drive housing/tower interface base  138 . The main drive housing/tower interface base  138  allow the main drive tower  104  to be controllably oriented to different headings so as to capture the prevailing winds and/or to place the blade assembly  102  in a shutdown mode with minimal stress on the blade assembly  102 . The main drive housing positioning motor  130 , e.g., an electric or hydraulic motor, is used to orient the main drive housing  104  heading.  
         [0038]     Support tower  106  includes a high pressure tank  140 , a high pressure tank sensor  142 , and a primer valve  144 . The high pressure tank  140  stores high pressure fluid  146 . In some embodiments, the high pressure tank may also include a bellows assembly. A low pressure feed tube  148  is routed through or adjacent to the high pressure tank  140 . At the bottom of the low pressure feed tube  148  is a low pressure inlet  152  which is situated in the low pressure tank  110  such that low pressure fluid  154  can be drawn into the low pressure feed tube. In some embodiments, an inert gas  155 , e.g., nitrogen, under pressure is included in the low pressure tank  110 , and the pressure of the inert gas aids in forcing the low pressure fluid  154  up the feed tube  148 . At the top of the support tower  106  a hydraulic swivel  150  couples the high pressure low pressure feed tube  148  to the hydraulic pump  128  low pressure inlet port and couples the high pressure output of the hydraulic pump  128  to the high pressure tank  140 . A high pressure outlet  153  discharges high pressure fluid from the hydraulic pump  128  into the high pressure tank  140 .  
         [0039]     The low pressure feed tube  148  includes a check valve  156 . When re-starting the hydraulic pump  128  of the wind turbine  100 , with a sufficient restart level of residual pressure having been intentionally maintained in the high pressure tank  140 , the primer valve  144  is controlled to direct regulated high pressure fluid into the low pressure feed tube  148 . Check valve  156  prevents the pressurized fluid from entering the low pressure tank  110 . The pressurized fluid enters the inlet of the hydraulic pump, which now functions as a hydraulic motor to start the blade assembly  102  spinning. Then, the primer valve  144  is switched to seal off the high pressure chamber  140  form the low pressure feed tube  148 , and the wind energy continues to spin the blade assembly  102  and the hydraulic pump  128  ceases to operate as a hydraulic motor and operates in an energy storage mode of operation increasing the pressure in the high pressure tank  140 .  
         [0040]     The hydraulic motor and generator housing  108  includes a proportioning valve  158 , a regulated output line  160 , a hydraulic motor  162 , a coupling shaft  164 , a generator  166 , and an output switch  168 . The proportioning valve  158  is coupled via a high pressure inlet  170  open to the high pressure tank  140 . The proportioning valve  158  regulates the pressure level to maintain a consistent regulated pressure level, when possible, to drive the hydraulic motor  162  at a consistent speed. The output of the proportioning valve  158  is directed via regulated output line  160  which couples the proportioning valve  158  to an inlet of the hydraulic motor  162 . The hydraulic motor  162  includes a discharge outlet  172  through which lower pressure fluid is discharged into the low pressure tank  110 , stored energy having been extracted from the pressurized fluid when the hydraulic motor  162  was driven. The hydraulic motor  162  is coupled to generator  166  via coupling shaft  164 , which in turn spins the generator  166  to produce electrical power. By spinning the hydraulic motor  162  at a constant controlled speed, the generator  166  is in turn spun at a constant controlled speed thus controlling and maintaining the frequency of the generated electric signal to be compatible with the power grid. The output of the generator  166 , e.g., 3 phase output lines, is coupled to the input of output switch  168 . The output of output switch  168  is coupled to the power grid and/or storage devices. The output switch  168  can be controlled to disconnect the generator from the power grid such that start-up and shut-down of the hydraulic motor and/or generator, during which the generator is being spun at a frequency outside the acceptable tolerances, does not introduce problematic signals into the power grid. In addition, the output switch  168  can be used to cut out the generator output, before the hydraulic motor  162  is turned off due to insufficient high pressure in the high pressure tank  140 , and to reconnect the generator output to the power grid after start up has stabilized.  
         [0041]     Low pressure tank  110  stores the low pressure fluid  154 . The low pressure tank  110  also includes a low pressure tank sensor  155  which measures the pressure and/or fluid level in the low pressure tank  110 . In some embodiments, the low pressure tank  110  also includes a bellows or float assembly.  
         [0042]     Computer control module  112  includes interfaces to other networks, interfaces to sensors, and interfaces to control devices. Computer control module  112  includes a processor and memory. The memory includes routines and data/information. The processor, e.g., a CPU, executes the routines and uses the data/information in memory to control the operation of the wind turbine system  100  and implement the methods of the present invention. Various functions controlled by the computer control module  112  include wind measurements, blade assembly start-up operations, sail deployment control, main drive housing positioning control, pressure regulation control, primer valve operation, proportioning valve control, generator output monitoring, generator output switching, and signaling a management network of changing conditions. Various signals received by the computer control module  112  include wind sensor output signal  174 , low pressure tank sensor output signal  176 , high pressure tank sensor output signal  178  and generator output monitor signal  180 . Other signals received by the computer control module  112  may include position indicator signals indicative of the sail deployment level and position indicator signals indicative of the direction of the main drive housing  104 . Fault indication signals may also be received and processed by the computer control module  112 . Various output signals generated by the computer control module  112  used to control operation of the wind turbine system  100  include said deployment control signal  182 , housing direction positioning control signal  184 , proportioning valve control signal  186 , primer valve control signal  188 , and output switch module control signal  190 . The computer control module  112  also interfaces with a management network via signals over the control line to management network  192 , both receiving commands, e.g., take wind turbine off-line, and sending notifications, e.g., wind-turbine to be taken off-line at a specified time.  
         [0043]     Slip ring are provides at the main drive housing  104 /main drive housing/tower interface base  138 .  
         [0044]     Wind measurements from sensor  136  can be performed, processed, and used by the computer control module  112  to predict how long operations can continue before insufficient wind energy input to keep up with output demand will force an energy output shutdown, and a cutoff of the generator output. Based on pressure measurements of high pressure sensor output signal  120 , the computer control module can predict the remaining energy capacity. The computer control module  112  can notify the management network via control line  192  of conditions and give advance notice before stopping energy output to the grid.  
         [0045]      FIG. 2  is a functional drawing  200  used to describe operations and flow in the wind turbine system  100 . Functional drawing  200  includes low pressure tank  110 , high pressure tank  140 , low pressure feed tube  148 , hydraulic pump  128 , primer valve  144 , check valve  156 , electronic proportioning valve  158 , hydraulic motor  162 , regulated pressure line  160 , return line  172 , drive coupling  164 , generator  166  and storage device  202 . Storage device  202  may include, e.g., invertors, filters and a bank of storage batteries.  FIG. 2  illustrates operation of exemplary wind turbine system  100  during conditions where the blade assembly  102 , which is capturing wind energy, is driving the pump  128 , and there is sufficient stored energy in the high pressure tank  140  to drive the hydraulic motor  162  in accordance with the present invention.  
         [0046]     The pump  128 , driven by wind power captured by blade assembly  102 , turns siphoning low pressure fluid  154  from low pressure tank  110  and generating hydraulic pressure. Low pressure fluid  154  is drawn up through the low pressure feed tube  148  through the check valve  156 , which is open, and into the low pressure side of pump  128 . Under these described operating conditions, primer valve  144  is controlled to be closed under the direction of the computer control module  112  via control signal  188 . The pump  128  pressurizes the fluid with the high pressure side of the pump coupled to the high pressure tank  140 .  
         [0047]     The electronic proportioning valve  158  is controlled under the direction of the computer control module  112  via control signal  186  to regulate the pressure to the hydraulic motor  162  such that the hydraulic motor  162  will continue to spin at a controlled determined rotational rate. In some embodiments, a sensor may also be included to monitor the rate of rotation of the drive coupling  164  and to forward such information to the computer control module  112  to be used in closed loop control operations. High pressure fluid  146  enters the electronic proportioning valve  158 , is regulated to become a regulated pressure fluid in line  160 , the fluid then passes through hydraulic motor  162  spinning drive coupling  164  to drive the generator at a controlled rotational rate. This results in generator  166  producing electric energy at a constant frequency, e.g., 60 Hz or 50 Hz, which is output to the power grid and/or storage device  202 . Discharge fluid from hydraulic motor  162  is returned to the low pressure tank  110  via return line  172 .  
         [0048]     If the pump  128  is producing more energy than consumed by hydraulic motor  162 , e.g., due to favorable wind conditions, the pressure in high pressure tank can be allowed to increase within the safety margins of the high pressure tank  140 , thus storing the excess energy for use later. If the pump  128  is producing less energy than currently consumed by hydraulic motor  162 , then the pressure in high pressure tank  140  will decrease.  
         [0049]     In accordance with one feature of various embodiments of the present invention, the pressure in the high pressure tank  140  is maintained to at least a minimal value needed to restart the hydraulic pump  128  after the blade assembly  102  has stopped. The electronic proportioning valve  158  under the direction of the control module  112  via control signal  186  shuts off flow to the hydraulic motor  162  before this minimal restart pressure level threshold is crossed.  
         [0050]      FIG. 3  is a functional drawing  300  used to describe operations and flow in the wind turbine system  100 . Functional drawing  300  includes low pressure tank  110 , high pressure tank  140 , low pressure feed tube  148 , hydraulic pump  128 , primer valve  144 , check valve  156 , electronic proportioning valve  158 , hydraulic motor  162 , regulated pressure line  160 , return line  172 , drive coupling  164 , generator  166 , storage device  202  and check valve  302 .  FIG. 3  illustrates operation of exemplary wind turbine system  100  during conditions where the blade assembly  102  has stopped rotating and is no longer capturing wind energy; however, the high pressure tank has sufficient energy stored above the minimum level needed for a restart such that hydraulic motor  162  operation and generator  166  operation can continue. Hydraulic pump  128  is not rotating. Check valves  156  and  302  are closed, and primer valve  144  is also closed. The electronic proportioning valve  158  under the control of the computer control module  112  via control signal  186  continues to allow flow.  
         [0051]     High pressure fluid  146  enters the electronic proportioning valve  158 , is regulated to become a regulated pressure fluid in line  160 , the fluid then passes through hydraulic motor  162  spinning drive coupling  164  to drive the generator at a controlled rotational rate. This results in generator  166  producing electric energy at a constant frequency, e.g., 60 Hz or 50 Hz, which is output to the power grid and/or storage device  202 . Discharge fluid from hydraulic motor  162  is returned to the low pressure tank  110  via return line  172 . During this mode of operation, the pressure level of the high pressure fluid gradually decreases. At a certain level, above the minimum pressure needed for a restart, the electronic proportioning valve is controlled via control signal  186  to stop flow through the hydraulic motor  162  and thus retain the pressure level in the high pressure tank.  
         [0052]      FIG. 4  is a functional drawing  400  used to describe operations and flow in the wind turbine system  100 . Functional drawing  400  includes low pressure tank  110 , high pressure tank  140 , low pressure feed tube  148 , hydraulic pump  128 , primer valve  144 , check valve  156 , electronic proportioning valve  158 , hydraulic motor  162 , regulated pressure line  160 , return line  172 , drive coupling  164 , generator  166 , storage device  202  and check valve  302 .  FIG. 4  illustrates operation of exemplary wind turbine system  100  during a restart operation of the blade assembly  102 . Initially hydraulic pump  128  is not rotating. Primer valve  144  is controlled by the computer control module  112  via control signal  188  to open allowing high pressure fluid or some regulated level thereof to enter the low pressure feed tube  148 . Check valve  156  is closed preventing the high pressure fluid from entering the low pressure tank  110 . The high pressure fluid which passed through the primer valve  144  enters the inlet side of the pump  128 , which at this time is functioning as a hydraulic motor. The pressure on the inlet side of the pump  128 , causes the pump  128  to start to rotate, which in turn rotates the blade assembly  102 , to which the pump  128  is mechanically connected. Having started the blade assembly  102  rotating, wind energy continues to keep the blade assembly  102  rotating. The primer valve  144  is controlled via control signal  188  to shut, and the hydraulic pump continues to rotate under wind energy with the pump  128  drawing low pressure fluid  154  through check valve  156 , which now opens, pressurizing the fluid, and the high pressure fluid exits into the high pressure tank  140  through check valve  302 , which now opens. The hydraulic pump  128 , operating now under wind energy, continues to pump, increasing the pressure in high pressure tank  140 . At some detected high pressure level, the computer control module  112  determines that pressure is sufficiently high for the hydraulic motor  162  to resume operations. The electronic proportioning valve  158  is controlled via signal  186  to open and send regulated pressure to the hydraulic motor  162 . Once stabilized rotational operation has been achieved, the generator&#39;s output can be switched on to reconnect with the power grid/storage device  202 .  
         [0053]      FIG. 5  is a drawing illustrating components in an exemplary blade assembly  500  in accordance with the present invention. Exemplary blade assembly  500  may be blade assembly  102  of the exemplary wind turbine  100  of  FIG. 1 . Center hub  502  may be hub  114  including sail deployment gear set  116 , while mast  504  and boom  506  may be sail/shaft blade  118 , and sail  508  may be sail  120  of  FIG. 1 . Blade assembly  500  includes a plurality, e.g., four, sets of a mast  504 , a boom  506 , and a sail  508 . Mast  504  includes an internal mast shaft  510 , and boom  506  includes internal boom shaft  512 . For a given set of mast  504 , boom  506 , and sail  508 , the construction is such that the sail  508  can be rolled around one of the internal mast shaft  510  and the internal boom shaft  512 , with the sail  508  being slid along the other shaft when the sail is being unfurled or reefed in. Sails  508  are constructed of flexible sail material that can be rolled up on a shaft, e.g., a boom internal shaft  512  or a mast internal shaft  510 . Some masts  504  and/or booms  506  include slots into which the sail  508  can be retracted when being rolled up. Some masts  504  and/or booms  506  include slots along which the sail  508  or sail anchor slides when being unfurled or reefed in. In some embodiments, each sail  508  is rolled up/out along one of the shafts, e.g., a boom shaft  512 , and pulled down/up the other shaft, e.g., a mast shaft  510 . In some embodiments, some of the sails  508  are rolled up/out along internal mast shafts  510  and some of the sails  508  are rolled up/out along internal boom shafts  512 .  
         [0054]      FIG. 5  illustrates the condition where the sails  508  have been fully unfurled.  
         [0055]      FIG. 6  is a drawing  600  illustrating the exemplary blade assembly of  FIG. 5  except showing the sails in a partially reefed in position.  
         [0056]      FIG. 7  is a drawing  700  illustrating an exemplary mast or boom/inner shaft/sail structure in accordance with some embodiments of the present invention. Mast or boom  704  includes an inner shaft  706  upon which sail  702  may be rolled in or let out. In some embodiments, the mast and/or boom  704  has a wing shape allowing the wind turbine to capture wind energy even when the sail is completely reefed in. The mast or boom  704  may be mast  504  or boom  506  of  FIG. 5 ; inner shaft  706  may be internal mast shaft  510  or internal boom shaft  512  of  FIG. 5 ; sail  702  maybe sail  508  of  FIG. 5 .  
         [0057]      FIG. 10  is a drawing illustrating an exemplary mast or boom/inner shaft/sail structure  1000  in accordance with various embodiments of the present invention. Exemplary structure  1000  includes a mast or boom  1002 , inner shaft  1004 , slotted guide/bearing  1006 , collar assembly  1008 , sail securing ring  1016 , and sail  1018 . Inner shaft  1004  includes a threaded outer portion  1010 . Collar assembly  1008  includes a threaded inner portion  1012 , and a sail attachment portion  1014 . The threaded outer portion of the inner shaft  1010  meshes with the threaded inner portion of the collar assembly  1012 . The collar assembly is restricted to the slotted guide/bearing  1006  of the mast or boom  1002 . As the inner shaft  1004  rotates as part of the sail deployment operations, the collar assembly moves along the shaft  1004 . The sail  1018  is attached to the sail securing ring  1016 ; the sail securing ring is attached to the sail attachment portion of the collar assembly  1014 . As the collar assembly  1014  moves along the inner shaft  1004 , the end of the sail is dragged along.  
         [0058]      FIG. 11  is a drawing  1100  showing some components included in the exemplary structure  1000  of  FIG. 10  from a different perspective. Sail  1018  is shown in a partially reefed in state.  
         [0059]      FIG. 8  is a drawing of a head on view of an exemplary hub assembly  800  in accordance with the present invention. Hub assembly  800  may be used in the wind turbine system  100  of  FIG. 1 . Hub assembly  800  includes hub  802 , a sail deployment driveshaft/mast shaft gear  812 , four mast shaft drive gears  814 , four mast shaft/boom shaft gears  816  and four boom shaft drive gears  818 . Masts  804  and booms  806  are attached to the hub  802  via supports  820 ,  822 , respectively. The sail deployment driveshaft  824  is attached to the sail deployment/mast shaft gear  812 . As gear  812  rotates, the four mast shaft drive gears  814  are rotated turning the mast shafts  808  to unfurl or reef in the sail. In addition, as the mast shafts rotate, the mast shaft/boom shaft gears  816  are rotated. Gears  816  mesh with boom shaft gears  818 ; therefore the boom shaft  810  is also rotated in coordination with the rotations of the mast shaft to perform a controlled sail unfurling or sail reefing in operation.  
         [0060]      FIG. 9  is a drawing  900  illustrating an energy storage feature in accordance with some embodiments of the present invention. Wind turbine tower structure  902  includes a high energy capacitor or bank of capacitors  904 . The capacitor(s)  904  are electrically coupled to interface circuit  906 . Interface circuit  906  may include switching, filtering, and/or conversion circuitry and may be operated under the direction of a computer control module in the wind turbine system, e.g., module  112  of the exemplary system of  FIG. 1 . The interface circuit  906  is also coupled to the wind turbine generator output  908  and the power grid and/or loads  910 . Under conditions where the wind turbine generator output energy generation exceeds electrical energy load requirements, the additional energy may be stored in the high energy capacitor(s)  904 . Under conditions where the wind turbine generator energy output is below electrical load requirements or the generator output is zero, then stored energy can be extracted from the capacitors  904  and supplied to the loads.  
         [0061]     In some embodiments, hydraulic fluid is displaced in the tower structure for the high energy capacitor or capacitors  904 . The high energy capacitor  904 , is, e.g., a carbon nanotube capacitor with energy storage densities of 30 kilo-watts per kilogram. The high energy capacitor  904  is, in some embodiments, incorporated into the fluid bath or collocated with the tower. This additional energy storage capacity provided by the high energy capacitor  904 , in addition to the energy stored in the high pressure fluid in the high pressure tank, can significantly enhances on-site energy storage capabilities for a wind turbine system in accordance with some embodiments of the present invention. For example, a 30 kilo-watt hour per kilogram carbon nanotube capacitor weighing ten thousand pounds could be charged up during high energy output periods to give a 4 Mega-Watt wind generator system 34 hours of extended output when the generator is unable to produce energy. This energy storage enhancement capability would smooth the energy curve and improve the efficiency of a wind turbine system thus allowing for a larger amount of energy to be sent over the grid to users over time.  
         [0062]     While control of sail deployment has been described using a mechanical drive mechanism, an electrical motor driven approach could be used to control sail material deployment and retraction. In one such embodiment, an electrical motor, controlled by electrical signals generated under control of the computer control system as a function of wind velocity, is used to drive the sail deployment in each blade. In one such system, one electrical motor is mounted near the center of the rotor assembly for each blade and used control the deployment of the sail for that blade. Normally, two motors corresponding to blades mounted opposite each other are controlled to cause uniform deployment of sail material and to maintain blade balance.  
         [0063]     In various embodiments elements described herein are implemented using one or more modules to perform the steps corresponding to one or more methods of the present invention. Thus, in some embodiments various features of the present invention are implemented using modules. Such modules may be implemented using software, hardware or a combination of software and hardware. Many of the above described methods or method steps can be implemented using machine executable instructions, such as software, included in a machine readable medium such as a memory device, e.g., RAM, floppy disk, etc. to control a machine, e.g., general purpose computer with or without additional hardware, to implement all or portions of the above described methods, e.g., in one or more nodes. Accordingly, among other things, the present invention is directed to a machine-readable medium including machine executable instructions for causing a machine, e.g., processor and associated hardware which may be part of a test device, to perform one or more of the steps of the above-described method(s).  
         [0064]     Numerous additional variations on the methods and apparatus of the present invention described above will be apparent to those skilled in the art in view of the above description of the invention. Such variations are to be considered within the scope of the invention.