WO2010098813A1

WO2010098813A1 - Wind energy device

Info

Publication number: WO2010098813A1
Application number: PCT/US2010/000328
Authority: WO
Inventors: George Moser; Randy W. Linn; Van Walworth; Craig S. Whitaker
Original assignee: Ener2 Llc
Priority date: 2009-02-28
Filing date: 2010-02-08
Publication date: 2010-09-02

Abstract

A wind turbine is proposed employing multiple horizontal axis rotors mounted on a single tower symmetrically on both sides of the tower. Said rotor units can share appropriate controls, support structures, and optionally some other operating components such as the generator or the gearbox, in order to provide a highly cost-effective turbine system. The control system for the multi-rotor system can control not only the yaw and the pitch, as in conventional single-rotor systems, but also the tilt angle of the rotors, adding a previously not available control parameter that can significantly increase operating efficiency in the presence of winds that are not perfectly horizontal, which is a common occurrence. The resulting system can provide substantially higher energy generation at lower investment costs and lower cost per KW generated.

Description

WIND ENERGY DEVICE

DESCRIPTION CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application No. 61/208,750, filed February 28, 2009, which is hereby incorporated by reference and made a part hereof.

FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT [0002] Not Applicable.

TECHNICAL FIELD

[0003] The subject invention is related to the industry of alternative energy production and more specifically the industry of wind turbines for electricity generation.

BACKGROUND OF THE INVENTION

[0004] Wind turbines are well known mechanical devices used for hundreds of years to perform various mechanical works. The application and use of wind turbines to generate electricity was a natural and obvious application of turbines as soon the need for and availability of electricity uses was developed. Since the initial uses of turbines for generating electric power first appeared, many improvements and efficiencies have been applied to turbine technology.

[0005] Traditional turbines have at least one rotor blade mounted on a hub rotating about a horizontal axis. The turbine unit is usually fixed to the top of a tower structure and is capable of being rotated about the axis of the tower (yaw) in order to align with the direction of the wind. Most modern wind turbines of the current state of the art employ three rotor blades.

[0006] The ever increasing need for energy, combined with environmental concerns for alternative energy systems, provides the catalyst for more development and investment in wind power technology than ever before in the history of wind turbines. [0007] Development trends in wind energy technology include off-shore installations, some of which are floating, while others are setting on the ocean floor. Other wind technologies include installing the turbines into kites, gliders, blimps, and/or other systems operating at altitudes above the earth while being tethered to the ground.

[0008] Wind energy technology is very important because it is environmentally clean and in virtually unlimited supply. Harnessing the wind for power consumption is a multi-billion dollar industry and the trends suggest and represent that a larger portion of the total power produced each year is produced from wind systems than the previous year. It is projected by some that this increasing production rate will last for many years to come. At the present time only a small percent of the total power generated comes from renewable alternative sources such as wind power generating systems.

[0009] Demands for wind generated power have lead to many governments of countries and states to put legislative policies in place regarding renewable power generation such as wind power. There are many countries that want to increase renewable energy generation from 5% of the total power produced to 10%, 20 % or even more. Scotland has announced plans for 50% energy from wind. The USA is considering a 20% minimum energy production from alternative energy. As a result, there is massive demand worldwide for wind turbines. Turbine manufacturers cannot meet the demand for turbine units. Many new turbine unit orders are booked years in advance and/or backlogged.

[0010] One possible solution to meet the demand would be to design and manufacture a wind turbine that can provide more power than current turbines, which usually reach only about 3 to 5 MW capacity. This invention makes that possible.

[0011] Another issue is the still relatively high cost of electricity generated from wind. There is increasing global pressure to reduce the cost of power and reach grid parity (match the cost of fossil fuel based energy). Alternative energy remains more expensive to produce than fossil fuel based systems. The present invention makes a major contribution in that area too.

[0012] Finally, another important issue regarding wind energy is the fact that many areas of the world are effectively running out of space for turbine installations. This is especially true in many European countries, with the best wind locations already taken. There is a real and present need to replace many existing aging turbines with new machines that can provide more power, and that can provide that power more efficiently than previous installations. With installation space at a premium and the high cost of leasing or buying space for turbines, a more space-effective solution is needed. The present invention makes a major contribution in that regard.

SUMMARY OF THE INVENTION

[0013] In order to get more power and reduce cost per KW, the wind industry has been trying to grow the size of rotors. It is well known that the amount of power generating capability increases with rotor diameter. Therefore, turbine technology and manufacturing companies continue to push the limits of rotor diameter. Turbine units have been manufactured with rotor diameters over 120 meters. However, many problems are also introduced as rotor diameter increases.

[0014] One problem is that the forces acting on the blades become overwhelming. These stresses can cause premature rotor failure and/or place enormous demands of the materials used in construction of the rotors. The engineering challenges that must be overcome increase exponentially with rotor size also, and the solutions lead to very high costs.

[0015] Another problem with increasingly larger rotors is that the large rotor size, towers, and the nacelle become so large that the cost of transportation becomes extremely high.

[0016] Yet another problem is that the exceptionally large rotor blades are becoming prohibitively expensive to manufacture. Many manufacturers are faced with the need to build super-sized manufacturing facilities just to manufacture the super-sized equipment. The subject invention addresses this problem by utilizing smaller diameter equipment which is more cost effective to manufacture.

[0017] Yet another problem with larger rotor diameters is that the cut-in wind speed becomes significantly increased. Therefore, the force required to initiate rotation of the rotors is such that low wind speeds may not be enough to get the turbine unit moving. The subject invention addresses this problem by making it possible to utilize smaller diameter turbine units in areas with lower wind speed, which require less wind speed to start rotation. [0018] Still another problem with large wind turbines is the poor eye appeal or detraction to natural landscapes that wind farms impose. There is growing favor from public opinion to promote wind turbines, however, most people that favor them do not favor them being installed near them. The subject invention also addresses the eye appeal issue of wind turbines by providing some inherent design opportunities to artistically enhance the design and appearance of the turbine unit which are not available with the current state of the art turbines.

[0019] Further growth in rotor diameters is very problematic, and yet more efficient power generation technology is needed. Increased rotor size alone is not the solution. Rotor size does matter, but it must be in balance with how the rotor is utilized.

[0020] The subject invention addresses this problem by allowing efficient use of multiple rotors in each turbine unit to generate a multiple of the energy production of a single larger turbine unit. The multi-turbine unit of the subject invention at least doubles the power of the turbine installation without doubling the cost and without any increase in space requirements.

[0021] The subject invention proposes at least two or three turbines (or possibly more) arranged on the same tower structure. In one preferred embodiment, the turbine units can be operated independently of each other, or in another environment, they can share the use of some subsystems or components.

[0022] Another key innovative feature of this invention is the ability to tilt the rotors when the wind is not perfectly horizontal. Modern wind turbines are conventionally equipped with a yaw mechanism that allows the nacelle to turn around a vertical axis in order to orient themselves advantageously against the wind. However, they have no way to adjust their position around a horizontal axis, which is what is required for best orientation with respect to an ascending or descending wind, which is a common occurrence. Current turbines lack adjustability to this key parameter - in other words, a key needed knob is missing to adjust to this additional degree of freedom of the wind. As a result, current wind turbines operate under suboptimal conditions in ascending or descending winds.

[0023] The reason modern turbines lack a tilting mechanism is because the tilting movement in a conventional turbine would cause the rotor blades to clash with the tower mast when tilted down to adjust the turbine to ascending winds. The subject invention provides a mechanism where this problem is eliminated and a tilting mechanism can be used without any danger of such a clash, leading to a substantial increase in operating efficiency.

[0024] Other advantages and features of the subject invention will be apparent to those skilled in the art.

[0025] One advantage of the subject invention is the cost reduction from sharing some subsystems, such as the same yawing system, the same tower (reinforced, therefore not really the same tower, but still more cost-effective than multiple towers), the same space (cost of the leased or bought land is shared), the same transformers, the same connection to the grid, the same maintenance, the same communications equipment such as phone line and diagnosis equipment, and potentially others.

[0026] Another advantage of the subject invention is that the multi-turbine unit provides a system in which each turbine includes its own nacelle and therefore each turbine works independently. This configuration provides a measure of redundancy in case of failure.

[0027] Another advantage of the subject invention is that the multi-turbine unit can provides a combination of two smaller rotors that can produce the same or more electric power than a larger single rotor, but with a lower cut-in wind speed and therefore longer periods of time in operation. The net result is more continuous hours of energy production each year.

[0028] Another advantage of the subject invention is that the multi-turbine unit provides one additional degree of freedom to optimize power generation (angle of rotor relative to tower). This advantage provides a major advantage in power generation. Wind streams are typically not perfectly horizontal, and often are at a substantial degree from a horizontal line. The advantage of the subject invention to tilt upward and downward to better confront the wind stream is a major advantage in efficient use of the turbine. The consequence is better operating efficiency and higher power generation.

[0029] Another advantage of the subject invention is that the multi-turbine unit can provide a combination of two smaller rotors that can be less expensive than a larger single rotor, reducing cost per KW. [0030] Another advantage of the subject invention is that the multi -turbine unit with smaller rotors required can reduce transportation and still generate the same or more electricity than a larger rotor.

[0031] Another advantage of the subject invention is that the multi-turbine unit can have better aerodynamic performance because of a support structure which introduces less air pressure resistance to the sweep of the rotor blades as they pass in proximity to the support structure, eventually resulting in longer blade durability and better turbine longevity.

[0032] Another advantage of the subject invention is that the multi-turbine unit provides a means to dramatically increase total energy capacity production in a wind farm. This advantage is accomplished by taking advantage of the dense population that smaller rotor turbines are permitted in a given area compared to the population density of large rotor turbines in the same geographical wind farm area. The impact of this is more energy at lower cost.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] To understand the present invention, it will now be described by way of example, with reference to the accompanying drawings in which:

[0034] Figure 1 is a front view of a conventional prior art turbine;

[0035] Figure 2 is a side view of the turbine of Figure 1 ;

[0036] Figure 3 is a partial blown up view of the turbine of Figure 1 ;

[0037] Figure 4 is a front view of one embodiment of the invention;

[0038] Figure 5 is a front view of another embodiment of the invention;

[0039] Figure 6 is a front view of another embodiment of the invention;

[0040] Figure 7 is a perspective view of the embodiment of Figure 6;

[0041] Figure 8 is a front view of an embodiment showing one turbine rotation;

[0042] Figure 9 is a front view of an embodiment showing another turbine rotation; [0043] Figure 10 is a front view of another embodiment of the invention;

[0044] Figure 11 is a schematic view of a turbine drive system;

[0045] Figure 12 is a schematic view of another turbine drive system;

[0046] Figure 13 is a schematic view of another turbine drive system;

[0047] Figure 14 is a schematic view of another turbine drive system;

[0048] Figure 15 is a front view of another embodiment of the invention with three turbines;

[0049] Figure 16 is a front view of another embodiment of the invention, such as an offshore embodiment;

[0050] Figure 17 is a front view of another embodiment of the invention;

[0051] Figure 18 is a side view of the embodiment of Figure 17;

[0052] Figure 19 is a top view of the embodiment of Figure 17;

[0053] Figure 20 is a front view of a prior art turbine;

[0054] Figure 21 is a front view of another embodiment of the invention;

[0055] Figure 22 is a front view of another embodiment of the invention;

[0056] Figure 23 is a front view of another embodiment of the invention;

[0057] Figure 24 is a front view of the embodiment of Figure 22;

[0058] Figure 25 is a front view of another embodiment of the invention;

[0059] Figure 26 is a front view of another embodiment of the invention;

[0060] Figure 27 is a front view of another embodiment of the invention;

[0061] Figure 28 is a front view of the embodiment of Figure 26; [0062] Figure 29 is a front view of the embodiment of Figure 27;

[0063] Figure 30 is a side view of an installation of a turbine; and,

[0064] Figure 31 is a side view of an installation of a turbine with the turbine tiled down.

DETAILED DESCRIPTION

[0065] Figure 1 shows a front view of a conventional prior art turbine. Generically, 10 is a schematic representation of the sweep area of the three rotor blades 12, 13 andl4, which are arrayed around hub 16. The nacelle 15 is the machine house, which contains the hub, gearbox, generator, yaw motor, anemometer, mechanical brake, main drive shaft, yaw bearing, controller, wind vane, rotor hub, rotor blade pitch mechanism, and other components, all mounted on tower mast 11.

[0066] Modern turbines work when the rotor blades respond to passing wind streams causing the turbine to rotate. The blades can be rotated around their longitudinal axis using a blade pitch mechanism located in the hub to optimize their angle with respect to the wind.

[0067] The entire nacelle and rotor is turned to face into the wind to further take advantage of wind speed using a yaw mechanism. The yaw mechanism usually includes a system of gears and electric motors (the so called yaw or azimuth motors) which cause the nacelle to rotate around the tower. A controller monitors the wind direction and a host of other parameters and initiates the yaw mechanism as needed to keep the rotor facing into the wind.

[0068] As the rotor blades sweep through the air, they turn a central shaft in the nacelle which is connected to a gear box. The gear box is connected to the generator to produce electric power. A shaft between the generator and the gear box includes a brake mechanism which is used to stop the rotor from turning and/or to slow it down to maintain a certain speed.

[0069] The controller monitors wind speed and wind direction and makes adjustments to the two basic mechanisms it has to control turbine operation: a) the pitch of the blades, and b) the yaw. In the future through this invention there will be a third key mechanism: the tilt mechanism, which is not available today. [0070] Figure 2 shows a side view of the same conventional prior art as shown in Figure 1.

[0071] Figure 3 shows the nacelle 15 or machine house with a schematic representation of its internal components. Rotor blades 14 sweep through the air connected at the root of the blade at the hub 16. The rotational motion turns the slow shaft 84 in the nacelle which is connected to gear box 17. Gear box 17 is connected to generator 18 by fast shaft 85 to produce electric power. Some types of generators, typically called direct-drive generators, eliminate the need for a gea box. In such a case (not shown in this Figure) the slow shaft would connect directly with the direct-drive generator.

[0072] Figure 4 shows a first embodiment of the subject invention. Turbines 21 and 22 are mounted on the same tower 20. Truss 23 is depicted as a bridge type schematic structure, which is a structure that supports both of the turbines, basically a beam, or a system of beams. It can be a lattice or round structure, or rectangular beams, etc. 24 and 25 are the bridge supports, which are also beams, tubes or other brace type structures designed to rigidly support the bridge. Other embodiments of the subject invention are described herein which do not employ brace systems as depicted in Figure 4.

[0073] In this embodiment, the two turbines 21 and 22 are basically independent from each other in their operation. They can rotate at different speeds from each other depending on the wind they are exposed to. Independently operating nacelles 27 and 28 contain all the typical subsystems and components, such as transmission and generator. Variations on the theme provide nacelles 27 and 28 to be direct-drive turbines, with only a generator and no transmission, in which case the nacelles only contain the hub, the slow shaft, the generator and the pitching mechanism for the turbine blades.

[0074] Turbines 21 and 22 are at substantially the same vertical height from the installation surface, so they can both benefit from maximum altitude and wind strength. A symmetrical design with equal hub height and equal distances from the turbine units to the tower is preferred, to avoid imbalances that would be otherwise created due to the wind gradient. If the turbines are mounted at different altitudes the vertical wind gradient would cause an imbalance by exerting different thrust on each side of the tower and therefore applying a net torque around tower 20. The balanced symmetrical concept of this invention avoids imbalances and therefore minimizes cost for tower 20, while simultaneously protecting all subsystems and components from excessive stresses that would result from unbalanced forces.

[0075] Also on Figure 4, tower 20 has two subsections, which are rotateable at joint 26 relative to each other. Joint 26 is equipped with a motorized yawing system with one or more azimuth drives (typically electric motors) which rotate the top subsection of the tower with respect to the bottom subsection to orient the turbine rotors in the optimal direction with respect to the wind.

[0076] Figure 5 shows another embodiment of the subject invention depicting a T- structure with horizontal bridge 23. Those skilled in the art will appreciate that bridge 23 may be heavier in construction than bridge 23 depicted in Figure 4 because of the lack of bridge supports 24. However, this type of turbine support structure offers improved aesthetic appearance against the landscape. This type of structure is also favorable to birds flying near the turbine because there are fewer obstacles to navigate.

[0077] Figure 6 shows another embodiment of the subject invention depicting a V- structure with upward oriented braces 86a and 86b. Those skilled in the art will appreciate that braces 86a may be heavier in construction than bridge 23 depicted in Figure 4 because of the lack of bridge supports similar to 24. However, this type of turbine support structure offers improved aesthetic appearance against the landscape. This type of structure is also favorable to birds flying near the turbine because there are fewer obstacles to navigate.

[0078] Figure 7 is a 3D view of the embodiment shown in Figure 6a.

[0079] Figures 8 and 9 show that in a dual configuration, the turbines can be made to rotate in the same or opposite directions depending on the types of turbine rotors used. Clockwise rotation is the unofficial standard as shown in Figure 8, while Figure 9 depicts one rotor with clockwise rotation and one rotor with counterclockwise rotation. Rotors with the same direction of rotation may be more acceptable in the landscape and people may perceive them as more acceptable, because they are more familiar with them and used to seeing turbines rotate all in the same direction. Counter-rotating rotors may have aerodynamic advantages, because they may focus the air flow on the dual turbines, increasing torque and thereby energy production. [0080] Figure 9 shows an embodiment of the subject invention with 3 rotors mounted on top of tower 20. Those skilled in the art will appreciate this depiction is simply a schematic and that the support and brace system required for this embodiment will obviously include complex structural enhancements not depicted in detail. The rotateable joint 26 and the yawing mechanism have been moved down closer to the ground surface to accommodate the bridge supports.

[0081] Figure 10 is another embodiment of the subject invention depicting two rotors 21 and 22. This embodiment achieves an improvement in cost reduction by sharing subsystems and components. Instead of separate nacelles as in the previous Figures, Figure 9 has a central nacelle 30. The central nacelle 30 allows the sharing of one or more of the components such as the transmission, generator and other subsystems and components.

[0082] Figure 11 shows how some subsystems and components can be shared between the 2 rotors in the embodiment with a central nacelle. 40 and 41 are the rotors, which in this figure are assumed to be rotating in the same direction. The left rotor 40 drives bevel gear 45, which engages with bevel pinion 42, which drives shaft 43. Shaft 43 transmits the power to the central nacelle 44, which contains all the typical subsystems and components, such as a transmission and a generator (or in the case of direct-drive turbines, only a generator and no transmission). In the nacelle 44, the mechanical energy from shaft 43 converted it into electrical energy. The same process happens on the right side of Figure 10. Notice that because of the way the gears are connected with each other, shaft 43 and shaft 46 rotate in opposite directions. That may be desirable or undesirable depending on the type of transmission and generator being used. If the same direction of rotation is desired, the gear arrangement shown in Figure 12 can be used.

[0083] Figurel2 is very similar to Figure 10. The basic difference is that the shafts entering the central nacelle 54 have the same direction of rotation. 50 and 51 are the rotors, which in this figure are assumed to be rotating in the same direction. The left rotor drives bevel gear 55, which engages with bevel pinion 52, which drives shaft 53. Shaft 53 transmits the power to the central nacelle 54, which contains all the typical subsystems and components, such as a transmission and a generator (or in the case of direct-drive turbines, only a generator and no transmission). In the nacelle 54 the mechanical energy from shaft 53 is converted into electrical energy. The same process happens on the right side of Figure 11. Notice that because of the way the gears are connected with each other, now shaft 53 and shaft 56 rotate in the same direction.

[0084] The configurations shown in Figures 11 and 12 can be used with rotors that rotate in the same direction or with rotors that rotate in the opposite direction.

[0085] A potential problem of Figures 11 and 11 is that shafts 43 and 53 are low speed shafts and must carry the full torque generated by their respective wind rotors, which is very high. That makes those shafts very heavy and expensive.

[0086] Figure 13 shows an alternative embodiment of the subject invention. The transmissions 65 and 61 are directly attached to the wind rotor shafts (instead of being located in the central nacelle as in Figures 10 and 11). Therefore the torque is greatly reduced before reaching the shafts 63 and 65. This configuration allows a more cost- effective design of the driveline leading from the wind rotors to the generator in the central nacelle.

[0087] Figure 14 is a similar embodiment to the ones previously shown, but it adds clutches 66 and 67, which allow a lower wind cut-in speed by allowing the wind rotors to start rotating at very low wind speed with the rotors basically disengaged from the load (the transmission and generator). The load is applied only after the rotors have acquired some speed and kinetic energy.

[0088] Figure 15 shows an embodiment with three turbines.

[0089] Figure 16 is another embodiment showing an off-shore version of the turbine of the subject invention. The schematic depiction shows an installation embedded in the ocean floor. Those skilled in the art will easily appreciate that the features and advantages of the subject invention can be incorporated regardless of which particular foundation structure is utilized for the off-shore installation, such as anchored to the ocean or lake ground, floating or other methods. A platform is depicted for access and maintenance. The wavy line represents water level.

[0090] Figures 17, 18 and 19 depict an embodiment of the subject invention with two turbines 27 and 28 mounted on tower 20 shown in a front view, top side view, and top view respectively. Brace supports 25 in Figures 18 and 19 are hidden behind brace supports 24 and out of view in Figure 17. Similarly, brace support 66b shown in Figure 18 is hidden behind brace support 66a shown in Figure 17. These brace supports or similar supporting structures may be required in certain support designs, and are placed so that they pose no additional interference to the wind stream passing through the rotor sweep area.

[0091] Figures 18 and 19 introduce another embodiment schematically shown as support component 82a supporting moveable counter weight 82b. This moveable counter weight feature can be employed to help stabilize the individual turbine to offset the forces imposed upon it by the wind stream. This counter weight system is able to be adjusted by moving the counter weight 82b along support member 82a to establish a more stable turbine.

[0092] Figure 20 depicts a common prior art turbine while Figure 21 depicts an embodiment of the subject invention featuring two turbines. Figure 20 has a relatively large diameter rotor while Figure 21 features two turbines with a relatively smaller rotor diameter. The two rotors in Figure 21 are sized such that they are capable of generating as much or more power than the single large rotor in Figure 20.

[0093] A comparison between Figures 20 and 21 reveals that the new invention in Figure 21 has aerodynamic advantages, because it reduces the obstacles to wind flow located behind the turbine, which cause power losses and create fatigue effects on the blades. Tower 76 has a relatively thick cross section 75 compared to cross sections 70a and 70b. Those skilled in the art will readily appreciate that the relative thickness of the structure required for a relatively large turbine will obviously require more structural thickness than is required for a relatively smaller turbine - other things being equal.

[0094] Figures 20 and 21 also allow some comparative observations to be made between the large turbine and the smaller multiple turbines. Those skilled in the art will readily appreciate that the larger turbine requires a larger manufacturing facility to produce the rotors than is required for the smaller turbines. Similarly, the transportation cost of the larger rotors will naturally be more costly than the smaller rotors. Those skilled in the art will appreciate that the shear mass of the larger rotors will require more force to initiate rotation than smaller rotors, and as a result, the minimum wind speed required to maintain rotation will be greater for the large rotor than for the smaller rotors. [0095] Those skilled in the art will also appreciate that when the large rotor is under maintenance the entire turbine unit does not produce power, however, in the smaller multiple rotor design of the subject invention, one turbine can be halted for maintenance while the other turbine continues power generation. Therefore, the total up-time and total power generated by the smaller multiple rotors is capable of producing more than the equivalent power of the larger rotor. Therefore, the subject invention provides a means of scaling for reduced power generation that is impossible with a single and/or larger turbine.

[0096] Figures 22 and 23 depict an embodiment of the subject invention with multiple rotors compared to a typical prior art rotor of the same relative rotor diameter. The shaded areas 73a and 73b represent the area of air pressure restriction that develops as the rotor blade sweeps past the proximity of the support structures with thickness 70a and 70b respectively. Similarly, shaded area 72 represents the area of air pressure restriction that develops in a typical prior art turbine as the rotor blade passes near proximity to the support structure with thickness 71. It can easily be recognized that the stress effects of 73a and 73b will have less impact on the rotor blades than that of 72 due to the magnitude of the air pressure restriction difference. The greater the air pressure restriction the greater the stress imparted to the rotor blade.

[0097] Figure 24 is the same multiple turbine embodiment shown in Figure 22. Assume that this multiple turbine embodiment has an energy production capacity of "X" kW. The turbine in Figure 23 represents a large rotor turbine. Assume this larger turbine also has an energy production capacity of "X" kW. This is possible because the smaller diameter multiple rotors produce in tandem the equivalent energy capacity of the larger diameter single rotor.

[0098] The air pressure restriction area 77 that is generated by the rotor passing by the near proximity of thickness 75 is significantly more severe than areas 73a and 73b. Once again, it can easily be recognized that the stress effects of 73a and 73b will have significantly less impact on the rotor blades than that of 77 due to the magnitude of the air pressure restriction difference. The greater the air pressure restriction the greater the stress imparted to the rotor blade. This is especially problematic for larger diameter rotors. [0099] Figure 26 represents another embodiment of the subject invention of the multiple turbine system. The multiple turbines 21 and 22 give the designer many options to design the turbine in eye appealing ways not conceivable or possible with traditional turbines. An arc shaped sweep or some kind of semicircular structure 78a or even an irregular shaped structure is possible to incorporate into the design of the multiple turbine embodiments. Those skilled in the art will appreciate the variations on the theme for dynamic and eye appealing esthetic turbine designs which are only limited by one's imagination.

[00100] Figure 27 represents another embodiment in which support structure 78b is predominantly in the shape of a circle or hoop like structure. Once again, it is obvious to those skilled in the art that alternative variations on the theme of esthetic and eye appealing structural turbine designs are possible with the multiple turbine embodiments of the subject invention.

[00101] Figure 28 shows the embodiment of Figure 26 and reveals that the air pressure restriction area that builds up between the rotor blades and the support structure builds gradually as shown by 80 and maxes out with area 79b. This gentle build up of air pressure restriction is much less severe on the rotor blades than traditional turbines. The arc shaped support structure 78 does not have a substantial portion oriented along an axis that is in-line with the radius of the rotor. Traditional turbines have a support structure 76 as shown in Figure 25 which is substantially in-line with the radius of the rotor. Therefore, the stresses built up and imparted to the rotor blades during each pass near the proximity of the support structure of the subject embodiment is significantly less than occurs in traditional turbines with support structures that are substantially in-line with the radius of the rotor.

[00102] Figure 29 shows the embodiment of Figure 27 and reveals that the air pressure restriction area that builds up between the rotor blades and the support structure builds gradually as shown by 80 increases as depicted by 79c and maxes out with area 79b. Once again, this gentle build up of air pressure restriction is much less severe on the rotor blades than traditional turbines. The circular shaped support structure 78 does not have a substantial portion oriented along an axis that is in-line with the radius of the rotor.

[00103] Figure 30 shows a common installation arrangement of a turbine on top of a hill or other topographical elevation. The advantage of such a location is that the wind is accelerated upstream, providing high velocity at the top of the topographical formation. A significant part of that advantage is lost though if the turbine does not confront the wind perpendicularly.

[00104] The main shaft in a typical turbine installation has a fixed angle with respect to the ground such that the axis of the main shaft is substantially parallel to the horizontal plane. Traditional turbines can not tilt downward to confront the wind in a perpendicular orientation because the rotors would come too close to the tower mast that they may actually contact the tower mast and self-destruct. As a result of this design problem, a tilting mechanism is not provided and a lower efficiency is accepted (until now).

[00105] The turbine depicted in Figure 30 is a twin turbine embodiment of the subject invention. The turbine employs a tilting system that allows the multiple turbines to tilt upward and downward so as to confront the wind head on. There is danger of clash with the tower when downward tilting, because there is no tower mast in that area (the turbines are held in place by side supports).

[00106] Figure 31 shows the twin turbine embodiment tilted downward without a clash with the tower. The tilting mechanism can be continuously monitored and controlled similar to methods utilized to control yaw.

Claims

CLAIMSWhat is claimed is:

1. An electrical generation system to generate electricity from wind energy, comprising at least the following subsystems, in functional combination: a tower to provide the necessary altitude for favorable wind velocities; a carrier structure rotatably attached to the tower, substantially near to or at the top of the tower, said carrier structure providing lateral extensions to which at least two nacelles can be attached, symmetrically on each side of the tower; a rotor for each nacelle, rotatable at each nacelle around a generally horizontal rotor axis of rotation and comprising one rotor hub and at least one rotor blade, said blade rotatably attached at or near its root to the rotor hub; a generator and an optional transmission in each nacelle, to raise the rotational speed and then convert the rotational energy into electric energy; a pitching mechanism in each rotor hub or in each nacelle that can rotate the blade about a blade axis of adjustment which is substantially longitudinal to the rotor blade, in order to adjust the blade's angular position relative to the prevailing wind conditions and desired operating conditions; a yawing mechanism that can rotate the top section of the tower, along with the carrier structure and the at least two nacelles and the at least two rotors, around the bottom section of the tower, in order to simultaneously orient the at least two rotors in the desired direction, such as frontally against the wind for maximum power generation or at a different angle in the presence of extreme winds or to park the turbines for maintenance; and, a tilting mechanism that can rotate the rotors and nacelles around the lateral extensions of the carrier structure in order to achieve the desired angle of attack of the wind when the wind direction is not perfectly horizontal, such as upward winds and downward winds, thus providing one more key degree of freedom in the adjustment of the turbines for maximum energy generation, which is a new degree of freedom not previously available.

2. System of claim 1, wherein the number of rotors is an even number and the hubs of the at least two rotors are substantially at the same height relative to the ground, in order to achieve a balanced situation with zero or very small net torque around the tower due to the symmetrical nature of the forces so generated.

3. System of claim 1, wherein the nacelles are fixedly attached to the carrier structure, without the ability to tilt around the lateral extensions of the carrier structure.

4. System of claim 1, wherein the tower includes a first bottom section attached to the ground and a second top section which is rotatably attached to the bottom section of the tower, so that the carrier structure can be fixedly attached to the top section of the tower, with the yaw movement being achieved through the rotation of the top section of the tower with respect to the bottom section of the tower.

5. System of claim 1, wherein the carrier structure is comprised of a truss type frame support cantilevered symmetrically outward on two sides so that two turbines are supported straddle of the tower mast.

6. System of claim 1 , wherein the carrier structure is comprised of a bridge beam type frame support cantilevered symmetrically outward on two sides oriented in the general shape of a "T" relative to the tower mast, with or without additional connecting beams for additional strength, so that two turbines are supported straddle of the tower mast.

7. System of claim 1, wherein the carrier structure is comprised of a pair of beam type frame supports cantilevered symmetrically outward on two sides and oriented in the general shape of a "v" or an inverted "V" relative to the tower mast, with or without connecting beams between the sides of the "V" for additional strength, so that two turbines are supported straddle of the tower mast.

8. System of claim 1, wherein the carrier structure is comprised of an open truss type frame support cantilevered symmetrically outward on two sides so that two turbines are supported straddle of the tower mast, with the structure further including brace and truss support members extending rearward from the rotors so as to provide support against forces exerted by prevailing winds acting upon the turbine.

9. System of claim 1, wherein the at least two rotors share the use of at least one component, such as a common generator, a common transmission and/or other common elements.

10. System of claim 1, wherein an additional central nacelle is located at or near the center of the carrier structure between the lateral rotors.

1 1. System of claim 10 where the central nacelle does not have its own rotor and is just used to support the function of the lateral rotors.

12. System of claim 10 where the central nacelle is equipped with its own rotor and other needed components to operate.

13. System of claim 1, wherein the at least two rotors share at least one component, such as a generator, a transmission and/or other elements in the system through a system of shafts and gears.

14. System of claim 1, wherein the at least two rotors share at least one component, such as a generator, a transmission and/or other elements in the system through a system of belts or cables.

15. System of claim 13, wherein the at least one shared element is located substantially near the bottom of the tower, with a system of shafts and gears transferring power from the top of the tower to the bottom of the tower.

16. System of claim 14, wherein the at least one shared element is located substantially near the bottom of the tower, with a system of belts or cables transferring power from the top of the tower to the bottom of the tower.

17. System of claim 1, wherein the system is an off-shore application with multiple rotor units mounted straddle a tower mast, with said tower mast either resting on, inserted into or embedded in the floor of a body of water such as the ocean or a lake.

18. System of claim 27 wherein the off-shore system is not resting on the floor of a body of water, but instead on a floating body or structure, including a vessel or other structure supported primarily or partially by buoyancy.

19. System of claim 1, wherein multiple rotors are designed to rotate in the same direction.

20. System of claim 1, wherein multiple rotors are designed to rotate in opposite directions.