Patent Publication Number: US-2010117372-A1

Title: Hybrid Wind Turbine

Description:
RELATED APPLICATIONS 
     This application (Attorney Matter No. P216290) is a continuation in-part of U.S. patent application Ser. No. 12/022,958 filed Jan. 30, 2008, now U.S. Pat. No. 7,615,884 issued Nov. 10, 2009. 
     U.S. patent application Ser. No. 12/022,958 claims priority of U.S. Provisional Application Ser. No. 60/898,619 filed Jan. 30, 2007. 
     The contents of all related application listed above are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates in general to wind turbine technology, and more particularly to a system combining the apparatus and method of the wind turbine with other energy sources. 
     BACKGROUND 
     While wind turbine power has many advantages as an additional and/or alternative source of energy, it does have the drawback that there are time intervals where it is not able to produce any power at all, or only a small amount of power. Thus, there have been various approaches to combine the wind power source with other independent power sources to be able to produce power more reliably, in the form of “firm power”. 
     A search of the patent literature has disclosed patents related to solving these problems, and these are summarized in the following text. 
     U.S. Pat. No. 4,204,126 (Diggs) discloses a “Guided Flow Wind Power Machine With Tubular Fans”, which, when powered by the wind, can generate electricity. Also, when there is enough wind power it has the capability of also lifting “massive weights” hydraulically. Then when the wind has subsided, the weights can be permitted to be drop downwardly to supply energy to drive a generator.  FIGS. 4 and 5  show the weights  114  through  120  arranged in quadrants. 
     U.S. Pat. No. 5,740,677 (Vestesen) shows a system which is adapted to for use at a location where there is a need for electricity and also fresh water. However, this residential community is also near a source of salt water. There is a wind diesel plant which supplies electricity for various uses and also operates a distillation unit to supply the fresh water. The wind/diesel plant comprises at least an internal combustion engine, a wind turbine, a distillation unit, a first closed fluid circuit containing heating and cooling devices, and a second open fluid circuit. 
     U.S. Pat. No. 6,127,739 (Appa) issued Oct. 3, 2000, and is the first of three patents which have the same inventor. In this patent, there is a forward front rotor  12  having blades that would cause rotation in one direction, then there is a rear rotor  21  (called a “leeward rotor  21 ”) positioned behind the front rotor  12  and rotating in the opposite direction. This patent states that the various items added to this apparatus would produce a substantially higher “value of energy efficiency factor”. 
     U.S. Pat. No. 6,278,197 (Appa) is the second patent to the inventor and it discloses a wind turbine where there is a forward set of turbine blades which rotate in one direction, and a second set of turbine blades which are in the wake of the first set and which rotate in the opposite direction. The reason given for this is that there is still energy in the air that passes through the first set of turbine blades, and this is utilized in the second set of turbine blades. 
     U.S. Pat. No. 6,492,743 B1 (Appa) is the third (and more recent) patent to Mr. Appa, and this also shows a basic configuration of wind turbine where there are forward and rear sets of blades. There is a heat exchanger having a centrifugal fan to circulate ambient air to cool an alternator in the apparatus, and the hot air is directed to a combustion chamber by means of an air duct in the blades. Natural gas or liquid is also conveyed to the rotating frame. When wind speed is low, fuel will be injected into the combustion chamber and burned with a large mass of air. The hot gasses expand in an exit nozzle to provide thrust to assist wind power. 
     SUMMARY 
     The present invention may be embodied as a thermal energy system comprising a primary thermal energy system, a solar thermal energy system, a burner, and a heat recovery system. The solar thermal energy system comprises a pipe for absorbing heat from solar rays. The burner is arranged such that the pipe of the solar thermal energy system is capable of absorbing heat from the burner. The heat recovery system uses thermal energy from at least one of the primary and solar thermal energy sources. 
     The present invention may also be embodied as a method comprising the following steps. A primary thermal energy system is provided. A solar thermal energy system comprising a pipe for absorbing heat from solar rays is provided. A burner is arranged such that, when the burner generate heats, the pipe of the solar energy system absorbs heat generated by the burner. Thermal energy from at least one of the primary and solar thermal energy sources is recovered. 
     The present invention may also be embodied as a hybrid wind turbine comprising blades supported on a hub, a generator, an engine, a solar thermal energy system, and a heat recovery system. The generator is operatively connected to the hub such that rotation of the blades operates the generator. The engine is operatively connected to the generator such that operation of the motor operates the generator. The heat recovery system uses exhaust heat from the generator and heat collected by the solar thermal energy system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an elevation view of a hybrid wind turbine system of a first embodiment of the present invention; 
         FIG. 2  is an isometric exploded view showing the components of a typical wind turbine apparatus, some or all of which can be combined with the wind turbine apparatus of the embodiments of the present invention; 
         FIG. 3  is a somewhat schematic view of a power generating section  16  of the first embodiment; 
         FIGS. 4 ,  4 A and  4 B are views similar to  FIG. 3  showing a second embodiment illustrating alternate locations for the auxiliary drives; 
         FIGS. 5 and 5A  are views similar to  FIGS. 1 and 3 , showing a third embodiment which shows a heat recovery section in the support tower; 
         FIG. 6  shows yet a fourth embodiment of the invention, where a steam generator and steam turbine are utilized as the auxiliary power source; 
         FIGS. 7 and 7A  are views that show a basic wind turbine system which also utilizes solar energy to add energy to the system; 
         FIG. 8  is similar to  FIG. 7  in that it shows a basic wind turbine system which also utilizes an engine auxiliary drive with heat recovery and an associated steam turbine auxiliary drive; 
         FIG. 9  shows a system for a solar thermal energy system which is independent of the wind turbine power generation system but occupies the same wind turbine structure; 
         FIG. 10  is a combination of  FIGS. 7 and 8  in that it shows a basic wind turbine energy system which utilizes an engine auxiliary drive with heat recovery, an associated steam turbine auxiliary drive, and a solar thermal energy system which uses the same steam turbine; 
         FIG. 11  shows a basic wind turbine system with the addition of the nacelle substructure for housing additional heat recovery and power generation equipment; 
         FIG. 12  is a somewhat schematic, elevation view of a hybrid wind turbine system of a tenth example of the present invention; 
         FIG. 13  is a somewhat schematic, elevation view of a hybrid wind turbine system of an eleventh example of the present invention; 
         FIG. 14  is an elevation view of a hybrid wind turbine system of a twelfth example of the present invention; 
         FIG. 15  is a section view of an absorber portion of the hybrid wind turbine system of  FIG. 14 ; 
         FIG. 16  is a longitudinal section view of the absorber portion of the hybrid wind of  FIG. 14 ; 
         FIG. 17  is a schematic drawing of an example heat exchange system that may be used by the system of  FIG. 14 ; and 
         FIG. 18  is a schematic drawing of an example heat exchange system that may be used by the system of  FIG. 14 . 
     
    
    
     DETAILED DESCRIPTION 
     It is believed that a clearer understanding of the present invention can be obtained by first reviewing briefly the overall system of a first example of the present invention, as shown in  FIG. 1 . The discussion of the overall system of the first example will be followed by a more detailed description of a group of components shown in  FIG. 2 , which are typically found in related wind turbine apparatus, and some or all of which can be incorporated in one or more of the examples of the present invention described herein. The discussion of the related wind turbine components will then be followed by a more detailed description of a number of examples of systems incorporating the principles of the present invention. 
     A. General Description of First Example 
     To proceed now with the more general description of the first example, as indicated above, this will be done with reference to  FIG. 1 . There is a wind turbine assembly  10  which comprises a base support section comprising a vertically aligned tower  11  which is supported by a base  12 . At the upper end of the tower  11 , there is a power generating main support structure  13  which is rotatably mounted to the tower  11  to rotate about a vertical axis of rotation  14  centrally located in the tower  11 . This support section  13  provides a support for a power generating section  16  of the first example, and it may be in the configuration of a nacelle  13  commonly used with wind turbines. 
     The entire power generating section  16  comprises a blade section  18 , a rotary speed changing drive section  20 , a generator section  22 , and an auxiliary power section  24 . The blade section  18  comprises a plurality of turbine blades  28 , and a hub or rotor  30  to which the blades  18  are connected. 
     The blade section  18  and the speed changing drive section  20  can be grouped as the primary power generating portion while the auxiliary power section  24  (as well as the auxiliary power or back up power components, including those that are shown in other examples) can be considered as being in a secondary power generating portion. 
     The primary and secondary power generating portions together function in a manner to enable the generator  22  to provide firm power. 
     B. Summary of Related Components 
     With the overall description of this first example being presented, attention is now directed to  FIG. 2 , which, as indicated above, is an exploded drawing of a number of components which in themselves exist in the prior art and are commonly used in present day wind turbines. In  FIG. 2  only two of the three blades  28  are shown and the rotor  30  is not shown. There is a low speed shaft  32 , which (as shown in  FIG. 3 ) connects to a speed changing drive section  34  which is shown somewhat schematically, and (as its name implies) provided a power output at a higher RPM than that of the shaft  32 . 
     This drive section  34  is commonly in the form of a gear section. In general, the rotational speed of the low speed shaft  32  would be between about 30 to 60 rotations per minute, and the gear section  34  is in turn connected to the generator  22  to cause it to rotate at a speed between about 1,200 to 3,600 RPM. This would typically be a rotational speed required by a large number of present day generators to produce electricity. The gear section  34  connects to a shaft  38  which is located in the generator  22 . 
     There is provided an anemometer  40  which measures the wind speed, and also a wind vane  42  to ascertain wind direction. Both the wind speed and the wind direction data are transmitted to a controller  44 . The controller  44 , as its name implies, performs various control functions. For example, it controls a yaw drive  46  and its associated motor  48  to keep the blade section  18  facing into the wind as the wind direction changes, starts and stops the wind turbine, etc. There is also provided a disc brake  49  for the low speed shaft  32 , and in the prior art this can be applied mechanically, electrically, or hydraulically to stop the rotation of the rotary components in emergencies. 
     All, or most all, of the components which are shown in  FIG. 2  are, or may be, present in the examples of the present invention. However, for convenience of illustration (e.g., to avoid cluttering up the drawings), these are not shown in the following drawings ( FIGS. 3-11 ) which illustrate a number of examples of the present invention. 
     C. First Example 
     All (or many) of the components of this first example are shown in at least one of  FIGS. 1 ,  2  and  3 . Reference is now made to  FIG. 3 . It will be noted that a number of the components which appear in  FIG. 3  also appear in either  FIG. 1  or  2 . For clarification, those components in  FIG. 3  which already appear in either or both of  FIGS. 1 and 2 , are given like numerical designations, with an “a” suffix distinguishing those particular components. Then the components which appear in  FIG. 3  and which do not appear in either  FIG. 1  or  2  will be given new numerical designations. 
     To proceed now with a description of the first example of  FIG. 3 , as in  FIG. 1 , there are the blades  28   a  which are attached to the hub  30   a . The hub  30   a  in turn connects to and drives the low speed shaft  32   a . The low speed shaft  32   a  in turn drives the speed changing drive section  20   a  which then provides a high rotational speed power output to the generator  22   a.    
     The components of this first example described in the paragraph immediately above, are already found in  FIG. 1  or  2 . In  FIG. 3  there is also shown an auxiliary drive section  24   a  capable of providing a drive output to the generator  22   a.    
     For convenience of description, in describing the location of the components in  FIG. 3 , the hub  30   a  shall be considered to be a front or forward location, and the location of the auxiliary drive unit  24   a  shall be considered as having a rear location. Also, the axis of rotation of the hub  30   a , the blades  28   a , and also of the low speed shaft  32   a , and any other components which rotate on the same axis, shall be designated the “power generating axis of rotation  67 ”. 
     To return now to the description of this first example, the auxiliary drive unit  24   a  provides a rotating drive output to a torque converter  66 . The torque converter  66  in turn has a drive connection to an overrunning drive member  68  (which can be simply an overrunning drive clutch) that in turn connects to the rear end of the high speed shaft  38   a  of the generator  22   a . Then the forward end of the shaft  38   a  of the generator  22   a  connects to a forward overrunning drive member  69  that connects to the drive output of the speed changing drive section  34   a . The torque converter  66  located between the auxiliary drive unit  24   a  and the generator  22   a  may or may not be required and depends on the design speed of the generator  22   a  and the auxiliary drive unit  24   a . If the operating speed of the auxiliary drive unit  24   a  is a close match to the generator  22   a  operating speed, the overrunning clutch  68  would provide an adequate method of coupling the generator  22   a  to the auxiliary drive unit  24   a.    
     There are many types of conventional drives that could function as the auxiliary drive unit  24   a . For example, this could include an internal combustion engine, external combustion engine, steam turbine, steam engine, or hybrid drive. The most common types of drives would include, but not be limited to, gasoline engines, diesel engines, natural gas engines, gas turbine engines, steam turbines, steam engines, sterling engines, gas expanders, or hydraulic or electric motors with a nearby source of power or hydraulic energy. Sources of energy for the auxiliary drive unit  24   a  could include gasoline, diesel, jet fuel, heavy oil, natural gas, propane, hydrogen, ethanol, coal, wood, or any other energy source suitable for the auxiliary drive or its cooperating equipment. 
     D. Operation of First Example 
     To describe now the operating features of this first example, let us review three different situations, namely: i. the wind is at a sufficient velocity so that it is able to generate sufficient power to produce the desired power output of the generator  22   a ; ii. the wind velocity is not sufficient to drive the blade section at all, and the auxiliary drive section  24   a  is activated to generate the needed electric power; and iii. the wind velocity is such that it is able to rotate the blade section  18   a  to generate only an electrical power output which is below the desired output of the generator  22   a , and to obtain the desired level of the total electrical power output, it is necessary to operate the auxiliary drive section  24   a.    
     In the first situation (where the wind power is at a sufficiently high level), the blade section  18   a  is rotated to drive the blade sections  18   a  at full power output or near full power output. More specifically, the blade section  18   a  is rotating with sufficient power output so that the speed augmenting drive section  20   a  is acting through an overrunning clutch  69  to drive the generator  22   a  at a sufficient power output so that sufficient electrical power is developed. The overrunning drive section  68 , which connects to the shaft  38   a  of the generator  22   a , simply overruns its connection to the auxiliary drive section  24   a , thus, the auxiliary drive section  24   a  remains stationary. 
     Let us now take the second situation where there is either no wind or such a small velocity of the wind that the blade section  18   a  is put in a position where it is stationary or simply not rotating. In this situation, the auxiliary drive section  24   a  is activated manually or automatically so that its rotational output is directed through the torque converter  66 , which in turn acts through the overrunning drive  68 , which is caused to rotate in a direction so that it drives the generator  22   a.    
     At the same time, the speed changing drive section  20   a  remains stationary, and since the connection between the drive section  20   a  and the generator  22   a  is the overrunning drive member  69 , the generator  22   a  is able to operate to rotate in a manner so that it has no drive connection with the drive section  20   a  and is driven totally by the auxiliary power unit  24   a.    
     Let us now consider the third situation, which is that the wind generated power is great enough to achieve a useful lower power output level, but is not great enough to meet the desired power output. In this instance, the auxiliary drive section  24   a  would be utilized to cause rotation of its torque converter  66  to act through its drive member  68  and provide power to the rear end of the shaft  38   a  of the generator  22   a.    
     At the same time, the pitch of the blades  28   a  could be set at an angle of attack to optimize the power output that is developed by the use of both power sources. The effect of this is that the shaft  38   a  of the generator  22   a  would be driven at both its front and rear end portions, so that there would be sufficient power to generate the desired electrical power output. 
     Also, in this third operating mode, the two overrunning drive members (drive clutches)  68  and  69  are operating in their engaged position, so that these are providing rotational forces to the generator  22   a  at a sufficiently high power output. 
     E. Applications of First Example 
     Let us now turn our attention to some of the possible applications of the system of the first example of the invention (i.e., the various ways it might be used). As indicated earlier in this text, one of the drawbacks of a wind turbine is that it produces power intermittently. Thus, this puts wind power in the category of “non-firm energy producers”. However, by combining the wind power turbine in the combination of this first example, this now becomes a source of firm power that could supply energy to a power grid on a continuous basis. 
     Another situation of possible use is where there is a municipality which needs a reliable source of electricity. With the system of the first example, the system could be engineered so that the auxiliary power source by itself could generate an adequate level of electric power. In that situation, the auxiliary power source would be able to operate as the sole power source in that time interval when the wind turbine power source would be idle. Then as the wind energy was available, the system could be operated in the mode mentioned above as Mode 1 or Mode 2 where the electric power output would be entirely from the wind turbine or as Mode 3, a dual drive mode, where the combined operation of both the wind turbine and the auxiliary power section are utilized to drive the generator  22   a.    
     From the above comments, it becomes apparent that only the one generator  22   a  would be needed in each of the three modes. There are various expenses incurred in providing electric power through a generator, such as the cost of switchgear, transformers, etc. With this arrangement of this example, that extra expense is alleviated by utilizing the same generator for: i) the “only wind power mode”; ii) the “sole auxiliary power mode”; and iii) the “combined wind power/auxiliary power mode”. 
     It is to be understood that all of the components (or a large number of the components) that are shown in  FIG. 2  could be utilized also in each of the several examples of the present invention. 
     i) Generator Types 
     To comment generally on the generator  22   a , wind turbines are supplied with several different types of generators, including induction generators, double fed induction generators (for speed control), variable slip induction generators (for limited changes in speed), synchronous generators (directly and indirectly connected), and DC generators (typically small wind turbines). Most wind turbines in service are standard induction generators which are constant speed machines. Variable speed generators, with the exception of DC generators, can be held at a fairly constant speed with the control system. This is a plus for the operation of the auxiliary drive in that the additional energy input to the generator does not change the generator speed appreciably. Additional torque input to the generator simply causes more power output from the generator. The DC generator is not considered an ideal candidate for the auxiliary drive as too much torque from the auxiliary drive could speed up the wind turbine to the point where the wind would not contribute to energy production. 
     ii) Auxiliary Drive Considerations 
     To comment generally about the different possibilities of the auxiliary drive  24   a , it could be coupled directly to the generator via a torque converter or overrunning clutch or it can be connected through a gearbox, again using a torque converter or overrunning clutch. In most cases, an overrunning clutch will be sufficient; however, if there is a need to run the engine at constant speed and vary the output shaft speed to the generator, a torque converter can be used. If the wind turbine is at rest (zero speed) and the operator wishes to run the generator, he can start the auxiliary drive  24   a . Because the generator is at rest, the overrunning clutch will engage the generator as soon as the auxiliary drive commences startup. The generator rotor will rotate along with the auxiliary drive shaft during startup and will continue to rotate at the same speed as the auxiliary drive at all times. 
     To connect the generator to the grid, the auxiliary drive must speed the generator rotor up to a speed that matches the generator rotating magnetic field. At that point the generator breaker can be closed to connect the generator to the grid. Any additional power input from the auxiliary drive to the is generator will cause power to flow out of the generator to the grid. An alternate method of starting up the generator would be to use the soft start feature supplied with most large scale wind turbines to connect them to the grid. In this case the wind must be used to rotate the propeller, gear, and generator to get it close to the normal operating speed before closing the breaker. In some cases the soft start feature can be used to start the generator from dead stop. In this case, the generator acts as a motor until it gets up to speed at which time the wind energy input causes power to flow out from the generator. 
     If the auxiliary drive had a torque converter, the operator could start the auxiliary drive and run it up to operating speed before engaging the torque converter to spin up the generator. With the torque converter the engine speed could be changed and the output shaft speed from the torque converter could be held at a constant speed or, conversely, the engine speed could be kept constant and the output speed could be varied along with the generator speed. 
     The generator can be driven from the wind turbine end, the auxiliary drive end, or both ends at the same time. The generator will not know the difference. It only knows that torque is being applied to its rotor to generate electricity. It would be possible to use the auxiliary drive to reduce the impact of wind gusts on the wind turbine. This could be done by applying a certain amount of power from the auxiliary drive which is over and above the power being supplied to the generator from the wind. In this case the wind turbine would not be supplying full rated power to the generator. When a wind gust hits the wind turbine and increases the generator output and causes high loads on the gearbox, the auxiliary drive would receive a governor signal to reduce its power output so the generator and gear do not experience damaging load increases. Wind turbine manufacturers are constantly working on improvements to minimize the damaging effects of wind gusts and would welcome new solutions to the problem. The current methods to control the effect of wind gusts are associated with the electrical control systems and generators. Variable slip generators are used to help solve the wind gust problem by allowing the generator to temporarily speed up (increased generator slip) to allow the additional wind energy to be converted into kinetic energy and not forcing the energy through the generator. It would be like installing a clutch between the wind turbine propeller shaft and gearbox to allow the clutch to slip during wind gusts to avoid damage to the gears. 
     iii) Structural Considerations 
     An additional benefit of the auxiliary drive arrangement is to change the center of gravity of the nacelle. The auxiliary drive acts as a counterweight on the opposite end of the nacelle as the propeller, hub, shaft and gearbox. Due to the extreme weight of those components, the wind turbine nacelle must be positioned to keep its center of gravity above the center of the tower. This means the propeller is positioned quite close to the tower which causes the propeller blades to bend every time they pass by the wind turbine support tower. The wind shadow and flexing of propeller blades has caused fatigue failures of blades in the past. The weight of the auxiliary drive on the opposite end of the nacelle would allow the nacelle to be repositioned so that the propeller blades are farther away from the tower and less susceptible to flexing and fatigue failures. 
     F. Second Example 
     Reference will now be made to  FIGS. 4 ,  4 A and  4 B which are different configurations of this second example. 
     The second example is similar to the first example except that some of the auxiliary drive components are placed in different relative positions, and an auxiliary drive speed changing section is added in  FIGS. 4A and 4B  to allow the installation of two auxiliary drives. An example of the foregoing would be the installation of a natural gas engine as an auxiliary drive and a steam turbine as the second auxiliary drive. The second auxiliary drive would be part of an energy recovery system that would recover waste heat from the first auxiliary drive and convert the waste heat into steam. The steam would then be used as an energy input to the second auxiliary drive. Another example of a use for a second auxiliary drive would be a solar/wind hybrid wind turbine shown in  FIG. 7  where steam generated in the solar collector is routed to the second auxiliary drive (steam turbine) to provide additional power to the generator. 
     Components of this second example which are the same as, or similar to, components shown in  FIGS. 1 ,  2  and  3 , will be given like designations with a “b” suffix distinguishing those of the second example, and the newly mentioned components are given new numerical designations. Further, to distinguish between the three different versions, in the version of  FIG. 4 , a suffix of “b- 1 ” will distinguish those of the version of  FIG. 4 , a suffix of “b- 2 ” will distinguish those of the second version of  4 A, and the suffix of “b- 3 ” will distinguish those of the third version of  FIG. 4B . 
     All three of these versions of the second example have the following components, the blades  28   b , the hub  30   b , the low speed shaft  32   b , the speed changing section  20   b , the generator section  22   b , and the auxiliary drive section  24   b . In  FIG. 4 , all of these components are arranged in substantially the same way as corresponding components in  FIG. 3 , except that there are two auxiliary drive sections  24   b - 1  and  25   b - 1 . Other specific features are the same, such as having the torque converter and overrunning clutches located in substantially the same manner as in the first example of  FIG. 3 . 
     The first version of the second example of  FIG. 4  differs from the first example in that in addition to the auxiliary drive  24   b - 1  there is a second auxiliary drive  25   b - 1  which connects to the speed changing drive section  20   b - 1 . Power from the auxiliary drive  25   b - 1  is transmitted through the speed changing drive section  20   b - 1  to the generator  22   b - 1  for additional power output. In  FIG. 4  an overrunning clutch  27   b - 1  must be installed to de-couple the wind turbine shaft  32   b - 1  from the speed changing drive  20   b - 1  when there is insufficient wind to rotate wind turbine shaft  32   b - 1 . 
     In  FIG. 4A  the second version of  FIG. 4 , we have the same components of the wind turbine blades  28   b - 2 , the hub  30   b - 2 , the low speed shaft  32   b - 2 , the speed changing section  20   b - 2 , the generator section  22   b - 2 , and the auxiliary power section  24   b - 2 .  FIG. 4A  differs from  FIG. 4  in that there is provided a second speed changing section  26   b - 2  which has an operative connection to the auxiliary drive section  24   b - 2 . Then there is a second auxiliary drive section  25   b - 2  which also has an operative connection through the second speed changing section  26   b - 2 . The second auxiliary drive section  25   b - 2  provides additional power to generator  22   b - 2  as available from energy recovery systems or energy generation systems other than wind, which are part of the hybrid wind turbine system. 
       FIG. 4B  has substantially the same components as in  FIG. 4A , except that in addition to the auxiliary drive section  24   b - 3  transmitting power through the second speed changing section  26   b - 3 , the second auxiliary drive section  25   b - 3  is located on the same side of the second speed changing section  26   b - 3 . In other respects, it functions the same way as the second version of  FIG. 4A . 
     G. Third Example 
     A third example of the present invention will now be described with reference to  FIGS. 5 and 5A . Components of this third example which are the same as, or similar to, components of the earlier examples will be given like numerical designations, with a “c” suffix distinguishing those of the third example. 
     In this third example, the basic system as shown in  FIG. 3  is used, so that the main components and their functions of this third example are substantially the same as in the third example as they are in the first example. However, the added feature is that the auxiliary engine drive is combined with two stages of an organic rankine cycle heat recovery system to increase the overall efficiency of the engine drive. 
     In this example the two stages of heat recovery  50   c  and  51   c  are located in the wind turbine support tower  11   c.    
     With this system, the heat recovery process captures waste heat from the auxiliary engine  24   c  exhaust and the auxiliary engine  24   c  coolant. Also, the waste heat is converted into useful electricity using a separate turbine and generator which is part of the heat recovery system located in the tower  11   c.    
     In  FIG. 5A  the hot exhaust from auxiliary drive engine  24   c  flows to an organic rankine cycle boiler  52   c  to vaporize the organic working fluid. The cooled exhaust then flows to an emission control unit  53   c  before being discharged to atmosphere. The rankine cycle involves a boiler feed pump  54   c  which pumps the organic working fluid to the boiler  52   c  for vaporization. The vapor then flows to the expansion turbine  55   c  which is coupled to a generator  56   c . Power from the generator  56   c  is connected to the wind turbine electrical switchgear. The vapor then flows out of the expansion turbine to the air cooled condenser  57   c  where it is condensed back into a liquid. The liquid working fluid then flows back to the boiler feed pump  54   c  for recirculation. 
     In this example the auxiliary drive engine coolant is routed from auxiliary drive engine  24   c  to an organic rankine cycle boiler  58   c  to vaporize the organic working fluid. The cooled engine coolant is then pumped back to engine  24   c  using coolant circulation pump  59   c . The rankine cycle involves a boiler feed pump  60   c  which pumps the organic working fluid to the boiler  58   c  for vaporization. The vapor then flows to the expansion turbine  61   c  which is coupled to a generator  62   c . Power from the generator  62   c  is connected to the wind turbine electrical switchgear. The vapor then flows out of the expansion turbine  61   c  to the air cooled condenser  63   c  where it is condensed back into a liquid. The liquid working fluid then flows back to the boiler feed pump  60   c  for recirculation. 
     With the conversion of waste energy into additional electricity, the auxiliary drive  24   c  is a very efficient source of additional power for the hybrid wind turbine. 
     H. Fourth Example 
       FIG. 6  shows a fourth example of the present invention. Components of this fourth example which are the same as, or similar to, components of the earlier example will be given like numerical designations, with a “d” suffix distinguishing those of the fourth example. This fourth example has the same basic operating components as shown in the first example, except that in this to fourth example, the auxiliary drive section  24   d  is steam powered. Further, the steam that is generated to supply the power is generated by a boiler that is located in the support tower  11   d . The fuel can be solid fuel, liquid fuel, gaseous fuel, or other fuels. 
     As shown in  FIG. 6 , there is the support structure  13   d  mounted to the tower  11   d , the blade section  18   d , a speed changing drive section  20   d , and a generator  22   d . There are also the two overrunning drive members  68   d  and  69   d  on opposite sides of the generator  22   d.    
     There is a solids fuel hopper  90 , which directs the solid fuel  92  into a furnace area  94 , where there is a forced draft generated by the fan  96 . Further, there is a liquid and/or natural gas burner  98 , a steam drum  100 , a mud drum  102 , a boiler flue gas discharge  104 , and a bag house  106 . There is a steam conduit  108  leading to a steam drive turbine  110 . The steam drive turbine  110  is positioned to supply power to the generator  22   d . The steam exhaust from the steam turbine  110  flows along a conduit  112  to an air cooled surface condenser  114  and is cooled by a fan  116 . The condensate then flows to the feed water pump  105  and back to the boiler steam drum  100 . 
     I. Fifth Example 
     A fifth example of the present invention will now be described with reference to  FIG. 7 . Components of this fifth example which are the same as, or similar to, components of any of the earlier examples will be given like numerical designations, with an “e” suffix distinguishing those of this fifth example. 
     In this fifth example, there is a solar thermal power source in addition to the wind turbine power and also the auxiliary power section. In this case, there would be three sources of power to drive the generator, namely: i) wind; ii) solar generated power; and iii) the auxiliary drive section which, as indicated previously in this text, could be fueled by a wide variety of energy sources, such as an engine driven by diesel fuel, natural gas, ethanol, etc. 
     The wind and solar energy inputs would produce non-firm energy that cannot be depended upon as a constant source of power. However, the auxiliary drive  24   e  (engine or turbine) would be the ultimate backup for firm power generation. Thus, with these three options offered with the wind turbine, the customer could purchase a basic wind turbine, a wind turbine with a solar thermal energy drive, a wind turbine with an engine or turbine (steam, gas turbine, etc.) auxiliary drive, or a wind turbine with both a solar thermal energy drive and an engine or turbine drive. Thus, different sources of energy input to the wind turbine are not mutually exclusive and can cooperate to maximize the output of the wind turbine. With that background information having been given,  FIG. 7  shows the basic components that are shown in the first example of  FIG. 3 , and the components discussed above with reference to  FIG. 7 . 
     Thus, there is the source of firm power in the form of an auxiliary drive engine  24   e  or other power source (see  FIG. 7A ). 
     In this example, in  FIG. 7  there is the tower  11   e  which supports the rotatably mounted support structure  13   e , the speed changing drive section  20   e , and the generator  22   e .  FIG. 7  shows the engine auxiliary drive  24   e - 1  and the auxiliary drive  25   e - 1  in the form of a steam turbine. There is a condenser  152  which directs the condensate to the boiler feed pump  134 . 
     To provide the solar energy,  FIG. 7  shows there is a plurality of heliostats  130  which reflect the sun rays in a converging pattern to a solar absorber  132  that is mounted in the tower  11   e .  FIG. 7  shows there is a boiler feed pump  134  which pumps water or other liquid up through the solar absorber  132  to a steam drum  136  so that the steam can be separated from the steam and water mixture generated in the solar absorber  132 . The steam or other gaseous drive medium then travels upwardly to a steam turbine  25   e - 1 . The steam turbine auxiliary drive  25   e - 1  provides a rotary power output to is the generator  22   e - 1  in combination with the engine auxiliary drive power output  24   e - 1 , or through another operative connection to the generator  22   e - 1 . 
     In operation, either or both of the non firm power sources (i.e., the wind power source and the solar power source) are utilized to provide the energy output to rotate the generator  22   e - 1 . In the event that either or both of the wind power and solar power are absent because of the surrounding weather environment, and are producing no usable power, or only a smaller output of power, then the auxiliary power source  24   e - 1  can be used to supplement the power input to an adequate level. However, if the solar power source and/or the wind power source are adequate, then the auxiliary power section  24   e - 1  will not be required. 
     J. Sixth Example 
     A sixth example of the present invention will now be described with reference to  FIG. 8 . Components of this sixth example which are the same as, or similar to, components of any of the earlier examples will be given like numerical designations with an “f” suffix distinguishing those of this sixth example. 
     In this sixth example, there is an addition of a steam rankine cycle heat recovery system to recover heat from the engine auxiliary drive exhaust. To describe this sixth example, reference is made to  FIG. 8 . 
     Hot engine exhaust leaving the auxiliary drive exhaust flows to a heat recovery steam generator  144   f  where the heat in the exhaust generates steam. The cooled exhaust then flows to the emission control unit  146   f  for treatment before it is discharged to atmosphere. 
     A boiler feed water pump  148   f  pumps water to the heat recovery steam generator  144   f  to raise steam. The steam and water mixture flows to a steam drum  149   f , which is part of the heat recovery steam generator  144   f , to allow the steam to separate from the mixture and flow to a steam turbine auxiliary drive  25   f . This steam turbine  25   f  converts the steam energy into mechanical work by turning the turbine wheel and driving the auxiliary speed changing drive section  26   f  and the generator  22   f  through overrunning clutches  68   f  and  69   f.    
     After giving up a portion of its energy to the steam turbine  25   f , the steam flows to an air cooled condenser  152   f  where it is condensed back into water. The steam condensate then flows through a vacuum deaerator  154   f  for oxygen removal before flowing to the boiler feed water pump  148   f  which pumps the feed water back to the heat recovery steam generator  144   f  to generate more steam. 
     The addition of the heat recovery system to the engine auxiliary drive increases the overall thermal efficiency of the engine auxiliary drive. Several types of steam drivers can be used to drive the generator. An example of an alternate type of steam drive would be a rotary screw steam drive machine. 
     K. Seventh Example 
     A seventh example of the present invention will now be described with reference to  FIG. 9 . Components of this seventh example which are the same as, or similar to, components of earlier examples will be given like numerical designations, with a “g” suffix distinguishing those of this seventh example. 
     This seventh example comprises a solar thermal energy system which combines the benefits of wind power with solar power using the same turbine structure. 
     In this example, the entire solar thermal energy system is separated from the wind turbine power generation system. The solar thermal system uses an organic ranking cycle heat recovery system to convert solar energy into electricity.  FIG. 9  shows the process flow for the solar thermal system. The system components can be located in the support tower or the nacelle substructure of the ninth example. 
     As shown in  FIG. 9  there is a solar energy input to a solar absorber  190   g  which provides heat to a high temperature heat transfer fluid which is pumped through the absorber  190   g  using circulating pump  189   g . The heat transfer fluid then passes through a heat exchanger  192   g  where it vaporizes the organic rankine cycle working fluid. The cooled heat transfer fluid then flows back to the circulation pump  189   g  where it is pumped back to the solar absorber  190   g . The vaporized organic fluid flows out of the heat exchanger  192   g  and into the expander turbine  193   g . The expander turbine  193   g  is coupled to a generator  194   g  which produces electric power. The vaporized working fluid, usually propane or butane, passes through the expander turbine to a condenser  195   g  where it is condensed back to a liquid. The liquid then flows to a pump  196   g  which pumps the working fluid back to the exchanger  192   g  for conversion back into a vapor. An expansion tank  197   g  is provided to allow for the expansion of the heat transfer fluid in the solar thermal system. 
     In addition to the cost savings of combining the wind and solar energy to systems in one structure, the solar addition to the wind turbine has the added benefit of providing additional power output during the daylight hours when it is needed most. 
     L. Eighth Example 
     An eighth example of the present invention will now be described with reference to  FIG. 10 . Components of this eighth example which are the same as, or similar to, components of earlier examples will be given like numerical designations, with an “h” suffix distinguishing those of this eighth example. 
     This eighth example comprises a solar thermal energy system and an engine system with heat recovery which combines the benefits of wind power, solar power, and engine power using the same wind turbine support structure. 
       FIG. 10  shows the process flow for the combined solar thermal system and engine system with heat recovery. In the engine plus heat recovery system, hot engine exhaust leaving the engine  24   h  flows to a heat recovery steam generator  144   h  where the heat in the exhaust generates steam. The cooled exhaust then flows to the emission control unit  146   h  for treatment before it is discharged to the atmosphere. A boiler feed water pump  148   h  pumps water to the heat recovery steam generator  144   h  to raise steam. The steam and water mixture flows to a steam drum  149   h , which is part of the heat recovery steam generator  144   h , to allow the steam to separate from the mixture and flow to the steam turbine auxiliary drive  25   h . The steam turbine  25   h  converts the steam energy into mechanical work by turning the turbine wheel and driving the gear  26   h  and generator  22   h  through overrunning clutches. After giving up a portion of its energy to the steam turbine  25   h , the steam flows to an air cooled condenser  152   h  where it is condensed back into water. The steam condensate then flows through a vacuum de-aerator  154   h  for oxygen removal before flowing to the boiler feed water pump  148   h  which pumps the feed water back to the heat recovery steam generator  144   h  to generate more steam. 
     In the solar thermal system, the solar energy input to a solar absorber  132   h  is converted into steam which drives a steam turbine  25   h  which is coupled to the wind turbine main generator  22   h . The steam then exits the steam turbine  25   h  and flows to an air cooled condenser  152   h  where the steam is condensed back into water. The water then flows through a vacuum deaerator  154   h  to remove oxygen and then to the feed water circulating pump  148   h  where it is pumped back to the solar absorber to generate more steam. 
     M. Ninth Example 
     This ninth example of the present invention will now be described with reference to  FIG. 11 . Some of the components in this ninth example which are substantially the same as, or similar to, corresponding components of earlier examples will be given like numerical designations, with an “i” distinguishing those of this ninth example. Accordingly, there are the propeller blades  28   i  along with the hub  30   i . There is also the speed changing power section  20   i , the generator  22   i , and auxiliary speed changing section  26   i , an auxiliary drive section  24   i , and a second auxiliary drive power  25   i , which in this instance is in the form of a steam driven turbine. 
     This ninth example differs from the earlier examples in that the support structure (i.e., the nacelle  13   i ) has a nacelle substructure  141   i  to provide additional working areas for various purposes, such as to house heat recovery equipment associated with, for example, an auxiliary steam turbine drive. 
     The existing technology utilizes space in the wind turbine support tower and nacelle to house all equipment necessary to operate a wind turbine. At times it can be a challenge to install all equipment in the allowable space in a cost efficient manner and there is very little room for any extra equipment. Because the nacelle rotates to keep the wind turbine blades facing the wind, any equipment located in the support tower which must cooperate with equipment in the nacelle must address the problem of rotation. This means the design must incorporate flexible joints, cables, hoses and other interconnections that allow the necessary rotation. By installing a nacelle substructure below the nacelle and on the downwind side of the support tower, it is possible to provide a large amount of space to mount equipment which rotates with the nacelle. Thus, the problem of interfacing equipment that does not rotate with equipment that does rotate is eliminated. 
     Another advantage of nacelle substructures is that it can be shop fabricated and lifted by crane to attach to the underside of the nacelle. Because the nacelle substructure is designed with a width that is no wider than the support tower, there are no detrimental effects to efficient air flow across the tower which would have a negative impact on the wind turbine output. To the contrary, the shape of the nacelle substructure enclosure will act like a tail behind the tower to assist in yaw control. 
     This ninth example can be advantageous to any of the options described in earlier examples, including a standard wind turbine without any of these options. The substructure could be used with a standard wind turbine to house the electrical gear or other equipment located in the tower to achieve a cost savings during manufacturing. Due to the extremely tall support towers, it is possible to design the height of the substructure such that it extends down the tower as required to house all equipment intended to be located in the tower. 
     Although an auxiliary engine drive  24   i  and steam turbine drive  25   i  are shown coupled to the auxiliary gear  26   i , various other configurations shown in other options are equally suited to cooperate with the nacelle substructure. For example, in  FIG. 11 , there is shown in the upper part of the substructure a heat recovery steam generator or organic rankine cycle heat recovery equipment, generally designated  260   i . Then below this there are air cooled condensers indicated at  262   i . Below the nacelle substructure  141   i  there is a support structure  272   i  which provides support for the substructure, and which could also provide support for at least part of the nacelle  13   i  itself. This support structure  272   i  comprises a pair of circumferential rings  274   i  which are connected to the tower  11   i , and there are roller bearings  268   i  which are rotatably mounted for circular movement on the rings  274   i  around the tower  11   i . Then the support structure  272   i  of the substructure, such as indicated at  278   i , is supported by these bearing rings. 
     The nacelle substructure has the same width as the tower. Thus, the substructure can be extended further down the tower to accommodate additional equipment. There are various options which include the following: i) an engine only configuration in the nacelle; ii)/HRSG/Steam Turbine/Air Cooled Condenser; iii) engine/orc heat recovery/ajr cooled condenser; iv) solar steam generator/steam turbine/air cooled condenser; v) engine/HRSG/solar steam generator/steam turbine/ajr cooled condenser; vi) solar thermal heat absorber (heat transfer fluid)/orc heat recovery/air cooled condenser; vii) engine/solar thermal heat absorber (heat transfer fluid)/orc heat recovery/air cooler. 
     The nacelle substructure  141   i  is attached to the underside of the nacelle such that it rotates with the nacelle. Various pieces of equipment  260   i  can be located within the substructure on various levels. Examples are heat recovery equipment  260   i , air cooled condensers  262   i  and cooling fans  264   i . As indicated above, the structural supports  272   i  for the nacelle substructure are supported by the tower using metal support rings  274   i  enable the nacelle with roll around the support rings  274   i  when the nacelle rotates to face the wind. Solar thermal absorbers  280   i  are located on the support tower itself. 
     Obviously, the vertical dimension of the nacelle substructure could vary substantially. In the representation of the sub-nacelle in  FIG. 1 , its depth dimension (indicated at “b” in  FIG. 11 ), is about 40% of the horizontal length dimension (indicated at “a” in  FIG. 11 ), extending from the forward working end of the nacelle to the rear working end. Obviously, this vertical dimension “b” could be increased or decreased substantially, depending upon various factors. For example, this 40% dimension could be decreased down to about 30%, 20%, 15%, or 10%, or even as low as about 5%. Also, it could be greatly increased to values of, for example, 50%, 75%, 100%, 150%, 200%, 250%, 300%, 400%, 500%, or even possibly higher. 
     The nacelle substructure is an elegantly simple method of providing large amounts of space for equipment which rotates along with the nacelle and thereby eliminating the problem of interfacing rotating and non-rotating equipment. The additional weight will also be a counterweight to the wind turbine blades and will allow them to be located further from the tower, thus, reducing the blade flex when the blades pass by the tower. 
     To summarize at least some of the features of the present invention, the examples of the present invention provide the following advantages: i) the auxiliary drive system will allow a wind turbine to generate firm power rather than non-firm energy; ii) the hybrid wind turbine which incorporates the solar thermal heat recovery system into the wind turbine allows the same generator, switchgear, support tower, real estate, and transmission lines to be used by both the wind turbine and solar thermal power generator; iii) the nacelle sub-structure provides additional space to install equipment that must move with the equipment in the nacelle such as heat recovery steam generators, air coolers, organic rankine cycle heat recovery systems and electrical gear; iv) the nacelle sub-structure enclosure will act as a tail fin on the wind turbine to assist with yaw control; v) the nacelle sub-structure module can be constructed in a shop with ideal working conditions thus improving worker productivity and reducing construction costs; vi) the equipment located in the nacelle sub-structure can be installed in an upright position and remain in an upright position throughout the construction process (equipment located in the support tower must be turned on its side at some point during the shop fabrication, shipment, or construction process); vii) the energy conversion efficiency in BTU/KWH of the hybrid wind turbine which uses wind, and/or solar and/or thermal energy inputs in one combined system is very efficient when compared with the heat rate in BTU/KWH of a thermal energy conversion system alone due to the non-thermal energy inputs from the wind and solar systems; viii) all components of the hybrid wind turbine can be procured and constructed using commercially available equipment and commercially available engineering and construction practices; and ix) the nacelle sub-structure provides an alternate escape route for operations personnel in the event of a fire in the nacelle. 
     N. Tenth Example 
     Referring now to  FIG. 12 , depicted therein is yet another example of a hybrid wind turbine system  320  of the present invention. The example hybrid wind turbine system  320  comprises a tower structure  322  capable of supporting the system  320  in a desired orientation. The tower structure  322  in turn supports a nacelle  324  and blades  326 . As is conventional, the example nacelle  324  is mounted on the tower structure  322  such that the nacelle  324  may rotate to optimize the orientation of the blades  326  with respect to the wind at any point in time.  FIG. 12  further shows that electrical switch gear  328  may be mounted within the nacelle  324 . 
     The blades  326  are mounted on a hub  330  that is rotatably supported by the nacelle  324 . In particular, the hub  330  may be conventionally is supported by a generator shaft  332  of a generator  334 . Accordingly, air movement rotates the blades  326  to cause the generator  334  to generate electricity. 
     In the example system  320 , the generator shaft  332  is in turn connected to a gearbox  336  through a first overrunning clutch  338 . The gearbox  336  is connected to a variable speed drive  340  through a second overrunning clutch  342 . The variable speed drive  340  is connected to an auxiliary drive engine  344  through a coupling  346 . The auxiliary drive engine  344  is connected to a fuel line  348  connected to a conventional fuel source (not shown) such as fuel storage tanks or utility fuel lines. The fuel line  348  depicted in  FIG. 12  represents both a conduit for carrying fuel and the fuel carried by the conduit. 
     Accordingly, when desired, the auxiliary drive engine  344  may be operated to rotate the generator shaft  332  through the coupling  346 , variable speed drive  340 , second overrunning clutch  342 , gearbox  336 , and first overrunning clutch  338 . Operation of the auxiliary drive engine  344  thus causes the generator  334  to generate electricity. 
     As with others of the example systems described above, the auxiliary drive engine  344  of the example system  320  is located in the top portion  350  of the system  320 . In the example system  320 , the top portion  350  containing the auxiliary drive engine  344  is located below the nacelle  324  within an upper end of the tower structure  322 . 
     An exhaust line  352  connects the auxiliary drive engine  344  to a heat to recovery system  354  located at a lower portion  356  of the system  320 . Again, the exhaust line  352  depicted in  FIG. 12  represents both engine exhaust and the conduit for carrying that exhaust. The example heat recovery system  354  is depicted within a lower end of the tower structure  322 , but this system  354  may be located at least partly outside of the tower structure  322 . The heat recovery system  354  may be implemented using any suitable system for reclaiming or generating energy from heat. 
     The example configuration depicted in  FIG. 12  thus allows the auxiliary drive engine  344  to be mounted in a nonmovable section of the wind turbine system  320 , in this case the tower structure  322 . Mounting the auxiliary drive engine  344  within a nonmovable portion of the wind turbine system  320  allows exhaust from the engine  344  to be ducted down the tower structure  322  to heat recovery equipment located in the tower, or at the base of the tower, rather than to a substructure attached to the rotating nacelle  324 . 
     O. Eleventh Example 
     Referring now to  FIG. 13 , depicted therein is yet another example of a hybrid wind turbine system  420  of the present invention. The example hybrid wind turbine system  420  comprises a tower structure  422  capable of supporting the system  420  in a desired orientation. The tower structure  422  in turn supports a nacelle  424  and blades  426 . As is conventional, the example nacelle  424  is mounted on the tower structure  422  such that the nacelle  424  may rotate to optimize the orientation of the blades  426  with respect to the wind at any point in time.  FIG. 13  further shows that electrical switch gear  428  may be mounted within the nacelle  424 . 
     The blades  426  are mounted on a hub  430  that is rotatably supported by the nacelle  424 . In particular, the hub  430  may be conventionally supported by a generator shaft  432  of a generator  434 . Accordingly, air movement rotates the blades  426  to cause the generator  434  to generate electricity. 
     In the example system  420 , the generator shaft  432  is in turn connected to a gearbox  436 . In this example system  420 , the blades  426  are located on an opposite end of the nacelle  424  from the generator  434 , and the gearbox  436  is arranged between the blades  426  and the generator  434 . An overrunning clutch  438  may be connected between the hub  430  and the gear box  436 . 
     The gearbox  436  is connected to a fluid drive reduction gear  440  through an overrunning clutch  442 . The fluid drive reduction gear  440  is connected to an auxiliary drive engine  444  through a coupling  446 . The auxiliary drive engine  444  is connected to a fuel line  448  connected to a conventional fuel source (not shown) such as fuel storage tanks or utility fuel lines. The fuel line  448  depicted in  FIG. 13  represents both a conduit for carrying fuel and the fuel carried by the conduit. 
     Accordingly, when desired, the auxiliary drive engine  444  may be operated to rotate the generator shaft  432  through the coupling  446 , fluid drive reduction gear  440 , overrunning clutch  442 , and gearbox  436 . Operation of the auxiliary drive engine  444  thus causes the generator  434  to generate electricity. 
     As with others of the example systems described above, the auxiliary drive engine  444  of the example system  420  is located in the top portion  450  of the system  420 . In the example system  420 , the top portion  450  containing the auxiliary drive engine  444  is located below the nacelle  424  within an upper end of the tower structure  422 . 
     An exhaust line  452  connects the auxiliary drive engine  444  to a heat recovery system  454  located at a lower portion  456  of the system  420 . Again, the exhaust line  452  depicted in  FIG. 13  represents both engine exhaust and the conduit for carrying that exhaust. The example heat recovery system  454  is depicted within a lower end of the tower structure  422 , but this system  454  may be located at least partly outside of the tower structure  422 . The heat recovery system  454  may be implemented using any suitable system for reclaiming or generating energy from heat. 
       FIG. 13  thus illustrates another embodiment of a hybrid wind turbine of the present invention in which the auxiliary drive engine located in the top portion of the wind turbine tower below the nacelle. In this example, the generator  434  is a slow speed multi-pole generator. As with the example discussed in connection with  FIG. 12 , the auxiliary drive engine  444  is located in the non-movable section of the wind turbine, which allows the engine exhaust  452  to be ducted down through the tower structure  422  to heat recovery equipment  454  located in the tower structure  422 , or at the base of the tower structure  422 , rather than to a substructure which is attached to or located within the rotating nacelle  424 . 
     Accordingly, in the example system shown in  FIG. 13 , the wind imparts energy to the wind turbine blades  426  which cause rotation of the blades  426  and the hub  430 . The blade hub  430  is connected to the generator shaft  432 ; axial rotation of the generator shaft  432  turns the generator  434 . The example generator  434  is a multi-pole type generator, such as a permanent magnet generator, and operates at the rotor speed of the wind turbine blades  426 . In this configuration, a speed reduction gear is not required to allow the generator  434  to be connected to the shaft  432  connected to the hub  430 . The generator can operate at various rotational speeds and produces alternating current which may or may not be at a standard frequency of 50 or 60 cycles per second. To correct for any frequency offset from a desired frequency, the output of the generator is converted to direct current and subsequently rectified back to 50 or 60 cycle AC current. By allowing the generator to operate at various speeds, turbine manufacturers are able to optimize the wind turbine efficiency for various wind speeds. 
     In  FIG. 13 , the coupling  446  and fluid drive reduction gear  440  reduce the rotational speed of the output shaft of the auxiliary drive engine  444 . Additionally, the example engine  444  and the fluid drive reduction gear  440  are fixed in the axial center of the tower and do not rotate with the nacelle  424 . The clutch  442  connects the fluid drive reduction gear  440  to the gearbox  436 ; the example gearbox  436  is a 90 degree speed reduction gearbox. The example gearbox  436  thus reduces the rotational speed of the output shaft of the engine  444  to a speed appropriate for driving the generator  434 . The clutch  442  located between the gearbox  436  and the fluid drive reduction gear  440  allows the engine  444  to be disconnected from the gearbox  436  when the engine  444  is not in use. The engine  444  can operate simultaneously with the wind turbine to provide firm power output or it can operate independently if the wind turbine is idle (e.g., too little wind). 
     Although not shown in  FIG. 13 , the components that connect the fluid drive reduction gear  440  to the gearbox  436  may be a drive shaft with universal joints or an angle drive gear assembly. An angle drive gear assembly attached to gearbox  436  is capable of compensating for the small horizontal offset angle of equipment located in the nacelle  424 . Conventionally, the angular relationship between the wind turbine equipment mounted in the nacelle and the wind turbine tower is not perpendicular. When the blades are driven by wind, this non-perpendicular relationship allows the blades to maintain a greater distance from the tower when they pass by the tower during operation, which reduces the flexing of the blades and, thus, reduces the probability of blade fatigue failure. 
     P. Twelfth Example 
     Referring now to  FIGS. 14-17 , depicted therein is a twelfth example hybrid wind turbine system  520  of the present invention. The example hybrid wind turbine system  520  comprises a tower structure  522  capable of supporting the system  520  in a desired orientation. The tower structure  522  in turn supports a nacelle  524  and blades  526 . As is conventional, the example nacelle  524  is mounted on the tower structure  522  such that the nacelle  524  may rotate to optimize the orientation of the blades  526  with respect to the wind at any point in time.  FIG. 14  further shows that electrical switch gear  528  may be mounted within the nacelle  524 . 
     The blades  526  are mounted on a hub  530  that is rotatably supported by the nacelle  524 . In particular, the hub  530  may be conventionally supported by a generator shaft  532  of a generator  534 . Accordingly, air movement rotates the blades  526  to cause the generator  534  to generate electricity. 
     In the example system  520 , the generator shaft  532  is in turn connected to a gearbox  536  through a first overrunning clutch  538 . The gearbox  536  is connected to a variable speed drive  540  through a second overrunning clutch  542 . The variable speed drive  540  is connected to an auxiliary drive engine  544  through a coupling  546 . The auxiliary drive engine  544  is connected to a fuel line  548  connected to a conventional fuel source (not shown) such as fuel storage tanks or utility fuel lines. The fuel line  548  depicted in  FIG. 14  represents both a conduit for carrying fuel and the fuel carried by the conduit. 
     Accordingly, when desired, the auxiliary drive engine  544  may be operated to rotate the generator shaft  532  through the coupling  546 , variable speed drive  540 , second overrunning clutch  542 , gearbox  536 , and first overrunning clutch  538 . Operation of the auxiliary drive engine  544  thus causes the generator  534  to generate electricity. 
     As with others of the example systems described above, the auxiliary drive engine  544  of the example system  520  is located in the top portion  550  of the system  520 . In the example system  520 , the top portion  550  containing the auxiliary drive engine  544  is located below the nacelle  524  within an upper end of the tower structure  522 . 
     An exhaust line  552  connects the auxiliary drive engine  544  to a heat recovery system  554  located at a lower portion  556  of the system  520 . Again, the exhaust line  552  depicted in  FIG. 14  represents both engine exhaust and the conduit for carrying that exhaust. The example heat recovery system  554  is depicted within a lower end of the tower structure  522 , but this system  554  may be located at least partly outside of the tower structure  522 . The heat recovery system  554  may be implemented using any suitable system for reclaiming or generating energy from heat. 
     The example configuration depicted in  FIG. 14  thus allows the auxiliary drive engine  544  to be mounted in a nonmovable section of the wind turbine system  520 , in this case the tower structure  522 . Mounting the auxiliary drive engine  544  within a nonmovable portion of the wind turbine system  520  allows exhaust from the engine  544  to be ducted down the tower structure  522  to heat recovery equipment located in the tower, or at the base of the tower, rather than to a substructure attached to the rotating nacelle  524 . 
     As will be explained in further detail below, the example wind turbine system  520  further comprises a solar absorber system  560 . The solar absorber system  560  is secured at a desired elevation relative to the tower structure  522 ; a solar heat line  562  carries heated fluid from the solar absorber system  560  to the heat recovery system  554  as will be described in further detail below. 
     The drawings further illustrate an absorber housing  566  and a layer of heat absorption material  568  on or forming a part of the housing  566 . The heat absorption material  568  has desirable heat transfer properties and typically will be, or be coated with, a color, such as black, that facilitates the absorption of heat. 
       FIG. 14  shows the heat recovery system  554  and the solar absorber system  560  can be configured to recover both solar heat and heat generated by the auxiliary drive engine  544 .  FIGS. 14-16  only show the components of solar absorber system  560  on one side of the wind turbine tower for illustrative purposes. A wind turbine system incorporating a solar absorber system may have a first section facing east and a second section facing west to optimize absorption of solar energy during morning and afternoon. Additionally, one or more heliostats  564  may be arranged to direct solar rays onto the solar absorber system  560 . 
     As is conventional, wind imparts energy to the wind turbine blades  526  which move the blades  526  and blade hub  530 . The blade hub is connected to a shaft  532  which turns the generator  534 . The example generator  534  used in this embodiment is preferably, but not necessarily, capable of operating at a very low speed to obviate the need for a speed reduction gear to allow the generator to be connected to the generator shaft  532 . The example generator  534  is an AC permanent magnet generator that can operate at various rotational speeds and produces alternating current which may or not be at a standard frequency of 50 or 60 cycles per second. To correct for this possible deviation from the desired frequency, the output of the generator  534  is converted to direct current and subsequently rectified back to 50 or 60 cycle AC current. By allowing the generator  534  to operate at various speeds, wind turbine efficiency can be optimized for various wind speeds. 
       FIG. 14  illustrates that the auxiliary engine  544  is connected to the coupling  546 , which is in turn connected to a fluid drive reduction gear  540  to reduce the speed of the drive shaft of the auxiliary drive engine  544 . The example drive engine  544  and the fluid drive reduction gear  540  are fixed in the center of the tower and do not rotate with the nacelle. The coupling  542  connects the fluid drive reduction gear  540  to the speed reduction gearbox  536 . The speed reduction gearbox  536  reduces the output shaft speed of the fluid drive reduction gear  540  to match the speed of the generator  534 . The clutch  538  is located between the speed reduction gearbox  536  and the generator  534  to allow the generator  534  to be disconnected from the speed reduction gearbox  536  when the engine  544  is not in use. However, the engine  544  can operate simultaneously with the wind turbine to provide a firm power output, or the engine  544  can operate independently if the wind turbine is idle. 
     Referring now to  FIGS. 15 and 16 , a solar absorber  610  is mounted within the absorber housing  656 . An example engine exhaust line  612  routes the engine exhaust to an engine exhaust heat exchanger  620  portion of the heat recovery system  660 . The engine exhaust then flows through an emission control device  670  and an engine exhaust shutoff damper  650 . Engine exhaust then flows from the engine exhaust shutoff damper  650  to an annular space  656  between solar absorber tubes  630  and tower wall insulation  638  to transfer more waste heat to the back side of the solar tubes  630 . 
     A combustion air fan  648  draws ambient combustion air through an opening  646  in the tower structure  522  and sends it to the solar absorber burner  640 . The burner  640  combusts gas or liquid fuel  642  with engine exhaust  612 , combustion air, or a mixture of engine exhaust  612  and combustion air. The flue gas from the burner  640  flows upward in the annular space  656  between the absorber tubes  630  and tower wall insulation  638  and transfers heat to the absorber tubes  630 . The combination of solar energy directed onto the outside of the solar absorber tubes  630 , waste heat carried by the exhaust  612 , and heat from combusting the supplemental fuel  642  directed to the inside of the solar absorber tubes  630  allows the solar absorber  610  to supply thermal energy continuously, if desired, during daytime or night time hours. This design feature allows the solar absorber  610  to be classified as a hybrid solar absorber. 
       FIG. 16  further illustrates a heat exchanger inlet  622 , heat exchanger outlet  624 , and burner combustion air duct  644 .  FIG. 15  illustrates optional cooling lines  660 . 
     A heat transfer fluid is pumped through heat transfer fluid inlets  632  in the solar absorber tubes  630  to absorb heat from the solar and thermal energy sources. The hot heat transfer fluid flows out of outlets  634  in tubes  630  forming the solar absorber  610  to an organic rankine cycle heat recovery system turbine/generator or a conventional rankine cycle system turbine/generator to convert the thermal energy into electrical energy. Components of the Rankine cycle other than the solar absorption tubes  630 , engine exhaust heat exchanger  620 , and emission control device  670 , combustion air fan  648 , associated dampers and controls, and burner  640  can be located, if desired, at ground level at the base of the tower structure  522  as described herein. Thermal insulation  638  is applied to the outside of the wind turbine tower structure  522  to prevent overheating due to a mis-directed solar reflector which normally directs the solar rays onto the solar absorber tubes  630 . 
     A tower manway  658  allows access to the solar absorber access duct  656 . The solar absorber access duct also allows access to the fin-fan air coolers  662  which are mounted on the wall of the solar absorber access duct to  656 . The fin-fan air coolers  662  reject waste heat from the rankine cycle heat transfer fluid to condense the fluid from the vapor state to the liquid state. The fin-fan coolers  662  can also be mounted on the ground at the base of the tower structure  522 , if desired. The tower manway  658  also allows access to the solar absorber tubes  630 . A tower manway  664  and platform  666  allow access to the burners  640  for maintenance. 
     Referring now to  FIG. 17 , depicted therein is a process flow diagram illustrating an example energy recovery system that may be used with the heat recovery system of the example wind turbine systems of the present invention. For illustration purposes, the example energy recovery system shown in  FIG. 17  is the heat recovery system  554  of the example wind turbine system  520  described above. 
     The example energy recovery system  554  depicted in  FIG. 17  utilizes an organic rankine cycle heat recovery system. As generally discussed above, a hybrid wind turbine system incorporating this system  554  utilizes wind energy acting on blades  526  to turn a generator  534  to produce electricity, solar energy from the sun to produce electricity using an organic rankine cycle, and an engine  544  to generate supplemental or emergency power using conventional fossil fuels. The hot flue gas from the engine  544  flows through a heat exchanger  720  where it transfers heat to a circulating heat transfer fluid. The flue gas then passes through an emission control device  670  and then to the burner  640  before entering the solar absorber  610  where it passes by and transfers heat to the solar absorber tubes  630 . Additional heat may be added to the engine  544  exhaust flue gas by utilizing the burner  640  to burn additional fuel. The flue gas contains sufficient oxygen to allow combustion of the supplemental fuel  642 . 
     If the engine  544  is not operating, the solar absorber can still receive supplemental heat by operating the combustion air fan  648  to provide oxygen for combustion of the supplemental fuel  642 . If the engine  544  is not operating and it is necessary to operate the combustion air fan, damper  650  is closed and damper  652  is opened to prevent combustion air from flowing through the ductwork backward toward the engine  544 . If the engine  544  is running and it is not necessary or desired to operate the combustion air fan  648 , the damper  652  will be in the closed position and damper  650  will be in the open position. After passing through the solar absorber  612 , the exhaust flue gas  654  is vented to atmosphere. 
     A pump  722  is used to circulate the heat transfer fluid through the solar absorber and engine exhaust heat exchanger  720 . The fluid then flows to the organic rankine cycle boiler  724  where it vaporizes the working fluid. The heat transfer fluid then flows back to the circulating pump  722  to be re-circulated through the system again. 
     A pump  730  is used to pump an organic rankine cycle working fluid such as isopentane to the boiler  724  where it is vaporized. The vapor then flows to the organic rankine cycle turbine  732  where it expands and turns a shaft  734  which is connected to a generator  736  using coupling  738 . The vapor passes through the turbine  732  and flows to an air cooled condenser  740  which condenses the vapor into a liquid. The liquid flows back to the circulating pump  730  where it is pumped back to the boiler  724 . 
     Referring now to  FIG. 18 , depicted therein is a process flow diagram illustrating an example energy recovery system that may be used with the heat energy recovery system of the example wind turbine systems of the present invention. For illustration purposes, the example energy recovery system shown in  FIG. 18  is the heat recovery system  554  of the example wind turbine system  520  described above. 
     The heat recovery system  554  utilizes a steam rankine cycle heat recovery system. As generally discussed above, the system  520  utilizes the wind to turn the generator  534  to produce electricity, solar energy from the sun to produce electricity using an steam rankine cycle and an engine  544  to generate supplemental or emergency power using conventional fossil fuels. The hot flue gas from the engine  544  flows through a heat exchanger  750  where it transfers heat to a circulating heat transfer fluid. The flue gas then passes through an emission control device  670  and then to a burner  640  before entering the solar absorber  612  where it passes by and transfers heat to the solar absorber tubes  630 . 
     Additional heat may be added to the engine  544  exhaust flue gas by utilizing the burner  640  to burn additional fuel  642 . The flue gas contains sufficient oxygen to allow combustion of the supplemental fuel  642 . If the engine  544  is not operating, the solar absorber  610  can still receive supplemental heat by operating the combustion air fan  648  to provide oxygen for combustion of the supplemental fuel  642 . If the engine  544  is not operating and it is necessary to operate the combustion air fan, damper  650  is closed and damper  652  is opened to prevent combustion air from flowing through the ductwork backward toward the engine  544 . If the engine  544  is running and it is not necessary or desired to operate the combustion air fan  648 , the damper  650  will be in the open position and damper  652  will be in the closed position. After passing through the solar absorber  610 , the exhaust flue gas  654  is vented to atmosphere. 
     The steam rankine cycle in  FIG. 18  utilizes a feedwater pump  752  to pump feedwater to a convection section  754  of the solar absorber  610  and to the engine exhaust boiler  750 . The feedwater that flows to the convection section  754  of the solar absorber  612  picks up heat from the engine exhaust flue gas  654  before this gas exits the convection section  754 . The feedwater then flows through the solar absorber tubes  630  where it is converted into steam and then flows to a steam drum  770  for separation into steam and to water. The steam flows out of the steam drum  770  to the steam turbine  760  where it turns the turbine rotor and drives the generator  764  through coupling  766  to generate electricity. Low pressure steam exits the steam turbine  760  and flows to a surface condenser  768  where it is condensed back to water and then flows to the feedwater pump  752  for recirculation. Water that is separated out in the steam drum  770  flows to a de-aerator  772  and back to the boiler feedwater pump  752 . 
     Feedwater that is pumped to the engine exhaust boiler  750  is converted into steam and then flows to a steam drum  756  for separation into steam and water. The steam flows out of the steam drum  756  to the steam turbine  760  where it turns the turbine rotor and drives the generator  764  through coupling  766  to generate electricity. Low pressure steam exits the steam turbine  760  and flows to a surface condenser  768  where it is condensed back to water and then flows to the feedwater pump  752  for recirculation. Water that is separated out in the steam drum  756  flows to a deaerator  758  and back to the boiler feedwater pump  752 . 
     While the present invention is illustrated by description of several examples and while the illustrative examples are described in detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications within the scope of the appended claims will readily appear to those sufficed in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and methods, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of applicants&#39; general concept.